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1=head1 NAME
2
3perlguts - Perl's Internal Functions
4
5=head1 DESCRIPTION
6
7This document attempts to describe some of the internal functions of the
8Perl executable. It is far from complete and probably contains many errors.
9Please refer any questions or comments to the author below.
10
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11=head1 Variables
12
5f05dabc 13=head2 Datatypes
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14
15Perl has three typedefs that handle Perl's three main data types:
16
17 SV Scalar Value
18 AV Array Value
19 HV Hash Value
20
d1b91892 21Each typedef has specific routines that manipulate the various data types.
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22
23=head2 What is an "IV"?
24
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25Perl uses a special typedef IV which is a simple integer type that is
26guaranteed to be large enough to hold a pointer (as well as an integer).
a0d0e21e 27
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28Perl also uses two special typedefs, I32 and I16, which will always be at
29least 32-bits and 16-bits long, respectively.
a0d0e21e 30
54310121 31=head2 Working with SVs
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32
33An SV can be created and loaded with one command. There are four types of
34values that can be loaded: an integer value (IV), a double (NV), a string,
35(PV), and another scalar (SV).
36
9da1e3b5 37The six routines are:
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38
39 SV* newSViv(IV);
40 SV* newSVnv(double);
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41 SV* newSVpv(const char*, int);
42 SV* newSVpvn(const char*, int);
46fc3d4c 43 SV* newSVpvf(const char*, ...);
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44 SV* newSVsv(SV*);
45
deb3007b 46To change the value of an *already-existing* SV, there are seven routines:
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47
48 void sv_setiv(SV*, IV);
deb3007b 49 void sv_setuv(SV*, UV);
a0d0e21e 50 void sv_setnv(SV*, double);
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51 void sv_setpv(SV*, const char*);
52 void sv_setpvn(SV*, const char*, int)
46fc3d4c 53 void sv_setpvf(SV*, const char*, ...);
9abd00ed 54 void sv_setpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
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55 void sv_setsv(SV*, SV*);
56
57Notice that you can choose to specify the length of the string to be
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58assigned by using C<sv_setpvn>, C<newSVpvn>, or C<newSVpv>, or you may
59allow Perl to calculate the length by using C<sv_setpv> or by specifying
600 as the second argument to C<newSVpv>. Be warned, though, that Perl will
61determine the string's length by using C<strlen>, which depends on the
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62string terminating with a NUL character.
63
64The arguments of C<sv_setpvf> are processed like C<sprintf>, and the
65formatted output becomes the value.
66
67C<sv_setpvfn> is an analogue of C<vsprintf>, but it allows you to specify
68either a pointer to a variable argument list or the address and length of
69an array of SVs. The last argument points to a boolean; on return, if that
70boolean is true, then locale-specific information has been used to format
c2611fb3 71the string, and the string's contents are therefore untrustworthy (see
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72L<perlsec>). This pointer may be NULL if that information is not
73important. Note that this function requires you to specify the length of
74the format.
75
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76The C<sv_set*()> functions are not generic enough to operate on values
77that have "magic". See L<Magic Virtual Tables> later in this document.
a0d0e21e 78
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79All SVs that contain strings should be terminated with a NUL character.
80If it is not NUL-terminated there is a risk of
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81core dumps and corruptions from code which passes the string to C
82functions or system calls which expect a NUL-terminated string.
83Perl's own functions typically add a trailing NUL for this reason.
84Nevertheless, you should be very careful when you pass a string stored
85in an SV to a C function or system call.
86
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87To access the actual value that an SV points to, you can use the macros:
88
89 SvIV(SV*)
90 SvNV(SV*)
91 SvPV(SV*, STRLEN len)
1fa8b10d 92 SvPV_nolen(SV*)
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93
94which will automatically coerce the actual scalar type into an IV, double,
95or string.
96
97In the C<SvPV> macro, the length of the string returned is placed into the
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98variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do
99not care what the length of the data is, use the C<SvPV_nolen> macro.
100Historically the C<SvPV> macro with the global variable C<PL_na> has been
101used in this case. But that can be quite inefficient because C<PL_na> must
102be accessed in thread-local storage in threaded Perl. In any case, remember
103that Perl allows arbitrary strings of data that may both contain NULs and
104might not be terminated by a NUL.
a0d0e21e 105
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106Also remember that C doesn't allow you to safely say C<foo(SvPV(s, len),
107len);>. It might work with your compiler, but it won't work for everyone.
108Break this sort of statement up into separate assignments:
109
110 STRLEN len;
111 char * ptr;
112 ptr = SvPV(len);
113 foo(ptr, len);
114
07fa94a1 115If you want to know if the scalar value is TRUE, you can use:
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116
117 SvTRUE(SV*)
118
119Although Perl will automatically grow strings for you, if you need to force
120Perl to allocate more memory for your SV, you can use the macro
121
122 SvGROW(SV*, STRLEN newlen)
123
124which will determine if more memory needs to be allocated. If so, it will
125call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
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126decrease, the allocated memory of an SV and that it does not automatically
127add a byte for the a trailing NUL (perl's own string functions typically do
8ebc5c01 128C<SvGROW(sv, len + 1)>).
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129
130If you have an SV and want to know what kind of data Perl thinks is stored
131in it, you can use the following macros to check the type of SV you have.
132
133 SvIOK(SV*)
134 SvNOK(SV*)
135 SvPOK(SV*)
136
137You can get and set the current length of the string stored in an SV with
138the following macros:
139
140 SvCUR(SV*)
141 SvCUR_set(SV*, I32 val)
142
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143You can also get a pointer to the end of the string stored in the SV
144with the macro:
145
146 SvEND(SV*)
147
148But note that these last three macros are valid only if C<SvPOK()> is true.
a0d0e21e 149
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150If you want to append something to the end of string stored in an C<SV*>,
151you can use the following functions:
152
08105a92 153 void sv_catpv(SV*, const char*);
e65f3abd 154 void sv_catpvn(SV*, const char*, STRLEN);
46fc3d4c 155 void sv_catpvf(SV*, const char*, ...);
9abd00ed 156 void sv_catpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
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157 void sv_catsv(SV*, SV*);
158
159The first function calculates the length of the string to be appended by
160using C<strlen>. In the second, you specify the length of the string
46fc3d4c 161yourself. The third function processes its arguments like C<sprintf> and
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162appends the formatted output. The fourth function works like C<vsprintf>.
163You can specify the address and length of an array of SVs instead of the
164va_list argument. The fifth function extends the string stored in the first
165SV with the string stored in the second SV. It also forces the second SV
166to be interpreted as a string.
167
168The C<sv_cat*()> functions are not generic enough to operate on values that
169have "magic". See L<Magic Virtual Tables> later in this document.
d1b91892 170
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171If you know the name of a scalar variable, you can get a pointer to its SV
172by using the following:
173
5f05dabc 174 SV* perl_get_sv("package::varname", FALSE);
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175
176This returns NULL if the variable does not exist.
177
d1b91892 178If you want to know if this variable (or any other SV) is actually C<defined>,
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179you can call:
180
181 SvOK(SV*)
182
9cde0e7f 183The scalar C<undef> value is stored in an SV instance called C<PL_sv_undef>. Its
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184address can be used whenever an C<SV*> is needed.
185
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186There are also the two values C<PL_sv_yes> and C<PL_sv_no>, which contain Boolean
187TRUE and FALSE values, respectively. Like C<PL_sv_undef>, their addresses can
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188be used whenever an C<SV*> is needed.
189
9cde0e7f 190Do not be fooled into thinking that C<(SV *) 0> is the same as C<&PL_sv_undef>.
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191Take this code:
192
193 SV* sv = (SV*) 0;
194 if (I-am-to-return-a-real-value) {
195 sv = sv_2mortal(newSViv(42));
196 }
197 sv_setsv(ST(0), sv);
198
199This code tries to return a new SV (which contains the value 42) if it should
04343c6d 200return a real value, or undef otherwise. Instead it has returned a NULL
a0d0e21e 201pointer which, somewhere down the line, will cause a segmentation violation,
9cde0e7f 202bus error, or just weird results. Change the zero to C<&PL_sv_undef> in the first
5f05dabc 203line and all will be well.
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204
205To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
3fe9a6f1 206call is not necessary (see L<Reference Counts and Mortality>).
a0d0e21e 207
d1b91892 208=head2 What's Really Stored in an SV?
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209
210Recall that the usual method of determining the type of scalar you have is
5f05dabc 211to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
d1b91892 212usually these macros will always return TRUE and calling the C<Sv*V>
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213macros will do the appropriate conversion of string to integer/double or
214integer/double to string.
215
216If you I<really> need to know if you have an integer, double, or string
217pointer in an SV, you can use the following three macros instead:
218
219 SvIOKp(SV*)
220 SvNOKp(SV*)
221 SvPOKp(SV*)
222
223These will tell you if you truly have an integer, double, or string pointer
d1b91892 224stored in your SV. The "p" stands for private.
a0d0e21e 225
07fa94a1 226In general, though, it's best to use the C<Sv*V> macros.
a0d0e21e 227
54310121 228=head2 Working with AVs
a0d0e21e 229
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230There are two ways to create and load an AV. The first method creates an
231empty AV:
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232
233 AV* newAV();
234
54310121 235The second method both creates the AV and initially populates it with SVs:
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236
237 AV* av_make(I32 num, SV **ptr);
238
5f05dabc 239The second argument points to an array containing C<num> C<SV*>'s. Once the
54310121 240AV has been created, the SVs can be destroyed, if so desired.
a0d0e21e 241
54310121 242Once the AV has been created, the following operations are possible on AVs:
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243
244 void av_push(AV*, SV*);
245 SV* av_pop(AV*);
246 SV* av_shift(AV*);
247 void av_unshift(AV*, I32 num);
248
249These should be familiar operations, with the exception of C<av_unshift>.
250This routine adds C<num> elements at the front of the array with the C<undef>
251value. You must then use C<av_store> (described below) to assign values
252to these new elements.
253
254Here are some other functions:
255
5f05dabc 256 I32 av_len(AV*);
a0d0e21e 257 SV** av_fetch(AV*, I32 key, I32 lval);
a0d0e21e 258 SV** av_store(AV*, I32 key, SV* val);
a0d0e21e 259
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260The C<av_len> function returns the highest index value in array (just
261like $#array in Perl). If the array is empty, -1 is returned. The
262C<av_fetch> function returns the value at index C<key>, but if C<lval>
263is non-zero, then C<av_fetch> will store an undef value at that index.
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264The C<av_store> function stores the value C<val> at index C<key>, and does
265not increment the reference count of C<val>. Thus the caller is responsible
266for taking care of that, and if C<av_store> returns NULL, the caller will
267have to decrement the reference count to avoid a memory leak. Note that
268C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s as their
269return value.
d1b91892 270
a0d0e21e 271 void av_clear(AV*);
a0d0e21e 272 void av_undef(AV*);
cb1a09d0 273 void av_extend(AV*, I32 key);
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274
275The C<av_clear> function deletes all the elements in the AV* array, but
276does not actually delete the array itself. The C<av_undef> function will
277delete all the elements in the array plus the array itself. The
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278C<av_extend> function extends the array so that it contains at least C<key+1>
279elements. If C<key+1> is less than the currently allocated length of the array,
280then nothing is done.
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281
282If you know the name of an array variable, you can get a pointer to its AV
283by using the following:
284
5f05dabc 285 AV* perl_get_av("package::varname", FALSE);
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286
287This returns NULL if the variable does not exist.
288
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289See L<Understanding the Magic of Tied Hashes and Arrays> for more
290information on how to use the array access functions on tied arrays.
291
54310121 292=head2 Working with HVs
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293
294To create an HV, you use the following routine:
295
296 HV* newHV();
297
54310121 298Once the HV has been created, the following operations are possible on HVs:
a0d0e21e 299
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300 SV** hv_store(HV*, const char* key, U32 klen, SV* val, U32 hash);
301 SV** hv_fetch(HV*, const char* key, U32 klen, I32 lval);
a0d0e21e 302
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303The C<klen> parameter is the length of the key being passed in (Note that
304you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
305length of the key). The C<val> argument contains the SV pointer to the
54310121 306scalar being stored, and C<hash> is the precomputed hash value (zero if
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307you want C<hv_store> to calculate it for you). The C<lval> parameter
308indicates whether this fetch is actually a part of a store operation, in
309which case a new undefined value will be added to the HV with the supplied
310key and C<hv_fetch> will return as if the value had already existed.
a0d0e21e 311
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312Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
313C<SV*>. To access the scalar value, you must first dereference the return
314value. However, you should check to make sure that the return value is
315not NULL before dereferencing it.
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316
317These two functions check if a hash table entry exists, and deletes it.
318
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319 bool hv_exists(HV*, const char* key, U32 klen);
320 SV* hv_delete(HV*, const char* key, U32 klen, I32 flags);
a0d0e21e 321
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322If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
323create and return a mortal copy of the deleted value.
324
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325And more miscellaneous functions:
326
327 void hv_clear(HV*);
a0d0e21e 328 void hv_undef(HV*);
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329
330Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
331table but does not actually delete the hash table. The C<hv_undef> deletes
332both the entries and the hash table itself.
a0d0e21e 333
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334Perl keeps the actual data in linked list of structures with a typedef of HE.
335These contain the actual key and value pointers (plus extra administrative
336overhead). The key is a string pointer; the value is an C<SV*>. However,
337once you have an C<HE*>, to get the actual key and value, use the routines
338specified below.
339
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340 I32 hv_iterinit(HV*);
341 /* Prepares starting point to traverse hash table */
342 HE* hv_iternext(HV*);
343 /* Get the next entry, and return a pointer to a
344 structure that has both the key and value */
345 char* hv_iterkey(HE* entry, I32* retlen);
346 /* Get the key from an HE structure and also return
347 the length of the key string */
cb1a09d0 348 SV* hv_iterval(HV*, HE* entry);
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349 /* Return a SV pointer to the value of the HE
350 structure */
cb1a09d0 351 SV* hv_iternextsv(HV*, char** key, I32* retlen);
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352 /* This convenience routine combines hv_iternext,
353 hv_iterkey, and hv_iterval. The key and retlen
354 arguments are return values for the key and its
355 length. The value is returned in the SV* argument */
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356
357If you know the name of a hash variable, you can get a pointer to its HV
358by using the following:
359
5f05dabc 360 HV* perl_get_hv("package::varname", FALSE);
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361
362This returns NULL if the variable does not exist.
363
8ebc5c01 364The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
a0d0e21e 365
a0d0e21e 366 hash = 0;
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367 while (klen--)
368 hash = (hash * 33) + *key++;
87275199 369 hash = hash + (hash >> 5); /* after 5.6 */
ab192400 370
87275199 371The last step was added in version 5.6 to improve distribution of
ab192400 372lower bits in the resulting hash value.
a0d0e21e 373
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374See L<Understanding the Magic of Tied Hashes and Arrays> for more
375information on how to use the hash access functions on tied hashes.
376
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377=head2 Hash API Extensions
378
379Beginning with version 5.004, the following functions are also supported:
380
381 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
382 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
383
384 bool hv_exists_ent (HV* tb, SV* key, U32 hash);
385 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
386
387 SV* hv_iterkeysv (HE* entry);
388
389Note that these functions take C<SV*> keys, which simplifies writing
390of extension code that deals with hash structures. These functions
391also allow passing of C<SV*> keys to C<tie> functions without forcing
392you to stringify the keys (unlike the previous set of functions).
393
394They also return and accept whole hash entries (C<HE*>), making their
395use more efficient (since the hash number for a particular string
396doesn't have to be recomputed every time). See L<API LISTING> later in
397this document for detailed descriptions.
398
399The following macros must always be used to access the contents of hash
400entries. Note that the arguments to these macros must be simple
401variables, since they may get evaluated more than once. See
402L<API LISTING> later in this document for detailed descriptions of these
403macros.
404
405 HePV(HE* he, STRLEN len)
406 HeVAL(HE* he)
407 HeHASH(HE* he)
408 HeSVKEY(HE* he)
409 HeSVKEY_force(HE* he)
410 HeSVKEY_set(HE* he, SV* sv)
411
412These two lower level macros are defined, but must only be used when
413dealing with keys that are not C<SV*>s:
414
415 HeKEY(HE* he)
416 HeKLEN(HE* he)
417
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418Note that both C<hv_store> and C<hv_store_ent> do not increment the
419reference count of the stored C<val>, which is the caller's responsibility.
420If these functions return a NULL value, the caller will usually have to
421decrement the reference count of C<val> to avoid a memory leak.
1e422769 422
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423=head2 References
424
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425References are a special type of scalar that point to other data types
426(including references).
a0d0e21e 427
07fa94a1 428To create a reference, use either of the following functions:
a0d0e21e 429
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430 SV* newRV_inc((SV*) thing);
431 SV* newRV_noinc((SV*) thing);
a0d0e21e 432
5f05dabc 433The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
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434functions are identical except that C<newRV_inc> increments the reference
435count of the C<thing>, while C<newRV_noinc> does not. For historical
436reasons, C<newRV> is a synonym for C<newRV_inc>.
437
438Once you have a reference, you can use the following macro to dereference
439the reference:
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440
441 SvRV(SV*)
442
443then call the appropriate routines, casting the returned C<SV*> to either an
d1b91892 444C<AV*> or C<HV*>, if required.
a0d0e21e 445
d1b91892 446To determine if an SV is a reference, you can use the following macro:
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447
448 SvROK(SV*)
449
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450To discover what type of value the reference refers to, use the following
451macro and then check the return value.
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452
453 SvTYPE(SvRV(SV*))
454
455The most useful types that will be returned are:
456
457 SVt_IV Scalar
458 SVt_NV Scalar
459 SVt_PV Scalar
5f05dabc 460 SVt_RV Scalar
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461 SVt_PVAV Array
462 SVt_PVHV Hash
463 SVt_PVCV Code
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464 SVt_PVGV Glob (possible a file handle)
465 SVt_PVMG Blessed or Magical Scalar
466
467 See the sv.h header file for more details.
d1b91892 468
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469=head2 Blessed References and Class Objects
470
471References are also used to support object-oriented programming. In the
472OO lexicon, an object is simply a reference that has been blessed into a
473package (or class). Once blessed, the programmer may now use the reference
474to access the various methods in the class.
475
476A reference can be blessed into a package with the following function:
477
478 SV* sv_bless(SV* sv, HV* stash);
479
480The C<sv> argument must be a reference. The C<stash> argument specifies
3fe9a6f1 481which class the reference will belong to. See
2ae324a7 482L<Stashes and Globs> for information on converting class names into stashes.
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483
484/* Still under construction */
485
486Upgrades rv to reference if not already one. Creates new SV for rv to
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487point to. If C<classname> is non-null, the SV is blessed into the specified
488class. SV is returned.
cb1a09d0 489
08105a92 490 SV* newSVrv(SV* rv, const char* classname);
cb1a09d0 491
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492Copies integer or double into an SV whose reference is C<rv>. SV is blessed
493if C<classname> is non-null.
cb1a09d0 494
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495 SV* sv_setref_iv(SV* rv, const char* classname, IV iv);
496 SV* sv_setref_nv(SV* rv, const char* classname, NV iv);
cb1a09d0 497
5f05dabc 498Copies the pointer value (I<the address, not the string!>) into an SV whose
8ebc5c01 499reference is rv. SV is blessed if C<classname> is non-null.
cb1a09d0 500
08105a92 501 SV* sv_setref_pv(SV* rv, const char* classname, PV iv);
cb1a09d0 502
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503Copies string into an SV whose reference is C<rv>. Set length to 0 to let
504Perl calculate the string length. SV is blessed if C<classname> is non-null.
cb1a09d0 505
e65f3abd 506 SV* sv_setref_pvn(SV* rv, const char* classname, PV iv, STRLEN length);
cb1a09d0 507
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508Tests whether the SV is blessed into the specified class. It does not
509check inheritance relationships.
510
08105a92 511 int sv_isa(SV* sv, const char* name);
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512
513Tests whether the SV is a reference to a blessed object.
514
515 int sv_isobject(SV* sv);
516
517Tests whether the SV is derived from the specified class. SV can be either
518a reference to a blessed object or a string containing a class name. This
519is the function implementing the C<UNIVERSAL::isa> functionality.
520
08105a92 521 bool sv_derived_from(SV* sv, const char* name);
9abd00ed
GS
522
523To check if you've got an object derived from a specific class you have
524to write:
525
526 if (sv_isobject(sv) && sv_derived_from(sv, class)) { ... }
cb1a09d0 527
5f05dabc 528=head2 Creating New Variables
cb1a09d0 529
5f05dabc
PP
530To create a new Perl variable with an undef value which can be accessed from
531your Perl script, use the following routines, depending on the variable type.
cb1a09d0 532
5f05dabc
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533 SV* perl_get_sv("package::varname", TRUE);
534 AV* perl_get_av("package::varname", TRUE);
535 HV* perl_get_hv("package::varname", TRUE);
cb1a09d0
AD
536
537Notice the use of TRUE as the second parameter. The new variable can now
538be set, using the routines appropriate to the data type.
539
5f05dabc
PP
540There are additional macros whose values may be bitwise OR'ed with the
541C<TRUE> argument to enable certain extra features. Those bits are:
cb1a09d0 542
5f05dabc 543 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
54310121 544 "Name <varname> used only once: possible typo" warning.
07fa94a1
JO
545 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
546 the variable did not exist before the function was called.
cb1a09d0 547
07fa94a1
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548If you do not specify a package name, the variable is created in the current
549package.
cb1a09d0 550
5f05dabc 551=head2 Reference Counts and Mortality
a0d0e21e 552
54310121
PP
553Perl uses an reference count-driven garbage collection mechanism. SVs,
554AVs, or HVs (xV for short in the following) start their life with a
55497cff 555reference count of 1. If the reference count of an xV ever drops to 0,
07fa94a1 556then it will be destroyed and its memory made available for reuse.
55497cff
PP
557
558This normally doesn't happen at the Perl level unless a variable is
5f05dabc
PP
559undef'ed or the last variable holding a reference to it is changed or
560overwritten. At the internal level, however, reference counts can be
55497cff
PP
561manipulated with the following macros:
562
563 int SvREFCNT(SV* sv);
5f05dabc 564 SV* SvREFCNT_inc(SV* sv);
55497cff
PP
565 void SvREFCNT_dec(SV* sv);
566
567However, there is one other function which manipulates the reference
07fa94a1
JO
568count of its argument. The C<newRV_inc> function, you will recall,
569creates a reference to the specified argument. As a side effect,
570it increments the argument's reference count. If this is not what
571you want, use C<newRV_noinc> instead.
572
573For example, imagine you want to return a reference from an XSUB function.
574Inside the XSUB routine, you create an SV which initially has a reference
575count of one. Then you call C<newRV_inc>, passing it the just-created SV.
5f05dabc
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576This returns the reference as a new SV, but the reference count of the
577SV you passed to C<newRV_inc> has been incremented to two. Now you
07fa94a1
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578return the reference from the XSUB routine and forget about the SV.
579But Perl hasn't! Whenever the returned reference is destroyed, the
580reference count of the original SV is decreased to one and nothing happens.
581The SV will hang around without any way to access it until Perl itself
582terminates. This is a memory leak.
5f05dabc
PP
583
584The correct procedure, then, is to use C<newRV_noinc> instead of
faed5253
JO
585C<newRV_inc>. Then, if and when the last reference is destroyed,
586the reference count of the SV will go to zero and it will be destroyed,
07fa94a1 587stopping any memory leak.
55497cff 588
5f05dabc 589There are some convenience functions available that can help with the
54310121 590destruction of xVs. These functions introduce the concept of "mortality".
07fa94a1
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591An xV that is mortal has had its reference count marked to be decremented,
592but not actually decremented, until "a short time later". Generally the
593term "short time later" means a single Perl statement, such as a call to
54310121 594an XSUB function. The actual determinant for when mortal xVs have their
07fa94a1
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595reference count decremented depends on two macros, SAVETMPS and FREETMPS.
596See L<perlcall> and L<perlxs> for more details on these macros.
55497cff
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597
598"Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
599However, if you mortalize a variable twice, the reference count will
600later be decremented twice.
601
602You should be careful about creating mortal variables. Strange things
603can happen if you make the same value mortal within multiple contexts,
5f05dabc 604or if you make a variable mortal multiple times.
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605
606To create a mortal variable, use the functions:
607
608 SV* sv_newmortal()
609 SV* sv_2mortal(SV*)
610 SV* sv_mortalcopy(SV*)
611
5f05dabc
PP
612The first call creates a mortal SV, the second converts an existing
613SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
614third creates a mortal copy of an existing SV.
a0d0e21e 615
54310121 616The mortal routines are not just for SVs -- AVs and HVs can be
faed5253 617made mortal by passing their address (type-casted to C<SV*>) to the
07fa94a1 618C<sv_2mortal> or C<sv_mortalcopy> routines.
a0d0e21e 619
5f05dabc 620=head2 Stashes and Globs
a0d0e21e 621
aa689395
PP
622A "stash" is a hash that contains all of the different objects that
623are contained within a package. Each key of the stash is a symbol
624name (shared by all the different types of objects that have the same
625name), and each value in the hash table is a GV (Glob Value). This GV
626in turn contains references to the various objects of that name,
627including (but not limited to) the following:
cb1a09d0 628
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629 Scalar Value
630 Array Value
631 Hash Value
a3cb178b 632 I/O Handle
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633 Format
634 Subroutine
635
9cde0e7f 636There is a single stash called "PL_defstash" that holds the items that exist
5f05dabc
PP
637in the "main" package. To get at the items in other packages, append the
638string "::" to the package name. The items in the "Foo" package are in
9cde0e7f 639the stash "Foo::" in PL_defstash. The items in the "Bar::Baz" package are
5f05dabc 640in the stash "Baz::" in "Bar::"'s stash.
a0d0e21e 641
d1b91892 642To get the stash pointer for a particular package, use the function:
a0d0e21e 643
08105a92 644 HV* gv_stashpv(const char* name, I32 create)
a0d0e21e
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645 HV* gv_stashsv(SV*, I32 create)
646
647The first function takes a literal string, the second uses the string stored
d1b91892 648in the SV. Remember that a stash is just a hash table, so you get back an
cb1a09d0 649C<HV*>. The C<create> flag will create a new package if it is set.
a0d0e21e
LW
650
651The name that C<gv_stash*v> wants is the name of the package whose symbol table
652you want. The default package is called C<main>. If you have multiply nested
d1b91892
AD
653packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
654language itself.
a0d0e21e
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655
656Alternately, if you have an SV that is a blessed reference, you can find
657out the stash pointer by using:
658
659 HV* SvSTASH(SvRV(SV*));
660
661then use the following to get the package name itself:
662
663 char* HvNAME(HV* stash);
664
5f05dabc
PP
665If you need to bless or re-bless an object you can use the following
666function:
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LW
667
668 SV* sv_bless(SV*, HV* stash)
669
670where the first argument, an C<SV*>, must be a reference, and the second
671argument is a stash. The returned C<SV*> can now be used in the same way
672as any other SV.
673
d1b91892
AD
674For more information on references and blessings, consult L<perlref>.
675
54310121 676=head2 Double-Typed SVs
0a753a76
PP
677
678Scalar variables normally contain only one type of value, an integer,
679double, pointer, or reference. Perl will automatically convert the
680actual scalar data from the stored type into the requested type.
681
682Some scalar variables contain more than one type of scalar data. For
683example, the variable C<$!> contains either the numeric value of C<errno>
684or its string equivalent from either C<strerror> or C<sys_errlist[]>.
685
686To force multiple data values into an SV, you must do two things: use the
687C<sv_set*v> routines to add the additional scalar type, then set a flag
688so that Perl will believe it contains more than one type of data. The
689four macros to set the flags are:
690
691 SvIOK_on
692 SvNOK_on
693 SvPOK_on
694 SvROK_on
695
696The particular macro you must use depends on which C<sv_set*v> routine
697you called first. This is because every C<sv_set*v> routine turns on
698only the bit for the particular type of data being set, and turns off
699all the rest.
700
701For example, to create a new Perl variable called "dberror" that contains
702both the numeric and descriptive string error values, you could use the
703following code:
704
705 extern int dberror;
706 extern char *dberror_list;
707
708 SV* sv = perl_get_sv("dberror", TRUE);
709 sv_setiv(sv, (IV) dberror);
710 sv_setpv(sv, dberror_list[dberror]);
711 SvIOK_on(sv);
712
713If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
714macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
715
716=head2 Magic Variables
a0d0e21e 717
d1b91892
AD
718[This section still under construction. Ignore everything here. Post no
719bills. Everything not permitted is forbidden.]
720
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721Any SV may be magical, that is, it has special features that a normal
722SV does not have. These features are stored in the SV structure in a
5f05dabc 723linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
d1b91892
AD
724
725 struct magic {
726 MAGIC* mg_moremagic;
727 MGVTBL* mg_virtual;
728 U16 mg_private;
729 char mg_type;
730 U8 mg_flags;
731 SV* mg_obj;
732 char* mg_ptr;
733 I32 mg_len;
734 };
735
736Note this is current as of patchlevel 0, and could change at any time.
737
738=head2 Assigning Magic
739
740Perl adds magic to an SV using the sv_magic function:
741
08105a92 742 void sv_magic(SV* sv, SV* obj, int how, const char* name, I32 namlen);
d1b91892
AD
743
744The C<sv> argument is a pointer to the SV that is to acquire a new magical
745feature.
746
747If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
748set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
749it to the beginning of the linked list of magical features. Any prior
750entry of the same type of magic is deleted. Note that this can be
5fb8527f 751overridden, and multiple instances of the same type of magic can be
d1b91892
AD
752associated with an SV.
753
54310121
PP
754The C<name> and C<namlen> arguments are used to associate a string with
755the magic, typically the name of a variable. C<namlen> is stored in the
756C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
d1b91892
AD
757copy of the name is stored in C<mg_ptr> field.
758
759The sv_magic function uses C<how> to determine which, if any, predefined
760"Magic Virtual Table" should be assigned to the C<mg_virtual> field.
cb1a09d0
AD
761See the "Magic Virtual Table" section below. The C<how> argument is also
762stored in the C<mg_type> field.
d1b91892
AD
763
764The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
765structure. If it is not the same as the C<sv> argument, the reference
766count of the C<obj> object is incremented. If it is the same, or if
04343c6d 767the C<how> argument is "#", or if it is a NULL pointer, then C<obj> is
d1b91892
AD
768merely stored, without the reference count being incremented.
769
cb1a09d0
AD
770There is also a function to add magic to an C<HV>:
771
772 void hv_magic(HV *hv, GV *gv, int how);
773
774This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
775
776To remove the magic from an SV, call the function sv_unmagic:
777
778 void sv_unmagic(SV *sv, int type);
779
780The C<type> argument should be equal to the C<how> value when the C<SV>
781was initially made magical.
782
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AD
783=head2 Magic Virtual Tables
784
785The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
786C<MGVTBL>, which is a structure of function pointers and stands for
787"Magic Virtual Table" to handle the various operations that might be
788applied to that variable.
789
790The C<MGVTBL> has five pointers to the following routine types:
791
792 int (*svt_get)(SV* sv, MAGIC* mg);
793 int (*svt_set)(SV* sv, MAGIC* mg);
794 U32 (*svt_len)(SV* sv, MAGIC* mg);
795 int (*svt_clear)(SV* sv, MAGIC* mg);
796 int (*svt_free)(SV* sv, MAGIC* mg);
797
798This MGVTBL structure is set at compile-time in C<perl.h> and there are
799currently 19 types (or 21 with overloading turned on). These different
800structures contain pointers to various routines that perform additional
801actions depending on which function is being called.
802
803 Function pointer Action taken
804 ---------------- ------------
805 svt_get Do something after the value of the SV is retrieved.
806 svt_set Do something after the SV is assigned a value.
807 svt_len Report on the SV's length.
808 svt_clear Clear something the SV represents.
809 svt_free Free any extra storage associated with the SV.
810
811For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
812to an C<mg_type> of '\0') contains:
813
814 { magic_get, magic_set, magic_len, 0, 0 }
815
816Thus, when an SV is determined to be magical and of type '\0', if a get
817operation is being performed, the routine C<magic_get> is called. All
818the various routines for the various magical types begin with C<magic_>.
819
820The current kinds of Magic Virtual Tables are:
821
bdbeb323 822 mg_type MGVTBL Type of magic
5f05dabc 823 ------- ------ ----------------------------
bdbeb323
SM
824 \0 vtbl_sv Special scalar variable
825 A vtbl_amagic %OVERLOAD hash
826 a vtbl_amagicelem %OVERLOAD hash element
827 c (none) Holds overload table (AMT) on stash
828 B vtbl_bm Boyer-Moore (fast string search)
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AD
829 E vtbl_env %ENV hash
830 e vtbl_envelem %ENV hash element
bdbeb323
SM
831 f vtbl_fm Formline ('compiled' format)
832 g vtbl_mglob m//g target / study()ed string
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AD
833 I vtbl_isa @ISA array
834 i vtbl_isaelem @ISA array element
bdbeb323
SM
835 k vtbl_nkeys scalar(keys()) lvalue
836 L (none) Debugger %_<filename
837 l vtbl_dbline Debugger %_<filename element
44a8e56a 838 o vtbl_collxfrm Locale transformation
bdbeb323
SM
839 P vtbl_pack Tied array or hash
840 p vtbl_packelem Tied array or hash element
841 q vtbl_packelem Tied scalar or handle
842 S vtbl_sig %SIG hash
843 s vtbl_sigelem %SIG hash element
d1b91892 844 t vtbl_taint Taintedness
bdbeb323
SM
845 U vtbl_uvar Available for use by extensions
846 v vtbl_vec vec() lvalue
847 x vtbl_substr substr() lvalue
848 y vtbl_defelem Shadow "foreach" iterator variable /
849 smart parameter vivification
850 * vtbl_glob GV (typeglob)
851 # vtbl_arylen Array length ($#ary)
852 . vtbl_pos pos() lvalue
853 ~ (none) Available for use by extensions
d1b91892 854
68dc0745
PP
855When an uppercase and lowercase letter both exist in the table, then the
856uppercase letter is used to represent some kind of composite type (a list
857or a hash), and the lowercase letter is used to represent an element of
d1b91892
AD
858that composite type.
859
bdbeb323
SM
860The '~' and 'U' magic types are defined specifically for use by
861extensions and will not be used by perl itself. Extensions can use
862'~' magic to 'attach' private information to variables (typically
863objects). This is especially useful because there is no way for
864normal perl code to corrupt this private information (unlike using
865extra elements of a hash object).
866
867Similarly, 'U' magic can be used much like tie() to call a C function
868any time a scalar's value is used or changed. The C<MAGIC>'s
869C<mg_ptr> field points to a C<ufuncs> structure:
870
871 struct ufuncs {
872 I32 (*uf_val)(IV, SV*);
873 I32 (*uf_set)(IV, SV*);
874 IV uf_index;
875 };
876
877When the SV is read from or written to, the C<uf_val> or C<uf_set>
878function will be called with C<uf_index> as the first arg and a
1526ead6
AB
879pointer to the SV as the second. A simple example of how to add 'U'
880magic is shown below. Note that the ufuncs structure is copied by
881sv_magic, so you can safely allocate it on the stack.
882
883 void
884 Umagic(sv)
885 SV *sv;
886 PREINIT:
887 struct ufuncs uf;
888 CODE:
889 uf.uf_val = &my_get_fn;
890 uf.uf_set = &my_set_fn;
891 uf.uf_index = 0;
892 sv_magic(sv, 0, 'U', (char*)&uf, sizeof(uf));
5f05dabc 893
bdbeb323
SM
894Note that because multiple extensions may be using '~' or 'U' magic,
895it is important for extensions to take extra care to avoid conflict.
896Typically only using the magic on objects blessed into the same class
897as the extension is sufficient. For '~' magic, it may also be
898appropriate to add an I32 'signature' at the top of the private data
899area and check that.
5f05dabc 900
ef50df4b
GS
901Also note that the C<sv_set*()> and C<sv_cat*()> functions described
902earlier do B<not> invoke 'set' magic on their targets. This must
903be done by the user either by calling the C<SvSETMAGIC()> macro after
904calling these functions, or by using one of the C<sv_set*_mg()> or
905C<sv_cat*_mg()> functions. Similarly, generic C code must call the
906C<SvGETMAGIC()> macro to invoke any 'get' magic if they use an SV
907obtained from external sources in functions that don't handle magic.
908L<API LISTING> later in this document identifies such functions.
189b2af5
GS
909For example, calls to the C<sv_cat*()> functions typically need to be
910followed by C<SvSETMAGIC()>, but they don't need a prior C<SvGETMAGIC()>
911since their implementation handles 'get' magic.
912
d1b91892
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913=head2 Finding Magic
914
915 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
916
917This routine returns a pointer to the C<MAGIC> structure stored in the SV.
918If the SV does not have that magical feature, C<NULL> is returned. Also,
54310121 919if the SV is not of type SVt_PVMG, Perl may core dump.
d1b91892 920
08105a92 921 int mg_copy(SV* sv, SV* nsv, const char* key, STRLEN klen);
d1b91892
AD
922
923This routine checks to see what types of magic C<sv> has. If the mg_type
68dc0745
PP
924field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
925the mg_type field is changed to be the lowercase letter.
a0d0e21e 926
04343c6d
GS
927=head2 Understanding the Magic of Tied Hashes and Arrays
928
929Tied hashes and arrays are magical beasts of the 'P' magic type.
9edb2b46
GS
930
931WARNING: As of the 5.004 release, proper usage of the array and hash
932access functions requires understanding a few caveats. Some
933of these caveats are actually considered bugs in the API, to be fixed
934in later releases, and are bracketed with [MAYCHANGE] below. If
935you find yourself actually applying such information in this section, be
936aware that the behavior may change in the future, umm, without warning.
04343c6d 937
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938The perl tie function associates a variable with an object that implements
939the various GET, SET etc methods. To perform the equivalent of the perl
940tie function from an XSUB, you must mimic this behaviour. The code below
941carries out the necessary steps - firstly it creates a new hash, and then
942creates a second hash which it blesses into the class which will implement
943the tie methods. Lastly it ties the two hashes together, and returns a
944reference to the new tied hash. Note that the code below does NOT call the
945TIEHASH method in the MyTie class -
946see L<Calling Perl Routines from within C Programs> for details on how
947to do this.
948
949 SV*
950 mytie()
951 PREINIT:
952 HV *hash;
953 HV *stash;
954 SV *tie;
955 CODE:
956 hash = newHV();
957 tie = newRV_noinc((SV*)newHV());
958 stash = gv_stashpv("MyTie", TRUE);
959 sv_bless(tie, stash);
960 hv_magic(hash, tie, 'P');
961 RETVAL = newRV_noinc(hash);
962 OUTPUT:
963 RETVAL
964
04343c6d
GS
965The C<av_store> function, when given a tied array argument, merely
966copies the magic of the array onto the value to be "stored", using
967C<mg_copy>. It may also return NULL, indicating that the value did not
9edb2b46
GS
968actually need to be stored in the array. [MAYCHANGE] After a call to
969C<av_store> on a tied array, the caller will usually need to call
970C<mg_set(val)> to actually invoke the perl level "STORE" method on the
971TIEARRAY object. If C<av_store> did return NULL, a call to
972C<SvREFCNT_dec(val)> will also be usually necessary to avoid a memory
973leak. [/MAYCHANGE]
04343c6d
GS
974
975The previous paragraph is applicable verbatim to tied hash access using the
976C<hv_store> and C<hv_store_ent> functions as well.
977
978C<av_fetch> and the corresponding hash functions C<hv_fetch> and
979C<hv_fetch_ent> actually return an undefined mortal value whose magic
980has been initialized using C<mg_copy>. Note the value so returned does not
9edb2b46
GS
981need to be deallocated, as it is already mortal. [MAYCHANGE] But you will
982need to call C<mg_get()> on the returned value in order to actually invoke
983the perl level "FETCH" method on the underlying TIE object. Similarly,
04343c6d
GS
984you may also call C<mg_set()> on the return value after possibly assigning
985a suitable value to it using C<sv_setsv>, which will invoke the "STORE"
9edb2b46 986method on the TIE object. [/MAYCHANGE]
04343c6d 987
9edb2b46 988[MAYCHANGE]
04343c6d
GS
989In other words, the array or hash fetch/store functions don't really
990fetch and store actual values in the case of tied arrays and hashes. They
991merely call C<mg_copy> to attach magic to the values that were meant to be
992"stored" or "fetched". Later calls to C<mg_get> and C<mg_set> actually
993do the job of invoking the TIE methods on the underlying objects. Thus
9edb2b46 994the magic mechanism currently implements a kind of lazy access to arrays
04343c6d
GS
995and hashes.
996
997Currently (as of perl version 5.004), use of the hash and array access
998functions requires the user to be aware of whether they are operating on
9edb2b46
GS
999"normal" hashes and arrays, or on their tied variants. The API may be
1000changed to provide more transparent access to both tied and normal data
1001types in future versions.
1002[/MAYCHANGE]
04343c6d
GS
1003
1004You would do well to understand that the TIEARRAY and TIEHASH interfaces
1005are mere sugar to invoke some perl method calls while using the uniform hash
1006and array syntax. The use of this sugar imposes some overhead (typically
1007about two to four extra opcodes per FETCH/STORE operation, in addition to
1008the creation of all the mortal variables required to invoke the methods).
1009This overhead will be comparatively small if the TIE methods are themselves
1010substantial, but if they are only a few statements long, the overhead
1011will not be insignificant.
1012
d1c897a1
IZ
1013=head2 Localizing changes
1014
1015Perl has a very handy construction
1016
1017 {
1018 local $var = 2;
1019 ...
1020 }
1021
1022This construction is I<approximately> equivalent to
1023
1024 {
1025 my $oldvar = $var;
1026 $var = 2;
1027 ...
1028 $var = $oldvar;
1029 }
1030
1031The biggest difference is that the first construction would
1032reinstate the initial value of $var, irrespective of how control exits
1033the block: C<goto>, C<return>, C<die>/C<eval> etc. It is a little bit
1034more efficient as well.
1035
1036There is a way to achieve a similar task from C via Perl API: create a
1037I<pseudo-block>, and arrange for some changes to be automatically
1038undone at the end of it, either explicit, or via a non-local exit (via
1039die()). A I<block>-like construct is created by a pair of
b687b08b
TC
1040C<ENTER>/C<LEAVE> macros (see L<perlcall/"Returning a Scalar">).
1041Such a construct may be created specially for some important localized
1042task, or an existing one (like boundaries of enclosing Perl
1043subroutine/block, or an existing pair for freeing TMPs) may be
1044used. (In the second case the overhead of additional localization must
1045be almost negligible.) Note that any XSUB is automatically enclosed in
1046an C<ENTER>/C<LEAVE> pair.
d1c897a1
IZ
1047
1048Inside such a I<pseudo-block> the following service is available:
1049
1050=over
1051
1052=item C<SAVEINT(int i)>
1053
1054=item C<SAVEIV(IV i)>
1055
1056=item C<SAVEI32(I32 i)>
1057
1058=item C<SAVELONG(long i)>
1059
1060These macros arrange things to restore the value of integer variable
1061C<i> at the end of enclosing I<pseudo-block>.
1062
1063=item C<SAVESPTR(s)>
1064
1065=item C<SAVEPPTR(p)>
1066
1067These macros arrange things to restore the value of pointers C<s> and
1068C<p>. C<s> must be a pointer of a type which survives conversion to
1069C<SV*> and back, C<p> should be able to survive conversion to C<char*>
1070and back.
1071
1072=item C<SAVEFREESV(SV *sv)>
1073
1074The refcount of C<sv> would be decremented at the end of
1075I<pseudo-block>. This is similar to C<sv_2mortal>, which should (?) be
1076used instead.
1077
1078=item C<SAVEFREEOP(OP *op)>
1079
1080The C<OP *> is op_free()ed at the end of I<pseudo-block>.
1081
1082=item C<SAVEFREEPV(p)>
1083
1084The chunk of memory which is pointed to by C<p> is Safefree()ed at the
1085end of I<pseudo-block>.
1086
1087=item C<SAVECLEARSV(SV *sv)>
1088
1089Clears a slot in the current scratchpad which corresponds to C<sv> at
1090the end of I<pseudo-block>.
1091
1092=item C<SAVEDELETE(HV *hv, char *key, I32 length)>
1093
1094The key C<key> of C<hv> is deleted at the end of I<pseudo-block>. The
1095string pointed to by C<key> is Safefree()ed. If one has a I<key> in
1096short-lived storage, the corresponding string may be reallocated like
1097this:
1098
9cde0e7f 1099 SAVEDELETE(PL_defstash, savepv(tmpbuf), strlen(tmpbuf));
d1c897a1
IZ
1100
1101=item C<SAVEDESTRUCTOR(f,p)>
1102
1103At the end of I<pseudo-block> the function C<f> is called with the
1104only argument (of type C<void*>) C<p>.
1105
1106=item C<SAVESTACK_POS()>
1107
1108The current offset on the Perl internal stack (cf. C<SP>) is restored
1109at the end of I<pseudo-block>.
1110
1111=back
1112
1113The following API list contains functions, thus one needs to
1114provide pointers to the modifiable data explicitly (either C pointers,
1115or Perlish C<GV *>s). Where the above macros take C<int>, a similar
1116function takes C<int *>.
1117
1118=over
1119
1120=item C<SV* save_scalar(GV *gv)>
1121
1122Equivalent to Perl code C<local $gv>.
1123
1124=item C<AV* save_ary(GV *gv)>
1125
1126=item C<HV* save_hash(GV *gv)>
1127
1128Similar to C<save_scalar>, but localize C<@gv> and C<%gv>.
1129
1130=item C<void save_item(SV *item)>
1131
1132Duplicates the current value of C<SV>, on the exit from the current
1133C<ENTER>/C<LEAVE> I<pseudo-block> will restore the value of C<SV>
1134using the stored value.
1135
1136=item C<void save_list(SV **sarg, I32 maxsarg)>
1137
1138A variant of C<save_item> which takes multiple arguments via an array
1139C<sarg> of C<SV*> of length C<maxsarg>.
1140
1141=item C<SV* save_svref(SV **sptr)>
1142
1143Similar to C<save_scalar>, but will reinstate a C<SV *>.
1144
1145=item C<void save_aptr(AV **aptr)>
1146
1147=item C<void save_hptr(HV **hptr)>
1148
1149Similar to C<save_svref>, but localize C<AV *> and C<HV *>.
1150
1151=back
1152
1153The C<Alias> module implements localization of the basic types within the
1154I<caller's scope>. People who are interested in how to localize things in
1155the containing scope should take a look there too.
1156
0a753a76 1157=head1 Subroutines
a0d0e21e 1158
68dc0745 1159=head2 XSUBs and the Argument Stack
5f05dabc
PP
1160
1161The XSUB mechanism is a simple way for Perl programs to access C subroutines.
1162An XSUB routine will have a stack that contains the arguments from the Perl
1163program, and a way to map from the Perl data structures to a C equivalent.
1164
1165The stack arguments are accessible through the C<ST(n)> macro, which returns
1166the C<n>'th stack argument. Argument 0 is the first argument passed in the
1167Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
1168an C<SV*> is used.
1169
1170Most of the time, output from the C routine can be handled through use of
1171the RETVAL and OUTPUT directives. However, there are some cases where the
1172argument stack is not already long enough to handle all the return values.
1173An example is the POSIX tzname() call, which takes no arguments, but returns
1174two, the local time zone's standard and summer time abbreviations.
1175
1176To handle this situation, the PPCODE directive is used and the stack is
1177extended using the macro:
1178
924508f0 1179 EXTEND(SP, num);
5f05dabc 1180
924508f0
GS
1181where C<SP> is the macro that represents the local copy of the stack pointer,
1182and C<num> is the number of elements the stack should be extended by.
5f05dabc
PP
1183
1184Now that there is room on the stack, values can be pushed on it using the
54310121 1185macros to push IVs, doubles, strings, and SV pointers respectively:
5f05dabc
PP
1186
1187 PUSHi(IV)
1188 PUSHn(double)
1189 PUSHp(char*, I32)
1190 PUSHs(SV*)
1191
1192And now the Perl program calling C<tzname>, the two values will be assigned
1193as in:
1194
1195 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
1196
1197An alternate (and possibly simpler) method to pushing values on the stack is
1198to use the macros:
1199
1200 XPUSHi(IV)
1201 XPUSHn(double)
1202 XPUSHp(char*, I32)
1203 XPUSHs(SV*)
1204
1205These macros automatically adjust the stack for you, if needed. Thus, you
1206do not need to call C<EXTEND> to extend the stack.
1207
1208For more information, consult L<perlxs> and L<perlxstut>.
1209
1210=head2 Calling Perl Routines from within C Programs
a0d0e21e
LW
1211
1212There are four routines that can be used to call a Perl subroutine from
1213within a C program. These four are:
1214
1215 I32 perl_call_sv(SV*, I32);
08105a92
GS
1216 I32 perl_call_pv(const char*, I32);
1217 I32 perl_call_method(const char*, I32);
1218 I32 perl_call_argv(const char*, I32, register char**);
a0d0e21e 1219
d1b91892
AD
1220The routine most often used is C<perl_call_sv>. The C<SV*> argument
1221contains either the name of the Perl subroutine to be called, or a
1222reference to the subroutine. The second argument consists of flags
1223that control the context in which the subroutine is called, whether
1224or not the subroutine is being passed arguments, how errors should be
1225trapped, and how to treat return values.
a0d0e21e
LW
1226
1227All four routines return the number of arguments that the subroutine returned
1228on the Perl stack.
1229
d1b91892
AD
1230When using any of these routines (except C<perl_call_argv>), the programmer
1231must manipulate the Perl stack. These include the following macros and
1232functions:
a0d0e21e
LW
1233
1234 dSP
924508f0 1235 SP
a0d0e21e
LW
1236 PUSHMARK()
1237 PUTBACK
1238 SPAGAIN
1239 ENTER
1240 SAVETMPS
1241 FREETMPS
1242 LEAVE
1243 XPUSH*()
cb1a09d0 1244 POP*()
a0d0e21e 1245
5f05dabc
PP
1246For a detailed description of calling conventions from C to Perl,
1247consult L<perlcall>.
a0d0e21e 1248
5f05dabc 1249=head2 Memory Allocation
a0d0e21e 1250
86058a2d
GS
1251All memory meant to be used with the Perl API functions should be manipulated
1252using the macros described in this section. The macros provide the necessary
1253transparency between differences in the actual malloc implementation that is
1254used within perl.
1255
1256It is suggested that you enable the version of malloc that is distributed
5f05dabc 1257with Perl. It keeps pools of various sizes of unallocated memory in
07fa94a1
JO
1258order to satisfy allocation requests more quickly. However, on some
1259platforms, it may cause spurious malloc or free errors.
d1b91892
AD
1260
1261 New(x, pointer, number, type);
1262 Newc(x, pointer, number, type, cast);
1263 Newz(x, pointer, number, type);
1264
07fa94a1 1265These three macros are used to initially allocate memory.
5f05dabc
PP
1266
1267The first argument C<x> was a "magic cookie" that was used to keep track
1268of who called the macro, to help when debugging memory problems. However,
07fa94a1
JO
1269the current code makes no use of this feature (most Perl developers now
1270use run-time memory checkers), so this argument can be any number.
5f05dabc
PP
1271
1272The second argument C<pointer> should be the name of a variable that will
1273point to the newly allocated memory.
d1b91892 1274
d1b91892
AD
1275The third and fourth arguments C<number> and C<type> specify how many of
1276the specified type of data structure should be allocated. The argument
1277C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
1278should be used if the C<pointer> argument is different from the C<type>
1279argument.
1280
1281Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
1282to zero out all the newly allocated memory.
1283
1284 Renew(pointer, number, type);
1285 Renewc(pointer, number, type, cast);
1286 Safefree(pointer)
1287
1288These three macros are used to change a memory buffer size or to free a
1289piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
1290match those of C<New> and C<Newc> with the exception of not needing the
1291"magic cookie" argument.
1292
1293 Move(source, dest, number, type);
1294 Copy(source, dest, number, type);
1295 Zero(dest, number, type);
1296
1297These three macros are used to move, copy, or zero out previously allocated
1298memory. The C<source> and C<dest> arguments point to the source and
1299destination starting points. Perl will move, copy, or zero out C<number>
1300instances of the size of the C<type> data structure (using the C<sizeof>
1301function).
a0d0e21e 1302
5f05dabc 1303=head2 PerlIO
ce3d39e2 1304
5f05dabc
PP
1305The most recent development releases of Perl has been experimenting with
1306removing Perl's dependency on the "normal" standard I/O suite and allowing
1307other stdio implementations to be used. This involves creating a new
1308abstraction layer that then calls whichever implementation of stdio Perl
68dc0745 1309was compiled with. All XSUBs should now use the functions in the PerlIO
5f05dabc
PP
1310abstraction layer and not make any assumptions about what kind of stdio
1311is being used.
1312
1313For a complete description of the PerlIO abstraction, consult L<perlapio>.
1314
8ebc5c01 1315=head2 Putting a C value on Perl stack
ce3d39e2
IZ
1316
1317A lot of opcodes (this is an elementary operation in the internal perl
1318stack machine) put an SV* on the stack. However, as an optimization
1319the corresponding SV is (usually) not recreated each time. The opcodes
1320reuse specially assigned SVs (I<target>s) which are (as a corollary)
1321not constantly freed/created.
1322
0a753a76 1323Each of the targets is created only once (but see
ce3d39e2
IZ
1324L<Scratchpads and recursion> below), and when an opcode needs to put
1325an integer, a double, or a string on stack, it just sets the
1326corresponding parts of its I<target> and puts the I<target> on stack.
1327
1328The macro to put this target on stack is C<PUSHTARG>, and it is
1329directly used in some opcodes, as well as indirectly in zillions of
1330others, which use it via C<(X)PUSH[pni]>.
1331
8ebc5c01 1332=head2 Scratchpads
ce3d39e2 1333
54310121 1334The question remains on when the SVs which are I<target>s for opcodes
5f05dabc
PP
1335are created. The answer is that they are created when the current unit --
1336a subroutine or a file (for opcodes for statements outside of
1337subroutines) -- is compiled. During this time a special anonymous Perl
ce3d39e2
IZ
1338array is created, which is called a scratchpad for the current
1339unit.
1340
54310121 1341A scratchpad keeps SVs which are lexicals for the current unit and are
ce3d39e2
IZ
1342targets for opcodes. One can deduce that an SV lives on a scratchpad
1343by looking on its flags: lexicals have C<SVs_PADMY> set, and
1344I<target>s have C<SVs_PADTMP> set.
1345
54310121
PP
1346The correspondence between OPs and I<target>s is not 1-to-1. Different
1347OPs in the compile tree of the unit can use the same target, if this
ce3d39e2
IZ
1348would not conflict with the expected life of the temporary.
1349
2ae324a7 1350=head2 Scratchpads and recursion
ce3d39e2
IZ
1351
1352In fact it is not 100% true that a compiled unit contains a pointer to
1353the scratchpad AV. In fact it contains a pointer to an AV of
1354(initially) one element, and this element is the scratchpad AV. Why do
1355we need an extra level of indirection?
1356
1357The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1358these can create several execution pointers going into the same
1359subroutine. For the subroutine-child not write over the temporaries
1360for the subroutine-parent (lifespan of which covers the call to the
1361child), the parent and the child should have different
1362scratchpads. (I<And> the lexicals should be separate anyway!)
1363
5f05dabc
PP
1364So each subroutine is born with an array of scratchpads (of length 1).
1365On each entry to the subroutine it is checked that the current
ce3d39e2
IZ
1366depth of the recursion is not more than the length of this array, and
1367if it is, new scratchpad is created and pushed into the array.
1368
1369The I<target>s on this scratchpad are C<undef>s, but they are already
1370marked with correct flags.
1371
0a753a76
PP
1372=head1 Compiled code
1373
1374=head2 Code tree
1375
1376Here we describe the internal form your code is converted to by
1377Perl. Start with a simple example:
1378
1379 $a = $b + $c;
1380
1381This is converted to a tree similar to this one:
1382
1383 assign-to
1384 / \
1385 + $a
1386 / \
1387 $b $c
1388
7b8d334a 1389(but slightly more complicated). This tree reflects the way Perl
0a753a76
PP
1390parsed your code, but has nothing to do with the execution order.
1391There is an additional "thread" going through the nodes of the tree
1392which shows the order of execution of the nodes. In our simplified
1393example above it looks like:
1394
1395 $b ---> $c ---> + ---> $a ---> assign-to
1396
1397But with the actual compile tree for C<$a = $b + $c> it is different:
1398some nodes I<optimized away>. As a corollary, though the actual tree
1399contains more nodes than our simplified example, the execution order
1400is the same as in our example.
1401
1402=head2 Examining the tree
1403
1404If you have your perl compiled for debugging (usually done with C<-D
1405optimize=-g> on C<Configure> command line), you may examine the
1406compiled tree by specifying C<-Dx> on the Perl command line. The
1407output takes several lines per node, and for C<$b+$c> it looks like
1408this:
1409
1410 5 TYPE = add ===> 6
1411 TARG = 1
1412 FLAGS = (SCALAR,KIDS)
1413 {
1414 TYPE = null ===> (4)
1415 (was rv2sv)
1416 FLAGS = (SCALAR,KIDS)
1417 {
1418 3 TYPE = gvsv ===> 4
1419 FLAGS = (SCALAR)
1420 GV = main::b
1421 }
1422 }
1423 {
1424 TYPE = null ===> (5)
1425 (was rv2sv)
1426 FLAGS = (SCALAR,KIDS)
1427 {
1428 4 TYPE = gvsv ===> 5
1429 FLAGS = (SCALAR)
1430 GV = main::c
1431 }
1432 }
1433
1434This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1435not optimized away (one per number in the left column). The immediate
1436children of the given node correspond to C<{}> pairs on the same level
1437of indentation, thus this listing corresponds to the tree:
1438
1439 add
1440 / \
1441 null null
1442 | |
1443 gvsv gvsv
1444
1445The execution order is indicated by C<===E<gt>> marks, thus it is C<3
14464 5 6> (node C<6> is not included into above listing), i.e.,
1447C<gvsv gvsv add whatever>.
1448
1449=head2 Compile pass 1: check routines
1450
1451The tree is created by the I<pseudo-compiler> while yacc code feeds it
1452the constructions it recognizes. Since yacc works bottom-up, so does
1453the first pass of perl compilation.
1454
1455What makes this pass interesting for perl developers is that some
1456optimization may be performed on this pass. This is optimization by
1457so-called I<check routines>. The correspondence between node names
1458and corresponding check routines is described in F<opcode.pl> (do not
1459forget to run C<make regen_headers> if you modify this file).
1460
1461A check routine is called when the node is fully constructed except
7b8d334a 1462for the execution-order thread. Since at this time there are no
0a753a76
PP
1463back-links to the currently constructed node, one can do most any
1464operation to the top-level node, including freeing it and/or creating
1465new nodes above/below it.
1466
1467The check routine returns the node which should be inserted into the
1468tree (if the top-level node was not modified, check routine returns
1469its argument).
1470
1471By convention, check routines have names C<ck_*>. They are usually
1472called from C<new*OP> subroutines (or C<convert>) (which in turn are
1473called from F<perly.y>).
1474
1475=head2 Compile pass 1a: constant folding
1476
1477Immediately after the check routine is called the returned node is
1478checked for being compile-time executable. If it is (the value is
1479judged to be constant) it is immediately executed, and a I<constant>
1480node with the "return value" of the corresponding subtree is
1481substituted instead. The subtree is deleted.
1482
1483If constant folding was not performed, the execution-order thread is
1484created.
1485
1486=head2 Compile pass 2: context propagation
1487
1488When a context for a part of compile tree is known, it is propagated
a3cb178b 1489down through the tree. At this time the context can have 5 values
0a753a76
PP
1490(instead of 2 for runtime context): void, boolean, scalar, list, and
1491lvalue. In contrast with the pass 1 this pass is processed from top
1492to bottom: a node's context determines the context for its children.
1493
1494Additional context-dependent optimizations are performed at this time.
1495Since at this moment the compile tree contains back-references (via
1496"thread" pointers), nodes cannot be free()d now. To allow
1497optimized-away nodes at this stage, such nodes are null()ified instead
1498of free()ing (i.e. their type is changed to OP_NULL).
1499
1500=head2 Compile pass 3: peephole optimization
1501
1502After the compile tree for a subroutine (or for an C<eval> or a file)
1503is created, an additional pass over the code is performed. This pass
1504is neither top-down or bottom-up, but in the execution order (with
7b8d334a 1505additional complications for conditionals). These optimizations are
0a753a76
PP
1506done in the subroutine peep(). Optimizations performed at this stage
1507are subject to the same restrictions as in the pass 2.
1508
ee072b34
GS
1509=head1 The Perl API
1510
1511WARNING: This information is subject to radical changes prior to
1512the Perl 5.6 release. Use with caution.
1513
1514=head2 Background and PERL_IMPLICIT_CONTEXT
1515
1516The Perl interpreter can be regarded as a closed box: it has an API
1517for feeding it code or otherwise making it do things, but it also has
1518functions for its own use. This smells a lot like an object, and
1519there are ways for you to build Perl so that you can have multiple
1520interpreters, with one interpreter represented either as a C++ object,
1521a C structure, or inside a thread. The thread, the C structure, or
1522the C++ object will contain all the context, the state of that
1523interpreter.
1524
54aff467
GS
1525Three macros control the major Perl build flavors: MULTIPLICITY,
1526USE_THREADS and PERL_OBJECT. The MULTIPLICITY build has a C structure
1527that packages all the interpreter state, there is a similar thread-specific
1528data structure under USE_THREADS, and the PERL_OBJECT build has a C++
1529class to maintain interpreter state. In all three cases,
1530PERL_IMPLICIT_CONTEXT is also normally defined, and enables the
1531support for passing in a "hidden" first argument that represents all three
1532data structures. (The traditional MULTIPLICITY and USE_THREADS builds
1533built without PERL_IMPLICIT_CONTEXT may also be supported, but this is
1534currently somewhat broken.)
1535
1536All this obviously requires a way for the Perl internal functions to be
ee072b34
GS
1537C++ methods, subroutines taking some kind of structure as the first
1538argument, or subroutines taking nothing as the first argument. To
1539enable these three very different ways of building the interpreter,
1540the Perl source (as it does in so many other situations) makes heavy
1541use of macros and subroutine naming conventions.
1542
54aff467 1543First problem: deciding which functions will be public API functions and
ee072b34 1544which will be private. Those functions whose names begin C<Perl_> are
54aff467
GS
1545public, and those whose names begin C<S_> are private (think "S" for
1546"secret" or "static").
ee072b34
GS
1547
1548Some functions have no prefix (e.g., restore_rsfp in toke.c). These
1549are not parts of the object or pseudo-structure because you need to
1550pass pointers to them to other subroutines.
1551
1552Second problem: there must be a syntax so that the same subroutine
1553declarations and calls can pass a structure as their first argument,
1554or pass nothing. To solve this, the subroutines are named and
1555declared in a particular way. Here's a typical start of a static
1556function used within the Perl guts:
1557
1558 STATIC void
1559 S_incline(pTHX_ char *s)
1560
1561STATIC becomes "static" in C, and is #define'd to nothing in C++.
1562
1563A public function (i.e. part of the API) begins like this:
1564
1565 void
1566 Perl_sv_setsv(pTHX_ SV* dsv, SV* ssv)
1567
1568C<pTHX_> is one of a number of macros (in perl.h) that hide the
1569details of the interpreter's context. THX stands for "thread", "this",
1570or "thingy", as the case may be. (And no, George Lucas is not involved. :-)
1571The first character could be 'p' for a B<p>rototype, 'a' for B<a>rgument,
1572or 'd' for B<d>eclaration.
1573
1574When Perl is built without PERL_IMPLICIT_CONTEXT, there is no first
1575argument containing the interpreter's context. The trailing underscore
1576in the pTHX_ macro indicates that the macro expansion needs a comma
1577after the context argument because other arguments follow it. If
1578PERL_IMPLICIT_CONTEXT is not defined, pTHX_ will be ignored, and the
54aff467
GS
1579subroutine is not prototyped to take the extra argument. The form of the
1580macro without the trailing underscore is used when there are no additional
ee072b34
GS
1581explicit arguments.
1582
54aff467 1583When a core function calls another, it must pass the context. This
ee072b34
GS
1584is normally hidden via macros. Consider C<sv_setsv>. It expands
1585something like this:
1586
1587 ifdef PERL_IMPLICIT_CONTEXT
1588 define sv_setsv(a,b) Perl_sv_setsv(aTHX_ a, b)
1589 /* can't do this for vararg functions, see below */
1590 else
1591 define sv_setsv Perl_sv_setsv
1592 endif
1593
1594This works well, and means that XS authors can gleefully write:
1595
1596 sv_setsv(foo, bar);
1597
1598and still have it work under all the modes Perl could have been
1599compiled with.
1600
1601Under PERL_OBJECT in the core, that will translate to either:
1602
1603 CPerlObj::Perl_sv_setsv(foo,bar); # in CPerlObj functions,
1604 # C++ takes care of 'this'
1605 or
1606
1607 pPerl->Perl_sv_setsv(foo,bar); # in truly static functions,
1608 # see objXSUB.h
1609
1610Under PERL_OBJECT in extensions (aka PERL_CAPI), or under
1611MULTIPLICITY/USE_THREADS w/ PERL_IMPLICIT_CONTEXT in both core
1612and extensions, it will be:
1613
1614 Perl_sv_setsv(aTHX_ foo, bar); # the canonical Perl "API"
1615 # for all build flavors
1616
1617This doesn't work so cleanly for varargs functions, though, as macros
1618imply that the number of arguments is known in advance. Instead we
1619either need to spell them out fully, passing C<aTHX_> as the first
1620argument (the Perl core tends to do this with functions like
1621Perl_warner), or use a context-free version.
1622
1623The context-free version of Perl_warner is called
1624Perl_warner_nocontext, and does not take the extra argument. Instead
1625it does dTHX; to get the context from thread-local storage. We
1626C<#define warner Perl_warner_nocontext> so that extensions get source
1627compatibility at the expense of performance. (Passing an arg is
1628cheaper than grabbing it from thread-local storage.)
1629
1630You can ignore [pad]THX[xo] when browsing the Perl headers/sources.
1631Those are strictly for use within the core. Extensions and embedders
1632need only be aware of [pad]THX.
1633
1634=head2 How do I use all this in extensions?
1635
1636When Perl is built with PERL_IMPLICIT_CONTEXT, extensions that call
1637any functions in the Perl API will need to pass the initial context
1638argument somehow. The kicker is that you will need to write it in
1639such a way that the extension still compiles when Perl hasn't been
1640built with PERL_IMPLICIT_CONTEXT enabled.
1641
1642There are three ways to do this. First, the easy but inefficient way,
1643which is also the default, in order to maintain source compatibility
1644with extensions: whenever XSUB.h is #included, it redefines the aTHX
1645and aTHX_ macros to call a function that will return the context.
1646Thus, something like:
1647
1648 sv_setsv(asv, bsv);
1649
54aff467
GS
1650in your extesion will translate to this when PERL_IMPLICIT_CONTEXT is
1651in effect:
ee072b34
GS
1652
1653 Perl_sv_setsv(GetPerlInterpreter(), asv, bsv);
1654
54aff467 1655or to this otherwise:
ee072b34
GS
1656
1657 Perl_sv_setsv(asv, bsv);
1658
1659You have to do nothing new in your extension to get this; since
1660the Perl library provides GetPerlInterpreter(), it will all just
1661work.
1662
1663The second, more efficient way is to use the following template for
1664your Foo.xs:
1665
1666 #define PERL_NO_GET_CONTEXT /* we want efficiency */
1667 #include "EXTERN.h"
1668 #include "perl.h"
1669 #include "XSUB.h"
1670
1671 static my_private_function(int arg1, int arg2);
1672
1673 static SV *
54aff467 1674 my_private_function(int arg1, int arg2)
ee072b34
GS
1675 {
1676 dTHX; /* fetch context */
1677 ... call many Perl API functions ...
1678 }
1679
1680 [... etc ...]
1681
1682 MODULE = Foo PACKAGE = Foo
1683
1684 /* typical XSUB */
1685
1686 void
1687 my_xsub(arg)
1688 int arg
1689 CODE:
1690 my_private_function(arg, 10);
1691
1692Note that the only two changes from the normal way of writing an
1693extension is the addition of a C<#define PERL_NO_GET_CONTEXT> before
1694including the Perl headers, followed by a C<dTHX;> declaration at
1695the start of every function that will call the Perl API. (You'll
1696know which functions need this, because the C compiler will complain
1697that there's an undeclared identifier in those functions.) No changes
1698are needed for the XSUBs themselves, because the XS() macro is
1699correctly defined to pass in the implicit context if needed.
1700
1701The third, even more efficient way is to ape how it is done within
1702the Perl guts:
1703
1704
1705 #define PERL_NO_GET_CONTEXT /* we want efficiency */
1706 #include "EXTERN.h"
1707 #include "perl.h"
1708 #include "XSUB.h"
1709
1710 /* pTHX_ only needed for functions that call Perl API */
1711 static my_private_function(pTHX_ int arg1, int arg2);
1712
1713 static SV *
1714 my_private_function(pTHX_ int arg1, int arg2)
1715 {
1716 /* dTHX; not needed here, because THX is an argument */
1717 ... call Perl API functions ...
1718 }
1719
1720 [... etc ...]
1721
1722 MODULE = Foo PACKAGE = Foo
1723
1724 /* typical XSUB */
1725
1726 void
1727 my_xsub(arg)
1728 int arg
1729 CODE:
1730 my_private_function(aTHX_ arg, 10);
1731
1732This implementation never has to fetch the context using a function
1733call, since it is always passed as an extra argument. Depending on
1734your needs for simplicity or efficiency, you may mix the previous
1735two approaches freely.
1736
1737Never say C<pTHX,> yourself--always use the form of the macro with the
1738underscore for functions that take explicit arguments, or the form
1739without the argument for functions with no explicit arguments.
1740
1741=head2 Future Plans and PERL_IMPLICIT_SYS
1742
1743Just as PERL_IMPLICIT_CONTEXT provides a way to bundle up everything
1744that the interpreter knows about itself and pass it around, so too are
1745there plans to allow the interpreter to bundle up everything it knows
1746about the environment it's running on. This is enabled with the
1747PERL_IMPLICIT_SYS macro. Currently it only works with PERL_OBJECT,
1748but is mostly there for MULTIPLICITY and USE_THREADS (see inside
1749iperlsys.h).
1750
1751This allows the ability to provide an extra pointer (called the "host"
1752environment) for all the system calls. This makes it possible for
1753all the system stuff to maintain their own state, broken down into
1754seven C structures. These are thin wrappers around the usual system
1755calls (see win32/perllib.c) for the default perl executable, but for a
1756more ambitious host (like the one that would do fork() emulation) all
1757the extra work needed to pretend that different interpreters are
1758actually different "processes", would be done here.
1759
1760The Perl engine/interpreter and the host are orthogonal entities.
1761There could be one or more interpreters in a process, and one or
1762more "hosts", with free association between them.
1763
0a753a76 1764=head1 API LISTING
a0d0e21e 1765
cb1a09d0
AD
1766This is a listing of functions, macros, flags, and variables that may be
1767useful to extension writers or that may be found while reading other
1768extensions.
9cde0e7f
GS
1769
1770Note that all Perl API global variables must be referenced with the C<PL_>
1771prefix. Some macros are provided for compatibility with the older,
ee072b34 1772unadorned names, but this support may be disabled in a future release.
9cde0e7f 1773
e89caa19 1774The sort order of the listing is case insensitive, with any
b5a41e52 1775occurrences of '_' ignored for the purpose of sorting.
a0d0e21e 1776
cb1a09d0 1777=over 8
a0d0e21e 1778
cb1a09d0
AD
1779=item av_clear
1780
0146554f
GA
1781Clears an array, making it empty. Does not free the memory used by the
1782array itself.
cb1a09d0 1783
ef50df4b 1784 void av_clear (AV* ar)
cb1a09d0
AD
1785
1786=item av_extend
1787
1788Pre-extend an array. The C<key> is the index to which the array should be
1789extended.
1790
ef50df4b 1791 void av_extend (AV* ar, I32 key)
cb1a09d0
AD
1792
1793=item av_fetch
1794
1795Returns the SV at the specified index in the array. The C<key> is the
1796index. If C<lval> is set then the fetch will be part of a store. Check
1797that the return value is non-null before dereferencing it to a C<SV*>.
1798
04343c6d
GS
1799See L<Understanding the Magic of Tied Hashes and Arrays> for more
1800information on how to use this function on tied arrays.
1801
ef50df4b 1802 SV** av_fetch (AV* ar, I32 key, I32 lval)
cb1a09d0 1803
e89caa19
GA
1804=item AvFILL
1805
95906810 1806Same as C<av_len()>. Deprecated, use C<av_len()> instead.
e89caa19 1807
cb1a09d0
AD
1808=item av_len
1809
1810Returns the highest index in the array. Returns -1 if the array is empty.
1811
ef50df4b 1812 I32 av_len (AV* ar)
cb1a09d0
AD
1813
1814=item av_make
1815
5fb8527f
PP
1816Creates a new AV and populates it with a list of SVs. The SVs are copied
1817into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1818will have a reference count of 1.
cb1a09d0 1819
ef50df4b 1820 AV* av_make (I32 size, SV** svp)
cb1a09d0
AD
1821
1822=item av_pop
1823
9cde0e7f 1824Pops an SV off the end of the array. Returns C<&PL_sv_undef> if the array is
cb1a09d0
AD
1825empty.
1826
ef50df4b 1827 SV* av_pop (AV* ar)
cb1a09d0
AD
1828
1829=item av_push
1830
5fb8527f
PP
1831Pushes an SV onto the end of the array. The array will grow automatically
1832to accommodate the addition.
cb1a09d0 1833
ef50df4b 1834 void av_push (AV* ar, SV* val)
cb1a09d0
AD
1835
1836=item av_shift
1837
1838Shifts an SV off the beginning of the array.
1839
ef50df4b 1840 SV* av_shift (AV* ar)
cb1a09d0
AD
1841
1842=item av_store
1843
1844Stores an SV in an array. The array index is specified as C<key>. The
04343c6d
GS
1845return value will be NULL if the operation failed or if the value did not
1846need to be actually stored within the array (as in the case of tied arrays).
1847Otherwise it can be dereferenced to get the original C<SV*>. Note that the
1848caller is responsible for suitably incrementing the reference count of C<val>
1849before the call, and decrementing it if the function returned NULL.
1850
1851See L<Understanding the Magic of Tied Hashes and Arrays> for more
1852information on how to use this function on tied arrays.
cb1a09d0 1853
ef50df4b 1854 SV** av_store (AV* ar, I32 key, SV* val)
cb1a09d0
AD
1855
1856=item av_undef
1857
0146554f 1858Undefines the array. Frees the memory used by the array itself.
cb1a09d0 1859
ef50df4b 1860 void av_undef (AV* ar)
cb1a09d0
AD
1861
1862=item av_unshift
1863
0146554f
GA
1864Unshift the given number of C<undef> values onto the beginning of the
1865array. The array will grow automatically to accommodate the addition.
1866You must then use C<av_store> to assign values to these new elements.
cb1a09d0 1867
ef50df4b 1868 void av_unshift (AV* ar, I32 num)
cb1a09d0
AD
1869
1870=item CLASS
1871
1872Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1873constructor. This is always a C<char*>. See C<THIS> and
1874L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1875
1876=item Copy
1877
1878The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1879source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 1880the type. May fail on overlapping copies. See also C<Move>.
cb1a09d0 1881
e89caa19 1882 void Copy( s, d, n, t )
cb1a09d0
AD
1883
1884=item croak
1885
1886This is the XSUB-writer's interface to Perl's C<die> function. Use this
1887function the same way you use the C C<printf> function. See C<warn>.
1888
1889=item CvSTASH
1890
1891Returns the stash of the CV.
1892
e89caa19 1893 HV* CvSTASH( SV* sv )
cb1a09d0 1894
9cde0e7f 1895=item PL_DBsingle
cb1a09d0
AD
1896
1897When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1898boolean which indicates whether subs are being single-stepped.
5fb8527f 1899Single-stepping is automatically turned on after every step. This is the C
9cde0e7f 1900variable which corresponds to Perl's $DB::single variable. See C<PL_DBsub>.
cb1a09d0 1901
9cde0e7f 1902=item PL_DBsub
cb1a09d0
AD
1903
1904When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f 1905the SV which holds the name of the sub being debugged. This is the C
9cde0e7f 1906variable which corresponds to Perl's $DB::sub variable. See C<PL_DBsingle>.
cb1a09d0
AD
1907The sub name can be found by
1908
2d8e6c8d 1909 SvPV( GvSV( PL_DBsub ), len )
cb1a09d0 1910
9cde0e7f 1911=item PL_DBtrace
5fb8527f
PP
1912
1913Trace variable used when Perl is run in debugging mode, with the B<-d>
1914switch. This is the C variable which corresponds to Perl's $DB::trace
9cde0e7f 1915variable. See C<PL_DBsingle>.
5fb8527f 1916
cb1a09d0
AD
1917=item dMARK
1918
5fb8527f
PP
1919Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1920C<dORIGMARK>.
cb1a09d0
AD
1921
1922=item dORIGMARK
1923
1924Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1925
9cde0e7f 1926=item PL_dowarn
5fb8527f
PP
1927
1928The C variable which corresponds to Perl's $^W warning variable.
1929
cb1a09d0
AD
1930=item dSP
1931
924508f0
GS
1932Declares a local copy of perl's stack pointer for the XSUB, available via
1933the C<SP> macro. See C<SP>.
cb1a09d0
AD
1934
1935=item dXSARGS
1936
1937Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1938usually handled automatically by C<xsubpp>. Declares the C<items> variable
1939to indicate the number of items on the stack.
1940
5fb8527f
PP
1941=item dXSI32
1942
1943Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1944handled automatically by C<xsubpp>.
1945
491527d0
GS
1946=item do_binmode
1947
1948Switches filehandle to binmode. C<iotype> is what C<IoTYPE(io)> would
1949contain.
1950
1951 do_binmode(fp, iotype, TRUE);
1952
cb1a09d0
AD
1953=item ENTER
1954
1955Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1956
1957 ENTER;
1958
1959=item EXTEND
1960
1961Used to extend the argument stack for an XSUB's return values.
1962
ef50df4b 1963 EXTEND( sp, int x )
cb1a09d0 1964
e89caa19
GA
1965=item fbm_compile
1966
1967Analyses the string in order to make fast searches on it using fbm_instr() --
1968the Boyer-Moore algorithm.
1969
411d5715 1970 void fbm_compile(SV* sv, U32 flags)
e89caa19
GA
1971
1972=item fbm_instr
1973
1974Returns the location of the SV in the string delimited by C<str> and
1975C<strend>. It returns C<Nullch> if the string can't be found. The
1976C<sv> does not have to be fbm_compiled, but the search will not be as
1977fast then.
1978
411d5715 1979 char* fbm_instr(char *str, char *strend, SV *sv, U32 flags)
e89caa19 1980
cb1a09d0
AD
1981=item FREETMPS
1982
1983Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1984L<perlcall>.
1985
1986 FREETMPS;
1987
1988=item G_ARRAY
1989
54310121 1990Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
cb1a09d0
AD
1991
1992=item G_DISCARD
1993
1994Indicates that arguments returned from a callback should be discarded. See
1995L<perlcall>.
1996
1997=item G_EVAL
1998
1999Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
2000
2001=item GIMME
2002
54310121
PP
2003A backward-compatible version of C<GIMME_V> which can only return
2004C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
2005
2006=item GIMME_V
2007
2008The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
2009C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
2010context, respectively.
cb1a09d0
AD
2011
2012=item G_NOARGS
2013
2014Indicates that no arguments are being sent to a callback. See L<perlcall>.
2015
2016=item G_SCALAR
2017
54310121
PP
2018Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
2019
faed5253
JO
2020=item gv_fetchmeth
2021
2022Returns the glob with the given C<name> and a defined subroutine or
9607fc9c 2023C<NULL>. The glob lives in the given C<stash>, or in the stashes
f86cebdf 2024accessible via @ISA and @UNIVERSAL.
faed5253 2025
9607fc9c 2026The argument C<level> should be either 0 or -1. If C<level==0>, as a
0a753a76
PP
2027side-effect creates a glob with the given C<name> in the given
2028C<stash> which in the case of success contains an alias for the
2029subroutine, and sets up caching info for this glob. Similarly for all
2030the searched stashes.
2031
9607fc9c
PP
2032This function grants C<"SUPER"> token as a postfix of the stash name.
2033
0a753a76
PP
2034The GV returned from C<gv_fetchmeth> may be a method cache entry,
2035which is not visible to Perl code. So when calling C<perl_call_sv>,
2036you should not use the GV directly; instead, you should use the
2037method's CV, which can be obtained from the GV with the C<GvCV> macro.
faed5253 2038
08105a92 2039 GV* gv_fetchmeth (HV* stash, const char* name, STRLEN len, I32 level)
faed5253
JO
2040
2041=item gv_fetchmethod
2042
dc848c6f
PP
2043=item gv_fetchmethod_autoload
2044
faed5253 2045Returns the glob which contains the subroutine to call to invoke the
c2611fb3 2046method on the C<stash>. In fact in the presence of autoloading this may
dc848c6f 2047be the glob for "AUTOLOAD". In this case the corresponding variable
faed5253
JO
2048$AUTOLOAD is already setup.
2049
dc848c6f
PP
2050The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
2051lookup is performed if the given method is not present: non-zero means
2052yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
2053C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
2054non-zero C<autoload> parameter.
2055
2056These functions grant C<"SUPER"> token as a prefix of the method name.
2057
2058Note that if you want to keep the returned glob for a long time, you
2059need to check for it being "AUTOLOAD", since at the later time the call
faed5253
JO
2060may load a different subroutine due to $AUTOLOAD changing its value.
2061Use the glob created via a side effect to do this.
2062
dc848c6f
PP
2063These functions have the same side-effects and as C<gv_fetchmeth> with
2064C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
0a753a76 2065The warning against passing the GV returned by C<gv_fetchmeth> to
dc848c6f 2066C<perl_call_sv> apply equally to these functions.
faed5253 2067
08105a92
GS
2068 GV* gv_fetchmethod (HV* stash, const char* name)
2069 GV* gv_fetchmethod_autoload (HV* stash, const char* name, I32 autoload)
faed5253 2070
e89caa19
GA
2071=item G_VOID
2072
2073Used to indicate void context. See C<GIMME_V> and L<perlcall>.
2074
cb1a09d0
AD
2075=item gv_stashpv
2076
2077Returns a pointer to the stash for a specified package. If C<create> is set
2078then the package will be created if it does not already exist. If C<create>
2079is not set and the package does not exist then NULL is returned.
2080
08105a92 2081 HV* gv_stashpv (const char* name, I32 create)
cb1a09d0
AD
2082
2083=item gv_stashsv
2084
2085Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
2086
ef50df4b 2087 HV* gv_stashsv (SV* sv, I32 create)
cb1a09d0 2088
e5581bf4 2089=item GvSV
cb1a09d0 2090
e5581bf4 2091Return the SV from the GV.
44a8e56a 2092
1e422769
PP
2093=item HEf_SVKEY
2094
2095This flag, used in the length slot of hash entries and magic
2096structures, specifies the structure contains a C<SV*> pointer where a
2097C<char*> pointer is to be expected. (For information only--not to be used).
2098
1e422769
PP
2099=item HeHASH
2100
e89caa19 2101Returns the computed hash stored in the hash entry.
1e422769 2102
e89caa19 2103 U32 HeHASH(HE* he)
1e422769
PP
2104
2105=item HeKEY
2106
2107Returns the actual pointer stored in the key slot of the hash entry.
2108The pointer may be either C<char*> or C<SV*>, depending on the value of
2109C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
2110are usually preferable for finding the value of a key.
2111
e89caa19 2112 char* HeKEY(HE* he)
1e422769
PP
2113
2114=item HeKLEN
2115
2116If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
2117holds an C<SV*> key. Otherwise, holds the actual length of the key.
2118Can be assigned to. The C<HePV()> macro is usually preferable for finding
2119key lengths.
2120
e89caa19 2121 int HeKLEN(HE* he)
1e422769
PP
2122
2123=item HePV
2124
2125Returns the key slot of the hash entry as a C<char*> value, doing any
2126necessary dereferencing of possibly C<SV*> keys. The length of
2127the string is placed in C<len> (this is a macro, so do I<not> use
2128C<&len>). If you do not care about what the length of the key is,
2d8e6c8d
GS
2129you may use the global variable C<PL_na>, though this is rather less
2130efficient than using a local variable. Remember though, that hash
1e422769
PP
2131keys in perl are free to contain embedded nulls, so using C<strlen()>
2132or similar is not a good way to find the length of hash keys.
2133This is very similar to the C<SvPV()> macro described elsewhere in
2134this document.
2135
e89caa19 2136 char* HePV(HE* he, STRLEN len)
1e422769
PP
2137
2138=item HeSVKEY
2139
2140Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
2141does not contain an C<SV*> key.
2142
2143 HeSVKEY(HE* he)
2144
2145=item HeSVKEY_force
2146
2147Returns the key as an C<SV*>. Will create and return a temporary
2148mortal C<SV*> if the hash entry contains only a C<char*> key.
2149
2150 HeSVKEY_force(HE* he)
2151
2152=item HeSVKEY_set
2153
2154Sets the key to a given C<SV*>, taking care to set the appropriate flags
2155to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
2156
2157 HeSVKEY_set(HE* he, SV* sv)
2158
2159=item HeVAL
2160
2161Returns the value slot (type C<SV*>) stored in the hash entry.
2162
2163 HeVAL(HE* he)
2164
cb1a09d0
AD
2165=item hv_clear
2166
2167Clears a hash, making it empty.
2168
ef50df4b 2169 void hv_clear (HV* tb)
cb1a09d0
AD
2170
2171=item hv_delete
2172
2173Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 2174and returned to the caller. The C<klen> is the length of the key. The
04343c6d 2175C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
cb1a09d0
AD
2176returned.
2177
08105a92 2178 SV* hv_delete (HV* tb, const char* key, U32 klen, I32 flags)
cb1a09d0 2179
1e422769
PP
2180=item hv_delete_ent
2181
2182Deletes a key/value pair in the hash. The value SV is removed from the hash
2183and returned to the caller. The C<flags> value will normally be zero; if set
04343c6d 2184to G_DISCARD then NULL will be returned. C<hash> can be a valid precomputed
1e422769
PP
2185hash value, or 0 to ask for it to be computed.
2186
ef50df4b 2187 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash)
1e422769 2188
cb1a09d0
AD
2189=item hv_exists
2190
2191Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 2192C<klen> is the length of the key.
cb1a09d0 2193
08105a92 2194 bool hv_exists (HV* tb, const char* key, U32 klen)
cb1a09d0 2195
1e422769
PP
2196=item hv_exists_ent
2197
2198Returns a boolean indicating whether the specified hash key exists. C<hash>
54310121 2199can be a valid precomputed hash value, or 0 to ask for it to be computed.
1e422769 2200
ef50df4b 2201 bool hv_exists_ent (HV* tb, SV* key, U32 hash)
1e422769 2202
cb1a09d0
AD
2203=item hv_fetch
2204
2205Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 2206C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
2207part of a store. Check that the return value is non-null before
2208dereferencing it to a C<SV*>.
2209
04343c6d
GS
2210See L<Understanding the Magic of Tied Hashes and Arrays> for more
2211information on how to use this function on tied hashes.
2212
08105a92 2213 SV** hv_fetch (HV* tb, const char* key, U32 klen, I32 lval)
cb1a09d0 2214
1e422769
PP
2215=item hv_fetch_ent
2216
2217Returns the hash entry which corresponds to the specified key in the hash.
54310121 2218C<hash> must be a valid precomputed hash number for the given C<key>, or
1e422769
PP
22190 if you want the function to compute it. IF C<lval> is set then the
2220fetch will be part of a store. Make sure the return value is non-null
2221before accessing it. The return value when C<tb> is a tied hash
2222is a pointer to a static location, so be sure to make a copy of the
2223structure if you need to store it somewhere.
2224
04343c6d
GS
2225See L<Understanding the Magic of Tied Hashes and Arrays> for more
2226information on how to use this function on tied hashes.
2227
ef50df4b 2228 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash)
1e422769 2229
cb1a09d0
AD
2230=item hv_iterinit
2231
2232Prepares a starting point to traverse a hash table.
2233
ef50df4b 2234 I32 hv_iterinit (HV* tb)
cb1a09d0 2235
c6601927
SI
2236Returns the number of keys in the hash (i.e. the same as C<HvKEYS(tb)>).
2237The return value is currently only meaningful for hashes without tie
2238magic.
2239
2240NOTE: Before version 5.004_65, C<hv_iterinit> used to return the number
2241of hash buckets that happen to be in use. If you still need that
2242esoteric value, you can get it through the macro C<HvFILL(tb)>.
fb73857a 2243
cb1a09d0
AD
2244=item hv_iterkey
2245
2246Returns the key from the current position of the hash iterator. See
2247C<hv_iterinit>.
2248
ef50df4b 2249 char* hv_iterkey (HE* entry, I32* retlen)
cb1a09d0 2250
1e422769 2251=item hv_iterkeysv
3fe9a6f1 2252
1e422769
PP
2253Returns the key as an C<SV*> from the current position of the hash
2254iterator. The return value will always be a mortal copy of the
2255key. Also see C<hv_iterinit>.
2256
ef50df4b 2257 SV* hv_iterkeysv (HE* entry)
1e422769 2258
cb1a09d0
AD
2259=item hv_iternext
2260
2261Returns entries from a hash iterator. See C<hv_iterinit>.
2262
ef50df4b 2263 HE* hv_iternext (HV* tb)
cb1a09d0
AD
2264
2265=item hv_iternextsv
2266
2267Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
2268operation.
2269
e89caa19 2270 SV* hv_iternextsv (HV* hv, char** key, I32* retlen)
cb1a09d0
AD
2271
2272=item hv_iterval
2273
2274Returns the value from the current position of the hash iterator. See
2275C<hv_iterkey>.
2276
ef50df4b 2277 SV* hv_iterval (HV* tb, HE* entry)
cb1a09d0
AD
2278
2279=item hv_magic
2280
2281Adds magic to a hash. See C<sv_magic>.
2282
ef50df4b 2283 void hv_magic (HV* hv, GV* gv, int how)
cb1a09d0
AD
2284
2285=item HvNAME
2286
2287Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
2288
e89caa19 2289 char* HvNAME (HV* stash)
cb1a09d0
AD
2290
2291=item hv_store
2292
2293Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
54310121 2294the length of the key. The C<hash> parameter is the precomputed hash
cb1a09d0 2295value; if it is zero then Perl will compute it. The return value will be
04343c6d
GS
2296NULL if the operation failed or if the value did not need to be actually
2297stored within the hash (as in the case of tied hashes). Otherwise it can
2298be dereferenced to get the original C<SV*>. Note that the caller is
2299responsible for suitably incrementing the reference count of C<val>
2300before the call, and decrementing it if the function returned NULL.
2301
2302See L<Understanding the Magic of Tied Hashes and Arrays> for more
2303information on how to use this function on tied hashes.
cb1a09d0 2304
08105a92 2305 SV** hv_store (HV* tb, const char* key, U32 klen, SV* val, U32 hash)
cb1a09d0 2306
1e422769
PP
2307=item hv_store_ent
2308
2309Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
54310121 2310parameter is the precomputed hash value; if it is zero then Perl will
1e422769 2311compute it. The return value is the new hash entry so created. It will be
04343c6d
GS
2312NULL if the operation failed or if the value did not need to be actually
2313stored within the hash (as in the case of tied hashes). Otherwise the
2314contents of the return value can be accessed using the C<He???> macros
2315described here. Note that the caller is responsible for suitably
2316incrementing the reference count of C<val> before the call, and decrementing
2317it if the function returned NULL.
2318
2319See L<Understanding the Magic of Tied Hashes and Arrays> for more
2320information on how to use this function on tied hashes.
1e422769 2321
ef50df4b 2322 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash)
1e422769 2323
cb1a09d0
AD
2324=item hv_undef
2325
2326Undefines the hash.
2327
ef50df4b 2328 void hv_undef (HV* tb)
cb1a09d0
AD
2329
2330=item isALNUM
2331
2332Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 2333character or digit.
cb1a09d0 2334
e89caa19 2335 int isALNUM (char c)
cb1a09d0
AD
2336
2337=item isALPHA
2338
5fb8527f 2339Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
2340character.
2341
e89caa19 2342 int isALPHA (char c)
cb1a09d0
AD
2343
2344=item isDIGIT
2345
2346Returns a boolean indicating whether the C C<char> is an ascii digit.
2347
e89caa19 2348 int isDIGIT (char c)
cb1a09d0
AD
2349
2350=item isLOWER
2351
2352Returns a boolean indicating whether the C C<char> is a lowercase character.
2353
e89caa19 2354 int isLOWER (char c)
cb1a09d0
AD
2355
2356=item isSPACE
2357
2358Returns a boolean indicating whether the C C<char> is whitespace.
2359
e89caa19 2360 int isSPACE (char c)
cb1a09d0
AD
2361
2362=item isUPPER
2363
2364Returns a boolean indicating whether the C C<char> is an uppercase character.
2365
e89caa19 2366 int isUPPER (char c)
cb1a09d0
AD
2367
2368=item items
2369
2370Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
2371stack. See L<perlxs/"Variable-length Parameter Lists">.
2372
2373=item ix
2374
2375Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
2376was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
2377
2378=item LEAVE
2379
2380Closing bracket on a callback. See C<ENTER> and L<perlcall>.
2381
2382 LEAVE;
2383
e89caa19
GA
2384=item looks_like_number
2385
2386Test if an the content of an SV looks like a number (or is a number).
2387
2388 int looks_like_number(SV*)
2389
2390
cb1a09d0
AD
2391=item MARK
2392
5fb8527f 2393Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
2394
2395=item mg_clear
2396
2397Clear something magical that the SV represents. See C<sv_magic>.
2398
ef50df4b 2399 int mg_clear (SV* sv)
cb1a09d0
AD
2400
2401=item mg_copy
2402
2403Copies the magic from one SV to another. See C<sv_magic>.
2404
08105a92 2405 int mg_copy (SV *, SV *, const char *, STRLEN)
cb1a09d0
AD
2406
2407=item mg_find
2408
2409Finds the magic pointer for type matching the SV. See C<sv_magic>.
2410
ef50df4b 2411 MAGIC* mg_find (SV* sv, int type)
cb1a09d0
AD
2412
2413=item mg_free
2414
2415Free any magic storage used by the SV. See C<sv_magic>.
2416
ef50df4b 2417 int mg_free (SV* sv)
cb1a09d0
AD
2418
2419=item mg_get
2420
2421Do magic after a value is retrieved from the SV. See C<sv_magic>.
2422
ef50df4b 2423 int mg_get (SV* sv)
cb1a09d0
AD
2424
2425=item mg_len
2426
2427Report on the SV's length. See C<sv_magic>.
2428
ef50df4b 2429 U32 mg_len (SV* sv)
cb1a09d0
AD
2430
2431=item mg_magical
2432
2433Turns on the magical status of an SV. See C<sv_magic>.
2434
ef50df4b 2435 void mg_magical (SV* sv)
cb1a09d0
AD
2436
2437=item mg_set
2438
2439Do magic after a value is assigned to the SV. See C<sv_magic>.
2440
ef50df4b 2441 int mg_set (SV* sv)
cb1a09d0 2442
b0fffe30
JP
2443=item modglobal
2444
2445C<modglobal> is a general purpose, interpreter global HV for use by
db696efe
GS
2446extensions that need to keep information on a per-interpreter basis.
2447In a pinch, it can also be used as a symbol table for extensions
2448to share data among each other. It is a good idea to use keys
2449prefixed by the package name of the extension that owns the data.
b0fffe30 2450
cb1a09d0
AD
2451=item Move
2452
2453The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
2454source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 2455the type. Can do overlapping moves. See also C<Copy>.
cb1a09d0 2456
e89caa19 2457 void Move( s, d, n, t )
cb1a09d0 2458
9cde0e7f 2459=item PL_na
cb1a09d0 2460
2d8e6c8d
GS
2461A convenience variable which is typically used with C<SvPV> when one doesn't
2462care about the length of the string. It is usually more efficient to
1fa8b10d
JD
2463either declare a local variable and use that instead or to use the C<SvPV_nolen>
2464macro.
cb1a09d0
AD
2465
2466=item New
2467
2468The XSUB-writer's interface to the C C<malloc> function.
2469
e89caa19 2470 void* New( x, void *ptr, int size, type )
cb1a09d0
AD
2471
2472=item newAV
2473
5f05dabc 2474Creates a new AV. The reference count is set to 1.
cb1a09d0 2475
ef50df4b 2476 AV* newAV (void)
cb1a09d0 2477
e89caa19
GA
2478=item Newc
2479
2480The XSUB-writer's interface to the C C<malloc> function, with cast.
2481
2482 void* Newc( x, void *ptr, int size, type, cast )
2483
5476c433
JD
2484=item newCONSTSUB
2485
2486Creates a constant sub equivalent to Perl C<sub FOO () { 123 }>
2487which is eligible for inlining at compile-time.
2488
2489 void newCONSTSUB(HV* stash, char* name, SV* sv)
2490
cb1a09d0
AD
2491=item newHV
2492
5f05dabc 2493Creates a new HV. The reference count is set to 1.
cb1a09d0 2494
ef50df4b 2495 HV* newHV (void)
cb1a09d0 2496
5f05dabc 2497=item newRV_inc
cb1a09d0 2498
5f05dabc 2499Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
2500incremented.
2501
ef50df4b 2502 SV* newRV_inc (SV* ref)
5f05dabc
PP
2503
2504For historical reasons, "newRV" is a synonym for "newRV_inc".
2505
2506=item newRV_noinc
2507
2508Creates an RV wrapper for an SV. The reference count for the original
2509SV is B<not> incremented.
2510
ef50df4b 2511 SV* newRV_noinc (SV* ref)
cb1a09d0 2512
8c52afec 2513=item NEWSV
cb1a09d0 2514
e89caa19
GA
2515Creates a new SV. A non-zero C<len> parameter indicates the number of
2516bytes of preallocated string space the SV should have. An extra byte
2517for a tailing NUL is also reserved. (SvPOK is not set for the SV even
2518if string space is allocated.) The reference count for the new SV is
2519set to 1. C<id> is an integer id between 0 and 1299 (used to identify
2520leaks).
cb1a09d0 2521
ef50df4b 2522 SV* NEWSV (int id, STRLEN len)
cb1a09d0
AD
2523
2524=item newSViv
2525
07fa94a1
JO
2526Creates a new SV and copies an integer into it. The reference count for the
2527SV is set to 1.
cb1a09d0 2528
ef50df4b 2529 SV* newSViv (IV i)
cb1a09d0
AD
2530
2531=item newSVnv
2532
07fa94a1
JO
2533Creates a new SV and copies a double into it. The reference count for the
2534SV is set to 1.
cb1a09d0 2535
ef50df4b 2536 SV* newSVnv (NV i)
cb1a09d0
AD
2537
2538=item newSVpv
2539
07fa94a1 2540Creates a new SV and copies a string into it. The reference count for the
79cb57f6
GS
2541SV is set to 1. If C<len> is zero, Perl will compute the length using
2542strlen(). For efficiency, consider using C<newSVpvn> instead.
cb1a09d0 2543
08105a92 2544 SV* newSVpv (const char* s, STRLEN len)
cb1a09d0 2545
e89caa19
GA
2546=item newSVpvf
2547
2548Creates a new SV an initialize it with the string formatted like
2549C<sprintf>.
2550
79cb57f6 2551 SV* newSVpvf(const char* pat, ...)
e89caa19 2552
9da1e3b5
MUN
2553=item newSVpvn
2554
2555Creates a new SV and copies a string into it. The reference count for the
79cb57f6
GS
2556SV is set to 1. Note that if C<len> is zero, Perl will create a zero length
2557string. You are responsible for ensuring that the source string is at least
2558C<len> bytes long.
9da1e3b5 2559
08105a92 2560 SV* newSVpvn (const char* s, STRLEN len)
9da1e3b5 2561
cb1a09d0
AD
2562=item newSVrv
2563
2564Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 2565it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 2566be blessed in the specified package. The new SV is returned and its
5f05dabc 2567reference count is 1.
8ebc5c01 2568
08105a92 2569 SV* newSVrv (SV* rv, const char* classname)
cb1a09d0
AD
2570
2571=item newSVsv
2572
5fb8527f 2573Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0 2574
ef50df4b 2575 SV* newSVsv (SV* old)
cb1a09d0
AD
2576
2577=item newXS
2578
2579Used by C<xsubpp> to hook up XSUBs as Perl subs.
2580
2581=item newXSproto
2582
2583Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
2584the subs.
2585
e89caa19
GA
2586=item Newz
2587
2588The XSUB-writer's interface to the C C<malloc> function. The allocated
2589memory is zeroed with C<memzero>.
2590
2591 void* Newz( x, void *ptr, int size, type )
2592
cb1a09d0
AD
2593=item Nullav
2594
2595Null AV pointer.
2596
2597=item Nullch
2598
2599Null character pointer.
2600
2601=item Nullcv
2602
2603Null CV pointer.
2604
2605=item Nullhv
2606
2607Null HV pointer.
2608
2609=item Nullsv
2610
2611Null SV pointer.
2612
2613=item ORIGMARK
2614
2615The original stack mark for the XSUB. See C<dORIGMARK>.
2616
2617=item perl_alloc
2618
2619Allocates a new Perl interpreter. See L<perlembed>.
2620
2621=item perl_call_argv
2622
2623Performs a callback to the specified Perl sub. See L<perlcall>.
2624
08105a92 2625 I32 perl_call_argv (const char* subname, I32 flags, char** argv)
cb1a09d0
AD
2626
2627=item perl_call_method
2628
2629Performs a callback to the specified Perl method. The blessed object must
2630be on the stack. See L<perlcall>.
2631
08105a92 2632 I32 perl_call_method (const char* methname, I32 flags)
cb1a09d0
AD
2633
2634=item perl_call_pv
2635
2636Performs a callback to the specified Perl sub. See L<perlcall>.
2637
08105a92 2638 I32 perl_call_pv (const char* subname, I32 flags)
cb1a09d0
AD
2639
2640=item perl_call_sv
2641
2642Performs a callback to the Perl sub whose name is in the SV. See
2643L<perlcall>.
2644
ef50df4b 2645 I32 perl_call_sv (SV* sv, I32 flags)
cb1a09d0
AD
2646
2647=item perl_construct
2648
2649Initializes a new Perl interpreter. See L<perlembed>.
2650
2651=item perl_destruct
2652
2653Shuts down a Perl interpreter. See L<perlembed>.
2654
2655=item perl_eval_sv
2656
2657Tells Perl to C<eval> the string in the SV.
2658
ef50df4b 2659 I32 perl_eval_sv (SV* sv, I32 flags)
cb1a09d0 2660
137443ea
PP
2661=item perl_eval_pv
2662
2663Tells Perl to C<eval> the given string and return an SV* result.
2664
08105a92 2665 SV* perl_eval_pv (const char* p, I32 croak_on_error)
137443ea 2666
cb1a09d0
AD
2667=item perl_free
2668
2669Releases a Perl interpreter. See L<perlembed>.
2670
2671=item perl_get_av
2672
2673Returns the AV of the specified Perl array. If C<create> is set and the
2674Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2675set and the variable does not exist then NULL is returned.
cb1a09d0 2676
08105a92 2677 AV* perl_get_av (const char* name, I32 create)
cb1a09d0
AD
2678
2679=item perl_get_cv
2680
f6ec51f7
GS
2681Returns the CV of the specified Perl subroutine. If C<create> is set and
2682the Perl subroutine does not exist then it will be declared (which has
2683the same effect as saying C<sub name;>). If C<create> is not
2684set and the subroutine does not exist then NULL is returned.
cb1a09d0 2685
08105a92 2686 CV* perl_get_cv (const char* name, I32 create)
cb1a09d0
AD
2687
2688=item perl_get_hv
2689
2690Returns the HV of the specified Perl hash. If C<create> is set and the Perl
2691variable does not exist then it will be created. If C<create> is not
04343c6d 2692set and the variable does not exist then NULL is returned.
cb1a09d0 2693
08105a92 2694 HV* perl_get_hv (const char* name, I32 create)
cb1a09d0
AD
2695
2696=item perl_get_sv
2697
2698Returns the SV of the specified Perl scalar. If C<create> is set and the
2699Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2700set and the variable does not exist then NULL is returned.
cb1a09d0 2701
08105a92 2702 SV* perl_get_sv (const char* name, I32 create)
cb1a09d0
AD
2703
2704=item perl_parse
2705
2706Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2707
2708=item perl_require_pv
2709
2710Tells Perl to C<require> a module.
2711
08105a92 2712 void perl_require_pv (const char* pv)
cb1a09d0
AD
2713
2714=item perl_run
2715
2716Tells a Perl interpreter to run. See L<perlembed>.
2717
2718=item POPi
2719
2720Pops an integer off the stack.
2721
e89caa19 2722 int POPi()
cb1a09d0
AD
2723
2724=item POPl
2725
2726Pops a long off the stack.
2727
e89caa19 2728 long POPl()
cb1a09d0
AD
2729
2730=item POPp
2731
2732Pops a string off the stack.
2733
e89caa19 2734 char* POPp()
cb1a09d0
AD
2735
2736=item POPn
2737
2738Pops a double off the stack.
2739
e89caa19 2740 double POPn()
cb1a09d0
AD
2741
2742=item POPs
2743
2744Pops an SV off the stack.
2745
e89caa19 2746 SV* POPs()
cb1a09d0
AD
2747
2748=item PUSHMARK
2749
2750Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2751
2752 PUSHMARK(p)
2753
2754=item PUSHi
2755
2756Push an integer onto the stack. The stack must have room for this element.
189b2af5 2757Handles 'set' magic. See C<XPUSHi>.
cb1a09d0 2758
e89caa19 2759 void PUSHi(int d)
cb1a09d0
AD
2760
2761=item PUSHn
2762
2763Push a double onto the stack. The stack must have room for this element.
189b2af5 2764Handles 'set' magic. See C<XPUSHn>.
cb1a09d0 2765
e89caa19 2766 void PUSHn(double d)
cb1a09d0
AD
2767
2768=item PUSHp
2769
2770Push a string onto the stack. The stack must have room for this element.
189b2af5
GS
2771The C<len> indicates the length of the string. Handles 'set' magic. See
2772C<XPUSHp>.
cb1a09d0 2773
e89caa19 2774 void PUSHp(char *c, int len )
cb1a09d0
AD
2775
2776=item PUSHs
2777
189b2af5
GS
2778Push an SV onto the stack. The stack must have room for this element. Does
2779not handle 'set' magic. See C<XPUSHs>.
cb1a09d0 2780
e89caa19
GA
2781 void PUSHs(sv)
2782
2783=item PUSHu
2784
2785Push an unsigned integer onto the stack. The stack must have room for
2786this element. See C<XPUSHu>.
2787
2788 void PUSHu(unsigned int d)
2789
cb1a09d0
AD
2790
2791=item PUTBACK
2792
2793Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2794See C<PUSHMARK> and L<perlcall> for other uses.
2795
2796 PUTBACK;
2797
2798=item Renew
2799
2800The XSUB-writer's interface to the C C<realloc> function.
2801
e89caa19 2802 void* Renew( void *ptr, int size, type )
cb1a09d0
AD
2803
2804=item Renewc
2805
2806The XSUB-writer's interface to the C C<realloc> function, with cast.
2807
e89caa19 2808 void* Renewc( void *ptr, int size, type, cast )
cb1a09d0
AD
2809
2810=item RETVAL
2811
2812Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
2813This is always the proper type for the XSUB.
2814See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
2815
2816=item safefree
2817
2818The XSUB-writer's interface to the C C<free> function.
2819
2820=item safemalloc
2821
2822The XSUB-writer's interface to the C C<malloc> function.
2823
2824=item saferealloc
2825
2826The XSUB-writer's interface to the C C<realloc> function.
2827
2828=item savepv
2829
2830Copy a string to a safe spot. This does not use an SV.
2831
08105a92 2832 char* savepv (const char* sv)
cb1a09d0
AD
2833
2834=item savepvn
2835
2836Copy a string to a safe spot. The C<len> indicates number of bytes to
2837copy. This does not use an SV.
2838
08105a92 2839 char* savepvn (const char* sv, I32 len)
cb1a09d0
AD
2840
2841=item SAVETMPS
2842
2843Opening bracket for temporaries on a callback. See C<FREETMPS> and
2844L<perlcall>.
2845
2846 SAVETMPS;
2847
2848=item SP
2849
2850Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2851C<SPAGAIN>.
2852
2853=item SPAGAIN
2854
54310121 2855Refetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
2856
2857 SPAGAIN;
2858
2859=item ST
2860
2861Used to access elements on the XSUB's stack.
2862
e89caa19 2863 SV* ST(int x)
cb1a09d0
AD
2864
2865=item strEQ
2866
2867Test two strings to see if they are equal. Returns true or false.
2868
e89caa19 2869 int strEQ( char *s1, char *s2 )
cb1a09d0
AD
2870
2871=item strGE
2872
2873Test two strings to see if the first, C<s1>, is greater than or equal to the
2874second, C<s2>. Returns true or false.
2875
e89caa19 2876 int strGE( char *s1, char *s2 )
cb1a09d0
AD
2877
2878=item strGT
2879
2880Test two strings to see if the first, C<s1>, is greater than the second,
2881C<s2>. Returns true or false.
2882
e89caa19 2883 int strGT( char *s1, char *s2 )
cb1a09d0
AD
2884
2885=item strLE
2886
2887Test two strings to see if the first, C<s1>, is less than or equal to the
2888second, C<s2>. Returns true or false.
2889
e89caa19 2890 int strLE( char *s1, char *s2 )
cb1a09d0
AD
2891
2892=item strLT
2893
2894Test two strings to see if the first, C<s1>, is less than the second,
2895C<s2>. Returns true or false.
2896
e89caa19 2897 int strLT( char *s1, char *s2 )
cb1a09d0
AD
2898
2899=item strNE
2900
2901Test two strings to see if they are different. Returns true or false.
2902
e89caa19 2903 int strNE( char *s1, char *s2 )
cb1a09d0
AD
2904
2905=item strnEQ
2906
2907Test two strings to see if they are equal. The C<len> parameter indicates
2908the number of bytes to compare. Returns true or false.
2909
e89caa19 2910 int strnEQ( char *s1, char *s2 )
cb1a09d0
AD
2911
2912=item strnNE
2913
2914Test two strings to see if they are different. The C<len> parameter
2915indicates the number of bytes to compare. Returns true or false.
2916
e89caa19 2917 int strnNE( char *s1, char *s2, int len )
cb1a09d0
AD
2918
2919=item sv_2mortal
2920
2921Marks an SV as mortal. The SV will be destroyed when the current context
2922ends.
2923
ef50df4b 2924 SV* sv_2mortal (SV* sv)
cb1a09d0
AD
2925
2926=item sv_bless
2927
2928Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
2929must be designated by its stash (see C<gv_stashpv()>). The reference count
2930of the SV is unaffected.
cb1a09d0 2931
ef50df4b 2932 SV* sv_bless (SV* sv, HV* stash)
cb1a09d0 2933
ef50df4b 2934=item sv_catpv
189b2af5 2935
ef50df4b
GS
2936Concatenates the string onto the end of the string which is in the SV.
2937Handles 'get' magic, but not 'set' magic. See C<sv_catpv_mg>.
189b2af5 2938
08105a92 2939 void sv_catpv (SV* sv, const char* ptr)
189b2af5 2940
ef50df4b 2941=item sv_catpv_mg
cb1a09d0 2942
ef50df4b 2943Like C<sv_catpv>, but also handles 'set' magic.
cb1a09d0 2944
08105a92 2945 void sv_catpvn (SV* sv, const char* ptr)
cb1a09d0
AD
2946
2947=item sv_catpvn
2948
2949Concatenates the string onto the end of the string which is in the SV. The
189b2af5 2950C<len> indicates number of bytes to copy. Handles 'get' magic, but not
ef50df4b 2951'set' magic. See C<sv_catpvn_mg>.
cb1a09d0 2952
08105a92 2953 void sv_catpvn (SV* sv, const char* ptr, STRLEN len)
ef50df4b
GS
2954
2955=item sv_catpvn_mg
2956
2957Like C<sv_catpvn>, but also handles 'set' magic.
2958
08105a92 2959 void sv_catpvn_mg (SV* sv, const char* ptr, STRLEN len)
cb1a09d0 2960
46fc3d4c
PP
2961=item sv_catpvf
2962
2963Processes its arguments like C<sprintf> and appends the formatted output
189b2af5
GS
2964to an SV. Handles 'get' magic, but not 'set' magic. C<SvSETMAGIC()> must
2965typically be called after calling this function to handle 'set' magic.
46fc3d4c 2966
ef50df4b
GS
2967 void sv_catpvf (SV* sv, const char* pat, ...)
2968
2969=item sv_catpvf_mg
2970
2971Like C<sv_catpvf>, but also handles 'set' magic.
2972
2973 void sv_catpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 2974
cb1a09d0
AD
2975=item sv_catsv
2976
5fb8527f 2977Concatenates the string from SV C<ssv> onto the end of the string in SV
ef50df4b
GS
2978C<dsv>. Handles 'get' magic, but not 'set' magic. See C<sv_catsv_mg>.
2979
2980 void sv_catsv (SV* dsv, SV* ssv)
2981
2982=item sv_catsv_mg
cb1a09d0 2983
ef50df4b
GS
2984Like C<sv_catsv>, but also handles 'set' magic.
2985
2986 void sv_catsv_mg (SV* dsv, SV* ssv)
cb1a09d0 2987
e89caa19
GA
2988=item sv_chop
2989
2990Efficient removal of characters from the beginning of the string
2991buffer. SvPOK(sv) must be true and the C<ptr> must be a pointer to
2992somewhere inside the string buffer. The C<ptr> becomes the first
2993character of the adjusted string.
2994
08105a92 2995 void sv_chop(SV* sv, const char *ptr)
e89caa19
GA
2996
2997
5fb8527f
PP
2998=item sv_cmp
2999
3000Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
3001string in C<sv1> is less than, equal to, or greater than the string in
3002C<sv2>.
3003
ef50df4b 3004 I32 sv_cmp (SV* sv1, SV* sv2)
5fb8527f 3005
cb1a09d0
AD
3006=item SvCUR
3007
3008Returns the length of the string which is in the SV. See C<SvLEN>.
3009
e89caa19 3010 int SvCUR (SV* sv)
cb1a09d0
AD
3011
3012=item SvCUR_set
3013
3014Set the length of the string which is in the SV. See C<SvCUR>.
3015
08105a92 3016 void SvCUR_set (SV* sv, int val)
cb1a09d0 3017
5fb8527f
PP
3018=item sv_dec
3019
5f05dabc 3020Auto-decrement of the value in the SV.
5fb8527f 3021
ef50df4b 3022 void sv_dec (SV* sv)
5fb8527f 3023
e89caa19
GA
3024=item sv_derived_from
3025
9abd00ed
GS
3026Returns a boolean indicating whether the SV is derived from the specified
3027class. This is the function that implements C<UNIVERSAL::isa>. It works
3028for class names as well as for objects.
3029
20ce7b12 3030 bool sv_derived_from (SV* sv, const char* name);
9abd00ed 3031
cb1a09d0
AD
3032=item SvEND
3033
3034Returns a pointer to the last character in the string which is in the SV.
3035See C<SvCUR>. Access the character as
3036
e89caa19 3037 char* SvEND(sv)
cb1a09d0 3038
5fb8527f
PP
3039=item sv_eq
3040
3041Returns a boolean indicating whether the strings in the two SVs are
3042identical.
3043
ef50df4b 3044 I32 sv_eq (SV* sv1, SV* sv2)
5fb8527f 3045
189b2af5
GS
3046=item SvGETMAGIC
3047
3048Invokes C<mg_get> on an SV if it has 'get' magic. This macro evaluates
3049its argument more than once.
3050
08105a92 3051 void SvGETMAGIC(SV *sv)
189b2af5 3052
cb1a09d0
AD
3053=item SvGROW
3054
e89caa19
GA
3055Expands the character buffer in the SV so that it has room for the
3056indicated number of bytes (remember to reserve space for an extra
3057trailing NUL character). Calls C<sv_grow> to perform the expansion if
3058necessary. Returns a pointer to the character buffer.
cb1a09d0 3059
08105a92 3060 char* SvGROW(SV* sv, STRLEN len)
cb1a09d0 3061
5fb8527f
PP
3062=item sv_grow
3063
3064Expands the character buffer in the SV. This will use C<sv_unref> and will
3065upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
3066Use C<SvGROW>.
3067
3068=item sv_inc
3069
07fa94a1 3070Auto-increment of the value in the SV.
5fb8527f 3071
ef50df4b 3072 void sv_inc (SV* sv)
5fb8527f 3073
e89caa19
GA
3074=item sv_insert
3075
3076Inserts a string at the specified offset/length within the SV.
3077Similar to the Perl substr() function.
3078
3079 void sv_insert(SV *sv, STRLEN offset, STRLEN len,
3080 char *str, STRLEN strlen)
3081
cb1a09d0
AD
3082=item SvIOK
3083
3084Returns a boolean indicating whether the SV contains an integer.
3085
e89caa19 3086 int SvIOK (SV* SV)
cb1a09d0
AD
3087
3088=item SvIOK_off
3089
3090Unsets the IV status of an SV.
3091
e89caa19 3092 void SvIOK_off (SV* sv)
cb1a09d0
AD
3093
3094=item SvIOK_on
3095
3096Tells an SV that it is an integer.
3097
e89caa19 3098 void SvIOK_on (SV* sv)
cb1a09d0 3099
5fb8527f
PP
3100=item SvIOK_only
3101
3102Tells an SV that it is an integer and disables all other OK bits.
3103
e89caa19 3104 void SvIOK_only (SV* sv)
5fb8527f 3105
cb1a09d0
AD
3106=item SvIOKp
3107
3108Returns a boolean indicating whether the SV contains an integer. Checks the
3109B<private> setting. Use C<SvIOK>.
3110
e89caa19 3111 int SvIOKp (SV* SV)
cb1a09d0
AD
3112
3113=item sv_isa
3114
3115Returns a boolean indicating whether the SV is blessed into the specified
9abd00ed 3116class. This does not check for subtypes; use C<sv_derived_from> to verify
cb1a09d0
AD
3117an inheritance relationship.
3118
ef50df4b 3119 int sv_isa (SV* sv, char* name)
cb1a09d0 3120
cb1a09d0
AD
3121=item sv_isobject
3122
3123Returns a boolean indicating whether the SV is an RV pointing to a blessed
3124object. If the SV is not an RV, or if the object is not blessed, then this
3125will return false.
3126
ef50df4b 3127 int sv_isobject (SV* sv)
cb1a09d0 3128
e89caa19
GA
3129=item SvIV
3130
5c68b227 3131Coerces the given SV to an integer and returns it.
e89caa19 3132
9abd00ed 3133 int SvIV (SV* sv)
a59f3522 3134
cb1a09d0
AD
3135=item SvIVX
3136
5c68b227 3137Returns the integer which is stored in the SV, assuming SvIOK is true.
cb1a09d0 3138
e89caa19 3139 int SvIVX (SV* sv)
cb1a09d0
AD
3140
3141=item SvLEN
3142
3143Returns the size of the string buffer in the SV. See C<SvCUR>.
3144
e89caa19 3145 int SvLEN (SV* sv)
cb1a09d0 3146
5fb8527f
PP
3147=item sv_len
3148
3149Returns the length of the string in the SV. Use C<SvCUR>.
3150
ef50df4b 3151 STRLEN sv_len (SV* sv)
5fb8527f 3152
cb1a09d0
AD
3153=item sv_magic
3154
3155Adds magic to an SV.
3156
08105a92 3157 void sv_magic (SV* sv, SV* obj, int how, const char* name, I32 namlen)
cb1a09d0
AD
3158
3159=item sv_mortalcopy
3160
3161Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 3162as mortal.
cb1a09d0 3163
ef50df4b 3164 SV* sv_mortalcopy (SV* oldsv)
cb1a09d0 3165
cb1a09d0
AD
3166=item sv_newmortal
3167
5f05dabc 3168Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0 3169
ef50df4b 3170 SV* sv_newmortal (void)
cb1a09d0 3171
cb1a09d0
AD
3172=item SvNIOK
3173
3174Returns a boolean indicating whether the SV contains a number, integer or
3175double.
3176
e89caa19 3177 int SvNIOK (SV* SV)
cb1a09d0
AD
3178
3179=item SvNIOK_off
3180
3181Unsets the NV/IV status of an SV.
3182
e89caa19 3183 void SvNIOK_off (SV* sv)
cb1a09d0
AD
3184
3185=item SvNIOKp
3186
3187Returns a boolean indicating whether the SV contains a number, integer or
3188double. Checks the B<private> setting. Use C<SvNIOK>.
3189
e89caa19
GA
3190 int SvNIOKp (SV* SV)
3191
9cde0e7f 3192=item PL_sv_no
e89caa19 3193
9cde0e7f 3194This is the C<false> SV. See C<PL_sv_yes>. Always refer to this as C<&PL_sv_no>.
cb1a09d0
AD
3195
3196=item SvNOK
3197
3198Returns a boolean indicating whether the SV contains a double.
3199
e89caa19 3200 int SvNOK (SV* SV)
cb1a09d0
AD
3201
3202=item SvNOK_off
3203
3204Unsets the NV status of an SV.
3205
e89caa19 3206 void SvNOK_off (SV* sv)
cb1a09d0
AD
3207
3208=item SvNOK_on
3209
3210Tells an SV that it is a double.
3211
e89caa19 3212 void SvNOK_on (SV* sv)
cb1a09d0 3213
5fb8527f
PP
3214=item SvNOK_only
3215
3216Tells an SV that it is a double and disables all other OK bits.
3217
e89caa19 3218 void SvNOK_only (SV* sv)
5fb8527f 3219
cb1a09d0
AD
3220=item SvNOKp
3221
3222Returns a boolean indicating whether the SV contains a double. Checks the
3223B<private> setting. Use C<SvNOK>.
3224
e89caa19 3225 int SvNOKp (SV* SV)
cb1a09d0
AD
3226
3227=item SvNV
3228
5c68b227 3229Coerce the given SV to a double and return it.
cb1a09d0 3230
e89caa19 3231 double SvNV (SV* sv)
cb1a09d0
AD
3232
3233=item SvNVX
3234
5c68b227 3235Returns the double which is stored in the SV, assuming SvNOK is true.
cb1a09d0 3236
e89caa19
GA
3237 double SvNVX (SV* sv)
3238
3239=item SvOK
3240
3241Returns a boolean indicating whether the value is an SV.
3242
3243 int SvOK (SV* sv)
3244
3245=item SvOOK
3246
3247Returns a boolean indicating whether the SvIVX is a valid offset value
3248for the SvPVX. This hack is used internally to speed up removal of
3249characters from the beginning of a SvPV. When SvOOK is true, then the
3250start of the allocated string buffer is really (SvPVX - SvIVX).
3251
9cde0e7f 3252 int SvOOK(SV* sv)
cb1a09d0
AD
3253
3254=item SvPOK
3255
3256Returns a boolean indicating whether the SV contains a character string.
3257
e89caa19 3258 int SvPOK (SV* SV)
cb1a09d0
AD
3259
3260=item SvPOK_off
3261
3262Unsets the PV status of an SV.
3263
e89caa19 3264 void SvPOK_off (SV* sv)
cb1a09d0
AD
3265
3266=item SvPOK_on
3267
3268Tells an SV that it is a string.
3269
e89caa19 3270 void SvPOK_on (SV* sv)
cb1a09d0 3271
5fb8527f
PP
3272=item SvPOK_only
3273
3274Tells an SV that it is a string and disables all other OK bits.
3275
e89caa19 3276 void SvPOK_only (SV* sv)
5fb8527f 3277
cb1a09d0
AD
3278=item SvPOKp
3279
3280Returns a boolean indicating whether the SV contains a character string.
3281Checks the B<private> setting. Use C<SvPOK>.
3282
e89caa19 3283 int SvPOKp (SV* SV)
cb1a09d0
AD
3284
3285=item SvPV
3286
3287Returns a pointer to the string in the SV, or a stringified form of the SV
2d8e6c8d 3288if the SV does not contain a string. Handles 'get' magic.
cb1a09d0 3289
e65f3abd 3290 char* SvPV (SV* sv, STRLEN len)
e89caa19
GA
3291
3292=item SvPV_force
3293
3294Like <SvPV> but will force the SV into becoming a string (SvPOK). You
3295want force if you are going to update the SvPVX directly.
3296
e65f3abd 3297 char* SvPV_force(SV* sv, STRLEN len)
e89caa19 3298
1fa8b10d
JD
3299=item SvPV_nolen
3300
3301Returns a pointer to the string in the SV, or a stringified form of the SV
3302if the SV does not contain a string. Handles 'get' magic.
3303
e65f3abd 3304 char* SvPV_nolen (SV* sv)
cb1a09d0
AD
3305
3306=item SvPVX
3307
3308Returns a pointer to the string in the SV. The SV must contain a string.
3309
e89caa19 3310 char* SvPVX (SV* sv)
cb1a09d0
AD
3311
3312=item SvREFCNT
3313
5f05dabc 3314Returns the value of the object's reference count.
cb1a09d0 3315
e89caa19 3316 int SvREFCNT (SV* sv)
cb1a09d0
AD
3317
3318=item SvREFCNT_dec
3319
5f05dabc 3320Decrements the reference count of the given SV.
cb1a09d0 3321
e89caa19 3322 void SvREFCNT_dec (SV* sv)
cb1a09d0
AD
3323
3324=item SvREFCNT_inc
3325
5f05dabc 3326Increments the reference count of the given SV.
cb1a09d0 3327
e89caa19 3328 void SvREFCNT_inc (SV* sv)
cb1a09d0
AD
3329
3330=item SvROK
3331
3332Tests if the SV is an RV.
3333
e89caa19 3334 int SvROK (SV* sv)
cb1a09d0
AD
3335
3336=item SvROK_off
3337
3338Unsets the RV status of an SV.
3339
e89caa19 3340 void SvROK_off (SV* sv)
cb1a09d0
AD
3341
3342=item SvROK_on
3343
3344Tells an SV that it is an RV.
3345
e89caa19 3346 void SvROK_on (SV* sv)
cb1a09d0
AD
3347
3348=item SvRV
3349
3350Dereferences an RV to return the SV.
3351
ef50df4b 3352 SV* SvRV (SV* sv)
cb1a09d0 3353
189b2af5
GS
3354=item SvSETMAGIC
3355
3356Invokes C<mg_set> on an SV if it has 'set' magic. This macro evaluates
3357its argument more than once.
3358
3359 void SvSETMAGIC( SV *sv )
3360
ef50df4b 3361=item sv_setiv
189b2af5 3362
ef50df4b
GS
3363Copies an integer into the given SV. Does not handle 'set' magic.
3364See C<sv_setiv_mg>.
189b2af5 3365
ef50df4b 3366 void sv_setiv (SV* sv, IV num)
189b2af5 3367
ef50df4b 3368=item sv_setiv_mg
189b2af5 3369
ef50df4b 3370Like C<sv_setiv>, but also handles 'set' magic.
189b2af5 3371
ef50df4b 3372 void sv_setiv_mg (SV* sv, IV num)
189b2af5 3373
ef50df4b 3374=item sv_setnv
189b2af5 3375
ef50df4b
GS
3376Copies a double into the given SV. Does not handle 'set' magic.
3377See C<sv_setnv_mg>.
189b2af5 3378
ef50df4b 3379 void sv_setnv (SV* sv, double num)
189b2af5 3380
ef50df4b 3381=item sv_setnv_mg
189b2af5 3382
ef50df4b 3383Like C<sv_setnv>, but also handles 'set' magic.
189b2af5 3384
ef50df4b 3385 void sv_setnv_mg (SV* sv, double num)
189b2af5 3386
ef50df4b 3387=item sv_setpv
189b2af5 3388
ef50df4b
GS
3389Copies a string into an SV. The string must be null-terminated.
3390Does not handle 'set' magic. See C<sv_setpv_mg>.
189b2af5 3391
08105a92 3392 void sv_setpv (SV* sv, const char* ptr)
189b2af5 3393
ef50df4b 3394=item sv_setpv_mg
189b2af5 3395
ef50df4b 3396Like C<sv_setpv>, but also handles 'set' magic.
189b2af5 3397
08105a92 3398 void sv_setpv_mg (SV* sv, const char* ptr)
189b2af5 3399
ef50df4b 3400=item sv_setpviv
cb1a09d0 3401
ef50df4b
GS
3402Copies an integer into the given SV, also updating its string value.
3403Does not handle 'set' magic. See C<sv_setpviv_mg>.
cb1a09d0 3404
ef50df4b 3405 void sv_setpviv (SV* sv, IV num)
cb1a09d0 3406
ef50df4b 3407=item sv_setpviv_mg
cb1a09d0 3408
ef50df4b 3409Like C<sv_setpviv>, but also handles 'set' magic.
cb1a09d0 3410
ef50df4b 3411 void sv_setpviv_mg (SV* sv, IV num)
cb1a09d0 3412
ef50df4b 3413=item sv_setpvn
cb1a09d0 3414
ef50df4b
GS
3415Copies a string into an SV. The C<len> parameter indicates the number of
3416bytes to be copied. Does not handle 'set' magic. See C<sv_setpvn_mg>.
cb1a09d0 3417
08105a92 3418 void sv_setpvn (SV* sv, const char* ptr, STRLEN len)
cb1a09d0 3419
ef50df4b 3420=item sv_setpvn_mg
189b2af5 3421
ef50df4b 3422Like C<sv_setpvn>, but also handles 'set' magic.
189b2af5 3423
08105a92 3424 void sv_setpvn_mg (SV* sv, const char* ptr, STRLEN len)
189b2af5 3425
ef50df4b 3426=item sv_setpvf
cb1a09d0 3427
ef50df4b
GS
3428Processes its arguments like C<sprintf> and sets an SV to the formatted
3429output. Does not handle 'set' magic. See C<sv_setpvf_mg>.
cb1a09d0 3430
ef50df4b 3431 void sv_setpvf (SV* sv, const char* pat, ...)
cb1a09d0 3432
ef50df4b 3433=item sv_setpvf_mg
46fc3d4c 3434
ef50df4b 3435Like C<sv_setpvf>, but also handles 'set' magic.
46fc3d4c 3436
ef50df4b 3437 void sv_setpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 3438
cb1a09d0
AD
3439=item sv_setref_iv
3440
5fb8527f
PP
3441Copies an integer into a new SV, optionally blessing the SV. The C<rv>
3442argument will be upgraded to an RV. That RV will be modified to point to
3443the new SV. The C<classname> argument indicates the package for the
3444blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3445will be returned and will have a reference count of 1.
cb1a09d0 3446
ef50df4b 3447 SV* sv_setref_iv (SV *rv, char *classname, IV iv)
cb1a09d0
AD
3448
3449=item sv_setref_nv
3450
5fb8527f
PP
3451Copies a double into a new SV, optionally blessing the SV. The C<rv>
3452argument will be upgraded to an RV. That RV will be modified to point to
3453the new SV. The C<classname> argument indicates the package for the
3454blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3455will be returned and will have a reference count of 1.
cb1a09d0 3456
ef50df4b 3457 SV* sv_setref_nv (SV *rv, char *classname, double nv)
cb1a09d0
AD
3458
3459=item sv_setref_pv
3460
5fb8527f
PP
3461Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
3462argument will be upgraded to an RV. That RV will be modified to point to
9cde0e7f 3463the new SV. If the C<pv> argument is NULL then C<PL_sv_undef> will be placed
5fb8527f
PP
3464into the SV. The C<classname> argument indicates the package for the
3465blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3466will be returned and will have a reference count of 1.
cb1a09d0 3467
ef50df4b 3468 SV* sv_setref_pv (SV *rv, char *classname, void* pv)
cb1a09d0
AD
3469
3470Do not use with integral Perl types such as HV, AV, SV, CV, because those
3471objects will become corrupted by the pointer copy process.
3472
3473Note that C<sv_setref_pvn> copies the string while this copies the pointer.
3474
3475=item sv_setref_pvn
3476
5fb8527f
PP
3477Copies a string into a new SV, optionally blessing the SV. The length of the
3478string must be specified with C<n>. The C<rv> argument will be upgraded to
3479an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
3480argument indicates the package for the blessing. Set C<classname> to
3481C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 3482a reference count of 1.
cb1a09d0 3483
ef50df4b 3484 SV* sv_setref_pvn (SV *rv, char *classname, char* pv, I32 n)
cb1a09d0
AD
3485
3486Note that C<sv_setref_pv> copies the pointer while this copies the string.
3487
189b2af5
GS
3488=item SvSetSV
3489
3490Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
3491more than once.
3492
3493 void SvSetSV (SV* dsv, SV* ssv)
3494
3495=item SvSetSV_nosteal
3496
3497Calls a non-destructive version of C<sv_setsv> if dsv is not the same as ssv.
3498May evaluate arguments more than once.
3499
3500 void SvSetSV_nosteal (SV* dsv, SV* ssv)
3501
cb1a09d0
AD
3502=item sv_setsv
3503
3504Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
189b2af5 3505The source SV may be destroyed if it is mortal. Does not handle 'set' magic.
ef50df4b
GS
3506See the macro forms C<SvSetSV>, C<SvSetSV_nosteal> and C<sv_setsv_mg>.
3507
3508 void sv_setsv (SV* dsv, SV* ssv)
3509
3510=item sv_setsv_mg
3511
3512Like C<sv_setsv>, but also handles 'set' magic.
cb1a09d0 3513
ef50df4b 3514 void sv_setsv_mg (SV* dsv, SV* ssv)
cb1a09d0 3515
189b2af5
GS
3516=item sv_setuv
3517
3518Copies an unsigned integer into the given SV. Does not handle 'set' magic.
ef50df4b 3519See C<sv_setuv_mg>.
189b2af5 3520
ef50df4b
GS
3521 void sv_setuv (SV* sv, UV num)
3522
3523=item sv_setuv_mg
3524
3525Like C<sv_setuv>, but also handles 'set' magic.
3526
3527 void sv_setuv_mg (SV* sv, UV num)
189b2af5 3528
cb1a09d0
AD
3529=item SvSTASH
3530
3531Returns the stash of the SV.
3532
e89caa19
GA
3533 HV* SvSTASH (SV* sv)
3534
3535=item SvTAINT
3536
3537Taints an SV if tainting is enabled
3538
3539 void SvTAINT (SV* sv)
3540
3541=item SvTAINTED
3542
3543Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.
3544
3545 int SvTAINTED (SV* sv)
3546
3547=item SvTAINTED_off
3548
3549Untaints an SV. Be I<very> careful with this routine, as it short-circuits
3550some of Perl's fundamental security features. XS module authors should
3551not use this function unless they fully understand all the implications
3552of unconditionally untainting the value. Untainting should be done in
3553the standard perl fashion, via a carefully crafted regexp, rather than
3554directly untainting variables.
3555
3556 void SvTAINTED_off (SV* sv)
3557
3558=item SvTAINTED_on
3559
3560Marks an SV as tainted.
3561
3562 void SvTAINTED_on (SV* sv)
cb1a09d0
AD
3563
3564=item SVt_IV
3565
3566Integer type flag for scalars. See C<svtype>.
3567
3568=item SVt_PV
3569
3570Pointer type flag for scalars. See C<svtype>.
3571
3572=item SVt_PVAV
3573
3574Type flag for arrays. See C<svtype>.
3575
3576=item SVt_PVCV
3577
3578Type flag for code refs. See C<svtype>.
3579
3580=item SVt_PVHV
3581
3582Type flag for hashes. See C<svtype>.
3583
3584=item SVt_PVMG
3585
3586Type flag for blessed scalars. See C<svtype>.
3587
3588=item SVt_NV
3589
3590Double type flag for scalars. See C<svtype>.
3591
3592=item SvTRUE
3593
3594Returns a boolean indicating whether Perl would evaluate the SV as true or
189b2af5 3595false, defined or undefined. Does not handle 'get' magic.
cb1a09d0 3596
e89caa19 3597 int SvTRUE (SV* sv)
cb1a09d0
AD
3598
3599=item SvTYPE
3600
3601Returns the type of the SV. See C<svtype>.
3602
3603 svtype SvTYPE (SV* sv)
3604
3605=item svtype
3606
3607An enum of flags for Perl types. These are found in the file B<sv.h> in the
3608C<svtype> enum. Test these flags with the C<SvTYPE> macro.
3609
9cde0e7f 3610=item PL_sv_undef
cb1a09d0 3611
9cde0e7f 3612This is the C<undef> SV. Always refer to this as C<&PL_sv_undef>.
cb1a09d0 3613
5fb8527f
PP
3614=item sv_unref
3615
07fa94a1
JO
3616Unsets the RV status of the SV, and decrements the reference count of
3617whatever was being referenced by the RV. This can almost be thought of
3618as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f 3619
ef50df4b 3620 void sv_unref (SV* sv)
189b2af5 3621
e89caa19
GA
3622=item SvUPGRADE
3623
3624Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
3625the upgrade if necessary. See C<svtype>.
3626
3627 bool SvUPGRADE (SV* sv, svtype mt)
3628
3629=item sv_upgrade
3630
3631Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
3632
cb1a09d0
AD
3633=item sv_usepvn
3634
3635Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
3636stored inside the SV but sv_usepvn allows the SV to use an outside string.
3637The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
3638string length, C<len>, must be supplied. This function will realloc the
3639memory pointed to by C<ptr>, so that pointer should not be freed or used by
189b2af5 3640the programmer after giving it to sv_usepvn. Does not handle 'set' magic.
ef50df4b
GS
3641See C<sv_usepvn_mg>.