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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
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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
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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".
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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)
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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.
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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
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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
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718[This section still under construction. Ignore everything here. Post no
719bills. Everything not permitted is forbidden.]
720
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AD
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
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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
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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
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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
1509=head1 API LISTING
a0d0e21e 1510
cb1a09d0
AD
1511This is a listing of functions, macros, flags, and variables that may be
1512useful to extension writers or that may be found while reading other
1513extensions.
9cde0e7f
GS
1514
1515Note that all Perl API global variables must be referenced with the C<PL_>
1516prefix. Some macros are provided for compatibility with the older,
1517unadorned names, but this support will be removed in a future release.
1518
1519It is strongly recommended that all Perl API functions that don't begin
1520with C<perl> be referenced with an explicit C<Perl_> prefix.
1521
e89caa19 1522The sort order of the listing is case insensitive, with any
b5a41e52 1523occurrences of '_' ignored for the purpose of sorting.
a0d0e21e 1524
cb1a09d0 1525=over 8
a0d0e21e 1526
cb1a09d0
AD
1527=item av_clear
1528
0146554f
GA
1529Clears an array, making it empty. Does not free the memory used by the
1530array itself.
cb1a09d0 1531
ef50df4b 1532 void av_clear (AV* ar)
cb1a09d0
AD
1533
1534=item av_extend
1535
1536Pre-extend an array. The C<key> is the index to which the array should be
1537extended.
1538
ef50df4b 1539 void av_extend (AV* ar, I32 key)
cb1a09d0
AD
1540
1541=item av_fetch
1542
1543Returns the SV at the specified index in the array. The C<key> is the
1544index. If C<lval> is set then the fetch will be part of a store. Check
1545that the return value is non-null before dereferencing it to a C<SV*>.
1546
04343c6d
GS
1547See L<Understanding the Magic of Tied Hashes and Arrays> for more
1548information on how to use this function on tied arrays.
1549
ef50df4b 1550 SV** av_fetch (AV* ar, I32 key, I32 lval)
cb1a09d0 1551
e89caa19
GA
1552=item AvFILL
1553
95906810 1554Same as C<av_len()>. Deprecated, use C<av_len()> instead.
e89caa19 1555
cb1a09d0
AD
1556=item av_len
1557
1558Returns the highest index in the array. Returns -1 if the array is empty.
1559
ef50df4b 1560 I32 av_len (AV* ar)
cb1a09d0
AD
1561
1562=item av_make
1563
5fb8527f
PP
1564Creates a new AV and populates it with a list of SVs. The SVs are copied
1565into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1566will have a reference count of 1.
cb1a09d0 1567
ef50df4b 1568 AV* av_make (I32 size, SV** svp)
cb1a09d0
AD
1569
1570=item av_pop
1571
9cde0e7f 1572Pops an SV off the end of the array. Returns C<&PL_sv_undef> if the array is
cb1a09d0
AD
1573empty.
1574
ef50df4b 1575 SV* av_pop (AV* ar)
cb1a09d0
AD
1576
1577=item av_push
1578
5fb8527f
PP
1579Pushes an SV onto the end of the array. The array will grow automatically
1580to accommodate the addition.
cb1a09d0 1581
ef50df4b 1582 void av_push (AV* ar, SV* val)
cb1a09d0
AD
1583
1584=item av_shift
1585
1586Shifts an SV off the beginning of the array.
1587
ef50df4b 1588 SV* av_shift (AV* ar)
cb1a09d0
AD
1589
1590=item av_store
1591
1592Stores an SV in an array. The array index is specified as C<key>. The
04343c6d
GS
1593return value will be NULL if the operation failed or if the value did not
1594need to be actually stored within the array (as in the case of tied arrays).
1595Otherwise it can be dereferenced to get the original C<SV*>. Note that the
1596caller is responsible for suitably incrementing the reference count of C<val>
1597before the call, and decrementing it if the function returned NULL.
1598
1599See L<Understanding the Magic of Tied Hashes and Arrays> for more
1600information on how to use this function on tied arrays.
cb1a09d0 1601
ef50df4b 1602 SV** av_store (AV* ar, I32 key, SV* val)
cb1a09d0
AD
1603
1604=item av_undef
1605
0146554f 1606Undefines the array. Frees the memory used by the array itself.
cb1a09d0 1607
ef50df4b 1608 void av_undef (AV* ar)
cb1a09d0
AD
1609
1610=item av_unshift
1611
0146554f
GA
1612Unshift the given number of C<undef> values onto the beginning of the
1613array. The array will grow automatically to accommodate the addition.
1614You must then use C<av_store> to assign values to these new elements.
cb1a09d0 1615
ef50df4b 1616 void av_unshift (AV* ar, I32 num)
cb1a09d0
AD
1617
1618=item CLASS
1619
1620Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1621constructor. This is always a C<char*>. See C<THIS> and
1622L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1623
1624=item Copy
1625
1626The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1627source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 1628the type. May fail on overlapping copies. See also C<Move>.
cb1a09d0 1629
e89caa19 1630 void Copy( s, d, n, t )
cb1a09d0
AD
1631
1632=item croak
1633
1634This is the XSUB-writer's interface to Perl's C<die> function. Use this
1635function the same way you use the C C<printf> function. See C<warn>.
1636
1637=item CvSTASH
1638
1639Returns the stash of the CV.
1640
e89caa19 1641 HV* CvSTASH( SV* sv )
cb1a09d0 1642
9cde0e7f 1643=item PL_DBsingle
cb1a09d0
AD
1644
1645When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1646boolean which indicates whether subs are being single-stepped.
5fb8527f 1647Single-stepping is automatically turned on after every step. This is the C
9cde0e7f 1648variable which corresponds to Perl's $DB::single variable. See C<PL_DBsub>.
cb1a09d0 1649
9cde0e7f 1650=item PL_DBsub
cb1a09d0
AD
1651
1652When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f 1653the SV which holds the name of the sub being debugged. This is the C
9cde0e7f 1654variable which corresponds to Perl's $DB::sub variable. See C<PL_DBsingle>.
cb1a09d0
AD
1655The sub name can be found by
1656
2d8e6c8d 1657 SvPV( GvSV( PL_DBsub ), len )
cb1a09d0 1658
9cde0e7f 1659=item PL_DBtrace
5fb8527f
PP
1660
1661Trace variable used when Perl is run in debugging mode, with the B<-d>
1662switch. This is the C variable which corresponds to Perl's $DB::trace
9cde0e7f 1663variable. See C<PL_DBsingle>.
5fb8527f 1664
cb1a09d0
AD
1665=item dMARK
1666
5fb8527f
PP
1667Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1668C<dORIGMARK>.
cb1a09d0
AD
1669
1670=item dORIGMARK
1671
1672Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1673
9cde0e7f 1674=item PL_dowarn
5fb8527f
PP
1675
1676The C variable which corresponds to Perl's $^W warning variable.
1677
cb1a09d0
AD
1678=item dSP
1679
924508f0
GS
1680Declares a local copy of perl's stack pointer for the XSUB, available via
1681the C<SP> macro. See C<SP>.
cb1a09d0
AD
1682
1683=item dXSARGS
1684
1685Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1686usually handled automatically by C<xsubpp>. Declares the C<items> variable
1687to indicate the number of items on the stack.
1688
5fb8527f
PP
1689=item dXSI32
1690
1691Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1692handled automatically by C<xsubpp>.
1693
491527d0
GS
1694=item do_binmode
1695
1696Switches filehandle to binmode. C<iotype> is what C<IoTYPE(io)> would
1697contain.
1698
1699 do_binmode(fp, iotype, TRUE);
1700
cb1a09d0
AD
1701=item ENTER
1702
1703Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1704
1705 ENTER;
1706
1707=item EXTEND
1708
1709Used to extend the argument stack for an XSUB's return values.
1710
ef50df4b 1711 EXTEND( sp, int x )
cb1a09d0 1712
e89caa19
GA
1713=item fbm_compile
1714
1715Analyses the string in order to make fast searches on it using fbm_instr() --
1716the Boyer-Moore algorithm.
1717
411d5715 1718 void fbm_compile(SV* sv, U32 flags)
e89caa19
GA
1719
1720=item fbm_instr
1721
1722Returns the location of the SV in the string delimited by C<str> and
1723C<strend>. It returns C<Nullch> if the string can't be found. The
1724C<sv> does not have to be fbm_compiled, but the search will not be as
1725fast then.
1726
411d5715 1727 char* fbm_instr(char *str, char *strend, SV *sv, U32 flags)
e89caa19 1728
cb1a09d0
AD
1729=item FREETMPS
1730
1731Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1732L<perlcall>.
1733
1734 FREETMPS;
1735
1736=item G_ARRAY
1737
54310121 1738Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
cb1a09d0
AD
1739
1740=item G_DISCARD
1741
1742Indicates that arguments returned from a callback should be discarded. See
1743L<perlcall>.
1744
1745=item G_EVAL
1746
1747Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1748
1749=item GIMME
1750
54310121
PP
1751A backward-compatible version of C<GIMME_V> which can only return
1752C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
1753
1754=item GIMME_V
1755
1756The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
1757C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
1758context, respectively.
cb1a09d0
AD
1759
1760=item G_NOARGS
1761
1762Indicates that no arguments are being sent to a callback. See L<perlcall>.
1763
1764=item G_SCALAR
1765
54310121
PP
1766Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
1767
faed5253
JO
1768=item gv_fetchmeth
1769
1770Returns the glob with the given C<name> and a defined subroutine or
9607fc9c 1771C<NULL>. The glob lives in the given C<stash>, or in the stashes
f86cebdf 1772accessible via @ISA and @UNIVERSAL.
faed5253 1773
9607fc9c 1774The argument C<level> should be either 0 or -1. If C<level==0>, as a
0a753a76
PP
1775side-effect creates a glob with the given C<name> in the given
1776C<stash> which in the case of success contains an alias for the
1777subroutine, and sets up caching info for this glob. Similarly for all
1778the searched stashes.
1779
9607fc9c
PP
1780This function grants C<"SUPER"> token as a postfix of the stash name.
1781
0a753a76
PP
1782The GV returned from C<gv_fetchmeth> may be a method cache entry,
1783which is not visible to Perl code. So when calling C<perl_call_sv>,
1784you should not use the GV directly; instead, you should use the
1785method's CV, which can be obtained from the GV with the C<GvCV> macro.
faed5253 1786
08105a92 1787 GV* gv_fetchmeth (HV* stash, const char* name, STRLEN len, I32 level)
faed5253
JO
1788
1789=item gv_fetchmethod
1790
dc848c6f
PP
1791=item gv_fetchmethod_autoload
1792
faed5253 1793Returns the glob which contains the subroutine to call to invoke the
c2611fb3 1794method on the C<stash>. In fact in the presence of autoloading this may
dc848c6f 1795be the glob for "AUTOLOAD". In this case the corresponding variable
faed5253
JO
1796$AUTOLOAD is already setup.
1797
dc848c6f
PP
1798The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
1799lookup is performed if the given method is not present: non-zero means
1800yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
1801C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
1802non-zero C<autoload> parameter.
1803
1804These functions grant C<"SUPER"> token as a prefix of the method name.
1805
1806Note that if you want to keep the returned glob for a long time, you
1807need to check for it being "AUTOLOAD", since at the later time the call
faed5253
JO
1808may load a different subroutine due to $AUTOLOAD changing its value.
1809Use the glob created via a side effect to do this.
1810
dc848c6f
PP
1811These functions have the same side-effects and as C<gv_fetchmeth> with
1812C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
0a753a76 1813The warning against passing the GV returned by C<gv_fetchmeth> to
dc848c6f 1814C<perl_call_sv> apply equally to these functions.
faed5253 1815
08105a92
GS
1816 GV* gv_fetchmethod (HV* stash, const char* name)
1817 GV* gv_fetchmethod_autoload (HV* stash, const char* name, I32 autoload)
faed5253 1818
e89caa19
GA
1819=item G_VOID
1820
1821Used to indicate void context. See C<GIMME_V> and L<perlcall>.
1822
cb1a09d0
AD
1823=item gv_stashpv
1824
1825Returns a pointer to the stash for a specified package. If C<create> is set
1826then the package will be created if it does not already exist. If C<create>
1827is not set and the package does not exist then NULL is returned.
1828
08105a92 1829 HV* gv_stashpv (const char* name, I32 create)
cb1a09d0
AD
1830
1831=item gv_stashsv
1832
1833Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1834
ef50df4b 1835 HV* gv_stashsv (SV* sv, I32 create)
cb1a09d0 1836
e5581bf4 1837=item GvSV
cb1a09d0 1838
e5581bf4 1839Return the SV from the GV.
44a8e56a 1840
1e422769
PP
1841=item HEf_SVKEY
1842
1843This flag, used in the length slot of hash entries and magic
1844structures, specifies the structure contains a C<SV*> pointer where a
1845C<char*> pointer is to be expected. (For information only--not to be used).
1846
1e422769
PP
1847=item HeHASH
1848
e89caa19 1849Returns the computed hash stored in the hash entry.
1e422769 1850
e89caa19 1851 U32 HeHASH(HE* he)
1e422769
PP
1852
1853=item HeKEY
1854
1855Returns the actual pointer stored in the key slot of the hash entry.
1856The pointer may be either C<char*> or C<SV*>, depending on the value of
1857C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1858are usually preferable for finding the value of a key.
1859
e89caa19 1860 char* HeKEY(HE* he)
1e422769
PP
1861
1862=item HeKLEN
1863
1864If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1865holds an C<SV*> key. Otherwise, holds the actual length of the key.
1866Can be assigned to. The C<HePV()> macro is usually preferable for finding
1867key lengths.
1868
e89caa19 1869 int HeKLEN(HE* he)
1e422769
PP
1870
1871=item HePV
1872
1873Returns the key slot of the hash entry as a C<char*> value, doing any
1874necessary dereferencing of possibly C<SV*> keys. The length of
1875the string is placed in C<len> (this is a macro, so do I<not> use
1876C<&len>). If you do not care about what the length of the key is,
2d8e6c8d
GS
1877you may use the global variable C<PL_na>, though this is rather less
1878efficient than using a local variable. Remember though, that hash
1e422769
PP
1879keys in perl are free to contain embedded nulls, so using C<strlen()>
1880or similar is not a good way to find the length of hash keys.
1881This is very similar to the C<SvPV()> macro described elsewhere in
1882this document.
1883
e89caa19 1884 char* HePV(HE* he, STRLEN len)
1e422769
PP
1885
1886=item HeSVKEY
1887
1888Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1889does not contain an C<SV*> key.
1890
1891 HeSVKEY(HE* he)
1892
1893=item HeSVKEY_force
1894
1895Returns the key as an C<SV*>. Will create and return a temporary
1896mortal C<SV*> if the hash entry contains only a C<char*> key.
1897
1898 HeSVKEY_force(HE* he)
1899
1900=item HeSVKEY_set
1901
1902Sets the key to a given C<SV*>, taking care to set the appropriate flags
1903to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1904
1905 HeSVKEY_set(HE* he, SV* sv)
1906
1907=item HeVAL
1908
1909Returns the value slot (type C<SV*>) stored in the hash entry.
1910
1911 HeVAL(HE* he)
1912
cb1a09d0
AD
1913=item hv_clear
1914
1915Clears a hash, making it empty.
1916
ef50df4b 1917 void hv_clear (HV* tb)
cb1a09d0
AD
1918
1919=item hv_delete
1920
1921Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 1922and returned to the caller. The C<klen> is the length of the key. The
04343c6d 1923C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
cb1a09d0
AD
1924returned.
1925
08105a92 1926 SV* hv_delete (HV* tb, const char* key, U32 klen, I32 flags)
cb1a09d0 1927
1e422769
PP
1928=item hv_delete_ent
1929
1930Deletes a key/value pair in the hash. The value SV is removed from the hash
1931and returned to the caller. The C<flags> value will normally be zero; if set
04343c6d 1932to G_DISCARD then NULL will be returned. C<hash> can be a valid precomputed
1e422769
PP
1933hash value, or 0 to ask for it to be computed.
1934
ef50df4b 1935 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash)
1e422769 1936
cb1a09d0
AD
1937=item hv_exists
1938
1939Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 1940C<klen> is the length of the key.
cb1a09d0 1941
08105a92 1942 bool hv_exists (HV* tb, const char* key, U32 klen)
cb1a09d0 1943
1e422769
PP
1944=item hv_exists_ent
1945
1946Returns a boolean indicating whether the specified hash key exists. C<hash>
54310121 1947can be a valid precomputed hash value, or 0 to ask for it to be computed.
1e422769 1948
ef50df4b 1949 bool hv_exists_ent (HV* tb, SV* key, U32 hash)
1e422769 1950
cb1a09d0
AD
1951=item hv_fetch
1952
1953Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 1954C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
1955part of a store. Check that the return value is non-null before
1956dereferencing it to a C<SV*>.
1957
04343c6d
GS
1958See L<Understanding the Magic of Tied Hashes and Arrays> for more
1959information on how to use this function on tied hashes.
1960
08105a92 1961 SV** hv_fetch (HV* tb, const char* key, U32 klen, I32 lval)
cb1a09d0 1962
1e422769
PP
1963=item hv_fetch_ent
1964
1965Returns the hash entry which corresponds to the specified key in the hash.
54310121 1966C<hash> must be a valid precomputed hash number for the given C<key>, or
1e422769
PP
19670 if you want the function to compute it. IF C<lval> is set then the
1968fetch will be part of a store. Make sure the return value is non-null
1969before accessing it. The return value when C<tb> is a tied hash
1970is a pointer to a static location, so be sure to make a copy of the
1971structure if you need to store it somewhere.
1972
04343c6d
GS
1973See L<Understanding the Magic of Tied Hashes and Arrays> for more
1974information on how to use this function on tied hashes.
1975
ef50df4b 1976 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash)
1e422769 1977
cb1a09d0
AD
1978=item hv_iterinit
1979
1980Prepares a starting point to traverse a hash table.
1981
ef50df4b 1982 I32 hv_iterinit (HV* tb)
cb1a09d0 1983
c6601927
SI
1984Returns the number of keys in the hash (i.e. the same as C<HvKEYS(tb)>).
1985The return value is currently only meaningful for hashes without tie
1986magic.
1987
1988NOTE: Before version 5.004_65, C<hv_iterinit> used to return the number
1989of hash buckets that happen to be in use. If you still need that
1990esoteric value, you can get it through the macro C<HvFILL(tb)>.
fb73857a 1991
cb1a09d0
AD
1992=item hv_iterkey
1993
1994Returns the key from the current position of the hash iterator. See
1995C<hv_iterinit>.
1996
ef50df4b 1997 char* hv_iterkey (HE* entry, I32* retlen)
cb1a09d0 1998
1e422769 1999=item hv_iterkeysv
3fe9a6f1 2000
1e422769
PP
2001Returns the key as an C<SV*> from the current position of the hash
2002iterator. The return value will always be a mortal copy of the
2003key. Also see C<hv_iterinit>.
2004
ef50df4b 2005 SV* hv_iterkeysv (HE* entry)
1e422769 2006
cb1a09d0
AD
2007=item hv_iternext
2008
2009Returns entries from a hash iterator. See C<hv_iterinit>.
2010
ef50df4b 2011 HE* hv_iternext (HV* tb)
cb1a09d0
AD
2012
2013=item hv_iternextsv
2014
2015Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
2016operation.
2017
e89caa19 2018 SV* hv_iternextsv (HV* hv, char** key, I32* retlen)
cb1a09d0
AD
2019
2020=item hv_iterval
2021
2022Returns the value from the current position of the hash iterator. See
2023C<hv_iterkey>.
2024
ef50df4b 2025 SV* hv_iterval (HV* tb, HE* entry)
cb1a09d0
AD
2026
2027=item hv_magic
2028
2029Adds magic to a hash. See C<sv_magic>.
2030
ef50df4b 2031 void hv_magic (HV* hv, GV* gv, int how)
cb1a09d0
AD
2032
2033=item HvNAME
2034
2035Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
2036
e89caa19 2037 char* HvNAME (HV* stash)
cb1a09d0
AD
2038
2039=item hv_store
2040
2041Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
54310121 2042the length of the key. The C<hash> parameter is the precomputed hash
cb1a09d0 2043value; if it is zero then Perl will compute it. The return value will be
04343c6d
GS
2044NULL if the operation failed or if the value did not need to be actually
2045stored within the hash (as in the case of tied hashes). Otherwise it can
2046be dereferenced to get the original C<SV*>. Note that the caller is
2047responsible for suitably incrementing the reference count of C<val>
2048before the call, and decrementing it if the function returned NULL.
2049
2050See L<Understanding the Magic of Tied Hashes and Arrays> for more
2051information on how to use this function on tied hashes.
cb1a09d0 2052
08105a92 2053 SV** hv_store (HV* tb, const char* key, U32 klen, SV* val, U32 hash)
cb1a09d0 2054
1e422769
PP
2055=item hv_store_ent
2056
2057Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
54310121 2058parameter is the precomputed hash value; if it is zero then Perl will
1e422769 2059compute it. The return value is the new hash entry so created. It will be
04343c6d
GS
2060NULL if the operation failed or if the value did not need to be actually
2061stored within the hash (as in the case of tied hashes). Otherwise the
2062contents of the return value can be accessed using the C<He???> macros
2063described here. Note that the caller is responsible for suitably
2064incrementing the reference count of C<val> before the call, and decrementing
2065it if the function returned NULL.
2066
2067See L<Understanding the Magic of Tied Hashes and Arrays> for more
2068information on how to use this function on tied hashes.
1e422769 2069
ef50df4b 2070 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash)
1e422769 2071
cb1a09d0
AD
2072=item hv_undef
2073
2074Undefines the hash.
2075
ef50df4b 2076 void hv_undef (HV* tb)
cb1a09d0
AD
2077
2078=item isALNUM
2079
2080Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 2081character or digit.
cb1a09d0 2082
e89caa19 2083 int isALNUM (char c)
cb1a09d0
AD
2084
2085=item isALPHA
2086
5fb8527f 2087Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
2088character.
2089
e89caa19 2090 int isALPHA (char c)
cb1a09d0
AD
2091
2092=item isDIGIT
2093
2094Returns a boolean indicating whether the C C<char> is an ascii digit.
2095
e89caa19 2096 int isDIGIT (char c)
cb1a09d0
AD
2097
2098=item isLOWER
2099
2100Returns a boolean indicating whether the C C<char> is a lowercase character.
2101
e89caa19 2102 int isLOWER (char c)
cb1a09d0
AD
2103
2104=item isSPACE
2105
2106Returns a boolean indicating whether the C C<char> is whitespace.
2107
e89caa19 2108 int isSPACE (char c)
cb1a09d0
AD
2109
2110=item isUPPER
2111
2112Returns a boolean indicating whether the C C<char> is an uppercase character.
2113
e89caa19 2114 int isUPPER (char c)
cb1a09d0
AD
2115
2116=item items
2117
2118Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
2119stack. See L<perlxs/"Variable-length Parameter Lists">.
2120
2121=item ix
2122
2123Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
2124was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
2125
2126=item LEAVE
2127
2128Closing bracket on a callback. See C<ENTER> and L<perlcall>.
2129
2130 LEAVE;
2131
e89caa19
GA
2132=item looks_like_number
2133
2134Test if an the content of an SV looks like a number (or is a number).
2135
2136 int looks_like_number(SV*)
2137
2138
cb1a09d0
AD
2139=item MARK
2140
5fb8527f 2141Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
2142
2143=item mg_clear
2144
2145Clear something magical that the SV represents. See C<sv_magic>.
2146
ef50df4b 2147 int mg_clear (SV* sv)
cb1a09d0
AD
2148
2149=item mg_copy
2150
2151Copies the magic from one SV to another. See C<sv_magic>.
2152
08105a92 2153 int mg_copy (SV *, SV *, const char *, STRLEN)
cb1a09d0
AD
2154
2155=item mg_find
2156
2157Finds the magic pointer for type matching the SV. See C<sv_magic>.
2158
ef50df4b 2159 MAGIC* mg_find (SV* sv, int type)
cb1a09d0
AD
2160
2161=item mg_free
2162
2163Free any magic storage used by the SV. See C<sv_magic>.
2164
ef50df4b 2165 int mg_free (SV* sv)
cb1a09d0
AD
2166
2167=item mg_get
2168
2169Do magic after a value is retrieved from the SV. See C<sv_magic>.
2170
ef50df4b 2171 int mg_get (SV* sv)
cb1a09d0
AD
2172
2173=item mg_len
2174
2175Report on the SV's length. See C<sv_magic>.
2176
ef50df4b 2177 U32 mg_len (SV* sv)
cb1a09d0
AD
2178
2179=item mg_magical
2180
2181Turns on the magical status of an SV. See C<sv_magic>.
2182
ef50df4b 2183 void mg_magical (SV* sv)
cb1a09d0
AD
2184
2185=item mg_set
2186
2187Do magic after a value is assigned to the SV. See C<sv_magic>.
2188
ef50df4b 2189 int mg_set (SV* sv)
cb1a09d0 2190
b0fffe30
JP
2191=item modglobal
2192
2193C<modglobal> is a general purpose, interpreter global HV for use by
db696efe
GS
2194extensions that need to keep information on a per-interpreter basis.
2195In a pinch, it can also be used as a symbol table for extensions
2196to share data among each other. It is a good idea to use keys
2197prefixed by the package name of the extension that owns the data.
b0fffe30 2198
cb1a09d0
AD
2199=item Move
2200
2201The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
2202source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 2203the type. Can do overlapping moves. See also C<Copy>.
cb1a09d0 2204
e89caa19 2205 void Move( s, d, n, t )
cb1a09d0 2206
9cde0e7f 2207=item PL_na
cb1a09d0 2208
2d8e6c8d
GS
2209A convenience variable which is typically used with C<SvPV> when one doesn't
2210care about the length of the string. It is usually more efficient to
1fa8b10d
JD
2211either declare a local variable and use that instead or to use the C<SvPV_nolen>
2212macro.
cb1a09d0
AD
2213
2214=item New
2215
2216The XSUB-writer's interface to the C C<malloc> function.
2217
e89caa19 2218 void* New( x, void *ptr, int size, type )
cb1a09d0
AD
2219
2220=item newAV
2221
5f05dabc 2222Creates a new AV. The reference count is set to 1.
cb1a09d0 2223
ef50df4b 2224 AV* newAV (void)
cb1a09d0 2225
e89caa19
GA
2226=item Newc
2227
2228The XSUB-writer's interface to the C C<malloc> function, with cast.
2229
2230 void* Newc( x, void *ptr, int size, type, cast )
2231
5476c433
JD
2232=item newCONSTSUB
2233
2234Creates a constant sub equivalent to Perl C<sub FOO () { 123 }>
2235which is eligible for inlining at compile-time.
2236
2237 void newCONSTSUB(HV* stash, char* name, SV* sv)
2238
cb1a09d0
AD
2239=item newHV
2240
5f05dabc 2241Creates a new HV. The reference count is set to 1.
cb1a09d0 2242
ef50df4b 2243 HV* newHV (void)
cb1a09d0 2244
5f05dabc 2245=item newRV_inc
cb1a09d0 2246
5f05dabc 2247Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
2248incremented.
2249
ef50df4b 2250 SV* newRV_inc (SV* ref)
5f05dabc
PP
2251
2252For historical reasons, "newRV" is a synonym for "newRV_inc".
2253
2254=item newRV_noinc
2255
2256Creates an RV wrapper for an SV. The reference count for the original
2257SV is B<not> incremented.
2258
ef50df4b 2259 SV* newRV_noinc (SV* ref)
cb1a09d0 2260
8c52afec 2261=item NEWSV
cb1a09d0 2262
e89caa19
GA
2263Creates a new SV. A non-zero C<len> parameter indicates the number of
2264bytes of preallocated string space the SV should have. An extra byte
2265for a tailing NUL is also reserved. (SvPOK is not set for the SV even
2266if string space is allocated.) The reference count for the new SV is
2267set to 1. C<id> is an integer id between 0 and 1299 (used to identify
2268leaks).
cb1a09d0 2269
ef50df4b 2270 SV* NEWSV (int id, STRLEN len)
cb1a09d0
AD
2271
2272=item newSViv
2273
07fa94a1
JO
2274Creates a new SV and copies an integer into it. The reference count for the
2275SV is set to 1.
cb1a09d0 2276
ef50df4b 2277 SV* newSViv (IV i)
cb1a09d0
AD
2278
2279=item newSVnv
2280
07fa94a1
JO
2281Creates a new SV and copies a double into it. The reference count for the
2282SV is set to 1.
cb1a09d0 2283
ef50df4b 2284 SV* newSVnv (NV i)
cb1a09d0
AD
2285
2286=item newSVpv
2287
07fa94a1 2288Creates a new SV and copies a string into it. The reference count for the
79cb57f6
GS
2289SV is set to 1. If C<len> is zero, Perl will compute the length using
2290strlen(). For efficiency, consider using C<newSVpvn> instead.
cb1a09d0 2291
08105a92 2292 SV* newSVpv (const char* s, STRLEN len)
cb1a09d0 2293
e89caa19
GA
2294=item newSVpvf
2295
2296Creates a new SV an initialize it with the string formatted like
2297C<sprintf>.
2298
79cb57f6 2299 SV* newSVpvf(const char* pat, ...)
e89caa19 2300
9da1e3b5
MUN
2301=item newSVpvn
2302
2303Creates a new SV and copies a string into it. The reference count for the
79cb57f6
GS
2304SV is set to 1. Note that if C<len> is zero, Perl will create a zero length
2305string. You are responsible for ensuring that the source string is at least
2306C<len> bytes long.
9da1e3b5 2307
08105a92 2308 SV* newSVpvn (const char* s, STRLEN len)
9da1e3b5 2309
cb1a09d0
AD
2310=item newSVrv
2311
2312Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 2313it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 2314be blessed in the specified package. The new SV is returned and its
5f05dabc 2315reference count is 1.
8ebc5c01 2316
08105a92 2317 SV* newSVrv (SV* rv, const char* classname)
cb1a09d0
AD
2318
2319=item newSVsv
2320
5fb8527f 2321Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0 2322
ef50df4b 2323 SV* newSVsv (SV* old)
cb1a09d0
AD
2324
2325=item newXS
2326
2327Used by C<xsubpp> to hook up XSUBs as Perl subs.
2328
2329=item newXSproto
2330
2331Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
2332the subs.
2333
e89caa19
GA
2334=item Newz
2335
2336The XSUB-writer's interface to the C C<malloc> function. The allocated
2337memory is zeroed with C<memzero>.
2338
2339 void* Newz( x, void *ptr, int size, type )
2340
cb1a09d0
AD
2341=item Nullav
2342
2343Null AV pointer.
2344
2345=item Nullch
2346
2347Null character pointer.
2348
2349=item Nullcv
2350
2351Null CV pointer.
2352
2353=item Nullhv
2354
2355Null HV pointer.
2356
2357=item Nullsv
2358
2359Null SV pointer.
2360
2361=item ORIGMARK
2362
2363The original stack mark for the XSUB. See C<dORIGMARK>.
2364
2365=item perl_alloc
2366
2367Allocates a new Perl interpreter. See L<perlembed>.
2368
2369=item perl_call_argv
2370
2371Performs a callback to the specified Perl sub. See L<perlcall>.
2372
08105a92 2373 I32 perl_call_argv (const char* subname, I32 flags, char** argv)
cb1a09d0
AD
2374
2375=item perl_call_method
2376
2377Performs a callback to the specified Perl method. The blessed object must
2378be on the stack. See L<perlcall>.
2379
08105a92 2380 I32 perl_call_method (const char* methname, I32 flags)
cb1a09d0
AD
2381
2382=item perl_call_pv
2383
2384Performs a callback to the specified Perl sub. See L<perlcall>.
2385
08105a92 2386 I32 perl_call_pv (const char* subname, I32 flags)
cb1a09d0
AD
2387
2388=item perl_call_sv
2389
2390Performs a callback to the Perl sub whose name is in the SV. See
2391L<perlcall>.
2392
ef50df4b 2393 I32 perl_call_sv (SV* sv, I32 flags)
cb1a09d0
AD
2394
2395=item perl_construct
2396
2397Initializes a new Perl interpreter. See L<perlembed>.
2398
2399=item perl_destruct
2400
2401Shuts down a Perl interpreter. See L<perlembed>.
2402
2403=item perl_eval_sv
2404
2405Tells Perl to C<eval> the string in the SV.
2406
ef50df4b 2407 I32 perl_eval_sv (SV* sv, I32 flags)
cb1a09d0 2408
137443ea
PP
2409=item perl_eval_pv
2410
2411Tells Perl to C<eval> the given string and return an SV* result.
2412
08105a92 2413 SV* perl_eval_pv (const char* p, I32 croak_on_error)
137443ea 2414
cb1a09d0
AD
2415=item perl_free
2416
2417Releases a Perl interpreter. See L<perlembed>.
2418
2419=item perl_get_av
2420
2421Returns the AV of the specified Perl array. If C<create> is set and the
2422Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2423set and the variable does not exist then NULL is returned.
cb1a09d0 2424
08105a92 2425 AV* perl_get_av (const char* name, I32 create)
cb1a09d0
AD
2426
2427=item perl_get_cv
2428
f6ec51f7
GS
2429Returns the CV of the specified Perl subroutine. If C<create> is set and
2430the Perl subroutine does not exist then it will be declared (which has
2431the same effect as saying C<sub name;>). If C<create> is not
2432set and the subroutine does not exist then NULL is returned.
cb1a09d0 2433
08105a92 2434 CV* perl_get_cv (const char* name, I32 create)
cb1a09d0
AD
2435
2436=item perl_get_hv
2437
2438Returns the HV of the specified Perl hash. If C<create> is set and the Perl
2439variable does not exist then it will be created. If C<create> is not
04343c6d 2440set and the variable does not exist then NULL is returned.
cb1a09d0 2441
08105a92 2442 HV* perl_get_hv (const char* name, I32 create)
cb1a09d0
AD
2443
2444=item perl_get_sv
2445
2446Returns the SV of the specified Perl scalar. If C<create> is set and the
2447Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2448set and the variable does not exist then NULL is returned.
cb1a09d0 2449
08105a92 2450 SV* perl_get_sv (const char* name, I32 create)
cb1a09d0
AD
2451
2452=item perl_parse
2453
2454Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2455
2456=item perl_require_pv
2457
2458Tells Perl to C<require> a module.
2459
08105a92 2460 void perl_require_pv (const char* pv)
cb1a09d0
AD
2461
2462=item perl_run
2463
2464Tells a Perl interpreter to run. See L<perlembed>.
2465
2466=item POPi
2467
2468Pops an integer off the stack.
2469
e89caa19 2470 int POPi()
cb1a09d0
AD
2471
2472=item POPl
2473
2474Pops a long off the stack.
2475
e89caa19 2476 long POPl()
cb1a09d0
AD
2477
2478=item POPp
2479
2480Pops a string off the stack.
2481
e89caa19 2482 char* POPp()
cb1a09d0
AD
2483
2484=item POPn
2485
2486Pops a double off the stack.
2487
e89caa19 2488 double POPn()
cb1a09d0
AD
2489
2490=item POPs
2491
2492Pops an SV off the stack.
2493
e89caa19 2494 SV* POPs()
cb1a09d0
AD
2495
2496=item PUSHMARK
2497
2498Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2499
2500 PUSHMARK(p)
2501
2502=item PUSHi
2503
2504Push an integer onto the stack. The stack must have room for this element.
189b2af5 2505Handles 'set' magic. See C<XPUSHi>.
cb1a09d0 2506
e89caa19 2507 void PUSHi(int d)
cb1a09d0
AD
2508
2509=item PUSHn
2510
2511Push a double onto the stack. The stack must have room for this element.
189b2af5 2512Handles 'set' magic. See C<XPUSHn>.
cb1a09d0 2513
e89caa19 2514 void PUSHn(double d)
cb1a09d0
AD
2515
2516=item PUSHp
2517
2518Push a string onto the stack. The stack must have room for this element.
189b2af5
GS
2519The C<len> indicates the length of the string. Handles 'set' magic. See
2520C<XPUSHp>.
cb1a09d0 2521
e89caa19 2522 void PUSHp(char *c, int len )
cb1a09d0
AD
2523
2524=item PUSHs
2525
189b2af5
GS
2526Push an SV onto the stack. The stack must have room for this element. Does
2527not handle 'set' magic. See C<XPUSHs>.
cb1a09d0 2528
e89caa19
GA
2529 void PUSHs(sv)
2530
2531=item PUSHu
2532
2533Push an unsigned integer onto the stack. The stack must have room for
2534this element. See C<XPUSHu>.
2535
2536 void PUSHu(unsigned int d)
2537
cb1a09d0
AD
2538
2539=item PUTBACK
2540
2541Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2542See C<PUSHMARK> and L<perlcall> for other uses.
2543
2544 PUTBACK;
2545
2546=item Renew
2547
2548The XSUB-writer's interface to the C C<realloc> function.
2549
e89caa19 2550 void* Renew( void *ptr, int size, type )
cb1a09d0
AD
2551
2552=item Renewc
2553
2554The XSUB-writer's interface to the C C<realloc> function, with cast.
2555
e89caa19 2556 void* Renewc( void *ptr, int size, type, cast )
cb1a09d0
AD
2557
2558=item RETVAL
2559
2560Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
2561This is always the proper type for the XSUB.
2562See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
2563
2564=item safefree
2565
2566The XSUB-writer's interface to the C C<free> function.
2567
2568=item safemalloc
2569
2570The XSUB-writer's interface to the C C<malloc> function.
2571
2572=item saferealloc
2573
2574The XSUB-writer's interface to the C C<realloc> function.
2575
2576=item savepv
2577
2578Copy a string to a safe spot. This does not use an SV.
2579
08105a92 2580 char* savepv (const char* sv)
cb1a09d0
AD
2581
2582=item savepvn
2583
2584Copy a string to a safe spot. The C<len> indicates number of bytes to
2585copy. This does not use an SV.
2586
08105a92 2587 char* savepvn (const char* sv, I32 len)
cb1a09d0
AD
2588
2589=item SAVETMPS
2590
2591Opening bracket for temporaries on a callback. See C<FREETMPS> and
2592L<perlcall>.
2593
2594 SAVETMPS;
2595
2596=item SP
2597
2598Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2599C<SPAGAIN>.
2600
2601=item SPAGAIN
2602
54310121 2603Refetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
2604
2605 SPAGAIN;
2606
2607=item ST
2608
2609Used to access elements on the XSUB's stack.
2610
e89caa19 2611 SV* ST(int x)
cb1a09d0
AD
2612
2613=item strEQ
2614
2615Test two strings to see if they are equal. Returns true or false.
2616
e89caa19 2617 int strEQ( char *s1, char *s2 )
cb1a09d0
AD
2618
2619=item strGE
2620
2621Test two strings to see if the first, C<s1>, is greater than or equal to the
2622second, C<s2>. Returns true or false.
2623
e89caa19 2624 int strGE( char *s1, char *s2 )
cb1a09d0
AD
2625
2626=item strGT
2627
2628Test two strings to see if the first, C<s1>, is greater than the second,
2629C<s2>. Returns true or false.
2630
e89caa19 2631 int strGT( char *s1, char *s2 )
cb1a09d0
AD
2632
2633=item strLE
2634
2635Test two strings to see if the first, C<s1>, is less than or equal to the
2636second, C<s2>. Returns true or false.
2637
e89caa19 2638 int strLE( char *s1, char *s2 )
cb1a09d0
AD
2639
2640=item strLT
2641
2642Test two strings to see if the first, C<s1>, is less than the second,
2643C<s2>. Returns true or false.
2644
e89caa19 2645 int strLT( char *s1, char *s2 )
cb1a09d0
AD
2646
2647=item strNE
2648
2649Test two strings to see if they are different. Returns true or false.
2650
e89caa19 2651 int strNE( char *s1, char *s2 )
cb1a09d0
AD
2652
2653=item strnEQ
2654
2655Test two strings to see if they are equal. The C<len> parameter indicates
2656the number of bytes to compare. Returns true or false.
2657
e89caa19 2658 int strnEQ( char *s1, char *s2 )
cb1a09d0
AD
2659
2660=item strnNE
2661
2662Test two strings to see if they are different. The C<len> parameter
2663indicates the number of bytes to compare. Returns true or false.
2664
e89caa19 2665 int strnNE( char *s1, char *s2, int len )
cb1a09d0
AD
2666
2667=item sv_2mortal
2668
2669Marks an SV as mortal. The SV will be destroyed when the current context
2670ends.
2671
ef50df4b 2672 SV* sv_2mortal (SV* sv)
cb1a09d0
AD
2673
2674=item sv_bless
2675
2676Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
2677must be designated by its stash (see C<gv_stashpv()>). The reference count
2678of the SV is unaffected.
cb1a09d0 2679
ef50df4b 2680 SV* sv_bless (SV* sv, HV* stash)
cb1a09d0 2681
ef50df4b 2682=item sv_catpv
189b2af5 2683
ef50df4b
GS
2684Concatenates the string onto the end of the string which is in the SV.
2685Handles 'get' magic, but not 'set' magic. See C<sv_catpv_mg>.
189b2af5 2686
08105a92 2687 void sv_catpv (SV* sv, const char* ptr)
189b2af5 2688
ef50df4b 2689=item sv_catpv_mg
cb1a09d0 2690
ef50df4b 2691Like C<sv_catpv>, but also handles 'set' magic.
cb1a09d0 2692
08105a92 2693 void sv_catpvn (SV* sv, const char* ptr)
cb1a09d0
AD
2694
2695=item sv_catpvn
2696
2697Concatenates the string onto the end of the string which is in the SV. The
189b2af5 2698C<len> indicates number of bytes to copy. Handles 'get' magic, but not
ef50df4b 2699'set' magic. See C<sv_catpvn_mg>.
cb1a09d0 2700
08105a92 2701 void sv_catpvn (SV* sv, const char* ptr, STRLEN len)
ef50df4b
GS
2702
2703=item sv_catpvn_mg
2704
2705Like C<sv_catpvn>, but also handles 'set' magic.
2706
08105a92 2707 void sv_catpvn_mg (SV* sv, const char* ptr, STRLEN len)
cb1a09d0 2708
46fc3d4c
PP
2709=item sv_catpvf
2710
2711Processes its arguments like C<sprintf> and appends the formatted output
189b2af5
GS
2712to an SV. Handles 'get' magic, but not 'set' magic. C<SvSETMAGIC()> must
2713typically be called after calling this function to handle 'set' magic.
46fc3d4c 2714
ef50df4b
GS
2715 void sv_catpvf (SV* sv, const char* pat, ...)
2716
2717=item sv_catpvf_mg
2718
2719Like C<sv_catpvf>, but also handles 'set' magic.
2720
2721 void sv_catpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 2722
cb1a09d0
AD
2723=item sv_catsv
2724
5fb8527f 2725Concatenates the string from SV C<ssv> onto the end of the string in SV
ef50df4b
GS
2726C<dsv>. Handles 'get' magic, but not 'set' magic. See C<sv_catsv_mg>.
2727
2728 void sv_catsv (SV* dsv, SV* ssv)
2729
2730=item sv_catsv_mg
cb1a09d0 2731
ef50df4b
GS
2732Like C<sv_catsv>, but also handles 'set' magic.
2733
2734 void sv_catsv_mg (SV* dsv, SV* ssv)
cb1a09d0 2735
e89caa19
GA
2736=item sv_chop
2737
2738Efficient removal of characters from the beginning of the string
2739buffer. SvPOK(sv) must be true and the C<ptr> must be a pointer to
2740somewhere inside the string buffer. The C<ptr> becomes the first
2741character of the adjusted string.
2742
08105a92 2743 void sv_chop(SV* sv, const char *ptr)
e89caa19
GA
2744
2745
5fb8527f
PP
2746=item sv_cmp
2747
2748Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2749string in C<sv1> is less than, equal to, or greater than the string in
2750C<sv2>.
2751
ef50df4b 2752 I32 sv_cmp (SV* sv1, SV* sv2)
5fb8527f 2753
cb1a09d0
AD
2754=item SvCUR
2755
2756Returns the length of the string which is in the SV. See C<SvLEN>.
2757
e89caa19 2758 int SvCUR (SV* sv)
cb1a09d0
AD
2759
2760=item SvCUR_set
2761
2762Set the length of the string which is in the SV. See C<SvCUR>.
2763
08105a92 2764 void SvCUR_set (SV* sv, int val)
cb1a09d0 2765
5fb8527f
PP
2766=item sv_dec
2767
5f05dabc 2768Auto-decrement of the value in the SV.
5fb8527f 2769
ef50df4b 2770 void sv_dec (SV* sv)
5fb8527f 2771
e89caa19
GA
2772=item sv_derived_from
2773
9abd00ed
GS
2774Returns a boolean indicating whether the SV is derived from the specified
2775class. This is the function that implements C<UNIVERSAL::isa>. It works
2776for class names as well as for objects.
2777
20ce7b12 2778 bool sv_derived_from (SV* sv, const char* name);
9abd00ed 2779
cb1a09d0
AD
2780=item SvEND
2781
2782Returns a pointer to the last character in the string which is in the SV.
2783See C<SvCUR>. Access the character as
2784
e89caa19 2785 char* SvEND(sv)
cb1a09d0 2786
5fb8527f
PP
2787=item sv_eq
2788
2789Returns a boolean indicating whether the strings in the two SVs are
2790identical.
2791
ef50df4b 2792 I32 sv_eq (SV* sv1, SV* sv2)
5fb8527f 2793
189b2af5
GS
2794=item SvGETMAGIC
2795
2796Invokes C<mg_get> on an SV if it has 'get' magic. This macro evaluates
2797its argument more than once.
2798
08105a92 2799 void SvGETMAGIC(SV *sv)
189b2af5 2800
cb1a09d0
AD
2801=item SvGROW
2802
e89caa19
GA
2803Expands the character buffer in the SV so that it has room for the
2804indicated number of bytes (remember to reserve space for an extra
2805trailing NUL character). Calls C<sv_grow> to perform the expansion if
2806necessary. Returns a pointer to the character buffer.
cb1a09d0 2807
08105a92 2808 char* SvGROW(SV* sv, STRLEN len)
cb1a09d0 2809
5fb8527f
PP
2810=item sv_grow
2811
2812Expands the character buffer in the SV. This will use C<sv_unref> and will
2813upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2814Use C<SvGROW>.
2815
2816=item sv_inc
2817
07fa94a1 2818Auto-increment of the value in the SV.
5fb8527f 2819
ef50df4b 2820 void sv_inc (SV* sv)
5fb8527f 2821
e89caa19
GA
2822=item sv_insert
2823
2824Inserts a string at the specified offset/length within the SV.
2825Similar to the Perl substr() function.
2826
2827 void sv_insert(SV *sv, STRLEN offset, STRLEN len,
2828 char *str, STRLEN strlen)
2829
cb1a09d0
AD
2830=item SvIOK
2831
2832Returns a boolean indicating whether the SV contains an integer.
2833
e89caa19 2834 int SvIOK (SV* SV)
cb1a09d0
AD
2835
2836=item SvIOK_off
2837
2838Unsets the IV status of an SV.
2839
e89caa19 2840 void SvIOK_off (SV* sv)
cb1a09d0
AD
2841
2842=item SvIOK_on
2843
2844Tells an SV that it is an integer.
2845
e89caa19 2846 void SvIOK_on (SV* sv)
cb1a09d0 2847
5fb8527f
PP
2848=item SvIOK_only
2849
2850Tells an SV that it is an integer and disables all other OK bits.
2851
e89caa19 2852 void SvIOK_only (SV* sv)
5fb8527f 2853
cb1a09d0
AD
2854=item SvIOKp
2855
2856Returns a boolean indicating whether the SV contains an integer. Checks the
2857B<private> setting. Use C<SvIOK>.
2858
e89caa19 2859 int SvIOKp (SV* SV)
cb1a09d0
AD
2860
2861=item sv_isa
2862
2863Returns a boolean indicating whether the SV is blessed into the specified
9abd00ed 2864class. This does not check for subtypes; use C<sv_derived_from> to verify
cb1a09d0
AD
2865an inheritance relationship.
2866
ef50df4b 2867 int sv_isa (SV* sv, char* name)
cb1a09d0 2868
cb1a09d0
AD
2869=item sv_isobject
2870
2871Returns a boolean indicating whether the SV is an RV pointing to a blessed
2872object. If the SV is not an RV, or if the object is not blessed, then this
2873will return false.
2874
ef50df4b 2875 int sv_isobject (SV* sv)
cb1a09d0 2876
e89caa19
GA
2877=item SvIV
2878
5c68b227 2879Coerces the given SV to an integer and returns it.
e89caa19 2880
9abd00ed 2881 int SvIV (SV* sv)
a59f3522 2882
cb1a09d0
AD
2883=item SvIVX
2884
5c68b227 2885Returns the integer which is stored in the SV, assuming SvIOK is true.
cb1a09d0 2886
e89caa19 2887 int SvIVX (SV* sv)
cb1a09d0
AD
2888
2889=item SvLEN
2890
2891Returns the size of the string buffer in the SV. See C<SvCUR>.
2892
e89caa19 2893 int SvLEN (SV* sv)
cb1a09d0 2894
5fb8527f
PP
2895=item sv_len
2896
2897Returns the length of the string in the SV. Use C<SvCUR>.
2898
ef50df4b 2899 STRLEN sv_len (SV* sv)
5fb8527f 2900
cb1a09d0
AD
2901=item sv_magic
2902
2903Adds magic to an SV.
2904
08105a92 2905 void sv_magic (SV* sv, SV* obj, int how, const char* name, I32 namlen)
cb1a09d0
AD
2906
2907=item sv_mortalcopy
2908
2909Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 2910as mortal.
cb1a09d0 2911
ef50df4b 2912 SV* sv_mortalcopy (SV* oldsv)
cb1a09d0 2913
cb1a09d0
AD
2914=item sv_newmortal
2915
5f05dabc 2916Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0 2917
ef50df4b 2918 SV* sv_newmortal (void)
cb1a09d0 2919
cb1a09d0
AD
2920=item SvNIOK
2921
2922Returns a boolean indicating whether the SV contains a number, integer or
2923double.
2924
e89caa19 2925 int SvNIOK (SV* SV)
cb1a09d0
AD
2926
2927=item SvNIOK_off
2928
2929Unsets the NV/IV status of an SV.
2930
e89caa19 2931 void SvNIOK_off (SV* sv)
cb1a09d0
AD
2932
2933=item SvNIOKp
2934
2935Returns a boolean indicating whether the SV contains a number, integer or
2936double. Checks the B<private> setting. Use C<SvNIOK>.
2937
e89caa19
GA
2938 int SvNIOKp (SV* SV)
2939
9cde0e7f 2940=item PL_sv_no
e89caa19 2941
9cde0e7f 2942This is the C<false> SV. See C<PL_sv_yes>. Always refer to this as C<&PL_sv_no>.
cb1a09d0
AD
2943
2944=item SvNOK
2945
2946Returns a boolean indicating whether the SV contains a double.
2947
e89caa19 2948 int SvNOK (SV* SV)
cb1a09d0
AD
2949
2950=item SvNOK_off
2951
2952Unsets the NV status of an SV.
2953
e89caa19 2954 void SvNOK_off (SV* sv)
cb1a09d0
AD
2955
2956=item SvNOK_on
2957
2958Tells an SV that it is a double.
2959
e89caa19 2960 void SvNOK_on (SV* sv)
cb1a09d0 2961
5fb8527f
PP
2962=item SvNOK_only
2963
2964Tells an SV that it is a double and disables all other OK bits.
2965
e89caa19 2966 void SvNOK_only (SV* sv)
5fb8527f 2967
cb1a09d0
AD
2968=item SvNOKp
2969
2970Returns a boolean indicating whether the SV contains a double. Checks the
2971B<private> setting. Use C<SvNOK>.
2972
e89caa19 2973 int SvNOKp (SV* SV)
cb1a09d0
AD
2974
2975=item SvNV
2976
5c68b227 2977Coerce the given SV to a double and return it.
cb1a09d0 2978
e89caa19 2979 double SvNV (SV* sv)
cb1a09d0
AD
2980
2981=item SvNVX
2982
5c68b227 2983Returns the double which is stored in the SV, assuming SvNOK is true.
cb1a09d0 2984
e89caa19
GA
2985 double SvNVX (SV* sv)
2986
2987=item SvOK
2988
2989Returns a boolean indicating whether the value is an SV.
2990
2991 int SvOK (SV* sv)
2992
2993=item SvOOK
2994
2995Returns a boolean indicating whether the SvIVX is a valid offset value
2996for the SvPVX. This hack is used internally to speed up removal of
2997characters from the beginning of a SvPV. When SvOOK is true, then the
2998start of the allocated string buffer is really (SvPVX - SvIVX).
2999
9cde0e7f 3000 int SvOOK(SV* sv)
cb1a09d0
AD
3001
3002=item SvPOK
3003
3004Returns a boolean indicating whether the SV contains a character string.
3005
e89caa19 3006 int SvPOK (SV* SV)
cb1a09d0
AD
3007
3008=item SvPOK_off
3009
3010Unsets the PV status of an SV.
3011
e89caa19 3012 void SvPOK_off (SV* sv)
cb1a09d0
AD
3013
3014=item SvPOK_on
3015
3016Tells an SV that it is a string.
3017
e89caa19 3018 void SvPOK_on (SV* sv)
cb1a09d0 3019
5fb8527f
PP
3020=item SvPOK_only
3021
3022Tells an SV that it is a string and disables all other OK bits.
3023
e89caa19 3024 void SvPOK_only (SV* sv)
5fb8527f 3025
cb1a09d0
AD
3026=item SvPOKp
3027
3028Returns a boolean indicating whether the SV contains a character string.
3029Checks the B<private> setting. Use C<SvPOK>.
3030
e89caa19 3031 int SvPOKp (SV* SV)
cb1a09d0
AD
3032
3033=item SvPV
3034
3035Returns a pointer to the string in the SV, or a stringified form of the SV
2d8e6c8d 3036if the SV does not contain a string. Handles 'get' magic.
cb1a09d0 3037
e65f3abd 3038 char* SvPV (SV* sv, STRLEN len)
e89caa19
GA
3039
3040=item SvPV_force
3041
3042Like <SvPV> but will force the SV into becoming a string (SvPOK). You
3043want force if you are going to update the SvPVX directly.
3044
e65f3abd 3045 char* SvPV_force(SV* sv, STRLEN len)
e89caa19 3046
1fa8b10d
JD
3047=item SvPV_nolen
3048
3049Returns a pointer to the string in the SV, or a stringified form of the SV
3050if the SV does not contain a string. Handles 'get' magic.
3051
e65f3abd 3052 char* SvPV_nolen (SV* sv)
cb1a09d0
AD
3053
3054=item SvPVX
3055
3056Returns a pointer to the string in the SV. The SV must contain a string.
3057
e89caa19 3058 char* SvPVX (SV* sv)
cb1a09d0
AD
3059
3060=item SvREFCNT
3061
5f05dabc 3062Returns the value of the object's reference count.
cb1a09d0 3063
e89caa19 3064 int SvREFCNT (SV* sv)
cb1a09d0
AD
3065
3066=item SvREFCNT_dec
3067
5f05dabc 3068Decrements the reference count of the given SV.
cb1a09d0 3069
e89caa19 3070 void SvREFCNT_dec (SV* sv)
cb1a09d0
AD
3071
3072=item SvREFCNT_inc
3073
5f05dabc 3074Increments the reference count of the given SV.
cb1a09d0 3075
e89caa19 3076 void SvREFCNT_inc (SV* sv)
cb1a09d0
AD
3077
3078=item SvROK
3079
3080Tests if the SV is an RV.
3081
e89caa19 3082 int SvROK (SV* sv)
cb1a09d0
AD
3083
3084=item SvROK_off
3085
3086Unsets the RV status of an SV.
3087
e89caa19 3088 void SvROK_off (SV* sv)
cb1a09d0
AD
3089
3090=item SvROK_on
3091
3092Tells an SV that it is an RV.
3093
e89caa19 3094 void SvROK_on (SV* sv)
cb1a09d0
AD
3095
3096=item SvRV
3097
3098Dereferences an RV to return the SV.
3099
ef50df4b 3100 SV* SvRV (SV* sv)
cb1a09d0 3101
189b2af5
GS
3102=item SvSETMAGIC
3103
3104Invokes C<mg_set> on an SV if it has 'set' magic. This macro evaluates
3105its argument more than once.
3106
3107 void SvSETMAGIC( SV *sv )
3108
ef50df4b 3109=item sv_setiv
189b2af5 3110
ef50df4b
GS
3111Copies an integer into the given SV. Does not handle 'set' magic.
3112See C<sv_setiv_mg>.
189b2af5 3113
ef50df4b 3114 void sv_setiv (SV* sv, IV num)
189b2af5 3115
ef50df4b 3116=item sv_setiv_mg
189b2af5 3117
ef50df4b 3118Like C<sv_setiv>, but also handles 'set' magic.
189b2af5 3119
ef50df4b 3120 void sv_setiv_mg (SV* sv, IV num)
189b2af5 3121
ef50df4b 3122=item sv_setnv
189b2af5 3123
ef50df4b
GS
3124Copies a double into the given SV. Does not handle 'set' magic.
3125See C<sv_setnv_mg>.
189b2af5 3126
ef50df4b 3127 void sv_setnv (SV* sv, double num)
189b2af5 3128
ef50df4b 3129=item sv_setnv_mg
189b2af5 3130
ef50df4b 3131Like C<sv_setnv>, but also handles 'set' magic.
189b2af5 3132
ef50df4b 3133 void sv_setnv_mg (SV* sv, double num)
189b2af5 3134
ef50df4b 3135=item sv_setpv
189b2af5 3136
ef50df4b
GS
3137Copies a string into an SV. The string must be null-terminated.
3138Does not handle 'set' magic. See C<sv_setpv_mg>.
189b2af5 3139
08105a92 3140 void sv_setpv (SV* sv, const char* ptr)
189b2af5 3141
ef50df4b 3142=item sv_setpv_mg
189b2af5 3143
ef50df4b 3144Like C<sv_setpv>, but also handles 'set' magic.
189b2af5 3145
08105a92 3146 void sv_setpv_mg (SV* sv, const char* ptr)
189b2af5 3147
ef50df4b 3148=item sv_setpviv
cb1a09d0 3149
ef50df4b
GS
3150Copies an integer into the given SV, also updating its string value.
3151Does not handle 'set' magic. See C<sv_setpviv_mg>.
cb1a09d0 3152
ef50df4b 3153 void sv_setpviv (SV* sv, IV num)
cb1a09d0 3154
ef50df4b 3155=item sv_setpviv_mg
cb1a09d0 3156
ef50df4b 3157Like C<sv_setpviv>, but also handles 'set' magic.
cb1a09d0 3158
ef50df4b 3159 void sv_setpviv_mg (SV* sv, IV num)
cb1a09d0 3160
ef50df4b 3161=item sv_setpvn
cb1a09d0 3162
ef50df4b
GS
3163Copies a string into an SV. The C<len> parameter indicates the number of
3164bytes to be copied. Does not handle 'set' magic. See C<sv_setpvn_mg>.
cb1a09d0 3165
08105a92 3166 void sv_setpvn (SV* sv, const char* ptr, STRLEN len)
cb1a09d0 3167
ef50df4b 3168=item sv_setpvn_mg
189b2af5 3169
ef50df4b 3170Like C<sv_setpvn>, but also handles 'set' magic.
189b2af5 3171
08105a92 3172 void sv_setpvn_mg (SV* sv, const char* ptr, STRLEN len)
189b2af5 3173
ef50df4b 3174=item sv_setpvf
cb1a09d0 3175
ef50df4b
GS
3176Processes its arguments like C<sprintf> and sets an SV to the formatted
3177output. Does not handle 'set' magic. See C<sv_setpvf_mg>.
cb1a09d0 3178
ef50df4b 3179 void sv_setpvf (SV* sv, const char* pat, ...)
cb1a09d0 3180
ef50df4b 3181=item sv_setpvf_mg
46fc3d4c 3182
ef50df4b 3183Like C<sv_setpvf>, but also handles 'set' magic.
46fc3d4c 3184
ef50df4b 3185 void sv_setpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 3186
cb1a09d0
AD
3187=item sv_setref_iv
3188
5fb8527f
PP
3189Copies an integer into a new SV, optionally blessing the SV. The C<rv>
3190argument will be upgraded to an RV. That RV will be modified to point to
3191the new SV. The C<classname> argument indicates the package for the
3192blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3193will be returned and will have a reference count of 1.
cb1a09d0 3194
ef50df4b 3195 SV* sv_setref_iv (SV *rv, char *classname, IV iv)
cb1a09d0
AD
3196
3197=item sv_setref_nv
3198
5fb8527f
PP
3199Copies a double into a new SV, optionally blessing the SV. The C<rv>
3200argument will be upgraded to an RV. That RV will be modified to point to
3201the new SV. The C<classname> argument indicates the package for the
3202blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3203will be returned and will have a reference count of 1.
cb1a09d0 3204
ef50df4b 3205 SV* sv_setref_nv (SV *rv, char *classname, double nv)
cb1a09d0
AD
3206
3207=item sv_setref_pv
3208
5fb8527f
PP
3209Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
3210argument will be upgraded to an RV. That RV will be modified to point to
9cde0e7f 3211the new SV. If the C<pv> argument is NULL then C<PL_sv_undef> will be placed
5fb8527f
PP
3212into the SV. The C<classname> argument indicates the package for the
3213blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3214will be returned and will have a reference count of 1.
cb1a09d0 3215
ef50df4b 3216 SV* sv_setref_pv (SV *rv, char *classname, void* pv)
cb1a09d0
AD
3217
3218Do not use with integral Perl types such as HV, AV, SV, CV, because those
3219objects will become corrupted by the pointer copy process.
3220
3221Note that C<sv_setref_pvn> copies the string while this copies the pointer.
3222
3223=item sv_setref_pvn
3224
5fb8527f
PP
3225Copies a string into a new SV, optionally blessing the SV. The length of the
3226string must be specified with C<n>. The C<rv> argument will be upgraded to
3227an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
3228argument indicates the package for the blessing. Set C<classname> to
3229C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 3230a reference count of 1.
cb1a09d0 3231
ef50df4b 3232 SV* sv_setref_pvn (SV *rv, char *classname, char* pv, I32 n)
cb1a09d0
AD
3233
3234Note that C<sv_setref_pv> copies the pointer while this copies the string.
3235
189b2af5
GS
3236=item SvSetSV
3237
3238Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
3239more than once.
3240
3241 void SvSetSV (SV* dsv, SV* ssv)
3242
3243=item SvSetSV_nosteal
3244
3245Calls a non-destructive version of C<sv_setsv> if dsv is not the same as ssv.
3246May evaluate arguments more than once.
3247
3248 void SvSetSV_nosteal (SV* dsv, SV* ssv)
3249
cb1a09d0
AD
3250=item sv_setsv
3251
3252Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
189b2af5 3253The source SV may be destroyed if it is mortal. Does not handle 'set' magic.
ef50df4b
GS
3254See the macro forms C<SvSetSV>, C<SvSetSV_nosteal> and C<sv_setsv_mg>.
3255
3256 void sv_setsv (SV* dsv, SV* ssv)
3257
3258=item sv_setsv_mg
3259
3260Like C<sv_setsv>, but also handles 'set' magic.
cb1a09d0 3261
ef50df4b 3262 void sv_setsv_mg (SV* dsv, SV* ssv)
cb1a09d0 3263
189b2af5
GS
3264=item sv_setuv
3265
3266Copies an unsigned integer into the given SV. Does not handle 'set' magic.
ef50df4b 3267See C<sv_setuv_mg>.
189b2af5 3268
ef50df4b
GS
3269 void sv_setuv (SV* sv, UV num)
3270
3271=item sv_setuv_mg
3272
3273Like C<sv_setuv>, but also handles 'set' magic.
3274
3275 void sv_setuv_mg (SV* sv, UV num)
189b2af5 3276
cb1a09d0
AD
3277=item SvSTASH
3278
3279Returns the stash of the SV.
3280
e89caa19
GA
3281 HV* SvSTASH (SV* sv)
3282
3283=item SvTAINT
3284
3285Taints an SV if tainting is enabled
3286
3287 void SvTAINT (SV* sv)
3288
3289=item SvTAINTED
3290
3291Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.
3292
3293 int SvTAINTED (SV* sv)
3294
3295=item SvTAINTED_off
3296
3297Untaints an SV. Be I<very> careful with this routine, as it short-circuits
3298some of Perl's fundamental security features. XS module authors should
3299not use this function unless they fully understand all the implications
3300of unconditionally untainting the value. Untainting should be done in
3301the standard perl fashion, via a carefully crafted regexp, rather than
3302directly untainting variables.
3303
3304 void SvTAINTED_off (SV* sv)
3305
3306=item SvTAINTED_on
3307
3308Marks an SV as tainted.
3309
3310 void SvTAINTED_on (SV* sv)
cb1a09d0
AD
3311
3312=item SVt_IV
3313
3314Integer type flag for scalars. See C<svtype>.
3315
3316=item SVt_PV
3317
3318Pointer type flag for scalars. See C<svtype>.
3319
3320=item SVt_PVAV
3321
3322Type flag for arrays. See C<svtype>.
3323
3324=item SVt_PVCV
3325
3326Type flag for code refs. See C<svtype>.
3327
3328=item SVt_PVHV
3329
3330Type flag for hashes. See C<svtype>.
3331
3332=item SVt_PVMG
3333
3334Type flag for blessed scalars. See C<svtype>.
3335
3336=item SVt_NV
3337
3338Double type flag for scalars. See C<svtype>.
3339
3340=item SvTRUE
3341
3342Returns a boolean indicating whether Perl would evaluate the SV as true or
189b2af5 3343false, defined or undefined. Does not handle 'get' magic.
cb1a09d0 3344
e89caa19 3345 int SvTRUE (SV* sv)
cb1a09d0
AD
3346
3347=item SvTYPE
3348
3349Returns the type of the SV. See C<svtype>.
3350
3351 svtype SvTYPE (SV* sv)
3352
3353=item svtype
3354
3355An enum of flags for Perl types. These are found in the file B<sv.h> in the
3356C<svtype> enum. Test these flags with the C<SvTYPE> macro.
3357
9cde0e7f 3358=item PL_sv_undef
cb1a09d0 3359
9cde0e7f 3360This is the C<undef> SV. Always refer to this as C<&PL_sv_undef>.
cb1a09d0 3361
5fb8527f
PP
3362=item sv_unref
3363
07fa94a1
JO
3364Unsets the RV status of the SV, and decrements the reference count of
3365whatever was being referenced by the RV. This can almost be thought of
3366as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f 3367
ef50df4b 3368 void sv_unref (SV* sv)
189b2af5 3369
e89caa19
GA
3370=item SvUPGRADE
3371
3372Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
3373the upgrade if necessary. See C<svtype>.
3374
3375 bool SvUPGRADE (SV* sv, svtype mt)
3376
3377=item sv_upgrade
3378
3379Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
3380
cb1a09d0
AD
3381=item sv_usepvn
3382
3383Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
3384stored inside the SV but sv_usepvn allows the SV to use an outside string.
3385The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
3386string length, C<len>, must be supplied. This function will realloc the
3387memory pointed to by C<ptr>, so that pointer should not be freed or used by
189b2af5 3388the programmer after giving it to sv_usepvn. Does not handle 'set' magic.
ef50df4b
GS
3389See C<sv_usepvn_mg>.
3390
3391 void sv_usepvn (SV* sv, char* ptr, STRLEN len)
3392
3393=item sv_usepvn_mg
3394
3395Like C<sv_usepvn>, but also handles 'set' magic.
cb1a09d0 3396
ef50df4b 3397 void sv_usepvn_mg (SV* sv, char* ptr, STRLEN len)
cb1a09d0 3398
9abd00ed
GS
3399=item sv_vcatpvfn(sv, pat, patlen, args, svargs, svmax, used_locale)
3400
3401Processes its arguments like C<vsprintf> and appends the formatted output
3402to an SV. Uses an array of SVs if the C style variable argument list is
3403missing (NULL). Indicates if locale information has been used for formatting.
3404
20ce7b12
GS
3405 void sv_catpvfn (SV* sv, const char* pat, STRLEN patlen,
3406 va_list *args, SV **svargs, I32 svmax,
3407 bool *used_locale);
9abd00ed
GS
3408
3409=item sv_vsetpvfn(sv, pat, patlen, args, svargs, svmax, used_locale)
3410
3411Works like C<vcatpvfn> but copies the text into the SV instead of
3412appending it.
3413
20ce7b12
GS
3414 void sv_setpvfn (SV* sv, const char* pat, STRLEN patlen,
3415 va_list *args, SV **svargs, I32 svmax,
3416 bool *used_locale);
9abd00ed 3417
e89caa19
GA
3418=item SvUV
3419
5c68b227 3420Coerces the given SV to an unsigned integer and returns it.
e89caa19
GA
3421
3422 UV SvUV(SV* sv)
3423
3424=item SvUVX
3425
5c68b227 3426Returns the unsigned integer which is stored in the SV, assuming SvIOK is true.
e89caa19
GA
3427
3428 UV SvUVX(SV* sv)
3429
9cde0e7f 3430=item PL_sv_yes
cb1a09d0 3431
9cde0e7f 3432This is the C<true> SV. See C<PL_sv_no>. Always refer to this as C<&PL_sv_yes>.
cb1a09d0
AD
3433
3434=item THIS
3435
3436Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
3437This is always the proper type for the C++ object. See C<CLASS> and
5fb8527f 3438L<perlxs/"Using XS With C++">.
cb1a09d0
AD
3439
3440=item toLOWER
3441
3442Converts the specified character to lowercase.
3443
e89caa19 3444 int toLOWER (char c)
cb1a09d0
AD
3445
3446=item toUPPER
3447
3448Converts the specified character to uppercase.
3449
e89caa19 3450 int toUPPER (char c)
cb1a09d0
AD
3451
3452=item warn
3453
3454This is the XSUB-writer's interface to Perl's C<warn> function. Use this
3455function the same way you use the C C<printf> function. See C<croak()>.
3456
3457=item XPUSHi
3458
189b2af5
GS
3459Push an integer onto the stack, extending the stack if necessary. Handles
3460'set' magic. See C<PUSHi>.
cb1a09d0
AD
3461
3462 XPUSHi(int d)
3463
3464=item XPUSHn
3465
189b2af5
GS
3466Push a double onto the stack, extending the stack if necessary. Handles 'set'
3467magic. See C<PUSHn>.
cb1a09d0
AD
3468
3469 XPUSHn(double d)
3470
3471=item XPUSHp
3472
3473Push a string onto the stack, extending the stack if necessary. The C<len>
189b2af5 3474indicates the length of the string. Handles 'set' magic. See C<PUSHp>.
cb1a09d0
AD
3475
3476 XPUSHp(char *c, int len)
3477
3478=item XPUSHs
3479
189b2af5
GS
3480Push an SV onto the stack, extending the stack if necessary. Does not
3481handle 'set' magic. See C<PUSHs>.
cb1a09d0
AD
3482
3483 XPUSHs(sv)
3484
e89caa19
GA
3485=item XPUSHu
3486
3487Push an unsigned integer onto the stack, extending the stack if
3488necessary. See C<PUSHu>.
3489
5fb8527f
PP
3490=item XS
3491
3492Macro to declare an XSUB and its C parameter list. This is handled by
3493C<xsubpp>.
3494
cb1a09d0
AD
3495=item XSRETURN
3496
3497Return from XSUB, indicating number of items on the stack. This is usually
3498handled by C<xsubpp>.
3499
ef50df4b 3500 XSRETURN(int x)
cb1a09d0
AD
3501
3502=item XSRETURN_EMPTY
3503
5fb8527f 3504Return an empty list from an XSUB immediately.
cb1a09d0
AD
3505
3506 XSRETURN_EMPTY;
3507
5fb8527f
PP
3508=item XSRETURN_IV
3509
3510Return an integer from an XSUB immediately. Uses C<XST_mIV>.
3511
ef50df4b 3512 XSRETURN_IV(IV v)
5fb8527f 3513
cb1a09d0
AD
3514=item XSRETURN_NO
3515
9cde0e7f 3516Return C<&PL_sv_no> from an XSUB immediately. Uses C<XST_mNO>.
cb1a09d0
AD
3517
3518 XSRETURN_NO;
3519
5fb8527f
PP
3520=item XSRETURN_NV
3521
3522Return an double from an XSUB immediately. Uses C<XST_mNV>.
3523
ef50df4b 3524 XSRETURN_NV(NV v)
5fb8527f
PP
3525
3526=item XSRETURN_PV
3527
3528Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
3529
ef50df4b 3530 XSRETURN_PV(char *v)
5fb8527f 3531
cb1a09d0
AD
3532=item XSRETURN_UNDEF
3533
9cde0e7f 3534Return C<&PL_sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
cb1a09d0
AD
3535
3536 XSRETURN_UNDEF;
3537
3538=item XSRETURN_YES
3539
9cde0e7f 3540Return C<&PL_sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
cb1a09d0
AD
3541
3542 XSRETURN_YES;
3543
5fb8527f
PP
3544=item XST_mIV
3545
3546Place an integer into the specified position C<i> on the stack. The value is
3547stored in a new mortal SV.
3548
ef50df4b 3549 XST_mIV( int i, IV v )
5fb8527f
PP
3550
3551=item XST_mNV
3552
3553Place a double into the specified position C<i> on the stack. The value is
3554stored in a new mortal SV.
3555
ef50df4b 3556 XST_mNV( int i, NV v )
5fb8527f
PP
3557
3558=item XST_mNO
3559
9cde0e7f 3560Place C<&PL_sv_no> into the specified position C<i> on the stack.
5fb8527f 3561
ef50df4b 3562 XST_mNO( int i )
5fb8527f
PP
3563
3564=item XST_mPV
3565
3566Place a copy of a string into the specified position C<i> on the stack. The
3567value is stored in a new mortal SV.
3568
ef50df4b 3569 XST_mPV( int i, char *v )
5fb8527f
PP
3570
3571=item XST_mUNDEF
3572
9cde0e7f 3573Place C<&PL_sv_undef> into the specified position C<i> on the stack.
5fb8527f 3574
ef50df4b 3575 XST_mUNDEF( int i )
5fb8527f
PP
3576
3577=item XST_mYES
3578
9cde0e7f 3579Place C<&PL_sv_yes> into the specified position C<i> on the stack.
5fb8527f 3580
ef50df4b 3581 XST_mYES( int i )
5fb8527f
PP
3582
3583=item XS_VERSION
3584
3585The version identifier for an XS module. This is usually handled
3586automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
3587
3588=item XS_VERSION_BOOTCHECK
3589
3590Macro to verify that a PM module's $VERSION variable matches the XS module's
3591C<XS_VERSION> variable. This is usually handled automatically by
3592C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
3593
cb1a09d0
AD
3594=item Zero
3595
3596The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
3597destination, C<n> is the number of items, and C<t> is the type.
3598
e89caa19 3599 void Zero( d, n, t )
cb1a09d0
AD
3600
3601=back
3602
9cecd9f2 3603=head1 AUTHORS
cb1a09d0 3604
9cecd9f2
GA
3605Until May 1997, this document was maintained by Jeff Okamoto
3606<okamoto@corp.hp.com>. It is now maintained as part of Perl itself.
cb1a09d0
AD
3607
3608With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
3609Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil