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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);
41 SV* newSVpv(char*, int);
9da1e3b5 42 SV* newSVpvn(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);
a0d0e21e 51 void sv_setpv(SV*, char*);
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52 void sv_setpvn(SV*, char*, int)
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
71the string, and the string's contents are therefore untrustworty (see
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)
92
93which will automatically coerce the actual scalar type into an IV, double,
94or string.
95
96In the C<SvPV> macro, the length of the string returned is placed into the
97variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
9cde0e7f 98care what the length of the data is, use the global variable C<PL_na>. Remember,
a0d0e21e 99however, that Perl allows arbitrary strings of data that may both contain
54310121 100NULs and might not be terminated by a NUL.
a0d0e21e 101
07fa94a1 102If you want to know if the scalar value is TRUE, you can use:
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103
104 SvTRUE(SV*)
105
106Although Perl will automatically grow strings for you, if you need to force
107Perl to allocate more memory for your SV, you can use the macro
108
109 SvGROW(SV*, STRLEN newlen)
110
111which will determine if more memory needs to be allocated. If so, it will
112call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
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113decrease, the allocated memory of an SV and that it does not automatically
114add a byte for the a trailing NUL (perl's own string functions typically do
8ebc5c01 115C<SvGROW(sv, len + 1)>).
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116
117If you have an SV and want to know what kind of data Perl thinks is stored
118in it, you can use the following macros to check the type of SV you have.
119
120 SvIOK(SV*)
121 SvNOK(SV*)
122 SvPOK(SV*)
123
124You can get and set the current length of the string stored in an SV with
125the following macros:
126
127 SvCUR(SV*)
128 SvCUR_set(SV*, I32 val)
129
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130You can also get a pointer to the end of the string stored in the SV
131with the macro:
132
133 SvEND(SV*)
134
135But note that these last three macros are valid only if C<SvPOK()> is true.
a0d0e21e 136
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137If you want to append something to the end of string stored in an C<SV*>,
138you can use the following functions:
139
140 void sv_catpv(SV*, char*);
141 void sv_catpvn(SV*, char*, int);
46fc3d4c 142 void sv_catpvf(SV*, const char*, ...);
9abd00ed 143 void sv_catpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
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144 void sv_catsv(SV*, SV*);
145
146The first function calculates the length of the string to be appended by
147using C<strlen>. In the second, you specify the length of the string
46fc3d4c 148yourself. The third function processes its arguments like C<sprintf> and
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149appends the formatted output. The fourth function works like C<vsprintf>.
150You can specify the address and length of an array of SVs instead of the
151va_list argument. The fifth function extends the string stored in the first
152SV with the string stored in the second SV. It also forces the second SV
153to be interpreted as a string.
154
155The C<sv_cat*()> functions are not generic enough to operate on values that
156have "magic". See L<Magic Virtual Tables> later in this document.
d1b91892 157
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158If you know the name of a scalar variable, you can get a pointer to its SV
159by using the following:
160
5f05dabc 161 SV* perl_get_sv("package::varname", FALSE);
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162
163This returns NULL if the variable does not exist.
164
d1b91892 165If you want to know if this variable (or any other SV) is actually C<defined>,
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166you can call:
167
168 SvOK(SV*)
169
9cde0e7f 170The scalar C<undef> value is stored in an SV instance called C<PL_sv_undef>. Its
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171address can be used whenever an C<SV*> is needed.
172
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173There are also the two values C<PL_sv_yes> and C<PL_sv_no>, which contain Boolean
174TRUE and FALSE values, respectively. Like C<PL_sv_undef>, their addresses can
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175be used whenever an C<SV*> is needed.
176
9cde0e7f 177Do not be fooled into thinking that C<(SV *) 0> is the same as C<&PL_sv_undef>.
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178Take this code:
179
180 SV* sv = (SV*) 0;
181 if (I-am-to-return-a-real-value) {
182 sv = sv_2mortal(newSViv(42));
183 }
184 sv_setsv(ST(0), sv);
185
186This code tries to return a new SV (which contains the value 42) if it should
04343c6d 187return a real value, or undef otherwise. Instead it has returned a NULL
a0d0e21e 188pointer which, somewhere down the line, will cause a segmentation violation,
9cde0e7f 189bus error, or just weird results. Change the zero to C<&PL_sv_undef> in the first
5f05dabc 190line and all will be well.
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191
192To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
3fe9a6f1 193call is not necessary (see L<Reference Counts and Mortality>).
a0d0e21e 194
d1b91892 195=head2 What's Really Stored in an SV?
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196
197Recall that the usual method of determining the type of scalar you have is
5f05dabc 198to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
d1b91892 199usually these macros will always return TRUE and calling the C<Sv*V>
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200macros will do the appropriate conversion of string to integer/double or
201integer/double to string.
202
203If you I<really> need to know if you have an integer, double, or string
204pointer in an SV, you can use the following three macros instead:
205
206 SvIOKp(SV*)
207 SvNOKp(SV*)
208 SvPOKp(SV*)
209
210These will tell you if you truly have an integer, double, or string pointer
d1b91892 211stored in your SV. The "p" stands for private.
a0d0e21e 212
07fa94a1 213In general, though, it's best to use the C<Sv*V> macros.
a0d0e21e 214
54310121 215=head2 Working with AVs
a0d0e21e 216
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217There are two ways to create and load an AV. The first method creates an
218empty AV:
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219
220 AV* newAV();
221
54310121 222The second method both creates the AV and initially populates it with SVs:
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223
224 AV* av_make(I32 num, SV **ptr);
225
5f05dabc 226The second argument points to an array containing C<num> C<SV*>'s. Once the
54310121 227AV has been created, the SVs can be destroyed, if so desired.
a0d0e21e 228
54310121 229Once the AV has been created, the following operations are possible on AVs:
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230
231 void av_push(AV*, SV*);
232 SV* av_pop(AV*);
233 SV* av_shift(AV*);
234 void av_unshift(AV*, I32 num);
235
236These should be familiar operations, with the exception of C<av_unshift>.
237This routine adds C<num> elements at the front of the array with the C<undef>
238value. You must then use C<av_store> (described below) to assign values
239to these new elements.
240
241Here are some other functions:
242
5f05dabc 243 I32 av_len(AV*);
a0d0e21e 244 SV** av_fetch(AV*, I32 key, I32 lval);
a0d0e21e 245 SV** av_store(AV*, I32 key, SV* val);
a0d0e21e 246
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247The C<av_len> function returns the highest index value in array (just
248like $#array in Perl). If the array is empty, -1 is returned. The
249C<av_fetch> function returns the value at index C<key>, but if C<lval>
250is non-zero, then C<av_fetch> will store an undef value at that index.
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251The C<av_store> function stores the value C<val> at index C<key>, and does
252not increment the reference count of C<val>. Thus the caller is responsible
253for taking care of that, and if C<av_store> returns NULL, the caller will
254have to decrement the reference count to avoid a memory leak. Note that
255C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s as their
256return value.
d1b91892 257
a0d0e21e 258 void av_clear(AV*);
a0d0e21e 259 void av_undef(AV*);
cb1a09d0 260 void av_extend(AV*, I32 key);
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261
262The C<av_clear> function deletes all the elements in the AV* array, but
263does not actually delete the array itself. The C<av_undef> function will
264delete all the elements in the array plus the array itself. The
265C<av_extend> function extends the array so that it contains C<key>
266elements. If C<key> is less than the current length of the array, then
267nothing is done.
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268
269If you know the name of an array variable, you can get a pointer to its AV
270by using the following:
271
5f05dabc 272 AV* perl_get_av("package::varname", FALSE);
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273
274This returns NULL if the variable does not exist.
275
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276See L<Understanding the Magic of Tied Hashes and Arrays> for more
277information on how to use the array access functions on tied arrays.
278
54310121 279=head2 Working with HVs
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280
281To create an HV, you use the following routine:
282
283 HV* newHV();
284
54310121 285Once the HV has been created, the following operations are possible on HVs:
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286
287 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
288 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
289
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290The C<klen> parameter is the length of the key being passed in (Note that
291you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
292length of the key). The C<val> argument contains the SV pointer to the
54310121 293scalar being stored, and C<hash> is the precomputed hash value (zero if
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294you want C<hv_store> to calculate it for you). The C<lval> parameter
295indicates whether this fetch is actually a part of a store operation, in
296which case a new undefined value will be added to the HV with the supplied
297key and C<hv_fetch> will return as if the value had already existed.
a0d0e21e 298
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299Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
300C<SV*>. To access the scalar value, you must first dereference the return
301value. However, you should check to make sure that the return value is
302not NULL before dereferencing it.
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303
304These two functions check if a hash table entry exists, and deletes it.
305
306 bool hv_exists(HV*, char* key, U32 klen);
d1b91892 307 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
a0d0e21e 308
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309If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
310create and return a mortal copy of the deleted value.
311
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312And more miscellaneous functions:
313
314 void hv_clear(HV*);
a0d0e21e 315 void hv_undef(HV*);
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316
317Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
318table but does not actually delete the hash table. The C<hv_undef> deletes
319both the entries and the hash table itself.
a0d0e21e 320
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321Perl keeps the actual data in linked list of structures with a typedef of HE.
322These contain the actual key and value pointers (plus extra administrative
323overhead). The key is a string pointer; the value is an C<SV*>. However,
324once you have an C<HE*>, to get the actual key and value, use the routines
325specified below.
326
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327 I32 hv_iterinit(HV*);
328 /* Prepares starting point to traverse hash table */
329 HE* hv_iternext(HV*);
330 /* Get the next entry, and return a pointer to a
331 structure that has both the key and value */
332 char* hv_iterkey(HE* entry, I32* retlen);
333 /* Get the key from an HE structure and also return
334 the length of the key string */
cb1a09d0 335 SV* hv_iterval(HV*, HE* entry);
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336 /* Return a SV pointer to the value of the HE
337 structure */
cb1a09d0 338 SV* hv_iternextsv(HV*, char** key, I32* retlen);
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339 /* This convenience routine combines hv_iternext,
340 hv_iterkey, and hv_iterval. The key and retlen
341 arguments are return values for the key and its
342 length. The value is returned in the SV* argument */
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343
344If you know the name of a hash variable, you can get a pointer to its HV
345by using the following:
346
5f05dabc 347 HV* perl_get_hv("package::varname", FALSE);
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348
349This returns NULL if the variable does not exist.
350
8ebc5c01 351The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
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352
353 i = klen;
354 hash = 0;
355 s = key;
356 while (i--)
357 hash = hash * 33 + *s++;
358
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359See L<Understanding the Magic of Tied Hashes and Arrays> for more
360information on how to use the hash access functions on tied hashes.
361
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362=head2 Hash API Extensions
363
364Beginning with version 5.004, the following functions are also supported:
365
366 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
367 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
368
369 bool hv_exists_ent (HV* tb, SV* key, U32 hash);
370 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
371
372 SV* hv_iterkeysv (HE* entry);
373
374Note that these functions take C<SV*> keys, which simplifies writing
375of extension code that deals with hash structures. These functions
376also allow passing of C<SV*> keys to C<tie> functions without forcing
377you to stringify the keys (unlike the previous set of functions).
378
379They also return and accept whole hash entries (C<HE*>), making their
380use more efficient (since the hash number for a particular string
381doesn't have to be recomputed every time). See L<API LISTING> later in
382this document for detailed descriptions.
383
384The following macros must always be used to access the contents of hash
385entries. Note that the arguments to these macros must be simple
386variables, since they may get evaluated more than once. See
387L<API LISTING> later in this document for detailed descriptions of these
388macros.
389
390 HePV(HE* he, STRLEN len)
391 HeVAL(HE* he)
392 HeHASH(HE* he)
393 HeSVKEY(HE* he)
394 HeSVKEY_force(HE* he)
395 HeSVKEY_set(HE* he, SV* sv)
396
397These two lower level macros are defined, but must only be used when
398dealing with keys that are not C<SV*>s:
399
400 HeKEY(HE* he)
401 HeKLEN(HE* he)
402
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403Note that both C<hv_store> and C<hv_store_ent> do not increment the
404reference count of the stored C<val>, which is the caller's responsibility.
405If these functions return a NULL value, the caller will usually have to
406decrement the reference count of C<val> to avoid a memory leak.
1e422769 407
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408=head2 References
409
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410References are a special type of scalar that point to other data types
411(including references).
a0d0e21e 412
07fa94a1 413To create a reference, use either of the following functions:
a0d0e21e 414
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415 SV* newRV_inc((SV*) thing);
416 SV* newRV_noinc((SV*) thing);
a0d0e21e 417
5f05dabc 418The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
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419functions are identical except that C<newRV_inc> increments the reference
420count of the C<thing>, while C<newRV_noinc> does not. For historical
421reasons, C<newRV> is a synonym for C<newRV_inc>.
422
423Once you have a reference, you can use the following macro to dereference
424the reference:
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425
426 SvRV(SV*)
427
428then call the appropriate routines, casting the returned C<SV*> to either an
d1b91892 429C<AV*> or C<HV*>, if required.
a0d0e21e 430
d1b91892 431To determine if an SV is a reference, you can use the following macro:
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432
433 SvROK(SV*)
434
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435To discover what type of value the reference refers to, use the following
436macro and then check the return value.
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437
438 SvTYPE(SvRV(SV*))
439
440The most useful types that will be returned are:
441
442 SVt_IV Scalar
443 SVt_NV Scalar
444 SVt_PV Scalar
5f05dabc 445 SVt_RV Scalar
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446 SVt_PVAV Array
447 SVt_PVHV Hash
448 SVt_PVCV Code
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449 SVt_PVGV Glob (possible a file handle)
450 SVt_PVMG Blessed or Magical Scalar
451
452 See the sv.h header file for more details.
d1b91892 453
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454=head2 Blessed References and Class Objects
455
456References are also used to support object-oriented programming. In the
457OO lexicon, an object is simply a reference that has been blessed into a
458package (or class). Once blessed, the programmer may now use the reference
459to access the various methods in the class.
460
461A reference can be blessed into a package with the following function:
462
463 SV* sv_bless(SV* sv, HV* stash);
464
465The C<sv> argument must be a reference. The C<stash> argument specifies
3fe9a6f1 466which class the reference will belong to. See
2ae324a7 467L<Stashes and Globs> for information on converting class names into stashes.
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468
469/* Still under construction */
470
471Upgrades rv to reference if not already one. Creates new SV for rv to
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472point to. If C<classname> is non-null, the SV is blessed into the specified
473class. SV is returned.
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474
475 SV* newSVrv(SV* rv, char* classname);
476
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477Copies integer or double into an SV whose reference is C<rv>. SV is blessed
478if C<classname> is non-null.
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479
480 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
481 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
482
5f05dabc 483Copies the pointer value (I<the address, not the string!>) into an SV whose
8ebc5c01 484reference is rv. SV is blessed if C<classname> is non-null.
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485
486 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
487
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488Copies string into an SV whose reference is C<rv>. Set length to 0 to let
489Perl calculate the string length. SV is blessed if C<classname> is non-null.
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490
491 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
492
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493Tests whether the SV is blessed into the specified class. It does not
494check inheritance relationships.
495
496 int sv_isa(SV* sv, char* name);
497
498Tests whether the SV is a reference to a blessed object.
499
500 int sv_isobject(SV* sv);
501
502Tests whether the SV is derived from the specified class. SV can be either
503a reference to a blessed object or a string containing a class name. This
504is the function implementing the C<UNIVERSAL::isa> functionality.
505
506 bool sv_derived_from(SV* sv, char* name);
507
508To check if you've got an object derived from a specific class you have
509to write:
510
511 if (sv_isobject(sv) && sv_derived_from(sv, class)) { ... }
cb1a09d0 512
5f05dabc 513=head2 Creating New Variables
cb1a09d0 514
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515To create a new Perl variable with an undef value which can be accessed from
516your Perl script, use the following routines, depending on the variable type.
cb1a09d0 517
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518 SV* perl_get_sv("package::varname", TRUE);
519 AV* perl_get_av("package::varname", TRUE);
520 HV* perl_get_hv("package::varname", TRUE);
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521
522Notice the use of TRUE as the second parameter. The new variable can now
523be set, using the routines appropriate to the data type.
524
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525There are additional macros whose values may be bitwise OR'ed with the
526C<TRUE> argument to enable certain extra features. Those bits are:
cb1a09d0 527
5f05dabc 528 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
54310121 529 "Name <varname> used only once: possible typo" warning.
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530 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
531 the variable did not exist before the function was called.
cb1a09d0 532
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533If you do not specify a package name, the variable is created in the current
534package.
cb1a09d0 535
5f05dabc 536=head2 Reference Counts and Mortality
a0d0e21e 537
54310121
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538Perl uses an reference count-driven garbage collection mechanism. SVs,
539AVs, or HVs (xV for short in the following) start their life with a
55497cff 540reference count of 1. If the reference count of an xV ever drops to 0,
07fa94a1 541then it will be destroyed and its memory made available for reuse.
55497cff
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542
543This normally doesn't happen at the Perl level unless a variable is
5f05dabc
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544undef'ed or the last variable holding a reference to it is changed or
545overwritten. At the internal level, however, reference counts can be
55497cff
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546manipulated with the following macros:
547
548 int SvREFCNT(SV* sv);
5f05dabc 549 SV* SvREFCNT_inc(SV* sv);
55497cff
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550 void SvREFCNT_dec(SV* sv);
551
552However, there is one other function which manipulates the reference
07fa94a1
JO
553count of its argument. The C<newRV_inc> function, you will recall,
554creates a reference to the specified argument. As a side effect,
555it increments the argument's reference count. If this is not what
556you want, use C<newRV_noinc> instead.
557
558For example, imagine you want to return a reference from an XSUB function.
559Inside the XSUB routine, you create an SV which initially has a reference
560count of one. Then you call C<newRV_inc>, passing it the just-created SV.
5f05dabc
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561This returns the reference as a new SV, but the reference count of the
562SV you passed to C<newRV_inc> has been incremented to two. Now you
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563return the reference from the XSUB routine and forget about the SV.
564But Perl hasn't! Whenever the returned reference is destroyed, the
565reference count of the original SV is decreased to one and nothing happens.
566The SV will hang around without any way to access it until Perl itself
567terminates. This is a memory leak.
5f05dabc
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568
569The correct procedure, then, is to use C<newRV_noinc> instead of
faed5253
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570C<newRV_inc>. Then, if and when the last reference is destroyed,
571the reference count of the SV will go to zero and it will be destroyed,
07fa94a1 572stopping any memory leak.
55497cff 573
5f05dabc 574There are some convenience functions available that can help with the
54310121 575destruction of xVs. These functions introduce the concept of "mortality".
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576An xV that is mortal has had its reference count marked to be decremented,
577but not actually decremented, until "a short time later". Generally the
578term "short time later" means a single Perl statement, such as a call to
54310121 579an XSUB function. The actual determinant for when mortal xVs have their
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580reference count decremented depends on two macros, SAVETMPS and FREETMPS.
581See L<perlcall> and L<perlxs> for more details on these macros.
55497cff
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582
583"Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
584However, if you mortalize a variable twice, the reference count will
585later be decremented twice.
586
587You should be careful about creating mortal variables. Strange things
588can happen if you make the same value mortal within multiple contexts,
5f05dabc 589or if you make a variable mortal multiple times.
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590
591To create a mortal variable, use the functions:
592
593 SV* sv_newmortal()
594 SV* sv_2mortal(SV*)
595 SV* sv_mortalcopy(SV*)
596
5f05dabc
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597The first call creates a mortal SV, the second converts an existing
598SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
599third creates a mortal copy of an existing SV.
a0d0e21e 600
54310121 601The mortal routines are not just for SVs -- AVs and HVs can be
faed5253 602made mortal by passing their address (type-casted to C<SV*>) to the
07fa94a1 603C<sv_2mortal> or C<sv_mortalcopy> routines.
a0d0e21e 604
5f05dabc 605=head2 Stashes and Globs
a0d0e21e 606
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607A "stash" is a hash that contains all of the different objects that
608are contained within a package. Each key of the stash is a symbol
609name (shared by all the different types of objects that have the same
610name), and each value in the hash table is a GV (Glob Value). This GV
611in turn contains references to the various objects of that name,
612including (but not limited to) the following:
cb1a09d0 613
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614 Scalar Value
615 Array Value
616 Hash Value
a3cb178b 617 I/O Handle
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618 Format
619 Subroutine
620
9cde0e7f 621There is a single stash called "PL_defstash" that holds the items that exist
5f05dabc
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622in the "main" package. To get at the items in other packages, append the
623string "::" to the package name. The items in the "Foo" package are in
9cde0e7f 624the stash "Foo::" in PL_defstash. The items in the "Bar::Baz" package are
5f05dabc 625in the stash "Baz::" in "Bar::"'s stash.
a0d0e21e 626
d1b91892 627To get the stash pointer for a particular package, use the function:
a0d0e21e
LW
628
629 HV* gv_stashpv(char* name, I32 create)
630 HV* gv_stashsv(SV*, I32 create)
631
632The first function takes a literal string, the second uses the string stored
d1b91892 633in the SV. Remember that a stash is just a hash table, so you get back an
cb1a09d0 634C<HV*>. The C<create> flag will create a new package if it is set.
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635
636The name that C<gv_stash*v> wants is the name of the package whose symbol table
637you want. The default package is called C<main>. If you have multiply nested
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638packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
639language itself.
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640
641Alternately, if you have an SV that is a blessed reference, you can find
642out the stash pointer by using:
643
644 HV* SvSTASH(SvRV(SV*));
645
646then use the following to get the package name itself:
647
648 char* HvNAME(HV* stash);
649
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650If you need to bless or re-bless an object you can use the following
651function:
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LW
652
653 SV* sv_bless(SV*, HV* stash)
654
655where the first argument, an C<SV*>, must be a reference, and the second
656argument is a stash. The returned C<SV*> can now be used in the same way
657as any other SV.
658
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659For more information on references and blessings, consult L<perlref>.
660
54310121 661=head2 Double-Typed SVs
0a753a76
PP
662
663Scalar variables normally contain only one type of value, an integer,
664double, pointer, or reference. Perl will automatically convert the
665actual scalar data from the stored type into the requested type.
666
667Some scalar variables contain more than one type of scalar data. For
668example, the variable C<$!> contains either the numeric value of C<errno>
669or its string equivalent from either C<strerror> or C<sys_errlist[]>.
670
671To force multiple data values into an SV, you must do two things: use the
672C<sv_set*v> routines to add the additional scalar type, then set a flag
673so that Perl will believe it contains more than one type of data. The
674four macros to set the flags are:
675
676 SvIOK_on
677 SvNOK_on
678 SvPOK_on
679 SvROK_on
680
681The particular macro you must use depends on which C<sv_set*v> routine
682you called first. This is because every C<sv_set*v> routine turns on
683only the bit for the particular type of data being set, and turns off
684all the rest.
685
686For example, to create a new Perl variable called "dberror" that contains
687both the numeric and descriptive string error values, you could use the
688following code:
689
690 extern int dberror;
691 extern char *dberror_list;
692
693 SV* sv = perl_get_sv("dberror", TRUE);
694 sv_setiv(sv, (IV) dberror);
695 sv_setpv(sv, dberror_list[dberror]);
696 SvIOK_on(sv);
697
698If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
699macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
700
701=head2 Magic Variables
a0d0e21e 702
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703[This section still under construction. Ignore everything here. Post no
704bills. Everything not permitted is forbidden.]
705
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706Any SV may be magical, that is, it has special features that a normal
707SV does not have. These features are stored in the SV structure in a
5f05dabc 708linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
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AD
709
710 struct magic {
711 MAGIC* mg_moremagic;
712 MGVTBL* mg_virtual;
713 U16 mg_private;
714 char mg_type;
715 U8 mg_flags;
716 SV* mg_obj;
717 char* mg_ptr;
718 I32 mg_len;
719 };
720
721Note this is current as of patchlevel 0, and could change at any time.
722
723=head2 Assigning Magic
724
725Perl adds magic to an SV using the sv_magic function:
726
727 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
728
729The C<sv> argument is a pointer to the SV that is to acquire a new magical
730feature.
731
732If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
733set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
734it to the beginning of the linked list of magical features. Any prior
735entry of the same type of magic is deleted. Note that this can be
5fb8527f 736overridden, and multiple instances of the same type of magic can be
d1b91892
AD
737associated with an SV.
738
54310121
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739The C<name> and C<namlen> arguments are used to associate a string with
740the magic, typically the name of a variable. C<namlen> is stored in the
741C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
d1b91892
AD
742copy of the name is stored in C<mg_ptr> field.
743
744The sv_magic function uses C<how> to determine which, if any, predefined
745"Magic Virtual Table" should be assigned to the C<mg_virtual> field.
cb1a09d0
AD
746See the "Magic Virtual Table" section below. The C<how> argument is also
747stored in the C<mg_type> field.
d1b91892
AD
748
749The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
750structure. If it is not the same as the C<sv> argument, the reference
751count of the C<obj> object is incremented. If it is the same, or if
04343c6d 752the C<how> argument is "#", or if it is a NULL pointer, then C<obj> is
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AD
753merely stored, without the reference count being incremented.
754
cb1a09d0
AD
755There is also a function to add magic to an C<HV>:
756
757 void hv_magic(HV *hv, GV *gv, int how);
758
759This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
760
761To remove the magic from an SV, call the function sv_unmagic:
762
763 void sv_unmagic(SV *sv, int type);
764
765The C<type> argument should be equal to the C<how> value when the C<SV>
766was initially made magical.
767
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AD
768=head2 Magic Virtual Tables
769
770The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
771C<MGVTBL>, which is a structure of function pointers and stands for
772"Magic Virtual Table" to handle the various operations that might be
773applied to that variable.
774
775The C<MGVTBL> has five pointers to the following routine types:
776
777 int (*svt_get)(SV* sv, MAGIC* mg);
778 int (*svt_set)(SV* sv, MAGIC* mg);
779 U32 (*svt_len)(SV* sv, MAGIC* mg);
780 int (*svt_clear)(SV* sv, MAGIC* mg);
781 int (*svt_free)(SV* sv, MAGIC* mg);
782
783This MGVTBL structure is set at compile-time in C<perl.h> and there are
784currently 19 types (or 21 with overloading turned on). These different
785structures contain pointers to various routines that perform additional
786actions depending on which function is being called.
787
788 Function pointer Action taken
789 ---------------- ------------
790 svt_get Do something after the value of the SV is retrieved.
791 svt_set Do something after the SV is assigned a value.
792 svt_len Report on the SV's length.
793 svt_clear Clear something the SV represents.
794 svt_free Free any extra storage associated with the SV.
795
796For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
797to an C<mg_type> of '\0') contains:
798
799 { magic_get, magic_set, magic_len, 0, 0 }
800
801Thus, when an SV is determined to be magical and of type '\0', if a get
802operation is being performed, the routine C<magic_get> is called. All
803the various routines for the various magical types begin with C<magic_>.
804
805The current kinds of Magic Virtual Tables are:
806
bdbeb323 807 mg_type MGVTBL Type of magic
5f05dabc 808 ------- ------ ----------------------------
bdbeb323
SM
809 \0 vtbl_sv Special scalar variable
810 A vtbl_amagic %OVERLOAD hash
811 a vtbl_amagicelem %OVERLOAD hash element
812 c (none) Holds overload table (AMT) on stash
813 B vtbl_bm Boyer-Moore (fast string search)
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AD
814 E vtbl_env %ENV hash
815 e vtbl_envelem %ENV hash element
bdbeb323
SM
816 f vtbl_fm Formline ('compiled' format)
817 g vtbl_mglob m//g target / study()ed string
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AD
818 I vtbl_isa @ISA array
819 i vtbl_isaelem @ISA array element
bdbeb323
SM
820 k vtbl_nkeys scalar(keys()) lvalue
821 L (none) Debugger %_<filename
822 l vtbl_dbline Debugger %_<filename element
44a8e56a 823 o vtbl_collxfrm Locale transformation
bdbeb323
SM
824 P vtbl_pack Tied array or hash
825 p vtbl_packelem Tied array or hash element
826 q vtbl_packelem Tied scalar or handle
827 S vtbl_sig %SIG hash
828 s vtbl_sigelem %SIG hash element
d1b91892 829 t vtbl_taint Taintedness
bdbeb323
SM
830 U vtbl_uvar Available for use by extensions
831 v vtbl_vec vec() lvalue
832 x vtbl_substr substr() lvalue
833 y vtbl_defelem Shadow "foreach" iterator variable /
834 smart parameter vivification
835 * vtbl_glob GV (typeglob)
836 # vtbl_arylen Array length ($#ary)
837 . vtbl_pos pos() lvalue
838 ~ (none) Available for use by extensions
d1b91892 839
68dc0745
PP
840When an uppercase and lowercase letter both exist in the table, then the
841uppercase letter is used to represent some kind of composite type (a list
842or a hash), and the lowercase letter is used to represent an element of
d1b91892
AD
843that composite type.
844
bdbeb323
SM
845The '~' and 'U' magic types are defined specifically for use by
846extensions and will not be used by perl itself. Extensions can use
847'~' magic to 'attach' private information to variables (typically
848objects). This is especially useful because there is no way for
849normal perl code to corrupt this private information (unlike using
850extra elements of a hash object).
851
852Similarly, 'U' magic can be used much like tie() to call a C function
853any time a scalar's value is used or changed. The C<MAGIC>'s
854C<mg_ptr> field points to a C<ufuncs> structure:
855
856 struct ufuncs {
857 I32 (*uf_val)(IV, SV*);
858 I32 (*uf_set)(IV, SV*);
859 IV uf_index;
860 };
861
862When the SV is read from or written to, the C<uf_val> or C<uf_set>
863function will be called with C<uf_index> as the first arg and a
864pointer to the SV as the second.
5f05dabc 865
bdbeb323
SM
866Note that because multiple extensions may be using '~' or 'U' magic,
867it is important for extensions to take extra care to avoid conflict.
868Typically only using the magic on objects blessed into the same class
869as the extension is sufficient. For '~' magic, it may also be
870appropriate to add an I32 'signature' at the top of the private data
871area and check that.
5f05dabc 872
ef50df4b
GS
873Also note that the C<sv_set*()> and C<sv_cat*()> functions described
874earlier do B<not> invoke 'set' magic on their targets. This must
875be done by the user either by calling the C<SvSETMAGIC()> macro after
876calling these functions, or by using one of the C<sv_set*_mg()> or
877C<sv_cat*_mg()> functions. Similarly, generic C code must call the
878C<SvGETMAGIC()> macro to invoke any 'get' magic if they use an SV
879obtained from external sources in functions that don't handle magic.
880L<API LISTING> later in this document identifies such functions.
189b2af5
GS
881For example, calls to the C<sv_cat*()> functions typically need to be
882followed by C<SvSETMAGIC()>, but they don't need a prior C<SvGETMAGIC()>
883since their implementation handles 'get' magic.
884
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AD
885=head2 Finding Magic
886
887 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
888
889This routine returns a pointer to the C<MAGIC> structure stored in the SV.
890If the SV does not have that magical feature, C<NULL> is returned. Also,
54310121 891if the SV is not of type SVt_PVMG, Perl may core dump.
d1b91892
AD
892
893 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
894
895This routine checks to see what types of magic C<sv> has. If the mg_type
68dc0745
PP
896field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
897the mg_type field is changed to be the lowercase letter.
a0d0e21e 898
04343c6d
GS
899=head2 Understanding the Magic of Tied Hashes and Arrays
900
901Tied hashes and arrays are magical beasts of the 'P' magic type.
9edb2b46
GS
902
903WARNING: As of the 5.004 release, proper usage of the array and hash
904access functions requires understanding a few caveats. Some
905of these caveats are actually considered bugs in the API, to be fixed
906in later releases, and are bracketed with [MAYCHANGE] below. If
907you find yourself actually applying such information in this section, be
908aware that the behavior may change in the future, umm, without warning.
04343c6d
GS
909
910The C<av_store> function, when given a tied array argument, merely
911copies the magic of the array onto the value to be "stored", using
912C<mg_copy>. It may also return NULL, indicating that the value did not
9edb2b46
GS
913actually need to be stored in the array. [MAYCHANGE] After a call to
914C<av_store> on a tied array, the caller will usually need to call
915C<mg_set(val)> to actually invoke the perl level "STORE" method on the
916TIEARRAY object. If C<av_store> did return NULL, a call to
917C<SvREFCNT_dec(val)> will also be usually necessary to avoid a memory
918leak. [/MAYCHANGE]
04343c6d
GS
919
920The previous paragraph is applicable verbatim to tied hash access using the
921C<hv_store> and C<hv_store_ent> functions as well.
922
923C<av_fetch> and the corresponding hash functions C<hv_fetch> and
924C<hv_fetch_ent> actually return an undefined mortal value whose magic
925has been initialized using C<mg_copy>. Note the value so returned does not
9edb2b46
GS
926need to be deallocated, as it is already mortal. [MAYCHANGE] But you will
927need to call C<mg_get()> on the returned value in order to actually invoke
928the perl level "FETCH" method on the underlying TIE object. Similarly,
04343c6d
GS
929you may also call C<mg_set()> on the return value after possibly assigning
930a suitable value to it using C<sv_setsv>, which will invoke the "STORE"
9edb2b46 931method on the TIE object. [/MAYCHANGE]
04343c6d 932
9edb2b46 933[MAYCHANGE]
04343c6d
GS
934In other words, the array or hash fetch/store functions don't really
935fetch and store actual values in the case of tied arrays and hashes. They
936merely call C<mg_copy> to attach magic to the values that were meant to be
937"stored" or "fetched". Later calls to C<mg_get> and C<mg_set> actually
938do the job of invoking the TIE methods on the underlying objects. Thus
9edb2b46 939the magic mechanism currently implements a kind of lazy access to arrays
04343c6d
GS
940and hashes.
941
942Currently (as of perl version 5.004), use of the hash and array access
943functions requires the user to be aware of whether they are operating on
9edb2b46
GS
944"normal" hashes and arrays, or on their tied variants. The API may be
945changed to provide more transparent access to both tied and normal data
946types in future versions.
947[/MAYCHANGE]
04343c6d
GS
948
949You would do well to understand that the TIEARRAY and TIEHASH interfaces
950are mere sugar to invoke some perl method calls while using the uniform hash
951and array syntax. The use of this sugar imposes some overhead (typically
952about two to four extra opcodes per FETCH/STORE operation, in addition to
953the creation of all the mortal variables required to invoke the methods).
954This overhead will be comparatively small if the TIE methods are themselves
955substantial, but if they are only a few statements long, the overhead
956will not be insignificant.
957
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IZ
958=head2 Localizing changes
959
960Perl has a very handy construction
961
962 {
963 local $var = 2;
964 ...
965 }
966
967This construction is I<approximately> equivalent to
968
969 {
970 my $oldvar = $var;
971 $var = 2;
972 ...
973 $var = $oldvar;
974 }
975
976The biggest difference is that the first construction would
977reinstate the initial value of $var, irrespective of how control exits
978the block: C<goto>, C<return>, C<die>/C<eval> etc. It is a little bit
979more efficient as well.
980
981There is a way to achieve a similar task from C via Perl API: create a
982I<pseudo-block>, and arrange for some changes to be automatically
983undone at the end of it, either explicit, or via a non-local exit (via
984die()). A I<block>-like construct is created by a pair of
985C<ENTER>/C<LEAVE> macros (see L<perlcall/EXAMPLE/"Returning a
986Scalar">). Such a construct may be created specially for some
987important localized task, or an existing one (like boundaries of
988enclosing Perl subroutine/block, or an existing pair for freeing TMPs)
989may be used. (In the second case the overhead of additional
990localization must be almost negligible.) Note that any XSUB is
991automatically enclosed in an C<ENTER>/C<LEAVE> pair.
992
993Inside such a I<pseudo-block> the following service is available:
994
995=over
996
997=item C<SAVEINT(int i)>
998
999=item C<SAVEIV(IV i)>
1000
1001=item C<SAVEI32(I32 i)>
1002
1003=item C<SAVELONG(long i)>
1004
1005These macros arrange things to restore the value of integer variable
1006C<i> at the end of enclosing I<pseudo-block>.
1007
1008=item C<SAVESPTR(s)>
1009
1010=item C<SAVEPPTR(p)>
1011
1012These macros arrange things to restore the value of pointers C<s> and
1013C<p>. C<s> must be a pointer of a type which survives conversion to
1014C<SV*> and back, C<p> should be able to survive conversion to C<char*>
1015and back.
1016
1017=item C<SAVEFREESV(SV *sv)>
1018
1019The refcount of C<sv> would be decremented at the end of
1020I<pseudo-block>. This is similar to C<sv_2mortal>, which should (?) be
1021used instead.
1022
1023=item C<SAVEFREEOP(OP *op)>
1024
1025The C<OP *> is op_free()ed at the end of I<pseudo-block>.
1026
1027=item C<SAVEFREEPV(p)>
1028
1029The chunk of memory which is pointed to by C<p> is Safefree()ed at the
1030end of I<pseudo-block>.
1031
1032=item C<SAVECLEARSV(SV *sv)>
1033
1034Clears a slot in the current scratchpad which corresponds to C<sv> at
1035the end of I<pseudo-block>.
1036
1037=item C<SAVEDELETE(HV *hv, char *key, I32 length)>
1038
1039The key C<key> of C<hv> is deleted at the end of I<pseudo-block>. The
1040string pointed to by C<key> is Safefree()ed. If one has a I<key> in
1041short-lived storage, the corresponding string may be reallocated like
1042this:
1043
9cde0e7f 1044 SAVEDELETE(PL_defstash, savepv(tmpbuf), strlen(tmpbuf));
d1c897a1
IZ
1045
1046=item C<SAVEDESTRUCTOR(f,p)>
1047
1048At the end of I<pseudo-block> the function C<f> is called with the
1049only argument (of type C<void*>) C<p>.
1050
1051=item C<SAVESTACK_POS()>
1052
1053The current offset on the Perl internal stack (cf. C<SP>) is restored
1054at the end of I<pseudo-block>.
1055
1056=back
1057
1058The following API list contains functions, thus one needs to
1059provide pointers to the modifiable data explicitly (either C pointers,
1060or Perlish C<GV *>s). Where the above macros take C<int>, a similar
1061function takes C<int *>.
1062
1063=over
1064
1065=item C<SV* save_scalar(GV *gv)>
1066
1067Equivalent to Perl code C<local $gv>.
1068
1069=item C<AV* save_ary(GV *gv)>
1070
1071=item C<HV* save_hash(GV *gv)>
1072
1073Similar to C<save_scalar>, but localize C<@gv> and C<%gv>.
1074
1075=item C<void save_item(SV *item)>
1076
1077Duplicates the current value of C<SV>, on the exit from the current
1078C<ENTER>/C<LEAVE> I<pseudo-block> will restore the value of C<SV>
1079using the stored value.
1080
1081=item C<void save_list(SV **sarg, I32 maxsarg)>
1082
1083A variant of C<save_item> which takes multiple arguments via an array
1084C<sarg> of C<SV*> of length C<maxsarg>.
1085
1086=item C<SV* save_svref(SV **sptr)>
1087
1088Similar to C<save_scalar>, but will reinstate a C<SV *>.
1089
1090=item C<void save_aptr(AV **aptr)>
1091
1092=item C<void save_hptr(HV **hptr)>
1093
1094Similar to C<save_svref>, but localize C<AV *> and C<HV *>.
1095
1096=back
1097
1098The C<Alias> module implements localization of the basic types within the
1099I<caller's scope>. People who are interested in how to localize things in
1100the containing scope should take a look there too.
1101
0a753a76 1102=head1 Subroutines
a0d0e21e 1103
68dc0745 1104=head2 XSUBs and the Argument Stack
5f05dabc
PP
1105
1106The XSUB mechanism is a simple way for Perl programs to access C subroutines.
1107An XSUB routine will have a stack that contains the arguments from the Perl
1108program, and a way to map from the Perl data structures to a C equivalent.
1109
1110The stack arguments are accessible through the C<ST(n)> macro, which returns
1111the C<n>'th stack argument. Argument 0 is the first argument passed in the
1112Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
1113an C<SV*> is used.
1114
1115Most of the time, output from the C routine can be handled through use of
1116the RETVAL and OUTPUT directives. However, there are some cases where the
1117argument stack is not already long enough to handle all the return values.
1118An example is the POSIX tzname() call, which takes no arguments, but returns
1119two, the local time zone's standard and summer time abbreviations.
1120
1121To handle this situation, the PPCODE directive is used and the stack is
1122extended using the macro:
1123
924508f0 1124 EXTEND(SP, num);
5f05dabc 1125
924508f0
GS
1126where C<SP> is the macro that represents the local copy of the stack pointer,
1127and C<num> is the number of elements the stack should be extended by.
5f05dabc
PP
1128
1129Now that there is room on the stack, values can be pushed on it using the
54310121 1130macros to push IVs, doubles, strings, and SV pointers respectively:
5f05dabc
PP
1131
1132 PUSHi(IV)
1133 PUSHn(double)
1134 PUSHp(char*, I32)
1135 PUSHs(SV*)
1136
1137And now the Perl program calling C<tzname>, the two values will be assigned
1138as in:
1139
1140 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
1141
1142An alternate (and possibly simpler) method to pushing values on the stack is
1143to use the macros:
1144
1145 XPUSHi(IV)
1146 XPUSHn(double)
1147 XPUSHp(char*, I32)
1148 XPUSHs(SV*)
1149
1150These macros automatically adjust the stack for you, if needed. Thus, you
1151do not need to call C<EXTEND> to extend the stack.
1152
1153For more information, consult L<perlxs> and L<perlxstut>.
1154
1155=head2 Calling Perl Routines from within C Programs
a0d0e21e
LW
1156
1157There are four routines that can be used to call a Perl subroutine from
1158within a C program. These four are:
1159
1160 I32 perl_call_sv(SV*, I32);
1161 I32 perl_call_pv(char*, I32);
1162 I32 perl_call_method(char*, I32);
1163 I32 perl_call_argv(char*, I32, register char**);
1164
d1b91892
AD
1165The routine most often used is C<perl_call_sv>. The C<SV*> argument
1166contains either the name of the Perl subroutine to be called, or a
1167reference to the subroutine. The second argument consists of flags
1168that control the context in which the subroutine is called, whether
1169or not the subroutine is being passed arguments, how errors should be
1170trapped, and how to treat return values.
a0d0e21e
LW
1171
1172All four routines return the number of arguments that the subroutine returned
1173on the Perl stack.
1174
d1b91892
AD
1175When using any of these routines (except C<perl_call_argv>), the programmer
1176must manipulate the Perl stack. These include the following macros and
1177functions:
a0d0e21e
LW
1178
1179 dSP
924508f0 1180 SP
a0d0e21e
LW
1181 PUSHMARK()
1182 PUTBACK
1183 SPAGAIN
1184 ENTER
1185 SAVETMPS
1186 FREETMPS
1187 LEAVE
1188 XPUSH*()
cb1a09d0 1189 POP*()
a0d0e21e 1190
5f05dabc
PP
1191For a detailed description of calling conventions from C to Perl,
1192consult L<perlcall>.
a0d0e21e 1193
5f05dabc 1194=head2 Memory Allocation
a0d0e21e 1195
5f05dabc
PP
1196It is suggested that you use the version of malloc that is distributed
1197with Perl. It keeps pools of various sizes of unallocated memory in
07fa94a1
JO
1198order to satisfy allocation requests more quickly. However, on some
1199platforms, it may cause spurious malloc or free errors.
d1b91892
AD
1200
1201 New(x, pointer, number, type);
1202 Newc(x, pointer, number, type, cast);
1203 Newz(x, pointer, number, type);
1204
07fa94a1 1205These three macros are used to initially allocate memory.
5f05dabc
PP
1206
1207The first argument C<x> was a "magic cookie" that was used to keep track
1208of who called the macro, to help when debugging memory problems. However,
07fa94a1
JO
1209the current code makes no use of this feature (most Perl developers now
1210use run-time memory checkers), so this argument can be any number.
5f05dabc
PP
1211
1212The second argument C<pointer> should be the name of a variable that will
1213point to the newly allocated memory.
d1b91892 1214
d1b91892
AD
1215The third and fourth arguments C<number> and C<type> specify how many of
1216the specified type of data structure should be allocated. The argument
1217C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
1218should be used if the C<pointer> argument is different from the C<type>
1219argument.
1220
1221Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
1222to zero out all the newly allocated memory.
1223
1224 Renew(pointer, number, type);
1225 Renewc(pointer, number, type, cast);
1226 Safefree(pointer)
1227
1228These three macros are used to change a memory buffer size or to free a
1229piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
1230match those of C<New> and C<Newc> with the exception of not needing the
1231"magic cookie" argument.
1232
1233 Move(source, dest, number, type);
1234 Copy(source, dest, number, type);
1235 Zero(dest, number, type);
1236
1237These three macros are used to move, copy, or zero out previously allocated
1238memory. The C<source> and C<dest> arguments point to the source and
1239destination starting points. Perl will move, copy, or zero out C<number>
1240instances of the size of the C<type> data structure (using the C<sizeof>
1241function).
a0d0e21e 1242
5f05dabc 1243=head2 PerlIO
ce3d39e2 1244
5f05dabc
PP
1245The most recent development releases of Perl has been experimenting with
1246removing Perl's dependency on the "normal" standard I/O suite and allowing
1247other stdio implementations to be used. This involves creating a new
1248abstraction layer that then calls whichever implementation of stdio Perl
68dc0745 1249was compiled with. All XSUBs should now use the functions in the PerlIO
5f05dabc
PP
1250abstraction layer and not make any assumptions about what kind of stdio
1251is being used.
1252
1253For a complete description of the PerlIO abstraction, consult L<perlapio>.
1254
8ebc5c01 1255=head2 Putting a C value on Perl stack
ce3d39e2
IZ
1256
1257A lot of opcodes (this is an elementary operation in the internal perl
1258stack machine) put an SV* on the stack. However, as an optimization
1259the corresponding SV is (usually) not recreated each time. The opcodes
1260reuse specially assigned SVs (I<target>s) which are (as a corollary)
1261not constantly freed/created.
1262
0a753a76 1263Each of the targets is created only once (but see
ce3d39e2
IZ
1264L<Scratchpads and recursion> below), and when an opcode needs to put
1265an integer, a double, or a string on stack, it just sets the
1266corresponding parts of its I<target> and puts the I<target> on stack.
1267
1268The macro to put this target on stack is C<PUSHTARG>, and it is
1269directly used in some opcodes, as well as indirectly in zillions of
1270others, which use it via C<(X)PUSH[pni]>.
1271
8ebc5c01 1272=head2 Scratchpads
ce3d39e2 1273
54310121 1274The question remains on when the SVs which are I<target>s for opcodes
5f05dabc
PP
1275are created. The answer is that they are created when the current unit --
1276a subroutine or a file (for opcodes for statements outside of
1277subroutines) -- is compiled. During this time a special anonymous Perl
ce3d39e2
IZ
1278array is created, which is called a scratchpad for the current
1279unit.
1280
54310121 1281A scratchpad keeps SVs which are lexicals for the current unit and are
ce3d39e2
IZ
1282targets for opcodes. One can deduce that an SV lives on a scratchpad
1283by looking on its flags: lexicals have C<SVs_PADMY> set, and
1284I<target>s have C<SVs_PADTMP> set.
1285
54310121
PP
1286The correspondence between OPs and I<target>s is not 1-to-1. Different
1287OPs in the compile tree of the unit can use the same target, if this
ce3d39e2
IZ
1288would not conflict with the expected life of the temporary.
1289
2ae324a7 1290=head2 Scratchpads and recursion
ce3d39e2
IZ
1291
1292In fact it is not 100% true that a compiled unit contains a pointer to
1293the scratchpad AV. In fact it contains a pointer to an AV of
1294(initially) one element, and this element is the scratchpad AV. Why do
1295we need an extra level of indirection?
1296
1297The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1298these can create several execution pointers going into the same
1299subroutine. For the subroutine-child not write over the temporaries
1300for the subroutine-parent (lifespan of which covers the call to the
1301child), the parent and the child should have different
1302scratchpads. (I<And> the lexicals should be separate anyway!)
1303
5f05dabc
PP
1304So each subroutine is born with an array of scratchpads (of length 1).
1305On each entry to the subroutine it is checked that the current
ce3d39e2
IZ
1306depth of the recursion is not more than the length of this array, and
1307if it is, new scratchpad is created and pushed into the array.
1308
1309The I<target>s on this scratchpad are C<undef>s, but they are already
1310marked with correct flags.
1311
0a753a76
PP
1312=head1 Compiled code
1313
1314=head2 Code tree
1315
1316Here we describe the internal form your code is converted to by
1317Perl. Start with a simple example:
1318
1319 $a = $b + $c;
1320
1321This is converted to a tree similar to this one:
1322
1323 assign-to
1324 / \
1325 + $a
1326 / \
1327 $b $c
1328
7b8d334a 1329(but slightly more complicated). This tree reflects the way Perl
0a753a76
PP
1330parsed your code, but has nothing to do with the execution order.
1331There is an additional "thread" going through the nodes of the tree
1332which shows the order of execution of the nodes. In our simplified
1333example above it looks like:
1334
1335 $b ---> $c ---> + ---> $a ---> assign-to
1336
1337But with the actual compile tree for C<$a = $b + $c> it is different:
1338some nodes I<optimized away>. As a corollary, though the actual tree
1339contains more nodes than our simplified example, the execution order
1340is the same as in our example.
1341
1342=head2 Examining the tree
1343
1344If you have your perl compiled for debugging (usually done with C<-D
1345optimize=-g> on C<Configure> command line), you may examine the
1346compiled tree by specifying C<-Dx> on the Perl command line. The
1347output takes several lines per node, and for C<$b+$c> it looks like
1348this:
1349
1350 5 TYPE = add ===> 6
1351 TARG = 1
1352 FLAGS = (SCALAR,KIDS)
1353 {
1354 TYPE = null ===> (4)
1355 (was rv2sv)
1356 FLAGS = (SCALAR,KIDS)
1357 {
1358 3 TYPE = gvsv ===> 4
1359 FLAGS = (SCALAR)
1360 GV = main::b
1361 }
1362 }
1363 {
1364 TYPE = null ===> (5)
1365 (was rv2sv)
1366 FLAGS = (SCALAR,KIDS)
1367 {
1368 4 TYPE = gvsv ===> 5
1369 FLAGS = (SCALAR)
1370 GV = main::c
1371 }
1372 }
1373
1374This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1375not optimized away (one per number in the left column). The immediate
1376children of the given node correspond to C<{}> pairs on the same level
1377of indentation, thus this listing corresponds to the tree:
1378
1379 add
1380 / \
1381 null null
1382 | |
1383 gvsv gvsv
1384
1385The execution order is indicated by C<===E<gt>> marks, thus it is C<3
13864 5 6> (node C<6> is not included into above listing), i.e.,
1387C<gvsv gvsv add whatever>.
1388
1389=head2 Compile pass 1: check routines
1390
1391The tree is created by the I<pseudo-compiler> while yacc code feeds it
1392the constructions it recognizes. Since yacc works bottom-up, so does
1393the first pass of perl compilation.
1394
1395What makes this pass interesting for perl developers is that some
1396optimization may be performed on this pass. This is optimization by
1397so-called I<check routines>. The correspondence between node names
1398and corresponding check routines is described in F<opcode.pl> (do not
1399forget to run C<make regen_headers> if you modify this file).
1400
1401A check routine is called when the node is fully constructed except
7b8d334a 1402for the execution-order thread. Since at this time there are no
0a753a76
PP
1403back-links to the currently constructed node, one can do most any
1404operation to the top-level node, including freeing it and/or creating
1405new nodes above/below it.
1406
1407The check routine returns the node which should be inserted into the
1408tree (if the top-level node was not modified, check routine returns
1409its argument).
1410
1411By convention, check routines have names C<ck_*>. They are usually
1412called from C<new*OP> subroutines (or C<convert>) (which in turn are
1413called from F<perly.y>).
1414
1415=head2 Compile pass 1a: constant folding
1416
1417Immediately after the check routine is called the returned node is
1418checked for being compile-time executable. If it is (the value is
1419judged to be constant) it is immediately executed, and a I<constant>
1420node with the "return value" of the corresponding subtree is
1421substituted instead. The subtree is deleted.
1422
1423If constant folding was not performed, the execution-order thread is
1424created.
1425
1426=head2 Compile pass 2: context propagation
1427
1428When a context for a part of compile tree is known, it is propagated
a3cb178b 1429down through the tree. At this time the context can have 5 values
0a753a76
PP
1430(instead of 2 for runtime context): void, boolean, scalar, list, and
1431lvalue. In contrast with the pass 1 this pass is processed from top
1432to bottom: a node's context determines the context for its children.
1433
1434Additional context-dependent optimizations are performed at this time.
1435Since at this moment the compile tree contains back-references (via
1436"thread" pointers), nodes cannot be free()d now. To allow
1437optimized-away nodes at this stage, such nodes are null()ified instead
1438of free()ing (i.e. their type is changed to OP_NULL).
1439
1440=head2 Compile pass 3: peephole optimization
1441
1442After the compile tree for a subroutine (or for an C<eval> or a file)
1443is created, an additional pass over the code is performed. This pass
1444is neither top-down or bottom-up, but in the execution order (with
7b8d334a 1445additional complications for conditionals). These optimizations are
0a753a76
PP
1446done in the subroutine peep(). Optimizations performed at this stage
1447are subject to the same restrictions as in the pass 2.
1448
1449=head1 API LISTING
a0d0e21e 1450
cb1a09d0
AD
1451This is a listing of functions, macros, flags, and variables that may be
1452useful to extension writers or that may be found while reading other
1453extensions.
9cde0e7f
GS
1454
1455Note that all Perl API global variables must be referenced with the C<PL_>
1456prefix. Some macros are provided for compatibility with the older,
1457unadorned names, but this support will be removed in a future release.
1458
1459It is strongly recommended that all Perl API functions that don't begin
1460with C<perl> be referenced with an explicit C<Perl_> prefix.
1461
e89caa19
GA
1462The sort order of the listing is case insensitive, with any
1463occurrences of '_' ignored for the the purpose of sorting.
a0d0e21e 1464
cb1a09d0 1465=over 8
a0d0e21e 1466
cb1a09d0
AD
1467=item av_clear
1468
0146554f
GA
1469Clears an array, making it empty. Does not free the memory used by the
1470array itself.
cb1a09d0 1471
ef50df4b 1472 void av_clear (AV* ar)
cb1a09d0
AD
1473
1474=item av_extend
1475
1476Pre-extend an array. The C<key> is the index to which the array should be
1477extended.
1478
ef50df4b 1479 void av_extend (AV* ar, I32 key)
cb1a09d0
AD
1480
1481=item av_fetch
1482
1483Returns the SV at the specified index in the array. The C<key> is the
1484index. If C<lval> is set then the fetch will be part of a store. Check
1485that the return value is non-null before dereferencing it to a C<SV*>.
1486
04343c6d
GS
1487See L<Understanding the Magic of Tied Hashes and Arrays> for more
1488information on how to use this function on tied arrays.
1489
ef50df4b 1490 SV** av_fetch (AV* ar, I32 key, I32 lval)
cb1a09d0 1491
e89caa19
GA
1492=item AvFILL
1493
95906810 1494Same as C<av_len()>. Deprecated, use C<av_len()> instead.
e89caa19 1495
cb1a09d0
AD
1496=item av_len
1497
1498Returns the highest index in the array. Returns -1 if the array is empty.
1499
ef50df4b 1500 I32 av_len (AV* ar)
cb1a09d0
AD
1501
1502=item av_make
1503
5fb8527f
PP
1504Creates a new AV and populates it with a list of SVs. The SVs are copied
1505into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1506will have a reference count of 1.
cb1a09d0 1507
ef50df4b 1508 AV* av_make (I32 size, SV** svp)
cb1a09d0
AD
1509
1510=item av_pop
1511
9cde0e7f 1512Pops an SV off the end of the array. Returns C<&PL_sv_undef> if the array is
cb1a09d0
AD
1513empty.
1514
ef50df4b 1515 SV* av_pop (AV* ar)
cb1a09d0
AD
1516
1517=item av_push
1518
5fb8527f
PP
1519Pushes an SV onto the end of the array. The array will grow automatically
1520to accommodate the addition.
cb1a09d0 1521
ef50df4b 1522 void av_push (AV* ar, SV* val)
cb1a09d0
AD
1523
1524=item av_shift
1525
1526Shifts an SV off the beginning of the array.
1527
ef50df4b 1528 SV* av_shift (AV* ar)
cb1a09d0
AD
1529
1530=item av_store
1531
1532Stores an SV in an array. The array index is specified as C<key>. The
04343c6d
GS
1533return value will be NULL if the operation failed or if the value did not
1534need to be actually stored within the array (as in the case of tied arrays).
1535Otherwise it can be dereferenced to get the original C<SV*>. Note that the
1536caller is responsible for suitably incrementing the reference count of C<val>
1537before the call, and decrementing it if the function returned NULL.
1538
1539See L<Understanding the Magic of Tied Hashes and Arrays> for more
1540information on how to use this function on tied arrays.
cb1a09d0 1541
ef50df4b 1542 SV** av_store (AV* ar, I32 key, SV* val)
cb1a09d0
AD
1543
1544=item av_undef
1545
0146554f 1546Undefines the array. Frees the memory used by the array itself.
cb1a09d0 1547
ef50df4b 1548 void av_undef (AV* ar)
cb1a09d0
AD
1549
1550=item av_unshift
1551
0146554f
GA
1552Unshift the given number of C<undef> values onto the beginning of the
1553array. The array will grow automatically to accommodate the addition.
1554You must then use C<av_store> to assign values to these new elements.
cb1a09d0 1555
ef50df4b 1556 void av_unshift (AV* ar, I32 num)
cb1a09d0
AD
1557
1558=item CLASS
1559
1560Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1561constructor. This is always a C<char*>. See C<THIS> and
1562L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1563
1564=item Copy
1565
1566The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1567source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 1568the type. May fail on overlapping copies. See also C<Move>.
cb1a09d0 1569
e89caa19 1570 void Copy( s, d, n, t )
cb1a09d0
AD
1571
1572=item croak
1573
1574This is the XSUB-writer's interface to Perl's C<die> function. Use this
1575function the same way you use the C C<printf> function. See C<warn>.
1576
1577=item CvSTASH
1578
1579Returns the stash of the CV.
1580
e89caa19 1581 HV* CvSTASH( SV* sv )
cb1a09d0 1582
9cde0e7f 1583=item PL_DBsingle
cb1a09d0
AD
1584
1585When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1586boolean which indicates whether subs are being single-stepped.
5fb8527f 1587Single-stepping is automatically turned on after every step. This is the C
9cde0e7f 1588variable which corresponds to Perl's $DB::single variable. See C<PL_DBsub>.
cb1a09d0 1589
9cde0e7f 1590=item PL_DBsub
cb1a09d0
AD
1591
1592When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f 1593the SV which holds the name of the sub being debugged. This is the C
9cde0e7f 1594variable which corresponds to Perl's $DB::sub variable. See C<PL_DBsingle>.
cb1a09d0
AD
1595The sub name can be found by
1596
9cde0e7f 1597 SvPV( GvSV( PL_DBsub ), PL_na )
cb1a09d0 1598
9cde0e7f 1599=item PL_DBtrace
5fb8527f
PP
1600
1601Trace variable used when Perl is run in debugging mode, with the B<-d>
1602switch. This is the C variable which corresponds to Perl's $DB::trace
9cde0e7f 1603variable. See C<PL_DBsingle>.
5fb8527f 1604
cb1a09d0
AD
1605=item dMARK
1606
5fb8527f
PP
1607Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1608C<dORIGMARK>.
cb1a09d0
AD
1609
1610=item dORIGMARK
1611
1612Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1613
9cde0e7f 1614=item PL_dowarn
5fb8527f
PP
1615
1616The C variable which corresponds to Perl's $^W warning variable.
1617
cb1a09d0
AD
1618=item dSP
1619
924508f0
GS
1620Declares a local copy of perl's stack pointer for the XSUB, available via
1621the C<SP> macro. See C<SP>.
cb1a09d0
AD
1622
1623=item dXSARGS
1624
1625Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1626usually handled automatically by C<xsubpp>. Declares the C<items> variable
1627to indicate the number of items on the stack.
1628
5fb8527f
PP
1629=item dXSI32
1630
1631Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1632handled automatically by C<xsubpp>.
1633
491527d0
GS
1634=item do_binmode
1635
1636Switches filehandle to binmode. C<iotype> is what C<IoTYPE(io)> would
1637contain.
1638
1639 do_binmode(fp, iotype, TRUE);
1640
cb1a09d0
AD
1641=item ENTER
1642
1643Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1644
1645 ENTER;
1646
1647=item EXTEND
1648
1649Used to extend the argument stack for an XSUB's return values.
1650
ef50df4b 1651 EXTEND( sp, int x )
cb1a09d0 1652
e89caa19
GA
1653=item fbm_compile
1654
1655Analyses the string in order to make fast searches on it using fbm_instr() --
1656the Boyer-Moore algorithm.
1657
411d5715 1658 void fbm_compile(SV* sv, U32 flags)
e89caa19
GA
1659
1660=item fbm_instr
1661
1662Returns the location of the SV in the string delimited by C<str> and
1663C<strend>. It returns C<Nullch> if the string can't be found. The
1664C<sv> does not have to be fbm_compiled, but the search will not be as
1665fast then.
1666
411d5715 1667 char* fbm_instr(char *str, char *strend, SV *sv, U32 flags)
e89caa19 1668
cb1a09d0
AD
1669=item FREETMPS
1670
1671Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1672L<perlcall>.
1673
1674 FREETMPS;
1675
1676=item G_ARRAY
1677
54310121 1678Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
cb1a09d0
AD
1679
1680=item G_DISCARD
1681
1682Indicates that arguments returned from a callback should be discarded. See
1683L<perlcall>.
1684
1685=item G_EVAL
1686
1687Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1688
1689=item GIMME
1690
54310121
PP
1691A backward-compatible version of C<GIMME_V> which can only return
1692C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
1693
1694=item GIMME_V
1695
1696The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
1697C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
1698context, respectively.
cb1a09d0
AD
1699
1700=item G_NOARGS
1701
1702Indicates that no arguments are being sent to a callback. See L<perlcall>.
1703
1704=item G_SCALAR
1705
54310121
PP
1706Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
1707
faed5253
JO
1708=item gv_fetchmeth
1709
1710Returns the glob with the given C<name> and a defined subroutine or
9607fc9c 1711C<NULL>. The glob lives in the given C<stash>, or in the stashes
f86cebdf 1712accessible via @ISA and @UNIVERSAL.
faed5253 1713
9607fc9c 1714The argument C<level> should be either 0 or -1. If C<level==0>, as a
0a753a76
PP
1715side-effect creates a glob with the given C<name> in the given
1716C<stash> which in the case of success contains an alias for the
1717subroutine, and sets up caching info for this glob. Similarly for all
1718the searched stashes.
1719
9607fc9c
PP
1720This function grants C<"SUPER"> token as a postfix of the stash name.
1721
0a753a76
PP
1722The GV returned from C<gv_fetchmeth> may be a method cache entry,
1723which is not visible to Perl code. So when calling C<perl_call_sv>,
1724you should not use the GV directly; instead, you should use the
1725method's CV, which can be obtained from the GV with the C<GvCV> macro.
faed5253 1726
ef50df4b 1727 GV* gv_fetchmeth (HV* stash, char* name, STRLEN len, I32 level)
faed5253
JO
1728
1729=item gv_fetchmethod
1730
dc848c6f
PP
1731=item gv_fetchmethod_autoload
1732
faed5253 1733Returns the glob which contains the subroutine to call to invoke the
dc848c6f
PP
1734method on the C<stash>. In fact in the presense of autoloading this may
1735be the glob for "AUTOLOAD". In this case the corresponding variable
faed5253
JO
1736$AUTOLOAD is already setup.
1737
dc848c6f
PP
1738The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
1739lookup is performed if the given method is not present: non-zero means
1740yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
1741C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
1742non-zero C<autoload> parameter.
1743
1744These functions grant C<"SUPER"> token as a prefix of the method name.
1745
1746Note that if you want to keep the returned glob for a long time, you
1747need to check for it being "AUTOLOAD", since at the later time the call
faed5253
JO
1748may load a different subroutine due to $AUTOLOAD changing its value.
1749Use the glob created via a side effect to do this.
1750
dc848c6f
PP
1751These functions have the same side-effects and as C<gv_fetchmeth> with
1752C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
0a753a76 1753The warning against passing the GV returned by C<gv_fetchmeth> to
dc848c6f 1754C<perl_call_sv> apply equally to these functions.
faed5253 1755
ef50df4b
GS
1756 GV* gv_fetchmethod (HV* stash, char* name)
1757 GV* gv_fetchmethod_autoload (HV* stash, char* name, I32 autoload)
faed5253 1758
e89caa19
GA
1759=item G_VOID
1760
1761Used to indicate void context. See C<GIMME_V> and L<perlcall>.
1762
cb1a09d0
AD
1763=item gv_stashpv
1764
1765Returns a pointer to the stash for a specified package. If C<create> is set
1766then the package will be created if it does not already exist. If C<create>
1767is not set and the package does not exist then NULL is returned.
1768
ef50df4b 1769 HV* gv_stashpv (char* name, I32 create)
cb1a09d0
AD
1770
1771=item gv_stashsv
1772
1773Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1774
ef50df4b 1775 HV* gv_stashsv (SV* sv, I32 create)
cb1a09d0 1776
e5581bf4 1777=item GvSV
cb1a09d0 1778
e5581bf4 1779Return the SV from the GV.
44a8e56a 1780
1e422769
PP
1781=item HEf_SVKEY
1782
1783This flag, used in the length slot of hash entries and magic
1784structures, specifies the structure contains a C<SV*> pointer where a
1785C<char*> pointer is to be expected. (For information only--not to be used).
1786
1e422769
PP
1787=item HeHASH
1788
e89caa19 1789Returns the computed hash stored in the hash entry.
1e422769 1790
e89caa19 1791 U32 HeHASH(HE* he)
1e422769
PP
1792
1793=item HeKEY
1794
1795Returns the actual pointer stored in the key slot of the hash entry.
1796The pointer may be either C<char*> or C<SV*>, depending on the value of
1797C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1798are usually preferable for finding the value of a key.
1799
e89caa19 1800 char* HeKEY(HE* he)
1e422769
PP
1801
1802=item HeKLEN
1803
1804If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1805holds an C<SV*> key. Otherwise, holds the actual length of the key.
1806Can be assigned to. The C<HePV()> macro is usually preferable for finding
1807key lengths.
1808
e89caa19 1809 int HeKLEN(HE* he)
1e422769
PP
1810
1811=item HePV
1812
1813Returns the key slot of the hash entry as a C<char*> value, doing any
1814necessary dereferencing of possibly C<SV*> keys. The length of
1815the string is placed in C<len> (this is a macro, so do I<not> use
1816C<&len>). If you do not care about what the length of the key is,
9cde0e7f 1817you may use the global variable C<PL_na>. Remember though, that hash
1e422769
PP
1818keys in perl are free to contain embedded nulls, so using C<strlen()>
1819or similar is not a good way to find the length of hash keys.
1820This is very similar to the C<SvPV()> macro described elsewhere in
1821this document.
1822
e89caa19 1823 char* HePV(HE* he, STRLEN len)
1e422769
PP
1824
1825=item HeSVKEY
1826
1827Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1828does not contain an C<SV*> key.
1829
1830 HeSVKEY(HE* he)
1831
1832=item HeSVKEY_force
1833
1834Returns the key as an C<SV*>. Will create and return a temporary
1835mortal C<SV*> if the hash entry contains only a C<char*> key.
1836
1837 HeSVKEY_force(HE* he)
1838
1839=item HeSVKEY_set
1840
1841Sets the key to a given C<SV*>, taking care to set the appropriate flags
1842to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1843
1844 HeSVKEY_set(HE* he, SV* sv)
1845
1846=item HeVAL
1847
1848Returns the value slot (type C<SV*>) stored in the hash entry.
1849
1850 HeVAL(HE* he)
1851
cb1a09d0
AD
1852=item hv_clear
1853
1854Clears a hash, making it empty.
1855
ef50df4b 1856 void hv_clear (HV* tb)
cb1a09d0 1857
68dc0745
PP
1858=item hv_delayfree_ent
1859
1860Releases a hash entry, such as while iterating though the hash, but
1861delays actual freeing of key and value until the end of the current
1862statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
1863and C<hv_free_ent>.
1864
ef50df4b 1865 void hv_delayfree_ent (HV* hv, HE* entry)
68dc0745 1866
cb1a09d0
AD
1867=item hv_delete
1868
1869Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 1870and returned to the caller. The C<klen> is the length of the key. The
04343c6d 1871C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
cb1a09d0
AD
1872returned.
1873
ef50df4b 1874 SV* hv_delete (HV* tb, char* key, U32 klen, I32 flags)
cb1a09d0 1875
1e422769
PP
1876=item hv_delete_ent
1877
1878Deletes a key/value pair in the hash. The value SV is removed from the hash
1879and returned to the caller. The C<flags> value will normally be zero; if set
04343c6d 1880to G_DISCARD then NULL will be returned. C<hash> can be a valid precomputed
1e422769
PP
1881hash value, or 0 to ask for it to be computed.
1882
ef50df4b 1883 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash)
1e422769 1884
cb1a09d0
AD
1885=item hv_exists
1886
1887Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 1888C<klen> is the length of the key.
cb1a09d0 1889
ef50df4b 1890 bool hv_exists (HV* tb, char* key, U32 klen)
cb1a09d0 1891
1e422769
PP
1892=item hv_exists_ent
1893
1894Returns a boolean indicating whether the specified hash key exists. C<hash>
54310121 1895can be a valid precomputed hash value, or 0 to ask for it to be computed.
1e422769 1896
ef50df4b 1897 bool hv_exists_ent (HV* tb, SV* key, U32 hash)
1e422769 1898
cb1a09d0
AD
1899=item hv_fetch
1900
1901Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 1902C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
1903part of a store. Check that the return value is non-null before
1904dereferencing it to a C<SV*>.
1905
04343c6d
GS
1906See L<Understanding the Magic of Tied Hashes and Arrays> for more
1907information on how to use this function on tied hashes.
1908
ef50df4b 1909 SV** hv_fetch (HV* tb, char* key, U32 klen, I32 lval)
cb1a09d0 1910
1e422769
PP
1911=item hv_fetch_ent
1912
1913Returns the hash entry which corresponds to the specified key in the hash.
54310121 1914C<hash> must be a valid precomputed hash number for the given C<key>, or
1e422769
PP
19150 if you want the function to compute it. IF C<lval> is set then the
1916fetch will be part of a store. Make sure the return value is non-null
1917before accessing it. The return value when C<tb> is a tied hash
1918is a pointer to a static location, so be sure to make a copy of the
1919structure if you need to store it somewhere.
1920
04343c6d
GS
1921See L<Understanding the Magic of Tied Hashes and Arrays> for more
1922information on how to use this function on tied hashes.
1923
ef50df4b 1924 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash)
1e422769 1925
68dc0745
PP
1926=item hv_free_ent
1927
1928Releases a hash entry, such as while iterating though the hash. See
1929C<hv_iternext> and C<hv_delayfree_ent>.
1930
ef50df4b 1931 void hv_free_ent (HV* hv, HE* entry)
68dc0745 1932
cb1a09d0
AD
1933=item hv_iterinit
1934
1935Prepares a starting point to traverse a hash table.
1936
ef50df4b 1937 I32 hv_iterinit (HV* tb)
cb1a09d0 1938
c6601927
SI
1939Returns the number of keys in the hash (i.e. the same as C<HvKEYS(tb)>).
1940The return value is currently only meaningful for hashes without tie
1941magic.
1942
1943NOTE: Before version 5.004_65, C<hv_iterinit> used to return the number
1944of hash buckets that happen to be in use. If you still need that
1945esoteric value, you can get it through the macro C<HvFILL(tb)>.
fb73857a 1946
cb1a09d0
AD
1947=item hv_iterkey
1948
1949Returns the key from the current position of the hash iterator. See
1950C<hv_iterinit>.
1951
ef50df4b 1952 char* hv_iterkey (HE* entry, I32* retlen)
cb1a09d0 1953
1e422769 1954=item hv_iterkeysv
3fe9a6f1 1955
1e422769
PP
1956Returns the key as an C<SV*> from the current position of the hash
1957iterator. The return value will always be a mortal copy of the
1958key. Also see C<hv_iterinit>.
1959
ef50df4b 1960 SV* hv_iterkeysv (HE* entry)
1e422769 1961
cb1a09d0
AD
1962=item hv_iternext
1963
1964Returns entries from a hash iterator. See C<hv_iterinit>.
1965
ef50df4b 1966 HE* hv_iternext (HV* tb)
cb1a09d0
AD
1967
1968=item hv_iternextsv
1969
1970Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1971operation.
1972
e89caa19 1973 SV* hv_iternextsv (HV* hv, char** key, I32* retlen)
cb1a09d0
AD
1974
1975=item hv_iterval
1976
1977Returns the value from the current position of the hash iterator. See
1978C<hv_iterkey>.
1979
ef50df4b 1980 SV* hv_iterval (HV* tb, HE* entry)
cb1a09d0
AD
1981
1982=item hv_magic
1983
1984Adds magic to a hash. See C<sv_magic>.
1985
ef50df4b 1986 void hv_magic (HV* hv, GV* gv, int how)
cb1a09d0
AD
1987
1988=item HvNAME
1989
1990Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1991
e89caa19 1992 char* HvNAME (HV* stash)
cb1a09d0
AD
1993
1994=item hv_store
1995
1996Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
54310121 1997the length of the key. The C<hash> parameter is the precomputed hash
cb1a09d0 1998value; if it is zero then Perl will compute it. The return value will be
04343c6d
GS
1999NULL if the operation failed or if the value did not need to be actually
2000stored within the hash (as in the case of tied hashes). Otherwise it can
2001be dereferenced to get the original C<SV*>. Note that the caller is
2002responsible for suitably incrementing the reference count of C<val>
2003before the call, and decrementing it if the function returned NULL.
2004
2005See L<Understanding the Magic of Tied Hashes and Arrays> for more
2006information on how to use this function on tied hashes.
cb1a09d0 2007
ef50df4b 2008 SV** hv_store (HV* tb, char* key, U32 klen, SV* val, U32 hash)
cb1a09d0 2009
1e422769
PP
2010=item hv_store_ent
2011
2012Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
54310121 2013parameter is the precomputed hash value; if it is zero then Perl will
1e422769 2014compute it. The return value is the new hash entry so created. It will be
04343c6d
GS
2015NULL if the operation failed or if the value did not need to be actually
2016stored within the hash (as in the case of tied hashes). Otherwise the
2017contents of the return value can be accessed using the C<He???> macros
2018described here. Note that the caller is responsible for suitably
2019incrementing the reference count of C<val> before the call, and decrementing
2020it if the function returned NULL.
2021
2022See L<Understanding the Magic of Tied Hashes and Arrays> for more
2023information on how to use this function on tied hashes.
1e422769 2024
ef50df4b 2025 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash)
1e422769 2026
cb1a09d0
AD
2027=item hv_undef
2028
2029Undefines the hash.
2030
ef50df4b 2031 void hv_undef (HV* tb)
cb1a09d0
AD
2032
2033=item isALNUM
2034
2035Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 2036character or digit.
cb1a09d0 2037
e89caa19 2038 int isALNUM (char c)
cb1a09d0
AD
2039
2040=item isALPHA
2041
5fb8527f 2042Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
2043character.
2044
e89caa19 2045 int isALPHA (char c)
cb1a09d0
AD
2046
2047=item isDIGIT
2048
2049Returns a boolean indicating whether the C C<char> is an ascii digit.
2050
e89caa19 2051 int isDIGIT (char c)
cb1a09d0
AD
2052
2053=item isLOWER
2054
2055Returns a boolean indicating whether the C C<char> is a lowercase character.
2056
e89caa19 2057 int isLOWER (char c)
cb1a09d0
AD
2058
2059=item isSPACE
2060
2061Returns a boolean indicating whether the C C<char> is whitespace.
2062
e89caa19 2063 int isSPACE (char c)
cb1a09d0
AD
2064
2065=item isUPPER
2066
2067Returns a boolean indicating whether the C C<char> is an uppercase character.
2068
e89caa19 2069 int isUPPER (char c)
cb1a09d0
AD
2070
2071=item items
2072
2073Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
2074stack. See L<perlxs/"Variable-length Parameter Lists">.
2075
2076=item ix
2077
2078Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
2079was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
2080
2081=item LEAVE
2082
2083Closing bracket on a callback. See C<ENTER> and L<perlcall>.
2084
2085 LEAVE;
2086
e89caa19
GA
2087=item looks_like_number
2088
2089Test if an the content of an SV looks like a number (or is a number).
2090
2091 int looks_like_number(SV*)
2092
2093
cb1a09d0
AD
2094=item MARK
2095
5fb8527f 2096Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
2097
2098=item mg_clear
2099
2100Clear something magical that the SV represents. See C<sv_magic>.
2101
ef50df4b 2102 int mg_clear (SV* sv)
cb1a09d0
AD
2103
2104=item mg_copy
2105
2106Copies the magic from one SV to another. See C<sv_magic>.
2107
ef50df4b 2108 int mg_copy (SV *, SV *, char *, STRLEN)
cb1a09d0
AD
2109
2110=item mg_find
2111
2112Finds the magic pointer for type matching the SV. See C<sv_magic>.
2113
ef50df4b 2114 MAGIC* mg_find (SV* sv, int type)
cb1a09d0
AD
2115
2116=item mg_free
2117
2118Free any magic storage used by the SV. See C<sv_magic>.
2119
ef50df4b 2120 int mg_free (SV* sv)
cb1a09d0
AD
2121
2122=item mg_get
2123
2124Do magic after a value is retrieved from the SV. See C<sv_magic>.
2125
ef50df4b 2126 int mg_get (SV* sv)
cb1a09d0
AD
2127
2128=item mg_len
2129
2130Report on the SV's length. See C<sv_magic>.
2131
ef50df4b 2132 U32 mg_len (SV* sv)
cb1a09d0
AD
2133
2134=item mg_magical
2135
2136Turns on the magical status of an SV. See C<sv_magic>.
2137
ef50df4b 2138 void mg_magical (SV* sv)
cb1a09d0
AD
2139
2140=item mg_set
2141
2142Do magic after a value is assigned to the SV. See C<sv_magic>.
2143
ef50df4b 2144 int mg_set (SV* sv)
cb1a09d0
AD
2145
2146=item Move
2147
2148The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
2149source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 2150the type. Can do overlapping moves. See also C<Copy>.
cb1a09d0 2151
e89caa19 2152 void Move( s, d, n, t )
cb1a09d0 2153
9cde0e7f 2154=item PL_na
cb1a09d0
AD
2155
2156A variable which may be used with C<SvPV> to tell Perl to calculate the
2157string length.
2158
2159=item New
2160
2161The XSUB-writer's interface to the C C<malloc> function.
2162
e89caa19 2163 void* New( x, void *ptr, int size, type )
cb1a09d0
AD
2164
2165=item newAV
2166
5f05dabc 2167Creates a new AV. The reference count is set to 1.
cb1a09d0 2168
ef50df4b 2169 AV* newAV (void)
cb1a09d0 2170
e89caa19
GA
2171=item Newc
2172
2173The XSUB-writer's interface to the C C<malloc> function, with cast.
2174
2175 void* Newc( x, void *ptr, int size, type, cast )
2176
5476c433
JD
2177=item newCONSTSUB
2178
2179Creates a constant sub equivalent to Perl C<sub FOO () { 123 }>
2180which is eligible for inlining at compile-time.
2181
2182 void newCONSTSUB(HV* stash, char* name, SV* sv)
2183
cb1a09d0
AD
2184=item newHV
2185
5f05dabc 2186Creates a new HV. The reference count is set to 1.
cb1a09d0 2187
ef50df4b 2188 HV* newHV (void)
cb1a09d0 2189
5f05dabc 2190=item newRV_inc
cb1a09d0 2191
5f05dabc 2192Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
2193incremented.
2194
ef50df4b 2195 SV* newRV_inc (SV* ref)
5f05dabc
PP
2196
2197For historical reasons, "newRV" is a synonym for "newRV_inc".
2198
2199=item newRV_noinc
2200
2201Creates an RV wrapper for an SV. The reference count for the original
2202SV is B<not> incremented.
2203
ef50df4b 2204 SV* newRV_noinc (SV* ref)
cb1a09d0 2205
8c52afec 2206=item NEWSV
cb1a09d0 2207
e89caa19
GA
2208Creates a new SV. A non-zero C<len> parameter indicates the number of
2209bytes of preallocated string space the SV should have. An extra byte
2210for a tailing NUL is also reserved. (SvPOK is not set for the SV even
2211if string space is allocated.) The reference count for the new SV is
2212set to 1. C<id> is an integer id between 0 and 1299 (used to identify
2213leaks).
cb1a09d0 2214
ef50df4b 2215 SV* NEWSV (int id, STRLEN len)
cb1a09d0
AD
2216
2217=item newSViv
2218
07fa94a1
JO
2219Creates a new SV and copies an integer into it. The reference count for the
2220SV is set to 1.
cb1a09d0 2221
ef50df4b 2222 SV* newSViv (IV i)
cb1a09d0
AD
2223
2224=item newSVnv
2225
07fa94a1
JO
2226Creates a new SV and copies a double into it. The reference count for the
2227SV is set to 1.
cb1a09d0 2228
ef50df4b 2229 SV* newSVnv (NV i)
cb1a09d0
AD
2230
2231=item newSVpv
2232
07fa94a1
JO
2233Creates a new SV and copies a string into it. The reference count for the
2234SV is set to 1. If C<len> is zero then Perl will compute the length.
cb1a09d0 2235
ef50df4b 2236 SV* newSVpv (char* s, STRLEN len)
cb1a09d0 2237
e89caa19
GA
2238=item newSVpvf
2239
2240Creates a new SV an initialize it with the string formatted like
2241C<sprintf>.
2242
2243 SV* newSVpvf(const char* pat, ...);
2244
9da1e3b5
MUN
2245=item newSVpvn
2246
2247Creates a new SV and copies a string into it. The reference count for the
2248SV is set to 1. If C<len> is zero then Perl will create a zero length
2249string.
2250
ef50df4b 2251 SV* newSVpvn (char* s, STRLEN len)
9da1e3b5 2252
cb1a09d0
AD
2253=item newSVrv
2254
2255Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 2256it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 2257be blessed in the specified package. The new SV is returned and its
5f05dabc 2258reference count is 1.
8ebc5c01 2259
ef50df4b 2260 SV* newSVrv (SV* rv, char* classname)
cb1a09d0
AD
2261
2262=item newSVsv
2263
5fb8527f 2264Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0 2265
ef50df4b 2266 SV* newSVsv (SV* old)
cb1a09d0
AD
2267
2268=item newXS
2269
2270Used by C<xsubpp> to hook up XSUBs as Perl subs.
2271
2272=item newXSproto
2273
2274Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
2275the subs.
2276
e89caa19
GA
2277=item Newz
2278
2279The XSUB-writer's interface to the C C<malloc> function. The allocated
2280memory is zeroed with C<memzero>.
2281
2282 void* Newz( x, void *ptr, int size, type )
2283
cb1a09d0
AD
2284=item Nullav
2285
2286Null AV pointer.
2287
2288=item Nullch
2289
2290Null character pointer.
2291
2292=item Nullcv
2293
2294Null CV pointer.
2295
2296=item Nullhv
2297
2298Null HV pointer.
2299
2300=item Nullsv
2301
2302Null SV pointer.
2303
2304=item ORIGMARK
2305
2306The original stack mark for the XSUB. See C<dORIGMARK>.
2307
2308=item perl_alloc
2309
2310Allocates a new Perl interpreter. See L<perlembed>.
2311
2312=item perl_call_argv
2313
2314Performs a callback to the specified Perl sub. See L<perlcall>.
2315
ef50df4b 2316 I32 perl_call_argv (char* subname, I32 flags, char** argv)
cb1a09d0
AD
2317
2318=item perl_call_method
2319
2320Performs a callback to the specified Perl method. The blessed object must
2321be on the stack. See L<perlcall>.
2322
ef50df4b 2323 I32 perl_call_method (char* methname, I32 flags)
cb1a09d0
AD
2324
2325=item perl_call_pv
2326
2327Performs a callback to the specified Perl sub. See L<perlcall>.
2328
ef50df4b 2329 I32 perl_call_pv (char* subname, I32 flags)
cb1a09d0
AD
2330
2331=item perl_call_sv
2332
2333Performs a callback to the Perl sub whose name is in the SV. See
2334L<perlcall>.
2335
ef50df4b 2336 I32 perl_call_sv (SV* sv, I32 flags)
cb1a09d0
AD
2337
2338=item perl_construct
2339
2340Initializes a new Perl interpreter. See L<perlembed>.
2341
2342=item perl_destruct
2343
2344Shuts down a Perl interpreter. See L<perlembed>.
2345
2346=item perl_eval_sv
2347
2348Tells Perl to C<eval> the string in the SV.
2349
ef50df4b 2350 I32 perl_eval_sv (SV* sv, I32 flags)
cb1a09d0 2351
137443ea
PP
2352=item perl_eval_pv
2353
2354Tells Perl to C<eval> the given string and return an SV* result.
2355
ef50df4b 2356 SV* perl_eval_pv (char* p, I32 croak_on_error)
137443ea 2357
cb1a09d0
AD
2358=item perl_free
2359
2360Releases a Perl interpreter. See L<perlembed>.
2361
2362=item perl_get_av
2363
2364Returns the AV of the specified Perl array. If C<create> is set and the
2365Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2366set and the variable does not exist then NULL is returned.
cb1a09d0 2367
ef50df4b 2368 AV* perl_get_av (char* name, I32 create)
cb1a09d0
AD
2369
2370=item perl_get_cv
2371
2372Returns the CV of the specified Perl sub. If C<create> is set and the Perl
2373variable does not exist then it will be created. If C<create> is not
04343c6d 2374set and the variable does not exist then NULL is returned.
cb1a09d0 2375
ef50df4b 2376 CV* perl_get_cv (char* name, I32 create)
cb1a09d0
AD
2377
2378=item perl_get_hv
2379
2380Returns the HV of the specified Perl hash. If C<create> is set and the Perl
2381variable does not exist then it will be created. If C<create> is not
04343c6d 2382set and the variable does not exist then NULL is returned.
cb1a09d0 2383
ef50df4b 2384 HV* perl_get_hv (char* name, I32 create)
cb1a09d0
AD
2385
2386=item perl_get_sv
2387
2388Returns the SV of the specified Perl scalar. If C<create> is set and the
2389Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2390set and the variable does not exist then NULL is returned.
cb1a09d0 2391
ef50df4b 2392 SV* perl_get_sv (char* name, I32 create)
cb1a09d0
AD
2393
2394=item perl_parse
2395
2396Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2397
2398=item perl_require_pv
2399
2400Tells Perl to C<require> a module.
2401
ef50df4b 2402 void perl_require_pv (char* pv)
cb1a09d0
AD
2403
2404=item perl_run
2405
2406Tells a Perl interpreter to run. See L<perlembed>.
2407
2408=item POPi
2409
2410Pops an integer off the stack.
2411
e89caa19 2412 int POPi()
cb1a09d0
AD
2413
2414=item POPl
2415
2416Pops a long off the stack.
2417
e89caa19 2418 long POPl()
cb1a09d0
AD
2419
2420=item POPp
2421
2422Pops a string off the stack.
2423
e89caa19 2424 char* POPp()
cb1a09d0
AD
2425
2426=item POPn
2427
2428Pops a double off the stack.
2429
e89caa19 2430 double POPn()
cb1a09d0
AD
2431
2432=item POPs
2433
2434Pops an SV off the stack.
2435
e89caa19 2436 SV* POPs()
cb1a09d0
AD
2437
2438=item PUSHMARK
2439
2440Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2441
2442 PUSHMARK(p)
2443
2444=item PUSHi
2445
2446Push an integer onto the stack. The stack must have room for this element.
189b2af5 2447Handles 'set' magic. See C<XPUSHi>.
cb1a09d0 2448
e89caa19 2449 void PUSHi(int d)
cb1a09d0
AD
2450
2451=item PUSHn
2452
2453Push a double onto the stack. The stack must have room for this element.
189b2af5 2454Handles 'set' magic. See C<XPUSHn>.
cb1a09d0 2455
e89caa19 2456 void PUSHn(double d)
cb1a09d0
AD
2457
2458=item PUSHp
2459
2460Push a string onto the stack. The stack must have room for this element.
189b2af5
GS
2461The C<len> indicates the length of the string. Handles 'set' magic. See
2462C<XPUSHp>.
cb1a09d0 2463
e89caa19 2464 void PUSHp(char *c, int len )
cb1a09d0
AD
2465
2466=item PUSHs
2467
189b2af5
GS
2468Push an SV onto the stack. The stack must have room for this element. Does
2469not handle 'set' magic. See C<XPUSHs>.
cb1a09d0 2470
e89caa19
GA
2471 void PUSHs(sv)
2472
2473=item PUSHu
2474
2475Push an unsigned integer onto the stack. The stack must have room for
2476this element. See C<XPUSHu>.
2477
2478 void PUSHu(unsigned int d)
2479
cb1a09d0
AD
2480
2481=item PUTBACK
2482
2483Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2484See C<PUSHMARK> and L<perlcall> for other uses.
2485
2486 PUTBACK;
2487
2488=item Renew
2489
2490The XSUB-writer's interface to the C C<realloc> function.
2491
e89caa19 2492 void* Renew( void *ptr, int size, type )
cb1a09d0
AD
2493
2494=item Renewc
2495
2496The XSUB-writer's interface to the C C<realloc> function, with cast.
2497
e89caa19 2498 void* Renewc( void *ptr, int size, type, cast )
cb1a09d0
AD
2499
2500=item RETVAL
2501
2502Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
2503This is always the proper type for the XSUB.
2504See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
2505
2506=item safefree
2507
2508The XSUB-writer's interface to the C C<free> function.
2509
2510=item safemalloc
2511
2512The XSUB-writer's interface to the C C<malloc> function.
2513
2514=item saferealloc
2515
2516The XSUB-writer's interface to the C C<realloc> function.
2517
2518=item savepv
2519
2520Copy a string to a safe spot. This does not use an SV.
2521
ef50df4b 2522 char* savepv (char* sv)
cb1a09d0
AD
2523
2524=item savepvn
2525
2526Copy a string to a safe spot. The C<len> indicates number of bytes to
2527copy. This does not use an SV.
2528
ef50df4b 2529 char* savepvn (char* sv, I32 len)
cb1a09d0
AD
2530
2531=item SAVETMPS
2532
2533Opening bracket for temporaries on a callback. See C<FREETMPS> and
2534L<perlcall>.
2535
2536 SAVETMPS;
2537
2538=item SP
2539
2540Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2541C<SPAGAIN>.
2542
2543=item SPAGAIN
2544
54310121 2545Refetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
2546
2547 SPAGAIN;
2548
2549=item ST
2550
2551Used to access elements on the XSUB's stack.
2552
e89caa19 2553 SV* ST(int x)
cb1a09d0
AD
2554
2555=item strEQ
2556
2557Test two strings to see if they are equal. Returns true or false.
2558
e89caa19 2559 int strEQ( char *s1, char *s2 )
cb1a09d0
AD
2560
2561=item strGE
2562
2563Test two strings to see if the first, C<s1>, is greater than or equal to the
2564second, C<s2>. Returns true or false.
2565
e89caa19 2566 int strGE( char *s1, char *s2 )
cb1a09d0
AD
2567
2568=item strGT
2569
2570Test two strings to see if the first, C<s1>, is greater than the second,
2571C<s2>. Returns true or false.
2572
e89caa19 2573 int strGT( char *s1, char *s2 )
cb1a09d0
AD
2574
2575=item strLE
2576
2577Test two strings to see if the first, C<s1>, is less than or equal to the
2578second, C<s2>. Returns true or false.
2579
e89caa19 2580 int strLE( char *s1, char *s2 )
cb1a09d0
AD
2581
2582=item strLT
2583
2584Test two strings to see if the first, C<s1>, is less than the second,
2585C<s2>. Returns true or false.
2586
e89caa19 2587 int strLT( char *s1, char *s2 )
cb1a09d0
AD
2588
2589=item strNE
2590
2591Test two strings to see if they are different. Returns true or false.
2592
e89caa19 2593 int strNE( char *s1, char *s2 )
cb1a09d0
AD
2594
2595=item strnEQ
2596
2597Test two strings to see if they are equal. The C<len> parameter indicates
2598the number of bytes to compare. Returns true or false.
2599
e89caa19 2600 int strnEQ( char *s1, char *s2 )
cb1a09d0
AD
2601
2602=item strnNE
2603
2604Test two strings to see if they are different. The C<len> parameter
2605indicates the number of bytes to compare. Returns true or false.
2606
e89caa19 2607 int strnNE( char *s1, char *s2, int len )
cb1a09d0
AD
2608
2609=item sv_2mortal
2610
2611Marks an SV as mortal. The SV will be destroyed when the current context
2612ends.
2613
ef50df4b 2614 SV* sv_2mortal (SV* sv)
cb1a09d0
AD
2615
2616=item sv_bless
2617
2618Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
2619must be designated by its stash (see C<gv_stashpv()>). The reference count
2620of the SV is unaffected.
cb1a09d0 2621
ef50df4b 2622 SV* sv_bless (SV* sv, HV* stash)
cb1a09d0 2623
ef50df4b 2624=item sv_catpv
189b2af5 2625
ef50df4b
GS
2626Concatenates the string onto the end of the string which is in the SV.
2627Handles 'get' magic, but not 'set' magic. See C<sv_catpv_mg>.
189b2af5 2628
ef50df4b 2629 void sv_catpv (SV* sv, char* ptr)
189b2af5 2630
ef50df4b 2631=item sv_catpv_mg
cb1a09d0 2632
ef50df4b 2633Like C<sv_catpv>, but also handles 'set' magic.
cb1a09d0 2634
ef50df4b 2635 void sv_catpvn (SV* sv, char* ptr)
cb1a09d0
AD
2636
2637=item sv_catpvn
2638
2639Concatenates the string onto the end of the string which is in the SV. The
189b2af5 2640C<len> indicates number of bytes to copy. Handles 'get' magic, but not
ef50df4b 2641'set' magic. See C<sv_catpvn_mg>.
cb1a09d0 2642
ef50df4b
GS
2643 void sv_catpvn (SV* sv, char* ptr, STRLEN len)
2644
2645=item sv_catpvn_mg
2646
2647Like C<sv_catpvn>, but also handles 'set' magic.
2648
2649 void sv_catpvn_mg (SV* sv, char* ptr, STRLEN len)
cb1a09d0 2650
46fc3d4c
PP
2651=item sv_catpvf
2652
2653Processes its arguments like C<sprintf> and appends the formatted output
189b2af5
GS
2654to an SV. Handles 'get' magic, but not 'set' magic. C<SvSETMAGIC()> must
2655typically be called after calling this function to handle 'set' magic.
46fc3d4c 2656
ef50df4b
GS
2657 void sv_catpvf (SV* sv, const char* pat, ...)
2658
2659=item sv_catpvf_mg
2660
2661Like C<sv_catpvf>, but also handles 'set' magic.
2662
2663 void sv_catpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 2664
cb1a09d0
AD
2665=item sv_catsv
2666
5fb8527f 2667Concatenates the string from SV C<ssv> onto the end of the string in SV
ef50df4b
GS
2668C<dsv>. Handles 'get' magic, but not 'set' magic. See C<sv_catsv_mg>.
2669
2670 void sv_catsv (SV* dsv, SV* ssv)
2671
2672=item sv_catsv_mg
cb1a09d0 2673
ef50df4b
GS
2674Like C<sv_catsv>, but also handles 'set' magic.
2675
2676 void sv_catsv_mg (SV* dsv, SV* ssv)
cb1a09d0 2677
e89caa19
GA
2678=item sv_chop
2679
2680Efficient removal of characters from the beginning of the string
2681buffer. SvPOK(sv) must be true and the C<ptr> must be a pointer to
2682somewhere inside the string buffer. The C<ptr> becomes the first
2683character of the adjusted string.
2684
2685 void sv_chop(SV* sv, char *ptr)
2686
2687
5fb8527f
PP
2688=item sv_cmp
2689
2690Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2691string in C<sv1> is less than, equal to, or greater than the string in
2692C<sv2>.
2693
ef50df4b 2694 I32 sv_cmp (SV* sv1, SV* sv2)
5fb8527f 2695
cb1a09d0
AD
2696=item SvCUR
2697
2698Returns the length of the string which is in the SV. See C<SvLEN>.
2699
e89caa19 2700 int SvCUR (SV* sv)
cb1a09d0
AD
2701
2702=item SvCUR_set
2703
2704Set the length of the string which is in the SV. See C<SvCUR>.
2705
e89caa19 2706 void SvCUR_set (SV* sv, int val )
cb1a09d0 2707
5fb8527f
PP
2708=item sv_dec
2709
5f05dabc 2710Auto-decrement of the value in the SV.
5fb8527f 2711
ef50df4b 2712 void sv_dec (SV* sv)
5fb8527f 2713
e89caa19
GA
2714=item sv_derived_from
2715
2716Returns a boolean indicating whether the SV is a subclass of the
2717specified class.
2718
2719 int sv_derived_from(SV* sv, char* class)
2720
9abd00ed
GS
2721=item sv_derived_from
2722
2723Returns a boolean indicating whether the SV is derived from the specified
2724class. This is the function that implements C<UNIVERSAL::isa>. It works
2725for class names as well as for objects.
2726
2727 bool sv_derived_from _((SV* sv, char* name));
2728
cb1a09d0
AD
2729=item SvEND
2730
2731Returns a pointer to the last character in the string which is in the SV.
2732See C<SvCUR>. Access the character as
2733
e89caa19 2734 char* SvEND(sv)
cb1a09d0 2735
5fb8527f
PP
2736=item sv_eq
2737
2738Returns a boolean indicating whether the strings in the two SVs are
2739identical.
2740
ef50df4b 2741 I32 sv_eq (SV* sv1, SV* sv2)
5fb8527f 2742
189b2af5
GS
2743=item SvGETMAGIC
2744
2745Invokes C<mg_get> on an SV if it has 'get' magic. This macro evaluates
2746its argument more than once.
2747
2748 void SvGETMAGIC( SV *sv )
2749
cb1a09d0
AD
2750=item SvGROW
2751
e89caa19
GA
2752Expands the character buffer in the SV so that it has room for the
2753indicated number of bytes (remember to reserve space for an extra
2754trailing NUL character). Calls C<sv_grow> to perform the expansion if
2755necessary. Returns a pointer to the character buffer.
cb1a09d0 2756
e89caa19 2757 char* SvGROW( SV* sv, int len )
cb1a09d0 2758
5fb8527f
PP
2759=item sv_grow
2760
2761Expands the character buffer in the SV. This will use C<sv_unref> and will
2762upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2763Use C<SvGROW>.
2764
2765=item sv_inc
2766
07fa94a1 2767Auto-increment of the value in the SV.
5fb8527f 2768
ef50df4b 2769 void sv_inc (SV* sv)
5fb8527f 2770
e89caa19
GA
2771=item sv_insert
2772
2773Inserts a string at the specified offset/length within the SV.
2774Similar to the Perl substr() function.
2775
2776 void sv_insert(SV *sv, STRLEN offset, STRLEN len,
2777 char *str, STRLEN strlen)
2778
cb1a09d0
AD
2779=item SvIOK
2780
2781Returns a boolean indicating whether the SV contains an integer.
2782
e89caa19 2783 int SvIOK (SV* SV)
cb1a09d0
AD
2784
2785=item SvIOK_off
2786
2787Unsets the IV status of an SV.
2788
e89caa19 2789 void SvIOK_off (SV* sv)
cb1a09d0
AD
2790
2791=item SvIOK_on
2792
2793Tells an SV that it is an integer.
2794
e89caa19 2795 void SvIOK_on (SV* sv)
cb1a09d0 2796
5fb8527f
PP
2797=item SvIOK_only
2798
2799Tells an SV that it is an integer and disables all other OK bits.
2800
e89caa19 2801 void SvIOK_only (SV* sv)
5fb8527f 2802
cb1a09d0
AD
2803=item SvIOKp
2804
2805Returns a boolean indicating whether the SV contains an integer. Checks the
2806B<private> setting. Use C<SvIOK>.
2807
e89caa19 2808 int SvIOKp (SV* SV)
cb1a09d0
AD
2809
2810=item sv_isa
2811
2812Returns a boolean indicating whether the SV is blessed into the specified
9abd00ed 2813class. This does not check for subtypes; use C<sv_derived_from> to verify
cb1a09d0
AD
2814an inheritance relationship.
2815
ef50df4b 2816 int sv_isa (SV* sv, char* name)
cb1a09d0 2817
cb1a09d0
AD
2818=item sv_isobject
2819
2820Returns a boolean indicating whether the SV is an RV pointing to a blessed
2821object. If the SV is not an RV, or if the object is not blessed, then this
2822will return false.
2823
ef50df4b 2824 int sv_isobject (SV* sv)
cb1a09d0 2825
e89caa19
GA
2826=item SvIV
2827
2828Returns the integer which is in the SV.
2829
9abd00ed 2830 int SvIV (SV* sv)
a59f3522 2831
cb1a09d0
AD
2832=item SvIVX
2833
2834Returns the integer which is stored in the SV.
2835
e89caa19 2836 int SvIVX (SV* sv)
cb1a09d0
AD
2837
2838=item SvLEN
2839
2840Returns the size of the string buffer in the SV. See C<SvCUR>.
2841
e89caa19 2842 int SvLEN (SV* sv)
cb1a09d0 2843
5fb8527f
PP
2844=item sv_len
2845
2846Returns the length of the string in the SV. Use C<SvCUR>.
2847
ef50df4b 2848 STRLEN sv_len (SV* sv)
5fb8527f 2849
cb1a09d0
AD
2850=item sv_magic
2851
2852Adds magic to an SV.
2853
ef50df4b 2854 void sv_magic (SV* sv, SV* obj, int how, char* name, I32 namlen)
cb1a09d0
AD
2855
2856=item sv_mortalcopy
2857
2858Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 2859as mortal.
cb1a09d0 2860
ef50df4b 2861 SV* sv_mortalcopy (SV* oldsv)
cb1a09d0 2862
cb1a09d0
AD
2863=item sv_newmortal
2864
5f05dabc 2865Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0 2866
ef50df4b 2867 SV* sv_newmortal (void)
cb1a09d0 2868
cb1a09d0
AD
2869=item SvNIOK
2870
2871Returns a boolean indicating whether the SV contains a number, integer or
2872double.
2873
e89caa19 2874 int SvNIOK (SV* SV)
cb1a09d0
AD
2875
2876=item SvNIOK_off
2877
2878Unsets the NV/IV status of an SV.
2879
e89caa19 2880 void SvNIOK_off (SV* sv)
cb1a09d0
AD
2881
2882=item SvNIOKp
2883
2884Returns a boolean indicating whether the SV contains a number, integer or
2885double. Checks the B<private> setting. Use C<SvNIOK>.
2886
e89caa19
GA
2887 int SvNIOKp (SV* SV)
2888
9cde0e7f 2889=item PL_sv_no
e89caa19 2890
9cde0e7f 2891This is the C<false> SV. See C<PL_sv_yes>. Always refer to this as C<&PL_sv_no>.
cb1a09d0
AD
2892
2893=item SvNOK
2894
2895Returns a boolean indicating whether the SV contains a double.
2896
e89caa19 2897 int SvNOK (SV* SV)
cb1a09d0
AD
2898
2899=item SvNOK_off
2900
2901Unsets the NV status of an SV.
2902
e89caa19 2903 void SvNOK_off (SV* sv)
cb1a09d0
AD
2904
2905=item SvNOK_on
2906
2907Tells an SV that it is a double.
2908
e89caa19 2909 void SvNOK_on (SV* sv)
cb1a09d0 2910
5fb8527f
PP
2911=item SvNOK_only
2912
2913Tells an SV that it is a double and disables all other OK bits.
2914
e89caa19 2915 void SvNOK_only (SV* sv)
5fb8527f 2916
cb1a09d0
AD
2917=item SvNOKp
2918
2919Returns a boolean indicating whether the SV contains a double. Checks the
2920B<private> setting. Use C<SvNOK>.
2921
e89caa19 2922 int SvNOKp (SV* SV)
cb1a09d0
AD
2923
2924=item SvNV
2925
2926Returns the double which is stored in the SV.
2927
e89caa19 2928 double SvNV (SV* sv)
cb1a09d0
AD
2929
2930=item SvNVX
2931
2932Returns the double which is stored in the SV.
2933
e89caa19
GA
2934 double SvNVX (SV* sv)
2935
2936=item SvOK
2937
2938Returns a boolean indicating whether the value is an SV.
2939
2940 int SvOK (SV* sv)
2941
2942=item SvOOK
2943
2944Returns a boolean indicating whether the SvIVX is a valid offset value
2945for the SvPVX. This hack is used internally to speed up removal of
2946characters from the beginning of a SvPV. When SvOOK is true, then the
2947start of the allocated string buffer is really (SvPVX - SvIVX).
2948
9cde0e7f 2949 int SvOOK(SV* sv)
cb1a09d0
AD
2950
2951=item SvPOK
2952
2953Returns a boolean indicating whether the SV contains a character string.
2954
e89caa19 2955 int SvPOK (SV* SV)
cb1a09d0
AD
2956
2957=item SvPOK_off
2958
2959Unsets the PV status of an SV.
2960
e89caa19 2961 void SvPOK_off (SV* sv)
cb1a09d0
AD
2962
2963=item SvPOK_on
2964
2965Tells an SV that it is a string.
2966
e89caa19 2967 void SvPOK_on (SV* sv)
cb1a09d0 2968
5fb8527f
PP
2969=item SvPOK_only
2970
2971Tells an SV that it is a string and disables all other OK bits.
2972
e89caa19 2973 void SvPOK_only (SV* sv)
5fb8527f 2974
cb1a09d0
AD
2975=item SvPOKp
2976
2977Returns a boolean indicating whether the SV contains a character string.
2978Checks the B<private> setting. Use C<SvPOK>.
2979
e89caa19 2980 int SvPOKp (SV* SV)
cb1a09d0
AD
2981
2982=item SvPV
2983
2984Returns a pointer to the string in the SV, or a stringified form of the SV
9cde0e7f 2985if the SV does not contain a string. If C<len> is C<PL_na> then Perl will
189b2af5 2986handle the length on its own. Handles 'get' magic.
cb1a09d0 2987
e89caa19
GA
2988 char* SvPV (SV* sv, int len )
2989
2990=item SvPV_force
2991
2992Like <SvPV> but will force the SV into becoming a string (SvPOK). You
2993want force if you are going to update the SvPVX directly.
2994
2995 char* SvPV_force(SV* sv, int len)
2996
cb1a09d0
AD
2997
2998=item SvPVX
2999
3000Returns a pointer to the string in the SV. The SV must contain a string.
3001
e89caa19 3002 char* SvPVX (SV* sv)
cb1a09d0
AD
3003
3004=item SvREFCNT
3005
5f05dabc 3006Returns the value of the object's reference count.
cb1a09d0 3007
e89caa19 3008 int SvREFCNT (SV* sv)
cb1a09d0
AD
3009
3010=item SvREFCNT_dec
3011
5f05dabc 3012Decrements the reference count of the given SV.
cb1a09d0 3013
e89caa19 3014 void SvREFCNT_dec (SV* sv)
cb1a09d0
AD
3015
3016=item SvREFCNT_inc
3017
5f05dabc 3018Increments the reference count of the given SV.
cb1a09d0 3019
e89caa19 3020 void SvREFCNT_inc (SV* sv)
cb1a09d0
AD
3021
3022=item SvROK
3023
3024Tests if the SV is an RV.
3025
e89caa19 3026 int SvROK (SV* sv)
cb1a09d0
AD
3027
3028=item SvROK_off
3029
3030Unsets the RV status of an SV.
3031
e89caa19 3032 void SvROK_off (SV* sv)
cb1a09d0
AD
3033
3034=item SvROK_on
3035
3036Tells an SV that it is an RV.
3037
e89caa19 3038 void SvROK_on (SV* sv)
cb1a09d0
AD
3039
3040=item SvRV
3041
3042Dereferences an RV to return the SV.
3043
ef50df4b 3044 SV* SvRV (SV* sv)
cb1a09d0 3045
189b2af5
GS
3046=item SvSETMAGIC
3047
3048Invokes C<mg_set> on an SV if it has 'set' magic. This macro evaluates
3049its argument more than once.
3050
3051 void SvSETMAGIC( SV *sv )
3052
ef50df4b 3053=item sv_setiv
189b2af5 3054
ef50df4b
GS
3055Copies an integer into the given SV. Does not handle 'set' magic.
3056See C<sv_setiv_mg>.
189b2af5 3057
ef50df4b 3058 void sv_setiv (SV* sv, IV num)
189b2af5 3059
ef50df4b 3060=item sv_setiv_mg
189b2af5 3061
ef50df4b 3062Like C<sv_setiv>, but also handles 'set' magic.
189b2af5 3063
ef50df4b 3064 void sv_setiv_mg (SV* sv, IV num)
189b2af5 3065
ef50df4b 3066=item sv_setnv
189b2af5 3067
ef50df4b
GS
3068Copies a double into the given SV. Does not handle 'set' magic.
3069See C<sv_setnv_mg>.
189b2af5 3070
ef50df4b 3071 void sv_setnv (SV* sv, double num)
189b2af5 3072
ef50df4b 3073=item sv_setnv_mg
189b2af5 3074
ef50df4b 3075Like C<sv_setnv>, but also handles 'set' magic.
189b2af5 3076
ef50df4b 3077 void sv_setnv_mg (SV* sv, double num)
189b2af5 3078
ef50df4b 3079=item sv_setpv
189b2af5 3080
ef50df4b
GS
3081Copies a string into an SV. The string must be null-terminated.
3082Does not handle 'set' magic. See C<sv_setpv_mg>.
189b2af5 3083
ef50df4b 3084 void sv_setpv (SV* sv, char* ptr)
189b2af5 3085
ef50df4b 3086=item sv_setpv_mg
189b2af5 3087
ef50df4b 3088Like C<sv_setpv>, but also handles 'set' magic.
189b2af5 3089
ef50df4b 3090 void sv_setpv_mg (SV* sv, char* ptr)
189b2af5 3091
ef50df4b 3092=item sv_setpviv
cb1a09d0 3093
ef50df4b
GS
3094Copies an integer into the given SV, also updating its string value.
3095Does not handle 'set' magic. See C<sv_setpviv_mg>.
cb1a09d0 3096
ef50df4b 3097 void sv_setpviv (SV* sv, IV num)
cb1a09d0 3098
ef50df4b 3099=item sv_setpviv_mg
cb1a09d0 3100
ef50df4b 3101Like C<sv_setpviv>, but also handles 'set' magic.
cb1a09d0 3102
ef50df4b 3103 void sv_setpviv_mg (SV* sv, IV num)
cb1a09d0 3104
ef50df4b 3105=item sv_setpvn
cb1a09d0 3106
ef50df4b
GS
3107Copies a string into an SV. The C<len> parameter indicates the number of
3108bytes to be copied. Does not handle 'set' magic. See C<sv_setpvn_mg>.
cb1a09d0 3109
ef50df4b 3110 void sv_setpvn (SV* sv, char* ptr, STRLEN len)
cb1a09d0 3111
ef50df4b 3112=item sv_setpvn_mg
189b2af5 3113
ef50df4b 3114Like C<sv_setpvn>, but also handles 'set' magic.
189b2af5 3115
ef50df4b 3116 void sv_setpvn_mg (SV* sv, char* ptr, STRLEN len)
189b2af5 3117
ef50df4b 3118=item sv_setpvf
cb1a09d0 3119
ef50df4b
GS
3120Processes its arguments like C<sprintf> and sets an SV to the formatted
3121output. Does not handle 'set' magic. See C<sv_setpvf_mg>.
cb1a09d0 3122
ef50df4b 3123 void sv_setpvf (SV* sv, const char* pat, ...)
cb1a09d0 3124
ef50df4b 3125=item sv_setpvf_mg
46fc3d4c 3126
ef50df4b 3127Like C<sv_setpvf>, but also handles 'set' magic.
46fc3d4c 3128
ef50df4b 3129 void sv_setpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 3130
cb1a09d0
AD
3131=item sv_setref_iv
3132
5fb8527f
PP
3133Copies an integer into a new SV, optionally blessing the SV. The C<rv>
3134argument will be upgraded to an RV. That RV will be modified to point to
3135the new SV. The C<classname> argument indicates the package for the
3136blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3137will be returned and will have a reference count of 1.
cb1a09d0 3138
ef50df4b 3139 SV* sv_setref_iv (SV *rv, char *classname, IV iv)
cb1a09d0
AD
3140
3141=item sv_setref_nv
3142
5fb8527f
PP
3143Copies a double into a new SV, optionally blessing the SV. The C<rv>
3144argument will be upgraded to an RV. That RV will be modified to point to
3145the new SV. The C<classname> argument indicates the package for the
3146blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3147will be returned and will have a reference count of 1.
cb1a09d0 3148
ef50df4b 3149 SV* sv_setref_nv (SV *rv, char *classname, double nv)
cb1a09d0
AD
3150
3151=item sv_setref_pv
3152
5fb8527f
PP
3153Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
3154argument will be upgraded to an RV. That RV will be modified to point to
9cde0e7f 3155the new SV. If the C<pv> argument is NULL then C<PL_sv_undef> will be placed
5fb8527f
PP
3156into the SV. The C<classname> argument indicates the package for the
3157blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3158will be returned and will have a reference count of 1.
cb1a09d0 3159
ef50df4b 3160 SV* sv_setref_pv (SV *rv, char *classname, void* pv)
cb1a09d0
AD
3161
3162Do not use with integral Perl types such as HV, AV, SV, CV, because those
3163objects will become corrupted by the pointer copy process.
3164
3165Note that C<sv_setref_pvn> copies the string while this copies the pointer.
3166
3167=item sv_setref_pvn
3168
5fb8527f
PP
3169Copies a string into a new SV, optionally blessing the SV. The length of the
3170string must be specified with C<n>. The C<rv> argument will be upgraded to
3171an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
3172argument indicates the package for the blessing. Set C<classname> to
3173C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 3174a reference count of 1.
cb1a09d0 3175
ef50df4b 3176 SV* sv_setref_pvn (SV *rv, char *classname, char* pv, I32 n)
cb1a09d0
AD
3177
3178Note that C<sv_setref_pv> copies the pointer while this copies the string.
3179
189b2af5
GS
3180=item SvSetSV
3181
3182Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
3183more than once.
3184
3185 void SvSetSV (SV* dsv, SV* ssv)
3186
3187=item SvSetSV_nosteal
3188
3189Calls a non-destructive version of C<sv_setsv> if dsv is not the same as ssv.
3190May evaluate arguments more than once.
3191
3192 void SvSetSV_nosteal (SV* dsv, SV* ssv)
3193
cb1a09d0
AD
3194=item sv_setsv
3195
3196Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
189b2af5 3197The source SV may be destroyed if it is mortal. Does not handle 'set' magic.
ef50df4b
GS
3198See the macro forms C<SvSetSV>, C<SvSetSV_nosteal> and C<sv_setsv_mg>.
3199
3200 void sv_setsv (SV* dsv, SV* ssv)
3201
3202=item sv_setsv_mg
3203
3204Like C<sv_setsv>, but also handles 'set' magic.
cb1a09d0 3205
ef50df4b 3206 void sv_setsv_mg (SV* dsv, SV* ssv)
cb1a09d0 3207
189b2af5
GS
3208=item sv_setuv
3209
3210Copies an unsigned integer into the given SV. Does not handle 'set' magic.
ef50df4b 3211See C<sv_setuv_mg>.
189b2af5 3212
ef50df4b
GS
3213 void sv_setuv (SV* sv, UV num)
3214
3215=item sv_setuv_mg
3216
3217Like C<sv_setuv>, but also handles 'set' magic.
3218
3219 void sv_setuv_mg (SV* sv, UV num)
189b2af5 3220
cb1a09d0
AD
3221=item SvSTASH
3222
3223Returns the stash of the SV.
3224
e89caa19
GA
3225 HV* SvSTASH (SV* sv)
3226
3227=item SvTAINT
3228
3229Taints an SV if tainting is enabled
3230
3231 void SvTAINT (SV* sv)
3232
3233=item SvTAINTED
3234
3235Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.
3236
3237 int SvTAINTED (SV* sv)
3238
3239=item SvTAINTED_off
3240
3241Untaints an SV. Be I<very> careful with this routine, as it short-circuits
3242some of Perl's fundamental security features. XS module authors should
3243not use this function unless they fully understand all the implications
3244of unconditionally untainting the value. Untainting should be done in
3245the standard perl fashion, via a carefully crafted regexp, rather than
3246directly untainting variables.
3247
3248 void SvTAINTED_off (SV* sv)
3249
3250=item SvTAINTED_on
3251
3252Marks an SV as tainted.
3253
3254 void SvTAINTED_on (SV* sv)
cb1a09d0
AD
3255
3256=item SVt_IV
3257
3258Integer type flag for scalars. See C<svtype>.
3259
3260=item SVt_PV
3261
3262Pointer type flag for scalars. See C<svtype>.
3263
3264=item SVt_PVAV
3265
3266Type flag for arrays. See C<svtype>.
3267
3268=item SVt_PVCV
3269
3270Type flag for code refs. See C<svtype>.
3271
3272=item SVt_PVHV
3273
3274Type flag for hashes. See C<svtype>.
3275
3276=item SVt_PVMG
3277
3278Type flag for blessed scalars. See C<svtype>.
3279
3280=item SVt_NV
3281
3282Double type flag for scalars. See C<svtype>.
3283
3284=item SvTRUE
3285
3286Returns a boolean indicating whether Perl would evaluate the SV as true or
189b2af5 3287false, defined or undefined. Does not handle 'get' magic.
cb1a09d0 3288
e89caa19 3289 int SvTRUE (SV* sv)
cb1a09d0
AD
3290
3291=item SvTYPE
3292
3293Returns the type of the SV. See C<svtype>.
3294
3295 svtype SvTYPE (SV* sv)
3296
3297=item svtype
3298
3299An enum of flags for Perl types. These are found in the file B<sv.h> in the
3300C<svtype> enum. Test these flags with the C<SvTYPE> macro.
3301
9cde0e7f 3302=item PL_sv_undef
cb1a09d0 3303
9cde0e7f 3304This is the C<undef> SV. Always refer to this as C<&PL_sv_undef>.
cb1a09d0 3305
5fb8527f
PP
3306=item sv_unref
3307
07fa94a1
JO
3308Unsets the RV status of the SV, and decrements the reference count of
3309whatever was being referenced by the RV. This can almost be thought of
3310as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f 3311
ef50df4b 3312 void sv_unref (SV* sv)
189b2af5 3313
e89caa19
GA
3314=item SvUPGRADE
3315
3316Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
3317the upgrade if necessary. See C<svtype>.
3318
3319 bool SvUPGRADE (SV* sv, svtype mt)
3320
3321=item sv_upgrade
3322
3323Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
3324
cb1a09d0
AD
3325=item sv_usepvn
3326
3327Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
3328stored inside the SV but sv_usepvn allows the SV to use an outside string.
3329The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
3330string length, C<len>, must be supplied. This function will realloc the
3331memory pointed to by C<ptr>, so that pointer should not be freed or used by
189b2af5 3332the programmer after giving it to sv_usepvn. Does not handle 'set' magic.
ef50df4b
GS
3333See C<sv_usepvn_mg>.
3334
3335 void sv_usepvn (SV* sv, char* ptr, STRLEN len)
3336
3337=item sv_usepvn_mg
3338
3339Like C<sv_usepvn>, but also handles 'set' magic.
cb1a09d0 3340
ef50df4b 3341 void sv_usepvn_mg (SV* sv, char* ptr, STRLEN len)
cb1a09d0 3342
9abd00ed
GS
3343=item sv_vcatpvfn(sv, pat, patlen, args, svargs, svmax, used_locale)
3344
3345Processes its arguments like C<vsprintf> and appends the formatted output
3346to an SV. Uses an array of SVs if the C style variable argument list is
3347missing (NULL). Indicates if locale information has been used for formatting.
3348
3349 void sv_catpvfn _((SV* sv, const char* pat, STRLEN patlen,
3350 va_list *args, SV **svargs, I32 svmax,
3351 bool *used_locale));
3352
3353=item sv_vsetpvfn(sv, pat, patlen, args, svargs, svmax, used_locale)
3354
3355Works like C<vcatpvfn> but copies the text into the SV instead of
3356appending it.
3357
3358 void sv_setpvfn _((SV* sv, const char* pat, STRLEN patlen,
3359 va_list *args, SV **svargs, I32 svmax,
3360 bool *used_locale));
3361
e89caa19
GA
3362=item SvUV
3363
3364Returns the unsigned integer which is in the SV.
3365
3366 UV SvUV(SV* sv)
3367
3368=item SvUVX
3369
3370Returns the unsigned integer which is stored in the SV.
3371
3372 UV SvUVX(SV* sv)
3373
9cde0e7f 3374=item PL_sv_yes
cb1a09d0 3375
9cde0e7f 3376This is the C<true> SV. See C<PL_sv_no>. Always refer to this as C<&PL_sv_yes>.
cb1a09d0
AD
3377
3378=item THIS
3379
3380Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
3381This is always the proper type for the C++ object. See C<CLASS> and
5fb8527f 3382L<perlxs/"Using XS With C++">.
cb1a09d0
AD
3383
3384=item toLOWER
3385
3386Converts the specified character to lowercase.
3387
e89caa19 3388 int toLOWER (char c)
cb1a09d0
AD
3389
3390=item toUPPER
3391
3392Converts the specified character to uppercase.
3393
e89caa19 3394 int toUPPER (char c)
cb1a09d0
AD
3395
3396=item warn
3397
3398This is the XSUB-writer's interface to Perl's C<warn> function. Use this
3399function the same way you use the C C<printf> function. See C<croak()>.
3400
3401=item XPUSHi
3402
189b2af5
GS
3403Push an integer onto the stack, extending the stack if necessary. Handles
3404'set' magic. See C<PUSHi>.
cb1a09d0
AD
3405
3406 XPUSHi(int d)
3407
3408=item XPUSHn
3409
189b2af5
GS
3410Push a double onto the stack, extending the stack if necessary. Handles 'set'
3411magic. See C<PUSHn>.
cb1a09d0
AD
3412
3413 XPUSHn(double d)
3414
3415=item XPUSHp
3416
3417Push a string onto the stack, extending the stack if necessary. The C<len>
189b2af5 3418indicates the length of the string. Handles 'set' magic. See C<PUSHp>.
cb1a09d0
AD
3419
3420 XPUSHp(char *c, int len)
3421
3422=item XPUSHs
3423
189b2af5
GS
3424Push an SV onto the stack, extending the stack if necessary. Does not
3425handle 'set' magic. See C<PUSHs>.
cb1a09d0
AD
3426
3427 XPUSHs(sv)
3428
e89caa19
GA
3429=item XPUSHu
3430
3431Push an unsigned integer onto the stack, extending the stack if
3432necessary. See C<PUSHu>.
3433
5fb8527f
PP
3434=item XS
3435
3436Macro to declare an XSUB and its C parameter list. This is handled by
3437C<xsubpp>.
3438
cb1a09d0
AD
3439=item XSRETURN
3440
3441Return from XSUB, indicating number of items on the stack. This is usually
3442handled by C<xsubpp>.
3443
ef50df4b 3444 XSRETURN(int x)
cb1a09d0
AD
3445
3446=item XSRETURN_EMPTY
3447
5fb8527f 3448Return an empty list from an XSUB immediately.
cb1a09d0
AD
3449
3450 XSRETURN_EMPTY;
3451
5fb8527f
PP
3452=item XSRETURN_IV
3453
3454Return an integer from an XSUB immediately. Uses C<XST_mIV>.
3455
ef50df4b 3456 XSRETURN_IV(IV v)
5fb8527f 3457
cb1a09d0
AD
3458=item XSRETURN_NO
3459
9cde0e7f 3460Return C<&PL_sv_no> from an XSUB immediately. Uses C<XST_mNO>.
cb1a09d0
AD
3461
3462 XSRETURN_NO;
3463
5fb8527f
PP
3464=item XSRETURN_NV
3465
3466Return an double from an XSUB immediately. Uses C<XST_mNV>.
3467
ef50df4b 3468 XSRETURN_NV(NV v)
5fb8527f
PP
3469
3470=item XSRETURN_PV
3471
3472Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
3473
ef50df4b 3474 XSRETURN_PV(char *v)
5fb8527f 3475
cb1a09d0
AD
3476=item XSRETURN_UNDEF
3477
9cde0e7f 3478Return C<&PL_sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
cb1a09d0
AD
3479
3480 XSRETURN_UNDEF;
3481
3482=item XSRETURN_YES
3483
9cde0e7f 3484Return C<&PL_sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
cb1a09d0
AD
3485
3486 XSRETURN_YES;
3487
5fb8527f
PP
3488=item XST_mIV
3489
3490Place an integer into the specified position C<i> on the stack. The value is
3491stored in a new mortal SV.
3492
ef50df4b 3493 XST_mIV( int i, IV v )
5fb8527f
PP
3494
3495=item XST_mNV
3496
3497Place a double into the specified position C<i> on the stack. The value is
3498stored in a new mortal SV.
3499
ef50df4b 3500 XST_mNV( int i, NV v )
5fb8527f
PP
3501
3502=item XST_mNO
3503
9cde0e7f 3504Place C<&PL_sv_no> into the specified position C<i> on the stack.
5fb8527f 3505
ef50df4b 3506 XST_mNO( int i )
5fb8527f
PP
3507
3508=item XST_mPV
3509
3510Place a copy of a string into the specified position C<i> on the stack. The
3511value is stored in a new mortal SV.
3512
ef50df4b 3513 XST_mPV( int i, char *v )
5fb8527f
PP
3514
3515=item XST_mUNDEF
3516
9cde0e7f 3517Place C<&PL_sv_undef> into the specified position C<i> on the stack.
5fb8527f 3518
ef50df4b 3519 XST_mUNDEF( int i )
5fb8527f
PP
3520
3521=item XST_mYES
3522
9cde0e7f 3523Place C<&PL_sv_yes> into the specified position C<i> on the stack.
5fb8527f 3524
ef50df4b 3525 XST_mYES( int i )
5fb8527f
PP
3526
3527=item XS_VERSION
3528
3529The version identifier for an XS module. This is usually handled
3530automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
3531
3532=item XS_VERSION_BOOTCHECK
3533
3534Macro to verify that a PM module's $VERSION variable matches the XS module's
3535C<XS_VERSION> variable. This is usually handled automatically by
3536C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
3537
cb1a09d0
AD
3538=item Zero
3539
3540The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
3541destination, C<n> is the number of items, and C<t> is the type.
3542
e89caa19 3543 void Zero( d, n, t )
cb1a09d0
AD
3544
3545=back
3546
9cecd9f2 3547=head1 AUTHORS
cb1a09d0 3548
9cecd9f2
GA
3549Until May 1997, this document was maintained by Jeff Okamoto
3550<okamoto@corp.hp.com>. It is now maintained as part of Perl itself.
cb1a09d0
AD
3551
3552With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
3553Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
189b2af5
GS
3554Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
3555Stephen McCamant, and Gurusamy Sarathy.
cb1a09d0 3556
9cecd9f2 3557API Listing originally by Dean Roehrich <roehrich@cray.com>.