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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*, ...);
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54 void sv_setsv(SV*, SV*);
55
56Notice that you can choose to specify the length of the string to be
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57assigned by using C<sv_setpvn>, C<newSVpvn>, or C<newSVpv>, or you may
58allow Perl to calculate the length by using C<sv_setpv> or by specifying
590 as the second argument to C<newSVpv>. Be warned, though, that Perl will
60determine the string's length by using C<strlen>, which depends on the
61string terminating with a NUL character. The arguments of C<sv_setpvf>
62are processed like C<sprintf>, and the formatted output becomes the value.
63The C<sv_set*()> functions are not generic enough to operate on values
64that have "magic". See L<Magic Virtual Tables> later in this document.
a0d0e21e 65
54310121 66All SVs that will contain strings should, but need not, be terminated
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67with a NUL character. If it is not NUL-terminated there is a risk of
68core dumps and corruptions from code which passes the string to C
69functions or system calls which expect a NUL-terminated string.
70Perl's own functions typically add a trailing NUL for this reason.
71Nevertheless, you should be very careful when you pass a string stored
72in an SV to a C function or system call.
73
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74To access the actual value that an SV points to, you can use the macros:
75
76 SvIV(SV*)
77 SvNV(SV*)
78 SvPV(SV*, STRLEN len)
79
80which will automatically coerce the actual scalar type into an IV, double,
81or string.
82
83In the C<SvPV> macro, the length of the string returned is placed into the
84variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
85care what the length of the data is, use the global variable C<na>. Remember,
86however, that Perl allows arbitrary strings of data that may both contain
54310121 87NULs and might not be terminated by a NUL.
a0d0e21e 88
07fa94a1 89If you want to know if the scalar value is TRUE, you can use:
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90
91 SvTRUE(SV*)
92
93Although Perl will automatically grow strings for you, if you need to force
94Perl to allocate more memory for your SV, you can use the macro
95
96 SvGROW(SV*, STRLEN newlen)
97
98which will determine if more memory needs to be allocated. If so, it will
99call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
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100decrease, the allocated memory of an SV and that it does not automatically
101add a byte for the a trailing NUL (perl's own string functions typically do
8ebc5c01 102C<SvGROW(sv, len + 1)>).
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103
104If you have an SV and want to know what kind of data Perl thinks is stored
105in it, you can use the following macros to check the type of SV you have.
106
107 SvIOK(SV*)
108 SvNOK(SV*)
109 SvPOK(SV*)
110
111You can get and set the current length of the string stored in an SV with
112the following macros:
113
114 SvCUR(SV*)
115 SvCUR_set(SV*, I32 val)
116
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117You can also get a pointer to the end of the string stored in the SV
118with the macro:
119
120 SvEND(SV*)
121
122But note that these last three macros are valid only if C<SvPOK()> is true.
a0d0e21e 123
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124If you want to append something to the end of string stored in an C<SV*>,
125you can use the following functions:
126
127 void sv_catpv(SV*, char*);
128 void sv_catpvn(SV*, char*, int);
46fc3d4c 129 void sv_catpvf(SV*, const char*, ...);
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130 void sv_catsv(SV*, SV*);
131
132The first function calculates the length of the string to be appended by
133using C<strlen>. In the second, you specify the length of the string
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134yourself. The third function processes its arguments like C<sprintf> and
135appends the formatted output. The fourth function extends the string
136stored in the first SV with the string stored in the second SV. It also
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137forces the second SV to be interpreted as a string. The C<sv_cat*()>
138functions are not generic enough to operate on values that have "magic".
139See L<Magic Virtual Tables> later in this document.
d1b91892 140
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141If you know the name of a scalar variable, you can get a pointer to its SV
142by using the following:
143
5f05dabc 144 SV* perl_get_sv("package::varname", FALSE);
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145
146This returns NULL if the variable does not exist.
147
d1b91892 148If you want to know if this variable (or any other SV) is actually C<defined>,
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149you can call:
150
151 SvOK(SV*)
152
153The scalar C<undef> value is stored in an SV instance called C<sv_undef>. Its
154address can be used whenever an C<SV*> is needed.
155
156There are also the two values C<sv_yes> and C<sv_no>, which contain Boolean
157TRUE and FALSE values, respectively. Like C<sv_undef>, their addresses can
158be used whenever an C<SV*> is needed.
159
160Do not be fooled into thinking that C<(SV *) 0> is the same as C<&sv_undef>.
161Take this code:
162
163 SV* sv = (SV*) 0;
164 if (I-am-to-return-a-real-value) {
165 sv = sv_2mortal(newSViv(42));
166 }
167 sv_setsv(ST(0), sv);
168
169This code tries to return a new SV (which contains the value 42) if it should
04343c6d 170return a real value, or undef otherwise. Instead it has returned a NULL
a0d0e21e 171pointer which, somewhere down the line, will cause a segmentation violation,
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172bus error, or just weird results. Change the zero to C<&sv_undef> in the first
173line and all will be well.
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174
175To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
3fe9a6f1 176call is not necessary (see L<Reference Counts and Mortality>).
a0d0e21e 177
d1b91892 178=head2 What's Really Stored in an SV?
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179
180Recall that the usual method of determining the type of scalar you have is
5f05dabc 181to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
d1b91892 182usually these macros will always return TRUE and calling the C<Sv*V>
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183macros will do the appropriate conversion of string to integer/double or
184integer/double to string.
185
186If you I<really> need to know if you have an integer, double, or string
187pointer in an SV, you can use the following three macros instead:
188
189 SvIOKp(SV*)
190 SvNOKp(SV*)
191 SvPOKp(SV*)
192
193These will tell you if you truly have an integer, double, or string pointer
d1b91892 194stored in your SV. The "p" stands for private.
a0d0e21e 195
07fa94a1 196In general, though, it's best to use the C<Sv*V> macros.
a0d0e21e 197
54310121 198=head2 Working with AVs
a0d0e21e 199
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200There are two ways to create and load an AV. The first method creates an
201empty AV:
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202
203 AV* newAV();
204
54310121 205The second method both creates the AV and initially populates it with SVs:
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206
207 AV* av_make(I32 num, SV **ptr);
208
5f05dabc 209The second argument points to an array containing C<num> C<SV*>'s. Once the
54310121 210AV has been created, the SVs can be destroyed, if so desired.
a0d0e21e 211
54310121 212Once the AV has been created, the following operations are possible on AVs:
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213
214 void av_push(AV*, SV*);
215 SV* av_pop(AV*);
216 SV* av_shift(AV*);
217 void av_unshift(AV*, I32 num);
218
219These should be familiar operations, with the exception of C<av_unshift>.
220This routine adds C<num> elements at the front of the array with the C<undef>
221value. You must then use C<av_store> (described below) to assign values
222to these new elements.
223
224Here are some other functions:
225
5f05dabc 226 I32 av_len(AV*);
a0d0e21e 227 SV** av_fetch(AV*, I32 key, I32 lval);
a0d0e21e 228 SV** av_store(AV*, I32 key, SV* val);
a0d0e21e 229
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230The C<av_len> function returns the highest index value in array (just
231like $#array in Perl). If the array is empty, -1 is returned. The
232C<av_fetch> function returns the value at index C<key>, but if C<lval>
233is non-zero, then C<av_fetch> will store an undef value at that index.
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234The C<av_store> function stores the value C<val> at index C<key>, and does
235not increment the reference count of C<val>. Thus the caller is responsible
236for taking care of that, and if C<av_store> returns NULL, the caller will
237have to decrement the reference count to avoid a memory leak. Note that
238C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s as their
239return value.
d1b91892 240
a0d0e21e 241 void av_clear(AV*);
a0d0e21e 242 void av_undef(AV*);
cb1a09d0 243 void av_extend(AV*, I32 key);
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244
245The C<av_clear> function deletes all the elements in the AV* array, but
246does not actually delete the array itself. The C<av_undef> function will
247delete all the elements in the array plus the array itself. The
248C<av_extend> function extends the array so that it contains C<key>
249elements. If C<key> is less than the current length of the array, then
250nothing is done.
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251
252If you know the name of an array variable, you can get a pointer to its AV
253by using the following:
254
5f05dabc 255 AV* perl_get_av("package::varname", FALSE);
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256
257This returns NULL if the variable does not exist.
258
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259See L<Understanding the Magic of Tied Hashes and Arrays> for more
260information on how to use the array access functions on tied arrays.
261
54310121 262=head2 Working with HVs
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263
264To create an HV, you use the following routine:
265
266 HV* newHV();
267
54310121 268Once the HV has been created, the following operations are possible on HVs:
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269
270 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
271 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
272
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273The C<klen> parameter is the length of the key being passed in (Note that
274you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
275length of the key). The C<val> argument contains the SV pointer to the
54310121 276scalar being stored, and C<hash> is the precomputed hash value (zero if
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277you want C<hv_store> to calculate it for you). The C<lval> parameter
278indicates whether this fetch is actually a part of a store operation, in
279which case a new undefined value will be added to the HV with the supplied
280key and C<hv_fetch> will return as if the value had already existed.
a0d0e21e 281
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282Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
283C<SV*>. To access the scalar value, you must first dereference the return
284value. However, you should check to make sure that the return value is
285not NULL before dereferencing it.
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286
287These two functions check if a hash table entry exists, and deletes it.
288
289 bool hv_exists(HV*, char* key, U32 klen);
d1b91892 290 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
a0d0e21e 291
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292If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
293create and return a mortal copy of the deleted value.
294
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295And more miscellaneous functions:
296
297 void hv_clear(HV*);
a0d0e21e 298 void hv_undef(HV*);
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299
300Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
301table but does not actually delete the hash table. The C<hv_undef> deletes
302both the entries and the hash table itself.
a0d0e21e 303
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304Perl keeps the actual data in linked list of structures with a typedef of HE.
305These contain the actual key and value pointers (plus extra administrative
306overhead). The key is a string pointer; the value is an C<SV*>. However,
307once you have an C<HE*>, to get the actual key and value, use the routines
308specified below.
309
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310 I32 hv_iterinit(HV*);
311 /* Prepares starting point to traverse hash table */
312 HE* hv_iternext(HV*);
313 /* Get the next entry, and return a pointer to a
314 structure that has both the key and value */
315 char* hv_iterkey(HE* entry, I32* retlen);
316 /* Get the key from an HE structure and also return
317 the length of the key string */
cb1a09d0 318 SV* hv_iterval(HV*, HE* entry);
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319 /* Return a SV pointer to the value of the HE
320 structure */
cb1a09d0 321 SV* hv_iternextsv(HV*, char** key, I32* retlen);
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322 /* This convenience routine combines hv_iternext,
323 hv_iterkey, and hv_iterval. The key and retlen
324 arguments are return values for the key and its
325 length. The value is returned in the SV* argument */
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326
327If you know the name of a hash variable, you can get a pointer to its HV
328by using the following:
329
5f05dabc 330 HV* perl_get_hv("package::varname", FALSE);
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331
332This returns NULL if the variable does not exist.
333
8ebc5c01 334The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
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335
336 i = klen;
337 hash = 0;
338 s = key;
339 while (i--)
340 hash = hash * 33 + *s++;
341
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342See L<Understanding the Magic of Tied Hashes and Arrays> for more
343information on how to use the hash access functions on tied hashes.
344
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345=head2 Hash API Extensions
346
347Beginning with version 5.004, the following functions are also supported:
348
349 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
350 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
351
352 bool hv_exists_ent (HV* tb, SV* key, U32 hash);
353 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
354
355 SV* hv_iterkeysv (HE* entry);
356
357Note that these functions take C<SV*> keys, which simplifies writing
358of extension code that deals with hash structures. These functions
359also allow passing of C<SV*> keys to C<tie> functions without forcing
360you to stringify the keys (unlike the previous set of functions).
361
362They also return and accept whole hash entries (C<HE*>), making their
363use more efficient (since the hash number for a particular string
364doesn't have to be recomputed every time). See L<API LISTING> later in
365this document for detailed descriptions.
366
367The following macros must always be used to access the contents of hash
368entries. Note that the arguments to these macros must be simple
369variables, since they may get evaluated more than once. See
370L<API LISTING> later in this document for detailed descriptions of these
371macros.
372
373 HePV(HE* he, STRLEN len)
374 HeVAL(HE* he)
375 HeHASH(HE* he)
376 HeSVKEY(HE* he)
377 HeSVKEY_force(HE* he)
378 HeSVKEY_set(HE* he, SV* sv)
379
380These two lower level macros are defined, but must only be used when
381dealing with keys that are not C<SV*>s:
382
383 HeKEY(HE* he)
384 HeKLEN(HE* he)
385
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386Note that both C<hv_store> and C<hv_store_ent> do not increment the
387reference count of the stored C<val>, which is the caller's responsibility.
388If these functions return a NULL value, the caller will usually have to
389decrement the reference count of C<val> to avoid a memory leak.
1e422769 390
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391=head2 References
392
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393References are a special type of scalar that point to other data types
394(including references).
a0d0e21e 395
07fa94a1 396To create a reference, use either of the following functions:
a0d0e21e 397
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398 SV* newRV_inc((SV*) thing);
399 SV* newRV_noinc((SV*) thing);
a0d0e21e 400
5f05dabc 401The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
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402functions are identical except that C<newRV_inc> increments the reference
403count of the C<thing>, while C<newRV_noinc> does not. For historical
404reasons, C<newRV> is a synonym for C<newRV_inc>.
405
406Once you have a reference, you can use the following macro to dereference
407the reference:
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408
409 SvRV(SV*)
410
411then call the appropriate routines, casting the returned C<SV*> to either an
d1b91892 412C<AV*> or C<HV*>, if required.
a0d0e21e 413
d1b91892 414To determine if an SV is a reference, you can use the following macro:
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415
416 SvROK(SV*)
417
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418To discover what type of value the reference refers to, use the following
419macro and then check the return value.
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420
421 SvTYPE(SvRV(SV*))
422
423The most useful types that will be returned are:
424
425 SVt_IV Scalar
426 SVt_NV Scalar
427 SVt_PV Scalar
5f05dabc 428 SVt_RV Scalar
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429 SVt_PVAV Array
430 SVt_PVHV Hash
431 SVt_PVCV Code
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432 SVt_PVGV Glob (possible a file handle)
433 SVt_PVMG Blessed or Magical Scalar
434
435 See the sv.h header file for more details.
d1b91892 436
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437=head2 Blessed References and Class Objects
438
439References are also used to support object-oriented programming. In the
440OO lexicon, an object is simply a reference that has been blessed into a
441package (or class). Once blessed, the programmer may now use the reference
442to access the various methods in the class.
443
444A reference can be blessed into a package with the following function:
445
446 SV* sv_bless(SV* sv, HV* stash);
447
448The C<sv> argument must be a reference. The C<stash> argument specifies
3fe9a6f1 449which class the reference will belong to. See
2ae324a7 450L<Stashes and Globs> for information on converting class names into stashes.
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451
452/* Still under construction */
453
454Upgrades rv to reference if not already one. Creates new SV for rv to
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455point to. If C<classname> is non-null, the SV is blessed into the specified
456class. SV is returned.
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457
458 SV* newSVrv(SV* rv, char* classname);
459
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460Copies integer or double into an SV whose reference is C<rv>. SV is blessed
461if C<classname> is non-null.
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462
463 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
464 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
465
5f05dabc 466Copies the pointer value (I<the address, not the string!>) into an SV whose
8ebc5c01 467reference is rv. SV is blessed if C<classname> is non-null.
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468
469 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
470
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471Copies string into an SV whose reference is C<rv>. Set length to 0 to let
472Perl calculate the string length. SV is blessed if C<classname> is non-null.
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473
474 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
475
476 int sv_isa(SV* sv, char* name);
477 int sv_isobject(SV* sv);
478
5f05dabc 479=head2 Creating New Variables
cb1a09d0 480
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481To create a new Perl variable with an undef value which can be accessed from
482your Perl script, use the following routines, depending on the variable type.
cb1a09d0 483
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484 SV* perl_get_sv("package::varname", TRUE);
485 AV* perl_get_av("package::varname", TRUE);
486 HV* perl_get_hv("package::varname", TRUE);
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487
488Notice the use of TRUE as the second parameter. The new variable can now
489be set, using the routines appropriate to the data type.
490
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491There are additional macros whose values may be bitwise OR'ed with the
492C<TRUE> argument to enable certain extra features. Those bits are:
cb1a09d0 493
5f05dabc 494 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
54310121 495 "Name <varname> used only once: possible typo" warning.
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496 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
497 the variable did not exist before the function was called.
cb1a09d0 498
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499If you do not specify a package name, the variable is created in the current
500package.
cb1a09d0 501
5f05dabc 502=head2 Reference Counts and Mortality
a0d0e21e 503
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504Perl uses an reference count-driven garbage collection mechanism. SVs,
505AVs, or HVs (xV for short in the following) start their life with a
55497cff 506reference count of 1. If the reference count of an xV ever drops to 0,
07fa94a1 507then it will be destroyed and its memory made available for reuse.
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508
509This normally doesn't happen at the Perl level unless a variable is
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510undef'ed or the last variable holding a reference to it is changed or
511overwritten. At the internal level, however, reference counts can be
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512manipulated with the following macros:
513
514 int SvREFCNT(SV* sv);
5f05dabc 515 SV* SvREFCNT_inc(SV* sv);
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516 void SvREFCNT_dec(SV* sv);
517
518However, there is one other function which manipulates the reference
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519count of its argument. The C<newRV_inc> function, you will recall,
520creates a reference to the specified argument. As a side effect,
521it increments the argument's reference count. If this is not what
522you want, use C<newRV_noinc> instead.
523
524For example, imagine you want to return a reference from an XSUB function.
525Inside the XSUB routine, you create an SV which initially has a reference
526count of one. Then you call C<newRV_inc>, passing it the just-created SV.
5f05dabc
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527This returns the reference as a new SV, but the reference count of the
528SV you passed to C<newRV_inc> has been incremented to two. Now you
07fa94a1
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529return the reference from the XSUB routine and forget about the SV.
530But Perl hasn't! Whenever the returned reference is destroyed, the
531reference count of the original SV is decreased to one and nothing happens.
532The SV will hang around without any way to access it until Perl itself
533terminates. This is a memory leak.
5f05dabc
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534
535The correct procedure, then, is to use C<newRV_noinc> instead of
faed5253
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536C<newRV_inc>. Then, if and when the last reference is destroyed,
537the reference count of the SV will go to zero and it will be destroyed,
07fa94a1 538stopping any memory leak.
55497cff 539
5f05dabc 540There are some convenience functions available that can help with the
54310121 541destruction of xVs. These functions introduce the concept of "mortality".
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542An xV that is mortal has had its reference count marked to be decremented,
543but not actually decremented, until "a short time later". Generally the
544term "short time later" means a single Perl statement, such as a call to
54310121 545an XSUB function. The actual determinant for when mortal xVs have their
07fa94a1
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546reference count decremented depends on two macros, SAVETMPS and FREETMPS.
547See L<perlcall> and L<perlxs> for more details on these macros.
55497cff
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548
549"Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
550However, if you mortalize a variable twice, the reference count will
551later be decremented twice.
552
553You should be careful about creating mortal variables. Strange things
554can happen if you make the same value mortal within multiple contexts,
5f05dabc 555or if you make a variable mortal multiple times.
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556
557To create a mortal variable, use the functions:
558
559 SV* sv_newmortal()
560 SV* sv_2mortal(SV*)
561 SV* sv_mortalcopy(SV*)
562
5f05dabc
PP
563The first call creates a mortal SV, the second converts an existing
564SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
565third creates a mortal copy of an existing SV.
a0d0e21e 566
54310121 567The mortal routines are not just for SVs -- AVs and HVs can be
faed5253 568made mortal by passing their address (type-casted to C<SV*>) to the
07fa94a1 569C<sv_2mortal> or C<sv_mortalcopy> routines.
a0d0e21e 570
5f05dabc 571=head2 Stashes and Globs
a0d0e21e 572
aa689395
PP
573A "stash" is a hash that contains all of the different objects that
574are contained within a package. Each key of the stash is a symbol
575name (shared by all the different types of objects that have the same
576name), and each value in the hash table is a GV (Glob Value). This GV
577in turn contains references to the various objects of that name,
578including (but not limited to) the following:
cb1a09d0 579
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580 Scalar Value
581 Array Value
582 Hash Value
583 File Handle
584 Directory Handle
585 Format
586 Subroutine
587
5f05dabc
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588There is a single stash called "defstash" that holds the items that exist
589in the "main" package. To get at the items in other packages, append the
590string "::" to the package name. The items in the "Foo" package are in
591the stash "Foo::" in defstash. The items in the "Bar::Baz" package are
592in the stash "Baz::" in "Bar::"'s stash.
a0d0e21e 593
d1b91892 594To get the stash pointer for a particular package, use the function:
a0d0e21e
LW
595
596 HV* gv_stashpv(char* name, I32 create)
597 HV* gv_stashsv(SV*, I32 create)
598
599The first function takes a literal string, the second uses the string stored
d1b91892 600in the SV. Remember that a stash is just a hash table, so you get back an
cb1a09d0 601C<HV*>. The C<create> flag will create a new package if it is set.
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602
603The name that C<gv_stash*v> wants is the name of the package whose symbol table
604you want. The default package is called C<main>. If you have multiply nested
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605packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
606language itself.
a0d0e21e
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607
608Alternately, if you have an SV that is a blessed reference, you can find
609out the stash pointer by using:
610
611 HV* SvSTASH(SvRV(SV*));
612
613then use the following to get the package name itself:
614
615 char* HvNAME(HV* stash);
616
5f05dabc
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617If you need to bless or re-bless an object you can use the following
618function:
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619
620 SV* sv_bless(SV*, HV* stash)
621
622where the first argument, an C<SV*>, must be a reference, and the second
623argument is a stash. The returned C<SV*> can now be used in the same way
624as any other SV.
625
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626For more information on references and blessings, consult L<perlref>.
627
54310121 628=head2 Double-Typed SVs
0a753a76
PP
629
630Scalar variables normally contain only one type of value, an integer,
631double, pointer, or reference. Perl will automatically convert the
632actual scalar data from the stored type into the requested type.
633
634Some scalar variables contain more than one type of scalar data. For
635example, the variable C<$!> contains either the numeric value of C<errno>
636or its string equivalent from either C<strerror> or C<sys_errlist[]>.
637
638To force multiple data values into an SV, you must do two things: use the
639C<sv_set*v> routines to add the additional scalar type, then set a flag
640so that Perl will believe it contains more than one type of data. The
641four macros to set the flags are:
642
643 SvIOK_on
644 SvNOK_on
645 SvPOK_on
646 SvROK_on
647
648The particular macro you must use depends on which C<sv_set*v> routine
649you called first. This is because every C<sv_set*v> routine turns on
650only the bit for the particular type of data being set, and turns off
651all the rest.
652
653For example, to create a new Perl variable called "dberror" that contains
654both the numeric and descriptive string error values, you could use the
655following code:
656
657 extern int dberror;
658 extern char *dberror_list;
659
660 SV* sv = perl_get_sv("dberror", TRUE);
661 sv_setiv(sv, (IV) dberror);
662 sv_setpv(sv, dberror_list[dberror]);
663 SvIOK_on(sv);
664
665If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
666macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
667
668=head2 Magic Variables
a0d0e21e 669
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670[This section still under construction. Ignore everything here. Post no
671bills. Everything not permitted is forbidden.]
672
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673Any SV may be magical, that is, it has special features that a normal
674SV does not have. These features are stored in the SV structure in a
5f05dabc 675linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
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676
677 struct magic {
678 MAGIC* mg_moremagic;
679 MGVTBL* mg_virtual;
680 U16 mg_private;
681 char mg_type;
682 U8 mg_flags;
683 SV* mg_obj;
684 char* mg_ptr;
685 I32 mg_len;
686 };
687
688Note this is current as of patchlevel 0, and could change at any time.
689
690=head2 Assigning Magic
691
692Perl adds magic to an SV using the sv_magic function:
693
694 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
695
696The C<sv> argument is a pointer to the SV that is to acquire a new magical
697feature.
698
699If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
700set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
701it to the beginning of the linked list of magical features. Any prior
702entry of the same type of magic is deleted. Note that this can be
5fb8527f 703overridden, and multiple instances of the same type of magic can be
d1b91892
AD
704associated with an SV.
705
54310121
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706The C<name> and C<namlen> arguments are used to associate a string with
707the magic, typically the name of a variable. C<namlen> is stored in the
708C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
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709copy of the name is stored in C<mg_ptr> field.
710
711The sv_magic function uses C<how> to determine which, if any, predefined
712"Magic Virtual Table" should be assigned to the C<mg_virtual> field.
cb1a09d0
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713See the "Magic Virtual Table" section below. The C<how> argument is also
714stored in the C<mg_type> field.
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715
716The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
717structure. If it is not the same as the C<sv> argument, the reference
718count of the C<obj> object is incremented. If it is the same, or if
04343c6d 719the C<how> argument is "#", or if it is a NULL pointer, then C<obj> is
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720merely stored, without the reference count being incremented.
721
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722There is also a function to add magic to an C<HV>:
723
724 void hv_magic(HV *hv, GV *gv, int how);
725
726This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
727
728To remove the magic from an SV, call the function sv_unmagic:
729
730 void sv_unmagic(SV *sv, int type);
731
732The C<type> argument should be equal to the C<how> value when the C<SV>
733was initially made magical.
734
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735=head2 Magic Virtual Tables
736
737The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
738C<MGVTBL>, which is a structure of function pointers and stands for
739"Magic Virtual Table" to handle the various operations that might be
740applied to that variable.
741
742The C<MGVTBL> has five pointers to the following routine types:
743
744 int (*svt_get)(SV* sv, MAGIC* mg);
745 int (*svt_set)(SV* sv, MAGIC* mg);
746 U32 (*svt_len)(SV* sv, MAGIC* mg);
747 int (*svt_clear)(SV* sv, MAGIC* mg);
748 int (*svt_free)(SV* sv, MAGIC* mg);
749
750This MGVTBL structure is set at compile-time in C<perl.h> and there are
751currently 19 types (or 21 with overloading turned on). These different
752structures contain pointers to various routines that perform additional
753actions depending on which function is being called.
754
755 Function pointer Action taken
756 ---------------- ------------
757 svt_get Do something after the value of the SV is retrieved.
758 svt_set Do something after the SV is assigned a value.
759 svt_len Report on the SV's length.
760 svt_clear Clear something the SV represents.
761 svt_free Free any extra storage associated with the SV.
762
763For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
764to an C<mg_type> of '\0') contains:
765
766 { magic_get, magic_set, magic_len, 0, 0 }
767
768Thus, when an SV is determined to be magical and of type '\0', if a get
769operation is being performed, the routine C<magic_get> is called. All
770the various routines for the various magical types begin with C<magic_>.
771
772The current kinds of Magic Virtual Tables are:
773
bdbeb323 774 mg_type MGVTBL Type of magic
5f05dabc 775 ------- ------ ----------------------------
bdbeb323
SM
776 \0 vtbl_sv Special scalar variable
777 A vtbl_amagic %OVERLOAD hash
778 a vtbl_amagicelem %OVERLOAD hash element
779 c (none) Holds overload table (AMT) on stash
780 B vtbl_bm Boyer-Moore (fast string search)
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AD
781 E vtbl_env %ENV hash
782 e vtbl_envelem %ENV hash element
bdbeb323
SM
783 f vtbl_fm Formline ('compiled' format)
784 g vtbl_mglob m//g target / study()ed string
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AD
785 I vtbl_isa @ISA array
786 i vtbl_isaelem @ISA array element
bdbeb323
SM
787 k vtbl_nkeys scalar(keys()) lvalue
788 L (none) Debugger %_<filename
789 l vtbl_dbline Debugger %_<filename element
44a8e56a 790 o vtbl_collxfrm Locale transformation
bdbeb323
SM
791 P vtbl_pack Tied array or hash
792 p vtbl_packelem Tied array or hash element
793 q vtbl_packelem Tied scalar or handle
794 S vtbl_sig %SIG hash
795 s vtbl_sigelem %SIG hash element
d1b91892 796 t vtbl_taint Taintedness
bdbeb323
SM
797 U vtbl_uvar Available for use by extensions
798 v vtbl_vec vec() lvalue
799 x vtbl_substr substr() lvalue
800 y vtbl_defelem Shadow "foreach" iterator variable /
801 smart parameter vivification
802 * vtbl_glob GV (typeglob)
803 # vtbl_arylen Array length ($#ary)
804 . vtbl_pos pos() lvalue
805 ~ (none) Available for use by extensions
d1b91892 806
68dc0745
PP
807When an uppercase and lowercase letter both exist in the table, then the
808uppercase letter is used to represent some kind of composite type (a list
809or a hash), and the lowercase letter is used to represent an element of
d1b91892
AD
810that composite type.
811
bdbeb323
SM
812The '~' and 'U' magic types are defined specifically for use by
813extensions and will not be used by perl itself. Extensions can use
814'~' magic to 'attach' private information to variables (typically
815objects). This is especially useful because there is no way for
816normal perl code to corrupt this private information (unlike using
817extra elements of a hash object).
818
819Similarly, 'U' magic can be used much like tie() to call a C function
820any time a scalar's value is used or changed. The C<MAGIC>'s
821C<mg_ptr> field points to a C<ufuncs> structure:
822
823 struct ufuncs {
824 I32 (*uf_val)(IV, SV*);
825 I32 (*uf_set)(IV, SV*);
826 IV uf_index;
827 };
828
829When the SV is read from or written to, the C<uf_val> or C<uf_set>
830function will be called with C<uf_index> as the first arg and a
831pointer to the SV as the second.
5f05dabc 832
bdbeb323
SM
833Note that because multiple extensions may be using '~' or 'U' magic,
834it is important for extensions to take extra care to avoid conflict.
835Typically only using the magic on objects blessed into the same class
836as the extension is sufficient. For '~' magic, it may also be
837appropriate to add an I32 'signature' at the top of the private data
838area and check that.
5f05dabc 839
ef50df4b
GS
840Also note that the C<sv_set*()> and C<sv_cat*()> functions described
841earlier do B<not> invoke 'set' magic on their targets. This must
842be done by the user either by calling the C<SvSETMAGIC()> macro after
843calling these functions, or by using one of the C<sv_set*_mg()> or
844C<sv_cat*_mg()> functions. Similarly, generic C code must call the
845C<SvGETMAGIC()> macro to invoke any 'get' magic if they use an SV
846obtained from external sources in functions that don't handle magic.
847L<API LISTING> later in this document identifies such functions.
189b2af5
GS
848For example, calls to the C<sv_cat*()> functions typically need to be
849followed by C<SvSETMAGIC()>, but they don't need a prior C<SvGETMAGIC()>
850since their implementation handles 'get' magic.
851
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AD
852=head2 Finding Magic
853
854 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
855
856This routine returns a pointer to the C<MAGIC> structure stored in the SV.
857If the SV does not have that magical feature, C<NULL> is returned. Also,
54310121 858if the SV is not of type SVt_PVMG, Perl may core dump.
d1b91892
AD
859
860 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
861
862This routine checks to see what types of magic C<sv> has. If the mg_type
68dc0745
PP
863field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
864the mg_type field is changed to be the lowercase letter.
a0d0e21e 865
04343c6d
GS
866=head2 Understanding the Magic of Tied Hashes and Arrays
867
868Tied hashes and arrays are magical beasts of the 'P' magic type.
9edb2b46
GS
869
870WARNING: As of the 5.004 release, proper usage of the array and hash
871access functions requires understanding a few caveats. Some
872of these caveats are actually considered bugs in the API, to be fixed
873in later releases, and are bracketed with [MAYCHANGE] below. If
874you find yourself actually applying such information in this section, be
875aware that the behavior may change in the future, umm, without warning.
04343c6d
GS
876
877The C<av_store> function, when given a tied array argument, merely
878copies the magic of the array onto the value to be "stored", using
879C<mg_copy>. It may also return NULL, indicating that the value did not
9edb2b46
GS
880actually need to be stored in the array. [MAYCHANGE] After a call to
881C<av_store> on a tied array, the caller will usually need to call
882C<mg_set(val)> to actually invoke the perl level "STORE" method on the
883TIEARRAY object. If C<av_store> did return NULL, a call to
884C<SvREFCNT_dec(val)> will also be usually necessary to avoid a memory
885leak. [/MAYCHANGE]
04343c6d
GS
886
887The previous paragraph is applicable verbatim to tied hash access using the
888C<hv_store> and C<hv_store_ent> functions as well.
889
890C<av_fetch> and the corresponding hash functions C<hv_fetch> and
891C<hv_fetch_ent> actually return an undefined mortal value whose magic
892has been initialized using C<mg_copy>. Note the value so returned does not
9edb2b46
GS
893need to be deallocated, as it is already mortal. [MAYCHANGE] But you will
894need to call C<mg_get()> on the returned value in order to actually invoke
895the perl level "FETCH" method on the underlying TIE object. Similarly,
04343c6d
GS
896you may also call C<mg_set()> on the return value after possibly assigning
897a suitable value to it using C<sv_setsv>, which will invoke the "STORE"
9edb2b46 898method on the TIE object. [/MAYCHANGE]
04343c6d 899
9edb2b46 900[MAYCHANGE]
04343c6d
GS
901In other words, the array or hash fetch/store functions don't really
902fetch and store actual values in the case of tied arrays and hashes. They
903merely call C<mg_copy> to attach magic to the values that were meant to be
904"stored" or "fetched". Later calls to C<mg_get> and C<mg_set> actually
905do the job of invoking the TIE methods on the underlying objects. Thus
9edb2b46 906the magic mechanism currently implements a kind of lazy access to arrays
04343c6d
GS
907and hashes.
908
909Currently (as of perl version 5.004), use of the hash and array access
910functions requires the user to be aware of whether they are operating on
9edb2b46
GS
911"normal" hashes and arrays, or on their tied variants. The API may be
912changed to provide more transparent access to both tied and normal data
913types in future versions.
914[/MAYCHANGE]
04343c6d
GS
915
916You would do well to understand that the TIEARRAY and TIEHASH interfaces
917are mere sugar to invoke some perl method calls while using the uniform hash
918and array syntax. The use of this sugar imposes some overhead (typically
919about two to four extra opcodes per FETCH/STORE operation, in addition to
920the creation of all the mortal variables required to invoke the methods).
921This overhead will be comparatively small if the TIE methods are themselves
922substantial, but if they are only a few statements long, the overhead
923will not be insignificant.
924
d1c897a1
IZ
925=head2 Localizing changes
926
927Perl has a very handy construction
928
929 {
930 local $var = 2;
931 ...
932 }
933
934This construction is I<approximately> equivalent to
935
936 {
937 my $oldvar = $var;
938 $var = 2;
939 ...
940 $var = $oldvar;
941 }
942
943The biggest difference is that the first construction would
944reinstate the initial value of $var, irrespective of how control exits
945the block: C<goto>, C<return>, C<die>/C<eval> etc. It is a little bit
946more efficient as well.
947
948There is a way to achieve a similar task from C via Perl API: create a
949I<pseudo-block>, and arrange for some changes to be automatically
950undone at the end of it, either explicit, or via a non-local exit (via
951die()). A I<block>-like construct is created by a pair of
952C<ENTER>/C<LEAVE> macros (see L<perlcall/EXAMPLE/"Returning a
953Scalar">). Such a construct may be created specially for some
954important localized task, or an existing one (like boundaries of
955enclosing Perl subroutine/block, or an existing pair for freeing TMPs)
956may be used. (In the second case the overhead of additional
957localization must be almost negligible.) Note that any XSUB is
958automatically enclosed in an C<ENTER>/C<LEAVE> pair.
959
960Inside such a I<pseudo-block> the following service is available:
961
962=over
963
964=item C<SAVEINT(int i)>
965
966=item C<SAVEIV(IV i)>
967
968=item C<SAVEI32(I32 i)>
969
970=item C<SAVELONG(long i)>
971
972These macros arrange things to restore the value of integer variable
973C<i> at the end of enclosing I<pseudo-block>.
974
975=item C<SAVESPTR(s)>
976
977=item C<SAVEPPTR(p)>
978
979These macros arrange things to restore the value of pointers C<s> and
980C<p>. C<s> must be a pointer of a type which survives conversion to
981C<SV*> and back, C<p> should be able to survive conversion to C<char*>
982and back.
983
984=item C<SAVEFREESV(SV *sv)>
985
986The refcount of C<sv> would be decremented at the end of
987I<pseudo-block>. This is similar to C<sv_2mortal>, which should (?) be
988used instead.
989
990=item C<SAVEFREEOP(OP *op)>
991
992The C<OP *> is op_free()ed at the end of I<pseudo-block>.
993
994=item C<SAVEFREEPV(p)>
995
996The chunk of memory which is pointed to by C<p> is Safefree()ed at the
997end of I<pseudo-block>.
998
999=item C<SAVECLEARSV(SV *sv)>
1000
1001Clears a slot in the current scratchpad which corresponds to C<sv> at
1002the end of I<pseudo-block>.
1003
1004=item C<SAVEDELETE(HV *hv, char *key, I32 length)>
1005
1006The key C<key> of C<hv> is deleted at the end of I<pseudo-block>. The
1007string pointed to by C<key> is Safefree()ed. If one has a I<key> in
1008short-lived storage, the corresponding string may be reallocated like
1009this:
1010
1011 SAVEDELETE(defstash, savepv(tmpbuf), strlen(tmpbuf));
1012
1013=item C<SAVEDESTRUCTOR(f,p)>
1014
1015At the end of I<pseudo-block> the function C<f> is called with the
1016only argument (of type C<void*>) C<p>.
1017
1018=item C<SAVESTACK_POS()>
1019
1020The current offset on the Perl internal stack (cf. C<SP>) is restored
1021at the end of I<pseudo-block>.
1022
1023=back
1024
1025The following API list contains functions, thus one needs to
1026provide pointers to the modifiable data explicitly (either C pointers,
1027or Perlish C<GV *>s). Where the above macros take C<int>, a similar
1028function takes C<int *>.
1029
1030=over
1031
1032=item C<SV* save_scalar(GV *gv)>
1033
1034Equivalent to Perl code C<local $gv>.
1035
1036=item C<AV* save_ary(GV *gv)>
1037
1038=item C<HV* save_hash(GV *gv)>
1039
1040Similar to C<save_scalar>, but localize C<@gv> and C<%gv>.
1041
1042=item C<void save_item(SV *item)>
1043
1044Duplicates the current value of C<SV>, on the exit from the current
1045C<ENTER>/C<LEAVE> I<pseudo-block> will restore the value of C<SV>
1046using the stored value.
1047
1048=item C<void save_list(SV **sarg, I32 maxsarg)>
1049
1050A variant of C<save_item> which takes multiple arguments via an array
1051C<sarg> of C<SV*> of length C<maxsarg>.
1052
1053=item C<SV* save_svref(SV **sptr)>
1054
1055Similar to C<save_scalar>, but will reinstate a C<SV *>.
1056
1057=item C<void save_aptr(AV **aptr)>
1058
1059=item C<void save_hptr(HV **hptr)>
1060
1061Similar to C<save_svref>, but localize C<AV *> and C<HV *>.
1062
1063=back
1064
1065The C<Alias> module implements localization of the basic types within the
1066I<caller's scope>. People who are interested in how to localize things in
1067the containing scope should take a look there too.
1068
0a753a76 1069=head1 Subroutines
a0d0e21e 1070
68dc0745 1071=head2 XSUBs and the Argument Stack
5f05dabc
PP
1072
1073The XSUB mechanism is a simple way for Perl programs to access C subroutines.
1074An XSUB routine will have a stack that contains the arguments from the Perl
1075program, and a way to map from the Perl data structures to a C equivalent.
1076
1077The stack arguments are accessible through the C<ST(n)> macro, which returns
1078the C<n>'th stack argument. Argument 0 is the first argument passed in the
1079Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
1080an C<SV*> is used.
1081
1082Most of the time, output from the C routine can be handled through use of
1083the RETVAL and OUTPUT directives. However, there are some cases where the
1084argument stack is not already long enough to handle all the return values.
1085An example is the POSIX tzname() call, which takes no arguments, but returns
1086two, the local time zone's standard and summer time abbreviations.
1087
1088To handle this situation, the PPCODE directive is used and the stack is
1089extended using the macro:
1090
924508f0 1091 EXTEND(SP, num);
5f05dabc 1092
924508f0
GS
1093where C<SP> is the macro that represents the local copy of the stack pointer,
1094and C<num> is the number of elements the stack should be extended by.
5f05dabc
PP
1095
1096Now that there is room on the stack, values can be pushed on it using the
54310121 1097macros to push IVs, doubles, strings, and SV pointers respectively:
5f05dabc
PP
1098
1099 PUSHi(IV)
1100 PUSHn(double)
1101 PUSHp(char*, I32)
1102 PUSHs(SV*)
1103
1104And now the Perl program calling C<tzname>, the two values will be assigned
1105as in:
1106
1107 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
1108
1109An alternate (and possibly simpler) method to pushing values on the stack is
1110to use the macros:
1111
1112 XPUSHi(IV)
1113 XPUSHn(double)
1114 XPUSHp(char*, I32)
1115 XPUSHs(SV*)
1116
1117These macros automatically adjust the stack for you, if needed. Thus, you
1118do not need to call C<EXTEND> to extend the stack.
1119
1120For more information, consult L<perlxs> and L<perlxstut>.
1121
1122=head2 Calling Perl Routines from within C Programs
a0d0e21e
LW
1123
1124There are four routines that can be used to call a Perl subroutine from
1125within a C program. These four are:
1126
1127 I32 perl_call_sv(SV*, I32);
1128 I32 perl_call_pv(char*, I32);
1129 I32 perl_call_method(char*, I32);
1130 I32 perl_call_argv(char*, I32, register char**);
1131
d1b91892
AD
1132The routine most often used is C<perl_call_sv>. The C<SV*> argument
1133contains either the name of the Perl subroutine to be called, or a
1134reference to the subroutine. The second argument consists of flags
1135that control the context in which the subroutine is called, whether
1136or not the subroutine is being passed arguments, how errors should be
1137trapped, and how to treat return values.
a0d0e21e
LW
1138
1139All four routines return the number of arguments that the subroutine returned
1140on the Perl stack.
1141
d1b91892
AD
1142When using any of these routines (except C<perl_call_argv>), the programmer
1143must manipulate the Perl stack. These include the following macros and
1144functions:
a0d0e21e
LW
1145
1146 dSP
924508f0 1147 SP
a0d0e21e
LW
1148 PUSHMARK()
1149 PUTBACK
1150 SPAGAIN
1151 ENTER
1152 SAVETMPS
1153 FREETMPS
1154 LEAVE
1155 XPUSH*()
cb1a09d0 1156 POP*()
a0d0e21e 1157
5f05dabc
PP
1158For a detailed description of calling conventions from C to Perl,
1159consult L<perlcall>.
a0d0e21e 1160
5f05dabc 1161=head2 Memory Allocation
a0d0e21e 1162
5f05dabc
PP
1163It is suggested that you use the version of malloc that is distributed
1164with Perl. It keeps pools of various sizes of unallocated memory in
07fa94a1
JO
1165order to satisfy allocation requests more quickly. However, on some
1166platforms, it may cause spurious malloc or free errors.
d1b91892
AD
1167
1168 New(x, pointer, number, type);
1169 Newc(x, pointer, number, type, cast);
1170 Newz(x, pointer, number, type);
1171
07fa94a1 1172These three macros are used to initially allocate memory.
5f05dabc
PP
1173
1174The first argument C<x> was a "magic cookie" that was used to keep track
1175of who called the macro, to help when debugging memory problems. However,
07fa94a1
JO
1176the current code makes no use of this feature (most Perl developers now
1177use run-time memory checkers), so this argument can be any number.
5f05dabc
PP
1178
1179The second argument C<pointer> should be the name of a variable that will
1180point to the newly allocated memory.
d1b91892 1181
d1b91892
AD
1182The third and fourth arguments C<number> and C<type> specify how many of
1183the specified type of data structure should be allocated. The argument
1184C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
1185should be used if the C<pointer> argument is different from the C<type>
1186argument.
1187
1188Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
1189to zero out all the newly allocated memory.
1190
1191 Renew(pointer, number, type);
1192 Renewc(pointer, number, type, cast);
1193 Safefree(pointer)
1194
1195These three macros are used to change a memory buffer size or to free a
1196piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
1197match those of C<New> and C<Newc> with the exception of not needing the
1198"magic cookie" argument.
1199
1200 Move(source, dest, number, type);
1201 Copy(source, dest, number, type);
1202 Zero(dest, number, type);
1203
1204These three macros are used to move, copy, or zero out previously allocated
1205memory. The C<source> and C<dest> arguments point to the source and
1206destination starting points. Perl will move, copy, or zero out C<number>
1207instances of the size of the C<type> data structure (using the C<sizeof>
1208function).
a0d0e21e 1209
5f05dabc 1210=head2 PerlIO
ce3d39e2 1211
5f05dabc
PP
1212The most recent development releases of Perl has been experimenting with
1213removing Perl's dependency on the "normal" standard I/O suite and allowing
1214other stdio implementations to be used. This involves creating a new
1215abstraction layer that then calls whichever implementation of stdio Perl
68dc0745 1216was compiled with. All XSUBs should now use the functions in the PerlIO
5f05dabc
PP
1217abstraction layer and not make any assumptions about what kind of stdio
1218is being used.
1219
1220For a complete description of the PerlIO abstraction, consult L<perlapio>.
1221
8ebc5c01 1222=head2 Putting a C value on Perl stack
ce3d39e2
IZ
1223
1224A lot of opcodes (this is an elementary operation in the internal perl
1225stack machine) put an SV* on the stack. However, as an optimization
1226the corresponding SV is (usually) not recreated each time. The opcodes
1227reuse specially assigned SVs (I<target>s) which are (as a corollary)
1228not constantly freed/created.
1229
0a753a76 1230Each of the targets is created only once (but see
ce3d39e2
IZ
1231L<Scratchpads and recursion> below), and when an opcode needs to put
1232an integer, a double, or a string on stack, it just sets the
1233corresponding parts of its I<target> and puts the I<target> on stack.
1234
1235The macro to put this target on stack is C<PUSHTARG>, and it is
1236directly used in some opcodes, as well as indirectly in zillions of
1237others, which use it via C<(X)PUSH[pni]>.
1238
8ebc5c01 1239=head2 Scratchpads
ce3d39e2 1240
54310121 1241The question remains on when the SVs which are I<target>s for opcodes
5f05dabc
PP
1242are created. The answer is that they are created when the current unit --
1243a subroutine or a file (for opcodes for statements outside of
1244subroutines) -- is compiled. During this time a special anonymous Perl
ce3d39e2
IZ
1245array is created, which is called a scratchpad for the current
1246unit.
1247
54310121 1248A scratchpad keeps SVs which are lexicals for the current unit and are
ce3d39e2
IZ
1249targets for opcodes. One can deduce that an SV lives on a scratchpad
1250by looking on its flags: lexicals have C<SVs_PADMY> set, and
1251I<target>s have C<SVs_PADTMP> set.
1252
54310121
PP
1253The correspondence between OPs and I<target>s is not 1-to-1. Different
1254OPs in the compile tree of the unit can use the same target, if this
ce3d39e2
IZ
1255would not conflict with the expected life of the temporary.
1256
2ae324a7 1257=head2 Scratchpads and recursion
ce3d39e2
IZ
1258
1259In fact it is not 100% true that a compiled unit contains a pointer to
1260the scratchpad AV. In fact it contains a pointer to an AV of
1261(initially) one element, and this element is the scratchpad AV. Why do
1262we need an extra level of indirection?
1263
1264The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1265these can create several execution pointers going into the same
1266subroutine. For the subroutine-child not write over the temporaries
1267for the subroutine-parent (lifespan of which covers the call to the
1268child), the parent and the child should have different
1269scratchpads. (I<And> the lexicals should be separate anyway!)
1270
5f05dabc
PP
1271So each subroutine is born with an array of scratchpads (of length 1).
1272On each entry to the subroutine it is checked that the current
ce3d39e2
IZ
1273depth of the recursion is not more than the length of this array, and
1274if it is, new scratchpad is created and pushed into the array.
1275
1276The I<target>s on this scratchpad are C<undef>s, but they are already
1277marked with correct flags.
1278
0a753a76
PP
1279=head1 Compiled code
1280
1281=head2 Code tree
1282
1283Here we describe the internal form your code is converted to by
1284Perl. Start with a simple example:
1285
1286 $a = $b + $c;
1287
1288This is converted to a tree similar to this one:
1289
1290 assign-to
1291 / \
1292 + $a
1293 / \
1294 $b $c
1295
1296(but slightly more complicated). This tree reflect the way Perl
1297parsed your code, but has nothing to do with the execution order.
1298There is an additional "thread" going through the nodes of the tree
1299which shows the order of execution of the nodes. In our simplified
1300example above it looks like:
1301
1302 $b ---> $c ---> + ---> $a ---> assign-to
1303
1304But with the actual compile tree for C<$a = $b + $c> it is different:
1305some nodes I<optimized away>. As a corollary, though the actual tree
1306contains more nodes than our simplified example, the execution order
1307is the same as in our example.
1308
1309=head2 Examining the tree
1310
1311If you have your perl compiled for debugging (usually done with C<-D
1312optimize=-g> on C<Configure> command line), you may examine the
1313compiled tree by specifying C<-Dx> on the Perl command line. The
1314output takes several lines per node, and for C<$b+$c> it looks like
1315this:
1316
1317 5 TYPE = add ===> 6
1318 TARG = 1
1319 FLAGS = (SCALAR,KIDS)
1320 {
1321 TYPE = null ===> (4)
1322 (was rv2sv)
1323 FLAGS = (SCALAR,KIDS)
1324 {
1325 3 TYPE = gvsv ===> 4
1326 FLAGS = (SCALAR)
1327 GV = main::b
1328 }
1329 }
1330 {
1331 TYPE = null ===> (5)
1332 (was rv2sv)
1333 FLAGS = (SCALAR,KIDS)
1334 {
1335 4 TYPE = gvsv ===> 5
1336 FLAGS = (SCALAR)
1337 GV = main::c
1338 }
1339 }
1340
1341This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1342not optimized away (one per number in the left column). The immediate
1343children of the given node correspond to C<{}> pairs on the same level
1344of indentation, thus this listing corresponds to the tree:
1345
1346 add
1347 / \
1348 null null
1349 | |
1350 gvsv gvsv
1351
1352The execution order is indicated by C<===E<gt>> marks, thus it is C<3
13534 5 6> (node C<6> is not included into above listing), i.e.,
1354C<gvsv gvsv add whatever>.
1355
1356=head2 Compile pass 1: check routines
1357
1358The tree is created by the I<pseudo-compiler> while yacc code feeds it
1359the constructions it recognizes. Since yacc works bottom-up, so does
1360the first pass of perl compilation.
1361
1362What makes this pass interesting for perl developers is that some
1363optimization may be performed on this pass. This is optimization by
1364so-called I<check routines>. The correspondence between node names
1365and corresponding check routines is described in F<opcode.pl> (do not
1366forget to run C<make regen_headers> if you modify this file).
1367
1368A check routine is called when the node is fully constructed except
1369for the execution-order thread. Since at this time there is no
1370back-links to the currently constructed node, one can do most any
1371operation to the top-level node, including freeing it and/or creating
1372new nodes above/below it.
1373
1374The check routine returns the node which should be inserted into the
1375tree (if the top-level node was not modified, check routine returns
1376its argument).
1377
1378By convention, check routines have names C<ck_*>. They are usually
1379called from C<new*OP> subroutines (or C<convert>) (which in turn are
1380called from F<perly.y>).
1381
1382=head2 Compile pass 1a: constant folding
1383
1384Immediately after the check routine is called the returned node is
1385checked for being compile-time executable. If it is (the value is
1386judged to be constant) it is immediately executed, and a I<constant>
1387node with the "return value" of the corresponding subtree is
1388substituted instead. The subtree is deleted.
1389
1390If constant folding was not performed, the execution-order thread is
1391created.
1392
1393=head2 Compile pass 2: context propagation
1394
1395When a context for a part of compile tree is known, it is propagated
1396down through the tree. Aat this time the context can have 5 values
1397(instead of 2 for runtime context): void, boolean, scalar, list, and
1398lvalue. In contrast with the pass 1 this pass is processed from top
1399to bottom: a node's context determines the context for its children.
1400
1401Additional context-dependent optimizations are performed at this time.
1402Since at this moment the compile tree contains back-references (via
1403"thread" pointers), nodes cannot be free()d now. To allow
1404optimized-away nodes at this stage, such nodes are null()ified instead
1405of free()ing (i.e. their type is changed to OP_NULL).
1406
1407=head2 Compile pass 3: peephole optimization
1408
1409After the compile tree for a subroutine (or for an C<eval> or a file)
1410is created, an additional pass over the code is performed. This pass
1411is neither top-down or bottom-up, but in the execution order (with
1412additional compilications for conditionals). These optimizations are
1413done in the subroutine peep(). Optimizations performed at this stage
1414are subject to the same restrictions as in the pass 2.
1415
1416=head1 API LISTING
a0d0e21e 1417
cb1a09d0
AD
1418This is a listing of functions, macros, flags, and variables that may be
1419useful to extension writers or that may be found while reading other
1420extensions.
e89caa19
GA
1421The sort order of the listing is case insensitive, with any
1422occurrences of '_' ignored for the the purpose of sorting.
a0d0e21e 1423
cb1a09d0 1424=over 8
a0d0e21e 1425
cb1a09d0
AD
1426=item av_clear
1427
0146554f
GA
1428Clears an array, making it empty. Does not free the memory used by the
1429array itself.
cb1a09d0 1430
ef50df4b 1431 void av_clear (AV* ar)
cb1a09d0
AD
1432
1433=item av_extend
1434
1435Pre-extend an array. The C<key> is the index to which the array should be
1436extended.
1437
ef50df4b 1438 void av_extend (AV* ar, I32 key)
cb1a09d0
AD
1439
1440=item av_fetch
1441
1442Returns the SV at the specified index in the array. The C<key> is the
1443index. If C<lval> is set then the fetch will be part of a store. Check
1444that the return value is non-null before dereferencing it to a C<SV*>.
1445
04343c6d
GS
1446See L<Understanding the Magic of Tied Hashes and Arrays> for more
1447information on how to use this function on tied arrays.
1448
ef50df4b 1449 SV** av_fetch (AV* ar, I32 key, I32 lval)
cb1a09d0 1450
e89caa19
GA
1451=item AvFILL
1452
1453Same as C<av_len>.
1454
cb1a09d0
AD
1455=item av_len
1456
1457Returns the highest index in the array. Returns -1 if the array is empty.
1458
ef50df4b 1459 I32 av_len (AV* ar)
cb1a09d0
AD
1460
1461=item av_make
1462
5fb8527f
PP
1463Creates a new AV and populates it with a list of SVs. The SVs are copied
1464into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1465will have a reference count of 1.
cb1a09d0 1466
ef50df4b 1467 AV* av_make (I32 size, SV** svp)
cb1a09d0
AD
1468
1469=item av_pop
1470
1471Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
1472empty.
1473
ef50df4b 1474 SV* av_pop (AV* ar)
cb1a09d0
AD
1475
1476=item av_push
1477
5fb8527f
PP
1478Pushes an SV onto the end of the array. The array will grow automatically
1479to accommodate the addition.
cb1a09d0 1480
ef50df4b 1481 void av_push (AV* ar, SV* val)
cb1a09d0
AD
1482
1483=item av_shift
1484
1485Shifts an SV off the beginning of the array.
1486
ef50df4b 1487 SV* av_shift (AV* ar)
cb1a09d0
AD
1488
1489=item av_store
1490
1491Stores an SV in an array. The array index is specified as C<key>. The
04343c6d
GS
1492return value will be NULL if the operation failed or if the value did not
1493need to be actually stored within the array (as in the case of tied arrays).
1494Otherwise it can be dereferenced to get the original C<SV*>. Note that the
1495caller is responsible for suitably incrementing the reference count of C<val>
1496before the call, and decrementing it if the function returned NULL.
1497
1498See L<Understanding the Magic of Tied Hashes and Arrays> for more
1499information on how to use this function on tied arrays.
cb1a09d0 1500
ef50df4b 1501 SV** av_store (AV* ar, I32 key, SV* val)
cb1a09d0
AD
1502
1503=item av_undef
1504
0146554f 1505Undefines the array. Frees the memory used by the array itself.
cb1a09d0 1506
ef50df4b 1507 void av_undef (AV* ar)
cb1a09d0
AD
1508
1509=item av_unshift
1510
0146554f
GA
1511Unshift the given number of C<undef> values onto the beginning of the
1512array. The array will grow automatically to accommodate the addition.
1513You must then use C<av_store> to assign values to these new elements.
cb1a09d0 1514
ef50df4b 1515 void av_unshift (AV* ar, I32 num)
cb1a09d0
AD
1516
1517=item CLASS
1518
1519Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1520constructor. This is always a C<char*>. See C<THIS> and
1521L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1522
1523=item Copy
1524
1525The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1526source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 1527the type. May fail on overlapping copies. See also C<Move>.
cb1a09d0 1528
e89caa19 1529 void Copy( s, d, n, t )
cb1a09d0
AD
1530
1531=item croak
1532
1533This is the XSUB-writer's interface to Perl's C<die> function. Use this
1534function the same way you use the C C<printf> function. See C<warn>.
1535
1536=item CvSTASH
1537
1538Returns the stash of the CV.
1539
e89caa19 1540 HV* CvSTASH( SV* sv )
cb1a09d0
AD
1541
1542=item DBsingle
1543
1544When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1545boolean which indicates whether subs are being single-stepped.
5fb8527f
PP
1546Single-stepping is automatically turned on after every step. This is the C
1547variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
cb1a09d0
AD
1548
1549=item DBsub
1550
1551When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f
PP
1552the SV which holds the name of the sub being debugged. This is the C
1553variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
cb1a09d0
AD
1554The sub name can be found by
1555
1556 SvPV( GvSV( DBsub ), na )
1557
5fb8527f
PP
1558=item DBtrace
1559
1560Trace variable used when Perl is run in debugging mode, with the B<-d>
1561switch. This is the C variable which corresponds to Perl's $DB::trace
1562variable. See C<DBsingle>.
1563
cb1a09d0
AD
1564=item dMARK
1565
5fb8527f
PP
1566Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1567C<dORIGMARK>.
cb1a09d0
AD
1568
1569=item dORIGMARK
1570
1571Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1572
5fb8527f
PP
1573=item dowarn
1574
1575The C variable which corresponds to Perl's $^W warning variable.
1576
cb1a09d0
AD
1577=item dSP
1578
924508f0
GS
1579Declares a local copy of perl's stack pointer for the XSUB, available via
1580the C<SP> macro. See C<SP>.
cb1a09d0
AD
1581
1582=item dXSARGS
1583
1584Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1585usually handled automatically by C<xsubpp>. Declares the C<items> variable
1586to indicate the number of items on the stack.
1587
5fb8527f
PP
1588=item dXSI32
1589
1590Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1591handled automatically by C<xsubpp>.
1592
cb1a09d0
AD
1593=item ENTER
1594
1595Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1596
1597 ENTER;
1598
1599=item EXTEND
1600
1601Used to extend the argument stack for an XSUB's return values.
1602
ef50df4b 1603 EXTEND( sp, int x )
cb1a09d0 1604
e89caa19
GA
1605=item fbm_compile
1606
1607Analyses the string in order to make fast searches on it using fbm_instr() --
1608the Boyer-Moore algorithm.
1609
1610 void fbm_compile(SV* sv)
1611
1612=item fbm_instr
1613
1614Returns the location of the SV in the string delimited by C<str> and
1615C<strend>. It returns C<Nullch> if the string can't be found. The
1616C<sv> does not have to be fbm_compiled, but the search will not be as
1617fast then.
1618
1619 char* fbm_instr(char *str, char *strend, SV *sv)
1620
cb1a09d0
AD
1621=item FREETMPS
1622
1623Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1624L<perlcall>.
1625
1626 FREETMPS;
1627
1628=item G_ARRAY
1629
54310121 1630Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
cb1a09d0
AD
1631
1632=item G_DISCARD
1633
1634Indicates that arguments returned from a callback should be discarded. See
1635L<perlcall>.
1636
1637=item G_EVAL
1638
1639Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1640
1641=item GIMME
1642
54310121
PP
1643A backward-compatible version of C<GIMME_V> which can only return
1644C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
1645
1646=item GIMME_V
1647
1648The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
1649C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
1650context, respectively.
cb1a09d0
AD
1651
1652=item G_NOARGS
1653
1654Indicates that no arguments are being sent to a callback. See L<perlcall>.
1655
1656=item G_SCALAR
1657
54310121
PP
1658Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
1659
faed5253
JO
1660=item gv_fetchmeth
1661
1662Returns the glob with the given C<name> and a defined subroutine or
9607fc9c
PP
1663C<NULL>. The glob lives in the given C<stash>, or in the stashes
1664accessable via @ISA and @<UNIVERSAL>.
faed5253 1665
9607fc9c 1666The argument C<level> should be either 0 or -1. If C<level==0>, as a
0a753a76
PP
1667side-effect creates a glob with the given C<name> in the given
1668C<stash> which in the case of success contains an alias for the
1669subroutine, and sets up caching info for this glob. Similarly for all
1670the searched stashes.
1671
9607fc9c
PP
1672This function grants C<"SUPER"> token as a postfix of the stash name.
1673
0a753a76
PP
1674The GV returned from C<gv_fetchmeth> may be a method cache entry,
1675which is not visible to Perl code. So when calling C<perl_call_sv>,
1676you should not use the GV directly; instead, you should use the
1677method's CV, which can be obtained from the GV with the C<GvCV> macro.
faed5253 1678
ef50df4b 1679 GV* gv_fetchmeth (HV* stash, char* name, STRLEN len, I32 level)
faed5253
JO
1680
1681=item gv_fetchmethod
1682
dc848c6f
PP
1683=item gv_fetchmethod_autoload
1684
faed5253 1685Returns the glob which contains the subroutine to call to invoke the
dc848c6f
PP
1686method on the C<stash>. In fact in the presense of autoloading this may
1687be the glob for "AUTOLOAD". In this case the corresponding variable
faed5253
JO
1688$AUTOLOAD is already setup.
1689
dc848c6f
PP
1690The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
1691lookup is performed if the given method is not present: non-zero means
1692yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
1693C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
1694non-zero C<autoload> parameter.
1695
1696These functions grant C<"SUPER"> token as a prefix of the method name.
1697
1698Note that if you want to keep the returned glob for a long time, you
1699need to check for it being "AUTOLOAD", since at the later time the call
faed5253
JO
1700may load a different subroutine due to $AUTOLOAD changing its value.
1701Use the glob created via a side effect to do this.
1702
dc848c6f
PP
1703These functions have the same side-effects and as C<gv_fetchmeth> with
1704C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
0a753a76 1705The warning against passing the GV returned by C<gv_fetchmeth> to
dc848c6f 1706C<perl_call_sv> apply equally to these functions.
faed5253 1707
ef50df4b
GS
1708 GV* gv_fetchmethod (HV* stash, char* name)
1709 GV* gv_fetchmethod_autoload (HV* stash, char* name, I32 autoload)
faed5253 1710
e89caa19
GA
1711=item G_VOID
1712
1713Used to indicate void context. See C<GIMME_V> and L<perlcall>.
1714
cb1a09d0
AD
1715=item gv_stashpv
1716
1717Returns a pointer to the stash for a specified package. If C<create> is set
1718then the package will be created if it does not already exist. If C<create>
1719is not set and the package does not exist then NULL is returned.
1720
ef50df4b 1721 HV* gv_stashpv (char* name, I32 create)
cb1a09d0
AD
1722
1723=item gv_stashsv
1724
1725Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1726
ef50df4b 1727 HV* gv_stashsv (SV* sv, I32 create)
cb1a09d0 1728
e5581bf4 1729=item GvSV
cb1a09d0 1730
e5581bf4 1731Return the SV from the GV.
44a8e56a 1732
1e422769
PP
1733=item HEf_SVKEY
1734
1735This flag, used in the length slot of hash entries and magic
1736structures, specifies the structure contains a C<SV*> pointer where a
1737C<char*> pointer is to be expected. (For information only--not to be used).
1738
1e422769
PP
1739=item HeHASH
1740
e89caa19 1741Returns the computed hash stored in the hash entry.
1e422769 1742
e89caa19 1743 U32 HeHASH(HE* he)
1e422769
PP
1744
1745=item HeKEY
1746
1747Returns the actual pointer stored in the key slot of the hash entry.
1748The pointer may be either C<char*> or C<SV*>, depending on the value of
1749C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1750are usually preferable for finding the value of a key.
1751
e89caa19 1752 char* HeKEY(HE* he)
1e422769
PP
1753
1754=item HeKLEN
1755
1756If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1757holds an C<SV*> key. Otherwise, holds the actual length of the key.
1758Can be assigned to. The C<HePV()> macro is usually preferable for finding
1759key lengths.
1760
e89caa19 1761 int HeKLEN(HE* he)
1e422769
PP
1762
1763=item HePV
1764
1765Returns the key slot of the hash entry as a C<char*> value, doing any
1766necessary dereferencing of possibly C<SV*> keys. The length of
1767the string is placed in C<len> (this is a macro, so do I<not> use
1768C<&len>). If you do not care about what the length of the key is,
1769you may use the global variable C<na>. Remember though, that hash
1770keys in perl are free to contain embedded nulls, so using C<strlen()>
1771or similar is not a good way to find the length of hash keys.
1772This is very similar to the C<SvPV()> macro described elsewhere in
1773this document.
1774
e89caa19 1775 char* HePV(HE* he, STRLEN len)
1e422769
PP
1776
1777=item HeSVKEY
1778
1779Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1780does not contain an C<SV*> key.
1781
1782 HeSVKEY(HE* he)
1783
1784=item HeSVKEY_force
1785
1786Returns the key as an C<SV*>. Will create and return a temporary
1787mortal C<SV*> if the hash entry contains only a C<char*> key.
1788
1789 HeSVKEY_force(HE* he)
1790
1791=item HeSVKEY_set
1792
1793Sets the key to a given C<SV*>, taking care to set the appropriate flags
1794to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1795
1796 HeSVKEY_set(HE* he, SV* sv)
1797
1798=item HeVAL
1799
1800Returns the value slot (type C<SV*>) stored in the hash entry.
1801
1802 HeVAL(HE* he)
1803
cb1a09d0
AD
1804=item hv_clear
1805
1806Clears a hash, making it empty.
1807
ef50df4b 1808 void hv_clear (HV* tb)
cb1a09d0 1809
68dc0745
PP
1810=item hv_delayfree_ent
1811
1812Releases a hash entry, such as while iterating though the hash, but
1813delays actual freeing of key and value until the end of the current
1814statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
1815and C<hv_free_ent>.
1816
ef50df4b 1817 void hv_delayfree_ent (HV* hv, HE* entry)
68dc0745 1818
cb1a09d0
AD
1819=item hv_delete
1820
1821Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 1822and returned to the caller. The C<klen> is the length of the key. The
04343c6d 1823C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
cb1a09d0
AD
1824returned.
1825
ef50df4b 1826 SV* hv_delete (HV* tb, char* key, U32 klen, I32 flags)
cb1a09d0 1827
1e422769
PP
1828=item hv_delete_ent
1829
1830Deletes a key/value pair in the hash. The value SV is removed from the hash
1831and returned to the caller. The C<flags> value will normally be zero; if set
04343c6d 1832to G_DISCARD then NULL will be returned. C<hash> can be a valid precomputed
1e422769
PP
1833hash value, or 0 to ask for it to be computed.
1834
ef50df4b 1835 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash)
1e422769 1836
cb1a09d0
AD
1837=item hv_exists
1838
1839Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 1840C<klen> is the length of the key.
cb1a09d0 1841
ef50df4b 1842 bool hv_exists (HV* tb, char* key, U32 klen)
cb1a09d0 1843
1e422769
PP
1844=item hv_exists_ent
1845
1846Returns a boolean indicating whether the specified hash key exists. C<hash>
54310121 1847can be a valid precomputed hash value, or 0 to ask for it to be computed.
1e422769 1848
ef50df4b 1849 bool hv_exists_ent (HV* tb, SV* key, U32 hash)
1e422769 1850
cb1a09d0
AD
1851=item hv_fetch
1852
1853Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 1854C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
1855part of a store. Check that the return value is non-null before
1856dereferencing it to a C<SV*>.
1857
04343c6d
GS
1858See L<Understanding the Magic of Tied Hashes and Arrays> for more
1859information on how to use this function on tied hashes.
1860
ef50df4b 1861 SV** hv_fetch (HV* tb, char* key, U32 klen, I32 lval)
cb1a09d0 1862
1e422769
PP
1863=item hv_fetch_ent
1864
1865Returns the hash entry which corresponds to the specified key in the hash.
54310121 1866C<hash> must be a valid precomputed hash number for the given C<key>, or
1e422769
PP
18670 if you want the function to compute it. IF C<lval> is set then the
1868fetch will be part of a store. Make sure the return value is non-null
1869before accessing it. The return value when C<tb> is a tied hash
1870is a pointer to a static location, so be sure to make a copy of the
1871structure if you need to store it somewhere.
1872
04343c6d
GS
1873See L<Understanding the Magic of Tied Hashes and Arrays> for more
1874information on how to use this function on tied hashes.
1875
ef50df4b 1876 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash)
1e422769 1877
68dc0745
PP
1878=item hv_free_ent
1879
1880Releases a hash entry, such as while iterating though the hash. See
1881C<hv_iternext> and C<hv_delayfree_ent>.
1882
ef50df4b 1883 void hv_free_ent (HV* hv, HE* entry)
68dc0745 1884
cb1a09d0
AD
1885=item hv_iterinit
1886
1887Prepares a starting point to traverse a hash table.
1888
ef50df4b 1889 I32 hv_iterinit (HV* tb)
cb1a09d0 1890
c6601927
SI
1891Returns the number of keys in the hash (i.e. the same as C<HvKEYS(tb)>).
1892The return value is currently only meaningful for hashes without tie
1893magic.
1894
1895NOTE: Before version 5.004_65, C<hv_iterinit> used to return the number
1896of hash buckets that happen to be in use. If you still need that
1897esoteric value, you can get it through the macro C<HvFILL(tb)>.
fb73857a 1898
cb1a09d0
AD
1899=item hv_iterkey
1900
1901Returns the key from the current position of the hash iterator. See
1902C<hv_iterinit>.
1903
ef50df4b 1904 char* hv_iterkey (HE* entry, I32* retlen)
cb1a09d0 1905
1e422769 1906=item hv_iterkeysv
3fe9a6f1 1907
1e422769
PP
1908Returns the key as an C<SV*> from the current position of the hash
1909iterator. The return value will always be a mortal copy of the
1910key. Also see C<hv_iterinit>.
1911
ef50df4b 1912 SV* hv_iterkeysv (HE* entry)
1e422769 1913
cb1a09d0
AD
1914=item hv_iternext
1915
1916Returns entries from a hash iterator. See C<hv_iterinit>.
1917
ef50df4b 1918 HE* hv_iternext (HV* tb)
cb1a09d0
AD
1919
1920=item hv_iternextsv
1921
1922Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1923operation.
1924
e89caa19 1925 SV* hv_iternextsv (HV* hv, char** key, I32* retlen)
cb1a09d0
AD
1926
1927=item hv_iterval
1928
1929Returns the value from the current position of the hash iterator. See
1930C<hv_iterkey>.
1931
ef50df4b 1932 SV* hv_iterval (HV* tb, HE* entry)
cb1a09d0
AD
1933
1934=item hv_magic
1935
1936Adds magic to a hash. See C<sv_magic>.
1937
ef50df4b 1938 void hv_magic (HV* hv, GV* gv, int how)
cb1a09d0
AD
1939
1940=item HvNAME
1941
1942Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1943
e89caa19 1944 char* HvNAME (HV* stash)
cb1a09d0
AD
1945
1946=item hv_store
1947
1948Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
54310121 1949the length of the key. The C<hash> parameter is the precomputed hash
cb1a09d0 1950value; if it is zero then Perl will compute it. The return value will be
04343c6d
GS
1951NULL if the operation failed or if the value did not need to be actually
1952stored within the hash (as in the case of tied hashes). Otherwise it can
1953be dereferenced to get the original C<SV*>. Note that the caller is
1954responsible for suitably incrementing the reference count of C<val>
1955before the call, and decrementing it if the function returned NULL.
1956
1957See L<Understanding the Magic of Tied Hashes and Arrays> for more
1958information on how to use this function on tied hashes.
cb1a09d0 1959
ef50df4b 1960 SV** hv_store (HV* tb, char* key, U32 klen, SV* val, U32 hash)
cb1a09d0 1961
1e422769
PP
1962=item hv_store_ent
1963
1964Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
54310121 1965parameter is the precomputed hash value; if it is zero then Perl will
1e422769 1966compute it. The return value is the new hash entry so created. It will be
04343c6d
GS
1967NULL if the operation failed or if the value did not need to be actually
1968stored within the hash (as in the case of tied hashes). Otherwise the
1969contents of the return value can be accessed using the C<He???> macros
1970described here. Note that the caller is responsible for suitably
1971incrementing the reference count of C<val> before the call, and decrementing
1972it if the function returned NULL.
1973
1974See L<Understanding the Magic of Tied Hashes and Arrays> for more
1975information on how to use this function on tied hashes.
1e422769 1976
ef50df4b 1977 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash)
1e422769 1978
cb1a09d0
AD
1979=item hv_undef
1980
1981Undefines the hash.
1982
ef50df4b 1983 void hv_undef (HV* tb)
cb1a09d0
AD
1984
1985=item isALNUM
1986
1987Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 1988character or digit.
cb1a09d0 1989
e89caa19 1990 int isALNUM (char c)
cb1a09d0
AD
1991
1992=item isALPHA
1993
5fb8527f 1994Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
1995character.
1996
e89caa19 1997 int isALPHA (char c)
cb1a09d0
AD
1998
1999=item isDIGIT
2000
2001Returns a boolean indicating whether the C C<char> is an ascii digit.
2002
e89caa19 2003 int isDIGIT (char c)
cb1a09d0
AD
2004
2005=item isLOWER
2006
2007Returns a boolean indicating whether the C C<char> is a lowercase character.
2008
e89caa19 2009 int isLOWER (char c)
cb1a09d0
AD
2010
2011=item isSPACE
2012
2013Returns a boolean indicating whether the C C<char> is whitespace.
2014
e89caa19 2015 int isSPACE (char c)
cb1a09d0
AD
2016
2017=item isUPPER
2018
2019Returns a boolean indicating whether the C C<char> is an uppercase character.
2020
e89caa19 2021 int isUPPER (char c)
cb1a09d0
AD
2022
2023=item items
2024
2025Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
2026stack. See L<perlxs/"Variable-length Parameter Lists">.
2027
2028=item ix
2029
2030Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
2031was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
2032
2033=item LEAVE
2034
2035Closing bracket on a callback. See C<ENTER> and L<perlcall>.
2036
2037 LEAVE;
2038
e89caa19
GA
2039=item looks_like_number
2040
2041Test if an the content of an SV looks like a number (or is a number).
2042
2043 int looks_like_number(SV*)
2044
2045
cb1a09d0
AD
2046=item MARK
2047
5fb8527f 2048Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
2049
2050=item mg_clear
2051
2052Clear something magical that the SV represents. See C<sv_magic>.
2053
ef50df4b 2054 int mg_clear (SV* sv)
cb1a09d0
AD
2055
2056=item mg_copy
2057
2058Copies the magic from one SV to another. See C<sv_magic>.
2059
ef50df4b 2060 int mg_copy (SV *, SV *, char *, STRLEN)
cb1a09d0
AD
2061
2062=item mg_find
2063
2064Finds the magic pointer for type matching the SV. See C<sv_magic>.
2065
ef50df4b 2066 MAGIC* mg_find (SV* sv, int type)
cb1a09d0
AD
2067
2068=item mg_free
2069
2070Free any magic storage used by the SV. See C<sv_magic>.
2071
ef50df4b 2072 int mg_free (SV* sv)
cb1a09d0
AD
2073
2074=item mg_get
2075
2076Do magic after a value is retrieved from the SV. See C<sv_magic>.
2077
ef50df4b 2078 int mg_get (SV* sv)
cb1a09d0
AD
2079
2080=item mg_len
2081
2082Report on the SV's length. See C<sv_magic>.
2083
ef50df4b 2084 U32 mg_len (SV* sv)
cb1a09d0
AD
2085
2086=item mg_magical
2087
2088Turns on the magical status of an SV. See C<sv_magic>.
2089
ef50df4b 2090 void mg_magical (SV* sv)
cb1a09d0
AD
2091
2092=item mg_set
2093
2094Do magic after a value is assigned to the SV. See C<sv_magic>.
2095
ef50df4b 2096 int mg_set (SV* sv)
cb1a09d0
AD
2097
2098=item Move
2099
2100The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
2101source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 2102the type. Can do overlapping moves. See also C<Copy>.
cb1a09d0 2103
e89caa19 2104 void Move( s, d, n, t )
cb1a09d0
AD
2105
2106=item na
2107
2108A variable which may be used with C<SvPV> to tell Perl to calculate the
2109string length.
2110
2111=item New
2112
2113The XSUB-writer's interface to the C C<malloc> function.
2114
e89caa19 2115 void* New( x, void *ptr, int size, type )
cb1a09d0
AD
2116
2117=item newAV
2118
5f05dabc 2119Creates a new AV. The reference count is set to 1.
cb1a09d0 2120
ef50df4b 2121 AV* newAV (void)
cb1a09d0 2122
e89caa19
GA
2123=item Newc
2124
2125The XSUB-writer's interface to the C C<malloc> function, with cast.
2126
2127 void* Newc( x, void *ptr, int size, type, cast )
2128
5476c433
JD
2129=item newCONSTSUB
2130
2131Creates a constant sub equivalent to Perl C<sub FOO () { 123 }>
2132which is eligible for inlining at compile-time.
2133
2134 void newCONSTSUB(HV* stash, char* name, SV* sv)
2135
cb1a09d0
AD
2136=item newHV
2137
5f05dabc 2138Creates a new HV. The reference count is set to 1.
cb1a09d0 2139
ef50df4b 2140 HV* newHV (void)
cb1a09d0 2141
5f05dabc 2142=item newRV_inc
cb1a09d0 2143
5f05dabc 2144Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
2145incremented.
2146
ef50df4b 2147 SV* newRV_inc (SV* ref)
5f05dabc
PP
2148
2149For historical reasons, "newRV" is a synonym for "newRV_inc".
2150
2151=item newRV_noinc
2152
2153Creates an RV wrapper for an SV. The reference count for the original
2154SV is B<not> incremented.
2155
ef50df4b 2156 SV* newRV_noinc (SV* ref)
cb1a09d0 2157
8c52afec 2158=item NEWSV
cb1a09d0 2159
e89caa19
GA
2160Creates a new SV. A non-zero C<len> parameter indicates the number of
2161bytes of preallocated string space the SV should have. An extra byte
2162for a tailing NUL is also reserved. (SvPOK is not set for the SV even
2163if string space is allocated.) The reference count for the new SV is
2164set to 1. C<id> is an integer id between 0 and 1299 (used to identify
2165leaks).
cb1a09d0 2166
ef50df4b 2167 SV* NEWSV (int id, STRLEN len)
cb1a09d0
AD
2168
2169=item newSViv
2170
07fa94a1
JO
2171Creates a new SV and copies an integer into it. The reference count for the
2172SV is set to 1.
cb1a09d0 2173
ef50df4b 2174 SV* newSViv (IV i)
cb1a09d0
AD
2175
2176=item newSVnv
2177
07fa94a1
JO
2178Creates a new SV and copies a double into it. The reference count for the
2179SV is set to 1.
cb1a09d0 2180
ef50df4b 2181 SV* newSVnv (NV i)
cb1a09d0
AD
2182
2183=item newSVpv
2184
07fa94a1
JO
2185Creates a new SV and copies a string into it. The reference count for the
2186SV is set to 1. If C<len> is zero then Perl will compute the length.
cb1a09d0 2187
ef50df4b 2188 SV* newSVpv (char* s, STRLEN len)
cb1a09d0 2189
e89caa19
GA
2190=item newSVpvf
2191
2192Creates a new SV an initialize it with the string formatted like
2193C<sprintf>.
2194
2195 SV* newSVpvf(const char* pat, ...);
2196
9da1e3b5
MUN
2197=item newSVpvn
2198
2199Creates a new SV and copies a string into it. The reference count for the
2200SV is set to 1. If C<len> is zero then Perl will create a zero length
2201string.
2202
ef50df4b 2203 SV* newSVpvn (char* s, STRLEN len)
9da1e3b5 2204
cb1a09d0
AD
2205=item newSVrv
2206
2207Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 2208it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 2209be blessed in the specified package. The new SV is returned and its
5f05dabc 2210reference count is 1.
8ebc5c01 2211
ef50df4b 2212 SV* newSVrv (SV* rv, char* classname)
cb1a09d0
AD
2213
2214=item newSVsv
2215
5fb8527f 2216Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0 2217
ef50df4b 2218 SV* newSVsv (SV* old)
cb1a09d0
AD
2219
2220=item newXS
2221
2222Used by C<xsubpp> to hook up XSUBs as Perl subs.
2223
2224=item newXSproto
2225
2226Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
2227the subs.
2228
e89caa19
GA
2229=item Newz
2230
2231The XSUB-writer's interface to the C C<malloc> function. The allocated
2232memory is zeroed with C<memzero>.
2233
2234 void* Newz( x, void *ptr, int size, type )
2235
cb1a09d0
AD
2236=item Nullav
2237
2238Null AV pointer.
2239
2240=item Nullch
2241
2242Null character pointer.
2243
2244=item Nullcv
2245
2246Null CV pointer.
2247
2248=item Nullhv
2249
2250Null HV pointer.
2251
2252=item Nullsv
2253
2254Null SV pointer.
2255
2256=item ORIGMARK
2257
2258The original stack mark for the XSUB. See C<dORIGMARK>.
2259
2260=item perl_alloc
2261
2262Allocates a new Perl interpreter. See L<perlembed>.
2263
2264=item perl_call_argv
2265
2266Performs a callback to the specified Perl sub. See L<perlcall>.
2267
ef50df4b 2268 I32 perl_call_argv (char* subname, I32 flags, char** argv)
cb1a09d0
AD
2269
2270=item perl_call_method
2271
2272Performs a callback to the specified Perl method. The blessed object must
2273be on the stack. See L<perlcall>.
2274
ef50df4b 2275 I32 perl_call_method (char* methname, I32 flags)
cb1a09d0
AD
2276
2277=item perl_call_pv
2278
2279Performs a callback to the specified Perl sub. See L<perlcall>.
2280
ef50df4b 2281 I32 perl_call_pv (char* subname, I32 flags)
cb1a09d0
AD
2282
2283=item perl_call_sv
2284
2285Performs a callback to the Perl sub whose name is in the SV. See
2286L<perlcall>.
2287
ef50df4b 2288 I32 perl_call_sv (SV* sv, I32 flags)
cb1a09d0
AD
2289
2290=item perl_construct
2291
2292Initializes a new Perl interpreter. See L<perlembed>.
2293
2294=item perl_destruct
2295
2296Shuts down a Perl interpreter. See L<perlembed>.
2297
2298=item perl_eval_sv
2299
2300Tells Perl to C<eval> the string in the SV.
2301
ef50df4b 2302 I32 perl_eval_sv (SV* sv, I32 flags)
cb1a09d0 2303
137443ea
PP
2304=item perl_eval_pv
2305
2306Tells Perl to C<eval> the given string and return an SV* result.
2307
ef50df4b 2308 SV* perl_eval_pv (char* p, I32 croak_on_error)
137443ea 2309
cb1a09d0
AD
2310=item perl_free
2311
2312Releases a Perl interpreter. See L<perlembed>.
2313
2314=item perl_get_av
2315
2316Returns the AV of the specified Perl array. If C<create> is set and the
2317Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2318set and the variable does not exist then NULL is returned.
cb1a09d0 2319
ef50df4b 2320 AV* perl_get_av (char* name, I32 create)
cb1a09d0
AD
2321
2322=item perl_get_cv
2323
2324Returns the CV of the specified Perl sub. If C<create> is set and the Perl
2325variable does not exist then it will be created. If C<create> is not
04343c6d 2326set and the variable does not exist then NULL is returned.
cb1a09d0 2327
ef50df4b 2328 CV* perl_get_cv (char* name, I32 create)
cb1a09d0
AD
2329
2330=item perl_get_hv
2331
2332Returns the HV of the specified Perl hash. If C<create> is set and the Perl
2333variable does not exist then it will be created. If C<create> is not
04343c6d 2334set and the variable does not exist then NULL is returned.
cb1a09d0 2335
ef50df4b 2336 HV* perl_get_hv (char* name, I32 create)
cb1a09d0
AD
2337
2338=item perl_get_sv
2339
2340Returns the SV of the specified Perl scalar. If C<create> is set and the
2341Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2342set and the variable does not exist then NULL is returned.
cb1a09d0 2343
ef50df4b 2344 SV* perl_get_sv (char* name, I32 create)
cb1a09d0
AD
2345
2346=item perl_parse
2347
2348Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2349
2350=item perl_require_pv
2351
2352Tells Perl to C<require> a module.
2353
ef50df4b 2354 void perl_require_pv (char* pv)
cb1a09d0
AD
2355
2356=item perl_run
2357
2358Tells a Perl interpreter to run. See L<perlembed>.
2359
2360=item POPi
2361
2362Pops an integer off the stack.
2363
e89caa19 2364 int POPi()
cb1a09d0
AD
2365
2366=item POPl
2367
2368Pops a long off the stack.
2369
e89caa19 2370 long POPl()
cb1a09d0
AD
2371
2372=item POPp
2373
2374Pops a string off the stack.
2375
e89caa19 2376 char* POPp()
cb1a09d0
AD
2377
2378=item POPn
2379
2380Pops a double off the stack.
2381
e89caa19 2382 double POPn()
cb1a09d0
AD
2383
2384=item POPs
2385
2386Pops an SV off the stack.
2387
e89caa19 2388 SV* POPs()
cb1a09d0
AD
2389
2390=item PUSHMARK
2391
2392Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2393
2394 PUSHMARK(p)
2395
2396=item PUSHi
2397
2398Push an integer onto the stack. The stack must have room for this element.
189b2af5 2399Handles 'set' magic. See C<XPUSHi>.
cb1a09d0 2400
e89caa19 2401 void PUSHi(int d)
cb1a09d0
AD
2402
2403=item PUSHn
2404
2405Push a double onto the stack. The stack must have room for this element.
189b2af5 2406Handles 'set' magic. See C<XPUSHn>.
cb1a09d0 2407
e89caa19 2408 void PUSHn(double d)
cb1a09d0
AD
2409
2410=item PUSHp
2411
2412Push a string onto the stack. The stack must have room for this element.
189b2af5
GS
2413The C<len> indicates the length of the string. Handles 'set' magic. See
2414C<XPUSHp>.
cb1a09d0 2415
e89caa19 2416 void PUSHp(char *c, int len )
cb1a09d0
AD
2417
2418=item PUSHs
2419
189b2af5
GS
2420Push an SV onto the stack. The stack must have room for this element. Does
2421not handle 'set' magic. See C<XPUSHs>.
cb1a09d0 2422
e89caa19
GA
2423 void PUSHs(sv)
2424
2425=item PUSHu
2426
2427Push an unsigned integer onto the stack. The stack must have room for
2428this element. See C<XPUSHu>.
2429
2430 void PUSHu(unsigned int d)
2431
cb1a09d0
AD
2432
2433=item PUTBACK
2434
2435Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2436See C<PUSHMARK> and L<perlcall> for other uses.
2437
2438 PUTBACK;
2439
2440=item Renew
2441
2442The XSUB-writer's interface to the C C<realloc> function.
2443
e89caa19 2444 void* Renew( void *ptr, int size, type )
cb1a09d0
AD
2445
2446=item Renewc
2447
2448The XSUB-writer's interface to the C C<realloc> function, with cast.
2449
e89caa19 2450 void* Renewc( void *ptr, int size, type, cast )
cb1a09d0
AD
2451
2452=item RETVAL
2453
2454Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
2455This is always the proper type for the XSUB.
2456See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
2457
2458=item safefree
2459
2460The XSUB-writer's interface to the C C<free> function.
2461
2462=item safemalloc
2463
2464The XSUB-writer's interface to the C C<malloc> function.
2465
2466=item saferealloc
2467
2468The XSUB-writer's interface to the C C<realloc> function.
2469
2470=item savepv
2471
2472Copy a string to a safe spot. This does not use an SV.
2473
ef50df4b 2474 char* savepv (char* sv)
cb1a09d0
AD
2475
2476=item savepvn
2477
2478Copy a string to a safe spot. The C<len> indicates number of bytes to
2479copy. This does not use an SV.
2480
ef50df4b 2481 char* savepvn (char* sv, I32 len)
cb1a09d0
AD
2482
2483=item SAVETMPS
2484
2485Opening bracket for temporaries on a callback. See C<FREETMPS> and
2486L<perlcall>.
2487
2488 SAVETMPS;
2489
2490=item SP
2491
2492Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2493C<SPAGAIN>.
2494
2495=item SPAGAIN
2496
54310121 2497Refetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
2498
2499 SPAGAIN;
2500
2501=item ST
2502
2503Used to access elements on the XSUB's stack.
2504
e89caa19 2505 SV* ST(int x)
cb1a09d0
AD
2506
2507=item strEQ
2508
2509Test two strings to see if they are equal. Returns true or false.
2510
e89caa19 2511 int strEQ( char *s1, char *s2 )
cb1a09d0
AD
2512
2513=item strGE
2514
2515Test two strings to see if the first, C<s1>, is greater than or equal to the
2516second, C<s2>. Returns true or false.
2517
e89caa19 2518 int strGE( char *s1, char *s2 )
cb1a09d0
AD
2519
2520=item strGT
2521
2522Test two strings to see if the first, C<s1>, is greater than the second,
2523C<s2>. Returns true or false.
2524
e89caa19 2525 int strGT( char *s1, char *s2 )
cb1a09d0
AD
2526
2527=item strLE
2528
2529Test two strings to see if the first, C<s1>, is less than or equal to the
2530second, C<s2>. Returns true or false.
2531
e89caa19 2532 int strLE( char *s1, char *s2 )
cb1a09d0
AD
2533
2534=item strLT
2535
2536Test two strings to see if the first, C<s1>, is less than the second,
2537C<s2>. Returns true or false.
2538
e89caa19 2539 int strLT( char *s1, char *s2 )
cb1a09d0
AD
2540
2541=item strNE
2542
2543Test two strings to see if they are different. Returns true or false.
2544
e89caa19 2545 int strNE( char *s1, char *s2 )
cb1a09d0
AD
2546
2547=item strnEQ
2548
2549Test two strings to see if they are equal. The C<len> parameter indicates
2550the number of bytes to compare. Returns true or false.
2551
e89caa19 2552 int strnEQ( char *s1, char *s2 )
cb1a09d0
AD
2553
2554=item strnNE
2555
2556Test two strings to see if they are different. The C<len> parameter
2557indicates the number of bytes to compare. Returns true or false.
2558
e89caa19 2559 int strnNE( char *s1, char *s2, int len )
cb1a09d0
AD
2560
2561=item sv_2mortal
2562
2563Marks an SV as mortal. The SV will be destroyed when the current context
2564ends.
2565
ef50df4b 2566 SV* sv_2mortal (SV* sv)
cb1a09d0
AD
2567
2568=item sv_bless
2569
2570Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
2571must be designated by its stash (see C<gv_stashpv()>). The reference count
2572of the SV is unaffected.
cb1a09d0 2573
ef50df4b 2574 SV* sv_bless (SV* sv, HV* stash)
cb1a09d0 2575
ef50df4b 2576=item sv_catpv
189b2af5 2577
ef50df4b
GS
2578Concatenates the string onto the end of the string which is in the SV.
2579Handles 'get' magic, but not 'set' magic. See C<sv_catpv_mg>.
189b2af5 2580
ef50df4b 2581 void sv_catpv (SV* sv, char* ptr)
189b2af5 2582
ef50df4b 2583=item sv_catpv_mg
cb1a09d0 2584
ef50df4b 2585Like C<sv_catpv>, but also handles 'set' magic.
cb1a09d0 2586
ef50df4b 2587 void sv_catpvn (SV* sv, char* ptr)
cb1a09d0
AD
2588
2589=item sv_catpvn
2590
2591Concatenates the string onto the end of the string which is in the SV. The
189b2af5 2592C<len> indicates number of bytes to copy. Handles 'get' magic, but not
ef50df4b 2593'set' magic. See C<sv_catpvn_mg>.
cb1a09d0 2594
ef50df4b
GS
2595 void sv_catpvn (SV* sv, char* ptr, STRLEN len)
2596
2597=item sv_catpvn_mg
2598
2599Like C<sv_catpvn>, but also handles 'set' magic.
2600
2601 void sv_catpvn_mg (SV* sv, char* ptr, STRLEN len)
cb1a09d0 2602
46fc3d4c
PP
2603=item sv_catpvf
2604
2605Processes its arguments like C<sprintf> and appends the formatted output
189b2af5
GS
2606to an SV. Handles 'get' magic, but not 'set' magic. C<SvSETMAGIC()> must
2607typically be called after calling this function to handle 'set' magic.
46fc3d4c 2608
ef50df4b
GS
2609 void sv_catpvf (SV* sv, const char* pat, ...)
2610
2611=item sv_catpvf_mg
2612
2613Like C<sv_catpvf>, but also handles 'set' magic.
2614
2615 void sv_catpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 2616
cb1a09d0
AD
2617=item sv_catsv
2618
5fb8527f 2619Concatenates the string from SV C<ssv> onto the end of the string in SV
ef50df4b
GS
2620C<dsv>. Handles 'get' magic, but not 'set' magic. See C<sv_catsv_mg>.
2621
2622 void sv_catsv (SV* dsv, SV* ssv)
2623
2624=item sv_catsv_mg
cb1a09d0 2625
ef50df4b
GS
2626Like C<sv_catsv>, but also handles 'set' magic.
2627
2628 void sv_catsv_mg (SV* dsv, SV* ssv)
cb1a09d0 2629
e89caa19
GA
2630=item sv_chop
2631
2632Efficient removal of characters from the beginning of the string
2633buffer. SvPOK(sv) must be true and the C<ptr> must be a pointer to
2634somewhere inside the string buffer. The C<ptr> becomes the first
2635character of the adjusted string.
2636
2637 void sv_chop(SV* sv, char *ptr)
2638
2639
5fb8527f
PP
2640=item sv_cmp
2641
2642Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2643string in C<sv1> is less than, equal to, or greater than the string in
2644C<sv2>.
2645
ef50df4b 2646 I32 sv_cmp (SV* sv1, SV* sv2)
5fb8527f 2647
cb1a09d0
AD
2648=item SvCUR
2649
2650Returns the length of the string which is in the SV. See C<SvLEN>.
2651
e89caa19 2652 int SvCUR (SV* sv)
cb1a09d0
AD
2653
2654=item SvCUR_set
2655
2656Set the length of the string which is in the SV. See C<SvCUR>.
2657
e89caa19 2658 void SvCUR_set (SV* sv, int val )
cb1a09d0 2659
5fb8527f
PP
2660=item sv_dec
2661
5f05dabc 2662Auto-decrement of the value in the SV.
5fb8527f 2663
ef50df4b 2664 void sv_dec (SV* sv)
5fb8527f 2665
e89caa19
GA
2666=item sv_derived_from
2667
2668Returns a boolean indicating whether the SV is a subclass of the
2669specified class.
2670
2671 int sv_derived_from(SV* sv, char* class)
2672
cb1a09d0
AD
2673=item SvEND
2674
2675Returns a pointer to the last character in the string which is in the SV.
2676See C<SvCUR>. Access the character as
2677
e89caa19 2678 char* SvEND(sv)
cb1a09d0 2679
5fb8527f
PP
2680=item sv_eq
2681
2682Returns a boolean indicating whether the strings in the two SVs are
2683identical.
2684
ef50df4b 2685 I32 sv_eq (SV* sv1, SV* sv2)
5fb8527f 2686
189b2af5
GS
2687=item SvGETMAGIC
2688
2689Invokes C<mg_get> on an SV if it has 'get' magic. This macro evaluates
2690its argument more than once.
2691
2692 void SvGETMAGIC( SV *sv )
2693
cb1a09d0
AD
2694=item SvGROW
2695
e89caa19
GA
2696Expands the character buffer in the SV so that it has room for the
2697indicated number of bytes (remember to reserve space for an extra
2698trailing NUL character). Calls C<sv_grow> to perform the expansion if
2699necessary. Returns a pointer to the character buffer.
cb1a09d0 2700
e89caa19 2701 char* SvGROW( SV* sv, int len )
cb1a09d0 2702
5fb8527f
PP
2703=item sv_grow
2704
2705Expands the character buffer in the SV. This will use C<sv_unref> and will
2706upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2707Use C<SvGROW>.
2708
2709=item sv_inc
2710
07fa94a1 2711Auto-increment of the value in the SV.
5fb8527f 2712
ef50df4b 2713 void sv_inc (SV* sv)
5fb8527f 2714
e89caa19
GA
2715=item sv_insert
2716
2717Inserts a string at the specified offset/length within the SV.
2718Similar to the Perl substr() function.
2719
2720 void sv_insert(SV *sv, STRLEN offset, STRLEN len,
2721 char *str, STRLEN strlen)
2722
cb1a09d0
AD
2723=item SvIOK
2724
2725Returns a boolean indicating whether the SV contains an integer.
2726
e89caa19 2727 int SvIOK (SV* SV)
cb1a09d0
AD
2728
2729=item SvIOK_off
2730
2731Unsets the IV status of an SV.
2732
e89caa19 2733 void SvIOK_off (SV* sv)
cb1a09d0
AD
2734
2735=item SvIOK_on
2736
2737Tells an SV that it is an integer.
2738
e89caa19 2739 void SvIOK_on (SV* sv)
cb1a09d0 2740
5fb8527f
PP
2741=item SvIOK_only
2742
2743Tells an SV that it is an integer and disables all other OK bits.
2744
e89caa19 2745 void SvIOK_only (SV* sv)
5fb8527f 2746
cb1a09d0
AD
2747=item SvIOKp
2748
2749Returns a boolean indicating whether the SV contains an integer. Checks the
2750B<private> setting. Use C<SvIOK>.
2751
e89caa19 2752 int SvIOKp (SV* SV)
cb1a09d0
AD
2753
2754=item sv_isa
2755
2756Returns a boolean indicating whether the SV is blessed into the specified
2757class. This does not know how to check for subtype, so it doesn't work in
2758an inheritance relationship.
2759
ef50df4b 2760 int sv_isa (SV* sv, char* name)
cb1a09d0 2761
cb1a09d0
AD
2762=item sv_isobject
2763
2764Returns a boolean indicating whether the SV is an RV pointing to a blessed
2765object. If the SV is not an RV, or if the object is not blessed, then this
2766will return false.
2767
ef50df4b 2768 int sv_isobject (SV* sv)
cb1a09d0 2769
e89caa19
GA
2770=item SvIV
2771
2772Returns the integer which is in the SV.
2773
2774 int SvIV (SV* sv)
2775
cb1a09d0
AD
2776=item SvIVX
2777
2778Returns the integer which is stored in the SV.
2779
e89caa19 2780 int SvIVX (SV* sv)
cb1a09d0
AD
2781
2782=item SvLEN
2783
2784Returns the size of the string buffer in the SV. See C<SvCUR>.
2785
e89caa19 2786 int SvLEN (SV* sv)
cb1a09d0 2787
5fb8527f
PP
2788=item sv_len
2789
2790Returns the length of the string in the SV. Use C<SvCUR>.
2791
ef50df4b 2792 STRLEN sv_len (SV* sv)
5fb8527f 2793
cb1a09d0
AD
2794=item sv_magic
2795
2796Adds magic to an SV.
2797
ef50df4b 2798 void sv_magic (SV* sv, SV* obj, int how, char* name, I32 namlen)
cb1a09d0
AD
2799
2800=item sv_mortalcopy
2801
2802Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 2803as mortal.
cb1a09d0 2804
ef50df4b 2805 SV* sv_mortalcopy (SV* oldsv)
cb1a09d0 2806
cb1a09d0
AD
2807=item sv_newmortal
2808
5f05dabc 2809Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0 2810
ef50df4b 2811 SV* sv_newmortal (void)
cb1a09d0 2812
cb1a09d0
AD
2813=item SvNIOK
2814
2815Returns a boolean indicating whether the SV contains a number, integer or
2816double.
2817
e89caa19 2818 int SvNIOK (SV* SV)
cb1a09d0
AD
2819
2820=item SvNIOK_off
2821
2822Unsets the NV/IV status of an SV.
2823
e89caa19 2824 void SvNIOK_off (SV* sv)
cb1a09d0
AD
2825
2826=item SvNIOKp
2827
2828Returns a boolean indicating whether the SV contains a number, integer or
2829double. Checks the B<private> setting. Use C<SvNIOK>.
2830
e89caa19
GA
2831 int SvNIOKp (SV* SV)
2832
2833=item sv_no
2834
2835This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
cb1a09d0
AD
2836
2837=item SvNOK
2838
2839Returns a boolean indicating whether the SV contains a double.
2840
e89caa19 2841 int SvNOK (SV* SV)
cb1a09d0
AD
2842
2843=item SvNOK_off
2844
2845Unsets the NV status of an SV.
2846
e89caa19 2847 void SvNOK_off (SV* sv)
cb1a09d0
AD
2848
2849=item SvNOK_on
2850
2851Tells an SV that it is a double.
2852
e89caa19 2853 void SvNOK_on (SV* sv)
cb1a09d0 2854
5fb8527f
PP
2855=item SvNOK_only
2856
2857Tells an SV that it is a double and disables all other OK bits.
2858
e89caa19 2859 void SvNOK_only (SV* sv)
5fb8527f 2860
cb1a09d0
AD
2861=item SvNOKp
2862
2863Returns a boolean indicating whether the SV contains a double. Checks the
2864B<private> setting. Use C<SvNOK>.
2865
e89caa19 2866 int SvNOKp (SV* SV)
cb1a09d0
AD
2867
2868=item SvNV
2869
2870Returns the double which is stored in the SV.
2871
e89caa19 2872 double SvNV (SV* sv)
cb1a09d0
AD
2873
2874=item SvNVX
2875
2876Returns the double which is stored in the SV.
2877
e89caa19
GA
2878 double SvNVX (SV* sv)
2879
2880=item SvOK
2881
2882Returns a boolean indicating whether the value is an SV.
2883
2884 int SvOK (SV* sv)
2885
2886=item SvOOK
2887
2888Returns a boolean indicating whether the SvIVX is a valid offset value
2889for the SvPVX. This hack is used internally to speed up removal of
2890characters from the beginning of a SvPV. When SvOOK is true, then the
2891start of the allocated string buffer is really (SvPVX - SvIVX).
2892
2893 int SvOOK(Sv* sv)
cb1a09d0
AD
2894
2895=item SvPOK
2896
2897Returns a boolean indicating whether the SV contains a character string.
2898
e89caa19 2899 int SvPOK (SV* SV)
cb1a09d0
AD
2900
2901=item SvPOK_off
2902
2903Unsets the PV status of an SV.
2904
e89caa19 2905 void SvPOK_off (SV* sv)
cb1a09d0
AD
2906
2907=item SvPOK_on
2908
2909Tells an SV that it is a string.
2910
e89caa19 2911 void SvPOK_on (SV* sv)
cb1a09d0 2912
5fb8527f
PP
2913=item SvPOK_only
2914
2915Tells an SV that it is a string and disables all other OK bits.
2916
e89caa19 2917 void SvPOK_only (SV* sv)
5fb8527f 2918
cb1a09d0
AD
2919=item SvPOKp
2920
2921Returns a boolean indicating whether the SV contains a character string.
2922Checks the B<private> setting. Use C<SvPOK>.
2923
e89caa19 2924 int SvPOKp (SV* SV)
cb1a09d0
AD
2925
2926=item SvPV
2927
2928Returns a pointer to the string in the SV, or a stringified form of the SV
2929if the SV does not contain a string. If C<len> is C<na> then Perl will
189b2af5 2930handle the length on its own. Handles 'get' magic.
cb1a09d0 2931
e89caa19
GA
2932 char* SvPV (SV* sv, int len )
2933
2934=item SvPV_force
2935
2936Like <SvPV> but will force the SV into becoming a string (SvPOK). You
2937want force if you are going to update the SvPVX directly.
2938
2939 char* SvPV_force(SV* sv, int len)
2940
cb1a09d0
AD
2941
2942=item SvPVX
2943
2944Returns a pointer to the string in the SV. The SV must contain a string.
2945
e89caa19 2946 char* SvPVX (SV* sv)
cb1a09d0
AD
2947
2948=item SvREFCNT
2949
5f05dabc 2950Returns the value of the object's reference count.
cb1a09d0 2951
e89caa19 2952 int SvREFCNT (SV* sv)
cb1a09d0
AD
2953
2954=item SvREFCNT_dec
2955
5f05dabc 2956Decrements the reference count of the given SV.
cb1a09d0 2957
e89caa19 2958 void SvREFCNT_dec (SV* sv)
cb1a09d0
AD
2959
2960=item SvREFCNT_inc
2961
5f05dabc 2962Increments the reference count of the given SV.
cb1a09d0 2963
e89caa19 2964 void SvREFCNT_inc (SV* sv)
cb1a09d0
AD
2965
2966=item SvROK
2967
2968Tests if the SV is an RV.
2969
e89caa19 2970 int SvROK (SV* sv)
cb1a09d0
AD
2971
2972=item SvROK_off
2973
2974Unsets the RV status of an SV.
2975
e89caa19 2976 void SvROK_off (SV* sv)
cb1a09d0
AD
2977
2978=item SvROK_on
2979
2980Tells an SV that it is an RV.
2981
e89caa19 2982 void SvROK_on (SV* sv)
cb1a09d0
AD
2983
2984=item SvRV
2985
2986Dereferences an RV to return the SV.
2987
ef50df4b 2988 SV* SvRV (SV* sv)
cb1a09d0 2989
189b2af5
GS
2990=item SvSETMAGIC
2991
2992Invokes C<mg_set> on an SV if it has 'set' magic. This macro evaluates
2993its argument more than once.
2994
2995 void SvSETMAGIC( SV *sv )
2996
ef50df4b 2997=item sv_setiv
189b2af5 2998
ef50df4b
GS
2999Copies an integer into the given SV. Does not handle 'set' magic.
3000See C<sv_setiv_mg>.
189b2af5 3001
ef50df4b 3002 void sv_setiv (SV* sv, IV num)
189b2af5 3003
ef50df4b 3004=item sv_setiv_mg
189b2af5 3005
ef50df4b 3006Like C<sv_setiv>, but also handles 'set' magic.
189b2af5 3007
ef50df4b 3008 void sv_setiv_mg (SV* sv, IV num)
189b2af5 3009
ef50df4b 3010=item sv_setnv
189b2af5 3011
ef50df4b
GS
3012Copies a double into the given SV. Does not handle 'set' magic.
3013See C<sv_setnv_mg>.
189b2af5 3014
ef50df4b 3015 void sv_setnv (SV* sv, double num)
189b2af5 3016
ef50df4b 3017=item sv_setnv_mg
189b2af5 3018
ef50df4b 3019Like C<sv_setnv>, but also handles 'set' magic.
189b2af5 3020
ef50df4b 3021 void sv_setnv_mg (SV* sv, double num)
189b2af5 3022
ef50df4b 3023=item sv_setpv
189b2af5 3024
ef50df4b
GS
3025Copies a string into an SV. The string must be null-terminated.
3026Does not handle 'set' magic. See C<sv_setpv_mg>.
189b2af5 3027
ef50df4b 3028 void sv_setpv (SV* sv, char* ptr)
189b2af5 3029
ef50df4b 3030=item sv_setpv_mg
189b2af5 3031
ef50df4b 3032Like C<sv_setpv>, but also handles 'set' magic.
189b2af5 3033
ef50df4b 3034 void sv_setpv_mg (SV* sv, char* ptr)
189b2af5 3035
ef50df4b 3036=item sv_setpviv
cb1a09d0 3037
ef50df4b
GS
3038Copies an integer into the given SV, also updating its string value.
3039Does not handle 'set' magic. See C<sv_setpviv_mg>.
cb1a09d0 3040
ef50df4b 3041 void sv_setpviv (SV* sv, IV num)
cb1a09d0 3042
ef50df4b 3043=item sv_setpviv_mg
cb1a09d0 3044
ef50df4b 3045Like C<sv_setpviv>, but also handles 'set' magic.
cb1a09d0 3046
ef50df4b 3047 void sv_setpviv_mg (SV* sv, IV num)
cb1a09d0 3048
ef50df4b 3049=item sv_setpvn
cb1a09d0 3050
ef50df4b
GS
3051Copies a string into an SV. The C<len> parameter indicates the number of
3052bytes to be copied. Does not handle 'set' magic. See C<sv_setpvn_mg>.
cb1a09d0 3053
ef50df4b 3054 void sv_setpvn (SV* sv, char* ptr, STRLEN len)
cb1a09d0 3055
ef50df4b 3056=item sv_setpvn_mg
189b2af5 3057
ef50df4b 3058Like C<sv_setpvn>, but also handles 'set' magic.
189b2af5 3059
ef50df4b 3060 void sv_setpvn_mg (SV* sv, char* ptr, STRLEN len)
189b2af5 3061
ef50df4b 3062=item sv_setpvf
cb1a09d0 3063
ef50df4b
GS
3064Processes its arguments like C<sprintf> and sets an SV to the formatted
3065output. Does not handle 'set' magic. See C<sv_setpvf_mg>.
cb1a09d0 3066
ef50df4b 3067 void sv_setpvf (SV* sv, const char* pat, ...)
cb1a09d0 3068
ef50df4b 3069=item sv_setpvf_mg
46fc3d4c 3070
ef50df4b 3071Like C<sv_setpvf>, but also handles 'set' magic.
46fc3d4c 3072
ef50df4b 3073 void sv_setpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 3074
cb1a09d0
AD
3075=item sv_setref_iv
3076
5fb8527f
PP
3077Copies an integer into a new SV, optionally blessing the SV. The C<rv>
3078argument will be upgraded to an RV. That RV will be modified to point to
3079the new SV. The C<classname> argument indicates the package for the
3080blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3081will be returned and will have a reference count of 1.
cb1a09d0 3082
ef50df4b 3083 SV* sv_setref_iv (SV *rv, char *classname, IV iv)
cb1a09d0
AD
3084
3085=item sv_setref_nv
3086
5fb8527f
PP
3087Copies a double into a new SV, optionally blessing the SV. The C<rv>
3088argument will be upgraded to an RV. That RV will be modified to point to
3089the new SV. The C<classname> argument indicates the package for the
3090blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3091will be returned and will have a reference count of 1.
cb1a09d0 3092
ef50df4b 3093 SV* sv_setref_nv (SV *rv, char *classname, double nv)
cb1a09d0
AD
3094
3095=item sv_setref_pv
3096
5fb8527f
PP
3097Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
3098argument will be upgraded to an RV. That RV will be modified to point to
3099the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
3100into the SV. The C<classname> argument indicates the package for the
3101blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3102will be returned and will have a reference count of 1.
cb1a09d0 3103
ef50df4b 3104 SV* sv_setref_pv (SV *rv, char *classname, void* pv)
cb1a09d0
AD
3105
3106Do not use with integral Perl types such as HV, AV, SV, CV, because those
3107objects will become corrupted by the pointer copy process.
3108
3109Note that C<sv_setref_pvn> copies the string while this copies the pointer.
3110
3111=item sv_setref_pvn
3112
5fb8527f
PP
3113Copies a string into a new SV, optionally blessing the SV. The length of the
3114string must be specified with C<n>. The C<rv> argument will be upgraded to
3115an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
3116argument indicates the package for the blessing. Set C<classname> to
3117C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 3118a reference count of 1.
cb1a09d0 3119
ef50df4b 3120 SV* sv_setref_pvn (SV *rv, char *classname, char* pv, I32 n)
cb1a09d0
AD
3121
3122Note that C<sv_setref_pv> copies the pointer while this copies the string.
3123
189b2af5
GS
3124=item SvSetSV
3125
3126Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
3127more than once.
3128
3129 void SvSetSV (SV* dsv, SV* ssv)
3130
3131=item SvSetSV_nosteal
3132
3133Calls a non-destructive version of C<sv_setsv> if dsv is not the same as ssv.
3134May evaluate arguments more than once.
3135
3136 void SvSetSV_nosteal (SV* dsv, SV* ssv)
3137
cb1a09d0
AD
3138=item sv_setsv
3139
3140Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
189b2af5 3141The source SV may be destroyed if it is mortal. Does not handle 'set' magic.
ef50df4b
GS
3142See the macro forms C<SvSetSV>, C<SvSetSV_nosteal> and C<sv_setsv_mg>.
3143
3144 void sv_setsv (SV* dsv, SV* ssv)
3145
3146=item sv_setsv_mg
3147
3148Like C<sv_setsv>, but also handles 'set' magic.
cb1a09d0 3149
ef50df4b 3150 void sv_setsv_mg (SV* dsv, SV* ssv)
cb1a09d0 3151
189b2af5
GS
3152=item sv_setuv
3153
3154Copies an unsigned integer into the given SV. Does not handle 'set' magic.
ef50df4b 3155See C<sv_setuv_mg>.
189b2af5 3156
ef50df4b
GS
3157 void sv_setuv (SV* sv, UV num)
3158
3159=item sv_setuv_mg
3160
3161Like C<sv_setuv>, but also handles 'set' magic.
3162
3163 void sv_setuv_mg (SV* sv, UV num)
189b2af5 3164
cb1a09d0
AD
3165=item SvSTASH
3166
3167Returns the stash of the SV.
3168
e89caa19
GA
3169 HV* SvSTASH (SV* sv)
3170
3171=item SvTAINT
3172
3173Taints an SV if tainting is enabled
3174
3175 void SvTAINT (SV* sv)
3176
3177=item SvTAINTED
3178
3179Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.
3180
3181 int SvTAINTED (SV* sv)
3182
3183=item SvTAINTED_off
3184
3185Untaints an SV. Be I<very> careful with this routine, as it short-circuits
3186some of Perl's fundamental security features. XS module authors should
3187not use this function unless they fully understand all the implications
3188of unconditionally untainting the value. Untainting should be done in
3189the standard perl fashion, via a carefully crafted regexp, rather than
3190directly untainting variables.
3191
3192 void SvTAINTED_off (SV* sv)
3193
3194=item SvTAINTED_on
3195
3196Marks an SV as tainted.
3197
3198 void SvTAINTED_on (SV* sv)
cb1a09d0
AD
3199
3200=item SVt_IV
3201
3202Integer type flag for scalars. See C<svtype>.
3203
3204=item SVt_PV
3205
3206Pointer type flag for scalars. See C<svtype>.
3207
3208=item SVt_PVAV
3209
3210Type flag for arrays. See C<svtype>.
3211
3212=item SVt_PVCV
3213
3214Type flag for code refs. See C<svtype>.
3215
3216=item SVt_PVHV
3217
3218Type flag for hashes. See C<svtype>.
3219
3220=item SVt_PVMG
3221
3222Type flag for blessed scalars. See C<svtype>.
3223
3224=item SVt_NV
3225
3226Double type flag for scalars. See C<svtype>.
3227
3228=item SvTRUE
3229
3230Returns a boolean indicating whether Perl would evaluate the SV as true or
189b2af5 3231false, defined or undefined. Does not handle 'get' magic.
cb1a09d0 3232
e89caa19 3233 int SvTRUE (SV* sv)
cb1a09d0
AD
3234
3235=item SvTYPE
3236
3237Returns the type of the SV. See C<svtype>.
3238
3239 svtype SvTYPE (SV* sv)
3240
3241=item svtype
3242
3243An enum of flags for Perl types. These are found in the file B<sv.h> in the
3244C<svtype> enum. Test these flags with the C<SvTYPE> macro.
3245
cb1a09d0
AD
3246=item sv_undef
3247
3248This is the C<undef> SV. Always refer to this as C<&sv_undef>.
3249
5fb8527f
PP
3250=item sv_unref
3251
07fa94a1
JO
3252Unsets the RV status of the SV, and decrements the reference count of
3253whatever was being referenced by the RV. This can almost be thought of
3254as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f 3255
ef50df4b 3256 void sv_unref (SV* sv)
189b2af5 3257
e89caa19
GA
3258=item SvUPGRADE
3259
3260Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
3261the upgrade if necessary. See C<svtype>.
3262
3263 bool SvUPGRADE (SV* sv, svtype mt)
3264
3265=item sv_upgrade
3266
3267Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
3268
cb1a09d0
AD
3269=item sv_usepvn
3270
3271Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
3272stored inside the SV but sv_usepvn allows the SV to use an outside string.
3273The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
3274string length, C<len>, must be supplied. This function will realloc the
3275memory pointed to by C<ptr>, so that pointer should not be freed or used by
189b2af5 3276the programmer after giving it to sv_usepvn. Does not handle 'set' magic.
ef50df4b
GS
3277See C<sv_usepvn_mg>.
3278
3279 void sv_usepvn (SV* sv, char* ptr, STRLEN len)
3280
3281=item sv_usepvn_mg
3282
3283Like C<sv_usepvn>, but also handles 'set' magic.
cb1a09d0 3284
ef50df4b 3285 void sv_usepvn_mg (SV* sv, char* ptr, STRLEN len)
cb1a09d0 3286
e89caa19
GA
3287=item SvUV
3288
3289Returns the unsigned integer which is in the SV.
3290
3291 UV SvUV(SV* sv)
3292
3293=item SvUVX
3294
3295Returns the unsigned integer which is stored in the SV.
3296
3297 UV SvUVX(SV* sv)
3298
cb1a09d0
AD
3299=item sv_yes
3300
3301This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
3302
3303=item THIS
3304
3305Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
3306This is always the proper type for the C++ object. See C<CLASS> and
5fb8527f 3307L<perlxs/"Using XS With C++">.
cb1a09d0
AD
3308
3309=item toLOWER
3310
3311Converts the specified character to lowercase.
3312
e89caa19 3313 int toLOWER (char c)
cb1a09d0
AD
3314
3315=item toUPPER
3316
3317Converts the specified character to uppercase.
3318
e89caa19 3319 int toUPPER (char c)
cb1a09d0
AD
3320
3321=item warn
3322
3323This is the XSUB-writer's interface to Perl's C<warn> function. Use this
3324function the same way you use the C C<printf> function. See C<croak()>.
3325
3326=item XPUSHi
3327
189b2af5
GS
3328Push an integer onto the stack, extending the stack if necessary. Handles
3329'set' magic. See C<PUSHi>.
cb1a09d0
AD
3330
3331 XPUSHi(int d)
3332
3333=item XPUSHn
3334
189b2af5
GS
3335Push a double onto the stack, extending the stack if necessary. Handles 'set'
3336magic. See C<PUSHn>.
cb1a09d0
AD
3337
3338 XPUSHn(double d)
3339
3340=item XPUSHp
3341
3342Push a string onto the stack, extending the stack if necessary. The C<len>
189b2af5 3343indicates the length of the string. Handles 'set' magic. See C<PUSHp>.
cb1a09d0
AD
3344
3345 XPUSHp(char *c, int len)
3346
3347=item XPUSHs
3348
189b2af5
GS
3349Push an SV onto the stack, extending the stack if necessary. Does not
3350handle 'set' magic. See C<PUSHs>.
cb1a09d0
AD
3351
3352 XPUSHs(sv)
3353
e89caa19
GA
3354=item XPUSHu
3355
3356Push an unsigned integer onto the stack, extending the stack if
3357necessary. See C<PUSHu>.
3358
5fb8527f
PP
3359=item XS
3360
3361Macro to declare an XSUB and its C parameter list. This is handled by
3362C<xsubpp>.
3363
cb1a09d0
AD
3364=item XSRETURN
3365
3366Return from XSUB, indicating number of items on the stack. This is usually
3367handled by C<xsubpp>.
3368
ef50df4b 3369 XSRETURN(int x)
cb1a09d0
AD
3370
3371=item XSRETURN_EMPTY
3372
5fb8527f 3373Return an empty list from an XSUB immediately.
cb1a09d0
AD
3374
3375 XSRETURN_EMPTY;
3376
5fb8527f
PP
3377=item XSRETURN_IV
3378
3379Return an integer from an XSUB immediately. Uses C<XST_mIV>.
3380
ef50df4b 3381 XSRETURN_IV(IV v)
5fb8527f 3382
cb1a09d0
AD
3383=item XSRETURN_NO
3384
5fb8527f 3385Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
cb1a09d0
AD
3386
3387 XSRETURN_NO;
3388
5fb8527f
PP
3389=item XSRETURN_NV
3390
3391Return an double from an XSUB immediately. Uses C<XST_mNV>.
3392
ef50df4b 3393 XSRETURN_NV(NV v)
5fb8527f
PP
3394
3395=item XSRETURN_PV
3396
3397Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
3398
ef50df4b 3399 XSRETURN_PV(char *v)
5fb8527f 3400
cb1a09d0
AD
3401=item XSRETURN_UNDEF
3402
5fb8527f 3403Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
cb1a09d0
AD
3404
3405 XSRETURN_UNDEF;
3406
3407=item XSRETURN_YES
3408
5fb8527f 3409Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
cb1a09d0
AD
3410
3411 XSRETURN_YES;
3412
5fb8527f
PP
3413=item XST_mIV
3414
3415Place an integer into the specified position C<i> on the stack. The value is
3416stored in a new mortal SV.
3417
ef50df4b 3418 XST_mIV( int i, IV v )
5fb8527f
PP
3419
3420=item XST_mNV
3421
3422Place a double into the specified position C<i> on the stack. The value is
3423stored in a new mortal SV.
3424
ef50df4b 3425 XST_mNV( int i, NV v )
5fb8527f
PP
3426
3427=item XST_mNO
3428
3429Place C<&sv_no> into the specified position C<i> on the stack.
3430
ef50df4b 3431 XST_mNO( int i )
5fb8527f
PP
3432
3433=item XST_mPV
3434
3435Place a copy of a string into the specified position C<i> on the stack. The
3436value is stored in a new mortal SV.
3437
ef50df4b 3438 XST_mPV( int i, char *v )
5fb8527f
PP
3439
3440=item XST_mUNDEF
3441
3442Place C<&sv_undef> into the specified position C<i> on the stack.
3443
ef50df4b 3444 XST_mUNDEF( int i )
5fb8527f
PP
3445
3446=item XST_mYES
3447
3448Place C<&sv_yes> into the specified position C<i> on the stack.
3449
ef50df4b 3450 XST_mYES( int i )
5fb8527f
PP
3451
3452=item XS_VERSION
3453
3454The version identifier for an XS module. This is usually handled
3455automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
3456
3457=item XS_VERSION_BOOTCHECK
3458
3459Macro to verify that a PM module's $VERSION variable matches the XS module's
3460C<XS_VERSION> variable. This is usually handled automatically by
3461C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
3462
cb1a09d0
AD
3463=item Zero
3464
3465The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
3466destination, C<n> is the number of items, and C<t> is the type.
3467
e89caa19 3468 void Zero( d, n, t )
cb1a09d0
AD
3469
3470=back
3471
9cecd9f2 3472=head1 AUTHORS
cb1a09d0 3473
9cecd9f2
GA
3474Until May 1997, this document was maintained by Jeff Okamoto
3475<okamoto@corp.hp.com>. It is now maintained as part of Perl itself.
cb1a09d0
AD
3476
3477With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
3478Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
189b2af5
GS
3479Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
3480Stephen McCamant, and Gurusamy Sarathy.
cb1a09d0 3481
9cecd9f2 3482API Listing originally by Dean Roehrich <roehrich@cray.com>.