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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
1091 EXTEND(sp, num);
1092
1093where C<sp> is the stack pointer, and C<num> is the number of elements the
1094stack should be extended by.
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
1147 PUSHMARK()
1148 PUTBACK
1149 SPAGAIN
1150 ENTER
1151 SAVETMPS
1152 FREETMPS
1153 LEAVE
1154 XPUSH*()
cb1a09d0 1155 POP*()
a0d0e21e 1156
5f05dabc
PP
1157For a detailed description of calling conventions from C to Perl,
1158consult L<perlcall>.
a0d0e21e 1159
5f05dabc 1160=head2 Memory Allocation
a0d0e21e 1161
5f05dabc
PP
1162It is suggested that you use the version of malloc that is distributed
1163with Perl. It keeps pools of various sizes of unallocated memory in
07fa94a1
JO
1164order to satisfy allocation requests more quickly. However, on some
1165platforms, it may cause spurious malloc or free errors.
d1b91892
AD
1166
1167 New(x, pointer, number, type);
1168 Newc(x, pointer, number, type, cast);
1169 Newz(x, pointer, number, type);
1170
07fa94a1 1171These three macros are used to initially allocate memory.
5f05dabc
PP
1172
1173The first argument C<x> was a "magic cookie" that was used to keep track
1174of who called the macro, to help when debugging memory problems. However,
07fa94a1
JO
1175the current code makes no use of this feature (most Perl developers now
1176use run-time memory checkers), so this argument can be any number.
5f05dabc
PP
1177
1178The second argument C<pointer> should be the name of a variable that will
1179point to the newly allocated memory.
d1b91892 1180
d1b91892
AD
1181The third and fourth arguments C<number> and C<type> specify how many of
1182the specified type of data structure should be allocated. The argument
1183C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
1184should be used if the C<pointer> argument is different from the C<type>
1185argument.
1186
1187Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
1188to zero out all the newly allocated memory.
1189
1190 Renew(pointer, number, type);
1191 Renewc(pointer, number, type, cast);
1192 Safefree(pointer)
1193
1194These three macros are used to change a memory buffer size or to free a
1195piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
1196match those of C<New> and C<Newc> with the exception of not needing the
1197"magic cookie" argument.
1198
1199 Move(source, dest, number, type);
1200 Copy(source, dest, number, type);
1201 Zero(dest, number, type);
1202
1203These three macros are used to move, copy, or zero out previously allocated
1204memory. The C<source> and C<dest> arguments point to the source and
1205destination starting points. Perl will move, copy, or zero out C<number>
1206instances of the size of the C<type> data structure (using the C<sizeof>
1207function).
a0d0e21e 1208
5f05dabc 1209=head2 PerlIO
ce3d39e2 1210
5f05dabc
PP
1211The most recent development releases of Perl has been experimenting with
1212removing Perl's dependency on the "normal" standard I/O suite and allowing
1213other stdio implementations to be used. This involves creating a new
1214abstraction layer that then calls whichever implementation of stdio Perl
68dc0745 1215was compiled with. All XSUBs should now use the functions in the PerlIO
5f05dabc
PP
1216abstraction layer and not make any assumptions about what kind of stdio
1217is being used.
1218
1219For a complete description of the PerlIO abstraction, consult L<perlapio>.
1220
8ebc5c01 1221=head2 Putting a C value on Perl stack
ce3d39e2
IZ
1222
1223A lot of opcodes (this is an elementary operation in the internal perl
1224stack machine) put an SV* on the stack. However, as an optimization
1225the corresponding SV is (usually) not recreated each time. The opcodes
1226reuse specially assigned SVs (I<target>s) which are (as a corollary)
1227not constantly freed/created.
1228
0a753a76 1229Each of the targets is created only once (but see
ce3d39e2
IZ
1230L<Scratchpads and recursion> below), and when an opcode needs to put
1231an integer, a double, or a string on stack, it just sets the
1232corresponding parts of its I<target> and puts the I<target> on stack.
1233
1234The macro to put this target on stack is C<PUSHTARG>, and it is
1235directly used in some opcodes, as well as indirectly in zillions of
1236others, which use it via C<(X)PUSH[pni]>.
1237
8ebc5c01 1238=head2 Scratchpads
ce3d39e2 1239
54310121 1240The question remains on when the SVs which are I<target>s for opcodes
5f05dabc
PP
1241are created. The answer is that they are created when the current unit --
1242a subroutine or a file (for opcodes for statements outside of
1243subroutines) -- is compiled. During this time a special anonymous Perl
ce3d39e2
IZ
1244array is created, which is called a scratchpad for the current
1245unit.
1246
54310121 1247A scratchpad keeps SVs which are lexicals for the current unit and are
ce3d39e2
IZ
1248targets for opcodes. One can deduce that an SV lives on a scratchpad
1249by looking on its flags: lexicals have C<SVs_PADMY> set, and
1250I<target>s have C<SVs_PADTMP> set.
1251
54310121
PP
1252The correspondence between OPs and I<target>s is not 1-to-1. Different
1253OPs in the compile tree of the unit can use the same target, if this
ce3d39e2
IZ
1254would not conflict with the expected life of the temporary.
1255
2ae324a7 1256=head2 Scratchpads and recursion
ce3d39e2
IZ
1257
1258In fact it is not 100% true that a compiled unit contains a pointer to
1259the scratchpad AV. In fact it contains a pointer to an AV of
1260(initially) one element, and this element is the scratchpad AV. Why do
1261we need an extra level of indirection?
1262
1263The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1264these can create several execution pointers going into the same
1265subroutine. For the subroutine-child not write over the temporaries
1266for the subroutine-parent (lifespan of which covers the call to the
1267child), the parent and the child should have different
1268scratchpads. (I<And> the lexicals should be separate anyway!)
1269
5f05dabc
PP
1270So each subroutine is born with an array of scratchpads (of length 1).
1271On each entry to the subroutine it is checked that the current
ce3d39e2
IZ
1272depth of the recursion is not more than the length of this array, and
1273if it is, new scratchpad is created and pushed into the array.
1274
1275The I<target>s on this scratchpad are C<undef>s, but they are already
1276marked with correct flags.
1277
0a753a76
PP
1278=head1 Compiled code
1279
1280=head2 Code tree
1281
1282Here we describe the internal form your code is converted to by
1283Perl. Start with a simple example:
1284
1285 $a = $b + $c;
1286
1287This is converted to a tree similar to this one:
1288
1289 assign-to
1290 / \
1291 + $a
1292 / \
1293 $b $c
1294
1295(but slightly more complicated). This tree reflect the way Perl
1296parsed your code, but has nothing to do with the execution order.
1297There is an additional "thread" going through the nodes of the tree
1298which shows the order of execution of the nodes. In our simplified
1299example above it looks like:
1300
1301 $b ---> $c ---> + ---> $a ---> assign-to
1302
1303But with the actual compile tree for C<$a = $b + $c> it is different:
1304some nodes I<optimized away>. As a corollary, though the actual tree
1305contains more nodes than our simplified example, the execution order
1306is the same as in our example.
1307
1308=head2 Examining the tree
1309
1310If you have your perl compiled for debugging (usually done with C<-D
1311optimize=-g> on C<Configure> command line), you may examine the
1312compiled tree by specifying C<-Dx> on the Perl command line. The
1313output takes several lines per node, and for C<$b+$c> it looks like
1314this:
1315
1316 5 TYPE = add ===> 6
1317 TARG = 1
1318 FLAGS = (SCALAR,KIDS)
1319 {
1320 TYPE = null ===> (4)
1321 (was rv2sv)
1322 FLAGS = (SCALAR,KIDS)
1323 {
1324 3 TYPE = gvsv ===> 4
1325 FLAGS = (SCALAR)
1326 GV = main::b
1327 }
1328 }
1329 {
1330 TYPE = null ===> (5)
1331 (was rv2sv)
1332 FLAGS = (SCALAR,KIDS)
1333 {
1334 4 TYPE = gvsv ===> 5
1335 FLAGS = (SCALAR)
1336 GV = main::c
1337 }
1338 }
1339
1340This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1341not optimized away (one per number in the left column). The immediate
1342children of the given node correspond to C<{}> pairs on the same level
1343of indentation, thus this listing corresponds to the tree:
1344
1345 add
1346 / \
1347 null null
1348 | |
1349 gvsv gvsv
1350
1351The execution order is indicated by C<===E<gt>> marks, thus it is C<3
13524 5 6> (node C<6> is not included into above listing), i.e.,
1353C<gvsv gvsv add whatever>.
1354
1355=head2 Compile pass 1: check routines
1356
1357The tree is created by the I<pseudo-compiler> while yacc code feeds it
1358the constructions it recognizes. Since yacc works bottom-up, so does
1359the first pass of perl compilation.
1360
1361What makes this pass interesting for perl developers is that some
1362optimization may be performed on this pass. This is optimization by
1363so-called I<check routines>. The correspondence between node names
1364and corresponding check routines is described in F<opcode.pl> (do not
1365forget to run C<make regen_headers> if you modify this file).
1366
1367A check routine is called when the node is fully constructed except
1368for the execution-order thread. Since at this time there is no
1369back-links to the currently constructed node, one can do most any
1370operation to the top-level node, including freeing it and/or creating
1371new nodes above/below it.
1372
1373The check routine returns the node which should be inserted into the
1374tree (if the top-level node was not modified, check routine returns
1375its argument).
1376
1377By convention, check routines have names C<ck_*>. They are usually
1378called from C<new*OP> subroutines (or C<convert>) (which in turn are
1379called from F<perly.y>).
1380
1381=head2 Compile pass 1a: constant folding
1382
1383Immediately after the check routine is called the returned node is
1384checked for being compile-time executable. If it is (the value is
1385judged to be constant) it is immediately executed, and a I<constant>
1386node with the "return value" of the corresponding subtree is
1387substituted instead. The subtree is deleted.
1388
1389If constant folding was not performed, the execution-order thread is
1390created.
1391
1392=head2 Compile pass 2: context propagation
1393
1394When a context for a part of compile tree is known, it is propagated
1395down through the tree. Aat this time the context can have 5 values
1396(instead of 2 for runtime context): void, boolean, scalar, list, and
1397lvalue. In contrast with the pass 1 this pass is processed from top
1398to bottom: a node's context determines the context for its children.
1399
1400Additional context-dependent optimizations are performed at this time.
1401Since at this moment the compile tree contains back-references (via
1402"thread" pointers), nodes cannot be free()d now. To allow
1403optimized-away nodes at this stage, such nodes are null()ified instead
1404of free()ing (i.e. their type is changed to OP_NULL).
1405
1406=head2 Compile pass 3: peephole optimization
1407
1408After the compile tree for a subroutine (or for an C<eval> or a file)
1409is created, an additional pass over the code is performed. This pass
1410is neither top-down or bottom-up, but in the execution order (with
1411additional compilications for conditionals). These optimizations are
1412done in the subroutine peep(). Optimizations performed at this stage
1413are subject to the same restrictions as in the pass 2.
1414
1415=head1 API LISTING
a0d0e21e 1416
cb1a09d0
AD
1417This is a listing of functions, macros, flags, and variables that may be
1418useful to extension writers or that may be found while reading other
1419extensions.
a0d0e21e 1420
cb1a09d0 1421=over 8
a0d0e21e 1422
cb1a09d0
AD
1423=item AvFILL
1424
fb73857a 1425Same as C<av_len>.
cb1a09d0
AD
1426
1427=item av_clear
1428
0146554f
GA
1429Clears an array, making it empty. Does not free the memory used by the
1430array itself.
cb1a09d0 1431
ef50df4b 1432 void av_clear (AV* ar)
cb1a09d0
AD
1433
1434=item av_extend
1435
1436Pre-extend an array. The C<key> is the index to which the array should be
1437extended.
1438
ef50df4b 1439 void av_extend (AV* ar, I32 key)
cb1a09d0
AD
1440
1441=item av_fetch
1442
1443Returns the SV at the specified index in the array. The C<key> is the
1444index. If C<lval> is set then the fetch will be part of a store. Check
1445that the return value is non-null before dereferencing it to a C<SV*>.
1446
04343c6d
GS
1447See L<Understanding the Magic of Tied Hashes and Arrays> for more
1448information on how to use this function on tied arrays.
1449
ef50df4b 1450 SV** av_fetch (AV* ar, I32 key, I32 lval)
cb1a09d0
AD
1451
1452=item av_len
1453
1454Returns the highest index in the array. Returns -1 if the array is empty.
1455
ef50df4b 1456 I32 av_len (AV* ar)
cb1a09d0
AD
1457
1458=item av_make
1459
5fb8527f
PP
1460Creates a new AV and populates it with a list of SVs. The SVs are copied
1461into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1462will have a reference count of 1.
cb1a09d0 1463
ef50df4b 1464 AV* av_make (I32 size, SV** svp)
cb1a09d0
AD
1465
1466=item av_pop
1467
1468Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
1469empty.
1470
ef50df4b 1471 SV* av_pop (AV* ar)
cb1a09d0
AD
1472
1473=item av_push
1474
5fb8527f
PP
1475Pushes an SV onto the end of the array. The array will grow automatically
1476to accommodate the addition.
cb1a09d0 1477
ef50df4b 1478 void av_push (AV* ar, SV* val)
cb1a09d0
AD
1479
1480=item av_shift
1481
1482Shifts an SV off the beginning of the array.
1483
ef50df4b 1484 SV* av_shift (AV* ar)
cb1a09d0
AD
1485
1486=item av_store
1487
1488Stores an SV in an array. The array index is specified as C<key>. The
04343c6d
GS
1489return value will be NULL if the operation failed or if the value did not
1490need to be actually stored within the array (as in the case of tied arrays).
1491Otherwise it can be dereferenced to get the original C<SV*>. Note that the
1492caller is responsible for suitably incrementing the reference count of C<val>
1493before the call, and decrementing it if the function returned NULL.
1494
1495See L<Understanding the Magic of Tied Hashes and Arrays> for more
1496information on how to use this function on tied arrays.
cb1a09d0 1497
ef50df4b 1498 SV** av_store (AV* ar, I32 key, SV* val)
cb1a09d0
AD
1499
1500=item av_undef
1501
0146554f 1502Undefines the array. Frees the memory used by the array itself.
cb1a09d0 1503
ef50df4b 1504 void av_undef (AV* ar)
cb1a09d0
AD
1505
1506=item av_unshift
1507
0146554f
GA
1508Unshift the given number of C<undef> values onto the beginning of the
1509array. The array will grow automatically to accommodate the addition.
1510You must then use C<av_store> to assign values to these new elements.
cb1a09d0 1511
ef50df4b 1512 void av_unshift (AV* ar, I32 num)
cb1a09d0
AD
1513
1514=item CLASS
1515
1516Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1517constructor. This is always a C<char*>. See C<THIS> and
1518L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1519
1520=item Copy
1521
1522The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1523source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 1524the type. May fail on overlapping copies. See also C<Move>.
cb1a09d0 1525
ef50df4b 1526 (void) Copy( s, d, n, t )
cb1a09d0
AD
1527
1528=item croak
1529
1530This is the XSUB-writer's interface to Perl's C<die> function. Use this
1531function the same way you use the C C<printf> function. See C<warn>.
1532
1533=item CvSTASH
1534
1535Returns the stash of the CV.
1536
1537 HV * CvSTASH( SV* sv )
1538
1539=item DBsingle
1540
1541When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1542boolean which indicates whether subs are being single-stepped.
5fb8527f
PP
1543Single-stepping is automatically turned on after every step. This is the C
1544variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
cb1a09d0
AD
1545
1546=item DBsub
1547
1548When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f
PP
1549the SV which holds the name of the sub being debugged. This is the C
1550variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
cb1a09d0
AD
1551The sub name can be found by
1552
1553 SvPV( GvSV( DBsub ), na )
1554
5fb8527f
PP
1555=item DBtrace
1556
1557Trace variable used when Perl is run in debugging mode, with the B<-d>
1558switch. This is the C variable which corresponds to Perl's $DB::trace
1559variable. See C<DBsingle>.
1560
cb1a09d0
AD
1561=item dMARK
1562
5fb8527f
PP
1563Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1564C<dORIGMARK>.
cb1a09d0
AD
1565
1566=item dORIGMARK
1567
1568Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1569
5fb8527f
PP
1570=item dowarn
1571
1572The C variable which corresponds to Perl's $^W warning variable.
1573
cb1a09d0
AD
1574=item dSP
1575
5fb8527f 1576Declares a stack pointer variable, C<sp>, for the XSUB. See C<SP>.
cb1a09d0
AD
1577
1578=item dXSARGS
1579
1580Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1581usually handled automatically by C<xsubpp>. Declares the C<items> variable
1582to indicate the number of items on the stack.
1583
5fb8527f
PP
1584=item dXSI32
1585
1586Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1587handled automatically by C<xsubpp>.
1588
cb1a09d0
AD
1589=item ENTER
1590
1591Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1592
1593 ENTER;
1594
1595=item EXTEND
1596
1597Used to extend the argument stack for an XSUB's return values.
1598
ef50df4b 1599 EXTEND( sp, int x )
cb1a09d0
AD
1600
1601=item FREETMPS
1602
1603Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1604L<perlcall>.
1605
1606 FREETMPS;
1607
1608=item G_ARRAY
1609
54310121 1610Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
cb1a09d0
AD
1611
1612=item G_DISCARD
1613
1614Indicates that arguments returned from a callback should be discarded. See
1615L<perlcall>.
1616
1617=item G_EVAL
1618
1619Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1620
1621=item GIMME
1622
54310121
PP
1623A backward-compatible version of C<GIMME_V> which can only return
1624C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
1625
1626=item GIMME_V
1627
1628The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
1629C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
1630context, respectively.
cb1a09d0
AD
1631
1632=item G_NOARGS
1633
1634Indicates that no arguments are being sent to a callback. See L<perlcall>.
1635
1636=item G_SCALAR
1637
54310121
PP
1638Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
1639
1640=item G_VOID
1641
1642Used to indicate void context. See C<GIMME_V> and L<perlcall>.
cb1a09d0 1643
faed5253
JO
1644=item gv_fetchmeth
1645
1646Returns the glob with the given C<name> and a defined subroutine or
9607fc9c
PP
1647C<NULL>. The glob lives in the given C<stash>, or in the stashes
1648accessable via @ISA and @<UNIVERSAL>.
faed5253 1649
9607fc9c 1650The argument C<level> should be either 0 or -1. If C<level==0>, as a
0a753a76
PP
1651side-effect creates a glob with the given C<name> in the given
1652C<stash> which in the case of success contains an alias for the
1653subroutine, and sets up caching info for this glob. Similarly for all
1654the searched stashes.
1655
9607fc9c
PP
1656This function grants C<"SUPER"> token as a postfix of the stash name.
1657
0a753a76
PP
1658The GV returned from C<gv_fetchmeth> may be a method cache entry,
1659which is not visible to Perl code. So when calling C<perl_call_sv>,
1660you should not use the GV directly; instead, you should use the
1661method's CV, which can be obtained from the GV with the C<GvCV> macro.
faed5253 1662
ef50df4b 1663 GV* gv_fetchmeth (HV* stash, char* name, STRLEN len, I32 level)
faed5253
JO
1664
1665=item gv_fetchmethod
1666
dc848c6f
PP
1667=item gv_fetchmethod_autoload
1668
faed5253 1669Returns the glob which contains the subroutine to call to invoke the
dc848c6f
PP
1670method on the C<stash>. In fact in the presense of autoloading this may
1671be the glob for "AUTOLOAD". In this case the corresponding variable
faed5253
JO
1672$AUTOLOAD is already setup.
1673
dc848c6f
PP
1674The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
1675lookup is performed if the given method is not present: non-zero means
1676yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
1677C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
1678non-zero C<autoload> parameter.
1679
1680These functions grant C<"SUPER"> token as a prefix of the method name.
1681
1682Note that if you want to keep the returned glob for a long time, you
1683need to check for it being "AUTOLOAD", since at the later time the call
faed5253
JO
1684may load a different subroutine due to $AUTOLOAD changing its value.
1685Use the glob created via a side effect to do this.
1686
dc848c6f
PP
1687These functions have the same side-effects and as C<gv_fetchmeth> with
1688C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
0a753a76 1689The warning against passing the GV returned by C<gv_fetchmeth> to
dc848c6f 1690C<perl_call_sv> apply equally to these functions.
faed5253 1691
ef50df4b
GS
1692 GV* gv_fetchmethod (HV* stash, char* name)
1693 GV* gv_fetchmethod_autoload (HV* stash, char* name, I32 autoload)
faed5253 1694
cb1a09d0
AD
1695=item gv_stashpv
1696
1697Returns a pointer to the stash for a specified package. If C<create> is set
1698then the package will be created if it does not already exist. If C<create>
1699is not set and the package does not exist then NULL is returned.
1700
ef50df4b 1701 HV* gv_stashpv (char* name, I32 create)
cb1a09d0
AD
1702
1703=item gv_stashsv
1704
1705Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1706
ef50df4b 1707 HV* gv_stashsv (SV* sv, I32 create)
cb1a09d0 1708
e5581bf4 1709=item GvSV
cb1a09d0 1710
e5581bf4 1711Return the SV from the GV.
44a8e56a 1712
1e422769
PP
1713=item HEf_SVKEY
1714
1715This flag, used in the length slot of hash entries and magic
1716structures, specifies the structure contains a C<SV*> pointer where a
1717C<char*> pointer is to be expected. (For information only--not to be used).
1718
1e422769
PP
1719=item HeHASH
1720
1721Returns the computed hash (type C<U32>) stored in the hash entry.
1722
1723 HeHASH(HE* he)
1724
1725=item HeKEY
1726
1727Returns the actual pointer stored in the key slot of the hash entry.
1728The pointer may be either C<char*> or C<SV*>, depending on the value of
1729C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1730are usually preferable for finding the value of a key.
1731
1732 HeKEY(HE* he)
1733
1734=item HeKLEN
1735
1736If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1737holds an C<SV*> key. Otherwise, holds the actual length of the key.
1738Can be assigned to. The C<HePV()> macro is usually preferable for finding
1739key lengths.
1740
1741 HeKLEN(HE* he)
1742
1743=item HePV
1744
1745Returns the key slot of the hash entry as a C<char*> value, doing any
1746necessary dereferencing of possibly C<SV*> keys. The length of
1747the string is placed in C<len> (this is a macro, so do I<not> use
1748C<&len>). If you do not care about what the length of the key is,
1749you may use the global variable C<na>. Remember though, that hash
1750keys in perl are free to contain embedded nulls, so using C<strlen()>
1751or similar is not a good way to find the length of hash keys.
1752This is very similar to the C<SvPV()> macro described elsewhere in
1753this document.
1754
1755 HePV(HE* he, STRLEN len)
1756
1757=item HeSVKEY
1758
1759Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1760does not contain an C<SV*> key.
1761
1762 HeSVKEY(HE* he)
1763
1764=item HeSVKEY_force
1765
1766Returns the key as an C<SV*>. Will create and return a temporary
1767mortal C<SV*> if the hash entry contains only a C<char*> key.
1768
1769 HeSVKEY_force(HE* he)
1770
1771=item HeSVKEY_set
1772
1773Sets the key to a given C<SV*>, taking care to set the appropriate flags
1774to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1775
1776 HeSVKEY_set(HE* he, SV* sv)
1777
1778=item HeVAL
1779
1780Returns the value slot (type C<SV*>) stored in the hash entry.
1781
1782 HeVAL(HE* he)
1783
cb1a09d0
AD
1784=item hv_clear
1785
1786Clears a hash, making it empty.
1787
ef50df4b 1788 void hv_clear (HV* tb)
cb1a09d0 1789
68dc0745
PP
1790=item hv_delayfree_ent
1791
1792Releases a hash entry, such as while iterating though the hash, but
1793delays actual freeing of key and value until the end of the current
1794statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
1795and C<hv_free_ent>.
1796
ef50df4b 1797 void hv_delayfree_ent (HV* hv, HE* entry)
68dc0745 1798
cb1a09d0
AD
1799=item hv_delete
1800
1801Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 1802and returned to the caller. The C<klen> is the length of the key. The
04343c6d 1803C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
cb1a09d0
AD
1804returned.
1805
ef50df4b 1806 SV* hv_delete (HV* tb, char* key, U32 klen, I32 flags)
cb1a09d0 1807
1e422769
PP
1808=item hv_delete_ent
1809
1810Deletes a key/value pair in the hash. The value SV is removed from the hash
1811and returned to the caller. The C<flags> value will normally be zero; if set
04343c6d 1812to G_DISCARD then NULL will be returned. C<hash> can be a valid precomputed
1e422769
PP
1813hash value, or 0 to ask for it to be computed.
1814
ef50df4b 1815 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash)
1e422769 1816
cb1a09d0
AD
1817=item hv_exists
1818
1819Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 1820C<klen> is the length of the key.
cb1a09d0 1821
ef50df4b 1822 bool hv_exists (HV* tb, char* key, U32 klen)
cb1a09d0 1823
1e422769
PP
1824=item hv_exists_ent
1825
1826Returns a boolean indicating whether the specified hash key exists. C<hash>
54310121 1827can be a valid precomputed hash value, or 0 to ask for it to be computed.
1e422769 1828
ef50df4b 1829 bool hv_exists_ent (HV* tb, SV* key, U32 hash)
1e422769 1830
cb1a09d0
AD
1831=item hv_fetch
1832
1833Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 1834C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
1835part of a store. Check that the return value is non-null before
1836dereferencing it to a C<SV*>.
1837
04343c6d
GS
1838See L<Understanding the Magic of Tied Hashes and Arrays> for more
1839information on how to use this function on tied hashes.
1840
ef50df4b 1841 SV** hv_fetch (HV* tb, char* key, U32 klen, I32 lval)
cb1a09d0 1842
1e422769
PP
1843=item hv_fetch_ent
1844
1845Returns the hash entry which corresponds to the specified key in the hash.
54310121 1846C<hash> must be a valid precomputed hash number for the given C<key>, or
1e422769
PP
18470 if you want the function to compute it. IF C<lval> is set then the
1848fetch will be part of a store. Make sure the return value is non-null
1849before accessing it. The return value when C<tb> is a tied hash
1850is a pointer to a static location, so be sure to make a copy of the
1851structure if you need to store it somewhere.
1852
04343c6d
GS
1853See L<Understanding the Magic of Tied Hashes and Arrays> for more
1854information on how to use this function on tied hashes.
1855
ef50df4b 1856 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash)
1e422769 1857
68dc0745
PP
1858=item hv_free_ent
1859
1860Releases a hash entry, such as while iterating though the hash. See
1861C<hv_iternext> and C<hv_delayfree_ent>.
1862
ef50df4b 1863 void hv_free_ent (HV* hv, HE* entry)
68dc0745 1864
cb1a09d0
AD
1865=item hv_iterinit
1866
1867Prepares a starting point to traverse a hash table.
1868
ef50df4b 1869 I32 hv_iterinit (HV* tb)
cb1a09d0 1870
fb73857a
PP
1871Note that hv_iterinit I<currently> returns the number of I<buckets> in
1872the hash and I<not> the number of keys (as indicated in the Advanced
1873Perl Programming book). This may change in future. Use the HvKEYS(hv)
1874macro to find the number of keys in a hash.
1875
cb1a09d0
AD
1876=item hv_iterkey
1877
1878Returns the key from the current position of the hash iterator. See
1879C<hv_iterinit>.
1880
ef50df4b 1881 char* hv_iterkey (HE* entry, I32* retlen)
cb1a09d0 1882
1e422769 1883=item hv_iterkeysv
3fe9a6f1 1884
1e422769
PP
1885Returns the key as an C<SV*> from the current position of the hash
1886iterator. The return value will always be a mortal copy of the
1887key. Also see C<hv_iterinit>.
1888
ef50df4b 1889 SV* hv_iterkeysv (HE* entry)
1e422769 1890
cb1a09d0
AD
1891=item hv_iternext
1892
1893Returns entries from a hash iterator. See C<hv_iterinit>.
1894
ef50df4b 1895 HE* hv_iternext (HV* tb)
cb1a09d0
AD
1896
1897=item hv_iternextsv
1898
1899Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1900operation.
1901
ef50df4b 1902 SV * hv_iternextsv (HV* hv, char** key, I32* retlen)
cb1a09d0
AD
1903
1904=item hv_iterval
1905
1906Returns the value from the current position of the hash iterator. See
1907C<hv_iterkey>.
1908
ef50df4b 1909 SV* hv_iterval (HV* tb, HE* entry)
cb1a09d0
AD
1910
1911=item hv_magic
1912
1913Adds magic to a hash. See C<sv_magic>.
1914
ef50df4b 1915 void hv_magic (HV* hv, GV* gv, int how)
cb1a09d0
AD
1916
1917=item HvNAME
1918
1919Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1920
1921 char *HvNAME (HV* stash)
1922
1923=item hv_store
1924
1925Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
54310121 1926the length of the key. The C<hash> parameter is the precomputed hash
cb1a09d0 1927value; if it is zero then Perl will compute it. The return value will be
04343c6d
GS
1928NULL if the operation failed or if the value did not need to be actually
1929stored within the hash (as in the case of tied hashes). Otherwise it can
1930be dereferenced to get the original C<SV*>. Note that the caller is
1931responsible for suitably incrementing the reference count of C<val>
1932before the call, and decrementing it if the function returned NULL.
1933
1934See L<Understanding the Magic of Tied Hashes and Arrays> for more
1935information on how to use this function on tied hashes.
cb1a09d0 1936
ef50df4b 1937 SV** hv_store (HV* tb, char* key, U32 klen, SV* val, U32 hash)
cb1a09d0 1938
1e422769
PP
1939=item hv_store_ent
1940
1941Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
54310121 1942parameter is the precomputed hash value; if it is zero then Perl will
1e422769 1943compute it. The return value is the new hash entry so created. It will be
04343c6d
GS
1944NULL if the operation failed or if the value did not need to be actually
1945stored within the hash (as in the case of tied hashes). Otherwise the
1946contents of the return value can be accessed using the C<He???> macros
1947described here. Note that the caller is responsible for suitably
1948incrementing the reference count of C<val> before the call, and decrementing
1949it if the function returned NULL.
1950
1951See L<Understanding the Magic of Tied Hashes and Arrays> for more
1952information on how to use this function on tied hashes.
1e422769 1953
ef50df4b 1954 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash)
1e422769 1955
cb1a09d0
AD
1956=item hv_undef
1957
1958Undefines the hash.
1959
ef50df4b 1960 void hv_undef (HV* tb)
cb1a09d0
AD
1961
1962=item isALNUM
1963
1964Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 1965character or digit.
cb1a09d0
AD
1966
1967 int isALNUM (char c)
1968
1969=item isALPHA
1970
5fb8527f 1971Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
1972character.
1973
1974 int isALPHA (char c)
1975
1976=item isDIGIT
1977
1978Returns a boolean indicating whether the C C<char> is an ascii digit.
1979
1980 int isDIGIT (char c)
1981
1982=item isLOWER
1983
1984Returns a boolean indicating whether the C C<char> is a lowercase character.
1985
1986 int isLOWER (char c)
1987
1988=item isSPACE
1989
1990Returns a boolean indicating whether the C C<char> is whitespace.
1991
1992 int isSPACE (char c)
1993
1994=item isUPPER
1995
1996Returns a boolean indicating whether the C C<char> is an uppercase character.
1997
1998 int isUPPER (char c)
1999
2000=item items
2001
2002Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
2003stack. See L<perlxs/"Variable-length Parameter Lists">.
2004
2005=item ix
2006
2007Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
2008was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
2009
2010=item LEAVE
2011
2012Closing bracket on a callback. See C<ENTER> and L<perlcall>.
2013
2014 LEAVE;
2015
2016=item MARK
2017
5fb8527f 2018Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
2019
2020=item mg_clear
2021
2022Clear something magical that the SV represents. See C<sv_magic>.
2023
ef50df4b 2024 int mg_clear (SV* sv)
cb1a09d0
AD
2025
2026=item mg_copy
2027
2028Copies the magic from one SV to another. See C<sv_magic>.
2029
ef50df4b 2030 int mg_copy (SV *, SV *, char *, STRLEN)
cb1a09d0
AD
2031
2032=item mg_find
2033
2034Finds the magic pointer for type matching the SV. See C<sv_magic>.
2035
ef50df4b 2036 MAGIC* mg_find (SV* sv, int type)
cb1a09d0
AD
2037
2038=item mg_free
2039
2040Free any magic storage used by the SV. See C<sv_magic>.
2041
ef50df4b 2042 int mg_free (SV* sv)
cb1a09d0
AD
2043
2044=item mg_get
2045
2046Do magic after a value is retrieved from the SV. See C<sv_magic>.
2047
ef50df4b 2048 int mg_get (SV* sv)
cb1a09d0
AD
2049
2050=item mg_len
2051
2052Report on the SV's length. See C<sv_magic>.
2053
ef50df4b 2054 U32 mg_len (SV* sv)
cb1a09d0
AD
2055
2056=item mg_magical
2057
2058Turns on the magical status of an SV. See C<sv_magic>.
2059
ef50df4b 2060 void mg_magical (SV* sv)
cb1a09d0
AD
2061
2062=item mg_set
2063
2064Do magic after a value is assigned to the SV. See C<sv_magic>.
2065
ef50df4b 2066 int mg_set (SV* sv)
cb1a09d0
AD
2067
2068=item Move
2069
2070The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
2071source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 2072the type. Can do overlapping moves. See also C<Copy>.
cb1a09d0 2073
ef50df4b 2074 (void) Move( s, d, n, t )
cb1a09d0
AD
2075
2076=item na
2077
2078A variable which may be used with C<SvPV> to tell Perl to calculate the
2079string length.
2080
2081=item New
2082
2083The XSUB-writer's interface to the C C<malloc> function.
2084
2085 void * New( x, void *ptr, int size, type )
2086
2087=item Newc
2088
2089The XSUB-writer's interface to the C C<malloc> function, with cast.
2090
2091 void * Newc( x, void *ptr, int size, type, cast )
2092
2093=item Newz
2094
2095The XSUB-writer's interface to the C C<malloc> function. The allocated
2096memory is zeroed with C<memzero>.
2097
2098 void * Newz( x, void *ptr, int size, type )
2099
2100=item newAV
2101
5f05dabc 2102Creates a new AV. The reference count is set to 1.
cb1a09d0 2103
ef50df4b 2104 AV* newAV (void)
cb1a09d0
AD
2105
2106=item newHV
2107
5f05dabc 2108Creates a new HV. The reference count is set to 1.
cb1a09d0 2109
ef50df4b 2110 HV* newHV (void)
cb1a09d0 2111
5f05dabc 2112=item newRV_inc
cb1a09d0 2113
5f05dabc 2114Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
2115incremented.
2116
ef50df4b 2117 SV* newRV_inc (SV* ref)
5f05dabc
PP
2118
2119For historical reasons, "newRV" is a synonym for "newRV_inc".
2120
2121=item newRV_noinc
2122
2123Creates an RV wrapper for an SV. The reference count for the original
2124SV is B<not> incremented.
2125
ef50df4b 2126 SV* newRV_noinc (SV* ref)
cb1a09d0 2127
8c52afec 2128=item NEWSV
cb1a09d0
AD
2129
2130Creates a new SV. The C<len> parameter indicates the number of bytes of
68dc0745 2131preallocated string space the SV should have. The reference count for the
8c52afec
IZ
2132new SV is set to 1. C<id> is an integer id between 0 and 1299 (used to
2133identify leaks).
cb1a09d0 2134
ef50df4b 2135 SV* NEWSV (int id, STRLEN len)
cb1a09d0
AD
2136
2137=item newSViv
2138
07fa94a1
JO
2139Creates a new SV and copies an integer into it. The reference count for the
2140SV is set to 1.
cb1a09d0 2141
ef50df4b 2142 SV* newSViv (IV i)
cb1a09d0
AD
2143
2144=item newSVnv
2145
07fa94a1
JO
2146Creates a new SV and copies a double into it. The reference count for the
2147SV is set to 1.
cb1a09d0 2148
ef50df4b 2149 SV* newSVnv (NV i)
cb1a09d0
AD
2150
2151=item newSVpv
2152
07fa94a1
JO
2153Creates a new SV and copies a string into it. The reference count for the
2154SV is set to 1. If C<len> is zero then Perl will compute the length.
cb1a09d0 2155
ef50df4b 2156 SV* newSVpv (char* s, STRLEN len)
cb1a09d0 2157
9da1e3b5
MUN
2158=item newSVpvn
2159
2160Creates a new SV and copies a string into it. The reference count for the
2161SV is set to 1. If C<len> is zero then Perl will create a zero length
2162string.
2163
ef50df4b 2164 SV* newSVpvn (char* s, STRLEN len)
9da1e3b5 2165
cb1a09d0
AD
2166=item newSVrv
2167
2168Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 2169it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 2170be blessed in the specified package. The new SV is returned and its
5f05dabc 2171reference count is 1.
8ebc5c01 2172
ef50df4b 2173 SV* newSVrv (SV* rv, char* classname)
cb1a09d0
AD
2174
2175=item newSVsv
2176
5fb8527f 2177Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0 2178
ef50df4b 2179 SV* newSVsv (SV* old)
cb1a09d0
AD
2180
2181=item newXS
2182
2183Used by C<xsubpp> to hook up XSUBs as Perl subs.
2184
2185=item newXSproto
2186
2187Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
2188the subs.
2189
2190=item Nullav
2191
2192Null AV pointer.
2193
2194=item Nullch
2195
2196Null character pointer.
2197
2198=item Nullcv
2199
2200Null CV pointer.
2201
2202=item Nullhv
2203
2204Null HV pointer.
2205
2206=item Nullsv
2207
2208Null SV pointer.
2209
2210=item ORIGMARK
2211
2212The original stack mark for the XSUB. See C<dORIGMARK>.
2213
2214=item perl_alloc
2215
2216Allocates a new Perl interpreter. See L<perlembed>.
2217
2218=item perl_call_argv
2219
2220Performs a callback to the specified Perl sub. See L<perlcall>.
2221
ef50df4b 2222 I32 perl_call_argv (char* subname, I32 flags, char** argv)
cb1a09d0
AD
2223
2224=item perl_call_method
2225
2226Performs a callback to the specified Perl method. The blessed object must
2227be on the stack. See L<perlcall>.
2228
ef50df4b 2229 I32 perl_call_method (char* methname, I32 flags)
cb1a09d0
AD
2230
2231=item perl_call_pv
2232
2233Performs a callback to the specified Perl sub. See L<perlcall>.
2234
ef50df4b 2235 I32 perl_call_pv (char* subname, I32 flags)
cb1a09d0
AD
2236
2237=item perl_call_sv
2238
2239Performs a callback to the Perl sub whose name is in the SV. See
2240L<perlcall>.
2241
ef50df4b 2242 I32 perl_call_sv (SV* sv, I32 flags)
cb1a09d0
AD
2243
2244=item perl_construct
2245
2246Initializes a new Perl interpreter. See L<perlembed>.
2247
2248=item perl_destruct
2249
2250Shuts down a Perl interpreter. See L<perlembed>.
2251
2252=item perl_eval_sv
2253
2254Tells Perl to C<eval> the string in the SV.
2255
ef50df4b 2256 I32 perl_eval_sv (SV* sv, I32 flags)
cb1a09d0 2257
137443ea
PP
2258=item perl_eval_pv
2259
2260Tells Perl to C<eval> the given string and return an SV* result.
2261
ef50df4b 2262 SV* perl_eval_pv (char* p, I32 croak_on_error)
137443ea 2263
cb1a09d0
AD
2264=item perl_free
2265
2266Releases a Perl interpreter. See L<perlembed>.
2267
2268=item perl_get_av
2269
2270Returns the AV of the specified Perl array. If C<create> is set and the
2271Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2272set and the variable does not exist then NULL is returned.
cb1a09d0 2273
ef50df4b 2274 AV* perl_get_av (char* name, I32 create)
cb1a09d0
AD
2275
2276=item perl_get_cv
2277
2278Returns the CV of the specified Perl sub. If C<create> is set and the Perl
2279variable does not exist then it will be created. If C<create> is not
04343c6d 2280set and the variable does not exist then NULL is returned.
cb1a09d0 2281
ef50df4b 2282 CV* perl_get_cv (char* name, I32 create)
cb1a09d0
AD
2283
2284=item perl_get_hv
2285
2286Returns the HV of the specified Perl hash. If C<create> is set and the Perl
2287variable does not exist then it will be created. If C<create> is not
04343c6d 2288set and the variable does not exist then NULL is returned.
cb1a09d0 2289
ef50df4b 2290 HV* perl_get_hv (char* name, I32 create)
cb1a09d0
AD
2291
2292=item perl_get_sv
2293
2294Returns the SV of the specified Perl scalar. If C<create> is set and the
2295Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2296set and the variable does not exist then NULL is returned.
cb1a09d0 2297
ef50df4b 2298 SV* perl_get_sv (char* name, I32 create)
cb1a09d0
AD
2299
2300=item perl_parse
2301
2302Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2303
2304=item perl_require_pv
2305
2306Tells Perl to C<require> a module.
2307
ef50df4b 2308 void perl_require_pv (char* pv)
cb1a09d0
AD
2309
2310=item perl_run
2311
2312Tells a Perl interpreter to run. See L<perlembed>.
2313
2314=item POPi
2315
2316Pops an integer off the stack.
2317
ef50df4b 2318 int POPi()
cb1a09d0
AD
2319
2320=item POPl
2321
2322Pops a long off the stack.
2323
ef50df4b 2324 long POPl()
cb1a09d0
AD
2325
2326=item POPp
2327
2328Pops a string off the stack.
2329
ef50df4b 2330 char * POPp()
cb1a09d0
AD
2331
2332=item POPn
2333
2334Pops a double off the stack.
2335
ef50df4b 2336 double POPn()
cb1a09d0
AD
2337
2338=item POPs
2339
2340Pops an SV off the stack.
2341
ef50df4b 2342 SV* POPs()
cb1a09d0
AD
2343
2344=item PUSHMARK
2345
2346Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2347
2348 PUSHMARK(p)
2349
2350=item PUSHi
2351
2352Push an integer onto the stack. The stack must have room for this element.
189b2af5 2353Handles 'set' magic. See C<XPUSHi>.
cb1a09d0
AD
2354
2355 PUSHi(int d)
2356
2357=item PUSHn
2358
2359Push a double onto the stack. The stack must have room for this element.
189b2af5 2360Handles 'set' magic. See C<XPUSHn>.
cb1a09d0
AD
2361
2362 PUSHn(double d)
2363
2364=item PUSHp
2365
2366Push a string onto the stack. The stack must have room for this element.
189b2af5
GS
2367The C<len> indicates the length of the string. Handles 'set' magic. See
2368C<XPUSHp>.
cb1a09d0
AD
2369
2370 PUSHp(char *c, int len )
2371
2372=item PUSHs
2373
189b2af5
GS
2374Push an SV onto the stack. The stack must have room for this element. Does
2375not handle 'set' magic. See C<XPUSHs>.
cb1a09d0
AD
2376
2377 PUSHs(sv)
2378
2379=item PUTBACK
2380
2381Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2382See C<PUSHMARK> and L<perlcall> for other uses.
2383
2384 PUTBACK;
2385
2386=item Renew
2387
2388The XSUB-writer's interface to the C C<realloc> function.
2389
2390 void * Renew( void *ptr, int size, type )
2391
2392=item Renewc
2393
2394The XSUB-writer's interface to the C C<realloc> function, with cast.
2395
2396 void * Renewc( void *ptr, int size, type, cast )
2397
2398=item RETVAL
2399
2400Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
2401This is always the proper type for the XSUB.
2402See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
2403
2404=item safefree
2405
2406The XSUB-writer's interface to the C C<free> function.
2407
2408=item safemalloc
2409
2410The XSUB-writer's interface to the C C<malloc> function.
2411
2412=item saferealloc
2413
2414The XSUB-writer's interface to the C C<realloc> function.
2415
2416=item savepv
2417
2418Copy a string to a safe spot. This does not use an SV.
2419
ef50df4b 2420 char* savepv (char* sv)
cb1a09d0
AD
2421
2422=item savepvn
2423
2424Copy a string to a safe spot. The C<len> indicates number of bytes to
2425copy. This does not use an SV.
2426
ef50df4b 2427 char* savepvn (char* sv, I32 len)
cb1a09d0
AD
2428
2429=item SAVETMPS
2430
2431Opening bracket for temporaries on a callback. See C<FREETMPS> and
2432L<perlcall>.
2433
2434 SAVETMPS;
2435
2436=item SP
2437
2438Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2439C<SPAGAIN>.
2440
2441=item SPAGAIN
2442
54310121 2443Refetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
2444
2445 SPAGAIN;
2446
2447=item ST
2448
2449Used to access elements on the XSUB's stack.
2450
2451 SV* ST(int x)
2452
2453=item strEQ
2454
2455Test two strings to see if they are equal. Returns true or false.
2456
2457 int strEQ( char *s1, char *s2 )
2458
2459=item strGE
2460
2461Test two strings to see if the first, C<s1>, is greater than or equal to the
2462second, C<s2>. Returns true or false.
2463
2464 int strGE( char *s1, char *s2 )
2465
2466=item strGT
2467
2468Test two strings to see if the first, C<s1>, is greater than the second,
2469C<s2>. Returns true or false.
2470
2471 int strGT( char *s1, char *s2 )
2472
2473=item strLE
2474
2475Test two strings to see if the first, C<s1>, is less than or equal to the
2476second, C<s2>. Returns true or false.
2477
2478 int strLE( char *s1, char *s2 )
2479
2480=item strLT
2481
2482Test two strings to see if the first, C<s1>, is less than the second,
2483C<s2>. Returns true or false.
2484
2485 int strLT( char *s1, char *s2 )
2486
2487=item strNE
2488
2489Test two strings to see if they are different. Returns true or false.
2490
2491 int strNE( char *s1, char *s2 )
2492
2493=item strnEQ
2494
2495Test two strings to see if they are equal. The C<len> parameter indicates
2496the number of bytes to compare. Returns true or false.
2497
2498 int strnEQ( char *s1, char *s2 )
2499
2500=item strnNE
2501
2502Test two strings to see if they are different. The C<len> parameter
2503indicates the number of bytes to compare. Returns true or false.
2504
2505 int strnNE( char *s1, char *s2, int len )
2506
2507=item sv_2mortal
2508
2509Marks an SV as mortal. The SV will be destroyed when the current context
2510ends.
2511
ef50df4b 2512 SV* sv_2mortal (SV* sv)
cb1a09d0
AD
2513
2514=item sv_bless
2515
2516Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
2517must be designated by its stash (see C<gv_stashpv()>). The reference count
2518of the SV is unaffected.
cb1a09d0 2519
ef50df4b 2520 SV* sv_bless (SV* sv, HV* stash)
cb1a09d0 2521
ef50df4b 2522=item sv_catpv
189b2af5 2523
ef50df4b
GS
2524Concatenates the string onto the end of the string which is in the SV.
2525Handles 'get' magic, but not 'set' magic. See C<sv_catpv_mg>.
189b2af5 2526
ef50df4b 2527 void sv_catpv (SV* sv, char* ptr)
189b2af5 2528
ef50df4b 2529=item sv_catpv_mg
cb1a09d0 2530
ef50df4b 2531Like C<sv_catpv>, but also handles 'set' magic.
cb1a09d0 2532
ef50df4b 2533 void sv_catpvn (SV* sv, char* ptr)
cb1a09d0
AD
2534
2535=item sv_catpvn
2536
2537Concatenates the string onto the end of the string which is in the SV. The
189b2af5 2538C<len> indicates number of bytes to copy. Handles 'get' magic, but not
ef50df4b 2539'set' magic. See C<sv_catpvn_mg>.
cb1a09d0 2540
ef50df4b
GS
2541 void sv_catpvn (SV* sv, char* ptr, STRLEN len)
2542
2543=item sv_catpvn_mg
2544
2545Like C<sv_catpvn>, but also handles 'set' magic.
2546
2547 void sv_catpvn_mg (SV* sv, char* ptr, STRLEN len)
cb1a09d0 2548
46fc3d4c
PP
2549=item sv_catpvf
2550
2551Processes its arguments like C<sprintf> and appends the formatted output
189b2af5
GS
2552to an SV. Handles 'get' magic, but not 'set' magic. C<SvSETMAGIC()> must
2553typically be called after calling this function to handle 'set' magic.
46fc3d4c 2554
ef50df4b
GS
2555 void sv_catpvf (SV* sv, const char* pat, ...)
2556
2557=item sv_catpvf_mg
2558
2559Like C<sv_catpvf>, but also handles 'set' magic.
2560
2561 void sv_catpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 2562
cb1a09d0
AD
2563=item sv_catsv
2564
5fb8527f 2565Concatenates the string from SV C<ssv> onto the end of the string in SV
ef50df4b
GS
2566C<dsv>. Handles 'get' magic, but not 'set' magic. See C<sv_catsv_mg>.
2567
2568 void sv_catsv (SV* dsv, SV* ssv)
2569
2570=item sv_catsv_mg
cb1a09d0 2571
ef50df4b
GS
2572Like C<sv_catsv>, but also handles 'set' magic.
2573
2574 void sv_catsv_mg (SV* dsv, SV* ssv)
cb1a09d0 2575
5fb8527f
PP
2576=item sv_cmp
2577
2578Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2579string in C<sv1> is less than, equal to, or greater than the string in
2580C<sv2>.
2581
ef50df4b 2582 I32 sv_cmp (SV* sv1, SV* sv2)
5fb8527f 2583
cb1a09d0
AD
2584=item SvCUR
2585
2586Returns the length of the string which is in the SV. See C<SvLEN>.
2587
2588 int SvCUR (SV* sv)
2589
2590=item SvCUR_set
2591
2592Set the length of the string which is in the SV. See C<SvCUR>.
2593
2594 SvCUR_set (SV* sv, int val )
2595
5fb8527f
PP
2596=item sv_dec
2597
5f05dabc 2598Auto-decrement of the value in the SV.
5fb8527f 2599
ef50df4b 2600 void sv_dec (SV* sv)
5fb8527f 2601
cb1a09d0
AD
2602=item SvEND
2603
2604Returns a pointer to the last character in the string which is in the SV.
2605See C<SvCUR>. Access the character as
2606
2607 *SvEND(sv)
2608
5fb8527f
PP
2609=item sv_eq
2610
2611Returns a boolean indicating whether the strings in the two SVs are
2612identical.
2613
ef50df4b 2614 I32 sv_eq (SV* sv1, SV* sv2)
5fb8527f 2615
189b2af5
GS
2616=item SvGETMAGIC
2617
2618Invokes C<mg_get> on an SV if it has 'get' magic. This macro evaluates
2619its argument more than once.
2620
2621 void SvGETMAGIC( SV *sv )
2622
cb1a09d0
AD
2623=item SvGROW
2624
5fb8527f
PP
2625Expands the character buffer in the SV. Calls C<sv_grow> to perform the
2626expansion if necessary. Returns a pointer to the character buffer.
cb1a09d0
AD
2627
2628 char * SvGROW( SV* sv, int len )
2629
5fb8527f
PP
2630=item sv_grow
2631
2632Expands the character buffer in the SV. This will use C<sv_unref> and will
2633upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2634Use C<SvGROW>.
2635
2636=item sv_inc
2637
07fa94a1 2638Auto-increment of the value in the SV.
5fb8527f 2639
ef50df4b 2640 void sv_inc (SV* sv)
5fb8527f 2641
cb1a09d0
AD
2642=item SvIOK
2643
2644Returns a boolean indicating whether the SV contains an integer.
2645
2646 int SvIOK (SV* SV)
2647
2648=item SvIOK_off
2649
2650Unsets the IV status of an SV.
2651
2652 SvIOK_off (SV* sv)
2653
2654=item SvIOK_on
2655
2656Tells an SV that it is an integer.
2657
2658 SvIOK_on (SV* sv)
2659
5fb8527f
PP
2660=item SvIOK_only
2661
2662Tells an SV that it is an integer and disables all other OK bits.
2663
2664 SvIOK_on (SV* sv)
2665
cb1a09d0
AD
2666=item SvIOKp
2667
2668Returns a boolean indicating whether the SV contains an integer. Checks the
2669B<private> setting. Use C<SvIOK>.
2670
2671 int SvIOKp (SV* SV)
2672
2673=item sv_isa
2674
2675Returns a boolean indicating whether the SV is blessed into the specified
2676class. This does not know how to check for subtype, so it doesn't work in
2677an inheritance relationship.
2678
ef50df4b 2679 int sv_isa (SV* sv, char* name)
cb1a09d0
AD
2680
2681=item SvIV
2682
2683Returns the integer which is in the SV.
2684
2685 int SvIV (SV* sv)
2686
2687=item sv_isobject
2688
2689Returns a boolean indicating whether the SV is an RV pointing to a blessed
2690object. If the SV is not an RV, or if the object is not blessed, then this
2691will return false.
2692
ef50df4b 2693 int sv_isobject (SV* sv)
cb1a09d0
AD
2694
2695=item SvIVX
2696
2697Returns the integer which is stored in the SV.
2698
ef50df4b 2699 int SvIVX (SV* sv)
cb1a09d0
AD
2700
2701=item SvLEN
2702
2703Returns the size of the string buffer in the SV. See C<SvCUR>.
2704
2705 int SvLEN (SV* sv)
2706
5fb8527f
PP
2707=item sv_len
2708
2709Returns the length of the string in the SV. Use C<SvCUR>.
2710
ef50df4b 2711 STRLEN sv_len (SV* sv)
5fb8527f 2712
cb1a09d0
AD
2713=item sv_magic
2714
2715Adds magic to an SV.
2716
ef50df4b 2717 void sv_magic (SV* sv, SV* obj, int how, char* name, I32 namlen)
cb1a09d0
AD
2718
2719=item sv_mortalcopy
2720
2721Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 2722as mortal.
cb1a09d0 2723
ef50df4b 2724 SV* sv_mortalcopy (SV* oldsv)
cb1a09d0
AD
2725
2726=item SvOK
2727
2728Returns a boolean indicating whether the value is an SV.
2729
2730 int SvOK (SV* sv)
2731
2732=item sv_newmortal
2733
5f05dabc 2734Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0 2735
ef50df4b 2736 SV* sv_newmortal (void)
cb1a09d0
AD
2737
2738=item sv_no
2739
2740This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
2741
2742=item SvNIOK
2743
2744Returns a boolean indicating whether the SV contains a number, integer or
2745double.
2746
2747 int SvNIOK (SV* SV)
2748
2749=item SvNIOK_off
2750
2751Unsets the NV/IV status of an SV.
2752
2753 SvNIOK_off (SV* sv)
2754
2755=item SvNIOKp
2756
2757Returns a boolean indicating whether the SV contains a number, integer or
2758double. Checks the B<private> setting. Use C<SvNIOK>.
2759
2760 int SvNIOKp (SV* SV)
2761
2762=item SvNOK
2763
2764Returns a boolean indicating whether the SV contains a double.
2765
2766 int SvNOK (SV* SV)
2767
2768=item SvNOK_off
2769
2770Unsets the NV status of an SV.
2771
2772 SvNOK_off (SV* sv)
2773
2774=item SvNOK_on
2775
2776Tells an SV that it is a double.
2777
2778 SvNOK_on (SV* sv)
2779
5fb8527f
PP
2780=item SvNOK_only
2781
2782Tells an SV that it is a double and disables all other OK bits.
2783
2784 SvNOK_on (SV* sv)
2785
cb1a09d0
AD
2786=item SvNOKp
2787
2788Returns a boolean indicating whether the SV contains a double. Checks the
2789B<private> setting. Use C<SvNOK>.
2790
2791 int SvNOKp (SV* SV)
2792
2793=item SvNV
2794
2795Returns the double which is stored in the SV.
2796
ef50df4b 2797 double SvNV (SV* sv)
cb1a09d0
AD
2798
2799=item SvNVX
2800
2801Returns the double which is stored in the SV.
2802
ef50df4b 2803 double SvNVX (SV* sv)
cb1a09d0
AD
2804
2805=item SvPOK
2806
2807Returns a boolean indicating whether the SV contains a character string.
2808
2809 int SvPOK (SV* SV)
2810
2811=item SvPOK_off
2812
2813Unsets the PV status of an SV.
2814
2815 SvPOK_off (SV* sv)
2816
2817=item SvPOK_on
2818
2819Tells an SV that it is a string.
2820
2821 SvPOK_on (SV* sv)
2822
5fb8527f
PP
2823=item SvPOK_only
2824
2825Tells an SV that it is a string and disables all other OK bits.
2826
2827 SvPOK_on (SV* sv)
2828
cb1a09d0
AD
2829=item SvPOKp
2830
2831Returns a boolean indicating whether the SV contains a character string.
2832Checks the B<private> setting. Use C<SvPOK>.
2833
2834 int SvPOKp (SV* SV)
2835
2836=item SvPV
2837
2838Returns a pointer to the string in the SV, or a stringified form of the SV
2839if the SV does not contain a string. If C<len> is C<na> then Perl will
189b2af5 2840handle the length on its own. Handles 'get' magic.
cb1a09d0
AD
2841
2842 char * SvPV (SV* sv, int len )
2843
2844=item SvPVX
2845
2846Returns a pointer to the string in the SV. The SV must contain a string.
2847
2848 char * SvPVX (SV* sv)
2849
2850=item SvREFCNT
2851
5f05dabc 2852Returns the value of the object's reference count.
cb1a09d0 2853
ef50df4b 2854 int SvREFCNT (SV* sv)
cb1a09d0
AD
2855
2856=item SvREFCNT_dec
2857
5f05dabc 2858Decrements the reference count of the given SV.
cb1a09d0
AD
2859
2860 void SvREFCNT_dec (SV* sv)
2861
2862=item SvREFCNT_inc
2863
5f05dabc 2864Increments the reference count of the given SV.
cb1a09d0
AD
2865
2866 void SvREFCNT_inc (SV* sv)
2867
2868=item SvROK
2869
2870Tests if the SV is an RV.
2871
2872 int SvROK (SV* sv)
2873
2874=item SvROK_off
2875
2876Unsets the RV status of an SV.
2877
2878 SvROK_off (SV* sv)
2879
2880=item SvROK_on
2881
2882Tells an SV that it is an RV.
2883
2884 SvROK_on (SV* sv)
2885
2886=item SvRV
2887
2888Dereferences an RV to return the SV.
2889
ef50df4b 2890 SV* SvRV (SV* sv)
cb1a09d0 2891
189b2af5
GS
2892=item SvSETMAGIC
2893
2894Invokes C<mg_set> on an SV if it has 'set' magic. This macro evaluates
2895its argument more than once.
2896
2897 void SvSETMAGIC( SV *sv )
2898
fb73857a
PP
2899=item SvTAINT
2900
2901Taints an SV if tainting is enabled
2902
ef50df4b 2903 SvTAINT (SV* sv)
fb73857a
PP
2904
2905=item SvTAINTED
2906
2907Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.
2908
ef50df4b 2909 SvTAINTED (SV* sv)
fb73857a
PP
2910
2911=item SvTAINTED_off
2912
2913Untaints an SV. Be I<very> careful with this routine, as it short-circuits
2914some of Perl's fundamental security features. XS module authors should
2915not use this function unless they fully understand all the implications
2916of unconditionally untainting the value. Untainting should be done in
2917the standard perl fashion, via a carefully crafted regexp, rather than
2918directly untainting variables.
2919
ef50df4b 2920 SvTAINTED_off (SV* sv)
fb73857a
PP
2921
2922=item SvTAINTED_on
2923
2924Marks an SV as tainted.
2925
ef50df4b 2926 SvTAINTED_on (SV* sv)
189b2af5 2927
ef50df4b 2928=item sv_setiv
189b2af5 2929
ef50df4b
GS
2930Copies an integer into the given SV. Does not handle 'set' magic.
2931See C<sv_setiv_mg>.
189b2af5 2932
ef50df4b 2933 void sv_setiv (SV* sv, IV num)
189b2af5 2934
ef50df4b 2935=item sv_setiv_mg
189b2af5 2936
ef50df4b 2937Like C<sv_setiv>, but also handles 'set' magic.
189b2af5 2938
ef50df4b 2939 void sv_setiv_mg (SV* sv, IV num)
189b2af5 2940
ef50df4b 2941=item sv_setnv
189b2af5 2942
ef50df4b
GS
2943Copies a double into the given SV. Does not handle 'set' magic.
2944See C<sv_setnv_mg>.
189b2af5 2945
ef50df4b 2946 void sv_setnv (SV* sv, double num)
189b2af5 2947
ef50df4b 2948=item sv_setnv_mg
189b2af5 2949
ef50df4b 2950Like C<sv_setnv>, but also handles 'set' magic.
189b2af5 2951
ef50df4b 2952 void sv_setnv_mg (SV* sv, double num)
189b2af5 2953
ef50df4b 2954=item sv_setpv
189b2af5 2955
ef50df4b
GS
2956Copies a string into an SV. The string must be null-terminated.
2957Does not handle 'set' magic. See C<sv_setpv_mg>.
189b2af5 2958
ef50df4b 2959 void sv_setpv (SV* sv, char* ptr)
189b2af5 2960
ef50df4b 2961=item sv_setpv_mg
189b2af5 2962
ef50df4b 2963Like C<sv_setpv>, but also handles 'set' magic.
189b2af5 2964
ef50df4b 2965 void sv_setpv_mg (SV* sv, char* ptr)
189b2af5 2966
ef50df4b 2967=item sv_setpviv
cb1a09d0 2968
ef50df4b
GS
2969Copies an integer into the given SV, also updating its string value.
2970Does not handle 'set' magic. See C<sv_setpviv_mg>.
cb1a09d0 2971
ef50df4b 2972 void sv_setpviv (SV* sv, IV num)
cb1a09d0 2973
ef50df4b 2974=item sv_setpviv_mg
cb1a09d0 2975
ef50df4b 2976Like C<sv_setpviv>, but also handles 'set' magic.
cb1a09d0 2977
ef50df4b 2978 void sv_setpviv_mg (SV* sv, IV num)
cb1a09d0 2979
ef50df4b 2980=item sv_setpvn
cb1a09d0 2981
ef50df4b
GS
2982Copies a string into an SV. The C<len> parameter indicates the number of
2983bytes to be copied. Does not handle 'set' magic. See C<sv_setpvn_mg>.
cb1a09d0 2984
ef50df4b 2985 void sv_setpvn (SV* sv, char* ptr, STRLEN len)
cb1a09d0 2986
ef50df4b 2987=item sv_setpvn_mg
189b2af5 2988
ef50df4b 2989Like C<sv_setpvn>, but also handles 'set' magic.
189b2af5 2990
ef50df4b 2991 void sv_setpvn_mg (SV* sv, char* ptr, STRLEN len)
189b2af5 2992
ef50df4b 2993=item sv_setpvf
cb1a09d0 2994
ef50df4b
GS
2995Processes its arguments like C<sprintf> and sets an SV to the formatted
2996output. Does not handle 'set' magic. See C<sv_setpvf_mg>.
cb1a09d0 2997
ef50df4b 2998 void sv_setpvf (SV* sv, const char* pat, ...)
cb1a09d0 2999
ef50df4b 3000=item sv_setpvf_mg
46fc3d4c 3001
ef50df4b 3002Like C<sv_setpvf>, but also handles 'set' magic.
46fc3d4c 3003
ef50df4b 3004 void sv_setpvf_mg (SV* sv, const char* pat, ...)
46fc3d4c 3005
cb1a09d0
AD
3006=item sv_setref_iv
3007
5fb8527f
PP
3008Copies an integer into a new SV, optionally blessing the SV. The C<rv>
3009argument will be upgraded to an RV. That RV will be modified to point to
3010the new SV. The C<classname> argument indicates the package for the
3011blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3012will be returned and will have a reference count of 1.
cb1a09d0 3013
ef50df4b 3014 SV* sv_setref_iv (SV *rv, char *classname, IV iv)
cb1a09d0
AD
3015
3016=item sv_setref_nv
3017
5fb8527f
PP
3018Copies a double into a new SV, optionally blessing the SV. The C<rv>
3019argument will be upgraded to an RV. That RV will be modified to point to
3020the new SV. The C<classname> argument indicates the package for the
3021blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3022will be returned and will have a reference count of 1.
cb1a09d0 3023
ef50df4b 3024 SV* sv_setref_nv (SV *rv, char *classname, double nv)
cb1a09d0
AD
3025
3026=item sv_setref_pv
3027
5fb8527f
PP
3028Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
3029argument will be upgraded to an RV. That RV will be modified to point to
3030the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
3031into the SV. The C<classname> argument indicates the package for the
3032blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 3033will be returned and will have a reference count of 1.
cb1a09d0 3034
ef50df4b 3035 SV* sv_setref_pv (SV *rv, char *classname, void* pv)
cb1a09d0
AD
3036
3037Do not use with integral Perl types such as HV, AV, SV, CV, because those
3038objects will become corrupted by the pointer copy process.
3039
3040Note that C<sv_setref_pvn> copies the string while this copies the pointer.
3041
3042=item sv_setref_pvn
3043
5fb8527f
PP
3044Copies a string into a new SV, optionally blessing the SV. The length of the
3045string must be specified with C<n>. The C<rv> argument will be upgraded to
3046an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
3047argument indicates the package for the blessing. Set C<classname> to
3048C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 3049a reference count of 1.
cb1a09d0 3050
ef50df4b 3051 SV* sv_setref_pvn (SV *rv, char *classname, char* pv, I32 n)
cb1a09d0
AD
3052
3053Note that C<sv_setref_pv> copies the pointer while this copies the string.
3054
189b2af5
GS
3055=item SvSetSV
3056
3057Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
3058more than once.
3059
3060 void SvSetSV (SV* dsv, SV* ssv)
3061
3062=item SvSetSV_nosteal
3063
3064Calls a non-destructive version of C<sv_setsv> if dsv is not the same as ssv.
3065May evaluate arguments more than once.
3066
3067 void SvSetSV_nosteal (SV* dsv, SV* ssv)
3068
cb1a09d0
AD
3069=item sv_setsv
3070
3071Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
189b2af5 3072The source SV may be destroyed if it is mortal. Does not handle 'set' magic.
ef50df4b
GS
3073See the macro forms C<SvSetSV>, C<SvSetSV_nosteal> and C<sv_setsv_mg>.
3074
3075 void sv_setsv (SV* dsv, SV* ssv)
3076
3077=item sv_setsv_mg
3078
3079Like C<sv_setsv>, but also handles 'set' magic.
cb1a09d0 3080
ef50df4b 3081 void sv_setsv_mg (SV* dsv, SV* ssv)
cb1a09d0 3082
189b2af5
GS
3083=item sv_setuv
3084
3085Copies an unsigned integer into the given SV. Does not handle 'set' magic.
ef50df4b 3086See C<sv_setuv_mg>.
189b2af5 3087
ef50df4b
GS
3088 void sv_setuv (SV* sv, UV num)
3089
3090=item sv_setuv_mg
3091
3092Like C<sv_setuv>, but also handles 'set' magic.
3093
3094 void sv_setuv_mg (SV* sv, UV num)
189b2af5 3095
cb1a09d0
AD
3096=item SvSTASH
3097
3098Returns the stash of the SV.
3099
3100 HV * SvSTASH (SV* sv)
3101
3102=item SVt_IV
3103
3104Integer type flag for scalars. See C<svtype>.
3105
3106=item SVt_PV
3107
3108Pointer type flag for scalars. See C<svtype>.
3109
3110=item SVt_PVAV
3111
3112Type flag for arrays. See C<svtype>.
3113
3114=item SVt_PVCV
3115
3116Type flag for code refs. See C<svtype>.
3117
3118=item SVt_PVHV
3119
3120Type flag for hashes. See C<svtype>.
3121
3122=item SVt_PVMG
3123
3124Type flag for blessed scalars. See C<svtype>.
3125
3126=item SVt_NV
3127
3128Double type flag for scalars. See C<svtype>.
3129
3130=item SvTRUE
3131
3132Returns a boolean indicating whether Perl would evaluate the SV as true or
189b2af5 3133false, defined or undefined. Does not handle 'get' magic.
cb1a09d0
AD
3134
3135 int SvTRUE (SV* sv)
3136
3137=item SvTYPE
3138
3139Returns the type of the SV. See C<svtype>.
3140
3141 svtype SvTYPE (SV* sv)
3142
3143=item svtype
3144
3145An enum of flags for Perl types. These are found in the file B<sv.h> in the
3146C<svtype> enum. Test these flags with the C<SvTYPE> macro.
3147
3148=item SvUPGRADE
3149
5fb8527f
PP
3150Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
3151the upgrade if necessary. See C<svtype>.
3152
ef50df4b 3153 bool SvUPGRADE (SV* sv, svtype mt)
5fb8527f
PP
3154
3155=item sv_upgrade
3156
3157Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
cb1a09d0
AD
3158
3159=item sv_undef
3160
3161This is the C<undef> SV. Always refer to this as C<&sv_undef>.
3162
5fb8527f
PP
3163=item sv_unref
3164
07fa94a1
JO
3165Unsets the RV status of the SV, and decrements the reference count of
3166whatever was being referenced by the RV. This can almost be thought of
3167as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f 3168
ef50df4b 3169 void sv_unref (SV* sv)
189b2af5 3170
cb1a09d0
AD
3171=item sv_usepvn
3172
3173Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
3174stored inside the SV but sv_usepvn allows the SV to use an outside string.
3175The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
3176string length, C<len>, must be supplied. This function will realloc the
3177memory pointed to by C<ptr>, so that pointer should not be freed or used by
189b2af5 3178the programmer after giving it to sv_usepvn. Does not handle 'set' magic.
ef50df4b
GS
3179See C<sv_usepvn_mg>.
3180
3181 void sv_usepvn (SV* sv, char* ptr, STRLEN len)
3182
3183=item sv_usepvn_mg
3184
3185Like C<sv_usepvn>, but also handles 'set' magic.
cb1a09d0 3186
ef50df4b 3187 void sv_usepvn_mg (SV* sv, char* ptr, STRLEN len)
cb1a09d0
AD
3188
3189=item sv_yes
3190
3191This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
3192
3193=item THIS
3194
3195Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
3196This is always the proper type for the C++ object. See C<CLASS> and
5fb8527f 3197L<perlxs/"Using XS With C++">.
cb1a09d0
AD
3198
3199=item toLOWER
3200
3201Converts the specified character to lowercase.
3202
3203 int toLOWER (char c)
3204
3205=item toUPPER
3206
3207Converts the specified character to uppercase.
3208
3209 int toUPPER (char c)
3210
3211=item warn
3212
3213This is the XSUB-writer's interface to Perl's C<warn> function. Use this
3214function the same way you use the C C<printf> function. See C<croak()>.
3215
3216=item XPUSHi
3217
189b2af5
GS
3218Push an integer onto the stack, extending the stack if necessary. Handles
3219'set' magic. See C<PUSHi>.
cb1a09d0
AD
3220
3221 XPUSHi(int d)
3222
3223=item XPUSHn
3224
189b2af5
GS
3225Push a double onto the stack, extending the stack if necessary. Handles 'set'
3226magic. See C<PUSHn>.
cb1a09d0
AD
3227
3228 XPUSHn(double d)
3229
3230=item XPUSHp
3231
3232Push a string onto the stack, extending the stack if necessary. The C<len>
189b2af5 3233indicates the length of the string. Handles 'set' magic. See C<PUSHp>.
cb1a09d0
AD
3234
3235 XPUSHp(char *c, int len)
3236
3237=item XPUSHs
3238
189b2af5
GS
3239Push an SV onto the stack, extending the stack if necessary. Does not
3240handle 'set' magic. See C<PUSHs>.
cb1a09d0
AD
3241
3242 XPUSHs(sv)
3243
5fb8527f
PP
3244=item XS
3245
3246Macro to declare an XSUB and its C parameter list. This is handled by
3247C<xsubpp>.
3248
cb1a09d0
AD
3249=item XSRETURN
3250
3251Return from XSUB, indicating number of items on the stack. This is usually
3252handled by C<xsubpp>.
3253
ef50df4b 3254 XSRETURN(int x)
cb1a09d0
AD
3255
3256=item XSRETURN_EMPTY
3257
5fb8527f 3258Return an empty list from an XSUB immediately.
cb1a09d0
AD
3259
3260 XSRETURN_EMPTY;
3261
5fb8527f
PP
3262=item XSRETURN_IV
3263
3264Return an integer from an XSUB immediately. Uses C<XST_mIV>.
3265
ef50df4b 3266 XSRETURN_IV(IV v)
5fb8527f 3267
cb1a09d0
AD
3268=item XSRETURN_NO
3269
5fb8527f 3270Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
cb1a09d0
AD
3271
3272 XSRETURN_NO;
3273
5fb8527f
PP
3274=item XSRETURN_NV
3275
3276Return an double from an XSUB immediately. Uses C<XST_mNV>.
3277
ef50df4b 3278 XSRETURN_NV(NV v)
5fb8527f
PP
3279
3280=item XSRETURN_PV
3281
3282Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
3283
ef50df4b 3284 XSRETURN_PV(char *v)
5fb8527f 3285
cb1a09d0
AD
3286=item XSRETURN_UNDEF
3287
5fb8527f 3288Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
cb1a09d0
AD
3289
3290 XSRETURN_UNDEF;
3291
3292=item XSRETURN_YES
3293
5fb8527f 3294Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
cb1a09d0
AD
3295
3296 XSRETURN_YES;
3297
5fb8527f
PP
3298=item XST_mIV
3299
3300Place an integer into the specified position C<i> on the stack. The value is
3301stored in a new mortal SV.
3302
ef50df4b 3303 XST_mIV( int i, IV v )
5fb8527f
PP
3304
3305=item XST_mNV
3306
3307Place a double into the specified position C<i> on the stack. The value is
3308stored in a new mortal SV.
3309
ef50df4b 3310 XST_mNV( int i, NV v )
5fb8527f
PP
3311
3312=item XST_mNO
3313
3314Place C<&sv_no> into the specified position C<i> on the stack.
3315
ef50df4b 3316 XST_mNO( int i )
5fb8527f
PP
3317
3318=item XST_mPV
3319
3320Place a copy of a string into the specified position C<i> on the stack. The
3321value is stored in a new mortal SV.
3322
ef50df4b 3323 XST_mPV( int i, char *v )
5fb8527f
PP
3324
3325=item XST_mUNDEF
3326
3327Place C<&sv_undef> into the specified position C<i> on the stack.
3328
ef50df4b 3329 XST_mUNDEF( int i )
5fb8527f
PP
3330
3331=item XST_mYES
3332
3333Place C<&sv_yes> into the specified position C<i> on the stack.
3334
ef50df4b 3335 XST_mYES( int i )
5fb8527f
PP
3336
3337=item XS_VERSION
3338
3339The version identifier for an XS module. This is usually handled
3340automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
3341
3342=item XS_VERSION_BOOTCHECK
3343
3344Macro to verify that a PM module's $VERSION variable matches the XS module's
3345C<XS_VERSION> variable. This is usually handled automatically by
3346C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
3347
cb1a09d0
AD
3348=item Zero
3349
3350The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
3351destination, C<n> is the number of items, and C<t> is the type.
3352
ef50df4b 3353 (void) Zero( d, n, t )
cb1a09d0
AD
3354
3355=back
3356
5f05dabc 3357=head1 EDITOR
cb1a09d0 3358
9607fc9c 3359Jeff Okamoto <F<okamoto@corp.hp.com>>
cb1a09d0
AD
3360
3361With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
3362Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
189b2af5
GS
3363Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
3364Stephen McCamant, and Gurusamy Sarathy.
cb1a09d0 3365
9607fc9c 3366API Listing by Dean Roehrich <F<roehrich@cray.com>>.
cb1a09d0
AD
3367
3368=head1 DATE
3369
04343c6d 3370Version 31.8: 1997/5/17