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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
5f05dabc 31=head2 Working with SV's
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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
37The four routines are:
38
39 SV* newSViv(IV);
40 SV* newSVnv(double);
41 SV* newSVpv(char*, int);
42 SV* newSVsv(SV*);
43
5fb8527f 44To change the value of an *already-existing* SV, there are five routines:
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45
46 void sv_setiv(SV*, IV);
47 void sv_setnv(SV*, double);
48 void sv_setpvn(SV*, char*, int)
49 void sv_setpv(SV*, char*);
50 void sv_setsv(SV*, SV*);
51
52Notice that you can choose to specify the length of the string to be
d1b91892 53assigned by using C<sv_setpvn> or C<newSVpv>, or you may allow Perl to
cb1a09d0 54calculate the length by using C<sv_setpv> or by specifying 0 as the second
d1b91892 55argument to C<newSVpv>. Be warned, though, that Perl will determine the
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56string's length by using C<strlen>, which depends on the string terminating
57with a NUL character.
58
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59All SV's that will contain strings should, but need not, be terminated
60with a NUL character. If it is not NUL-terminated there is a risk of
61core dumps and corruptions from code which passes the string to C
62functions or system calls which expect a NUL-terminated string.
63Perl's own functions typically add a trailing NUL for this reason.
64Nevertheless, you should be very careful when you pass a string stored
65in an SV to a C function or system call.
66
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67To access the actual value that an SV points to, you can use the macros:
68
69 SvIV(SV*)
70 SvNV(SV*)
71 SvPV(SV*, STRLEN len)
72
73which will automatically coerce the actual scalar type into an IV, double,
74or string.
75
76In the C<SvPV> macro, the length of the string returned is placed into the
77variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
78care what the length of the data is, use the global variable C<na>. Remember,
79however, that Perl allows arbitrary strings of data that may both contain
5f05dabc 80NUL's and might not be terminated by a NUL.
a0d0e21e 81
07fa94a1 82If you want to know if the scalar value is TRUE, you can use:
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83
84 SvTRUE(SV*)
85
86Although Perl will automatically grow strings for you, if you need to force
87Perl to allocate more memory for your SV, you can use the macro
88
89 SvGROW(SV*, STRLEN newlen)
90
91which will determine if more memory needs to be allocated. If so, it will
92call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
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93decrease, the allocated memory of an SV and that it does not automatically
94add a byte for the a trailing NUL (perl's own string functions typically do
8ebc5c01 95C<SvGROW(sv, len + 1)>).
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96
97If you have an SV and want to know what kind of data Perl thinks is stored
98in it, you can use the following macros to check the type of SV you have.
99
100 SvIOK(SV*)
101 SvNOK(SV*)
102 SvPOK(SV*)
103
104You can get and set the current length of the string stored in an SV with
105the following macros:
106
107 SvCUR(SV*)
108 SvCUR_set(SV*, I32 val)
109
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110You can also get a pointer to the end of the string stored in the SV
111with the macro:
112
113 SvEND(SV*)
114
115But note that these last three macros are valid only if C<SvPOK()> is true.
a0d0e21e 116
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117If you want to append something to the end of string stored in an C<SV*>,
118you can use the following functions:
119
120 void sv_catpv(SV*, char*);
121 void sv_catpvn(SV*, char*, int);
122 void sv_catsv(SV*, SV*);
123
124The first function calculates the length of the string to be appended by
125using C<strlen>. In the second, you specify the length of the string
126yourself. The third function extends the string stored in the first SV
127with the string stored in the second SV. It also forces the second SV to
128be interpreted as a string.
129
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130If you know the name of a scalar variable, you can get a pointer to its SV
131by using the following:
132
5f05dabc 133 SV* perl_get_sv("package::varname", FALSE);
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134
135This returns NULL if the variable does not exist.
136
d1b91892 137If you want to know if this variable (or any other SV) is actually C<defined>,
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138you can call:
139
140 SvOK(SV*)
141
142The scalar C<undef> value is stored in an SV instance called C<sv_undef>. Its
143address can be used whenever an C<SV*> is needed.
144
145There are also the two values C<sv_yes> and C<sv_no>, which contain Boolean
146TRUE and FALSE values, respectively. Like C<sv_undef>, their addresses can
147be used whenever an C<SV*> is needed.
148
149Do not be fooled into thinking that C<(SV *) 0> is the same as C<&sv_undef>.
150Take this code:
151
152 SV* sv = (SV*) 0;
153 if (I-am-to-return-a-real-value) {
154 sv = sv_2mortal(newSViv(42));
155 }
156 sv_setsv(ST(0), sv);
157
158This code tries to return a new SV (which contains the value 42) if it should
159return a real value, or undef otherwise. Instead it has returned a null
160pointer which, somewhere down the line, will cause a segmentation violation,
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161bus error, or just weird results. Change the zero to C<&sv_undef> in the first
162line and all will be well.
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163
164To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
3fe9a6f1 165call is not necessary (see L<Reference Counts and Mortality>).
a0d0e21e 166
d1b91892 167=head2 What's Really Stored in an SV?
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168
169Recall that the usual method of determining the type of scalar you have is
5f05dabc 170to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
d1b91892 171usually these macros will always return TRUE and calling the C<Sv*V>
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172macros will do the appropriate conversion of string to integer/double or
173integer/double to string.
174
175If you I<really> need to know if you have an integer, double, or string
176pointer in an SV, you can use the following three macros instead:
177
178 SvIOKp(SV*)
179 SvNOKp(SV*)
180 SvPOKp(SV*)
181
182These will tell you if you truly have an integer, double, or string pointer
d1b91892 183stored in your SV. The "p" stands for private.
a0d0e21e 184
07fa94a1 185In general, though, it's best to use the C<Sv*V> macros.
a0d0e21e 186
5f05dabc 187=head2 Working with AV's
a0d0e21e 188
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189There are two ways to create and load an AV. The first method creates an
190empty AV:
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191
192 AV* newAV();
193
5f05dabc 194The second method both creates the AV and initially populates it with SV's:
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195
196 AV* av_make(I32 num, SV **ptr);
197
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198The second argument points to an array containing C<num> C<SV*>'s. Once the
199AV has been created, the SV's can be destroyed, if so desired.
a0d0e21e 200
5f05dabc 201Once the AV has been created, the following operations are possible on AV's:
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202
203 void av_push(AV*, SV*);
204 SV* av_pop(AV*);
205 SV* av_shift(AV*);
206 void av_unshift(AV*, I32 num);
207
208These should be familiar operations, with the exception of C<av_unshift>.
209This routine adds C<num> elements at the front of the array with the C<undef>
210value. You must then use C<av_store> (described below) to assign values
211to these new elements.
212
213Here are some other functions:
214
5f05dabc 215 I32 av_len(AV*);
a0d0e21e 216 SV** av_fetch(AV*, I32 key, I32 lval);
a0d0e21e 217 SV** av_store(AV*, I32 key, SV* val);
a0d0e21e 218
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219The C<av_len> function returns the highest index value in array (just
220like $#array in Perl). If the array is empty, -1 is returned. The
221C<av_fetch> function returns the value at index C<key>, but if C<lval>
222is non-zero, then C<av_fetch> will store an undef value at that index.
223The C<av_store> function stores the value C<val> at index C<key>.
224note that C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s
225as their return value.
d1b91892 226
a0d0e21e 227 void av_clear(AV*);
a0d0e21e 228 void av_undef(AV*);
cb1a09d0 229 void av_extend(AV*, I32 key);
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230
231The C<av_clear> function deletes all the elements in the AV* array, but
232does not actually delete the array itself. The C<av_undef> function will
233delete all the elements in the array plus the array itself. The
234C<av_extend> function extends the array so that it contains C<key>
235elements. If C<key> is less than the current length of the array, then
236nothing is done.
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237
238If you know the name of an array variable, you can get a pointer to its AV
239by using the following:
240
5f05dabc 241 AV* perl_get_av("package::varname", FALSE);
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242
243This returns NULL if the variable does not exist.
244
5f05dabc 245=head2 Working with HV's
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246
247To create an HV, you use the following routine:
248
249 HV* newHV();
250
5f05dabc 251Once the HV has been created, the following operations are possible on HV's:
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252
253 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
254 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
255
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256The C<klen> parameter is the length of the key being passed in (Note that
257you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
258length of the key). The C<val> argument contains the SV pointer to the
259scalar being stored, and C<hash> is the pre-computed hash value (zero if
260you want C<hv_store> to calculate it for you). The C<lval> parameter
261indicates whether this fetch is actually a part of a store operation, in
262which case a new undefined value will be added to the HV with the supplied
263key and C<hv_fetch> will return as if the value had already existed.
a0d0e21e 264
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265Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
266C<SV*>. To access the scalar value, you must first dereference the return
267value. However, you should check to make sure that the return value is
268not NULL before dereferencing it.
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269
270These two functions check if a hash table entry exists, and deletes it.
271
272 bool hv_exists(HV*, char* key, U32 klen);
d1b91892 273 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
a0d0e21e 274
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275If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
276create and return a mortal copy of the deleted value.
277
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278And more miscellaneous functions:
279
280 void hv_clear(HV*);
a0d0e21e 281 void hv_undef(HV*);
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282
283Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
284table but does not actually delete the hash table. The C<hv_undef> deletes
285both the entries and the hash table itself.
a0d0e21e 286
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287Perl keeps the actual data in linked list of structures with a typedef of HE.
288These contain the actual key and value pointers (plus extra administrative
289overhead). The key is a string pointer; the value is an C<SV*>. However,
290once you have an C<HE*>, to get the actual key and value, use the routines
291specified below.
292
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293 I32 hv_iterinit(HV*);
294 /* Prepares starting point to traverse hash table */
295 HE* hv_iternext(HV*);
296 /* Get the next entry, and return a pointer to a
297 structure that has both the key and value */
298 char* hv_iterkey(HE* entry, I32* retlen);
299 /* Get the key from an HE structure and also return
300 the length of the key string */
cb1a09d0 301 SV* hv_iterval(HV*, HE* entry);
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302 /* Return a SV pointer to the value of the HE
303 structure */
cb1a09d0 304 SV* hv_iternextsv(HV*, char** key, I32* retlen);
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305 /* This convenience routine combines hv_iternext,
306 hv_iterkey, and hv_iterval. The key and retlen
307 arguments are return values for the key and its
308 length. The value is returned in the SV* argument */
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309
310If you know the name of a hash variable, you can get a pointer to its HV
311by using the following:
312
5f05dabc 313 HV* perl_get_hv("package::varname", FALSE);
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314
315This returns NULL if the variable does not exist.
316
8ebc5c01 317The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
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318
319 i = klen;
320 hash = 0;
321 s = key;
322 while (i--)
323 hash = hash * 33 + *s++;
324
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325=head2 Hash API Extensions
326
327Beginning with version 5.004, the following functions are also supported:
328
329 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
330 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
331
332 bool hv_exists_ent (HV* tb, SV* key, U32 hash);
333 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
334
335 SV* hv_iterkeysv (HE* entry);
336
337Note that these functions take C<SV*> keys, which simplifies writing
338of extension code that deals with hash structures. These functions
339also allow passing of C<SV*> keys to C<tie> functions without forcing
340you to stringify the keys (unlike the previous set of functions).
341
342They also return and accept whole hash entries (C<HE*>), making their
343use more efficient (since the hash number for a particular string
344doesn't have to be recomputed every time). See L<API LISTING> later in
345this document for detailed descriptions.
346
347The following macros must always be used to access the contents of hash
348entries. Note that the arguments to these macros must be simple
349variables, since they may get evaluated more than once. See
350L<API LISTING> later in this document for detailed descriptions of these
351macros.
352
353 HePV(HE* he, STRLEN len)
354 HeVAL(HE* he)
355 HeHASH(HE* he)
356 HeSVKEY(HE* he)
357 HeSVKEY_force(HE* he)
358 HeSVKEY_set(HE* he, SV* sv)
359
360These two lower level macros are defined, but must only be used when
361dealing with keys that are not C<SV*>s:
362
363 HeKEY(HE* he)
364 HeKLEN(HE* he)
365
366
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367=head2 References
368
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369References are a special type of scalar that point to other data types
370(including references).
a0d0e21e 371
07fa94a1 372To create a reference, use either of the following functions:
a0d0e21e 373
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374 SV* newRV_inc((SV*) thing);
375 SV* newRV_noinc((SV*) thing);
a0d0e21e 376
5f05dabc 377The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
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378functions are identical except that C<newRV_inc> increments the reference
379count of the C<thing>, while C<newRV_noinc> does not. For historical
380reasons, C<newRV> is a synonym for C<newRV_inc>.
381
382Once you have a reference, you can use the following macro to dereference
383the reference:
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384
385 SvRV(SV*)
386
387then call the appropriate routines, casting the returned C<SV*> to either an
d1b91892 388C<AV*> or C<HV*>, if required.
a0d0e21e 389
d1b91892 390To determine if an SV is a reference, you can use the following macro:
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391
392 SvROK(SV*)
393
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394To discover what type of value the reference refers to, use the following
395macro and then check the return value.
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396
397 SvTYPE(SvRV(SV*))
398
399The most useful types that will be returned are:
400
401 SVt_IV Scalar
402 SVt_NV Scalar
403 SVt_PV Scalar
5f05dabc 404 SVt_RV Scalar
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405 SVt_PVAV Array
406 SVt_PVHV Hash
407 SVt_PVCV Code
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408 SVt_PVGV Glob (possible a file handle)
409 SVt_PVMG Blessed or Magical Scalar
410
411 See the sv.h header file for more details.
d1b91892 412
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413=head2 Blessed References and Class Objects
414
415References are also used to support object-oriented programming. In the
416OO lexicon, an object is simply a reference that has been blessed into a
417package (or class). Once blessed, the programmer may now use the reference
418to access the various methods in the class.
419
420A reference can be blessed into a package with the following function:
421
422 SV* sv_bless(SV* sv, HV* stash);
423
424The C<sv> argument must be a reference. The C<stash> argument specifies
3fe9a6f1 425which class the reference will belong to. See
2ae324a7 426L<Stashes and Globs> for information on converting class names into stashes.
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427
428/* Still under construction */
429
430Upgrades rv to reference if not already one. Creates new SV for rv to
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431point to. If C<classname> is non-null, the SV is blessed into the specified
432class. SV is returned.
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433
434 SV* newSVrv(SV* rv, char* classname);
435
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436Copies integer or double into an SV whose reference is C<rv>. SV is blessed
437if C<classname> is non-null.
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438
439 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
440 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
441
5f05dabc 442Copies the pointer value (I<the address, not the string!>) into an SV whose
8ebc5c01 443reference is rv. SV is blessed if C<classname> is non-null.
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444
445 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
446
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447Copies string into an SV whose reference is C<rv>. Set length to 0 to let
448Perl calculate the string length. SV is blessed if C<classname> is non-null.
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449
450 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
451
452 int sv_isa(SV* sv, char* name);
453 int sv_isobject(SV* sv);
454
5f05dabc 455=head2 Creating New Variables
cb1a09d0 456
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457To create a new Perl variable with an undef value which can be accessed from
458your Perl script, use the following routines, depending on the variable type.
cb1a09d0 459
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460 SV* perl_get_sv("package::varname", TRUE);
461 AV* perl_get_av("package::varname", TRUE);
462 HV* perl_get_hv("package::varname", TRUE);
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463
464Notice the use of TRUE as the second parameter. The new variable can now
465be set, using the routines appropriate to the data type.
466
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467There are additional macros whose values may be bitwise OR'ed with the
468C<TRUE> argument to enable certain extra features. Those bits are:
cb1a09d0 469
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470 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
471 "Indentifier <varname> used only once: possible typo" warning.
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472 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
473 the variable did not exist before the function was called.
cb1a09d0 474
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475If you do not specify a package name, the variable is created in the current
476package.
cb1a09d0 477
5f05dabc 478=head2 Reference Counts and Mortality
a0d0e21e 479
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480Perl uses an reference count-driven garbage collection mechanism. SV's,
481AV's, or HV's (xV for short in the following) start their life with a
482reference count of 1. If the reference count of an xV ever drops to 0,
07fa94a1 483then it will be destroyed and its memory made available for reuse.
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484
485This normally doesn't happen at the Perl level unless a variable is
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486undef'ed or the last variable holding a reference to it is changed or
487overwritten. At the internal level, however, reference counts can be
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488manipulated with the following macros:
489
490 int SvREFCNT(SV* sv);
5f05dabc 491 SV* SvREFCNT_inc(SV* sv);
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492 void SvREFCNT_dec(SV* sv);
493
494However, there is one other function which manipulates the reference
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495count of its argument. The C<newRV_inc> function, you will recall,
496creates a reference to the specified argument. As a side effect,
497it increments the argument's reference count. If this is not what
498you want, use C<newRV_noinc> instead.
499
500For example, imagine you want to return a reference from an XSUB function.
501Inside the XSUB routine, you create an SV which initially has a reference
502count of one. Then you call C<newRV_inc>, passing it the just-created SV.
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503This returns the reference as a new SV, but the reference count of the
504SV you passed to C<newRV_inc> has been incremented to two. Now you
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505return the reference from the XSUB routine and forget about the SV.
506But Perl hasn't! Whenever the returned reference is destroyed, the
507reference count of the original SV is decreased to one and nothing happens.
508The SV will hang around without any way to access it until Perl itself
509terminates. This is a memory leak.
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510
511The correct procedure, then, is to use C<newRV_noinc> instead of
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512C<newRV_inc>. Then, if and when the last reference is destroyed,
513the reference count of the SV will go to zero and it will be destroyed,
07fa94a1 514stopping any memory leak.
55497cff 515
5f05dabc 516There are some convenience functions available that can help with the
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517destruction of xV's. These functions introduce the concept of "mortality".
518An xV that is mortal has had its reference count marked to be decremented,
519but not actually decremented, until "a short time later". Generally the
520term "short time later" means a single Perl statement, such as a call to
521an XSUB function. The actual determinant for when mortal xV's have their
522reference count decremented depends on two macros, SAVETMPS and FREETMPS.
523See L<perlcall> and L<perlxs> for more details on these macros.
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524
525"Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
526However, if you mortalize a variable twice, the reference count will
527later be decremented twice.
528
529You should be careful about creating mortal variables. Strange things
530can happen if you make the same value mortal within multiple contexts,
5f05dabc 531or if you make a variable mortal multiple times.
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532
533To create a mortal variable, use the functions:
534
535 SV* sv_newmortal()
536 SV* sv_2mortal(SV*)
537 SV* sv_mortalcopy(SV*)
538
5f05dabc
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539The first call creates a mortal SV, the second converts an existing
540SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
541third creates a mortal copy of an existing SV.
a0d0e21e 542
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543The mortal routines are not just for SV's -- AV's and HV's can be
544made mortal by passing their address (type-casted to C<SV*>) to the
07fa94a1 545C<sv_2mortal> or C<sv_mortalcopy> routines.
a0d0e21e 546
5f05dabc 547=head2 Stashes and Globs
a0d0e21e 548
aa689395
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549A "stash" is a hash that contains all of the different objects that
550are contained within a package. Each key of the stash is a symbol
551name (shared by all the different types of objects that have the same
552name), and each value in the hash table is a GV (Glob Value). This GV
553in turn contains references to the various objects of that name,
554including (but not limited to) the following:
cb1a09d0 555
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556 Scalar Value
557 Array Value
558 Hash Value
559 File Handle
560 Directory Handle
561 Format
562 Subroutine
563
5f05dabc
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564There is a single stash called "defstash" that holds the items that exist
565in the "main" package. To get at the items in other packages, append the
566string "::" to the package name. The items in the "Foo" package are in
567the stash "Foo::" in defstash. The items in the "Bar::Baz" package are
568in the stash "Baz::" in "Bar::"'s stash.
a0d0e21e 569
d1b91892 570To get the stash pointer for a particular package, use the function:
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571
572 HV* gv_stashpv(char* name, I32 create)
573 HV* gv_stashsv(SV*, I32 create)
574
575The first function takes a literal string, the second uses the string stored
d1b91892 576in the SV. Remember that a stash is just a hash table, so you get back an
cb1a09d0 577C<HV*>. The C<create> flag will create a new package if it is set.
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578
579The name that C<gv_stash*v> wants is the name of the package whose symbol table
580you want. The default package is called C<main>. If you have multiply nested
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581packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
582language itself.
a0d0e21e
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583
584Alternately, if you have an SV that is a blessed reference, you can find
585out the stash pointer by using:
586
587 HV* SvSTASH(SvRV(SV*));
588
589then use the following to get the package name itself:
590
591 char* HvNAME(HV* stash);
592
5f05dabc
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593If you need to bless or re-bless an object you can use the following
594function:
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595
596 SV* sv_bless(SV*, HV* stash)
597
598where the first argument, an C<SV*>, must be a reference, and the second
599argument is a stash. The returned C<SV*> can now be used in the same way
600as any other SV.
601
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602For more information on references and blessings, consult L<perlref>.
603
0a753a76
PP
604=head2 Double-Typed SV's
605
606Scalar variables normally contain only one type of value, an integer,
607double, pointer, or reference. Perl will automatically convert the
608actual scalar data from the stored type into the requested type.
609
610Some scalar variables contain more than one type of scalar data. For
611example, the variable C<$!> contains either the numeric value of C<errno>
612or its string equivalent from either C<strerror> or C<sys_errlist[]>.
613
614To force multiple data values into an SV, you must do two things: use the
615C<sv_set*v> routines to add the additional scalar type, then set a flag
616so that Perl will believe it contains more than one type of data. The
617four macros to set the flags are:
618
619 SvIOK_on
620 SvNOK_on
621 SvPOK_on
622 SvROK_on
623
624The particular macro you must use depends on which C<sv_set*v> routine
625you called first. This is because every C<sv_set*v> routine turns on
626only the bit for the particular type of data being set, and turns off
627all the rest.
628
629For example, to create a new Perl variable called "dberror" that contains
630both the numeric and descriptive string error values, you could use the
631following code:
632
633 extern int dberror;
634 extern char *dberror_list;
635
636 SV* sv = perl_get_sv("dberror", TRUE);
637 sv_setiv(sv, (IV) dberror);
638 sv_setpv(sv, dberror_list[dberror]);
639 SvIOK_on(sv);
640
641If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
642macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
643
644=head2 Magic Variables
a0d0e21e 645
d1b91892
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646[This section still under construction. Ignore everything here. Post no
647bills. Everything not permitted is forbidden.]
648
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649Any SV may be magical, that is, it has special features that a normal
650SV does not have. These features are stored in the SV structure in a
5f05dabc 651linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
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652
653 struct magic {
654 MAGIC* mg_moremagic;
655 MGVTBL* mg_virtual;
656 U16 mg_private;
657 char mg_type;
658 U8 mg_flags;
659 SV* mg_obj;
660 char* mg_ptr;
661 I32 mg_len;
662 };
663
664Note this is current as of patchlevel 0, and could change at any time.
665
666=head2 Assigning Magic
667
668Perl adds magic to an SV using the sv_magic function:
669
670 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
671
672The C<sv> argument is a pointer to the SV that is to acquire a new magical
673feature.
674
675If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
676set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
677it to the beginning of the linked list of magical features. Any prior
678entry of the same type of magic is deleted. Note that this can be
5fb8527f 679overridden, and multiple instances of the same type of magic can be
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680associated with an SV.
681
682The C<name> and C<namlem> arguments are used to associate a string with
683the magic, typically the name of a variable. C<namlem> is stored in the
55497cff 684C<mg_len> field and if C<name> is non-null and C<namlem> >= 0 a malloc'd
d1b91892
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685copy of the name is stored in C<mg_ptr> field.
686
687The sv_magic function uses C<how> to determine which, if any, predefined
688"Magic Virtual Table" should be assigned to the C<mg_virtual> field.
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689See the "Magic Virtual Table" section below. The C<how> argument is also
690stored in the C<mg_type> field.
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691
692The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
693structure. If it is not the same as the C<sv> argument, the reference
694count of the C<obj> object is incremented. If it is the same, or if
695the C<how> argument is "#", or if it is a null pointer, then C<obj> is
696merely stored, without the reference count being incremented.
697
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698There is also a function to add magic to an C<HV>:
699
700 void hv_magic(HV *hv, GV *gv, int how);
701
702This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
703
704To remove the magic from an SV, call the function sv_unmagic:
705
706 void sv_unmagic(SV *sv, int type);
707
708The C<type> argument should be equal to the C<how> value when the C<SV>
709was initially made magical.
710
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711=head2 Magic Virtual Tables
712
713The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
714C<MGVTBL>, which is a structure of function pointers and stands for
715"Magic Virtual Table" to handle the various operations that might be
716applied to that variable.
717
718The C<MGVTBL> has five pointers to the following routine types:
719
720 int (*svt_get)(SV* sv, MAGIC* mg);
721 int (*svt_set)(SV* sv, MAGIC* mg);
722 U32 (*svt_len)(SV* sv, MAGIC* mg);
723 int (*svt_clear)(SV* sv, MAGIC* mg);
724 int (*svt_free)(SV* sv, MAGIC* mg);
725
726This MGVTBL structure is set at compile-time in C<perl.h> and there are
727currently 19 types (or 21 with overloading turned on). These different
728structures contain pointers to various routines that perform additional
729actions depending on which function is being called.
730
731 Function pointer Action taken
732 ---------------- ------------
733 svt_get Do something after the value of the SV is retrieved.
734 svt_set Do something after the SV is assigned a value.
735 svt_len Report on the SV's length.
736 svt_clear Clear something the SV represents.
737 svt_free Free any extra storage associated with the SV.
738
739For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
740to an C<mg_type> of '\0') contains:
741
742 { magic_get, magic_set, magic_len, 0, 0 }
743
744Thus, when an SV is determined to be magical and of type '\0', if a get
745operation is being performed, the routine C<magic_get> is called. All
746the various routines for the various magical types begin with C<magic_>.
747
748The current kinds of Magic Virtual Tables are:
749
07fa94a1 750 mg_type MGVTBL Type of magical
5f05dabc 751 ------- ------ ----------------------------
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AD
752 \0 vtbl_sv Regexp???
753 A vtbl_amagic Operator Overloading
754 a vtbl_amagicelem Operator Overloading
755 c 0 Used in Operator Overloading
756 B vtbl_bm Boyer-Moore???
757 E vtbl_env %ENV hash
758 e vtbl_envelem %ENV hash element
759 g vtbl_mglob Regexp /g flag???
760 I vtbl_isa @ISA array
761 i vtbl_isaelem @ISA array element
762 L 0 (but sets RMAGICAL) Perl Module/Debugger???
763 l vtbl_dbline Debugger?
44a8e56a 764 o vtbl_collxfrm Locale transformation
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AD
765 P vtbl_pack Tied Array or Hash
766 p vtbl_packelem Tied Array or Hash element
767 q vtbl_packelem Tied Scalar or Handle
768 S vtbl_sig Signal Hash
769 s vtbl_sigelem Signal Hash element
770 t vtbl_taint Taintedness
771 U vtbl_uvar ???
772 v vtbl_vec Vector
773 x vtbl_substr Substring???
e616eb7b 774 y vtbl_itervar Shadow "foreach" iterator variable
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AD
775 * vtbl_glob GV???
776 # vtbl_arylen Array Length
777 . vtbl_pos $. scalar variable
5f05dabc 778 ~ None Used by certain extensions
d1b91892 779
68dc0745
PP
780When an uppercase and lowercase letter both exist in the table, then the
781uppercase letter is used to represent some kind of composite type (a list
782or a hash), and the lowercase letter is used to represent an element of
d1b91892
AD
783that composite type.
784
5f05dabc
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785The '~' magic type is defined specifically for use by extensions and
786will not be used by perl itself. Extensions can use ~ magic to 'attach'
787private information to variables (typically objects). This is especially
788useful because there is no way for normal perl code to corrupt this
789private information (unlike using extra elements of a hash object).
790
791Note that because multiple extensions may be using ~ magic it is
792important for extensions to take extra care with it. Typically only
793using it on objects blessed into the same class as the extension
794is sufficient. It may also be appropriate to add an I32 'signature'
795at the top of the private data area and check that.
796
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AD
797=head2 Finding Magic
798
799 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
800
801This routine returns a pointer to the C<MAGIC> structure stored in the SV.
802If the SV does not have that magical feature, C<NULL> is returned. Also,
803if the SV is not of type SVt_PVMG, Perl may core-dump.
804
805 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
806
807This routine checks to see what types of magic C<sv> has. If the mg_type
68dc0745
PP
808field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
809the mg_type field is changed to be the lowercase letter.
a0d0e21e 810
0a753a76 811=head1 Subroutines
a0d0e21e 812
68dc0745 813=head2 XSUBs and the Argument Stack
5f05dabc
PP
814
815The XSUB mechanism is a simple way for Perl programs to access C subroutines.
816An XSUB routine will have a stack that contains the arguments from the Perl
817program, and a way to map from the Perl data structures to a C equivalent.
818
819The stack arguments are accessible through the C<ST(n)> macro, which returns
820the C<n>'th stack argument. Argument 0 is the first argument passed in the
821Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
822an C<SV*> is used.
823
824Most of the time, output from the C routine can be handled through use of
825the RETVAL and OUTPUT directives. However, there are some cases where the
826argument stack is not already long enough to handle all the return values.
827An example is the POSIX tzname() call, which takes no arguments, but returns
828two, the local time zone's standard and summer time abbreviations.
829
830To handle this situation, the PPCODE directive is used and the stack is
831extended using the macro:
832
833 EXTEND(sp, num);
834
835where C<sp> is the stack pointer, and C<num> is the number of elements the
836stack should be extended by.
837
838Now that there is room on the stack, values can be pushed on it using the
839macros to push IV's, doubles, strings, and SV pointers respectively:
840
841 PUSHi(IV)
842 PUSHn(double)
843 PUSHp(char*, I32)
844 PUSHs(SV*)
845
846And now the Perl program calling C<tzname>, the two values will be assigned
847as in:
848
849 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
850
851An alternate (and possibly simpler) method to pushing values on the stack is
852to use the macros:
853
854 XPUSHi(IV)
855 XPUSHn(double)
856 XPUSHp(char*, I32)
857 XPUSHs(SV*)
858
859These macros automatically adjust the stack for you, if needed. Thus, you
860do not need to call C<EXTEND> to extend the stack.
861
862For more information, consult L<perlxs> and L<perlxstut>.
863
864=head2 Calling Perl Routines from within C Programs
a0d0e21e
LW
865
866There are four routines that can be used to call a Perl subroutine from
867within a C program. These four are:
868
869 I32 perl_call_sv(SV*, I32);
870 I32 perl_call_pv(char*, I32);
871 I32 perl_call_method(char*, I32);
872 I32 perl_call_argv(char*, I32, register char**);
873
d1b91892
AD
874The routine most often used is C<perl_call_sv>. The C<SV*> argument
875contains either the name of the Perl subroutine to be called, or a
876reference to the subroutine. The second argument consists of flags
877that control the context in which the subroutine is called, whether
878or not the subroutine is being passed arguments, how errors should be
879trapped, and how to treat return values.
a0d0e21e
LW
880
881All four routines return the number of arguments that the subroutine returned
882on the Perl stack.
883
d1b91892
AD
884When using any of these routines (except C<perl_call_argv>), the programmer
885must manipulate the Perl stack. These include the following macros and
886functions:
a0d0e21e
LW
887
888 dSP
889 PUSHMARK()
890 PUTBACK
891 SPAGAIN
892 ENTER
893 SAVETMPS
894 FREETMPS
895 LEAVE
896 XPUSH*()
cb1a09d0 897 POP*()
a0d0e21e 898
5f05dabc
PP
899For a detailed description of calling conventions from C to Perl,
900consult L<perlcall>.
a0d0e21e 901
5f05dabc 902=head2 Memory Allocation
a0d0e21e 903
5f05dabc
PP
904It is suggested that you use the version of malloc that is distributed
905with Perl. It keeps pools of various sizes of unallocated memory in
07fa94a1
JO
906order to satisfy allocation requests more quickly. However, on some
907platforms, it may cause spurious malloc or free errors.
d1b91892
AD
908
909 New(x, pointer, number, type);
910 Newc(x, pointer, number, type, cast);
911 Newz(x, pointer, number, type);
912
07fa94a1 913These three macros are used to initially allocate memory.
5f05dabc
PP
914
915The first argument C<x> was a "magic cookie" that was used to keep track
916of who called the macro, to help when debugging memory problems. However,
07fa94a1
JO
917the current code makes no use of this feature (most Perl developers now
918use run-time memory checkers), so this argument can be any number.
5f05dabc
PP
919
920The second argument C<pointer> should be the name of a variable that will
921point to the newly allocated memory.
d1b91892 922
d1b91892
AD
923The third and fourth arguments C<number> and C<type> specify how many of
924the specified type of data structure should be allocated. The argument
925C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
926should be used if the C<pointer> argument is different from the C<type>
927argument.
928
929Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
930to zero out all the newly allocated memory.
931
932 Renew(pointer, number, type);
933 Renewc(pointer, number, type, cast);
934 Safefree(pointer)
935
936These three macros are used to change a memory buffer size or to free a
937piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
938match those of C<New> and C<Newc> with the exception of not needing the
939"magic cookie" argument.
940
941 Move(source, dest, number, type);
942 Copy(source, dest, number, type);
943 Zero(dest, number, type);
944
945These three macros are used to move, copy, or zero out previously allocated
946memory. The C<source> and C<dest> arguments point to the source and
947destination starting points. Perl will move, copy, or zero out C<number>
948instances of the size of the C<type> data structure (using the C<sizeof>
949function).
a0d0e21e 950
5f05dabc 951=head2 PerlIO
ce3d39e2 952
5f05dabc
PP
953The most recent development releases of Perl has been experimenting with
954removing Perl's dependency on the "normal" standard I/O suite and allowing
955other stdio implementations to be used. This involves creating a new
956abstraction layer that then calls whichever implementation of stdio Perl
68dc0745 957was compiled with. All XSUBs should now use the functions in the PerlIO
5f05dabc
PP
958abstraction layer and not make any assumptions about what kind of stdio
959is being used.
960
961For a complete description of the PerlIO abstraction, consult L<perlapio>.
962
8ebc5c01 963=head2 Putting a C value on Perl stack
ce3d39e2
IZ
964
965A lot of opcodes (this is an elementary operation in the internal perl
966stack machine) put an SV* on the stack. However, as an optimization
967the corresponding SV is (usually) not recreated each time. The opcodes
968reuse specially assigned SVs (I<target>s) which are (as a corollary)
969not constantly freed/created.
970
0a753a76 971Each of the targets is created only once (but see
ce3d39e2
IZ
972L<Scratchpads and recursion> below), and when an opcode needs to put
973an integer, a double, or a string on stack, it just sets the
974corresponding parts of its I<target> and puts the I<target> on stack.
975
976The macro to put this target on stack is C<PUSHTARG>, and it is
977directly used in some opcodes, as well as indirectly in zillions of
978others, which use it via C<(X)PUSH[pni]>.
979
8ebc5c01 980=head2 Scratchpads
ce3d39e2 981
5f05dabc
PP
982The question remains on when the SV's which are I<target>s for opcodes
983are created. The answer is that they are created when the current unit --
984a subroutine or a file (for opcodes for statements outside of
985subroutines) -- is compiled. During this time a special anonymous Perl
ce3d39e2
IZ
986array is created, which is called a scratchpad for the current
987unit.
988
5f05dabc 989A scratchpad keeps SV's which are lexicals for the current unit and are
ce3d39e2
IZ
990targets for opcodes. One can deduce that an SV lives on a scratchpad
991by looking on its flags: lexicals have C<SVs_PADMY> set, and
992I<target>s have C<SVs_PADTMP> set.
993
5f05dabc
PP
994The correspondence between OP's and I<target>s is not 1-to-1. Different
995OP's in the compile tree of the unit can use the same target, if this
ce3d39e2
IZ
996would not conflict with the expected life of the temporary.
997
2ae324a7 998=head2 Scratchpads and recursion
ce3d39e2
IZ
999
1000In fact it is not 100% true that a compiled unit contains a pointer to
1001the scratchpad AV. In fact it contains a pointer to an AV of
1002(initially) one element, and this element is the scratchpad AV. Why do
1003we need an extra level of indirection?
1004
1005The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1006these can create several execution pointers going into the same
1007subroutine. For the subroutine-child not write over the temporaries
1008for the subroutine-parent (lifespan of which covers the call to the
1009child), the parent and the child should have different
1010scratchpads. (I<And> the lexicals should be separate anyway!)
1011
5f05dabc
PP
1012So each subroutine is born with an array of scratchpads (of length 1).
1013On each entry to the subroutine it is checked that the current
ce3d39e2
IZ
1014depth of the recursion is not more than the length of this array, and
1015if it is, new scratchpad is created and pushed into the array.
1016
1017The I<target>s on this scratchpad are C<undef>s, but they are already
1018marked with correct flags.
1019
0a753a76
PP
1020=head1 Compiled code
1021
1022=head2 Code tree
1023
1024Here we describe the internal form your code is converted to by
1025Perl. Start with a simple example:
1026
1027 $a = $b + $c;
1028
1029This is converted to a tree similar to this one:
1030
1031 assign-to
1032 / \
1033 + $a
1034 / \
1035 $b $c
1036
1037(but slightly more complicated). This tree reflect the way Perl
1038parsed your code, but has nothing to do with the execution order.
1039There is an additional "thread" going through the nodes of the tree
1040which shows the order of execution of the nodes. In our simplified
1041example above it looks like:
1042
1043 $b ---> $c ---> + ---> $a ---> assign-to
1044
1045But with the actual compile tree for C<$a = $b + $c> it is different:
1046some nodes I<optimized away>. As a corollary, though the actual tree
1047contains more nodes than our simplified example, the execution order
1048is the same as in our example.
1049
1050=head2 Examining the tree
1051
1052If you have your perl compiled for debugging (usually done with C<-D
1053optimize=-g> on C<Configure> command line), you may examine the
1054compiled tree by specifying C<-Dx> on the Perl command line. The
1055output takes several lines per node, and for C<$b+$c> it looks like
1056this:
1057
1058 5 TYPE = add ===> 6
1059 TARG = 1
1060 FLAGS = (SCALAR,KIDS)
1061 {
1062 TYPE = null ===> (4)
1063 (was rv2sv)
1064 FLAGS = (SCALAR,KIDS)
1065 {
1066 3 TYPE = gvsv ===> 4
1067 FLAGS = (SCALAR)
1068 GV = main::b
1069 }
1070 }
1071 {
1072 TYPE = null ===> (5)
1073 (was rv2sv)
1074 FLAGS = (SCALAR,KIDS)
1075 {
1076 4 TYPE = gvsv ===> 5
1077 FLAGS = (SCALAR)
1078 GV = main::c
1079 }
1080 }
1081
1082This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1083not optimized away (one per number in the left column). The immediate
1084children of the given node correspond to C<{}> pairs on the same level
1085of indentation, thus this listing corresponds to the tree:
1086
1087 add
1088 / \
1089 null null
1090 | |
1091 gvsv gvsv
1092
1093The execution order is indicated by C<===E<gt>> marks, thus it is C<3
10944 5 6> (node C<6> is not included into above listing), i.e.,
1095C<gvsv gvsv add whatever>.
1096
1097=head2 Compile pass 1: check routines
1098
1099The tree is created by the I<pseudo-compiler> while yacc code feeds it
1100the constructions it recognizes. Since yacc works bottom-up, so does
1101the first pass of perl compilation.
1102
1103What makes this pass interesting for perl developers is that some
1104optimization may be performed on this pass. This is optimization by
1105so-called I<check routines>. The correspondence between node names
1106and corresponding check routines is described in F<opcode.pl> (do not
1107forget to run C<make regen_headers> if you modify this file).
1108
1109A check routine is called when the node is fully constructed except
1110for the execution-order thread. Since at this time there is no
1111back-links to the currently constructed node, one can do most any
1112operation to the top-level node, including freeing it and/or creating
1113new nodes above/below it.
1114
1115The check routine returns the node which should be inserted into the
1116tree (if the top-level node was not modified, check routine returns
1117its argument).
1118
1119By convention, check routines have names C<ck_*>. They are usually
1120called from C<new*OP> subroutines (or C<convert>) (which in turn are
1121called from F<perly.y>).
1122
1123=head2 Compile pass 1a: constant folding
1124
1125Immediately after the check routine is called the returned node is
1126checked for being compile-time executable. If it is (the value is
1127judged to be constant) it is immediately executed, and a I<constant>
1128node with the "return value" of the corresponding subtree is
1129substituted instead. The subtree is deleted.
1130
1131If constant folding was not performed, the execution-order thread is
1132created.
1133
1134=head2 Compile pass 2: context propagation
1135
1136When a context for a part of compile tree is known, it is propagated
1137down through the tree. Aat this time the context can have 5 values
1138(instead of 2 for runtime context): void, boolean, scalar, list, and
1139lvalue. In contrast with the pass 1 this pass is processed from top
1140to bottom: a node's context determines the context for its children.
1141
1142Additional context-dependent optimizations are performed at this time.
1143Since at this moment the compile tree contains back-references (via
1144"thread" pointers), nodes cannot be free()d now. To allow
1145optimized-away nodes at this stage, such nodes are null()ified instead
1146of free()ing (i.e. their type is changed to OP_NULL).
1147
1148=head2 Compile pass 3: peephole optimization
1149
1150After the compile tree for a subroutine (or for an C<eval> or a file)
1151is created, an additional pass over the code is performed. This pass
1152is neither top-down or bottom-up, but in the execution order (with
1153additional compilications for conditionals). These optimizations are
1154done in the subroutine peep(). Optimizations performed at this stage
1155are subject to the same restrictions as in the pass 2.
1156
1157=head1 API LISTING
a0d0e21e 1158
cb1a09d0
AD
1159This is a listing of functions, macros, flags, and variables that may be
1160useful to extension writers or that may be found while reading other
1161extensions.
a0d0e21e 1162
cb1a09d0 1163=over 8
a0d0e21e 1164
cb1a09d0
AD
1165=item AvFILL
1166
1167See C<av_len>.
1168
1169=item av_clear
1170
1171Clears an array, making it empty.
1172
1173 void av_clear _((AV* ar));
1174
1175=item av_extend
1176
1177Pre-extend an array. The C<key> is the index to which the array should be
1178extended.
1179
1180 void av_extend _((AV* ar, I32 key));
1181
1182=item av_fetch
1183
1184Returns the SV at the specified index in the array. The C<key> is the
1185index. If C<lval> is set then the fetch will be part of a store. Check
1186that the return value is non-null before dereferencing it to a C<SV*>.
1187
1188 SV** av_fetch _((AV* ar, I32 key, I32 lval));
1189
1190=item av_len
1191
1192Returns the highest index in the array. Returns -1 if the array is empty.
1193
1194 I32 av_len _((AV* ar));
1195
1196=item av_make
1197
5fb8527f
PP
1198Creates a new AV and populates it with a list of SVs. The SVs are copied
1199into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1200will have a reference count of 1.
cb1a09d0
AD
1201
1202 AV* av_make _((I32 size, SV** svp));
1203
1204=item av_pop
1205
1206Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
1207empty.
1208
1209 SV* av_pop _((AV* ar));
1210
1211=item av_push
1212
5fb8527f
PP
1213Pushes an SV onto the end of the array. The array will grow automatically
1214to accommodate the addition.
cb1a09d0
AD
1215
1216 void av_push _((AV* ar, SV* val));
1217
1218=item av_shift
1219
1220Shifts an SV off the beginning of the array.
1221
1222 SV* av_shift _((AV* ar));
1223
1224=item av_store
1225
1226Stores an SV in an array. The array index is specified as C<key>. The
1227return value will be null if the operation failed, otherwise it can be
1228dereferenced to get the original C<SV*>.
1229
1230 SV** av_store _((AV* ar, I32 key, SV* val));
1231
1232=item av_undef
1233
1234Undefines the array.
1235
1236 void av_undef _((AV* ar));
1237
1238=item av_unshift
1239
5fb8527f
PP
1240Unshift an SV onto the beginning of the array. The array will grow
1241automatically to accommodate the addition.
cb1a09d0
AD
1242
1243 void av_unshift _((AV* ar, I32 num));
1244
1245=item CLASS
1246
1247Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1248constructor. This is always a C<char*>. See C<THIS> and
1249L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1250
1251=item Copy
1252
1253The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1254source, C<d> is the destination, C<n> is the number of items, and C<t> is
1255the type.
1256
1257 (void) Copy( s, d, n, t );
1258
1259=item croak
1260
1261This is the XSUB-writer's interface to Perl's C<die> function. Use this
1262function the same way you use the C C<printf> function. See C<warn>.
1263
1264=item CvSTASH
1265
1266Returns the stash of the CV.
1267
1268 HV * CvSTASH( SV* sv )
1269
1270=item DBsingle
1271
1272When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1273boolean which indicates whether subs are being single-stepped.
5fb8527f
PP
1274Single-stepping is automatically turned on after every step. This is the C
1275variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
cb1a09d0
AD
1276
1277=item DBsub
1278
1279When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f
PP
1280the SV which holds the name of the sub being debugged. This is the C
1281variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
cb1a09d0
AD
1282The sub name can be found by
1283
1284 SvPV( GvSV( DBsub ), na )
1285
5fb8527f
PP
1286=item DBtrace
1287
1288Trace variable used when Perl is run in debugging mode, with the B<-d>
1289switch. This is the C variable which corresponds to Perl's $DB::trace
1290variable. See C<DBsingle>.
1291
cb1a09d0
AD
1292=item dMARK
1293
5fb8527f
PP
1294Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1295C<dORIGMARK>.
cb1a09d0
AD
1296
1297=item dORIGMARK
1298
1299Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1300
5fb8527f
PP
1301=item dowarn
1302
1303The C variable which corresponds to Perl's $^W warning variable.
1304
cb1a09d0
AD
1305=item dSP
1306
5fb8527f 1307Declares a stack pointer variable, C<sp>, for the XSUB. See C<SP>.
cb1a09d0
AD
1308
1309=item dXSARGS
1310
1311Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1312usually handled automatically by C<xsubpp>. Declares the C<items> variable
1313to indicate the number of items on the stack.
1314
5fb8527f
PP
1315=item dXSI32
1316
1317Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1318handled automatically by C<xsubpp>.
1319
1320=item dXSI32
1321
1322Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1323handled automatically by C<xsubpp>.
1324
cb1a09d0
AD
1325=item ENTER
1326
1327Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1328
1329 ENTER;
1330
1331=item EXTEND
1332
1333Used to extend the argument stack for an XSUB's return values.
1334
1335 EXTEND( sp, int x );
1336
1337=item FREETMPS
1338
1339Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1340L<perlcall>.
1341
1342 FREETMPS;
1343
1344=item G_ARRAY
1345
1346Used to indicate array context. See C<GIMME> and L<perlcall>.
1347
1348=item G_DISCARD
1349
1350Indicates that arguments returned from a callback should be discarded. See
1351L<perlcall>.
1352
1353=item G_EVAL
1354
1355Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1356
1357=item GIMME
1358
1359The XSUB-writer's equivalent to Perl's C<wantarray>. Returns C<G_SCALAR> or
1360C<G_ARRAY> for scalar or array context.
1361
1362=item G_NOARGS
1363
1364Indicates that no arguments are being sent to a callback. See L<perlcall>.
1365
1366=item G_SCALAR
1367
1368Used to indicate scalar context. See C<GIMME> and L<perlcall>.
1369
faed5253
JO
1370=item gv_fetchmeth
1371
1372Returns the glob with the given C<name> and a defined subroutine or
9607fc9c
PP
1373C<NULL>. The glob lives in the given C<stash>, or in the stashes
1374accessable via @ISA and @<UNIVERSAL>.
faed5253 1375
9607fc9c 1376The argument C<level> should be either 0 or -1. If C<level==0>, as a
0a753a76
PP
1377side-effect creates a glob with the given C<name> in the given
1378C<stash> which in the case of success contains an alias for the
1379subroutine, and sets up caching info for this glob. Similarly for all
1380the searched stashes.
1381
9607fc9c
PP
1382This function grants C<"SUPER"> token as a postfix of the stash name.
1383
0a753a76
PP
1384The GV returned from C<gv_fetchmeth> may be a method cache entry,
1385which is not visible to Perl code. So when calling C<perl_call_sv>,
1386you should not use the GV directly; instead, you should use the
1387method's CV, which can be obtained from the GV with the C<GvCV> macro.
faed5253
JO
1388
1389 GV* gv_fetchmeth _((HV* stash, char* name, STRLEN len, I32 level));
1390
1391=item gv_fetchmethod
1392
1393Returns the glob which contains the subroutine to call to invoke the
1394method on the C<stash>. In fact in the presense of autoloading this may
1395be the glob for "AUTOLOAD". In this case the corresponing variable
1396$AUTOLOAD is already setup.
1397
1398Note that if you want to keep this glob for a long time, you need to
68dc0745 1399check for it being "AUTOLOAD", since at the later time the call
faed5253
JO
1400may load a different subroutine due to $AUTOLOAD changing its value.
1401Use the glob created via a side effect to do this.
1402
9607fc9c 1403This function grants C<"SUPER"> token as a prefix of the method name.
faed5253 1404
0a753a76
PP
1405Has the same side-effects and as C<gv_fetchmeth> with C<level==0>.
1406C<name> should be writable if contains C<':'> or C<'\''>.
1407The warning against passing the GV returned by C<gv_fetchmeth> to
1408C<perl_call_sv> apply equally to C<gv_fetchmethod>.
faed5253
JO
1409
1410 GV* gv_fetchmethod _((HV* stash, char* name));
1411
cb1a09d0
AD
1412=item gv_stashpv
1413
1414Returns a pointer to the stash for a specified package. If C<create> is set
1415then the package will be created if it does not already exist. If C<create>
1416is not set and the package does not exist then NULL is returned.
1417
1418 HV* gv_stashpv _((char* name, I32 create));
1419
1420=item gv_stashsv
1421
1422Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1423
1424 HV* gv_stashsv _((SV* sv, I32 create));
1425
e5581bf4 1426=item GvSV
cb1a09d0 1427
e5581bf4 1428Return the SV from the GV.
44a8e56a 1429
1e422769
PP
1430=item HEf_SVKEY
1431
1432This flag, used in the length slot of hash entries and magic
1433structures, specifies the structure contains a C<SV*> pointer where a
1434C<char*> pointer is to be expected. (For information only--not to be used).
1435
1e422769
PP
1436=item HeHASH
1437
1438Returns the computed hash (type C<U32>) stored in the hash entry.
1439
1440 HeHASH(HE* he)
1441
1442=item HeKEY
1443
1444Returns the actual pointer stored in the key slot of the hash entry.
1445The pointer may be either C<char*> or C<SV*>, depending on the value of
1446C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1447are usually preferable for finding the value of a key.
1448
1449 HeKEY(HE* he)
1450
1451=item HeKLEN
1452
1453If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1454holds an C<SV*> key. Otherwise, holds the actual length of the key.
1455Can be assigned to. The C<HePV()> macro is usually preferable for finding
1456key lengths.
1457
1458 HeKLEN(HE* he)
1459
1460=item HePV
1461
1462Returns the key slot of the hash entry as a C<char*> value, doing any
1463necessary dereferencing of possibly C<SV*> keys. The length of
1464the string is placed in C<len> (this is a macro, so do I<not> use
1465C<&len>). If you do not care about what the length of the key is,
1466you may use the global variable C<na>. Remember though, that hash
1467keys in perl are free to contain embedded nulls, so using C<strlen()>
1468or similar is not a good way to find the length of hash keys.
1469This is very similar to the C<SvPV()> macro described elsewhere in
1470this document.
1471
1472 HePV(HE* he, STRLEN len)
1473
1474=item HeSVKEY
1475
1476Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1477does not contain an C<SV*> key.
1478
1479 HeSVKEY(HE* he)
1480
1481=item HeSVKEY_force
1482
1483Returns the key as an C<SV*>. Will create and return a temporary
1484mortal C<SV*> if the hash entry contains only a C<char*> key.
1485
1486 HeSVKEY_force(HE* he)
1487
1488=item HeSVKEY_set
1489
1490Sets the key to a given C<SV*>, taking care to set the appropriate flags
1491to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1492
1493 HeSVKEY_set(HE* he, SV* sv)
1494
1495=item HeVAL
1496
1497Returns the value slot (type C<SV*>) stored in the hash entry.
1498
1499 HeVAL(HE* he)
1500
cb1a09d0
AD
1501=item hv_clear
1502
1503Clears a hash, making it empty.
1504
1505 void hv_clear _((HV* tb));
1506
68dc0745
PP
1507=item hv_delayfree_ent
1508
1509Releases a hash entry, such as while iterating though the hash, but
1510delays actual freeing of key and value until the end of the current
1511statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
1512and C<hv_free_ent>.
1513
1514 void hv_delayfree_ent _((HV* hv, HE* entry));
1515
cb1a09d0
AD
1516=item hv_delete
1517
1518Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 1519and returned to the caller. The C<klen> is the length of the key. The
cb1a09d0
AD
1520C<flags> value will normally be zero; if set to G_DISCARD then null will be
1521returned.
1522
1523 SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));
1524
1e422769
PP
1525=item hv_delete_ent
1526
1527Deletes a key/value pair in the hash. The value SV is removed from the hash
1528and returned to the caller. The C<flags> value will normally be zero; if set
1529to G_DISCARD then null will be returned. C<hash> can be a valid pre-computed
1530hash value, or 0 to ask for it to be computed.
1531
1532 SV* hv_delete_ent _((HV* tb, SV* key, I32 flags, U32 hash));
1533
cb1a09d0
AD
1534=item hv_exists
1535
1536Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 1537C<klen> is the length of the key.
cb1a09d0
AD
1538
1539 bool hv_exists _((HV* tb, char* key, U32 klen));
1540
1e422769
PP
1541=item hv_exists_ent
1542
1543Returns a boolean indicating whether the specified hash key exists. C<hash>
1544can be a valid pre-computed hash value, or 0 to ask for it to be computed.
1545
1546 bool hv_exists_ent _((HV* tb, SV* key, U32 hash));
1547
cb1a09d0
AD
1548=item hv_fetch
1549
1550Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 1551C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
1552part of a store. Check that the return value is non-null before
1553dereferencing it to a C<SV*>.
1554
1555 SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));
1556
1e422769
PP
1557=item hv_fetch_ent
1558
1559Returns the hash entry which corresponds to the specified key in the hash.
1560C<hash> must be a valid pre-computed hash number for the given C<key>, or
15610 if you want the function to compute it. IF C<lval> is set then the
1562fetch will be part of a store. Make sure the return value is non-null
1563before accessing it. The return value when C<tb> is a tied hash
1564is a pointer to a static location, so be sure to make a copy of the
1565structure if you need to store it somewhere.
1566
1567 HE* hv_fetch_ent _((HV* tb, SV* key, I32 lval, U32 hash));
1568
68dc0745
PP
1569=item hv_free_ent
1570
1571Releases a hash entry, such as while iterating though the hash. See
1572C<hv_iternext> and C<hv_delayfree_ent>.
1573
1574 void hv_free_ent _((HV* hv, HE* entry));
1575
cb1a09d0
AD
1576=item hv_iterinit
1577
1578Prepares a starting point to traverse a hash table.
1579
1580 I32 hv_iterinit _((HV* tb));
1581
1582=item hv_iterkey
1583
1584Returns the key from the current position of the hash iterator. See
1585C<hv_iterinit>.
1586
1587 char* hv_iterkey _((HE* entry, I32* retlen));
1588
1e422769 1589=item hv_iterkeysv
3fe9a6f1 1590
1e422769
PP
1591Returns the key as an C<SV*> from the current position of the hash
1592iterator. The return value will always be a mortal copy of the
1593key. Also see C<hv_iterinit>.
1594
1595 SV* hv_iterkeysv _((HE* entry));
1596
cb1a09d0
AD
1597=item hv_iternext
1598
1599Returns entries from a hash iterator. See C<hv_iterinit>.
1600
1601 HE* hv_iternext _((HV* tb));
1602
1603=item hv_iternextsv
1604
1605Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1606operation.
1607
1608 SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));
1609
1610=item hv_iterval
1611
1612Returns the value from the current position of the hash iterator. See
1613C<hv_iterkey>.
1614
1615 SV* hv_iterval _((HV* tb, HE* entry));
1616
1617=item hv_magic
1618
1619Adds magic to a hash. See C<sv_magic>.
1620
1621 void hv_magic _((HV* hv, GV* gv, int how));
1622
1623=item HvNAME
1624
1625Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1626
1627 char *HvNAME (HV* stash)
1628
1629=item hv_store
1630
1631Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
1632the length of the key. The C<hash> parameter is the pre-computed hash
1633value; if it is zero then Perl will compute it. The return value will be
1634null if the operation failed, otherwise it can be dereferenced to get the
1635original C<SV*>.
1636
1637 SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
1638
1e422769
PP
1639=item hv_store_ent
1640
1641Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
1642parameter is the pre-computed hash value; if it is zero then Perl will
1643compute it. The return value is the new hash entry so created. It will be
1644null if the operation failed or if the entry was stored in a tied hash.
1645Otherwise the contents of the return value can be accessed using the
1646C<He???> macros described here.
1647
1648 HE* hv_store_ent _((HV* tb, SV* key, SV* val, U32 hash));
1649
cb1a09d0
AD
1650=item hv_undef
1651
1652Undefines the hash.
1653
1654 void hv_undef _((HV* tb));
1655
1656=item isALNUM
1657
1658Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 1659character or digit.
cb1a09d0
AD
1660
1661 int isALNUM (char c)
1662
1663=item isALPHA
1664
5fb8527f 1665Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
1666character.
1667
1668 int isALPHA (char c)
1669
1670=item isDIGIT
1671
1672Returns a boolean indicating whether the C C<char> is an ascii digit.
1673
1674 int isDIGIT (char c)
1675
1676=item isLOWER
1677
1678Returns a boolean indicating whether the C C<char> is a lowercase character.
1679
1680 int isLOWER (char c)
1681
1682=item isSPACE
1683
1684Returns a boolean indicating whether the C C<char> is whitespace.
1685
1686 int isSPACE (char c)
1687
1688=item isUPPER
1689
1690Returns a boolean indicating whether the C C<char> is an uppercase character.
1691
1692 int isUPPER (char c)
1693
1694=item items
1695
1696Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
1697stack. See L<perlxs/"Variable-length Parameter Lists">.
1698
1699=item ix
1700
1701Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
1702was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
1703
1704=item LEAVE
1705
1706Closing bracket on a callback. See C<ENTER> and L<perlcall>.
1707
1708 LEAVE;
1709
1710=item MARK
1711
5fb8527f 1712Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
1713
1714=item mg_clear
1715
1716Clear something magical that the SV represents. See C<sv_magic>.
1717
1718 int mg_clear _((SV* sv));
1719
1720=item mg_copy
1721
1722Copies the magic from one SV to another. See C<sv_magic>.
1723
1724 int mg_copy _((SV *, SV *, char *, STRLEN));
1725
1726=item mg_find
1727
1728Finds the magic pointer for type matching the SV. See C<sv_magic>.
1729
1730 MAGIC* mg_find _((SV* sv, int type));
1731
1732=item mg_free
1733
1734Free any magic storage used by the SV. See C<sv_magic>.
1735
1736 int mg_free _((SV* sv));
1737
1738=item mg_get
1739
1740Do magic after a value is retrieved from the SV. See C<sv_magic>.
1741
1742 int mg_get _((SV* sv));
1743
1744=item mg_len
1745
1746Report on the SV's length. See C<sv_magic>.
1747
1748 U32 mg_len _((SV* sv));
1749
1750=item mg_magical
1751
1752Turns on the magical status of an SV. See C<sv_magic>.
1753
1754 void mg_magical _((SV* sv));
1755
1756=item mg_set
1757
1758Do magic after a value is assigned to the SV. See C<sv_magic>.
1759
1760 int mg_set _((SV* sv));
1761
1762=item Move
1763
1764The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
1765source, C<d> is the destination, C<n> is the number of items, and C<t> is
1766the type.
1767
1768 (void) Move( s, d, n, t );
1769
1770=item na
1771
1772A variable which may be used with C<SvPV> to tell Perl to calculate the
1773string length.
1774
1775=item New
1776
1777The XSUB-writer's interface to the C C<malloc> function.
1778
1779 void * New( x, void *ptr, int size, type )
1780
1781=item Newc
1782
1783The XSUB-writer's interface to the C C<malloc> function, with cast.
1784
1785 void * Newc( x, void *ptr, int size, type, cast )
1786
1787=item Newz
1788
1789The XSUB-writer's interface to the C C<malloc> function. The allocated
1790memory is zeroed with C<memzero>.
1791
1792 void * Newz( x, void *ptr, int size, type )
1793
1794=item newAV
1795
5f05dabc 1796Creates a new AV. The reference count is set to 1.
cb1a09d0
AD
1797
1798 AV* newAV _((void));
1799
1800=item newHV
1801
5f05dabc 1802Creates a new HV. The reference count is set to 1.
cb1a09d0
AD
1803
1804 HV* newHV _((void));
1805
5f05dabc 1806=item newRV_inc
cb1a09d0 1807
5f05dabc 1808Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
1809incremented.
1810
5f05dabc
PP
1811 SV* newRV_inc _((SV* ref));
1812
1813For historical reasons, "newRV" is a synonym for "newRV_inc".
1814
1815=item newRV_noinc
1816
1817Creates an RV wrapper for an SV. The reference count for the original
1818SV is B<not> incremented.
1819
07fa94a1 1820 SV* newRV_noinc _((SV* ref));
cb1a09d0
AD
1821
1822=item newSV
1823
1824Creates a new SV. The C<len> parameter indicates the number of bytes of
68dc0745 1825preallocated string space the SV should have. The reference count for the
07fa94a1 1826new SV is set to 1.
cb1a09d0
AD
1827
1828 SV* newSV _((STRLEN len));
1829
1830=item newSViv
1831
07fa94a1
JO
1832Creates a new SV and copies an integer into it. The reference count for the
1833SV is set to 1.
cb1a09d0
AD
1834
1835 SV* newSViv _((IV i));
1836
1837=item newSVnv
1838
07fa94a1
JO
1839Creates a new SV and copies a double into it. The reference count for the
1840SV is set to 1.
cb1a09d0
AD
1841
1842 SV* newSVnv _((NV i));
1843
1844=item newSVpv
1845
07fa94a1
JO
1846Creates a new SV and copies a string into it. The reference count for the
1847SV is set to 1. If C<len> is zero then Perl will compute the length.
cb1a09d0
AD
1848
1849 SV* newSVpv _((char* s, STRLEN len));
1850
1851=item newSVrv
1852
1853Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 1854it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 1855be blessed in the specified package. The new SV is returned and its
5f05dabc 1856reference count is 1.
8ebc5c01 1857
cb1a09d0
AD
1858 SV* newSVrv _((SV* rv, char* classname));
1859
1860=item newSVsv
1861
5fb8527f 1862Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0
AD
1863
1864 SV* newSVsv _((SV* old));
1865
1866=item newXS
1867
1868Used by C<xsubpp> to hook up XSUBs as Perl subs.
1869
1870=item newXSproto
1871
1872Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
1873the subs.
1874
1875=item Nullav
1876
1877Null AV pointer.
1878
1879=item Nullch
1880
1881Null character pointer.
1882
1883=item Nullcv
1884
1885Null CV pointer.
1886
1887=item Nullhv
1888
1889Null HV pointer.
1890
1891=item Nullsv
1892
1893Null SV pointer.
1894
1895=item ORIGMARK
1896
1897The original stack mark for the XSUB. See C<dORIGMARK>.
1898
1899=item perl_alloc
1900
1901Allocates a new Perl interpreter. See L<perlembed>.
1902
1903=item perl_call_argv
1904
1905Performs a callback to the specified Perl sub. See L<perlcall>.
1906
1907 I32 perl_call_argv _((char* subname, I32 flags, char** argv));
1908
1909=item perl_call_method
1910
1911Performs a callback to the specified Perl method. The blessed object must
1912be on the stack. See L<perlcall>.
1913
1914 I32 perl_call_method _((char* methname, I32 flags));
1915
1916=item perl_call_pv
1917
1918Performs a callback to the specified Perl sub. See L<perlcall>.
1919
1920 I32 perl_call_pv _((char* subname, I32 flags));
1921
1922=item perl_call_sv
1923
1924Performs a callback to the Perl sub whose name is in the SV. See
1925L<perlcall>.
1926
1927 I32 perl_call_sv _((SV* sv, I32 flags));
1928
1929=item perl_construct
1930
1931Initializes a new Perl interpreter. See L<perlembed>.
1932
1933=item perl_destruct
1934
1935Shuts down a Perl interpreter. See L<perlembed>.
1936
1937=item perl_eval_sv
1938
1939Tells Perl to C<eval> the string in the SV.
1940
1941 I32 perl_eval_sv _((SV* sv, I32 flags));
1942
1943=item perl_free
1944
1945Releases a Perl interpreter. See L<perlembed>.
1946
1947=item perl_get_av
1948
1949Returns the AV of the specified Perl array. If C<create> is set and the
1950Perl variable does not exist then it will be created. If C<create> is not
1951set and the variable does not exist then null is returned.
1952
1953 AV* perl_get_av _((char* name, I32 create));
1954
1955=item perl_get_cv
1956
1957Returns the CV of the specified Perl sub. If C<create> is set and the Perl
1958variable does not exist then it will be created. If C<create> is not
1959set and the variable does not exist then null is returned.
1960
1961 CV* perl_get_cv _((char* name, I32 create));
1962
1963=item perl_get_hv
1964
1965Returns the HV of the specified Perl hash. If C<create> is set and the Perl
1966variable does not exist then it will be created. If C<create> is not
1967set and the variable does not exist then null is returned.
1968
1969 HV* perl_get_hv _((char* name, I32 create));
1970
1971=item perl_get_sv
1972
1973Returns the SV of the specified Perl scalar. If C<create> is set and the
1974Perl variable does not exist then it will be created. If C<create> is not
1975set and the variable does not exist then null is returned.
1976
1977 SV* perl_get_sv _((char* name, I32 create));
1978
1979=item perl_parse
1980
1981Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
1982
1983=item perl_require_pv
1984
1985Tells Perl to C<require> a module.
1986
1987 void perl_require_pv _((char* pv));
1988
1989=item perl_run
1990
1991Tells a Perl interpreter to run. See L<perlembed>.
1992
1993=item POPi
1994
1995Pops an integer off the stack.
1996
1997 int POPi();
1998
1999=item POPl
2000
2001Pops a long off the stack.
2002
2003 long POPl();
2004
2005=item POPp
2006
2007Pops a string off the stack.
2008
2009 char * POPp();
2010
2011=item POPn
2012
2013Pops a double off the stack.
2014
2015 double POPn();
2016
2017=item POPs
2018
2019Pops an SV off the stack.
2020
2021 SV* POPs();
2022
2023=item PUSHMARK
2024
2025Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2026
2027 PUSHMARK(p)
2028
2029=item PUSHi
2030
2031Push an integer onto the stack. The stack must have room for this element.
2032See C<XPUSHi>.
2033
2034 PUSHi(int d)
2035
2036=item PUSHn
2037
2038Push a double onto the stack. The stack must have room for this element.
2039See C<XPUSHn>.
2040
2041 PUSHn(double d)
2042
2043=item PUSHp
2044
2045Push a string onto the stack. The stack must have room for this element.
2046The C<len> indicates the length of the string. See C<XPUSHp>.
2047
2048 PUSHp(char *c, int len )
2049
2050=item PUSHs
2051
2052Push an SV onto the stack. The stack must have room for this element. See
2053C<XPUSHs>.
2054
2055 PUSHs(sv)
2056
2057=item PUTBACK
2058
2059Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2060See C<PUSHMARK> and L<perlcall> for other uses.
2061
2062 PUTBACK;
2063
2064=item Renew
2065
2066The XSUB-writer's interface to the C C<realloc> function.
2067
2068 void * Renew( void *ptr, int size, type )
2069
2070=item Renewc
2071
2072The XSUB-writer's interface to the C C<realloc> function, with cast.
2073
2074 void * Renewc( void *ptr, int size, type, cast )
2075
2076=item RETVAL
2077
2078Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
2079This is always the proper type for the XSUB.
2080See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
2081
2082=item safefree
2083
2084The XSUB-writer's interface to the C C<free> function.
2085
2086=item safemalloc
2087
2088The XSUB-writer's interface to the C C<malloc> function.
2089
2090=item saferealloc
2091
2092The XSUB-writer's interface to the C C<realloc> function.
2093
2094=item savepv
2095
2096Copy a string to a safe spot. This does not use an SV.
2097
2098 char* savepv _((char* sv));
2099
2100=item savepvn
2101
2102Copy a string to a safe spot. The C<len> indicates number of bytes to
2103copy. This does not use an SV.
2104
2105 char* savepvn _((char* sv, I32 len));
2106
2107=item SAVETMPS
2108
2109Opening bracket for temporaries on a callback. See C<FREETMPS> and
2110L<perlcall>.
2111
2112 SAVETMPS;
2113
2114=item SP
2115
2116Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2117C<SPAGAIN>.
2118
2119=item SPAGAIN
2120
5f05dabc 2121Re-fetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
2122
2123 SPAGAIN;
2124
2125=item ST
2126
2127Used to access elements on the XSUB's stack.
2128
2129 SV* ST(int x)
2130
2131=item strEQ
2132
2133Test two strings to see if they are equal. Returns true or false.
2134
2135 int strEQ( char *s1, char *s2 )
2136
2137=item strGE
2138
2139Test two strings to see if the first, C<s1>, is greater than or equal to the
2140second, C<s2>. Returns true or false.
2141
2142 int strGE( char *s1, char *s2 )
2143
2144=item strGT
2145
2146Test two strings to see if the first, C<s1>, is greater than the second,
2147C<s2>. Returns true or false.
2148
2149 int strGT( char *s1, char *s2 )
2150
2151=item strLE
2152
2153Test two strings to see if the first, C<s1>, is less than or equal to the
2154second, C<s2>. Returns true or false.
2155
2156 int strLE( char *s1, char *s2 )
2157
2158=item strLT
2159
2160Test two strings to see if the first, C<s1>, is less than the second,
2161C<s2>. Returns true or false.
2162
2163 int strLT( char *s1, char *s2 )
2164
2165=item strNE
2166
2167Test two strings to see if they are different. Returns true or false.
2168
2169 int strNE( char *s1, char *s2 )
2170
2171=item strnEQ
2172
2173Test two strings to see if they are equal. The C<len> parameter indicates
2174the number of bytes to compare. Returns true or false.
2175
2176 int strnEQ( char *s1, char *s2 )
2177
2178=item strnNE
2179
2180Test two strings to see if they are different. The C<len> parameter
2181indicates the number of bytes to compare. Returns true or false.
2182
2183 int strnNE( char *s1, char *s2, int len )
2184
2185=item sv_2mortal
2186
2187Marks an SV as mortal. The SV will be destroyed when the current context
2188ends.
2189
2190 SV* sv_2mortal _((SV* sv));
2191
2192=item sv_bless
2193
2194Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
2195must be designated by its stash (see C<gv_stashpv()>). The reference count
2196of the SV is unaffected.
cb1a09d0
AD
2197
2198 SV* sv_bless _((SV* sv, HV* stash));
2199
2200=item sv_catpv
2201
2202Concatenates the string onto the end of the string which is in the SV.
2203
2204 void sv_catpv _((SV* sv, char* ptr));
2205
2206=item sv_catpvn
2207
2208Concatenates the string onto the end of the string which is in the SV. The
2209C<len> indicates number of bytes to copy.
2210
2211 void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
2212
2213=item sv_catsv
2214
5fb8527f 2215Concatenates the string from SV C<ssv> onto the end of the string in SV
cb1a09d0
AD
2216C<dsv>.
2217
2218 void sv_catsv _((SV* dsv, SV* ssv));
2219
5fb8527f
PP
2220=item sv_cmp
2221
2222Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2223string in C<sv1> is less than, equal to, or greater than the string in
2224C<sv2>.
2225
2226 I32 sv_cmp _((SV* sv1, SV* sv2));
2227
2228=item sv_cmp
2229
2230Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2231string in C<sv1> is less than, equal to, or greater than the string in
2232C<sv2>.
2233
2234 I32 sv_cmp _((SV* sv1, SV* sv2));
2235
cb1a09d0
AD
2236=item SvCUR
2237
2238Returns the length of the string which is in the SV. See C<SvLEN>.
2239
2240 int SvCUR (SV* sv)
2241
2242=item SvCUR_set
2243
2244Set the length of the string which is in the SV. See C<SvCUR>.
2245
2246 SvCUR_set (SV* sv, int val )
2247
5fb8527f
PP
2248=item sv_dec
2249
5f05dabc 2250Auto-decrement of the value in the SV.
5fb8527f
PP
2251
2252 void sv_dec _((SV* sv));
2253
2254=item sv_dec
2255
5f05dabc 2256Auto-decrement of the value in the SV.
5fb8527f
PP
2257
2258 void sv_dec _((SV* sv));
2259
cb1a09d0
AD
2260=item SvEND
2261
2262Returns a pointer to the last character in the string which is in the SV.
2263See C<SvCUR>. Access the character as
2264
2265 *SvEND(sv)
2266
5fb8527f
PP
2267=item sv_eq
2268
2269Returns a boolean indicating whether the strings in the two SVs are
2270identical.
2271
2272 I32 sv_eq _((SV* sv1, SV* sv2));
2273
cb1a09d0
AD
2274=item SvGROW
2275
5fb8527f
PP
2276Expands the character buffer in the SV. Calls C<sv_grow> to perform the
2277expansion if necessary. Returns a pointer to the character buffer.
cb1a09d0
AD
2278
2279 char * SvGROW( SV* sv, int len )
2280
5fb8527f
PP
2281=item sv_grow
2282
2283Expands the character buffer in the SV. This will use C<sv_unref> and will
2284upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2285Use C<SvGROW>.
2286
2287=item sv_inc
2288
07fa94a1 2289Auto-increment of the value in the SV.
5fb8527f
PP
2290
2291 void sv_inc _((SV* sv));
2292
cb1a09d0
AD
2293=item SvIOK
2294
2295Returns a boolean indicating whether the SV contains an integer.
2296
2297 int SvIOK (SV* SV)
2298
2299=item SvIOK_off
2300
2301Unsets the IV status of an SV.
2302
2303 SvIOK_off (SV* sv)
2304
2305=item SvIOK_on
2306
2307Tells an SV that it is an integer.
2308
2309 SvIOK_on (SV* sv)
2310
5fb8527f
PP
2311=item SvIOK_only
2312
2313Tells an SV that it is an integer and disables all other OK bits.
2314
2315 SvIOK_on (SV* sv)
2316
2317=item SvIOK_only
2318
2319Tells an SV that it is an integer and disables all other OK bits.
2320
2321 SvIOK_on (SV* sv)
2322
cb1a09d0
AD
2323=item SvIOKp
2324
2325Returns a boolean indicating whether the SV contains an integer. Checks the
2326B<private> setting. Use C<SvIOK>.
2327
2328 int SvIOKp (SV* SV)
2329
2330=item sv_isa
2331
2332Returns a boolean indicating whether the SV is blessed into the specified
2333class. This does not know how to check for subtype, so it doesn't work in
2334an inheritance relationship.
2335
2336 int sv_isa _((SV* sv, char* name));
2337
2338=item SvIV
2339
2340Returns the integer which is in the SV.
2341
2342 int SvIV (SV* sv)
2343
2344=item sv_isobject
2345
2346Returns a boolean indicating whether the SV is an RV pointing to a blessed
2347object. If the SV is not an RV, or if the object is not blessed, then this
2348will return false.
2349
2350 int sv_isobject _((SV* sv));
2351
2352=item SvIVX
2353
2354Returns the integer which is stored in the SV.
2355
2356 int SvIVX (SV* sv);
2357
2358=item SvLEN
2359
2360Returns the size of the string buffer in the SV. See C<SvCUR>.
2361
2362 int SvLEN (SV* sv)
2363
5fb8527f
PP
2364=item sv_len
2365
2366Returns the length of the string in the SV. Use C<SvCUR>.
2367
2368 STRLEN sv_len _((SV* sv));
2369
2370=item sv_len
2371
2372Returns the length of the string in the SV. Use C<SvCUR>.
2373
2374 STRLEN sv_len _((SV* sv));
2375
cb1a09d0
AD
2376=item sv_magic
2377
2378Adds magic to an SV.
2379
2380 void sv_magic _((SV* sv, SV* obj, int how, char* name, I32 namlen));
2381
2382=item sv_mortalcopy
2383
2384Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 2385as mortal.
cb1a09d0
AD
2386
2387 SV* sv_mortalcopy _((SV* oldsv));
2388
2389=item SvOK
2390
2391Returns a boolean indicating whether the value is an SV.
2392
2393 int SvOK (SV* sv)
2394
2395=item sv_newmortal
2396
5f05dabc 2397Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0
AD
2398
2399 SV* sv_newmortal _((void));
2400
2401=item sv_no
2402
2403This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
2404
2405=item SvNIOK
2406
2407Returns a boolean indicating whether the SV contains a number, integer or
2408double.
2409
2410 int SvNIOK (SV* SV)
2411
2412=item SvNIOK_off
2413
2414Unsets the NV/IV status of an SV.
2415
2416 SvNIOK_off (SV* sv)
2417
2418=item SvNIOKp
2419
2420Returns a boolean indicating whether the SV contains a number, integer or
2421double. Checks the B<private> setting. Use C<SvNIOK>.
2422
2423 int SvNIOKp (SV* SV)
2424
2425=item SvNOK
2426
2427Returns a boolean indicating whether the SV contains a double.
2428
2429 int SvNOK (SV* SV)
2430
2431=item SvNOK_off
2432
2433Unsets the NV status of an SV.
2434
2435 SvNOK_off (SV* sv)
2436
2437=item SvNOK_on
2438
2439Tells an SV that it is a double.
2440
2441 SvNOK_on (SV* sv)
2442
5fb8527f
PP
2443=item SvNOK_only
2444
2445Tells an SV that it is a double and disables all other OK bits.
2446
2447 SvNOK_on (SV* sv)
2448
2449=item SvNOK_only
2450
2451Tells an SV that it is a double and disables all other OK bits.
2452
2453 SvNOK_on (SV* sv)
2454
cb1a09d0
AD
2455=item SvNOKp
2456
2457Returns a boolean indicating whether the SV contains a double. Checks the
2458B<private> setting. Use C<SvNOK>.
2459
2460 int SvNOKp (SV* SV)
2461
2462=item SvNV
2463
2464Returns the double which is stored in the SV.
2465
2466 double SvNV (SV* sv);
2467
2468=item SvNVX
2469
2470Returns the double which is stored in the SV.
2471
2472 double SvNVX (SV* sv);
2473
2474=item SvPOK
2475
2476Returns a boolean indicating whether the SV contains a character string.
2477
2478 int SvPOK (SV* SV)
2479
2480=item SvPOK_off
2481
2482Unsets the PV status of an SV.
2483
2484 SvPOK_off (SV* sv)
2485
2486=item SvPOK_on
2487
2488Tells an SV that it is a string.
2489
2490 SvPOK_on (SV* sv)
2491
5fb8527f
PP
2492=item SvPOK_only
2493
2494Tells an SV that it is a string and disables all other OK bits.
2495
2496 SvPOK_on (SV* sv)
2497
2498=item SvPOK_only
2499
2500Tells an SV that it is a string and disables all other OK bits.
2501
2502 SvPOK_on (SV* sv)
2503
cb1a09d0
AD
2504=item SvPOKp
2505
2506Returns a boolean indicating whether the SV contains a character string.
2507Checks the B<private> setting. Use C<SvPOK>.
2508
2509 int SvPOKp (SV* SV)
2510
2511=item SvPV
2512
2513Returns a pointer to the string in the SV, or a stringified form of the SV
2514if the SV does not contain a string. If C<len> is C<na> then Perl will
2515handle the length on its own.
2516
2517 char * SvPV (SV* sv, int len )
2518
2519=item SvPVX
2520
2521Returns a pointer to the string in the SV. The SV must contain a string.
2522
2523 char * SvPVX (SV* sv)
2524
2525=item SvREFCNT
2526
5f05dabc 2527Returns the value of the object's reference count.
cb1a09d0
AD
2528
2529 int SvREFCNT (SV* sv);
2530
2531=item SvREFCNT_dec
2532
5f05dabc 2533Decrements the reference count of the given SV.
cb1a09d0
AD
2534
2535 void SvREFCNT_dec (SV* sv)
2536
2537=item SvREFCNT_inc
2538
5f05dabc 2539Increments the reference count of the given SV.
cb1a09d0
AD
2540
2541 void SvREFCNT_inc (SV* sv)
2542
2543=item SvROK
2544
2545Tests if the SV is an RV.
2546
2547 int SvROK (SV* sv)
2548
2549=item SvROK_off
2550
2551Unsets the RV status of an SV.
2552
2553 SvROK_off (SV* sv)
2554
2555=item SvROK_on
2556
2557Tells an SV that it is an RV.
2558
2559 SvROK_on (SV* sv)
2560
2561=item SvRV
2562
2563Dereferences an RV to return the SV.
2564
2565 SV* SvRV (SV* sv);
2566
2567=item sv_setiv
2568
2569Copies an integer into the given SV.
2570
2571 void sv_setiv _((SV* sv, IV num));
2572
2573=item sv_setnv
2574
2575Copies a double into the given SV.
2576
2577 void sv_setnv _((SV* sv, double num));
2578
2579=item sv_setpv
2580
2581Copies a string into an SV. The string must be null-terminated.
2582
2583 void sv_setpv _((SV* sv, char* ptr));
2584
2585=item sv_setpvn
2586
2587Copies a string into an SV. The C<len> parameter indicates the number of
2588bytes to be copied.
2589
2590 void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
2591
2592=item sv_setref_iv
2593
5fb8527f
PP
2594Copies an integer into a new SV, optionally blessing the SV. The C<rv>
2595argument will be upgraded to an RV. That RV will be modified to point to
2596the new SV. The C<classname> argument indicates the package for the
2597blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2598will be returned and will have a reference count of 1.
cb1a09d0
AD
2599
2600 SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
2601
2602=item sv_setref_nv
2603
5fb8527f
PP
2604Copies a double into a new SV, optionally blessing the SV. The C<rv>
2605argument will be upgraded to an RV. That RV will be modified to point to
2606the new SV. The C<classname> argument indicates the package for the
2607blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2608will be returned and will have a reference count of 1.
cb1a09d0
AD
2609
2610 SV* sv_setref_nv _((SV *rv, char *classname, double nv));
2611
2612=item sv_setref_pv
2613
5fb8527f
PP
2614Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
2615argument will be upgraded to an RV. That RV will be modified to point to
2616the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
2617into the SV. The C<classname> argument indicates the package for the
2618blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2619will be returned and will have a reference count of 1.
cb1a09d0
AD
2620
2621 SV* sv_setref_pv _((SV *rv, char *classname, void* pv));
2622
2623Do not use with integral Perl types such as HV, AV, SV, CV, because those
2624objects will become corrupted by the pointer copy process.
2625
2626Note that C<sv_setref_pvn> copies the string while this copies the pointer.
2627
2628=item sv_setref_pvn
2629
5fb8527f
PP
2630Copies a string into a new SV, optionally blessing the SV. The length of the
2631string must be specified with C<n>. The C<rv> argument will be upgraded to
2632an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
2633argument indicates the package for the blessing. Set C<classname> to
2634C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 2635a reference count of 1.
cb1a09d0
AD
2636
2637 SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
2638
2639Note that C<sv_setref_pv> copies the pointer while this copies the string.
2640
2641=item sv_setsv
2642
2643Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
5f05dabc 2644The source SV may be destroyed if it is mortal.
cb1a09d0
AD
2645
2646 void sv_setsv _((SV* dsv, SV* ssv));
2647
2648=item SvSTASH
2649
2650Returns the stash of the SV.
2651
2652 HV * SvSTASH (SV* sv)
2653
2654=item SVt_IV
2655
2656Integer type flag for scalars. See C<svtype>.
2657
2658=item SVt_PV
2659
2660Pointer type flag for scalars. See C<svtype>.
2661
2662=item SVt_PVAV
2663
2664Type flag for arrays. See C<svtype>.
2665
2666=item SVt_PVCV
2667
2668Type flag for code refs. See C<svtype>.
2669
2670=item SVt_PVHV
2671
2672Type flag for hashes. See C<svtype>.
2673
2674=item SVt_PVMG
2675
2676Type flag for blessed scalars. See C<svtype>.
2677
2678=item SVt_NV
2679
2680Double type flag for scalars. See C<svtype>.
2681
2682=item SvTRUE
2683
2684Returns a boolean indicating whether Perl would evaluate the SV as true or
2685false, defined or undefined.
2686
2687 int SvTRUE (SV* sv)
2688
2689=item SvTYPE
2690
2691Returns the type of the SV. See C<svtype>.
2692
2693 svtype SvTYPE (SV* sv)
2694
2695=item svtype
2696
2697An enum of flags for Perl types. These are found in the file B<sv.h> in the
2698C<svtype> enum. Test these flags with the C<SvTYPE> macro.
2699
2700=item SvUPGRADE
2701
5fb8527f
PP
2702Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
2703the upgrade if necessary. See C<svtype>.
2704
2705 bool SvUPGRADE _((SV* sv, svtype mt));
2706
2707=item sv_upgrade
2708
2709Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
cb1a09d0
AD
2710
2711=item sv_undef
2712
2713This is the C<undef> SV. Always refer to this as C<&sv_undef>.
2714
5fb8527f
PP
2715=item sv_unref
2716
07fa94a1
JO
2717Unsets the RV status of the SV, and decrements the reference count of
2718whatever was being referenced by the RV. This can almost be thought of
2719as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f
PP
2720
2721 void sv_unref _((SV* sv));
2722
cb1a09d0
AD
2723=item sv_usepvn
2724
2725Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
2726stored inside the SV but sv_usepvn allows the SV to use an outside string.
2727The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
2728string length, C<len>, must be supplied. This function will realloc the
2729memory pointed to by C<ptr>, so that pointer should not be freed or used by
2730the programmer after giving it to sv_usepvn.
2731
2732 void sv_usepvn _((SV* sv, char* ptr, STRLEN len));
2733
2734=item sv_yes
2735
2736This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
2737
2738=item THIS
2739
2740Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
2741This is always the proper type for the C++ object. See C<CLASS> and
5fb8527f 2742L<perlxs/"Using XS With C++">.
cb1a09d0
AD
2743
2744=item toLOWER
2745
2746Converts the specified character to lowercase.
2747
2748 int toLOWER (char c)
2749
2750=item toUPPER
2751
2752Converts the specified character to uppercase.
2753
2754 int toUPPER (char c)
2755
2756=item warn
2757
2758This is the XSUB-writer's interface to Perl's C<warn> function. Use this
2759function the same way you use the C C<printf> function. See C<croak()>.
2760
2761=item XPUSHi
2762
2763Push an integer onto the stack, extending the stack if necessary. See
2764C<PUSHi>.
2765
2766 XPUSHi(int d)
2767
2768=item XPUSHn
2769
2770Push a double onto the stack, extending the stack if necessary. See
2771C<PUSHn>.
2772
2773 XPUSHn(double d)
2774
2775=item XPUSHp
2776
2777Push a string onto the stack, extending the stack if necessary. The C<len>
2778indicates the length of the string. See C<PUSHp>.
2779
2780 XPUSHp(char *c, int len)
2781
2782=item XPUSHs
2783
2784Push an SV onto the stack, extending the stack if necessary. See C<PUSHs>.
2785
2786 XPUSHs(sv)
2787
5fb8527f
PP
2788=item XS
2789
2790Macro to declare an XSUB and its C parameter list. This is handled by
2791C<xsubpp>.
2792
cb1a09d0
AD
2793=item XSRETURN
2794
2795Return from XSUB, indicating number of items on the stack. This is usually
2796handled by C<xsubpp>.
2797
5fb8527f 2798 XSRETURN(int x);
cb1a09d0
AD
2799
2800=item XSRETURN_EMPTY
2801
5fb8527f 2802Return an empty list from an XSUB immediately.
cb1a09d0
AD
2803
2804 XSRETURN_EMPTY;
2805
5fb8527f
PP
2806=item XSRETURN_IV
2807
2808Return an integer from an XSUB immediately. Uses C<XST_mIV>.
2809
2810 XSRETURN_IV(IV v);
2811
cb1a09d0
AD
2812=item XSRETURN_NO
2813
5fb8527f 2814Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
cb1a09d0
AD
2815
2816 XSRETURN_NO;
2817
5fb8527f
PP
2818=item XSRETURN_NV
2819
2820Return an double from an XSUB immediately. Uses C<XST_mNV>.
2821
2822 XSRETURN_NV(NV v);
2823
2824=item XSRETURN_PV
2825
2826Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
2827
2828 XSRETURN_PV(char *v);
2829
cb1a09d0
AD
2830=item XSRETURN_UNDEF
2831
5fb8527f 2832Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
cb1a09d0
AD
2833
2834 XSRETURN_UNDEF;
2835
2836=item XSRETURN_YES
2837
5fb8527f 2838Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
cb1a09d0
AD
2839
2840 XSRETURN_YES;
2841
5fb8527f
PP
2842=item XST_mIV
2843
2844Place an integer into the specified position C<i> on the stack. The value is
2845stored in a new mortal SV.
2846
2847 XST_mIV( int i, IV v );
2848
2849=item XST_mNV
2850
2851Place a double into the specified position C<i> on the stack. The value is
2852stored in a new mortal SV.
2853
2854 XST_mNV( int i, NV v );
2855
2856=item XST_mNO
2857
2858Place C<&sv_no> into the specified position C<i> on the stack.
2859
2860 XST_mNO( int i );
2861
2862=item XST_mPV
2863
2864Place a copy of a string into the specified position C<i> on the stack. The
2865value is stored in a new mortal SV.
2866
2867 XST_mPV( int i, char *v );
2868
2869=item XST_mUNDEF
2870
2871Place C<&sv_undef> into the specified position C<i> on the stack.
2872
2873 XST_mUNDEF( int i );
2874
2875=item XST_mYES
2876
2877Place C<&sv_yes> into the specified position C<i> on the stack.
2878
2879 XST_mYES( int i );
2880
2881=item XS_VERSION
2882
2883The version identifier for an XS module. This is usually handled
2884automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
2885
2886=item XS_VERSION_BOOTCHECK
2887
2888Macro to verify that a PM module's $VERSION variable matches the XS module's
2889C<XS_VERSION> variable. This is usually handled automatically by
2890C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
2891
cb1a09d0
AD
2892=item Zero
2893
2894The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
2895destination, C<n> is the number of items, and C<t> is the type.
2896
2897 (void) Zero( d, n, t );
2898
2899=back
2900
5f05dabc 2901=head1 EDITOR
cb1a09d0 2902
9607fc9c 2903Jeff Okamoto <F<okamoto@corp.hp.com>>
cb1a09d0
AD
2904
2905With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
2906Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
55497cff 2907Bowers, Matthew Green, Tim Bunce, Spider Boardman, and Ulrich Pfeifer.
cb1a09d0 2908
9607fc9c 2909API Listing by Dean Roehrich <F<roehrich@cray.com>>.
cb1a09d0
AD
2910
2911=head1 DATE
2912
68dc0745 2913Version 31.3: 1997/3/14