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perlguts caveats
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1=head1 NAME
2
3perlguts - Perl's Internal Functions
4
5=head1 DESCRIPTION
6
7This document attempts to describe some of the internal functions of the
8Perl executable. It is far from complete and probably contains many errors.
9Please refer any questions or comments to the author below.
10
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11=head1 Variables
12
5f05dabc 13=head2 Datatypes
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14
15Perl has three typedefs that handle Perl's three main data types:
16
17 SV Scalar Value
18 AV Array Value
19 HV Hash Value
20
d1b91892 21Each typedef has specific routines that manipulate the various data types.
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22
23=head2 What is an "IV"?
24
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25Perl uses a special typedef IV which is a simple integer type that is
26guaranteed to be large enough to hold a pointer (as well as an integer).
a0d0e21e 27
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28Perl also uses two special typedefs, I32 and I16, which will always be at
29least 32-bits and 16-bits long, respectively.
a0d0e21e 30
54310121 31=head2 Working with SVs
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32
33An SV can be created and loaded with one command. There are four types of
34values that can be loaded: an integer value (IV), a double (NV), a string,
35(PV), and another scalar (SV).
36
46fc3d4c 37The five routines are:
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38
39 SV* newSViv(IV);
40 SV* newSVnv(double);
41 SV* newSVpv(char*, int);
46fc3d4c 42 SV* newSVpvf(const char*, ...);
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43 SV* newSVsv(SV*);
44
46fc3d4c 45To change the value of an *already-existing* SV, there are six routines:
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46
47 void sv_setiv(SV*, IV);
48 void sv_setnv(SV*, double);
a0d0e21e 49 void sv_setpv(SV*, char*);
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50 void sv_setpvn(SV*, char*, int)
51 void sv_setpvf(SV*, const char*, ...);
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52 void sv_setsv(SV*, SV*);
53
54Notice that you can choose to specify the length of the string to be
d1b91892 55assigned by using C<sv_setpvn> or C<newSVpv>, or you may allow Perl to
cb1a09d0 56calculate the length by using C<sv_setpv> or by specifying 0 as the second
d1b91892 57argument to C<newSVpv>. Be warned, though, that Perl will determine the
a0d0e21e 58string's length by using C<strlen>, which depends on the string terminating
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59with a NUL character. The arguments of C<sv_setpvf> are processed like
60C<sprintf>, and the formatted output becomes the value.
a0d0e21e 61
54310121 62All SVs that will contain strings should, but need not, be terminated
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63with a NUL character. If it is not NUL-terminated there is a risk of
64core dumps and corruptions from code which passes the string to C
65functions or system calls which expect a NUL-terminated string.
66Perl's own functions typically add a trailing NUL for this reason.
67Nevertheless, you should be very careful when you pass a string stored
68in an SV to a C function or system call.
69
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70To access the actual value that an SV points to, you can use the macros:
71
72 SvIV(SV*)
73 SvNV(SV*)
74 SvPV(SV*, STRLEN len)
75
76which will automatically coerce the actual scalar type into an IV, double,
77or string.
78
79In the C<SvPV> macro, the length of the string returned is placed into the
80variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
81care what the length of the data is, use the global variable C<na>. Remember,
82however, that Perl allows arbitrary strings of data that may both contain
54310121 83NULs and might not be terminated by a NUL.
a0d0e21e 84
07fa94a1 85If you want to know if the scalar value is TRUE, you can use:
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86
87 SvTRUE(SV*)
88
89Although Perl will automatically grow strings for you, if you need to force
90Perl to allocate more memory for your SV, you can use the macro
91
92 SvGROW(SV*, STRLEN newlen)
93
94which will determine if more memory needs to be allocated. If so, it will
95call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
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96decrease, the allocated memory of an SV and that it does not automatically
97add a byte for the a trailing NUL (perl's own string functions typically do
8ebc5c01 98C<SvGROW(sv, len + 1)>).
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99
100If you have an SV and want to know what kind of data Perl thinks is stored
101in it, you can use the following macros to check the type of SV you have.
102
103 SvIOK(SV*)
104 SvNOK(SV*)
105 SvPOK(SV*)
106
107You can get and set the current length of the string stored in an SV with
108the following macros:
109
110 SvCUR(SV*)
111 SvCUR_set(SV*, I32 val)
112
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113You can also get a pointer to the end of the string stored in the SV
114with the macro:
115
116 SvEND(SV*)
117
118But note that these last three macros are valid only if C<SvPOK()> is true.
a0d0e21e 119
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120If you want to append something to the end of string stored in an C<SV*>,
121you can use the following functions:
122
123 void sv_catpv(SV*, char*);
124 void sv_catpvn(SV*, char*, int);
46fc3d4c 125 void sv_catpvf(SV*, const char*, ...);
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126 void sv_catsv(SV*, SV*);
127
128The first function calculates the length of the string to be appended by
129using C<strlen>. In the second, you specify the length of the string
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130yourself. The third function processes its arguments like C<sprintf> and
131appends the formatted output. The fourth function extends the string
132stored in the first SV with the string stored in the second SV. It also
133forces the second SV to be interpreted as a string.
d1b91892 134
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135If you know the name of a scalar variable, you can get a pointer to its SV
136by using the following:
137
5f05dabc 138 SV* perl_get_sv("package::varname", FALSE);
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139
140This returns NULL if the variable does not exist.
141
d1b91892 142If you want to know if this variable (or any other SV) is actually C<defined>,
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143you can call:
144
145 SvOK(SV*)
146
147The scalar C<undef> value is stored in an SV instance called C<sv_undef>. Its
148address can be used whenever an C<SV*> is needed.
149
150There are also the two values C<sv_yes> and C<sv_no>, which contain Boolean
151TRUE and FALSE values, respectively. Like C<sv_undef>, their addresses can
152be used whenever an C<SV*> is needed.
153
154Do not be fooled into thinking that C<(SV *) 0> is the same as C<&sv_undef>.
155Take this code:
156
157 SV* sv = (SV*) 0;
158 if (I-am-to-return-a-real-value) {
159 sv = sv_2mortal(newSViv(42));
160 }
161 sv_setsv(ST(0), sv);
162
163This code tries to return a new SV (which contains the value 42) if it should
04343c6d 164return a real value, or undef otherwise. Instead it has returned a NULL
a0d0e21e 165pointer which, somewhere down the line, will cause a segmentation violation,
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166bus error, or just weird results. Change the zero to C<&sv_undef> in the first
167line and all will be well.
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168
169To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
3fe9a6f1 170call is not necessary (see L<Reference Counts and Mortality>).
a0d0e21e 171
d1b91892 172=head2 What's Really Stored in an SV?
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173
174Recall that the usual method of determining the type of scalar you have is
5f05dabc 175to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
d1b91892 176usually these macros will always return TRUE and calling the C<Sv*V>
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177macros will do the appropriate conversion of string to integer/double or
178integer/double to string.
179
180If you I<really> need to know if you have an integer, double, or string
181pointer in an SV, you can use the following three macros instead:
182
183 SvIOKp(SV*)
184 SvNOKp(SV*)
185 SvPOKp(SV*)
186
187These will tell you if you truly have an integer, double, or string pointer
d1b91892 188stored in your SV. The "p" stands for private.
a0d0e21e 189
07fa94a1 190In general, though, it's best to use the C<Sv*V> macros.
a0d0e21e 191
54310121 192=head2 Working with AVs
a0d0e21e 193
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194There are two ways to create and load an AV. The first method creates an
195empty AV:
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196
197 AV* newAV();
198
54310121 199The second method both creates the AV and initially populates it with SVs:
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200
201 AV* av_make(I32 num, SV **ptr);
202
5f05dabc 203The second argument points to an array containing C<num> C<SV*>'s. Once the
54310121 204AV has been created, the SVs can be destroyed, if so desired.
a0d0e21e 205
54310121 206Once the AV has been created, the following operations are possible on AVs:
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207
208 void av_push(AV*, SV*);
209 SV* av_pop(AV*);
210 SV* av_shift(AV*);
211 void av_unshift(AV*, I32 num);
212
213These should be familiar operations, with the exception of C<av_unshift>.
214This routine adds C<num> elements at the front of the array with the C<undef>
215value. You must then use C<av_store> (described below) to assign values
216to these new elements.
217
218Here are some other functions:
219
5f05dabc 220 I32 av_len(AV*);
a0d0e21e 221 SV** av_fetch(AV*, I32 key, I32 lval);
a0d0e21e 222 SV** av_store(AV*, I32 key, SV* val);
a0d0e21e 223
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224The C<av_len> function returns the highest index value in array (just
225like $#array in Perl). If the array is empty, -1 is returned. The
226C<av_fetch> function returns the value at index C<key>, but if C<lval>
227is non-zero, then C<av_fetch> will store an undef value at that index.
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228The C<av_store> function stores the value C<val> at index C<key>, and does
229not increment the reference count of C<val>. Thus the caller is responsible
230for taking care of that, and if C<av_store> returns NULL, the caller will
231have to decrement the reference count to avoid a memory leak. Note that
232C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s as their
233return value.
d1b91892 234
a0d0e21e 235 void av_clear(AV*);
a0d0e21e 236 void av_undef(AV*);
cb1a09d0 237 void av_extend(AV*, I32 key);
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238
239The C<av_clear> function deletes all the elements in the AV* array, but
240does not actually delete the array itself. The C<av_undef> function will
241delete all the elements in the array plus the array itself. The
242C<av_extend> function extends the array so that it contains C<key>
243elements. If C<key> is less than the current length of the array, then
244nothing is done.
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245
246If you know the name of an array variable, you can get a pointer to its AV
247by using the following:
248
5f05dabc 249 AV* perl_get_av("package::varname", FALSE);
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250
251This returns NULL if the variable does not exist.
252
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253See L<Understanding the Magic of Tied Hashes and Arrays> for more
254information on how to use the array access functions on tied arrays.
255
54310121 256=head2 Working with HVs
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257
258To create an HV, you use the following routine:
259
260 HV* newHV();
261
54310121 262Once the HV has been created, the following operations are possible on HVs:
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263
264 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
265 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
266
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267The C<klen> parameter is the length of the key being passed in (Note that
268you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
269length of the key). The C<val> argument contains the SV pointer to the
54310121 270scalar being stored, and C<hash> is the precomputed hash value (zero if
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271you want C<hv_store> to calculate it for you). The C<lval> parameter
272indicates whether this fetch is actually a part of a store operation, in
273which case a new undefined value will be added to the HV with the supplied
274key and C<hv_fetch> will return as if the value had already existed.
a0d0e21e 275
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276Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
277C<SV*>. To access the scalar value, you must first dereference the return
278value. However, you should check to make sure that the return value is
279not NULL before dereferencing it.
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280
281These two functions check if a hash table entry exists, and deletes it.
282
283 bool hv_exists(HV*, char* key, U32 klen);
d1b91892 284 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
a0d0e21e 285
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286If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
287create and return a mortal copy of the deleted value.
288
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289And more miscellaneous functions:
290
291 void hv_clear(HV*);
a0d0e21e 292 void hv_undef(HV*);
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293
294Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
295table but does not actually delete the hash table. The C<hv_undef> deletes
296both the entries and the hash table itself.
a0d0e21e 297
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298Perl keeps the actual data in linked list of structures with a typedef of HE.
299These contain the actual key and value pointers (plus extra administrative
300overhead). The key is a string pointer; the value is an C<SV*>. However,
301once you have an C<HE*>, to get the actual key and value, use the routines
302specified below.
303
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304 I32 hv_iterinit(HV*);
305 /* Prepares starting point to traverse hash table */
306 HE* hv_iternext(HV*);
307 /* Get the next entry, and return a pointer to a
308 structure that has both the key and value */
309 char* hv_iterkey(HE* entry, I32* retlen);
310 /* Get the key from an HE structure and also return
311 the length of the key string */
cb1a09d0 312 SV* hv_iterval(HV*, HE* entry);
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313 /* Return a SV pointer to the value of the HE
314 structure */
cb1a09d0 315 SV* hv_iternextsv(HV*, char** key, I32* retlen);
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316 /* This convenience routine combines hv_iternext,
317 hv_iterkey, and hv_iterval. The key and retlen
318 arguments are return values for the key and its
319 length. The value is returned in the SV* argument */
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320
321If you know the name of a hash variable, you can get a pointer to its HV
322by using the following:
323
5f05dabc 324 HV* perl_get_hv("package::varname", FALSE);
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325
326This returns NULL if the variable does not exist.
327
8ebc5c01 328The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
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329
330 i = klen;
331 hash = 0;
332 s = key;
333 while (i--)
334 hash = hash * 33 + *s++;
335
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336See L<Understanding the Magic of Tied Hashes and Arrays> for more
337information on how to use the hash access functions on tied hashes.
338
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339=head2 Hash API Extensions
340
341Beginning with version 5.004, the following functions are also supported:
342
343 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
344 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
345
346 bool hv_exists_ent (HV* tb, SV* key, U32 hash);
347 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
348
349 SV* hv_iterkeysv (HE* entry);
350
351Note that these functions take C<SV*> keys, which simplifies writing
352of extension code that deals with hash structures. These functions
353also allow passing of C<SV*> keys to C<tie> functions without forcing
354you to stringify the keys (unlike the previous set of functions).
355
356They also return and accept whole hash entries (C<HE*>), making their
357use more efficient (since the hash number for a particular string
358doesn't have to be recomputed every time). See L<API LISTING> later in
359this document for detailed descriptions.
360
361The following macros must always be used to access the contents of hash
362entries. Note that the arguments to these macros must be simple
363variables, since they may get evaluated more than once. See
364L<API LISTING> later in this document for detailed descriptions of these
365macros.
366
367 HePV(HE* he, STRLEN len)
368 HeVAL(HE* he)
369 HeHASH(HE* he)
370 HeSVKEY(HE* he)
371 HeSVKEY_force(HE* he)
372 HeSVKEY_set(HE* he, SV* sv)
373
374These two lower level macros are defined, but must only be used when
375dealing with keys that are not C<SV*>s:
376
377 HeKEY(HE* he)
378 HeKLEN(HE* he)
379
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380Note that both C<hv_store> and C<hv_store_ent> do not increment the
381reference count of the stored C<val>, which is the caller's responsibility.
382If these functions return a NULL value, the caller will usually have to
383decrement the reference count of C<val> to avoid a memory leak.
1e422769 384
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385=head2 References
386
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387References are a special type of scalar that point to other data types
388(including references).
a0d0e21e 389
07fa94a1 390To create a reference, use either of the following functions:
a0d0e21e 391
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392 SV* newRV_inc((SV*) thing);
393 SV* newRV_noinc((SV*) thing);
a0d0e21e 394
5f05dabc 395The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
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396functions are identical except that C<newRV_inc> increments the reference
397count of the C<thing>, while C<newRV_noinc> does not. For historical
398reasons, C<newRV> is a synonym for C<newRV_inc>.
399
400Once you have a reference, you can use the following macro to dereference
401the reference:
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402
403 SvRV(SV*)
404
405then call the appropriate routines, casting the returned C<SV*> to either an
d1b91892 406C<AV*> or C<HV*>, if required.
a0d0e21e 407
d1b91892 408To determine if an SV is a reference, you can use the following macro:
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409
410 SvROK(SV*)
411
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412To discover what type of value the reference refers to, use the following
413macro and then check the return value.
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414
415 SvTYPE(SvRV(SV*))
416
417The most useful types that will be returned are:
418
419 SVt_IV Scalar
420 SVt_NV Scalar
421 SVt_PV Scalar
5f05dabc 422 SVt_RV Scalar
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423 SVt_PVAV Array
424 SVt_PVHV Hash
425 SVt_PVCV Code
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426 SVt_PVGV Glob (possible a file handle)
427 SVt_PVMG Blessed or Magical Scalar
428
429 See the sv.h header file for more details.
d1b91892 430
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431=head2 Blessed References and Class Objects
432
433References are also used to support object-oriented programming. In the
434OO lexicon, an object is simply a reference that has been blessed into a
435package (or class). Once blessed, the programmer may now use the reference
436to access the various methods in the class.
437
438A reference can be blessed into a package with the following function:
439
440 SV* sv_bless(SV* sv, HV* stash);
441
442The C<sv> argument must be a reference. The C<stash> argument specifies
3fe9a6f1 443which class the reference will belong to. See
2ae324a7 444L<Stashes and Globs> for information on converting class names into stashes.
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445
446/* Still under construction */
447
448Upgrades rv to reference if not already one. Creates new SV for rv to
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449point to. If C<classname> is non-null, the SV is blessed into the specified
450class. SV is returned.
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451
452 SV* newSVrv(SV* rv, char* classname);
453
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454Copies integer or double into an SV whose reference is C<rv>. SV is blessed
455if C<classname> is non-null.
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456
457 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
458 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
459
5f05dabc 460Copies the pointer value (I<the address, not the string!>) into an SV whose
8ebc5c01 461reference is rv. SV is blessed if C<classname> is non-null.
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462
463 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
464
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465Copies string into an SV whose reference is C<rv>. Set length to 0 to let
466Perl calculate the string length. SV is blessed if C<classname> is non-null.
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467
468 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
469
470 int sv_isa(SV* sv, char* name);
471 int sv_isobject(SV* sv);
472
5f05dabc 473=head2 Creating New Variables
cb1a09d0 474
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475To create a new Perl variable with an undef value which can be accessed from
476your Perl script, use the following routines, depending on the variable type.
cb1a09d0 477
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478 SV* perl_get_sv("package::varname", TRUE);
479 AV* perl_get_av("package::varname", TRUE);
480 HV* perl_get_hv("package::varname", TRUE);
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481
482Notice the use of TRUE as the second parameter. The new variable can now
483be set, using the routines appropriate to the data type.
484
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485There are additional macros whose values may be bitwise OR'ed with the
486C<TRUE> argument to enable certain extra features. Those bits are:
cb1a09d0 487
5f05dabc 488 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
54310121 489 "Name <varname> used only once: possible typo" warning.
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490 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
491 the variable did not exist before the function was called.
cb1a09d0 492
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493If you do not specify a package name, the variable is created in the current
494package.
cb1a09d0 495
5f05dabc 496=head2 Reference Counts and Mortality
a0d0e21e 497
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498Perl uses an reference count-driven garbage collection mechanism. SVs,
499AVs, or HVs (xV for short in the following) start their life with a
55497cff 500reference count of 1. If the reference count of an xV ever drops to 0,
07fa94a1 501then it will be destroyed and its memory made available for reuse.
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502
503This normally doesn't happen at the Perl level unless a variable is
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504undef'ed or the last variable holding a reference to it is changed or
505overwritten. At the internal level, however, reference counts can be
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506manipulated with the following macros:
507
508 int SvREFCNT(SV* sv);
5f05dabc 509 SV* SvREFCNT_inc(SV* sv);
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510 void SvREFCNT_dec(SV* sv);
511
512However, there is one other function which manipulates the reference
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513count of its argument. The C<newRV_inc> function, you will recall,
514creates a reference to the specified argument. As a side effect,
515it increments the argument's reference count. If this is not what
516you want, use C<newRV_noinc> instead.
517
518For example, imagine you want to return a reference from an XSUB function.
519Inside the XSUB routine, you create an SV which initially has a reference
520count of one. Then you call C<newRV_inc>, passing it the just-created SV.
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521This returns the reference as a new SV, but the reference count of the
522SV you passed to C<newRV_inc> has been incremented to two. Now you
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523return the reference from the XSUB routine and forget about the SV.
524But Perl hasn't! Whenever the returned reference is destroyed, the
525reference count of the original SV is decreased to one and nothing happens.
526The SV will hang around without any way to access it until Perl itself
527terminates. This is a memory leak.
5f05dabc
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528
529The correct procedure, then, is to use C<newRV_noinc> instead of
faed5253
JO
530C<newRV_inc>. Then, if and when the last reference is destroyed,
531the reference count of the SV will go to zero and it will be destroyed,
07fa94a1 532stopping any memory leak.
55497cff 533
5f05dabc 534There are some convenience functions available that can help with the
54310121 535destruction of xVs. These functions introduce the concept of "mortality".
07fa94a1
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536An xV that is mortal has had its reference count marked to be decremented,
537but not actually decremented, until "a short time later". Generally the
538term "short time later" means a single Perl statement, such as a call to
54310121 539an XSUB function. The actual determinant for when mortal xVs have their
07fa94a1
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540reference count decremented depends on two macros, SAVETMPS and FREETMPS.
541See L<perlcall> and L<perlxs> for more details on these macros.
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542
543"Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
544However, if you mortalize a variable twice, the reference count will
545later be decremented twice.
546
547You should be careful about creating mortal variables. Strange things
548can happen if you make the same value mortal within multiple contexts,
5f05dabc 549or if you make a variable mortal multiple times.
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550
551To create a mortal variable, use the functions:
552
553 SV* sv_newmortal()
554 SV* sv_2mortal(SV*)
555 SV* sv_mortalcopy(SV*)
556
5f05dabc
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557The first call creates a mortal SV, the second converts an existing
558SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
559third creates a mortal copy of an existing SV.
a0d0e21e 560
54310121 561The mortal routines are not just for SVs -- AVs and HVs can be
faed5253 562made mortal by passing their address (type-casted to C<SV*>) to the
07fa94a1 563C<sv_2mortal> or C<sv_mortalcopy> routines.
a0d0e21e 564
5f05dabc 565=head2 Stashes and Globs
a0d0e21e 566
aa689395
PP
567A "stash" is a hash that contains all of the different objects that
568are contained within a package. Each key of the stash is a symbol
569name (shared by all the different types of objects that have the same
570name), and each value in the hash table is a GV (Glob Value). This GV
571in turn contains references to the various objects of that name,
572including (but not limited to) the following:
cb1a09d0 573
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574 Scalar Value
575 Array Value
576 Hash Value
577 File Handle
578 Directory Handle
579 Format
580 Subroutine
581
5f05dabc
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582There is a single stash called "defstash" that holds the items that exist
583in the "main" package. To get at the items in other packages, append the
584string "::" to the package name. The items in the "Foo" package are in
585the stash "Foo::" in defstash. The items in the "Bar::Baz" package are
586in the stash "Baz::" in "Bar::"'s stash.
a0d0e21e 587
d1b91892 588To get the stash pointer for a particular package, use the function:
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589
590 HV* gv_stashpv(char* name, I32 create)
591 HV* gv_stashsv(SV*, I32 create)
592
593The first function takes a literal string, the second uses the string stored
d1b91892 594in the SV. Remember that a stash is just a hash table, so you get back an
cb1a09d0 595C<HV*>. The C<create> flag will create a new package if it is set.
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596
597The name that C<gv_stash*v> wants is the name of the package whose symbol table
598you want. The default package is called C<main>. If you have multiply nested
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599packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
600language itself.
a0d0e21e
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601
602Alternately, if you have an SV that is a blessed reference, you can find
603out the stash pointer by using:
604
605 HV* SvSTASH(SvRV(SV*));
606
607then use the following to get the package name itself:
608
609 char* HvNAME(HV* stash);
610
5f05dabc
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611If you need to bless or re-bless an object you can use the following
612function:
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613
614 SV* sv_bless(SV*, HV* stash)
615
616where the first argument, an C<SV*>, must be a reference, and the second
617argument is a stash. The returned C<SV*> can now be used in the same way
618as any other SV.
619
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620For more information on references and blessings, consult L<perlref>.
621
54310121 622=head2 Double-Typed SVs
0a753a76
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623
624Scalar variables normally contain only one type of value, an integer,
625double, pointer, or reference. Perl will automatically convert the
626actual scalar data from the stored type into the requested type.
627
628Some scalar variables contain more than one type of scalar data. For
629example, the variable C<$!> contains either the numeric value of C<errno>
630or its string equivalent from either C<strerror> or C<sys_errlist[]>.
631
632To force multiple data values into an SV, you must do two things: use the
633C<sv_set*v> routines to add the additional scalar type, then set a flag
634so that Perl will believe it contains more than one type of data. The
635four macros to set the flags are:
636
637 SvIOK_on
638 SvNOK_on
639 SvPOK_on
640 SvROK_on
641
642The particular macro you must use depends on which C<sv_set*v> routine
643you called first. This is because every C<sv_set*v> routine turns on
644only the bit for the particular type of data being set, and turns off
645all the rest.
646
647For example, to create a new Perl variable called "dberror" that contains
648both the numeric and descriptive string error values, you could use the
649following code:
650
651 extern int dberror;
652 extern char *dberror_list;
653
654 SV* sv = perl_get_sv("dberror", TRUE);
655 sv_setiv(sv, (IV) dberror);
656 sv_setpv(sv, dberror_list[dberror]);
657 SvIOK_on(sv);
658
659If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
660macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
661
662=head2 Magic Variables
a0d0e21e 663
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664[This section still under construction. Ignore everything here. Post no
665bills. Everything not permitted is forbidden.]
666
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667Any SV may be magical, that is, it has special features that a normal
668SV does not have. These features are stored in the SV structure in a
5f05dabc 669linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
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670
671 struct magic {
672 MAGIC* mg_moremagic;
673 MGVTBL* mg_virtual;
674 U16 mg_private;
675 char mg_type;
676 U8 mg_flags;
677 SV* mg_obj;
678 char* mg_ptr;
679 I32 mg_len;
680 };
681
682Note this is current as of patchlevel 0, and could change at any time.
683
684=head2 Assigning Magic
685
686Perl adds magic to an SV using the sv_magic function:
687
688 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
689
690The C<sv> argument is a pointer to the SV that is to acquire a new magical
691feature.
692
693If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
694set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
695it to the beginning of the linked list of magical features. Any prior
696entry of the same type of magic is deleted. Note that this can be
5fb8527f 697overridden, and multiple instances of the same type of magic can be
d1b91892
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698associated with an SV.
699
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700The C<name> and C<namlen> arguments are used to associate a string with
701the magic, typically the name of a variable. C<namlen> is stored in the
702C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
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703copy of the name is stored in C<mg_ptr> field.
704
705The sv_magic function uses C<how> to determine which, if any, predefined
706"Magic Virtual Table" should be assigned to the C<mg_virtual> field.
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707See the "Magic Virtual Table" section below. The C<how> argument is also
708stored in the C<mg_type> field.
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709
710The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
711structure. If it is not the same as the C<sv> argument, the reference
712count of the C<obj> object is incremented. If it is the same, or if
04343c6d 713the C<how> argument is "#", or if it is a NULL pointer, then C<obj> is
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714merely stored, without the reference count being incremented.
715
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716There is also a function to add magic to an C<HV>:
717
718 void hv_magic(HV *hv, GV *gv, int how);
719
720This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
721
722To remove the magic from an SV, call the function sv_unmagic:
723
724 void sv_unmagic(SV *sv, int type);
725
726The C<type> argument should be equal to the C<how> value when the C<SV>
727was initially made magical.
728
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AD
729=head2 Magic Virtual Tables
730
731The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
732C<MGVTBL>, which is a structure of function pointers and stands for
733"Magic Virtual Table" to handle the various operations that might be
734applied to that variable.
735
736The C<MGVTBL> has five pointers to the following routine types:
737
738 int (*svt_get)(SV* sv, MAGIC* mg);
739 int (*svt_set)(SV* sv, MAGIC* mg);
740 U32 (*svt_len)(SV* sv, MAGIC* mg);
741 int (*svt_clear)(SV* sv, MAGIC* mg);
742 int (*svt_free)(SV* sv, MAGIC* mg);
743
744This MGVTBL structure is set at compile-time in C<perl.h> and there are
745currently 19 types (or 21 with overloading turned on). These different
746structures contain pointers to various routines that perform additional
747actions depending on which function is being called.
748
749 Function pointer Action taken
750 ---------------- ------------
751 svt_get Do something after the value of the SV is retrieved.
752 svt_set Do something after the SV is assigned a value.
753 svt_len Report on the SV's length.
754 svt_clear Clear something the SV represents.
755 svt_free Free any extra storage associated with the SV.
756
757For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
758to an C<mg_type> of '\0') contains:
759
760 { magic_get, magic_set, magic_len, 0, 0 }
761
762Thus, when an SV is determined to be magical and of type '\0', if a get
763operation is being performed, the routine C<magic_get> is called. All
764the various routines for the various magical types begin with C<magic_>.
765
766The current kinds of Magic Virtual Tables are:
767
07fa94a1 768 mg_type MGVTBL Type of magical
5f05dabc 769 ------- ------ ----------------------------
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AD
770 \0 vtbl_sv Regexp???
771 A vtbl_amagic Operator Overloading
772 a vtbl_amagicelem Operator Overloading
773 c 0 Used in Operator Overloading
774 B vtbl_bm Boyer-Moore???
775 E vtbl_env %ENV hash
776 e vtbl_envelem %ENV hash element
777 g vtbl_mglob Regexp /g flag???
778 I vtbl_isa @ISA array
779 i vtbl_isaelem @ISA array element
780 L 0 (but sets RMAGICAL) Perl Module/Debugger???
781 l vtbl_dbline Debugger?
44a8e56a 782 o vtbl_collxfrm Locale transformation
d1b91892
AD
783 P vtbl_pack Tied Array or Hash
784 p vtbl_packelem Tied Array or Hash element
785 q vtbl_packelem Tied Scalar or Handle
786 S vtbl_sig Signal Hash
787 s vtbl_sigelem Signal Hash element
788 t vtbl_taint Taintedness
789 U vtbl_uvar ???
790 v vtbl_vec Vector
791 x vtbl_substr Substring???
e616eb7b 792 y vtbl_itervar Shadow "foreach" iterator variable
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AD
793 * vtbl_glob GV???
794 # vtbl_arylen Array Length
795 . vtbl_pos $. scalar variable
5f05dabc 796 ~ None Used by certain extensions
d1b91892 797
68dc0745
PP
798When an uppercase and lowercase letter both exist in the table, then the
799uppercase letter is used to represent some kind of composite type (a list
800or a hash), and the lowercase letter is used to represent an element of
d1b91892
AD
801that composite type.
802
5f05dabc
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803The '~' magic type is defined specifically for use by extensions and
804will not be used by perl itself. Extensions can use ~ magic to 'attach'
805private information to variables (typically objects). This is especially
806useful because there is no way for normal perl code to corrupt this
807private information (unlike using extra elements of a hash object).
808
809Note that because multiple extensions may be using ~ magic it is
810important for extensions to take extra care with it. Typically only
811using it on objects blessed into the same class as the extension
812is sufficient. It may also be appropriate to add an I32 'signature'
813at the top of the private data area and check that.
814
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AD
815=head2 Finding Magic
816
817 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
818
819This routine returns a pointer to the C<MAGIC> structure stored in the SV.
820If the SV does not have that magical feature, C<NULL> is returned. Also,
54310121 821if the SV is not of type SVt_PVMG, Perl may core dump.
d1b91892
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822
823 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
824
825This routine checks to see what types of magic C<sv> has. If the mg_type
68dc0745
PP
826field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
827the mg_type field is changed to be the lowercase letter.
a0d0e21e 828
04343c6d
GS
829=head2 Understanding the Magic of Tied Hashes and Arrays
830
831Tied hashes and arrays are magical beasts of the 'P' magic type.
832Proper usage of the array and hash access functions on them requires
833understanding a few caveats.
834
835The C<av_store> function, when given a tied array argument, merely
836copies the magic of the array onto the value to be "stored", using
837C<mg_copy>. It may also return NULL, indicating that the value did not
838actually need to be stored in the array. After a call to C<av_store> on
6e2bfd7f 839a tied array, the caller will usually need to call C<mg_set(val)> to
04343c6d
GS
840actually invoke the perl level "STORE" method on the TIEARRAY object. If
841C<av_store> did return NULL, a call to C<SvREFCNT_dec(val)> will also be
842usually necessary to avoid a memory leak.
843
844The previous paragraph is applicable verbatim to tied hash access using the
845C<hv_store> and C<hv_store_ent> functions as well.
846
847C<av_fetch> and the corresponding hash functions C<hv_fetch> and
848C<hv_fetch_ent> actually return an undefined mortal value whose magic
849has been initialized using C<mg_copy>. Note the value so returned does not
850need to be deallocated, as it is already mortal. But you will need to
851call C<mg_get()> on the returned value in order to actually invoke the
852perl level "FETCH" method on the underlying TIE object. Similarly,
853you may also call C<mg_set()> on the return value after possibly assigning
854a suitable value to it using C<sv_setsv>, which will invoke the "STORE"
855method on the TIE object.
856
857In other words, the array or hash fetch/store functions don't really
858fetch and store actual values in the case of tied arrays and hashes. They
859merely call C<mg_copy> to attach magic to the values that were meant to be
860"stored" or "fetched". Later calls to C<mg_get> and C<mg_set> actually
861do the job of invoking the TIE methods on the underlying objects. Thus
862the magic mechanism actually implements a kind of lazy access to arrays
863and hashes.
864
865Currently (as of perl version 5.004), use of the hash and array access
866functions requires the user to be aware of whether they are operating on
867"normal" hashes and arrays, or on their tied variants. A simpler API
868interface that provides transparent access to both tied and normal data
869types may be available in future versions.
870
871You would do well to understand that the TIEARRAY and TIEHASH interfaces
872are mere sugar to invoke some perl method calls while using the uniform hash
873and array syntax. The use of this sugar imposes some overhead (typically
874about two to four extra opcodes per FETCH/STORE operation, in addition to
875the creation of all the mortal variables required to invoke the methods).
876This overhead will be comparatively small if the TIE methods are themselves
877substantial, but if they are only a few statements long, the overhead
878will not be insignificant.
879
0a753a76 880=head1 Subroutines
a0d0e21e 881
68dc0745 882=head2 XSUBs and the Argument Stack
5f05dabc
PP
883
884The XSUB mechanism is a simple way for Perl programs to access C subroutines.
885An XSUB routine will have a stack that contains the arguments from the Perl
886program, and a way to map from the Perl data structures to a C equivalent.
887
888The stack arguments are accessible through the C<ST(n)> macro, which returns
889the C<n>'th stack argument. Argument 0 is the first argument passed in the
890Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
891an C<SV*> is used.
892
893Most of the time, output from the C routine can be handled through use of
894the RETVAL and OUTPUT directives. However, there are some cases where the
895argument stack is not already long enough to handle all the return values.
896An example is the POSIX tzname() call, which takes no arguments, but returns
897two, the local time zone's standard and summer time abbreviations.
898
899To handle this situation, the PPCODE directive is used and the stack is
900extended using the macro:
901
902 EXTEND(sp, num);
903
904where C<sp> is the stack pointer, and C<num> is the number of elements the
905stack should be extended by.
906
907Now that there is room on the stack, values can be pushed on it using the
54310121 908macros to push IVs, doubles, strings, and SV pointers respectively:
5f05dabc
PP
909
910 PUSHi(IV)
911 PUSHn(double)
912 PUSHp(char*, I32)
913 PUSHs(SV*)
914
915And now the Perl program calling C<tzname>, the two values will be assigned
916as in:
917
918 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
919
920An alternate (and possibly simpler) method to pushing values on the stack is
921to use the macros:
922
923 XPUSHi(IV)
924 XPUSHn(double)
925 XPUSHp(char*, I32)
926 XPUSHs(SV*)
927
928These macros automatically adjust the stack for you, if needed. Thus, you
929do not need to call C<EXTEND> to extend the stack.
930
931For more information, consult L<perlxs> and L<perlxstut>.
932
933=head2 Calling Perl Routines from within C Programs
a0d0e21e
LW
934
935There are four routines that can be used to call a Perl subroutine from
936within a C program. These four are:
937
938 I32 perl_call_sv(SV*, I32);
939 I32 perl_call_pv(char*, I32);
940 I32 perl_call_method(char*, I32);
941 I32 perl_call_argv(char*, I32, register char**);
942
d1b91892
AD
943The routine most often used is C<perl_call_sv>. The C<SV*> argument
944contains either the name of the Perl subroutine to be called, or a
945reference to the subroutine. The second argument consists of flags
946that control the context in which the subroutine is called, whether
947or not the subroutine is being passed arguments, how errors should be
948trapped, and how to treat return values.
a0d0e21e
LW
949
950All four routines return the number of arguments that the subroutine returned
951on the Perl stack.
952
d1b91892
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953When using any of these routines (except C<perl_call_argv>), the programmer
954must manipulate the Perl stack. These include the following macros and
955functions:
a0d0e21e
LW
956
957 dSP
958 PUSHMARK()
959 PUTBACK
960 SPAGAIN
961 ENTER
962 SAVETMPS
963 FREETMPS
964 LEAVE
965 XPUSH*()
cb1a09d0 966 POP*()
a0d0e21e 967
5f05dabc
PP
968For a detailed description of calling conventions from C to Perl,
969consult L<perlcall>.
a0d0e21e 970
5f05dabc 971=head2 Memory Allocation
a0d0e21e 972
5f05dabc
PP
973It is suggested that you use the version of malloc that is distributed
974with Perl. It keeps pools of various sizes of unallocated memory in
07fa94a1
JO
975order to satisfy allocation requests more quickly. However, on some
976platforms, it may cause spurious malloc or free errors.
d1b91892
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977
978 New(x, pointer, number, type);
979 Newc(x, pointer, number, type, cast);
980 Newz(x, pointer, number, type);
981
07fa94a1 982These three macros are used to initially allocate memory.
5f05dabc
PP
983
984The first argument C<x> was a "magic cookie" that was used to keep track
985of who called the macro, to help when debugging memory problems. However,
07fa94a1
JO
986the current code makes no use of this feature (most Perl developers now
987use run-time memory checkers), so this argument can be any number.
5f05dabc
PP
988
989The second argument C<pointer> should be the name of a variable that will
990point to the newly allocated memory.
d1b91892 991
d1b91892
AD
992The third and fourth arguments C<number> and C<type> specify how many of
993the specified type of data structure should be allocated. The argument
994C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
995should be used if the C<pointer> argument is different from the C<type>
996argument.
997
998Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
999to zero out all the newly allocated memory.
1000
1001 Renew(pointer, number, type);
1002 Renewc(pointer, number, type, cast);
1003 Safefree(pointer)
1004
1005These three macros are used to change a memory buffer size or to free a
1006piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
1007match those of C<New> and C<Newc> with the exception of not needing the
1008"magic cookie" argument.
1009
1010 Move(source, dest, number, type);
1011 Copy(source, dest, number, type);
1012 Zero(dest, number, type);
1013
1014These three macros are used to move, copy, or zero out previously allocated
1015memory. The C<source> and C<dest> arguments point to the source and
1016destination starting points. Perl will move, copy, or zero out C<number>
1017instances of the size of the C<type> data structure (using the C<sizeof>
1018function).
a0d0e21e 1019
5f05dabc 1020=head2 PerlIO
ce3d39e2 1021
5f05dabc
PP
1022The most recent development releases of Perl has been experimenting with
1023removing Perl's dependency on the "normal" standard I/O suite and allowing
1024other stdio implementations to be used. This involves creating a new
1025abstraction layer that then calls whichever implementation of stdio Perl
68dc0745 1026was compiled with. All XSUBs should now use the functions in the PerlIO
5f05dabc
PP
1027abstraction layer and not make any assumptions about what kind of stdio
1028is being used.
1029
1030For a complete description of the PerlIO abstraction, consult L<perlapio>.
1031
8ebc5c01 1032=head2 Putting a C value on Perl stack
ce3d39e2
IZ
1033
1034A lot of opcodes (this is an elementary operation in the internal perl
1035stack machine) put an SV* on the stack. However, as an optimization
1036the corresponding SV is (usually) not recreated each time. The opcodes
1037reuse specially assigned SVs (I<target>s) which are (as a corollary)
1038not constantly freed/created.
1039
0a753a76 1040Each of the targets is created only once (but see
ce3d39e2
IZ
1041L<Scratchpads and recursion> below), and when an opcode needs to put
1042an integer, a double, or a string on stack, it just sets the
1043corresponding parts of its I<target> and puts the I<target> on stack.
1044
1045The macro to put this target on stack is C<PUSHTARG>, and it is
1046directly used in some opcodes, as well as indirectly in zillions of
1047others, which use it via C<(X)PUSH[pni]>.
1048
8ebc5c01 1049=head2 Scratchpads
ce3d39e2 1050
54310121 1051The question remains on when the SVs which are I<target>s for opcodes
5f05dabc
PP
1052are created. The answer is that they are created when the current unit --
1053a subroutine or a file (for opcodes for statements outside of
1054subroutines) -- is compiled. During this time a special anonymous Perl
ce3d39e2
IZ
1055array is created, which is called a scratchpad for the current
1056unit.
1057
54310121 1058A scratchpad keeps SVs which are lexicals for the current unit and are
ce3d39e2
IZ
1059targets for opcodes. One can deduce that an SV lives on a scratchpad
1060by looking on its flags: lexicals have C<SVs_PADMY> set, and
1061I<target>s have C<SVs_PADTMP> set.
1062
54310121
PP
1063The correspondence between OPs and I<target>s is not 1-to-1. Different
1064OPs in the compile tree of the unit can use the same target, if this
ce3d39e2
IZ
1065would not conflict with the expected life of the temporary.
1066
2ae324a7 1067=head2 Scratchpads and recursion
ce3d39e2
IZ
1068
1069In fact it is not 100% true that a compiled unit contains a pointer to
1070the scratchpad AV. In fact it contains a pointer to an AV of
1071(initially) one element, and this element is the scratchpad AV. Why do
1072we need an extra level of indirection?
1073
1074The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1075these can create several execution pointers going into the same
1076subroutine. For the subroutine-child not write over the temporaries
1077for the subroutine-parent (lifespan of which covers the call to the
1078child), the parent and the child should have different
1079scratchpads. (I<And> the lexicals should be separate anyway!)
1080
5f05dabc
PP
1081So each subroutine is born with an array of scratchpads (of length 1).
1082On each entry to the subroutine it is checked that the current
ce3d39e2
IZ
1083depth of the recursion is not more than the length of this array, and
1084if it is, new scratchpad is created and pushed into the array.
1085
1086The I<target>s on this scratchpad are C<undef>s, but they are already
1087marked with correct flags.
1088
0a753a76
PP
1089=head1 Compiled code
1090
1091=head2 Code tree
1092
1093Here we describe the internal form your code is converted to by
1094Perl. Start with a simple example:
1095
1096 $a = $b + $c;
1097
1098This is converted to a tree similar to this one:
1099
1100 assign-to
1101 / \
1102 + $a
1103 / \
1104 $b $c
1105
1106(but slightly more complicated). This tree reflect the way Perl
1107parsed your code, but has nothing to do with the execution order.
1108There is an additional "thread" going through the nodes of the tree
1109which shows the order of execution of the nodes. In our simplified
1110example above it looks like:
1111
1112 $b ---> $c ---> + ---> $a ---> assign-to
1113
1114But with the actual compile tree for C<$a = $b + $c> it is different:
1115some nodes I<optimized away>. As a corollary, though the actual tree
1116contains more nodes than our simplified example, the execution order
1117is the same as in our example.
1118
1119=head2 Examining the tree
1120
1121If you have your perl compiled for debugging (usually done with C<-D
1122optimize=-g> on C<Configure> command line), you may examine the
1123compiled tree by specifying C<-Dx> on the Perl command line. The
1124output takes several lines per node, and for C<$b+$c> it looks like
1125this:
1126
1127 5 TYPE = add ===> 6
1128 TARG = 1
1129 FLAGS = (SCALAR,KIDS)
1130 {
1131 TYPE = null ===> (4)
1132 (was rv2sv)
1133 FLAGS = (SCALAR,KIDS)
1134 {
1135 3 TYPE = gvsv ===> 4
1136 FLAGS = (SCALAR)
1137 GV = main::b
1138 }
1139 }
1140 {
1141 TYPE = null ===> (5)
1142 (was rv2sv)
1143 FLAGS = (SCALAR,KIDS)
1144 {
1145 4 TYPE = gvsv ===> 5
1146 FLAGS = (SCALAR)
1147 GV = main::c
1148 }
1149 }
1150
1151This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1152not optimized away (one per number in the left column). The immediate
1153children of the given node correspond to C<{}> pairs on the same level
1154of indentation, thus this listing corresponds to the tree:
1155
1156 add
1157 / \
1158 null null
1159 | |
1160 gvsv gvsv
1161
1162The execution order is indicated by C<===E<gt>> marks, thus it is C<3
11634 5 6> (node C<6> is not included into above listing), i.e.,
1164C<gvsv gvsv add whatever>.
1165
1166=head2 Compile pass 1: check routines
1167
1168The tree is created by the I<pseudo-compiler> while yacc code feeds it
1169the constructions it recognizes. Since yacc works bottom-up, so does
1170the first pass of perl compilation.
1171
1172What makes this pass interesting for perl developers is that some
1173optimization may be performed on this pass. This is optimization by
1174so-called I<check routines>. The correspondence between node names
1175and corresponding check routines is described in F<opcode.pl> (do not
1176forget to run C<make regen_headers> if you modify this file).
1177
1178A check routine is called when the node is fully constructed except
1179for the execution-order thread. Since at this time there is no
1180back-links to the currently constructed node, one can do most any
1181operation to the top-level node, including freeing it and/or creating
1182new nodes above/below it.
1183
1184The check routine returns the node which should be inserted into the
1185tree (if the top-level node was not modified, check routine returns
1186its argument).
1187
1188By convention, check routines have names C<ck_*>. They are usually
1189called from C<new*OP> subroutines (or C<convert>) (which in turn are
1190called from F<perly.y>).
1191
1192=head2 Compile pass 1a: constant folding
1193
1194Immediately after the check routine is called the returned node is
1195checked for being compile-time executable. If it is (the value is
1196judged to be constant) it is immediately executed, and a I<constant>
1197node with the "return value" of the corresponding subtree is
1198substituted instead. The subtree is deleted.
1199
1200If constant folding was not performed, the execution-order thread is
1201created.
1202
1203=head2 Compile pass 2: context propagation
1204
1205When a context for a part of compile tree is known, it is propagated
1206down through the tree. Aat this time the context can have 5 values
1207(instead of 2 for runtime context): void, boolean, scalar, list, and
1208lvalue. In contrast with the pass 1 this pass is processed from top
1209to bottom: a node's context determines the context for its children.
1210
1211Additional context-dependent optimizations are performed at this time.
1212Since at this moment the compile tree contains back-references (via
1213"thread" pointers), nodes cannot be free()d now. To allow
1214optimized-away nodes at this stage, such nodes are null()ified instead
1215of free()ing (i.e. their type is changed to OP_NULL).
1216
1217=head2 Compile pass 3: peephole optimization
1218
1219After the compile tree for a subroutine (or for an C<eval> or a file)
1220is created, an additional pass over the code is performed. This pass
1221is neither top-down or bottom-up, but in the execution order (with
1222additional compilications for conditionals). These optimizations are
1223done in the subroutine peep(). Optimizations performed at this stage
1224are subject to the same restrictions as in the pass 2.
1225
1226=head1 API LISTING
a0d0e21e 1227
cb1a09d0
AD
1228This is a listing of functions, macros, flags, and variables that may be
1229useful to extension writers or that may be found while reading other
1230extensions.
a0d0e21e 1231
cb1a09d0 1232=over 8
a0d0e21e 1233
cb1a09d0
AD
1234=item AvFILL
1235
1236See C<av_len>.
1237
1238=item av_clear
1239
0146554f
GA
1240Clears an array, making it empty. Does not free the memory used by the
1241array itself.
cb1a09d0
AD
1242
1243 void av_clear _((AV* ar));
1244
1245=item av_extend
1246
1247Pre-extend an array. The C<key> is the index to which the array should be
1248extended.
1249
1250 void av_extend _((AV* ar, I32 key));
1251
1252=item av_fetch
1253
1254Returns the SV at the specified index in the array. The C<key> is the
1255index. If C<lval> is set then the fetch will be part of a store. Check
1256that the return value is non-null before dereferencing it to a C<SV*>.
1257
04343c6d
GS
1258See L<Understanding the Magic of Tied Hashes and Arrays> for more
1259information on how to use this function on tied arrays.
1260
cb1a09d0
AD
1261 SV** av_fetch _((AV* ar, I32 key, I32 lval));
1262
1263=item av_len
1264
1265Returns the highest index in the array. Returns -1 if the array is empty.
1266
1267 I32 av_len _((AV* ar));
1268
1269=item av_make
1270
5fb8527f
PP
1271Creates a new AV and populates it with a list of SVs. The SVs are copied
1272into the array, so they may be freed after the call to av_make. The new AV
5f05dabc 1273will have a reference count of 1.
cb1a09d0
AD
1274
1275 AV* av_make _((I32 size, SV** svp));
1276
1277=item av_pop
1278
1279Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
1280empty.
1281
1282 SV* av_pop _((AV* ar));
1283
1284=item av_push
1285
5fb8527f
PP
1286Pushes an SV onto the end of the array. The array will grow automatically
1287to accommodate the addition.
cb1a09d0
AD
1288
1289 void av_push _((AV* ar, SV* val));
1290
1291=item av_shift
1292
1293Shifts an SV off the beginning of the array.
1294
1295 SV* av_shift _((AV* ar));
1296
1297=item av_store
1298
1299Stores an SV in an array. The array index is specified as C<key>. The
04343c6d
GS
1300return value will be NULL if the operation failed or if the value did not
1301need to be actually stored within the array (as in the case of tied arrays).
1302Otherwise it can be dereferenced to get the original C<SV*>. Note that the
1303caller is responsible for suitably incrementing the reference count of C<val>
1304before the call, and decrementing it if the function returned NULL.
1305
1306See L<Understanding the Magic of Tied Hashes and Arrays> for more
1307information on how to use this function on tied arrays.
cb1a09d0
AD
1308
1309 SV** av_store _((AV* ar, I32 key, SV* val));
1310
1311=item av_undef
1312
0146554f 1313Undefines the array. Frees the memory used by the array itself.
cb1a09d0
AD
1314
1315 void av_undef _((AV* ar));
1316
1317=item av_unshift
1318
0146554f
GA
1319Unshift the given number of C<undef> values onto the beginning of the
1320array. The array will grow automatically to accommodate the addition.
1321You must then use C<av_store> to assign values to these new elements.
cb1a09d0
AD
1322
1323 void av_unshift _((AV* ar, I32 num));
1324
1325=item CLASS
1326
1327Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
5fb8527f
PP
1328constructor. This is always a C<char*>. See C<THIS> and
1329L<perlxs/"Using XS With C++">.
cb1a09d0
AD
1330
1331=item Copy
1332
1333The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1334source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 1335the type. May fail on overlapping copies. See also C<Move>.
cb1a09d0
AD
1336
1337 (void) Copy( s, d, n, t );
1338
1339=item croak
1340
1341This is the XSUB-writer's interface to Perl's C<die> function. Use this
1342function the same way you use the C C<printf> function. See C<warn>.
1343
1344=item CvSTASH
1345
1346Returns the stash of the CV.
1347
1348 HV * CvSTASH( SV* sv )
1349
1350=item DBsingle
1351
1352When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1353boolean which indicates whether subs are being single-stepped.
5fb8527f
PP
1354Single-stepping is automatically turned on after every step. This is the C
1355variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
cb1a09d0
AD
1356
1357=item DBsub
1358
1359When Perl is run in debugging mode, with the B<-d> switch, this GV contains
5fb8527f
PP
1360the SV which holds the name of the sub being debugged. This is the C
1361variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
cb1a09d0
AD
1362The sub name can be found by
1363
1364 SvPV( GvSV( DBsub ), na )
1365
5fb8527f
PP
1366=item DBtrace
1367
1368Trace variable used when Perl is run in debugging mode, with the B<-d>
1369switch. This is the C variable which corresponds to Perl's $DB::trace
1370variable. See C<DBsingle>.
1371
cb1a09d0
AD
1372=item dMARK
1373
5fb8527f
PP
1374Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1375C<dORIGMARK>.
cb1a09d0
AD
1376
1377=item dORIGMARK
1378
1379Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1380
5fb8527f
PP
1381=item dowarn
1382
1383The C variable which corresponds to Perl's $^W warning variable.
1384
cb1a09d0
AD
1385=item dSP
1386
5fb8527f 1387Declares a stack pointer variable, C<sp>, for the XSUB. See C<SP>.
cb1a09d0
AD
1388
1389=item dXSARGS
1390
1391Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1392usually handled automatically by C<xsubpp>. Declares the C<items> variable
1393to indicate the number of items on the stack.
1394
5fb8527f
PP
1395=item dXSI32
1396
1397Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1398handled automatically by C<xsubpp>.
1399
1400=item dXSI32
1401
1402Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1403handled automatically by C<xsubpp>.
1404
cb1a09d0
AD
1405=item ENTER
1406
1407Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1408
1409 ENTER;
1410
1411=item EXTEND
1412
1413Used to extend the argument stack for an XSUB's return values.
1414
1415 EXTEND( sp, int x );
1416
1417=item FREETMPS
1418
1419Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1420L<perlcall>.
1421
1422 FREETMPS;
1423
1424=item G_ARRAY
1425
54310121 1426Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
cb1a09d0
AD
1427
1428=item G_DISCARD
1429
1430Indicates that arguments returned from a callback should be discarded. See
1431L<perlcall>.
1432
1433=item G_EVAL
1434
1435Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1436
1437=item GIMME
1438
54310121
PP
1439A backward-compatible version of C<GIMME_V> which can only return
1440C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
1441
1442=item GIMME_V
1443
1444The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
1445C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
1446context, respectively.
cb1a09d0
AD
1447
1448=item G_NOARGS
1449
1450Indicates that no arguments are being sent to a callback. See L<perlcall>.
1451
1452=item G_SCALAR
1453
54310121
PP
1454Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
1455
1456=item G_VOID
1457
1458Used to indicate void context. See C<GIMME_V> and L<perlcall>.
cb1a09d0 1459
faed5253
JO
1460=item gv_fetchmeth
1461
1462Returns the glob with the given C<name> and a defined subroutine or
9607fc9c
PP
1463C<NULL>. The glob lives in the given C<stash>, or in the stashes
1464accessable via @ISA and @<UNIVERSAL>.
faed5253 1465
9607fc9c 1466The argument C<level> should be either 0 or -1. If C<level==0>, as a
0a753a76
PP
1467side-effect creates a glob with the given C<name> in the given
1468C<stash> which in the case of success contains an alias for the
1469subroutine, and sets up caching info for this glob. Similarly for all
1470the searched stashes.
1471
9607fc9c
PP
1472This function grants C<"SUPER"> token as a postfix of the stash name.
1473
0a753a76
PP
1474The GV returned from C<gv_fetchmeth> may be a method cache entry,
1475which is not visible to Perl code. So when calling C<perl_call_sv>,
1476you should not use the GV directly; instead, you should use the
1477method's CV, which can be obtained from the GV with the C<GvCV> macro.
faed5253
JO
1478
1479 GV* gv_fetchmeth _((HV* stash, char* name, STRLEN len, I32 level));
1480
1481=item gv_fetchmethod
1482
dc848c6f
PP
1483=item gv_fetchmethod_autoload
1484
faed5253 1485Returns the glob which contains the subroutine to call to invoke the
dc848c6f
PP
1486method on the C<stash>. In fact in the presense of autoloading this may
1487be the glob for "AUTOLOAD". In this case the corresponding variable
faed5253
JO
1488$AUTOLOAD is already setup.
1489
dc848c6f
PP
1490The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
1491lookup is performed if the given method is not present: non-zero means
1492yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
1493C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
1494non-zero C<autoload> parameter.
1495
1496These functions grant C<"SUPER"> token as a prefix of the method name.
1497
1498Note that if you want to keep the returned glob for a long time, you
1499need to check for it being "AUTOLOAD", since at the later time the call
faed5253
JO
1500may load a different subroutine due to $AUTOLOAD changing its value.
1501Use the glob created via a side effect to do this.
1502
dc848c6f
PP
1503These functions have the same side-effects and as C<gv_fetchmeth> with
1504C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
0a753a76 1505The warning against passing the GV returned by C<gv_fetchmeth> to
dc848c6f 1506C<perl_call_sv> apply equally to these functions.
faed5253
JO
1507
1508 GV* gv_fetchmethod _((HV* stash, char* name));
dc848c6f
PP
1509 GV* gv_fetchmethod_autoload _((HV* stash, char* name,
1510 I32 autoload));
faed5253 1511
cb1a09d0
AD
1512=item gv_stashpv
1513
1514Returns a pointer to the stash for a specified package. If C<create> is set
1515then the package will be created if it does not already exist. If C<create>
1516is not set and the package does not exist then NULL is returned.
1517
1518 HV* gv_stashpv _((char* name, I32 create));
1519
1520=item gv_stashsv
1521
1522Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1523
1524 HV* gv_stashsv _((SV* sv, I32 create));
1525
e5581bf4 1526=item GvSV
cb1a09d0 1527
e5581bf4 1528Return the SV from the GV.
44a8e56a 1529
1e422769
PP
1530=item HEf_SVKEY
1531
1532This flag, used in the length slot of hash entries and magic
1533structures, specifies the structure contains a C<SV*> pointer where a
1534C<char*> pointer is to be expected. (For information only--not to be used).
1535
1e422769
PP
1536=item HeHASH
1537
1538Returns the computed hash (type C<U32>) stored in the hash entry.
1539
1540 HeHASH(HE* he)
1541
1542=item HeKEY
1543
1544Returns the actual pointer stored in the key slot of the hash entry.
1545The pointer may be either C<char*> or C<SV*>, depending on the value of
1546C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1547are usually preferable for finding the value of a key.
1548
1549 HeKEY(HE* he)
1550
1551=item HeKLEN
1552
1553If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1554holds an C<SV*> key. Otherwise, holds the actual length of the key.
1555Can be assigned to. The C<HePV()> macro is usually preferable for finding
1556key lengths.
1557
1558 HeKLEN(HE* he)
1559
1560=item HePV
1561
1562Returns the key slot of the hash entry as a C<char*> value, doing any
1563necessary dereferencing of possibly C<SV*> keys. The length of
1564the string is placed in C<len> (this is a macro, so do I<not> use
1565C<&len>). If you do not care about what the length of the key is,
1566you may use the global variable C<na>. Remember though, that hash
1567keys in perl are free to contain embedded nulls, so using C<strlen()>
1568or similar is not a good way to find the length of hash keys.
1569This is very similar to the C<SvPV()> macro described elsewhere in
1570this document.
1571
1572 HePV(HE* he, STRLEN len)
1573
1574=item HeSVKEY
1575
1576Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1577does not contain an C<SV*> key.
1578
1579 HeSVKEY(HE* he)
1580
1581=item HeSVKEY_force
1582
1583Returns the key as an C<SV*>. Will create and return a temporary
1584mortal C<SV*> if the hash entry contains only a C<char*> key.
1585
1586 HeSVKEY_force(HE* he)
1587
1588=item HeSVKEY_set
1589
1590Sets the key to a given C<SV*>, taking care to set the appropriate flags
1591to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1592
1593 HeSVKEY_set(HE* he, SV* sv)
1594
1595=item HeVAL
1596
1597Returns the value slot (type C<SV*>) stored in the hash entry.
1598
1599 HeVAL(HE* he)
1600
cb1a09d0
AD
1601=item hv_clear
1602
1603Clears a hash, making it empty.
1604
1605 void hv_clear _((HV* tb));
1606
68dc0745
PP
1607=item hv_delayfree_ent
1608
1609Releases a hash entry, such as while iterating though the hash, but
1610delays actual freeing of key and value until the end of the current
1611statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
1612and C<hv_free_ent>.
1613
1614 void hv_delayfree_ent _((HV* hv, HE* entry));
1615
cb1a09d0
AD
1616=item hv_delete
1617
1618Deletes a key/value pair in the hash. The value SV is removed from the hash
5fb8527f 1619and returned to the caller. The C<klen> is the length of the key. The
04343c6d 1620C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
cb1a09d0
AD
1621returned.
1622
1623 SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));
1624
1e422769
PP
1625=item hv_delete_ent
1626
1627Deletes a key/value pair in the hash. The value SV is removed from the hash
1628and returned to the caller. The C<flags> value will normally be zero; if set
04343c6d 1629to G_DISCARD then NULL will be returned. C<hash> can be a valid precomputed
1e422769
PP
1630hash value, or 0 to ask for it to be computed.
1631
1632 SV* hv_delete_ent _((HV* tb, SV* key, I32 flags, U32 hash));
1633
cb1a09d0
AD
1634=item hv_exists
1635
1636Returns a boolean indicating whether the specified hash key exists. The
5fb8527f 1637C<klen> is the length of the key.
cb1a09d0
AD
1638
1639 bool hv_exists _((HV* tb, char* key, U32 klen));
1640
1e422769
PP
1641=item hv_exists_ent
1642
1643Returns a boolean indicating whether the specified hash key exists. C<hash>
54310121 1644can be a valid precomputed hash value, or 0 to ask for it to be computed.
1e422769
PP
1645
1646 bool hv_exists_ent _((HV* tb, SV* key, U32 hash));
1647
cb1a09d0
AD
1648=item hv_fetch
1649
1650Returns the SV which corresponds to the specified key in the hash. The
5fb8527f 1651C<klen> is the length of the key. If C<lval> is set then the fetch will be
cb1a09d0
AD
1652part of a store. Check that the return value is non-null before
1653dereferencing it to a C<SV*>.
1654
04343c6d
GS
1655See L<Understanding the Magic of Tied Hashes and Arrays> for more
1656information on how to use this function on tied hashes.
1657
cb1a09d0
AD
1658 SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));
1659
1e422769
PP
1660=item hv_fetch_ent
1661
1662Returns the hash entry which corresponds to the specified key in the hash.
54310121 1663C<hash> must be a valid precomputed hash number for the given C<key>, or
1e422769
PP
16640 if you want the function to compute it. IF C<lval> is set then the
1665fetch will be part of a store. Make sure the return value is non-null
1666before accessing it. The return value when C<tb> is a tied hash
1667is a pointer to a static location, so be sure to make a copy of the
1668structure if you need to store it somewhere.
1669
04343c6d
GS
1670See L<Understanding the Magic of Tied Hashes and Arrays> for more
1671information on how to use this function on tied hashes.
1672
1e422769
PP
1673 HE* hv_fetch_ent _((HV* tb, SV* key, I32 lval, U32 hash));
1674
68dc0745
PP
1675=item hv_free_ent
1676
1677Releases a hash entry, such as while iterating though the hash. See
1678C<hv_iternext> and C<hv_delayfree_ent>.
1679
1680 void hv_free_ent _((HV* hv, HE* entry));
1681
cb1a09d0
AD
1682=item hv_iterinit
1683
1684Prepares a starting point to traverse a hash table.
1685
1686 I32 hv_iterinit _((HV* tb));
1687
1688=item hv_iterkey
1689
1690Returns the key from the current position of the hash iterator. See
1691C<hv_iterinit>.
1692
1693 char* hv_iterkey _((HE* entry, I32* retlen));
1694
1e422769 1695=item hv_iterkeysv
3fe9a6f1 1696
1e422769
PP
1697Returns the key as an C<SV*> from the current position of the hash
1698iterator. The return value will always be a mortal copy of the
1699key. Also see C<hv_iterinit>.
1700
1701 SV* hv_iterkeysv _((HE* entry));
1702
cb1a09d0
AD
1703=item hv_iternext
1704
1705Returns entries from a hash iterator. See C<hv_iterinit>.
1706
1707 HE* hv_iternext _((HV* tb));
1708
1709=item hv_iternextsv
1710
1711Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1712operation.
1713
1714 SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));
1715
1716=item hv_iterval
1717
1718Returns the value from the current position of the hash iterator. See
1719C<hv_iterkey>.
1720
1721 SV* hv_iterval _((HV* tb, HE* entry));
1722
1723=item hv_magic
1724
1725Adds magic to a hash. See C<sv_magic>.
1726
1727 void hv_magic _((HV* hv, GV* gv, int how));
1728
1729=item HvNAME
1730
1731Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1732
1733 char *HvNAME (HV* stash)
1734
1735=item hv_store
1736
1737Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
54310121 1738the length of the key. The C<hash> parameter is the precomputed hash
cb1a09d0 1739value; if it is zero then Perl will compute it. The return value will be
04343c6d
GS
1740NULL if the operation failed or if the value did not need to be actually
1741stored within the hash (as in the case of tied hashes). Otherwise it can
1742be dereferenced to get the original C<SV*>. Note that the caller is
1743responsible for suitably incrementing the reference count of C<val>
1744before the call, and decrementing it if the function returned NULL.
1745
1746See L<Understanding the Magic of Tied Hashes and Arrays> for more
1747information on how to use this function on tied hashes.
cb1a09d0
AD
1748
1749 SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
1750
1e422769
PP
1751=item hv_store_ent
1752
1753Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
54310121 1754parameter is the precomputed hash value; if it is zero then Perl will
1e422769 1755compute it. The return value is the new hash entry so created. It will be
04343c6d
GS
1756NULL if the operation failed or if the value did not need to be actually
1757stored within the hash (as in the case of tied hashes). Otherwise the
1758contents of the return value can be accessed using the C<He???> macros
1759described here. Note that the caller is responsible for suitably
1760incrementing the reference count of C<val> before the call, and decrementing
1761it if the function returned NULL.
1762
1763See L<Understanding the Magic of Tied Hashes and Arrays> for more
1764information on how to use this function on tied hashes.
1e422769
PP
1765
1766 HE* hv_store_ent _((HV* tb, SV* key, SV* val, U32 hash));
1767
cb1a09d0
AD
1768=item hv_undef
1769
1770Undefines the hash.
1771
1772 void hv_undef _((HV* tb));
1773
1774=item isALNUM
1775
1776Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
5f05dabc 1777character or digit.
cb1a09d0
AD
1778
1779 int isALNUM (char c)
1780
1781=item isALPHA
1782
5fb8527f 1783Returns a boolean indicating whether the C C<char> is an ascii alphabetic
cb1a09d0
AD
1784character.
1785
1786 int isALPHA (char c)
1787
1788=item isDIGIT
1789
1790Returns a boolean indicating whether the C C<char> is an ascii digit.
1791
1792 int isDIGIT (char c)
1793
1794=item isLOWER
1795
1796Returns a boolean indicating whether the C C<char> is a lowercase character.
1797
1798 int isLOWER (char c)
1799
1800=item isSPACE
1801
1802Returns a boolean indicating whether the C C<char> is whitespace.
1803
1804 int isSPACE (char c)
1805
1806=item isUPPER
1807
1808Returns a boolean indicating whether the C C<char> is an uppercase character.
1809
1810 int isUPPER (char c)
1811
1812=item items
1813
1814Variable which is setup by C<xsubpp> to indicate the number of items on the
5fb8527f
PP
1815stack. See L<perlxs/"Variable-length Parameter Lists">.
1816
1817=item ix
1818
1819Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
1820was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
cb1a09d0
AD
1821
1822=item LEAVE
1823
1824Closing bracket on a callback. See C<ENTER> and L<perlcall>.
1825
1826 LEAVE;
1827
1828=item MARK
1829
5fb8527f 1830Stack marker variable for the XSUB. See C<dMARK>.
cb1a09d0
AD
1831
1832=item mg_clear
1833
1834Clear something magical that the SV represents. See C<sv_magic>.
1835
1836 int mg_clear _((SV* sv));
1837
1838=item mg_copy
1839
1840Copies the magic from one SV to another. See C<sv_magic>.
1841
1842 int mg_copy _((SV *, SV *, char *, STRLEN));
1843
1844=item mg_find
1845
1846Finds the magic pointer for type matching the SV. See C<sv_magic>.
1847
1848 MAGIC* mg_find _((SV* sv, int type));
1849
1850=item mg_free
1851
1852Free any magic storage used by the SV. See C<sv_magic>.
1853
1854 int mg_free _((SV* sv));
1855
1856=item mg_get
1857
1858Do magic after a value is retrieved from the SV. See C<sv_magic>.
1859
1860 int mg_get _((SV* sv));
1861
1862=item mg_len
1863
1864Report on the SV's length. See C<sv_magic>.
1865
1866 U32 mg_len _((SV* sv));
1867
1868=item mg_magical
1869
1870Turns on the magical status of an SV. See C<sv_magic>.
1871
1872 void mg_magical _((SV* sv));
1873
1874=item mg_set
1875
1876Do magic after a value is assigned to the SV. See C<sv_magic>.
1877
1878 int mg_set _((SV* sv));
1879
1880=item Move
1881
1882The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
1883source, C<d> is the destination, C<n> is the number of items, and C<t> is
0146554f 1884the type. Can do overlapping moves. See also C<Copy>.
cb1a09d0
AD
1885
1886 (void) Move( s, d, n, t );
1887
1888=item na
1889
1890A variable which may be used with C<SvPV> to tell Perl to calculate the
1891string length.
1892
1893=item New
1894
1895The XSUB-writer's interface to the C C<malloc> function.
1896
1897 void * New( x, void *ptr, int size, type )
1898
1899=item Newc
1900
1901The XSUB-writer's interface to the C C<malloc> function, with cast.
1902
1903 void * Newc( x, void *ptr, int size, type, cast )
1904
1905=item Newz
1906
1907The XSUB-writer's interface to the C C<malloc> function. The allocated
1908memory is zeroed with C<memzero>.
1909
1910 void * Newz( x, void *ptr, int size, type )
1911
1912=item newAV
1913
5f05dabc 1914Creates a new AV. The reference count is set to 1.
cb1a09d0
AD
1915
1916 AV* newAV _((void));
1917
1918=item newHV
1919
5f05dabc 1920Creates a new HV. The reference count is set to 1.
cb1a09d0
AD
1921
1922 HV* newHV _((void));
1923
5f05dabc 1924=item newRV_inc
cb1a09d0 1925
5f05dabc 1926Creates an RV wrapper for an SV. The reference count for the original SV is
cb1a09d0
AD
1927incremented.
1928
5f05dabc
PP
1929 SV* newRV_inc _((SV* ref));
1930
1931For historical reasons, "newRV" is a synonym for "newRV_inc".
1932
1933=item newRV_noinc
1934
1935Creates an RV wrapper for an SV. The reference count for the original
1936SV is B<not> incremented.
1937
07fa94a1 1938 SV* newRV_noinc _((SV* ref));
cb1a09d0
AD
1939
1940=item newSV
1941
1942Creates a new SV. The C<len> parameter indicates the number of bytes of
68dc0745 1943preallocated string space the SV should have. The reference count for the
07fa94a1 1944new SV is set to 1.
cb1a09d0
AD
1945
1946 SV* newSV _((STRLEN len));
1947
1948=item newSViv
1949
07fa94a1
JO
1950Creates a new SV and copies an integer into it. The reference count for the
1951SV is set to 1.
cb1a09d0
AD
1952
1953 SV* newSViv _((IV i));
1954
1955=item newSVnv
1956
07fa94a1
JO
1957Creates a new SV and copies a double into it. The reference count for the
1958SV is set to 1.
cb1a09d0
AD
1959
1960 SV* newSVnv _((NV i));
1961
1962=item newSVpv
1963
07fa94a1
JO
1964Creates a new SV and copies a string into it. The reference count for the
1965SV is set to 1. If C<len> is zero then Perl will compute the length.
cb1a09d0
AD
1966
1967 SV* newSVpv _((char* s, STRLEN len));
1968
1969=item newSVrv
1970
1971Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
5fb8527f 1972it will be upgraded to one. If C<classname> is non-null then the new SV will
cb1a09d0 1973be blessed in the specified package. The new SV is returned and its
5f05dabc 1974reference count is 1.
8ebc5c01 1975
cb1a09d0
AD
1976 SV* newSVrv _((SV* rv, char* classname));
1977
1978=item newSVsv
1979
5fb8527f 1980Creates a new SV which is an exact duplicate of the original SV.
cb1a09d0
AD
1981
1982 SV* newSVsv _((SV* old));
1983
1984=item newXS
1985
1986Used by C<xsubpp> to hook up XSUBs as Perl subs.
1987
1988=item newXSproto
1989
1990Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
1991the subs.
1992
1993=item Nullav
1994
1995Null AV pointer.
1996
1997=item Nullch
1998
1999Null character pointer.
2000
2001=item Nullcv
2002
2003Null CV pointer.
2004
2005=item Nullhv
2006
2007Null HV pointer.
2008
2009=item Nullsv
2010
2011Null SV pointer.
2012
2013=item ORIGMARK
2014
2015The original stack mark for the XSUB. See C<dORIGMARK>.
2016
2017=item perl_alloc
2018
2019Allocates a new Perl interpreter. See L<perlembed>.
2020
2021=item perl_call_argv
2022
2023Performs a callback to the specified Perl sub. See L<perlcall>.
2024
2025 I32 perl_call_argv _((char* subname, I32 flags, char** argv));
2026
2027=item perl_call_method
2028
2029Performs a callback to the specified Perl method. The blessed object must
2030be on the stack. See L<perlcall>.
2031
2032 I32 perl_call_method _((char* methname, I32 flags));
2033
2034=item perl_call_pv
2035
2036Performs a callback to the specified Perl sub. See L<perlcall>.
2037
2038 I32 perl_call_pv _((char* subname, I32 flags));
2039
2040=item perl_call_sv
2041
2042Performs a callback to the Perl sub whose name is in the SV. See
2043L<perlcall>.
2044
2045 I32 perl_call_sv _((SV* sv, I32 flags));
2046
2047=item perl_construct
2048
2049Initializes a new Perl interpreter. See L<perlembed>.
2050
2051=item perl_destruct
2052
2053Shuts down a Perl interpreter. See L<perlembed>.
2054
2055=item perl_eval_sv
2056
2057Tells Perl to C<eval> the string in the SV.
2058
2059 I32 perl_eval_sv _((SV* sv, I32 flags));
2060
137443ea
PP
2061=item perl_eval_pv
2062
2063Tells Perl to C<eval> the given string and return an SV* result.
2064
2065 SV* perl_eval_pv _((char* p, I32 croak_on_error));
2066
cb1a09d0
AD
2067=item perl_free
2068
2069Releases a Perl interpreter. See L<perlembed>.
2070
2071=item perl_get_av
2072
2073Returns the AV of the specified Perl array. If C<create> is set and the
2074Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2075set and the variable does not exist then NULL is returned.
cb1a09d0
AD
2076
2077 AV* perl_get_av _((char* name, I32 create));
2078
2079=item perl_get_cv
2080
2081Returns the CV of the specified Perl sub. If C<create> is set and the Perl
2082variable does not exist then it will be created. If C<create> is not
04343c6d 2083set and the variable does not exist then NULL is returned.
cb1a09d0
AD
2084
2085 CV* perl_get_cv _((char* name, I32 create));
2086
2087=item perl_get_hv
2088
2089Returns the HV of the specified Perl hash. If C<create> is set and the Perl
2090variable does not exist then it will be created. If C<create> is not
04343c6d 2091set and the variable does not exist then NULL is returned.
cb1a09d0
AD
2092
2093 HV* perl_get_hv _((char* name, I32 create));
2094
2095=item perl_get_sv
2096
2097Returns the SV of the specified Perl scalar. If C<create> is set and the
2098Perl variable does not exist then it will be created. If C<create> is not
04343c6d 2099set and the variable does not exist then NULL is returned.
cb1a09d0
AD
2100
2101 SV* perl_get_sv _((char* name, I32 create));
2102
2103=item perl_parse
2104
2105Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2106
2107=item perl_require_pv
2108
2109Tells Perl to C<require> a module.
2110
2111 void perl_require_pv _((char* pv));
2112
2113=item perl_run
2114
2115Tells a Perl interpreter to run. See L<perlembed>.
2116
2117=item POPi
2118
2119Pops an integer off the stack.
2120
2121 int POPi();
2122
2123=item POPl
2124
2125Pops a long off the stack.
2126
2127 long POPl();
2128
2129=item POPp
2130
2131Pops a string off the stack.
2132
2133 char * POPp();
2134
2135=item POPn
2136
2137Pops a double off the stack.
2138
2139 double POPn();
2140
2141=item POPs
2142
2143Pops an SV off the stack.
2144
2145 SV* POPs();
2146
2147=item PUSHMARK
2148
2149Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2150
2151 PUSHMARK(p)
2152
2153=item PUSHi
2154
2155Push an integer onto the stack. The stack must have room for this element.
2156See C<XPUSHi>.
2157
2158 PUSHi(int d)
2159
2160=item PUSHn
2161
2162Push a double onto the stack. The stack must have room for this element.
2163See C<XPUSHn>.
2164
2165 PUSHn(double d)
2166
2167=item PUSHp
2168
2169Push a string onto the stack. The stack must have room for this element.
2170The C<len> indicates the length of the string. See C<XPUSHp>.
2171
2172 PUSHp(char *c, int len )
2173
2174=item PUSHs
2175
2176Push an SV onto the stack. The stack must have room for this element. See
2177C<XPUSHs>.
2178
2179 PUSHs(sv)
2180
2181=item PUTBACK
2182
2183Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2184See C<PUSHMARK> and L<perlcall> for other uses.
2185
2186 PUTBACK;
2187
2188=item Renew
2189
2190The XSUB-writer's interface to the C C<realloc> function.
2191
2192 void * Renew( void *ptr, int size, type )
2193
2194=item Renewc
2195
2196The XSUB-writer's interface to the C C<realloc> function, with cast.
2197
2198 void * Renewc( void *ptr, int size, type, cast )
2199
2200=item RETVAL
2201
2202Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
5fb8527f
PP
2203This is always the proper type for the XSUB.
2204See L<perlxs/"The RETVAL Variable">.
cb1a09d0
AD
2205
2206=item safefree
2207
2208The XSUB-writer's interface to the C C<free> function.
2209
2210=item safemalloc
2211
2212The XSUB-writer's interface to the C C<malloc> function.
2213
2214=item saferealloc
2215
2216The XSUB-writer's interface to the C C<realloc> function.
2217
2218=item savepv
2219
2220Copy a string to a safe spot. This does not use an SV.
2221
2222 char* savepv _((char* sv));
2223
2224=item savepvn
2225
2226Copy a string to a safe spot. The C<len> indicates number of bytes to
2227copy. This does not use an SV.
2228
2229 char* savepvn _((char* sv, I32 len));
2230
2231=item SAVETMPS
2232
2233Opening bracket for temporaries on a callback. See C<FREETMPS> and
2234L<perlcall>.
2235
2236 SAVETMPS;
2237
2238=item SP
2239
2240Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2241C<SPAGAIN>.
2242
2243=item SPAGAIN
2244
54310121 2245Refetch the stack pointer. Used after a callback. See L<perlcall>.
cb1a09d0
AD
2246
2247 SPAGAIN;
2248
2249=item ST
2250
2251Used to access elements on the XSUB's stack.
2252
2253 SV* ST(int x)
2254
2255=item strEQ
2256
2257Test two strings to see if they are equal. Returns true or false.
2258
2259 int strEQ( char *s1, char *s2 )
2260
2261=item strGE
2262
2263Test two strings to see if the first, C<s1>, is greater than or equal to the
2264second, C<s2>. Returns true or false.
2265
2266 int strGE( char *s1, char *s2 )
2267
2268=item strGT
2269
2270Test two strings to see if the first, C<s1>, is greater than the second,
2271C<s2>. Returns true or false.
2272
2273 int strGT( char *s1, char *s2 )
2274
2275=item strLE
2276
2277Test two strings to see if the first, C<s1>, is less than or equal to the
2278second, C<s2>. Returns true or false.
2279
2280 int strLE( char *s1, char *s2 )
2281
2282=item strLT
2283
2284Test two strings to see if the first, C<s1>, is less than the second,
2285C<s2>. Returns true or false.
2286
2287 int strLT( char *s1, char *s2 )
2288
2289=item strNE
2290
2291Test two strings to see if they are different. Returns true or false.
2292
2293 int strNE( char *s1, char *s2 )
2294
2295=item strnEQ
2296
2297Test two strings to see if they are equal. The C<len> parameter indicates
2298the number of bytes to compare. Returns true or false.
2299
2300 int strnEQ( char *s1, char *s2 )
2301
2302=item strnNE
2303
2304Test two strings to see if they are different. The C<len> parameter
2305indicates the number of bytes to compare. Returns true or false.
2306
2307 int strnNE( char *s1, char *s2, int len )
2308
2309=item sv_2mortal
2310
2311Marks an SV as mortal. The SV will be destroyed when the current context
2312ends.
2313
2314 SV* sv_2mortal _((SV* sv));
2315
2316=item sv_bless
2317
2318Blesses an SV into a specified package. The SV must be an RV. The package
07fa94a1
JO
2319must be designated by its stash (see C<gv_stashpv()>). The reference count
2320of the SV is unaffected.
cb1a09d0
AD
2321
2322 SV* sv_bless _((SV* sv, HV* stash));
2323
2324=item sv_catpv
2325
2326Concatenates the string onto the end of the string which is in the SV.
2327
2328 void sv_catpv _((SV* sv, char* ptr));
2329
2330=item sv_catpvn
2331
2332Concatenates the string onto the end of the string which is in the SV. The
2333C<len> indicates number of bytes to copy.
2334
2335 void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
2336
46fc3d4c
PP
2337=item sv_catpvf
2338
2339Processes its arguments like C<sprintf> and appends the formatted output
2340to an SV.
2341
2342 void sv_catpvf _((SV* sv, const char* pat, ...));
2343
cb1a09d0
AD
2344=item sv_catsv
2345
5fb8527f 2346Concatenates the string from SV C<ssv> onto the end of the string in SV
cb1a09d0
AD
2347C<dsv>.
2348
2349 void sv_catsv _((SV* dsv, SV* ssv));
2350
5fb8527f
PP
2351=item sv_cmp
2352
2353Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2354string in C<sv1> is less than, equal to, or greater than the string in
2355C<sv2>.
2356
2357 I32 sv_cmp _((SV* sv1, SV* sv2));
2358
2359=item sv_cmp
2360
2361Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2362string in C<sv1> is less than, equal to, or greater than the string in
2363C<sv2>.
2364
2365 I32 sv_cmp _((SV* sv1, SV* sv2));
2366
cb1a09d0
AD
2367=item SvCUR
2368
2369Returns the length of the string which is in the SV. See C<SvLEN>.
2370
2371 int SvCUR (SV* sv)
2372
2373=item SvCUR_set
2374
2375Set the length of the string which is in the SV. See C<SvCUR>.
2376
2377 SvCUR_set (SV* sv, int val )
2378
5fb8527f
PP
2379=item sv_dec
2380
5f05dabc 2381Auto-decrement of the value in the SV.
5fb8527f
PP
2382
2383 void sv_dec _((SV* sv));
2384
2385=item sv_dec
2386
5f05dabc 2387Auto-decrement of the value in the SV.
5fb8527f
PP
2388
2389 void sv_dec _((SV* sv));
2390
cb1a09d0
AD
2391=item SvEND
2392
2393Returns a pointer to the last character in the string which is in the SV.
2394See C<SvCUR>. Access the character as
2395
2396 *SvEND(sv)
2397
5fb8527f
PP
2398=item sv_eq
2399
2400Returns a boolean indicating whether the strings in the two SVs are
2401identical.
2402
2403 I32 sv_eq _((SV* sv1, SV* sv2));
2404
cb1a09d0
AD
2405=item SvGROW
2406
5fb8527f
PP
2407Expands the character buffer in the SV. Calls C<sv_grow> to perform the
2408expansion if necessary. Returns a pointer to the character buffer.
cb1a09d0
AD
2409
2410 char * SvGROW( SV* sv, int len )
2411
5fb8527f
PP
2412=item sv_grow
2413
2414Expands the character buffer in the SV. This will use C<sv_unref> and will
2415upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2416Use C<SvGROW>.
2417
2418=item sv_inc
2419
07fa94a1 2420Auto-increment of the value in the SV.
5fb8527f
PP
2421
2422 void sv_inc _((SV* sv));
2423
cb1a09d0
AD
2424=item SvIOK
2425
2426Returns a boolean indicating whether the SV contains an integer.
2427
2428 int SvIOK (SV* SV)
2429
2430=item SvIOK_off
2431
2432Unsets the IV status of an SV.
2433
2434 SvIOK_off (SV* sv)
2435
2436=item SvIOK_on
2437
2438Tells an SV that it is an integer.
2439
2440 SvIOK_on (SV* sv)
2441
5fb8527f
PP
2442=item SvIOK_only
2443
2444Tells an SV that it is an integer and disables all other OK bits.
2445
2446 SvIOK_on (SV* sv)
2447
2448=item SvIOK_only
2449
2450Tells an SV that it is an integer and disables all other OK bits.
2451
2452 SvIOK_on (SV* sv)
2453
cb1a09d0
AD
2454=item SvIOKp
2455
2456Returns a boolean indicating whether the SV contains an integer. Checks the
2457B<private> setting. Use C<SvIOK>.
2458
2459 int SvIOKp (SV* SV)
2460
2461=item sv_isa
2462
2463Returns a boolean indicating whether the SV is blessed into the specified
2464class. This does not know how to check for subtype, so it doesn't work in
2465an inheritance relationship.
2466
2467 int sv_isa _((SV* sv, char* name));
2468
2469=item SvIV
2470
2471Returns the integer which is in the SV.
2472
2473 int SvIV (SV* sv)
2474
2475=item sv_isobject
2476
2477Returns a boolean indicating whether the SV is an RV pointing to a blessed
2478object. If the SV is not an RV, or if the object is not blessed, then this
2479will return false.
2480
2481 int sv_isobject _((SV* sv));
2482
2483=item SvIVX
2484
2485Returns the integer which is stored in the SV.
2486
2487 int SvIVX (SV* sv);
2488
2489=item SvLEN
2490
2491Returns the size of the string buffer in the SV. See C<SvCUR>.
2492
2493 int SvLEN (SV* sv)
2494
5fb8527f
PP
2495=item sv_len
2496
2497Returns the length of the string in the SV. Use C<SvCUR>.
2498
2499 STRLEN sv_len _((SV* sv));
2500
2501=item sv_len
2502
2503Returns the length of the string in the SV. Use C<SvCUR>.
2504
2505 STRLEN sv_len _((SV* sv));
2506
cb1a09d0
AD
2507=item sv_magic
2508
2509Adds magic to an SV.
2510
2511 void sv_magic _((SV* sv, SV* obj, int how, char* name, I32 namlen));
2512
2513=item sv_mortalcopy
2514
2515Creates a new SV which is a copy of the original SV. The new SV is marked
5f05dabc 2516as mortal.
cb1a09d0
AD
2517
2518 SV* sv_mortalcopy _((SV* oldsv));
2519
2520=item SvOK
2521
2522Returns a boolean indicating whether the value is an SV.
2523
2524 int SvOK (SV* sv)
2525
2526=item sv_newmortal
2527
5f05dabc 2528Creates a new SV which is mortal. The reference count of the SV is set to 1.
cb1a09d0
AD
2529
2530 SV* sv_newmortal _((void));
2531
2532=item sv_no
2533
2534This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
2535
2536=item SvNIOK
2537
2538Returns a boolean indicating whether the SV contains a number, integer or
2539double.
2540
2541 int SvNIOK (SV* SV)
2542
2543=item SvNIOK_off
2544
2545Unsets the NV/IV status of an SV.
2546
2547 SvNIOK_off (SV* sv)
2548
2549=item SvNIOKp
2550
2551Returns a boolean indicating whether the SV contains a number, integer or
2552double. Checks the B<private> setting. Use C<SvNIOK>.
2553
2554 int SvNIOKp (SV* SV)
2555
2556=item SvNOK
2557
2558Returns a boolean indicating whether the SV contains a double.
2559
2560 int SvNOK (SV* SV)
2561
2562=item SvNOK_off
2563
2564Unsets the NV status of an SV.
2565
2566 SvNOK_off (SV* sv)
2567
2568=item SvNOK_on
2569
2570Tells an SV that it is a double.
2571
2572 SvNOK_on (SV* sv)
2573
5fb8527f
PP
2574=item SvNOK_only
2575
2576Tells an SV that it is a double and disables all other OK bits.
2577
2578 SvNOK_on (SV* sv)
2579
2580=item SvNOK_only
2581
2582Tells an SV that it is a double and disables all other OK bits.
2583
2584 SvNOK_on (SV* sv)
2585
cb1a09d0
AD
2586=item SvNOKp
2587
2588Returns a boolean indicating whether the SV contains a double. Checks the
2589B<private> setting. Use C<SvNOK>.
2590
2591 int SvNOKp (SV* SV)
2592
2593=item SvNV
2594
2595Returns the double which is stored in the SV.
2596
2597 double SvNV (SV* sv);
2598
2599=item SvNVX
2600
2601Returns the double which is stored in the SV.
2602
2603 double SvNVX (SV* sv);
2604
2605=item SvPOK
2606
2607Returns a boolean indicating whether the SV contains a character string.
2608
2609 int SvPOK (SV* SV)
2610
2611=item SvPOK_off
2612
2613Unsets the PV status of an SV.
2614
2615 SvPOK_off (SV* sv)
2616
2617=item SvPOK_on
2618
2619Tells an SV that it is a string.
2620
2621 SvPOK_on (SV* sv)
2622
5fb8527f
PP
2623=item SvPOK_only
2624
2625Tells an SV that it is a string and disables all other OK bits.
2626
2627 SvPOK_on (SV* sv)
2628
2629=item SvPOK_only
2630
2631Tells an SV that it is a string and disables all other OK bits.
2632
2633 SvPOK_on (SV* sv)
2634
cb1a09d0
AD
2635=item SvPOKp
2636
2637Returns a boolean indicating whether the SV contains a character string.
2638Checks the B<private> setting. Use C<SvPOK>.
2639
2640 int SvPOKp (SV* SV)
2641
2642=item SvPV
2643
2644Returns a pointer to the string in the SV, or a stringified form of the SV
2645if the SV does not contain a string. If C<len> is C<na> then Perl will
2646handle the length on its own.
2647
2648 char * SvPV (SV* sv, int len )
2649
2650=item SvPVX
2651
2652Returns a pointer to the string in the SV. The SV must contain a string.
2653
2654 char * SvPVX (SV* sv)
2655
2656=item SvREFCNT
2657
5f05dabc 2658Returns the value of the object's reference count.
cb1a09d0
AD
2659
2660 int SvREFCNT (SV* sv);
2661
2662=item SvREFCNT_dec
2663
5f05dabc 2664Decrements the reference count of the given SV.
cb1a09d0
AD
2665
2666 void SvREFCNT_dec (SV* sv)
2667
2668=item SvREFCNT_inc
2669
5f05dabc 2670Increments the reference count of the given SV.
cb1a09d0
AD
2671
2672 void SvREFCNT_inc (SV* sv)
2673
2674=item SvROK
2675
2676Tests if the SV is an RV.
2677
2678 int SvROK (SV* sv)
2679
2680=item SvROK_off
2681
2682Unsets the RV status of an SV.
2683
2684 SvROK_off (SV* sv)
2685
2686=item SvROK_on
2687
2688Tells an SV that it is an RV.
2689
2690 SvROK_on (SV* sv)
2691
2692=item SvRV
2693
2694Dereferences an RV to return the SV.
2695
2696 SV* SvRV (SV* sv);
2697
2698=item sv_setiv
2699
2700Copies an integer into the given SV.
2701
2702 void sv_setiv _((SV* sv, IV num));
2703
2704=item sv_setnv
2705
2706Copies a double into the given SV.
2707
2708 void sv_setnv _((SV* sv, double num));
2709
2710=item sv_setpv
2711
2712Copies a string into an SV. The string must be null-terminated.
2713
2714 void sv_setpv _((SV* sv, char* ptr));
2715
2716=item sv_setpvn
2717
2718Copies a string into an SV. The C<len> parameter indicates the number of
2719bytes to be copied.
2720
2721 void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
2722
46fc3d4c
PP
2723=item sv_setpvf
2724
2725Processes its arguments like C<sprintf> and sets an SV to the formatted
2726output.
2727
2728 void sv_setpvf _((SV* sv, const char* pat, ...));
2729
cb1a09d0
AD
2730=item sv_setref_iv
2731
5fb8527f
PP
2732Copies an integer into a new SV, optionally blessing the SV. The C<rv>
2733argument will be upgraded to an RV. That RV will be modified to point to
2734the new SV. The C<classname> argument indicates the package for the
2735blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2736will be returned and will have a reference count of 1.
cb1a09d0
AD
2737
2738 SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
2739
2740=item sv_setref_nv
2741
5fb8527f
PP
2742Copies a double into a new SV, optionally blessing the SV. The C<rv>
2743argument will be upgraded to an RV. That RV will be modified to point to
2744the new SV. The C<classname> argument indicates the package for the
2745blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2746will be returned and will have a reference count of 1.
cb1a09d0
AD
2747
2748 SV* sv_setref_nv _((SV *rv, char *classname, double nv));
2749
2750=item sv_setref_pv
2751
5fb8527f
PP
2752Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
2753argument will be upgraded to an RV. That RV will be modified to point to
2754the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
2755into the SV. The C<classname> argument indicates the package for the
2756blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
5f05dabc 2757will be returned and will have a reference count of 1.
cb1a09d0
AD
2758
2759 SV* sv_setref_pv _((SV *rv, char *classname, void* pv));
2760
2761Do not use with integral Perl types such as HV, AV, SV, CV, because those
2762objects will become corrupted by the pointer copy process.
2763
2764Note that C<sv_setref_pvn> copies the string while this copies the pointer.
2765
2766=item sv_setref_pvn
2767
5fb8527f
PP
2768Copies a string into a new SV, optionally blessing the SV. The length of the
2769string must be specified with C<n>. The C<rv> argument will be upgraded to
2770an RV. That RV will be modified to point to the new SV. The C<classname>
cb1a09d0
AD
2771argument indicates the package for the blessing. Set C<classname> to
2772C<Nullch> to avoid the blessing. The new SV will be returned and will have
5f05dabc 2773a reference count of 1.
cb1a09d0
AD
2774
2775 SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
2776
2777Note that C<sv_setref_pv> copies the pointer while this copies the string.
2778
2779=item sv_setsv
2780
2781Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
5f05dabc 2782The source SV may be destroyed if it is mortal.
cb1a09d0
AD
2783
2784 void sv_setsv _((SV* dsv, SV* ssv));
2785
2786=item SvSTASH
2787
2788Returns the stash of the SV.
2789
2790 HV * SvSTASH (SV* sv)
2791
2792=item SVt_IV
2793
2794Integer type flag for scalars. See C<svtype>.
2795
2796=item SVt_PV
2797
2798Pointer type flag for scalars. See C<svtype>.
2799
2800=item SVt_PVAV
2801
2802Type flag for arrays. See C<svtype>.
2803
2804=item SVt_PVCV
2805
2806Type flag for code refs. See C<svtype>.
2807
2808=item SVt_PVHV
2809
2810Type flag for hashes. See C<svtype>.
2811
2812=item SVt_PVMG
2813
2814Type flag for blessed scalars. See C<svtype>.
2815
2816=item SVt_NV
2817
2818Double type flag for scalars. See C<svtype>.
2819
2820=item SvTRUE
2821
2822Returns a boolean indicating whether Perl would evaluate the SV as true or
2823false, defined or undefined.
2824
2825 int SvTRUE (SV* sv)
2826
2827=item SvTYPE
2828
2829Returns the type of the SV. See C<svtype>.
2830
2831 svtype SvTYPE (SV* sv)
2832
2833=item svtype
2834
2835An enum of flags for Perl types. These are found in the file B<sv.h> in the
2836C<svtype> enum. Test these flags with the C<SvTYPE> macro.
2837
2838=item SvUPGRADE
2839
5fb8527f
PP
2840Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
2841the upgrade if necessary. See C<svtype>.
2842
2843 bool SvUPGRADE _((SV* sv, svtype mt));
2844
2845=item sv_upgrade
2846
2847Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
cb1a09d0
AD
2848
2849=item sv_undef
2850
2851This is the C<undef> SV. Always refer to this as C<&sv_undef>.
2852
5fb8527f
PP
2853=item sv_unref
2854
07fa94a1
JO
2855Unsets the RV status of the SV, and decrements the reference count of
2856whatever was being referenced by the RV. This can almost be thought of
2857as a reversal of C<newSVrv>. See C<SvROK_off>.
5fb8527f
PP
2858
2859 void sv_unref _((SV* sv));
2860
cb1a09d0
AD
2861=item sv_usepvn
2862
2863Tells an SV to use C<ptr> to find its string value. Normally the string is
5fb8527f
PP
2864stored inside the SV but sv_usepvn allows the SV to use an outside string.
2865The C<ptr> should point to memory that was allocated by C<malloc>. The
cb1a09d0
AD
2866string length, C<len>, must be supplied. This function will realloc the
2867memory pointed to by C<ptr>, so that pointer should not be freed or used by
2868the programmer after giving it to sv_usepvn.
2869
2870 void sv_usepvn _((SV* sv, char* ptr, STRLEN len));
2871
2872=item sv_yes
2873
2874This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
2875
2876=item THIS
2877
2878Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
2879This is always the proper type for the C++ object. See C<CLASS> and
5fb8527f 2880L<perlxs/"Using XS With C++">.
cb1a09d0
AD
2881
2882=item toLOWER
2883
2884Converts the specified character to lowercase.
2885
2886 int toLOWER (char c)
2887
2888=item toUPPER
2889
2890Converts the specified character to uppercase.
2891
2892 int toUPPER (char c)
2893
2894=item warn
2895
2896This is the XSUB-writer's interface to Perl's C<warn> function. Use this
2897function the same way you use the C C<printf> function. See C<croak()>.
2898
2899=item XPUSHi
2900
2901Push an integer onto the stack, extending the stack if necessary. See
2902C<PUSHi>.
2903
2904 XPUSHi(int d)
2905
2906=item XPUSHn
2907
2908Push a double onto the stack, extending the stack if necessary. See
2909C<PUSHn>.
2910
2911 XPUSHn(double d)
2912
2913=item XPUSHp
2914
2915Push a string onto the stack, extending the stack if necessary. The C<len>
2916indicates the length of the string. See C<PUSHp>.
2917
2918 XPUSHp(char *c, int len)
2919
2920=item XPUSHs
2921
2922Push an SV onto the stack, extending the stack if necessary. See C<PUSHs>.
2923
2924 XPUSHs(sv)
2925
5fb8527f
PP
2926=item XS
2927
2928Macro to declare an XSUB and its C parameter list. This is handled by
2929C<xsubpp>.
2930
cb1a09d0
AD
2931=item XSRETURN
2932
2933Return from XSUB, indicating number of items on the stack. This is usually
2934handled by C<xsubpp>.
2935
5fb8527f 2936 XSRETURN(int x);
cb1a09d0
AD
2937
2938=item XSRETURN_EMPTY
2939
5fb8527f 2940Return an empty list from an XSUB immediately.
cb1a09d0
AD
2941
2942 XSRETURN_EMPTY;
2943
5fb8527f
PP
2944=item XSRETURN_IV
2945
2946Return an integer from an XSUB immediately. Uses C<XST_mIV>.
2947
2948 XSRETURN_IV(IV v);
2949
cb1a09d0
AD
2950=item XSRETURN_NO
2951
5fb8527f 2952Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
cb1a09d0
AD
2953
2954 XSRETURN_NO;
2955
5fb8527f
PP
2956=item XSRETURN_NV
2957
2958Return an double from an XSUB immediately. Uses C<XST_mNV>.
2959
2960 XSRETURN_NV(NV v);
2961
2962=item XSRETURN_PV
2963
2964Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
2965
2966 XSRETURN_PV(char *v);
2967
cb1a09d0
AD
2968=item XSRETURN_UNDEF
2969
5fb8527f 2970Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
cb1a09d0
AD
2971
2972 XSRETURN_UNDEF;
2973
2974=item XSRETURN_YES
2975
5fb8527f 2976Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
cb1a09d0
AD
2977
2978 XSRETURN_YES;
2979
5fb8527f
PP
2980=item XST_mIV
2981
2982Place an integer into the specified position C<i> on the stack. The value is
2983stored in a new mortal SV.
2984
2985 XST_mIV( int i, IV v );
2986
2987=item XST_mNV
2988
2989Place a double into the specified position C<i> on the stack. The value is
2990stored in a new mortal SV.
2991
2992 XST_mNV( int i, NV v );
2993
2994=item XST_mNO
2995
2996Place C<&sv_no> into the specified position C<i> on the stack.
2997
2998 XST_mNO( int i );
2999
3000=item XST_mPV
3001
3002Place a copy of a string into the specified position C<i> on the stack. The
3003value is stored in a new mortal SV.
3004
3005 XST_mPV( int i, char *v );
3006
3007=item XST_mUNDEF
3008
3009Place C<&sv_undef> into the specified position C<i> on the stack.
3010
3011 XST_mUNDEF( int i );
3012
3013=item XST_mYES
3014
3015Place C<&sv_yes> into the specified position C<i> on the stack.
3016
3017 XST_mYES( int i );
3018
3019=item XS_VERSION
3020
3021The version identifier for an XS module. This is usually handled
3022automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
3023
3024=item XS_VERSION_BOOTCHECK
3025
3026Macro to verify that a PM module's $VERSION variable matches the XS module's
3027C<XS_VERSION> variable. This is usually handled automatically by
3028C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
3029
cb1a09d0
AD
3030=item Zero
3031
3032The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
3033destination, C<n> is the number of items, and C<t> is the type.
3034
3035 (void) Zero( d, n, t );
3036
3037=back
3038
5f05dabc 3039=head1 EDITOR
cb1a09d0 3040
9607fc9c 3041Jeff Okamoto <F<okamoto@corp.hp.com>>
cb1a09d0
AD
3042
3043With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
3044Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
55497cff 3045Bowers, Matthew Green, Tim Bunce, Spider Boardman, and Ulrich Pfeifer.
cb1a09d0 3046
9607fc9c 3047API Listing by Dean Roehrich <F<roehrich@cray.com>>.
cb1a09d0
AD
3048
3049=head1 DATE
3050
04343c6d 3051Version 31.8: 1997/5/17