3 perlguts - Perl's Internal Functions
7 This document attempts to describe some of the internal functions of the
8 Perl executable. It is far from complete and probably contains many errors.
9 Please refer any questions or comments to the author below.
13 Perl has three typedefs that handle Perl's three main data types:
19 Each typedef has specific routines that manipulate the various data types.
21 =head2 What is an "IV"?
23 Perl uses a special typedef IV which is large enough to hold either an
26 Perl also uses two special typedefs, I32 and I16, which will always be at
27 least 32-bits and 16-bits long, respectively.
29 =head2 Working with SV's
31 An SV can be created and loaded with one command. There are four types of
32 values that can be loaded: an integer value (IV), a double (NV), a string,
33 (PV), and another scalar (SV).
35 The four routines are:
39 SV* newSVpv(char*, int);
42 To change the value of an I<already-existing> SV, there are five routines:
44 void sv_setiv(SV*, IV);
45 void sv_setnv(SV*, double);
46 void sv_setpvn(SV*, char*, int)
47 void sv_setpv(SV*, char*);
48 void sv_setsv(SV*, SV*);
50 Notice that you can choose to specify the length of the string to be
51 assigned by using C<sv_setpvn> or C<newSVpv>, or you may allow Perl to
52 calculate the length by using C<sv_setpv> or by specifying 0 as the second
53 argument to C<newSVpv>. Be warned, though, that Perl will determine the
54 string's length by using C<strlen>, which depends on the string terminating
57 To access the actual value that an SV points to, you can use the macros:
63 which will automatically coerce the actual scalar type into an IV, double,
66 In the C<SvPV> macro, the length of the string returned is placed into the
67 variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
68 care what the length of the data is, use the global variable C<na>. Remember,
69 however, that Perl allows arbitrary strings of data that may both contain
70 NUL's and not be terminated by a NUL.
72 If you simply want to know if the scalar value is TRUE, you can use:
76 Although Perl will automatically grow strings for you, if you need to force
77 Perl to allocate more memory for your SV, you can use the macro
79 SvGROW(SV*, STRLEN newlen)
81 which will determine if more memory needs to be allocated. If so, it will
82 call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
83 decrease, the allocated memory of an SV.
85 If you have an SV and want to know what kind of data Perl thinks is stored
86 in it, you can use the following macros to check the type of SV you have.
92 You can get and set the current length of the string stored in an SV with
96 SvCUR_set(SV*, I32 val)
98 You can also get a pointer to the end of the string stored in the SV
103 But note that these last three macros are valid only if C<SvPOK()> is true.
105 If you want to append something to the end of string stored in an C<SV*>,
106 you can use the following functions:
108 void sv_catpv(SV*, char*);
109 void sv_catpvn(SV*, char*, int);
110 void sv_catsv(SV*, SV*);
112 The first function calculates the length of the string to be appended by
113 using C<strlen>. In the second, you specify the length of the string
114 yourself. The third function extends the string stored in the first SV
115 with the string stored in the second SV. It also forces the second SV to
116 be interpreted as a string.
118 If you know the name of a scalar variable, you can get a pointer to its SV
119 by using the following:
121 SV* perl_get_sv("varname", FALSE);
123 This returns NULL if the variable does not exist.
125 If you want to know if this variable (or any other SV) is actually C<defined>,
130 The scalar C<undef> value is stored in an SV instance called C<sv_undef>. Its
131 address can be used whenever an C<SV*> is needed.
133 There are also the two values C<sv_yes> and C<sv_no>, which contain Boolean
134 TRUE and FALSE values, respectively. Like C<sv_undef>, their addresses can
135 be used whenever an C<SV*> is needed.
137 Do not be fooled into thinking that C<(SV *) 0> is the same as C<&sv_undef>.
141 if (I-am-to-return-a-real-value) {
142 sv = sv_2mortal(newSViv(42));
146 This code tries to return a new SV (which contains the value 42) if it should
147 return a real value, or undef otherwise. Instead it has returned a null
148 pointer which, somewhere down the line, will cause a segmentation violation,
149 or just weird results. Change the zero to C<&sv_undef> in the first line and
152 To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
153 call is not necessary. See the section on B<MORTALITY>.
155 =head2 What's Really Stored in an SV?
157 Recall that the usual method of determining the type of scalar you have is
158 to use C<Sv*OK> macros. Since a scalar can be both a number and a string,
159 usually these macros will always return TRUE and calling the C<Sv*V>
160 macros will do the appropriate conversion of string to integer/double or
161 integer/double to string.
163 If you I<really> need to know if you have an integer, double, or string
164 pointer in an SV, you can use the following three macros instead:
170 These will tell you if you truly have an integer, double, or string pointer
171 stored in your SV. The "p" stands for private.
173 In general, though, it's best to just use the C<Sv*V> macros.
175 =head2 Working with AV's
177 There are two ways to create and load an AV. The first method just creates
182 The second method both creates the AV and initially populates it with SV's:
184 AV* av_make(I32 num, SV **ptr);
186 The second argument points to an array containing C<num> C<SV*>'s. Once the
187 AV has been created, the SV's can be destroyed, if so desired.
189 Once the AV has been created, the following operations are possible on AV's:
191 void av_push(AV*, SV*);
194 void av_unshift(AV*, I32 num);
196 These should be familiar operations, with the exception of C<av_unshift>.
197 This routine adds C<num> elements at the front of the array with the C<undef>
198 value. You must then use C<av_store> (described below) to assign values
199 to these new elements.
201 Here are some other functions:
203 I32 av_len(AV*); /* Returns highest index value in array */
205 SV** av_fetch(AV*, I32 key, I32 lval);
206 /* Fetches value at key offset, but it stores an undef value
207 at the offset if lval is non-zero */
208 SV** av_store(AV*, I32 key, SV* val);
209 /* Stores val at offset key */
211 Take note that C<av_fetch> and C<av_store> return C<SV**>'s, not C<SV*>'s.
214 /* Clear out all elements, but leave the array */
216 /* Undefines the array, removing all elements */
217 void av_extend(AV*, I32 key);
218 /* Extend the array to a total of key elements */
220 If you know the name of an array variable, you can get a pointer to its AV
221 by using the following:
223 AV* perl_get_av("varname", FALSE);
225 This returns NULL if the variable does not exist.
227 =head2 Working with HV's
229 To create an HV, you use the following routine:
233 Once the HV has been created, the following operations are possible on HV's:
235 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
236 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
238 The C<klen> parameter is the length of the key being passed in. The C<val>
239 argument contains the SV pointer to the scalar being stored, and C<hash> is
240 the pre-computed hash value (zero if you want C<hv_store> to calculate it
241 for you). The C<lval> parameter indicates whether this fetch is actually a
242 part of a store operation.
244 Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
245 C<SV*>. In order to access the scalar value, you must first dereference
246 the return value. However, you should check to make sure that the return
247 value is not NULL before dereferencing it.
249 These two functions check if a hash table entry exists, and deletes it.
251 bool hv_exists(HV*, char* key, U32 klen);
252 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
254 And more miscellaneous functions:
257 /* Clears all entries in hash table */
259 /* Undefines the hash table */
261 Perl keeps the actual data in linked list of structures with a typedef of HE.
262 These contain the actual key and value pointers (plus extra administrative
263 overhead). The key is a string pointer; the value is an C<SV*>. However,
264 once you have an C<HE*>, to get the actual key and value, use the routines
267 I32 hv_iterinit(HV*);
268 /* Prepares starting point to traverse hash table */
269 HE* hv_iternext(HV*);
270 /* Get the next entry, and return a pointer to a
271 structure that has both the key and value */
272 char* hv_iterkey(HE* entry, I32* retlen);
273 /* Get the key from an HE structure and also return
274 the length of the key string */
275 SV* hv_iterval(HV*, HE* entry);
276 /* Return a SV pointer to the value of the HE
278 SV* hv_iternextsv(HV*, char** key, I32* retlen);
279 /* This convenience routine combines hv_iternext,
280 hv_iterkey, and hv_iterval. The key and retlen
281 arguments are return values for the key and its
282 length. The value is returned in the SV* argument */
284 If you know the name of a hash variable, you can get a pointer to its HV
285 by using the following:
287 HV* perl_get_hv("varname", FALSE);
289 This returns NULL if the variable does not exist.
291 The hash algorithm, for those who are interested, is:
297 hash = hash * 33 + *s++;
301 References are a special type of scalar that point to other data types
302 (including references).
304 To create a reference, use the following command:
306 SV* newRV((SV*) thing);
308 The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. Once
309 you have a reference, you can use the following macro to dereference the
314 then call the appropriate routines, casting the returned C<SV*> to either an
315 C<AV*> or C<HV*>, if required.
317 To determine if an SV is a reference, you can use the following macro:
321 To actually discover what the reference refers to, you must use the following
322 macro and then check the value returned.
326 The most useful types that will be returned are:
334 SVt_PVMG Blessed Scalar
336 =head2 Blessed References and Class Objects
338 References are also used to support object-oriented programming. In the
339 OO lexicon, an object is simply a reference that has been blessed into a
340 package (or class). Once blessed, the programmer may now use the reference
341 to access the various methods in the class.
343 A reference can be blessed into a package with the following function:
345 SV* sv_bless(SV* sv, HV* stash);
347 The C<sv> argument must be a reference. The C<stash> argument specifies
348 which class the reference will belong to. See the section on L<Stashes>
349 for information on converting class names into stashes.
351 /* Still under construction */
353 Upgrades rv to reference if not already one. Creates new SV for rv to
355 If classname is non-null, the SV is blessed into the specified class.
358 SV* newSVrv(SV* rv, char* classname);
360 Copies integer or double into an SV whose reference is rv. SV is blessed
361 if classname is non-null.
363 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
364 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
366 Copies pointer (I<not a string!>) into an SV whose reference is rv.
367 SV is blessed if classname is non-null.
369 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
371 Copies string into an SV whose reference is rv.
372 Set length to 0 to let Perl calculate the string length.
373 SV is blessed if classname is non-null.
375 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
377 int sv_isa(SV* sv, char* name);
378 int sv_isobject(SV* sv);
380 =head1 Creating New Variables
382 To create a new Perl variable, which can be accessed from your Perl script,
383 use the following routines, depending on the variable type.
385 SV* perl_get_sv("varname", TRUE);
386 AV* perl_get_av("varname", TRUE);
387 HV* perl_get_hv("varname", TRUE);
389 Notice the use of TRUE as the second parameter. The new variable can now
390 be set, using the routines appropriate to the data type.
392 There are additional bits that may be OR'ed with the TRUE argument to enable
393 certain extra features. Those bits are:
395 0x02 Marks the variable as multiply defined, thus preventing the
396 "Indentifier <varname> used only once: possible typo" warning.
397 0x04 Issues a "Had to create <varname> unexpectedly" warning if
398 the variable didn't actually exist. This is useful if
399 you expected the variable to already exist and want to propagate
400 this warning back to the user.
402 If the C<varname> argument does not contain a package specifier, it is
403 created in the current package.
405 =head1 XSUB's and the Argument Stack
407 The XSUB mechanism is a simple way for Perl programs to access C subroutines.
408 An XSUB routine will have a stack that contains the arguments from the Perl
409 program, and a way to map from the Perl data structures to a C equivalent.
411 The stack arguments are accessible through the C<ST(n)> macro, which returns
412 the C<n>'th stack argument. Argument 0 is the first argument passed in the
413 Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
416 Most of the time, output from the C routine can be handled through use of
417 the RETVAL and OUTPUT directives. However, there are some cases where the
418 argument stack is not already long enough to handle all the return values.
419 An example is the POSIX tzname() call, which takes no arguments, but returns
420 two, the local timezone's standard and summer time abbreviations.
422 To handle this situation, the PPCODE directive is used and the stack is
423 extended using the macro:
427 where C<sp> is the stack pointer, and C<num> is the number of elements the
428 stack should be extended by.
430 Now that there is room on the stack, values can be pushed on it using the
431 macros to push IV's, doubles, strings, and SV pointers respectively:
438 And now the Perl program calling C<tzname>, the two values will be assigned
441 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
443 An alternate (and possibly simpler) method to pushing values on the stack is
451 These macros automatically adjust the stack for you, if needed.
453 For more information, consult L<perlxs>.
457 In Perl, values are normally "immortal" -- that is, they are not freed unless
458 explicitly done so (via the Perl C<undef> call or other routines in Perl
461 Add cruft about reference counts.
462 int SvREFCNT(SV* sv);
463 void SvREFCNT_inc(SV* sv);
464 void SvREFCNT_dec(SV* sv);
466 In the above example with C<tzname>, we needed to create two new SV's to push
467 onto the argument stack, that being the two strings. However, we don't want
468 these new SV's to stick around forever because they will eventually be
469 copied into the SV's that hold the two scalar variables.
471 An SV (or AV or HV) that is "mortal" acts in all ways as a normal "immortal"
472 SV, AV, or HV, but is only valid in the "current context". When the Perl
473 interpreter leaves the current context, the mortal SV, AV, or HV is
474 automatically freed. Generally the "current context" means a single
477 To create a mortal variable, use the functions:
481 SV* sv_mortalcopy(SV*)
483 The first call creates a mortal SV, the second converts an existing SV to
484 a mortal SV, the third creates a mortal copy of an existing SV.
486 The mortal routines are not just for SV's -- AV's and HV's can be made mortal
487 by passing their address (and casting them to C<SV*>) to the C<sv_2mortal> or
488 C<sv_mortalcopy> routines.
491 Beware that the sv_2mortal() call is eventually equivalent to
492 svREFCNT_dec(). A value can happily be mortal in two different contexts,
493 and it will be svREFCNT_dec()ed twice, once on exit from these
494 contexts. It can also be mortal twice in the same context. This means
495 that you should be very careful to make a value mortal exactly as many
496 times as it is needed. The value that go to the Perl stack I<should>
499 You should be careful about creating mortal variables. It is possible for
500 strange things to happen should you make the same value mortal within
505 A stash is a hash table (associative array) that contains all of the
506 different objects that are contained within a package. Each key of the
507 stash is a symbol name (shared by all the different types of objects
508 that have the same name), and each value in the hash table is called a
509 GV (for Glob Value). This GV in turn contains references to the various
510 objects of that name, including (but not limited to) the following:
520 Perl stores various stashes in a separate GV structure (for global
521 variable) but represents them with an HV structure. The keys in this
522 larger GV are the various package names; the values are the C<GV*>'s
523 which are stashes. It may help to think of a stash purely as an HV,
524 and that the term "GV" means the global variable hash.
526 To get the stash pointer for a particular package, use the function:
528 HV* gv_stashpv(char* name, I32 create)
529 HV* gv_stashsv(SV*, I32 create)
531 The first function takes a literal string, the second uses the string stored
532 in the SV. Remember that a stash is just a hash table, so you get back an
533 C<HV*>. The C<create> flag will create a new package if it is set.
535 The name that C<gv_stash*v> wants is the name of the package whose symbol table
536 you want. The default package is called C<main>. If you have multiply nested
537 packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
540 Alternately, if you have an SV that is a blessed reference, you can find
541 out the stash pointer by using:
543 HV* SvSTASH(SvRV(SV*));
545 then use the following to get the package name itself:
547 char* HvNAME(HV* stash);
549 If you need to return a blessed value to your Perl script, you can use the
552 SV* sv_bless(SV*, HV* stash)
554 where the first argument, an C<SV*>, must be a reference, and the second
555 argument is a stash. The returned C<SV*> can now be used in the same way
558 For more information on references and blessings, consult L<perlref>.
562 [This section still under construction. Ignore everything here. Post no
563 bills. Everything not permitted is forbidden.]
565 # Version 6, 1995/1/27
567 Any SV may be magical, that is, it has special features that a normal
568 SV does not have. These features are stored in the SV structure in a
569 linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
582 Note this is current as of patchlevel 0, and could change at any time.
584 =head2 Assigning Magic
586 Perl adds magic to an SV using the sv_magic function:
588 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
590 The C<sv> argument is a pointer to the SV that is to acquire a new magical
593 If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
594 set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
595 it to the beginning of the linked list of magical features. Any prior
596 entry of the same type of magic is deleted. Note that this can be
597 overriden, and multiple instances of the same type of magic can be
598 associated with an SV.
600 The C<name> and C<namlem> arguments are used to associate a string with
601 the magic, typically the name of a variable. C<namlem> is stored in the
602 C<mg_len> field and if C<name> is non-null and C<namlem> >= 0 a malloc'd
603 copy of the name is stored in C<mg_ptr> field.
605 The sv_magic function uses C<how> to determine which, if any, predefined
606 "Magic Virtual Table" should be assigned to the C<mg_virtual> field.
607 See the "Magic Virtual Table" section below. The C<how> argument is also
608 stored in the C<mg_type> field.
610 The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
611 structure. If it is not the same as the C<sv> argument, the reference
612 count of the C<obj> object is incremented. If it is the same, or if
613 the C<how> argument is "#", or if it is a null pointer, then C<obj> is
614 merely stored, without the reference count being incremented.
616 There is also a function to add magic to an C<HV>:
618 void hv_magic(HV *hv, GV *gv, int how);
620 This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
622 To remove the magic from an SV, call the function sv_unmagic:
624 void sv_unmagic(SV *sv, int type);
626 The C<type> argument should be equal to the C<how> value when the C<SV>
627 was initially made magical.
629 =head2 Magic Virtual Tables
631 The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
632 C<MGVTBL>, which is a structure of function pointers and stands for
633 "Magic Virtual Table" to handle the various operations that might be
634 applied to that variable.
636 The C<MGVTBL> has five pointers to the following routine types:
638 int (*svt_get)(SV* sv, MAGIC* mg);
639 int (*svt_set)(SV* sv, MAGIC* mg);
640 U32 (*svt_len)(SV* sv, MAGIC* mg);
641 int (*svt_clear)(SV* sv, MAGIC* mg);
642 int (*svt_free)(SV* sv, MAGIC* mg);
644 This MGVTBL structure is set at compile-time in C<perl.h> and there are
645 currently 19 types (or 21 with overloading turned on). These different
646 structures contain pointers to various routines that perform additional
647 actions depending on which function is being called.
649 Function pointer Action taken
650 ---------------- ------------
651 svt_get Do something after the value of the SV is retrieved.
652 svt_set Do something after the SV is assigned a value.
653 svt_len Report on the SV's length.
654 svt_clear Clear something the SV represents.
655 svt_free Free any extra storage associated with the SV.
657 For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
658 to an C<mg_type> of '\0') contains:
660 { magic_get, magic_set, magic_len, 0, 0 }
662 Thus, when an SV is determined to be magical and of type '\0', if a get
663 operation is being performed, the routine C<magic_get> is called. All
664 the various routines for the various magical types begin with C<magic_>.
666 The current kinds of Magic Virtual Tables are:
668 mg_type MGVTBL Type of magicalness
669 ------- ------ -------------------
671 A vtbl_amagic Operator Overloading
672 a vtbl_amagicelem Operator Overloading
673 c 0 Used in Operator Overloading
674 B vtbl_bm Boyer-Moore???
676 e vtbl_envelem %ENV hash element
677 g vtbl_mglob Regexp /g flag???
678 I vtbl_isa @ISA array
679 i vtbl_isaelem @ISA array element
680 L 0 (but sets RMAGICAL) Perl Module/Debugger???
681 l vtbl_dbline Debugger?
682 P vtbl_pack Tied Array or Hash
683 p vtbl_packelem Tied Array or Hash element
684 q vtbl_packelem Tied Scalar or Handle
685 S vtbl_sig Signal Hash
686 s vtbl_sigelem Signal Hash element
687 t vtbl_taint Taintedness
690 x vtbl_substr Substring???
692 # vtbl_arylen Array Length
693 . vtbl_pos $. scalar variable
694 ~ Reserved for extensions, but multiple extensions may clash
696 When an upper-case and lower-case letter both exist in the table, then the
697 upper-case letter is used to represent some kind of composite type (a list
698 or a hash), and the lower-case letter is used to represent an element of
703 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
705 This routine returns a pointer to the C<MAGIC> structure stored in the SV.
706 If the SV does not have that magical feature, C<NULL> is returned. Also,
707 if the SV is not of type SVt_PVMG, Perl may core-dump.
709 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
711 This routine checks to see what types of magic C<sv> has. If the mg_type
712 field is an upper-case letter, then the mg_obj is copied to C<nsv>, but
713 the mg_type field is changed to be the lower-case letter.
715 =head1 Double-Typed SV's
717 Scalar variables normally contain only one type of value, an integer,
718 double, pointer, or reference. Perl will automatically convert the
719 actual scalar data from the stored type into the requested type.
721 Some scalar variables contain more than one type of scalar data. For
722 example, the variable C<$!> contains either the numeric value of C<errno>
723 or its string equivalent from either C<strerror> or C<sys_errlist[]>.
725 To force multiple data values into an SV, you must do two things: use the
726 C<sv_set*v> routines to add the additional scalar type, then set a flag
727 so that Perl will believe it contains more than one type of data. The
728 four macros to set the flags are:
735 The particular macro you must use depends on which C<sv_set*v> routine
736 you called first. This is because every C<sv_set*v> routine turns on
737 only the bit for the particular type of data being set, and turns off
740 For example, to create a new Perl variable called "dberror" that contains
741 both the numeric and descriptive string error values, you could use the
745 extern char *dberror_list;
747 SV* sv = perl_get_sv("dberror", TRUE);
748 sv_setiv(sv, (IV) dberror);
749 sv_setpv(sv, dberror_list[dberror]);
752 If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
753 macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
755 =head1 Calling Perl Routines from within C Programs
757 There are four routines that can be used to call a Perl subroutine from
758 within a C program. These four are:
760 I32 perl_call_sv(SV*, I32);
761 I32 perl_call_pv(char*, I32);
762 I32 perl_call_method(char*, I32);
763 I32 perl_call_argv(char*, I32, register char**);
765 The routine most often used is C<perl_call_sv>. The C<SV*> argument
766 contains either the name of the Perl subroutine to be called, or a
767 reference to the subroutine. The second argument consists of flags
768 that control the context in which the subroutine is called, whether
769 or not the subroutine is being passed arguments, how errors should be
770 trapped, and how to treat return values.
772 All four routines return the number of arguments that the subroutine returned
775 When using any of these routines (except C<perl_call_argv>), the programmer
776 must manipulate the Perl stack. These include the following macros and
790 For more information, consult L<perlcall>.
792 =head1 Memory Allocation
794 It is strongly suggested that you use the version of malloc that is distributed
795 with Perl. It keeps pools of various sizes of unallocated memory in order to
796 more quickly satisfy allocation requests.
797 However, on some platforms, it may cause spurious malloc or free errors.
799 New(x, pointer, number, type);
800 Newc(x, pointer, number, type, cast);
801 Newz(x, pointer, number, type);
803 These three macros are used to initially allocate memory. The first argument
804 C<x> was a "magic cookie" that was used to keep track of who called the macro,
805 to help when debugging memory problems. However, the current code makes no
806 use of this feature (Larry has switched to using a run-time memory checker),
807 so this argument can be any number.
809 The second argument C<pointer> will point to the newly allocated memory.
810 The third and fourth arguments C<number> and C<type> specify how many of
811 the specified type of data structure should be allocated. The argument
812 C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
813 should be used if the C<pointer> argument is different from the C<type>
816 Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
817 to zero out all the newly allocated memory.
819 Renew(pointer, number, type);
820 Renewc(pointer, number, type, cast);
823 These three macros are used to change a memory buffer size or to free a
824 piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
825 match those of C<New> and C<Newc> with the exception of not needing the
826 "magic cookie" argument.
828 Move(source, dest, number, type);
829 Copy(source, dest, number, type);
830 Zero(dest, number, type);
832 These three macros are used to move, copy, or zero out previously allocated
833 memory. The C<source> and C<dest> arguments point to the source and
834 destination starting points. Perl will move, copy, or zero out C<number>
835 instances of the size of the C<type> data structure (using the C<sizeof>
840 This is a listing of functions, macros, flags, and variables that may be
841 useful to extension writers or that may be found while reading other
852 Clears an array, making it empty.
854 void av_clear _((AV* ar));
858 Pre-extend an array. The C<key> is the index to which the array should be
861 void av_extend _((AV* ar, I32 key));
865 Returns the SV at the specified index in the array. The C<key> is the
866 index. If C<lval> is set then the fetch will be part of a store. Check
867 that the return value is non-null before dereferencing it to a C<SV*>.
869 SV** av_fetch _((AV* ar, I32 key, I32 lval));
873 Returns the highest index in the array. Returns -1 if the array is empty.
875 I32 av_len _((AV* ar));
879 Creats a new AV and populates it with a list of SVs. The SVs are copied
880 into the array, so they may be freed after the call to av_make.
882 AV* av_make _((I32 size, SV** svp));
886 Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
889 SV* av_pop _((AV* ar));
893 Pushes an SV onto the end of the array.
895 void av_push _((AV* ar, SV* val));
899 Shifts an SV off the beginning of the array.
901 SV* av_shift _((AV* ar));
905 Stores an SV in an array. The array index is specified as C<key>. The
906 return value will be null if the operation failed, otherwise it can be
907 dereferenced to get the original C<SV*>.
909 SV** av_store _((AV* ar, I32 key, SV* val));
915 void av_undef _((AV* ar));
919 Unshift an SV onto the beginning of the array.
921 void av_unshift _((AV* ar, I32 num));
925 Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
926 constructor. This is always a C<char*>. See C<THIS> and L<perlxs>.
930 The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
931 source, C<d> is the destination, C<n> is the number of items, and C<t> is
934 (void) Copy( s, d, n, t );
938 This is the XSUB-writer's interface to Perl's C<die> function. Use this
939 function the same way you use the C C<printf> function. See C<warn>.
943 Returns the stash of the CV.
945 HV * CvSTASH( SV* sv )
949 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
950 boolean which indicates whether subs are being single-stepped.
951 Single-stepping is automatically turned on after every step. See C<DBsub>.
955 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
956 the SV which holds the name of the sub being debugged. See C<DBsingle>.
957 The sub name can be found by
959 SvPV( GvSV( DBsub ), na )
963 Declare a stack marker for the XSUB. See C<MARK> and C<dORIGMARK>.
967 Saves the original stack mark for the XSUB. See C<ORIGMARK>.
971 Declares a stack pointer for the XSUB. See C<SP>.
975 Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
976 usually handled automatically by C<xsubpp>. Declares the C<items> variable
977 to indicate the number of items on the stack.
981 Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
987 Used to extend the argument stack for an XSUB's return values.
993 Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1000 Used to indicate array context. See C<GIMME> and L<perlcall>.
1004 Indicates that arguments returned from a callback should be discarded. See
1009 Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1013 The XSUB-writer's equivalent to Perl's C<wantarray>. Returns C<G_SCALAR> or
1014 C<G_ARRAY> for scalar or array context.
1018 Indicates that no arguments are being sent to a callback. See L<perlcall>.
1022 Used to indicate scalar context. See C<GIMME> and L<perlcall>.
1026 Returns a pointer to the stash for a specified package. If C<create> is set
1027 then the package will be created if it does not already exist. If C<create>
1028 is not set and the package does not exist then NULL is returned.
1030 HV* gv_stashpv _((char* name, I32 create));
1034 Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1036 HV* gv_stashsv _((SV* sv, I32 create));
1040 Return the SV from the GV.
1044 Releases a hash entry from an iterator. See C<hv_iternext>.
1048 Clears a hash, making it empty.
1050 void hv_clear _((HV* tb));
1054 Deletes a key/value pair in the hash. The value SV is removed from the hash
1055 and returned to the caller. The C<lken> is the length of the key. The
1056 C<flags> value will normally be zero; if set to G_DISCARD then null will be
1059 SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));
1063 Returns a boolean indicating whether the specified hash key exists. The
1064 C<lken> is the length of the key.
1066 bool hv_exists _((HV* tb, char* key, U32 klen));
1070 Returns the SV which corresponds to the specified key in the hash. The
1071 C<lken> is the length of the key. If C<lval> is set then the fetch will be
1072 part of a store. Check that the return value is non-null before
1073 dereferencing it to a C<SV*>.
1075 SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));
1079 Prepares a starting point to traverse a hash table.
1081 I32 hv_iterinit _((HV* tb));
1085 Returns the key from the current position of the hash iterator. See
1088 char* hv_iterkey _((HE* entry, I32* retlen));
1092 Returns entries from a hash iterator. See C<hv_iterinit>.
1094 HE* hv_iternext _((HV* tb));
1098 Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1101 SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));
1105 Returns the value from the current position of the hash iterator. See
1108 SV* hv_iterval _((HV* tb, HE* entry));
1112 Adds magic to a hash. See C<sv_magic>.
1114 void hv_magic _((HV* hv, GV* gv, int how));
1118 Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1120 char *HvNAME (HV* stash)
1124 Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
1125 the length of the key. The C<hash> parameter is the pre-computed hash
1126 value; if it is zero then Perl will compute it. The return value will be
1127 null if the operation failed, otherwise it can be dereferenced to get the
1130 SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
1136 void hv_undef _((HV* tb));
1140 Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
1143 int isALNUM (char c)
1147 Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
1150 int isALPHA (char c)
1154 Returns a boolean indicating whether the C C<char> is an ascii digit.
1156 int isDIGIT (char c)
1160 Returns a boolean indicating whether the C C<char> is a lowercase character.
1162 int isLOWER (char c)
1166 Returns a boolean indicating whether the C C<char> is whitespace.
1168 int isSPACE (char c)
1172 Returns a boolean indicating whether the C C<char> is an uppercase character.
1174 int isUPPER (char c)
1178 Variable which is setup by C<xsubpp> to indicate the number of items on the
1179 stack. See L<perlxs>.
1183 Closing bracket on a callback. See C<ENTER> and L<perlcall>.
1189 Stack marker for the XSUB. See C<dMARK>.
1193 Clear something magical that the SV represents. See C<sv_magic>.
1195 int mg_clear _((SV* sv));
1199 Copies the magic from one SV to another. See C<sv_magic>.
1201 int mg_copy _((SV *, SV *, char *, STRLEN));
1205 Finds the magic pointer for type matching the SV. See C<sv_magic>.
1207 MAGIC* mg_find _((SV* sv, int type));
1211 Free any magic storage used by the SV. See C<sv_magic>.
1213 int mg_free _((SV* sv));
1217 Do magic after a value is retrieved from the SV. See C<sv_magic>.
1219 int mg_get _((SV* sv));
1223 Report on the SV's length. See C<sv_magic>.
1225 U32 mg_len _((SV* sv));
1229 Turns on the magical status of an SV. See C<sv_magic>.
1231 void mg_magical _((SV* sv));
1235 Do magic after a value is assigned to the SV. See C<sv_magic>.
1237 int mg_set _((SV* sv));
1241 The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
1242 source, C<d> is the destination, C<n> is the number of items, and C<t> is
1245 (void) Move( s, d, n, t );
1249 A variable which may be used with C<SvPV> to tell Perl to calculate the
1254 The XSUB-writer's interface to the C C<malloc> function.
1256 void * New( x, void *ptr, int size, type )
1260 The XSUB-writer's interface to the C C<malloc> function, with cast.
1262 void * Newc( x, void *ptr, int size, type, cast )
1266 The XSUB-writer's interface to the C C<malloc> function. The allocated
1267 memory is zeroed with C<memzero>.
1269 void * Newz( x, void *ptr, int size, type )
1273 Creates a new AV. The refcount is set to 1.
1275 AV* newAV _((void));
1279 Creates a new HV. The refcount is set to 1.
1281 HV* newHV _((void));
1285 Creates an RV wrapper for an SV. The refcount for the original SV is
1288 SV* newRV _((SV* ref));
1292 Creates a new SV. The C<len> parameter indicates the number of bytes of
1293 pre-allocated string space the SV should have. The refcount for the new SV
1296 SV* newSV _((STRLEN len));
1300 Creates a new SV and copies an integer into it. The refcount for the SV is
1303 SV* newSViv _((IV i));
1307 Creates a new SV and copies a double into it. The refcount for the SV is
1310 SV* newSVnv _((NV i));
1314 Creates a new SV and copies a string into it. The refcount for the SV is
1315 set to 1. If C<len> is zero then Perl will compute the length.
1317 SV* newSVpv _((char* s, STRLEN len));
1321 Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
1322 it will be upgraded one. If C<classname> is non-null then the new SV will
1323 be blessed in the specified package. The new SV is returned and its
1326 SV* newSVrv _((SV* rv, char* classname));
1330 Creates a new SV which is an exact duplicate of the orignal SV.
1332 SV* newSVsv _((SV* old));
1336 Used by C<xsubpp> to hook up XSUBs as Perl subs.
1340 Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
1349 Null character pointer.
1365 The original stack mark for the XSUB. See C<dORIGMARK>.
1369 Allocates a new Perl interpreter. See L<perlembed>.
1371 =item perl_call_argv
1373 Performs a callback to the specified Perl sub. See L<perlcall>.
1375 I32 perl_call_argv _((char* subname, I32 flags, char** argv));
1377 =item perl_call_method
1379 Performs a callback to the specified Perl method. The blessed object must
1380 be on the stack. See L<perlcall>.
1382 I32 perl_call_method _((char* methname, I32 flags));
1386 Performs a callback to the specified Perl sub. See L<perlcall>.
1388 I32 perl_call_pv _((char* subname, I32 flags));
1392 Performs a callback to the Perl sub whose name is in the SV. See
1395 I32 perl_call_sv _((SV* sv, I32 flags));
1397 =item perl_construct
1399 Initializes a new Perl interpreter. See L<perlembed>.
1403 Shuts down a Perl interpreter. See L<perlembed>.
1407 Tells Perl to C<eval> the string in the SV.
1409 I32 perl_eval_sv _((SV* sv, I32 flags));
1413 Releases a Perl interpreter. See L<perlembed>.
1417 Returns the AV of the specified Perl array. If C<create> is set and the
1418 Perl variable does not exist then it will be created. If C<create> is not
1419 set and the variable does not exist then null is returned.
1421 AV* perl_get_av _((char* name, I32 create));
1425 Returns the CV of the specified Perl sub. If C<create> is set and the Perl
1426 variable does not exist then it will be created. If C<create> is not
1427 set and the variable does not exist then null is returned.
1429 CV* perl_get_cv _((char* name, I32 create));
1433 Returns the HV of the specified Perl hash. If C<create> is set and the Perl
1434 variable does not exist then it will be created. If C<create> is not
1435 set and the variable does not exist then null is returned.
1437 HV* perl_get_hv _((char* name, I32 create));
1441 Returns the SV of the specified Perl scalar. If C<create> is set and the
1442 Perl variable does not exist then it will be created. If C<create> is not
1443 set and the variable does not exist then null is returned.
1445 SV* perl_get_sv _((char* name, I32 create));
1449 Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
1451 =item perl_require_pv
1453 Tells Perl to C<require> a module.
1455 void perl_require_pv _((char* pv));
1459 Tells a Perl interpreter to run. See L<perlembed>.
1463 Pops an integer off the stack.
1469 Pops a long off the stack.
1475 Pops a string off the stack.
1481 Pops a double off the stack.
1487 Pops an SV off the stack.
1493 Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
1499 Push an integer onto the stack. The stack must have room for this element.
1506 Push a double onto the stack. The stack must have room for this element.
1513 Push a string onto the stack. The stack must have room for this element.
1514 The C<len> indicates the length of the string. See C<XPUSHp>.
1516 PUSHp(char *c, int len )
1520 Push an SV onto the stack. The stack must have room for this element. See
1527 Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
1528 See C<PUSHMARK> and L<perlcall> for other uses.
1534 The XSUB-writer's interface to the C C<realloc> function.
1536 void * Renew( void *ptr, int size, type )
1540 The XSUB-writer's interface to the C C<realloc> function, with cast.
1542 void * Renewc( void *ptr, int size, type, cast )
1546 Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
1547 This is always the proper type for the XSUB. See L<perlxs>.
1551 The XSUB-writer's interface to the C C<free> function.
1555 The XSUB-writer's interface to the C C<malloc> function.
1559 The XSUB-writer's interface to the C C<realloc> function.
1563 Copy a string to a safe spot. This does not use an SV.
1565 char* savepv _((char* sv));
1569 Copy a string to a safe spot. The C<len> indicates number of bytes to
1570 copy. This does not use an SV.
1572 char* savepvn _((char* sv, I32 len));
1576 Opening bracket for temporaries on a callback. See C<FREETMPS> and
1583 Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
1588 Refetch the stack pointer. Used after a callback. See L<perlcall>.
1594 Used to access elements on the XSUB's stack.
1600 Test two strings to see if they are equal. Returns true or false.
1602 int strEQ( char *s1, char *s2 )
1606 Test two strings to see if the first, C<s1>, is greater than or equal to the
1607 second, C<s2>. Returns true or false.
1609 int strGE( char *s1, char *s2 )
1613 Test two strings to see if the first, C<s1>, is greater than the second,
1614 C<s2>. Returns true or false.
1616 int strGT( char *s1, char *s2 )
1620 Test two strings to see if the first, C<s1>, is less than or equal to the
1621 second, C<s2>. Returns true or false.
1623 int strLE( char *s1, char *s2 )
1627 Test two strings to see if the first, C<s1>, is less than the second,
1628 C<s2>. Returns true or false.
1630 int strLT( char *s1, char *s2 )
1634 Test two strings to see if they are different. Returns true or false.
1636 int strNE( char *s1, char *s2 )
1640 Test two strings to see if they are equal. The C<len> parameter indicates
1641 the number of bytes to compare. Returns true or false.
1643 int strnEQ( char *s1, char *s2 )
1647 Test two strings to see if they are different. The C<len> parameter
1648 indicates the number of bytes to compare. Returns true or false.
1650 int strnNE( char *s1, char *s2, int len )
1654 Marks an SV as mortal. The SV will be destroyed when the current context
1657 SV* sv_2mortal _((SV* sv));
1661 Blesses an SV into a specified package. The SV must be an RV. The package
1662 must be designated by its stash (see C<gv_stashpv()>). The refcount of the
1665 SV* sv_bless _((SV* sv, HV* stash));
1669 Concatenates the string onto the end of the string which is in the SV.
1671 void sv_catpv _((SV* sv, char* ptr));
1675 Concatenates the string onto the end of the string which is in the SV. The
1676 C<len> indicates number of bytes to copy.
1678 void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
1682 Concatentates the string from SV C<ssv> onto the end of the string in SV
1685 void sv_catsv _((SV* dsv, SV* ssv));
1689 Returns the length of the string which is in the SV. See C<SvLEN>.
1695 Set the length of the string which is in the SV. See C<SvCUR>.
1697 SvCUR_set (SV* sv, int val )
1701 Returns a pointer to the last character in the string which is in the SV.
1702 See C<SvCUR>. Access the character as
1708 Expands the character buffer in the SV.
1710 char * SvGROW( SV* sv, int len )
1714 Returns a boolean indicating whether the SV contains an integer.
1720 Unsets the IV status of an SV.
1726 Tells an SV that it is an integer.
1732 Returns a boolean indicating whether the SV contains an integer. Checks the
1733 B<private> setting. Use C<SvIOK>.
1739 Returns a boolean indicating whether the SV is blessed into the specified
1740 class. This does not know how to check for subtype, so it doesn't work in
1741 an inheritance relationship.
1743 int sv_isa _((SV* sv, char* name));
1747 Returns the integer which is in the SV.
1753 Returns a boolean indicating whether the SV is an RV pointing to a blessed
1754 object. If the SV is not an RV, or if the object is not blessed, then this
1757 int sv_isobject _((SV* sv));
1761 Returns the integer which is stored in the SV.
1767 Returns the size of the string buffer in the SV. See C<SvCUR>.
1773 Adds magic to an SV.
1775 void sv_magic _((SV* sv, SV* obj, int how, char* name, I32 namlen));
1779 Creates a new SV which is a copy of the original SV. The new SV is marked
1782 SV* sv_mortalcopy _((SV* oldsv));
1786 Returns a boolean indicating whether the value is an SV.
1792 Creates a new SV which is mortal. The refcount of the SV is set to 1.
1794 SV* sv_newmortal _((void));
1798 This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
1802 Returns a boolean indicating whether the SV contains a number, integer or
1809 Unsets the NV/IV status of an SV.
1815 Returns a boolean indicating whether the SV contains a number, integer or
1816 double. Checks the B<private> setting. Use C<SvNIOK>.
1818 int SvNIOKp (SV* SV)
1822 Returns a boolean indicating whether the SV contains a double.
1828 Unsets the NV status of an SV.
1834 Tells an SV that it is a double.
1840 Returns a boolean indicating whether the SV contains a double. Checks the
1841 B<private> setting. Use C<SvNOK>.
1847 Returns the double which is stored in the SV.
1849 double SvNV (SV* sv);
1853 Returns the double which is stored in the SV.
1855 double SvNVX (SV* sv);
1859 Returns a boolean indicating whether the SV contains a character string.
1865 Unsets the PV status of an SV.
1871 Tells an SV that it is a string.
1877 Returns a boolean indicating whether the SV contains a character string.
1878 Checks the B<private> setting. Use C<SvPOK>.
1884 Returns a pointer to the string in the SV, or a stringified form of the SV
1885 if the SV does not contain a string. If C<len> is C<na> then Perl will
1886 handle the length on its own.
1888 char * SvPV (SV* sv, int len )
1892 Returns a pointer to the string in the SV. The SV must contain a string.
1894 char * SvPVX (SV* sv)
1898 Returns the value of the object's refcount.
1900 int SvREFCNT (SV* sv);
1904 Decrements the refcount of the given SV.
1906 void SvREFCNT_dec (SV* sv)
1910 Increments the refcount of the given SV.
1912 void SvREFCNT_inc (SV* sv)
1916 Tests if the SV is an RV.
1922 Unsets the RV status of an SV.
1928 Tells an SV that it is an RV.
1934 Dereferences an RV to return the SV.
1940 Copies an integer into the given SV.
1942 void sv_setiv _((SV* sv, IV num));
1946 Copies a double into the given SV.
1948 void sv_setnv _((SV* sv, double num));
1952 Copies a string into an SV. The string must be null-terminated.
1954 void sv_setpv _((SV* sv, char* ptr));
1958 Copies a string into an SV. The C<len> parameter indicates the number of
1961 void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
1965 Copies an integer into an SV, optionally blessing the SV. The SV must be an
1966 RV. The C<classname> argument indicates the package for the blessing. Set
1967 C<classname> to C<Nullch> to avoid the blessing. The new SV will be
1968 returned and will have a refcount of 1.
1970 SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
1974 Copies a double into an SV, optionally blessing the SV. The SV must be an
1975 RV. The C<classname> argument indicates the package for the blessing. Set
1976 C<classname> to C<Nullch> to avoid the blessing. The new SV will be
1977 returned and will have a refcount of 1.
1979 SV* sv_setref_nv _((SV *rv, char *classname, double nv));
1983 Copies a pointer into an SV, optionally blessing the SV. The SV must be an
1984 RV. If the C<pv> argument is NULL then C<sv_undef> will be placed into the
1985 SV. The C<classname> argument indicates the package for the blessing. Set
1986 C<classname> to C<Nullch> to avoid the blessing. The new SV will be
1987 returned and will have a refcount of 1.
1989 SV* sv_setref_pv _((SV *rv, char *classname, void* pv));
1991 Do not use with integral Perl types such as HV, AV, SV, CV, because those
1992 objects will become corrupted by the pointer copy process.
1994 Note that C<sv_setref_pvn> copies the string while this copies the pointer.
1998 Copies a string into an SV, optionally blessing the SV. The lenth of the
1999 string must be specified with C<n>. The SV must be an RV. The C<classname>
2000 argument indicates the package for the blessing. Set C<classname> to
2001 C<Nullch> to avoid the blessing. The new SV will be returned and will have
2004 SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
2006 Note that C<sv_setref_pv> copies the pointer while this copies the string.
2010 Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
2011 (B<NOTE:> If C<ssv> has the C<SVs_TEMP> bit set, C<sv_setsv> may simply steal
2012 the string from C<ssv> and give it to C<dsv>, leaving C<ssv> empty.
2015 void sv_setsv _((SV* dsv, SV* ssv));
2019 Returns the stash of the SV.
2021 HV * SvSTASH (SV* sv)
2025 Integer type flag for scalars. See C<svtype>.
2029 Pointer type flag for scalars. See C<svtype>.
2033 Type flag for arrays. See C<svtype>.
2037 Type flag for code refs. See C<svtype>.
2041 Type flag for hashes. See C<svtype>.
2045 Type flag for blessed scalars. See C<svtype>.
2049 Double type flag for scalars. See C<svtype>.
2053 Returns a boolean indicating whether Perl would evaluate the SV as true or
2054 false, defined or undefined.
2060 Returns the type of the SV. See C<svtype>.
2062 svtype SvTYPE (SV* sv)
2066 An enum of flags for Perl types. These are found in the file B<sv.h> in the
2067 C<svtype> enum. Test these flags with the C<SvTYPE> macro.
2071 Used to upgrade an SV to a more complex form. See C<svtype>.
2075 This is the C<undef> SV. Always refer to this as C<&sv_undef>.
2079 Tells an SV to use C<ptr> to find its string value. Normally the string is
2080 stored inside the SV; this allows the SV to use an outside string. The
2081 string length, C<len>, must be supplied. This function will realloc the
2082 memory pointed to by C<ptr>, so that pointer should not be freed or used by
2083 the programmer after giving it to sv_usepvn.
2085 void sv_usepvn _((SV* sv, char* ptr, STRLEN len));
2089 This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
2093 Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
2094 This is always the proper type for the C++ object. See C<CLASS> and
2099 Converts the specified character to lowercase.
2101 int toLOWER (char c)
2105 Converts the specified character to uppercase.
2107 int toUPPER (char c)
2111 This is the XSUB-writer's interface to Perl's C<warn> function. Use this
2112 function the same way you use the C C<printf> function. See C<croak()>.
2116 Push an integer onto the stack, extending the stack if necessary. See
2123 Push a double onto the stack, extending the stack if necessary. See
2130 Push a string onto the stack, extending the stack if necessary. The C<len>
2131 indicates the length of the string. See C<PUSHp>.
2133 XPUSHp(char *c, int len)
2137 Push an SV onto the stack, extending the stack if necessary. See C<PUSHs>.
2143 Return from XSUB, indicating number of items on the stack. This is usually
2144 handled by C<xsubpp>.
2148 =item XSRETURN_EMPTY
2150 Return from an XSUB immediately.
2156 Return C<false> from an XSUB immediately.
2160 =item XSRETURN_UNDEF
2162 Return C<undef> from an XSUB immediately.
2168 Return C<true> from an XSUB immediately.
2174 The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
2175 destination, C<n> is the number of items, and C<t> is the type.
2177 (void) Zero( d, n, t );
2183 Jeff Okamoto <okamoto@corp.hp.com>
2185 With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
2186 Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
2187 Bowers, Matthew Green, Tim Bunce, and Spider Boardman.
2189 API Listing by Dean Roehrich <roehrich@cray.com>.
2193 Version 20: 1995/12/14