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.
15 Perl has three typedefs that handle Perl's three main data types:
21 Each typedef has specific routines that manipulate the various data types.
23 =head2 What is an "IV"?
25 Perl uses a special typedef IV which is a simple integer type that is
26 guaranteed to be large enough to hold a pointer (as well as an integer).
28 Perl also uses two special typedefs, I32 and I16, which will always be at
29 least 32-bits and 16-bits long, respectively.
31 =head2 Working with SVs
33 An SV can be created and loaded with one command. There are four types of
34 values that can be loaded: an integer value (IV), a double (NV), a string,
35 (PV), and another scalar (SV).
37 The five routines are:
41 SV* newSVpv(char*, int);
42 SV* newSVpvf(const char*, ...);
45 To change the value of an *already-existing* SV, there are six routines:
47 void sv_setiv(SV*, IV);
48 void sv_setnv(SV*, double);
49 void sv_setpv(SV*, char*);
50 void sv_setpvn(SV*, char*, int)
51 void sv_setpvf(SV*, const char*, ...);
52 void sv_setsv(SV*, SV*);
54 Notice that you can choose to specify the length of the string to be
55 assigned by using C<sv_setpvn> or C<newSVpv>, or you may allow Perl to
56 calculate the length by using C<sv_setpv> or by specifying 0 as the second
57 argument to C<newSVpv>. Be warned, though, that Perl will determine the
58 string's length by using C<strlen>, which depends on the string terminating
59 with a NUL character. The arguments of C<sv_setpvf> are processed like
60 C<sprintf>, and the formatted output becomes the value.
62 All SVs that will contain strings should, but need not, be terminated
63 with a NUL character. If it is not NUL-terminated there is a risk of
64 core dumps and corruptions from code which passes the string to C
65 functions or system calls which expect a NUL-terminated string.
66 Perl's own functions typically add a trailing NUL for this reason.
67 Nevertheless, you should be very careful when you pass a string stored
68 in an SV to a C function or system call.
70 To access the actual value that an SV points to, you can use the macros:
76 which will automatically coerce the actual scalar type into an IV, double,
79 In the C<SvPV> macro, the length of the string returned is placed into the
80 variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
81 care what the length of the data is, use the global variable C<na>. Remember,
82 however, that Perl allows arbitrary strings of data that may both contain
83 NULs and might not be terminated by a NUL.
85 If you want to know if the scalar value is TRUE, you can use:
89 Although Perl will automatically grow strings for you, if you need to force
90 Perl to allocate more memory for your SV, you can use the macro
92 SvGROW(SV*, STRLEN newlen)
94 which will determine if more memory needs to be allocated. If so, it will
95 call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
96 decrease, the allocated memory of an SV and that it does not automatically
97 add a byte for the a trailing NUL (perl's own string functions typically do
98 C<SvGROW(sv, len + 1)>).
100 If you have an SV and want to know what kind of data Perl thinks is stored
101 in it, you can use the following macros to check the type of SV you have.
107 You can get and set the current length of the string stored in an SV with
108 the following macros:
111 SvCUR_set(SV*, I32 val)
113 You can also get a pointer to the end of the string stored in the SV
118 But note that these last three macros are valid only if C<SvPOK()> is true.
120 If you want to append something to the end of string stored in an C<SV*>,
121 you can use the following functions:
123 void sv_catpv(SV*, char*);
124 void sv_catpvn(SV*, char*, int);
125 void sv_catpvf(SV*, const char*, ...);
126 void sv_catsv(SV*, SV*);
128 The first function calculates the length of the string to be appended by
129 using C<strlen>. In the second, you specify the length of the string
130 yourself. The third function processes its arguments like C<sprintf> and
131 appends the formatted output. The fourth function extends the string
132 stored in the first SV with the string stored in the second SV. It also
133 forces the second SV to be interpreted as a string.
135 If you know the name of a scalar variable, you can get a pointer to its SV
136 by using the following:
138 SV* perl_get_sv("package::varname", FALSE);
140 This returns NULL if the variable does not exist.
142 If you want to know if this variable (or any other SV) is actually C<defined>,
147 The scalar C<undef> value is stored in an SV instance called C<sv_undef>. Its
148 address can be used whenever an C<SV*> is needed.
150 There are also the two values C<sv_yes> and C<sv_no>, which contain Boolean
151 TRUE and FALSE values, respectively. Like C<sv_undef>, their addresses can
152 be used whenever an C<SV*> is needed.
154 Do not be fooled into thinking that C<(SV *) 0> is the same as C<&sv_undef>.
158 if (I-am-to-return-a-real-value) {
159 sv = sv_2mortal(newSViv(42));
163 This code tries to return a new SV (which contains the value 42) if it should
164 return a real value, or undef otherwise. Instead it has returned a null
165 pointer which, somewhere down the line, will cause a segmentation violation,
166 bus error, or just weird results. Change the zero to C<&sv_undef> in the first
167 line and all will be well.
169 To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
170 call is not necessary (see L<Reference Counts and Mortality>).
172 =head2 What's Really Stored in an SV?
174 Recall that the usual method of determining the type of scalar you have is
175 to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
176 usually these macros will always return TRUE and calling the C<Sv*V>
177 macros will do the appropriate conversion of string to integer/double or
178 integer/double to string.
180 If you I<really> need to know if you have an integer, double, or string
181 pointer in an SV, you can use the following three macros instead:
187 These will tell you if you truly have an integer, double, or string pointer
188 stored in your SV. The "p" stands for private.
190 In general, though, it's best to use the C<Sv*V> macros.
192 =head2 Working with AVs
194 There are two ways to create and load an AV. The first method creates an
199 The second method both creates the AV and initially populates it with SVs:
201 AV* av_make(I32 num, SV **ptr);
203 The second argument points to an array containing C<num> C<SV*>'s. Once the
204 AV has been created, the SVs can be destroyed, if so desired.
206 Once the AV has been created, the following operations are possible on AVs:
208 void av_push(AV*, SV*);
211 void av_unshift(AV*, I32 num);
213 These should be familiar operations, with the exception of C<av_unshift>.
214 This routine adds C<num> elements at the front of the array with the C<undef>
215 value. You must then use C<av_store> (described below) to assign values
216 to these new elements.
218 Here are some other functions:
221 SV** av_fetch(AV*, I32 key, I32 lval);
222 SV** av_store(AV*, I32 key, SV* val);
224 The C<av_len> function returns the highest index value in array (just
225 like $#array in Perl). If the array is empty, -1 is returned. The
226 C<av_fetch> function returns the value at index C<key>, but if C<lval>
227 is non-zero, then C<av_fetch> will store an undef value at that index.
228 The C<av_store> function stores the value C<val> at index C<key>.
229 note that C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s
230 as their return value.
234 void av_extend(AV*, I32 key);
236 The C<av_clear> function deletes all the elements in the AV* array, but
237 does not actually delete the array itself. The C<av_undef> function will
238 delete all the elements in the array plus the array itself. The
239 C<av_extend> function extends the array so that it contains C<key>
240 elements. If C<key> is less than the current length of the array, then
243 If you know the name of an array variable, you can get a pointer to its AV
244 by using the following:
246 AV* perl_get_av("package::varname", FALSE);
248 This returns NULL if the variable does not exist.
250 =head2 Working with HVs
252 To create an HV, you use the following routine:
256 Once the HV has been created, the following operations are possible on HVs:
258 SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
259 SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
261 The C<klen> parameter is the length of the key being passed in (Note that
262 you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
263 length of the key). The C<val> argument contains the SV pointer to the
264 scalar being stored, and C<hash> is the precomputed hash value (zero if
265 you want C<hv_store> to calculate it for you). The C<lval> parameter
266 indicates whether this fetch is actually a part of a store operation, in
267 which case a new undefined value will be added to the HV with the supplied
268 key and C<hv_fetch> will return as if the value had already existed.
270 Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
271 C<SV*>. To access the scalar value, you must first dereference the return
272 value. However, you should check to make sure that the return value is
273 not NULL before dereferencing it.
275 These two functions check if a hash table entry exists, and deletes it.
277 bool hv_exists(HV*, char* key, U32 klen);
278 SV* hv_delete(HV*, char* key, U32 klen, I32 flags);
280 If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
281 create and return a mortal copy of the deleted value.
283 And more miscellaneous functions:
288 Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
289 table but does not actually delete the hash table. The C<hv_undef> deletes
290 both the entries and the hash table itself.
292 Perl keeps the actual data in linked list of structures with a typedef of HE.
293 These contain the actual key and value pointers (plus extra administrative
294 overhead). The key is a string pointer; the value is an C<SV*>. However,
295 once you have an C<HE*>, to get the actual key and value, use the routines
298 I32 hv_iterinit(HV*);
299 /* Prepares starting point to traverse hash table */
300 HE* hv_iternext(HV*);
301 /* Get the next entry, and return a pointer to a
302 structure that has both the key and value */
303 char* hv_iterkey(HE* entry, I32* retlen);
304 /* Get the key from an HE structure and also return
305 the length of the key string */
306 SV* hv_iterval(HV*, HE* entry);
307 /* Return a SV pointer to the value of the HE
309 SV* hv_iternextsv(HV*, char** key, I32* retlen);
310 /* This convenience routine combines hv_iternext,
311 hv_iterkey, and hv_iterval. The key and retlen
312 arguments are return values for the key and its
313 length. The value is returned in the SV* argument */
315 If you know the name of a hash variable, you can get a pointer to its HV
316 by using the following:
318 HV* perl_get_hv("package::varname", FALSE);
320 This returns NULL if the variable does not exist.
322 The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
328 hash = hash * 33 + *s++;
330 =head2 Hash API Extensions
332 Beginning with version 5.004, the following functions are also supported:
334 HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
335 HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
337 bool hv_exists_ent (HV* tb, SV* key, U32 hash);
338 SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
340 SV* hv_iterkeysv (HE* entry);
342 Note that these functions take C<SV*> keys, which simplifies writing
343 of extension code that deals with hash structures. These functions
344 also allow passing of C<SV*> keys to C<tie> functions without forcing
345 you to stringify the keys (unlike the previous set of functions).
347 They also return and accept whole hash entries (C<HE*>), making their
348 use more efficient (since the hash number for a particular string
349 doesn't have to be recomputed every time). See L<API LISTING> later in
350 this document for detailed descriptions.
352 The following macros must always be used to access the contents of hash
353 entries. Note that the arguments to these macros must be simple
354 variables, since they may get evaluated more than once. See
355 L<API LISTING> later in this document for detailed descriptions of these
358 HePV(HE* he, STRLEN len)
362 HeSVKEY_force(HE* he)
363 HeSVKEY_set(HE* he, SV* sv)
365 These two lower level macros are defined, but must only be used when
366 dealing with keys that are not C<SV*>s:
374 References are a special type of scalar that point to other data types
375 (including references).
377 To create a reference, use either of the following functions:
379 SV* newRV_inc((SV*) thing);
380 SV* newRV_noinc((SV*) thing);
382 The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
383 functions are identical except that C<newRV_inc> increments the reference
384 count of the C<thing>, while C<newRV_noinc> does not. For historical
385 reasons, C<newRV> is a synonym for C<newRV_inc>.
387 Once you have a reference, you can use the following macro to dereference
392 then call the appropriate routines, casting the returned C<SV*> to either an
393 C<AV*> or C<HV*>, if required.
395 To determine if an SV is a reference, you can use the following macro:
399 To discover what type of value the reference refers to, use the following
400 macro and then check the return value.
404 The most useful types that will be returned are:
413 SVt_PVGV Glob (possible a file handle)
414 SVt_PVMG Blessed or Magical Scalar
416 See the sv.h header file for more details.
418 =head2 Blessed References and Class Objects
420 References are also used to support object-oriented programming. In the
421 OO lexicon, an object is simply a reference that has been blessed into a
422 package (or class). Once blessed, the programmer may now use the reference
423 to access the various methods in the class.
425 A reference can be blessed into a package with the following function:
427 SV* sv_bless(SV* sv, HV* stash);
429 The C<sv> argument must be a reference. The C<stash> argument specifies
430 which class the reference will belong to. See
431 L<Stashes and Globs> for information on converting class names into stashes.
433 /* Still under construction */
435 Upgrades rv to reference if not already one. Creates new SV for rv to
436 point to. If C<classname> is non-null, the SV is blessed into the specified
437 class. SV is returned.
439 SV* newSVrv(SV* rv, char* classname);
441 Copies integer or double into an SV whose reference is C<rv>. SV is blessed
442 if C<classname> is non-null.
444 SV* sv_setref_iv(SV* rv, char* classname, IV iv);
445 SV* sv_setref_nv(SV* rv, char* classname, NV iv);
447 Copies the pointer value (I<the address, not the string!>) into an SV whose
448 reference is rv. SV is blessed if C<classname> is non-null.
450 SV* sv_setref_pv(SV* rv, char* classname, PV iv);
452 Copies string into an SV whose reference is C<rv>. Set length to 0 to let
453 Perl calculate the string length. SV is blessed if C<classname> is non-null.
455 SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
457 int sv_isa(SV* sv, char* name);
458 int sv_isobject(SV* sv);
460 =head2 Creating New Variables
462 To create a new Perl variable with an undef value which can be accessed from
463 your Perl script, use the following routines, depending on the variable type.
465 SV* perl_get_sv("package::varname", TRUE);
466 AV* perl_get_av("package::varname", TRUE);
467 HV* perl_get_hv("package::varname", TRUE);
469 Notice the use of TRUE as the second parameter. The new variable can now
470 be set, using the routines appropriate to the data type.
472 There are additional macros whose values may be bitwise OR'ed with the
473 C<TRUE> argument to enable certain extra features. Those bits are:
475 GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
476 "Name <varname> used only once: possible typo" warning.
477 GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
478 the variable did not exist before the function was called.
480 If you do not specify a package name, the variable is created in the current
483 =head2 Reference Counts and Mortality
485 Perl uses an reference count-driven garbage collection mechanism. SVs,
486 AVs, or HVs (xV for short in the following) start their life with a
487 reference count of 1. If the reference count of an xV ever drops to 0,
488 then it will be destroyed and its memory made available for reuse.
490 This normally doesn't happen at the Perl level unless a variable is
491 undef'ed or the last variable holding a reference to it is changed or
492 overwritten. At the internal level, however, reference counts can be
493 manipulated with the following macros:
495 int SvREFCNT(SV* sv);
496 SV* SvREFCNT_inc(SV* sv);
497 void SvREFCNT_dec(SV* sv);
499 However, there is one other function which manipulates the reference
500 count of its argument. The C<newRV_inc> function, you will recall,
501 creates a reference to the specified argument. As a side effect,
502 it increments the argument's reference count. If this is not what
503 you want, use C<newRV_noinc> instead.
505 For example, imagine you want to return a reference from an XSUB function.
506 Inside the XSUB routine, you create an SV which initially has a reference
507 count of one. Then you call C<newRV_inc>, passing it the just-created SV.
508 This returns the reference as a new SV, but the reference count of the
509 SV you passed to C<newRV_inc> has been incremented to two. Now you
510 return the reference from the XSUB routine and forget about the SV.
511 But Perl hasn't! Whenever the returned reference is destroyed, the
512 reference count of the original SV is decreased to one and nothing happens.
513 The SV will hang around without any way to access it until Perl itself
514 terminates. This is a memory leak.
516 The correct procedure, then, is to use C<newRV_noinc> instead of
517 C<newRV_inc>. Then, if and when the last reference is destroyed,
518 the reference count of the SV will go to zero and it will be destroyed,
519 stopping any memory leak.
521 There are some convenience functions available that can help with the
522 destruction of xVs. These functions introduce the concept of "mortality".
523 An xV that is mortal has had its reference count marked to be decremented,
524 but not actually decremented, until "a short time later". Generally the
525 term "short time later" means a single Perl statement, such as a call to
526 an XSUB function. The actual determinant for when mortal xVs have their
527 reference count decremented depends on two macros, SAVETMPS and FREETMPS.
528 See L<perlcall> and L<perlxs> for more details on these macros.
530 "Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
531 However, if you mortalize a variable twice, the reference count will
532 later be decremented twice.
534 You should be careful about creating mortal variables. Strange things
535 can happen if you make the same value mortal within multiple contexts,
536 or if you make a variable mortal multiple times.
538 To create a mortal variable, use the functions:
542 SV* sv_mortalcopy(SV*)
544 The first call creates a mortal SV, the second converts an existing
545 SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
546 third creates a mortal copy of an existing SV.
548 The mortal routines are not just for SVs -- AVs and HVs can be
549 made mortal by passing their address (type-casted to C<SV*>) to the
550 C<sv_2mortal> or C<sv_mortalcopy> routines.
552 =head2 Stashes and Globs
554 A "stash" is a hash that contains all of the different objects that
555 are contained within a package. Each key of the stash is a symbol
556 name (shared by all the different types of objects that have the same
557 name), and each value in the hash table is a GV (Glob Value). This GV
558 in turn contains references to the various objects of that name,
559 including (but not limited to) the following:
569 There is a single stash called "defstash" that holds the items that exist
570 in the "main" package. To get at the items in other packages, append the
571 string "::" to the package name. The items in the "Foo" package are in
572 the stash "Foo::" in defstash. The items in the "Bar::Baz" package are
573 in the stash "Baz::" in "Bar::"'s stash.
575 To get the stash pointer for a particular package, use the function:
577 HV* gv_stashpv(char* name, I32 create)
578 HV* gv_stashsv(SV*, I32 create)
580 The first function takes a literal string, the second uses the string stored
581 in the SV. Remember that a stash is just a hash table, so you get back an
582 C<HV*>. The C<create> flag will create a new package if it is set.
584 The name that C<gv_stash*v> wants is the name of the package whose symbol table
585 you want. The default package is called C<main>. If you have multiply nested
586 packages, pass their names to C<gv_stash*v>, separated by C<::> as in the Perl
589 Alternately, if you have an SV that is a blessed reference, you can find
590 out the stash pointer by using:
592 HV* SvSTASH(SvRV(SV*));
594 then use the following to get the package name itself:
596 char* HvNAME(HV* stash);
598 If you need to bless or re-bless an object you can use the following
601 SV* sv_bless(SV*, HV* stash)
603 where the first argument, an C<SV*>, must be a reference, and the second
604 argument is a stash. The returned C<SV*> can now be used in the same way
607 For more information on references and blessings, consult L<perlref>.
609 =head2 Double-Typed SVs
611 Scalar variables normally contain only one type of value, an integer,
612 double, pointer, or reference. Perl will automatically convert the
613 actual scalar data from the stored type into the requested type.
615 Some scalar variables contain more than one type of scalar data. For
616 example, the variable C<$!> contains either the numeric value of C<errno>
617 or its string equivalent from either C<strerror> or C<sys_errlist[]>.
619 To force multiple data values into an SV, you must do two things: use the
620 C<sv_set*v> routines to add the additional scalar type, then set a flag
621 so that Perl will believe it contains more than one type of data. The
622 four macros to set the flags are:
629 The particular macro you must use depends on which C<sv_set*v> routine
630 you called first. This is because every C<sv_set*v> routine turns on
631 only the bit for the particular type of data being set, and turns off
634 For example, to create a new Perl variable called "dberror" that contains
635 both the numeric and descriptive string error values, you could use the
639 extern char *dberror_list;
641 SV* sv = perl_get_sv("dberror", TRUE);
642 sv_setiv(sv, (IV) dberror);
643 sv_setpv(sv, dberror_list[dberror]);
646 If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
647 macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
649 =head2 Magic Variables
651 [This section still under construction. Ignore everything here. Post no
652 bills. Everything not permitted is forbidden.]
654 Any SV may be magical, that is, it has special features that a normal
655 SV does not have. These features are stored in the SV structure in a
656 linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
669 Note this is current as of patchlevel 0, and could change at any time.
671 =head2 Assigning Magic
673 Perl adds magic to an SV using the sv_magic function:
675 void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
677 The C<sv> argument is a pointer to the SV that is to acquire a new magical
680 If C<sv> is not already magical, Perl uses the C<SvUPGRADE> macro to
681 set the C<SVt_PVMG> flag for the C<sv>. Perl then continues by adding
682 it to the beginning of the linked list of magical features. Any prior
683 entry of the same type of magic is deleted. Note that this can be
684 overridden, and multiple instances of the same type of magic can be
685 associated with an SV.
687 The C<name> and C<namlen> arguments are used to associate a string with
688 the magic, typically the name of a variable. C<namlen> is stored in the
689 C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
690 copy of the name is stored in C<mg_ptr> field.
692 The sv_magic function uses C<how> to determine which, if any, predefined
693 "Magic Virtual Table" should be assigned to the C<mg_virtual> field.
694 See the "Magic Virtual Table" section below. The C<how> argument is also
695 stored in the C<mg_type> field.
697 The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
698 structure. If it is not the same as the C<sv> argument, the reference
699 count of the C<obj> object is incremented. If it is the same, or if
700 the C<how> argument is "#", or if it is a null pointer, then C<obj> is
701 merely stored, without the reference count being incremented.
703 There is also a function to add magic to an C<HV>:
705 void hv_magic(HV *hv, GV *gv, int how);
707 This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
709 To remove the magic from an SV, call the function sv_unmagic:
711 void sv_unmagic(SV *sv, int type);
713 The C<type> argument should be equal to the C<how> value when the C<SV>
714 was initially made magical.
716 =head2 Magic Virtual Tables
718 The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
719 C<MGVTBL>, which is a structure of function pointers and stands for
720 "Magic Virtual Table" to handle the various operations that might be
721 applied to that variable.
723 The C<MGVTBL> has five pointers to the following routine types:
725 int (*svt_get)(SV* sv, MAGIC* mg);
726 int (*svt_set)(SV* sv, MAGIC* mg);
727 U32 (*svt_len)(SV* sv, MAGIC* mg);
728 int (*svt_clear)(SV* sv, MAGIC* mg);
729 int (*svt_free)(SV* sv, MAGIC* mg);
731 This MGVTBL structure is set at compile-time in C<perl.h> and there are
732 currently 19 types (or 21 with overloading turned on). These different
733 structures contain pointers to various routines that perform additional
734 actions depending on which function is being called.
736 Function pointer Action taken
737 ---------------- ------------
738 svt_get Do something after the value of the SV is retrieved.
739 svt_set Do something after the SV is assigned a value.
740 svt_len Report on the SV's length.
741 svt_clear Clear something the SV represents.
742 svt_free Free any extra storage associated with the SV.
744 For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
745 to an C<mg_type> of '\0') contains:
747 { magic_get, magic_set, magic_len, 0, 0 }
749 Thus, when an SV is determined to be magical and of type '\0', if a get
750 operation is being performed, the routine C<magic_get> is called. All
751 the various routines for the various magical types begin with C<magic_>.
753 The current kinds of Magic Virtual Tables are:
755 mg_type MGVTBL Type of magical
756 ------- ------ ----------------------------
758 A vtbl_amagic Operator Overloading
759 a vtbl_amagicelem Operator Overloading
760 c 0 Used in Operator Overloading
761 B vtbl_bm Boyer-Moore???
763 e vtbl_envelem %ENV hash element
764 g vtbl_mglob Regexp /g flag???
765 I vtbl_isa @ISA array
766 i vtbl_isaelem @ISA array element
767 L 0 (but sets RMAGICAL) Perl Module/Debugger???
768 l vtbl_dbline Debugger?
769 o vtbl_collxfrm Locale transformation
770 P vtbl_pack Tied Array or Hash
771 p vtbl_packelem Tied Array or Hash element
772 q vtbl_packelem Tied Scalar or Handle
773 S vtbl_sig Signal Hash
774 s vtbl_sigelem Signal Hash element
775 t vtbl_taint Taintedness
778 x vtbl_substr Substring???
779 y vtbl_itervar Shadow "foreach" iterator variable
781 # vtbl_arylen Array Length
782 . vtbl_pos $. scalar variable
783 ~ None Used by certain extensions
785 When an uppercase and lowercase letter both exist in the table, then the
786 uppercase letter is used to represent some kind of composite type (a list
787 or a hash), and the lowercase letter is used to represent an element of
790 The '~' magic type is defined specifically for use by extensions and
791 will not be used by perl itself. Extensions can use ~ magic to 'attach'
792 private information to variables (typically objects). This is especially
793 useful because there is no way for normal perl code to corrupt this
794 private information (unlike using extra elements of a hash object).
796 Note that because multiple extensions may be using ~ magic it is
797 important for extensions to take extra care with it. Typically only
798 using it on objects blessed into the same class as the extension
799 is sufficient. It may also be appropriate to add an I32 'signature'
800 at the top of the private data area and check that.
804 MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
806 This routine returns a pointer to the C<MAGIC> structure stored in the SV.
807 If the SV does not have that magical feature, C<NULL> is returned. Also,
808 if the SV is not of type SVt_PVMG, Perl may core dump.
810 int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
812 This routine checks to see what types of magic C<sv> has. If the mg_type
813 field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
814 the mg_type field is changed to be the lowercase letter.
818 =head2 XSUBs and the Argument Stack
820 The XSUB mechanism is a simple way for Perl programs to access C subroutines.
821 An XSUB routine will have a stack that contains the arguments from the Perl
822 program, and a way to map from the Perl data structures to a C equivalent.
824 The stack arguments are accessible through the C<ST(n)> macro, which returns
825 the C<n>'th stack argument. Argument 0 is the first argument passed in the
826 Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
829 Most of the time, output from the C routine can be handled through use of
830 the RETVAL and OUTPUT directives. However, there are some cases where the
831 argument stack is not already long enough to handle all the return values.
832 An example is the POSIX tzname() call, which takes no arguments, but returns
833 two, the local time zone's standard and summer time abbreviations.
835 To handle this situation, the PPCODE directive is used and the stack is
836 extended using the macro:
840 where C<sp> is the stack pointer, and C<num> is the number of elements the
841 stack should be extended by.
843 Now that there is room on the stack, values can be pushed on it using the
844 macros to push IVs, doubles, strings, and SV pointers respectively:
851 And now the Perl program calling C<tzname>, the two values will be assigned
854 ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
856 An alternate (and possibly simpler) method to pushing values on the stack is
864 These macros automatically adjust the stack for you, if needed. Thus, you
865 do not need to call C<EXTEND> to extend the stack.
867 For more information, consult L<perlxs> and L<perlxstut>.
869 =head2 Calling Perl Routines from within C Programs
871 There are four routines that can be used to call a Perl subroutine from
872 within a C program. These four are:
874 I32 perl_call_sv(SV*, I32);
875 I32 perl_call_pv(char*, I32);
876 I32 perl_call_method(char*, I32);
877 I32 perl_call_argv(char*, I32, register char**);
879 The routine most often used is C<perl_call_sv>. The C<SV*> argument
880 contains either the name of the Perl subroutine to be called, or a
881 reference to the subroutine. The second argument consists of flags
882 that control the context in which the subroutine is called, whether
883 or not the subroutine is being passed arguments, how errors should be
884 trapped, and how to treat return values.
886 All four routines return the number of arguments that the subroutine returned
889 When using any of these routines (except C<perl_call_argv>), the programmer
890 must manipulate the Perl stack. These include the following macros and
904 For a detailed description of calling conventions from C to Perl,
907 =head2 Memory Allocation
909 It is suggested that you use the version of malloc that is distributed
910 with Perl. It keeps pools of various sizes of unallocated memory in
911 order to satisfy allocation requests more quickly. However, on some
912 platforms, it may cause spurious malloc or free errors.
914 New(x, pointer, number, type);
915 Newc(x, pointer, number, type, cast);
916 Newz(x, pointer, number, type);
918 These three macros are used to initially allocate memory.
920 The first argument C<x> was a "magic cookie" that was used to keep track
921 of who called the macro, to help when debugging memory problems. However,
922 the current code makes no use of this feature (most Perl developers now
923 use run-time memory checkers), so this argument can be any number.
925 The second argument C<pointer> should be the name of a variable that will
926 point to the newly allocated memory.
928 The third and fourth arguments C<number> and C<type> specify how many of
929 the specified type of data structure should be allocated. The argument
930 C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
931 should be used if the C<pointer> argument is different from the C<type>
934 Unlike the C<New> and C<Newc> macros, the C<Newz> macro calls C<memzero>
935 to zero out all the newly allocated memory.
937 Renew(pointer, number, type);
938 Renewc(pointer, number, type, cast);
941 These three macros are used to change a memory buffer size or to free a
942 piece of memory no longer needed. The arguments to C<Renew> and C<Renewc>
943 match those of C<New> and C<Newc> with the exception of not needing the
944 "magic cookie" argument.
946 Move(source, dest, number, type);
947 Copy(source, dest, number, type);
948 Zero(dest, number, type);
950 These three macros are used to move, copy, or zero out previously allocated
951 memory. The C<source> and C<dest> arguments point to the source and
952 destination starting points. Perl will move, copy, or zero out C<number>
953 instances of the size of the C<type> data structure (using the C<sizeof>
958 The most recent development releases of Perl has been experimenting with
959 removing Perl's dependency on the "normal" standard I/O suite and allowing
960 other stdio implementations to be used. This involves creating a new
961 abstraction layer that then calls whichever implementation of stdio Perl
962 was compiled with. All XSUBs should now use the functions in the PerlIO
963 abstraction layer and not make any assumptions about what kind of stdio
966 For a complete description of the PerlIO abstraction, consult L<perlapio>.
968 =head2 Putting a C value on Perl stack
970 A lot of opcodes (this is an elementary operation in the internal perl
971 stack machine) put an SV* on the stack. However, as an optimization
972 the corresponding SV is (usually) not recreated each time. The opcodes
973 reuse specially assigned SVs (I<target>s) which are (as a corollary)
974 not constantly freed/created.
976 Each of the targets is created only once (but see
977 L<Scratchpads and recursion> below), and when an opcode needs to put
978 an integer, a double, or a string on stack, it just sets the
979 corresponding parts of its I<target> and puts the I<target> on stack.
981 The macro to put this target on stack is C<PUSHTARG>, and it is
982 directly used in some opcodes, as well as indirectly in zillions of
983 others, which use it via C<(X)PUSH[pni]>.
987 The question remains on when the SVs which are I<target>s for opcodes
988 are created. The answer is that they are created when the current unit --
989 a subroutine or a file (for opcodes for statements outside of
990 subroutines) -- is compiled. During this time a special anonymous Perl
991 array is created, which is called a scratchpad for the current
994 A scratchpad keeps SVs which are lexicals for the current unit and are
995 targets for opcodes. One can deduce that an SV lives on a scratchpad
996 by looking on its flags: lexicals have C<SVs_PADMY> set, and
997 I<target>s have C<SVs_PADTMP> set.
999 The correspondence between OPs and I<target>s is not 1-to-1. Different
1000 OPs in the compile tree of the unit can use the same target, if this
1001 would not conflict with the expected life of the temporary.
1003 =head2 Scratchpads and recursion
1005 In fact it is not 100% true that a compiled unit contains a pointer to
1006 the scratchpad AV. In fact it contains a pointer to an AV of
1007 (initially) one element, and this element is the scratchpad AV. Why do
1008 we need an extra level of indirection?
1010 The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
1011 these can create several execution pointers going into the same
1012 subroutine. For the subroutine-child not write over the temporaries
1013 for the subroutine-parent (lifespan of which covers the call to the
1014 child), the parent and the child should have different
1015 scratchpads. (I<And> the lexicals should be separate anyway!)
1017 So each subroutine is born with an array of scratchpads (of length 1).
1018 On each entry to the subroutine it is checked that the current
1019 depth of the recursion is not more than the length of this array, and
1020 if it is, new scratchpad is created and pushed into the array.
1022 The I<target>s on this scratchpad are C<undef>s, but they are already
1023 marked with correct flags.
1025 =head1 Compiled code
1029 Here we describe the internal form your code is converted to by
1030 Perl. Start with a simple example:
1034 This is converted to a tree similar to this one:
1042 (but slightly more complicated). This tree reflect the way Perl
1043 parsed your code, but has nothing to do with the execution order.
1044 There is an additional "thread" going through the nodes of the tree
1045 which shows the order of execution of the nodes. In our simplified
1046 example above it looks like:
1048 $b ---> $c ---> + ---> $a ---> assign-to
1050 But with the actual compile tree for C<$a = $b + $c> it is different:
1051 some nodes I<optimized away>. As a corollary, though the actual tree
1052 contains more nodes than our simplified example, the execution order
1053 is the same as in our example.
1055 =head2 Examining the tree
1057 If you have your perl compiled for debugging (usually done with C<-D
1058 optimize=-g> on C<Configure> command line), you may examine the
1059 compiled tree by specifying C<-Dx> on the Perl command line. The
1060 output takes several lines per node, and for C<$b+$c> it looks like
1065 FLAGS = (SCALAR,KIDS)
1067 TYPE = null ===> (4)
1069 FLAGS = (SCALAR,KIDS)
1071 3 TYPE = gvsv ===> 4
1077 TYPE = null ===> (5)
1079 FLAGS = (SCALAR,KIDS)
1081 4 TYPE = gvsv ===> 5
1087 This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
1088 not optimized away (one per number in the left column). The immediate
1089 children of the given node correspond to C<{}> pairs on the same level
1090 of indentation, thus this listing corresponds to the tree:
1098 The execution order is indicated by C<===E<gt>> marks, thus it is C<3
1099 4 5 6> (node C<6> is not included into above listing), i.e.,
1100 C<gvsv gvsv add whatever>.
1102 =head2 Compile pass 1: check routines
1104 The tree is created by the I<pseudo-compiler> while yacc code feeds it
1105 the constructions it recognizes. Since yacc works bottom-up, so does
1106 the first pass of perl compilation.
1108 What makes this pass interesting for perl developers is that some
1109 optimization may be performed on this pass. This is optimization by
1110 so-called I<check routines>. The correspondence between node names
1111 and corresponding check routines is described in F<opcode.pl> (do not
1112 forget to run C<make regen_headers> if you modify this file).
1114 A check routine is called when the node is fully constructed except
1115 for the execution-order thread. Since at this time there is no
1116 back-links to the currently constructed node, one can do most any
1117 operation to the top-level node, including freeing it and/or creating
1118 new nodes above/below it.
1120 The check routine returns the node which should be inserted into the
1121 tree (if the top-level node was not modified, check routine returns
1124 By convention, check routines have names C<ck_*>. They are usually
1125 called from C<new*OP> subroutines (or C<convert>) (which in turn are
1126 called from F<perly.y>).
1128 =head2 Compile pass 1a: constant folding
1130 Immediately after the check routine is called the returned node is
1131 checked for being compile-time executable. If it is (the value is
1132 judged to be constant) it is immediately executed, and a I<constant>
1133 node with the "return value" of the corresponding subtree is
1134 substituted instead. The subtree is deleted.
1136 If constant folding was not performed, the execution-order thread is
1139 =head2 Compile pass 2: context propagation
1141 When a context for a part of compile tree is known, it is propagated
1142 down through the tree. Aat this time the context can have 5 values
1143 (instead of 2 for runtime context): void, boolean, scalar, list, and
1144 lvalue. In contrast with the pass 1 this pass is processed from top
1145 to bottom: a node's context determines the context for its children.
1147 Additional context-dependent optimizations are performed at this time.
1148 Since at this moment the compile tree contains back-references (via
1149 "thread" pointers), nodes cannot be free()d now. To allow
1150 optimized-away nodes at this stage, such nodes are null()ified instead
1151 of free()ing (i.e. their type is changed to OP_NULL).
1153 =head2 Compile pass 3: peephole optimization
1155 After the compile tree for a subroutine (or for an C<eval> or a file)
1156 is created, an additional pass over the code is performed. This pass
1157 is neither top-down or bottom-up, but in the execution order (with
1158 additional compilications for conditionals). These optimizations are
1159 done in the subroutine peep(). Optimizations performed at this stage
1160 are subject to the same restrictions as in the pass 2.
1164 This is a listing of functions, macros, flags, and variables that may be
1165 useful to extension writers or that may be found while reading other
1176 Clears an array, making it empty.
1178 void av_clear _((AV* ar));
1182 Pre-extend an array. The C<key> is the index to which the array should be
1185 void av_extend _((AV* ar, I32 key));
1189 Returns the SV at the specified index in the array. The C<key> is the
1190 index. If C<lval> is set then the fetch will be part of a store. Check
1191 that the return value is non-null before dereferencing it to a C<SV*>.
1193 SV** av_fetch _((AV* ar, I32 key, I32 lval));
1197 Returns the highest index in the array. Returns -1 if the array is empty.
1199 I32 av_len _((AV* ar));
1203 Creates a new AV and populates it with a list of SVs. The SVs are copied
1204 into the array, so they may be freed after the call to av_make. The new AV
1205 will have a reference count of 1.
1207 AV* av_make _((I32 size, SV** svp));
1211 Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
1214 SV* av_pop _((AV* ar));
1218 Pushes an SV onto the end of the array. The array will grow automatically
1219 to accommodate the addition.
1221 void av_push _((AV* ar, SV* val));
1225 Shifts an SV off the beginning of the array.
1227 SV* av_shift _((AV* ar));
1231 Stores an SV in an array. The array index is specified as C<key>. The
1232 return value will be null if the operation failed, otherwise it can be
1233 dereferenced to get the original C<SV*>.
1235 SV** av_store _((AV* ar, I32 key, SV* val));
1239 Undefines the array.
1241 void av_undef _((AV* ar));
1245 Unshift an SV onto the beginning of the array. The array will grow
1246 automatically to accommodate the addition.
1248 void av_unshift _((AV* ar, I32 num));
1252 Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
1253 constructor. This is always a C<char*>. See C<THIS> and
1254 L<perlxs/"Using XS With C++">.
1258 The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
1259 source, C<d> is the destination, C<n> is the number of items, and C<t> is
1262 (void) Copy( s, d, n, t );
1266 This is the XSUB-writer's interface to Perl's C<die> function. Use this
1267 function the same way you use the C C<printf> function. See C<warn>.
1271 Returns the stash of the CV.
1273 HV * CvSTASH( SV* sv )
1277 When Perl is run in debugging mode, with the B<-d> switch, this SV is a
1278 boolean which indicates whether subs are being single-stepped.
1279 Single-stepping is automatically turned on after every step. This is the C
1280 variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
1284 When Perl is run in debugging mode, with the B<-d> switch, this GV contains
1285 the SV which holds the name of the sub being debugged. This is the C
1286 variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
1287 The sub name can be found by
1289 SvPV( GvSV( DBsub ), na )
1293 Trace variable used when Perl is run in debugging mode, with the B<-d>
1294 switch. This is the C variable which corresponds to Perl's $DB::trace
1295 variable. See C<DBsingle>.
1299 Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
1304 Saves the original stack mark for the XSUB. See C<ORIGMARK>.
1308 The C variable which corresponds to Perl's $^W warning variable.
1312 Declares a stack pointer variable, C<sp>, for the XSUB. See C<SP>.
1316 Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
1317 usually handled automatically by C<xsubpp>. Declares the C<items> variable
1318 to indicate the number of items on the stack.
1322 Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1323 handled automatically by C<xsubpp>.
1327 Sets up the C<ix> variable for an XSUB which has aliases. This is usually
1328 handled automatically by C<xsubpp>.
1332 Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
1338 Used to extend the argument stack for an XSUB's return values.
1340 EXTEND( sp, int x );
1344 Closing bracket for temporaries on a callback. See C<SAVETMPS> and
1351 Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
1355 Indicates that arguments returned from a callback should be discarded. See
1360 Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
1364 A backward-compatible version of C<GIMME_V> which can only return
1365 C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
1369 The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
1370 C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
1371 context, respectively.
1375 Indicates that no arguments are being sent to a callback. See L<perlcall>.
1379 Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
1383 Used to indicate void context. See C<GIMME_V> and L<perlcall>.
1387 Returns the glob with the given C<name> and a defined subroutine or
1388 C<NULL>. The glob lives in the given C<stash>, or in the stashes
1389 accessable via @ISA and @<UNIVERSAL>.
1391 The argument C<level> should be either 0 or -1. If C<level==0>, as a
1392 side-effect creates a glob with the given C<name> in the given
1393 C<stash> which in the case of success contains an alias for the
1394 subroutine, and sets up caching info for this glob. Similarly for all
1395 the searched stashes.
1397 This function grants C<"SUPER"> token as a postfix of the stash name.
1399 The GV returned from C<gv_fetchmeth> may be a method cache entry,
1400 which is not visible to Perl code. So when calling C<perl_call_sv>,
1401 you should not use the GV directly; instead, you should use the
1402 method's CV, which can be obtained from the GV with the C<GvCV> macro.
1404 GV* gv_fetchmeth _((HV* stash, char* name, STRLEN len, I32 level));
1406 =item gv_fetchmethod
1408 =item gv_fetchmethod_autoload
1410 Returns the glob which contains the subroutine to call to invoke the
1411 method on the C<stash>. In fact in the presense of autoloading this may
1412 be the glob for "AUTOLOAD". In this case the corresponding variable
1413 $AUTOLOAD is already setup.
1415 The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
1416 lookup is performed if the given method is not present: non-zero means
1417 yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
1418 C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
1419 non-zero C<autoload> parameter.
1421 These functions grant C<"SUPER"> token as a prefix of the method name.
1423 Note that if you want to keep the returned glob for a long time, you
1424 need to check for it being "AUTOLOAD", since at the later time the call
1425 may load a different subroutine due to $AUTOLOAD changing its value.
1426 Use the glob created via a side effect to do this.
1428 These functions have the same side-effects and as C<gv_fetchmeth> with
1429 C<level==0>. C<name> should be writable if contains C<':'> or C<'\''>.
1430 The warning against passing the GV returned by C<gv_fetchmeth> to
1431 C<perl_call_sv> apply equally to these functions.
1433 GV* gv_fetchmethod _((HV* stash, char* name));
1434 GV* gv_fetchmethod_autoload _((HV* stash, char* name,
1439 Returns a pointer to the stash for a specified package. If C<create> is set
1440 then the package will be created if it does not already exist. If C<create>
1441 is not set and the package does not exist then NULL is returned.
1443 HV* gv_stashpv _((char* name, I32 create));
1447 Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
1449 HV* gv_stashsv _((SV* sv, I32 create));
1453 Return the SV from the GV.
1457 This flag, used in the length slot of hash entries and magic
1458 structures, specifies the structure contains a C<SV*> pointer where a
1459 C<char*> pointer is to be expected. (For information only--not to be used).
1463 Returns the computed hash (type C<U32>) stored in the hash entry.
1469 Returns the actual pointer stored in the key slot of the hash entry.
1470 The pointer may be either C<char*> or C<SV*>, depending on the value of
1471 C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
1472 are usually preferable for finding the value of a key.
1478 If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
1479 holds an C<SV*> key. Otherwise, holds the actual length of the key.
1480 Can be assigned to. The C<HePV()> macro is usually preferable for finding
1487 Returns the key slot of the hash entry as a C<char*> value, doing any
1488 necessary dereferencing of possibly C<SV*> keys. The length of
1489 the string is placed in C<len> (this is a macro, so do I<not> use
1490 C<&len>). If you do not care about what the length of the key is,
1491 you may use the global variable C<na>. Remember though, that hash
1492 keys in perl are free to contain embedded nulls, so using C<strlen()>
1493 or similar is not a good way to find the length of hash keys.
1494 This is very similar to the C<SvPV()> macro described elsewhere in
1497 HePV(HE* he, STRLEN len)
1501 Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
1502 does not contain an C<SV*> key.
1508 Returns the key as an C<SV*>. Will create and return a temporary
1509 mortal C<SV*> if the hash entry contains only a C<char*> key.
1511 HeSVKEY_force(HE* he)
1515 Sets the key to a given C<SV*>, taking care to set the appropriate flags
1516 to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
1518 HeSVKEY_set(HE* he, SV* sv)
1522 Returns the value slot (type C<SV*>) stored in the hash entry.
1528 Clears a hash, making it empty.
1530 void hv_clear _((HV* tb));
1532 =item hv_delayfree_ent
1534 Releases a hash entry, such as while iterating though the hash, but
1535 delays actual freeing of key and value until the end of the current
1536 statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
1539 void hv_delayfree_ent _((HV* hv, HE* entry));
1543 Deletes a key/value pair in the hash. The value SV is removed from the hash
1544 and returned to the caller. The C<klen> is the length of the key. The
1545 C<flags> value will normally be zero; if set to G_DISCARD then null will be
1548 SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));
1552 Deletes a key/value pair in the hash. The value SV is removed from the hash
1553 and returned to the caller. The C<flags> value will normally be zero; if set
1554 to G_DISCARD then null will be returned. C<hash> can be a valid precomputed
1555 hash value, or 0 to ask for it to be computed.
1557 SV* hv_delete_ent _((HV* tb, SV* key, I32 flags, U32 hash));
1561 Returns a boolean indicating whether the specified hash key exists. The
1562 C<klen> is the length of the key.
1564 bool hv_exists _((HV* tb, char* key, U32 klen));
1568 Returns a boolean indicating whether the specified hash key exists. C<hash>
1569 can be a valid precomputed hash value, or 0 to ask for it to be computed.
1571 bool hv_exists_ent _((HV* tb, SV* key, U32 hash));
1575 Returns the SV which corresponds to the specified key in the hash. The
1576 C<klen> is the length of the key. If C<lval> is set then the fetch will be
1577 part of a store. Check that the return value is non-null before
1578 dereferencing it to a C<SV*>.
1580 SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));
1584 Returns the hash entry which corresponds to the specified key in the hash.
1585 C<hash> must be a valid precomputed hash number for the given C<key>, or
1586 0 if you want the function to compute it. IF C<lval> is set then the
1587 fetch will be part of a store. Make sure the return value is non-null
1588 before accessing it. The return value when C<tb> is a tied hash
1589 is a pointer to a static location, so be sure to make a copy of the
1590 structure if you need to store it somewhere.
1592 HE* hv_fetch_ent _((HV* tb, SV* key, I32 lval, U32 hash));
1596 Releases a hash entry, such as while iterating though the hash. See
1597 C<hv_iternext> and C<hv_delayfree_ent>.
1599 void hv_free_ent _((HV* hv, HE* entry));
1603 Prepares a starting point to traverse a hash table.
1605 I32 hv_iterinit _((HV* tb));
1609 Returns the key from the current position of the hash iterator. See
1612 char* hv_iterkey _((HE* entry, I32* retlen));
1616 Returns the key as an C<SV*> from the current position of the hash
1617 iterator. The return value will always be a mortal copy of the
1618 key. Also see C<hv_iterinit>.
1620 SV* hv_iterkeysv _((HE* entry));
1624 Returns entries from a hash iterator. See C<hv_iterinit>.
1626 HE* hv_iternext _((HV* tb));
1630 Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
1633 SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));
1637 Returns the value from the current position of the hash iterator. See
1640 SV* hv_iterval _((HV* tb, HE* entry));
1644 Adds magic to a hash. See C<sv_magic>.
1646 void hv_magic _((HV* hv, GV* gv, int how));
1650 Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
1652 char *HvNAME (HV* stash)
1656 Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
1657 the length of the key. The C<hash> parameter is the precomputed hash
1658 value; if it is zero then Perl will compute it. The return value will be
1659 null if the operation failed, otherwise it can be dereferenced to get the
1662 SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
1666 Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
1667 parameter is the precomputed hash value; if it is zero then Perl will
1668 compute it. The return value is the new hash entry so created. It will be
1669 null if the operation failed or if the entry was stored in a tied hash.
1670 Otherwise the contents of the return value can be accessed using the
1671 C<He???> macros described here.
1673 HE* hv_store_ent _((HV* tb, SV* key, SV* val, U32 hash));
1679 void hv_undef _((HV* tb));
1683 Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
1686 int isALNUM (char c)
1690 Returns a boolean indicating whether the C C<char> is an ascii alphabetic
1693 int isALPHA (char c)
1697 Returns a boolean indicating whether the C C<char> is an ascii digit.
1699 int isDIGIT (char c)
1703 Returns a boolean indicating whether the C C<char> is a lowercase character.
1705 int isLOWER (char c)
1709 Returns a boolean indicating whether the C C<char> is whitespace.
1711 int isSPACE (char c)
1715 Returns a boolean indicating whether the C C<char> is an uppercase character.
1717 int isUPPER (char c)
1721 Variable which is setup by C<xsubpp> to indicate the number of items on the
1722 stack. See L<perlxs/"Variable-length Parameter Lists">.
1726 Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
1727 was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
1731 Closing bracket on a callback. See C<ENTER> and L<perlcall>.
1737 Stack marker variable for the XSUB. See C<dMARK>.
1741 Clear something magical that the SV represents. See C<sv_magic>.
1743 int mg_clear _((SV* sv));
1747 Copies the magic from one SV to another. See C<sv_magic>.
1749 int mg_copy _((SV *, SV *, char *, STRLEN));
1753 Finds the magic pointer for type matching the SV. See C<sv_magic>.
1755 MAGIC* mg_find _((SV* sv, int type));
1759 Free any magic storage used by the SV. See C<sv_magic>.
1761 int mg_free _((SV* sv));
1765 Do magic after a value is retrieved from the SV. See C<sv_magic>.
1767 int mg_get _((SV* sv));
1771 Report on the SV's length. See C<sv_magic>.
1773 U32 mg_len _((SV* sv));
1777 Turns on the magical status of an SV. See C<sv_magic>.
1779 void mg_magical _((SV* sv));
1783 Do magic after a value is assigned to the SV. See C<sv_magic>.
1785 int mg_set _((SV* sv));
1789 The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
1790 source, C<d> is the destination, C<n> is the number of items, and C<t> is
1793 (void) Move( s, d, n, t );
1797 A variable which may be used with C<SvPV> to tell Perl to calculate the
1802 The XSUB-writer's interface to the C C<malloc> function.
1804 void * New( x, void *ptr, int size, type )
1808 The XSUB-writer's interface to the C C<malloc> function, with cast.
1810 void * Newc( x, void *ptr, int size, type, cast )
1814 The XSUB-writer's interface to the C C<malloc> function. The allocated
1815 memory is zeroed with C<memzero>.
1817 void * Newz( x, void *ptr, int size, type )
1821 Creates a new AV. The reference count is set to 1.
1823 AV* newAV _((void));
1827 Creates a new HV. The reference count is set to 1.
1829 HV* newHV _((void));
1833 Creates an RV wrapper for an SV. The reference count for the original SV is
1836 SV* newRV_inc _((SV* ref));
1838 For historical reasons, "newRV" is a synonym for "newRV_inc".
1842 Creates an RV wrapper for an SV. The reference count for the original
1843 SV is B<not> incremented.
1845 SV* newRV_noinc _((SV* ref));
1849 Creates a new SV. The C<len> parameter indicates the number of bytes of
1850 preallocated string space the SV should have. The reference count for the
1853 SV* newSV _((STRLEN len));
1857 Creates a new SV and copies an integer into it. The reference count for the
1860 SV* newSViv _((IV i));
1864 Creates a new SV and copies a double into it. The reference count for the
1867 SV* newSVnv _((NV i));
1871 Creates a new SV and copies a string into it. The reference count for the
1872 SV is set to 1. If C<len> is zero then Perl will compute the length.
1874 SV* newSVpv _((char* s, STRLEN len));
1878 Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
1879 it will be upgraded to one. If C<classname> is non-null then the new SV will
1880 be blessed in the specified package. The new SV is returned and its
1881 reference count is 1.
1883 SV* newSVrv _((SV* rv, char* classname));
1887 Creates a new SV which is an exact duplicate of the original SV.
1889 SV* newSVsv _((SV* old));
1893 Used by C<xsubpp> to hook up XSUBs as Perl subs.
1897 Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
1906 Null character pointer.
1922 The original stack mark for the XSUB. See C<dORIGMARK>.
1926 Allocates a new Perl interpreter. See L<perlembed>.
1928 =item perl_call_argv
1930 Performs a callback to the specified Perl sub. See L<perlcall>.
1932 I32 perl_call_argv _((char* subname, I32 flags, char** argv));
1934 =item perl_call_method
1936 Performs a callback to the specified Perl method. The blessed object must
1937 be on the stack. See L<perlcall>.
1939 I32 perl_call_method _((char* methname, I32 flags));
1943 Performs a callback to the specified Perl sub. See L<perlcall>.
1945 I32 perl_call_pv _((char* subname, I32 flags));
1949 Performs a callback to the Perl sub whose name is in the SV. See
1952 I32 perl_call_sv _((SV* sv, I32 flags));
1954 =item perl_construct
1956 Initializes a new Perl interpreter. See L<perlembed>.
1960 Shuts down a Perl interpreter. See L<perlembed>.
1964 Tells Perl to C<eval> the string in the SV.
1966 I32 perl_eval_sv _((SV* sv, I32 flags));
1970 Tells Perl to C<eval> the given string and return an SV* result.
1972 SV* perl_eval_pv _((char* p, I32 croak_on_error));
1976 Releases a Perl interpreter. See L<perlembed>.
1980 Returns the AV of the specified Perl array. If C<create> is set and the
1981 Perl variable does not exist then it will be created. If C<create> is not
1982 set and the variable does not exist then null is returned.
1984 AV* perl_get_av _((char* name, I32 create));
1988 Returns the CV of the specified Perl sub. If C<create> is set and the Perl
1989 variable does not exist then it will be created. If C<create> is not
1990 set and the variable does not exist then null is returned.
1992 CV* perl_get_cv _((char* name, I32 create));
1996 Returns the HV of the specified Perl hash. If C<create> is set and the Perl
1997 variable does not exist then it will be created. If C<create> is not
1998 set and the variable does not exist then null is returned.
2000 HV* perl_get_hv _((char* name, I32 create));
2004 Returns the SV of the specified Perl scalar. If C<create> is set and the
2005 Perl variable does not exist then it will be created. If C<create> is not
2006 set and the variable does not exist then null is returned.
2008 SV* perl_get_sv _((char* name, I32 create));
2012 Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
2014 =item perl_require_pv
2016 Tells Perl to C<require> a module.
2018 void perl_require_pv _((char* pv));
2022 Tells a Perl interpreter to run. See L<perlembed>.
2026 Pops an integer off the stack.
2032 Pops a long off the stack.
2038 Pops a string off the stack.
2044 Pops a double off the stack.
2050 Pops an SV off the stack.
2056 Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
2062 Push an integer onto the stack. The stack must have room for this element.
2069 Push a double onto the stack. The stack must have room for this element.
2076 Push a string onto the stack. The stack must have room for this element.
2077 The C<len> indicates the length of the string. See C<XPUSHp>.
2079 PUSHp(char *c, int len )
2083 Push an SV onto the stack. The stack must have room for this element. See
2090 Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
2091 See C<PUSHMARK> and L<perlcall> for other uses.
2097 The XSUB-writer's interface to the C C<realloc> function.
2099 void * Renew( void *ptr, int size, type )
2103 The XSUB-writer's interface to the C C<realloc> function, with cast.
2105 void * Renewc( void *ptr, int size, type, cast )
2109 Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
2110 This is always the proper type for the XSUB.
2111 See L<perlxs/"The RETVAL Variable">.
2115 The XSUB-writer's interface to the C C<free> function.
2119 The XSUB-writer's interface to the C C<malloc> function.
2123 The XSUB-writer's interface to the C C<realloc> function.
2127 Copy a string to a safe spot. This does not use an SV.
2129 char* savepv _((char* sv));
2133 Copy a string to a safe spot. The C<len> indicates number of bytes to
2134 copy. This does not use an SV.
2136 char* savepvn _((char* sv, I32 len));
2140 Opening bracket for temporaries on a callback. See C<FREETMPS> and
2147 Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
2152 Refetch the stack pointer. Used after a callback. See L<perlcall>.
2158 Used to access elements on the XSUB's stack.
2164 Test two strings to see if they are equal. Returns true or false.
2166 int strEQ( char *s1, char *s2 )
2170 Test two strings to see if the first, C<s1>, is greater than or equal to the
2171 second, C<s2>. Returns true or false.
2173 int strGE( char *s1, char *s2 )
2177 Test two strings to see if the first, C<s1>, is greater than the second,
2178 C<s2>. Returns true or false.
2180 int strGT( char *s1, char *s2 )
2184 Test two strings to see if the first, C<s1>, is less than or equal to the
2185 second, C<s2>. Returns true or false.
2187 int strLE( char *s1, char *s2 )
2191 Test two strings to see if the first, C<s1>, is less than the second,
2192 C<s2>. Returns true or false.
2194 int strLT( char *s1, char *s2 )
2198 Test two strings to see if they are different. Returns true or false.
2200 int strNE( char *s1, char *s2 )
2204 Test two strings to see if they are equal. The C<len> parameter indicates
2205 the number of bytes to compare. Returns true or false.
2207 int strnEQ( char *s1, char *s2 )
2211 Test two strings to see if they are different. The C<len> parameter
2212 indicates the number of bytes to compare. Returns true or false.
2214 int strnNE( char *s1, char *s2, int len )
2218 Marks an SV as mortal. The SV will be destroyed when the current context
2221 SV* sv_2mortal _((SV* sv));
2225 Blesses an SV into a specified package. The SV must be an RV. The package
2226 must be designated by its stash (see C<gv_stashpv()>). The reference count
2227 of the SV is unaffected.
2229 SV* sv_bless _((SV* sv, HV* stash));
2233 Concatenates the string onto the end of the string which is in the SV.
2235 void sv_catpv _((SV* sv, char* ptr));
2239 Concatenates the string onto the end of the string which is in the SV. The
2240 C<len> indicates number of bytes to copy.
2242 void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
2246 Processes its arguments like C<sprintf> and appends the formatted output
2249 void sv_catpvf _((SV* sv, const char* pat, ...));
2253 Concatenates the string from SV C<ssv> onto the end of the string in SV
2256 void sv_catsv _((SV* dsv, SV* ssv));
2260 Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2261 string in C<sv1> is less than, equal to, or greater than the string in
2264 I32 sv_cmp _((SV* sv1, SV* sv2));
2268 Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
2269 string in C<sv1> is less than, equal to, or greater than the string in
2272 I32 sv_cmp _((SV* sv1, SV* sv2));
2276 Returns the length of the string which is in the SV. See C<SvLEN>.
2282 Set the length of the string which is in the SV. See C<SvCUR>.
2284 SvCUR_set (SV* sv, int val )
2288 Auto-decrement of the value in the SV.
2290 void sv_dec _((SV* sv));
2294 Auto-decrement of the value in the SV.
2296 void sv_dec _((SV* sv));
2300 Returns a pointer to the last character in the string which is in the SV.
2301 See C<SvCUR>. Access the character as
2307 Returns a boolean indicating whether the strings in the two SVs are
2310 I32 sv_eq _((SV* sv1, SV* sv2));
2314 Expands the character buffer in the SV. Calls C<sv_grow> to perform the
2315 expansion if necessary. Returns a pointer to the character buffer.
2317 char * SvGROW( SV* sv, int len )
2321 Expands the character buffer in the SV. This will use C<sv_unref> and will
2322 upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
2327 Auto-increment of the value in the SV.
2329 void sv_inc _((SV* sv));
2333 Returns a boolean indicating whether the SV contains an integer.
2339 Unsets the IV status of an SV.
2345 Tells an SV that it is an integer.
2351 Tells an SV that it is an integer and disables all other OK bits.
2357 Tells an SV that it is an integer and disables all other OK bits.
2363 Returns a boolean indicating whether the SV contains an integer. Checks the
2364 B<private> setting. Use C<SvIOK>.
2370 Returns a boolean indicating whether the SV is blessed into the specified
2371 class. This does not know how to check for subtype, so it doesn't work in
2372 an inheritance relationship.
2374 int sv_isa _((SV* sv, char* name));
2378 Returns the integer which is in the SV.
2384 Returns a boolean indicating whether the SV is an RV pointing to a blessed
2385 object. If the SV is not an RV, or if the object is not blessed, then this
2388 int sv_isobject _((SV* sv));
2392 Returns the integer which is stored in the SV.
2398 Returns the size of the string buffer in the SV. See C<SvCUR>.
2404 Returns the length of the string in the SV. Use C<SvCUR>.
2406 STRLEN sv_len _((SV* sv));
2410 Returns the length of the string in the SV. Use C<SvCUR>.
2412 STRLEN sv_len _((SV* sv));
2416 Adds magic to an SV.
2418 void sv_magic _((SV* sv, SV* obj, int how, char* name, I32 namlen));
2422 Creates a new SV which is a copy of the original SV. The new SV is marked
2425 SV* sv_mortalcopy _((SV* oldsv));
2429 Returns a boolean indicating whether the value is an SV.
2435 Creates a new SV which is mortal. The reference count of the SV is set to 1.
2437 SV* sv_newmortal _((void));
2441 This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
2445 Returns a boolean indicating whether the SV contains a number, integer or
2452 Unsets the NV/IV status of an SV.
2458 Returns a boolean indicating whether the SV contains a number, integer or
2459 double. Checks the B<private> setting. Use C<SvNIOK>.
2461 int SvNIOKp (SV* SV)
2465 Returns a boolean indicating whether the SV contains a double.
2471 Unsets the NV status of an SV.
2477 Tells an SV that it is a double.
2483 Tells an SV that it is a double and disables all other OK bits.
2489 Tells an SV that it is a double and disables all other OK bits.
2495 Returns a boolean indicating whether the SV contains a double. Checks the
2496 B<private> setting. Use C<SvNOK>.
2502 Returns the double which is stored in the SV.
2504 double SvNV (SV* sv);
2508 Returns the double which is stored in the SV.
2510 double SvNVX (SV* sv);
2514 Returns a boolean indicating whether the SV contains a character string.
2520 Unsets the PV status of an SV.
2526 Tells an SV that it is a string.
2532 Tells an SV that it is a string and disables all other OK bits.
2538 Tells an SV that it is a string and disables all other OK bits.
2544 Returns a boolean indicating whether the SV contains a character string.
2545 Checks the B<private> setting. Use C<SvPOK>.
2551 Returns a pointer to the string in the SV, or a stringified form of the SV
2552 if the SV does not contain a string. If C<len> is C<na> then Perl will
2553 handle the length on its own.
2555 char * SvPV (SV* sv, int len )
2559 Returns a pointer to the string in the SV. The SV must contain a string.
2561 char * SvPVX (SV* sv)
2565 Returns the value of the object's reference count.
2567 int SvREFCNT (SV* sv);
2571 Decrements the reference count of the given SV.
2573 void SvREFCNT_dec (SV* sv)
2577 Increments the reference count of the given SV.
2579 void SvREFCNT_inc (SV* sv)
2583 Tests if the SV is an RV.
2589 Unsets the RV status of an SV.
2595 Tells an SV that it is an RV.
2601 Dereferences an RV to return the SV.
2607 Copies an integer into the given SV.
2609 void sv_setiv _((SV* sv, IV num));
2613 Copies a double into the given SV.
2615 void sv_setnv _((SV* sv, double num));
2619 Copies a string into an SV. The string must be null-terminated.
2621 void sv_setpv _((SV* sv, char* ptr));
2625 Copies a string into an SV. The C<len> parameter indicates the number of
2628 void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
2632 Processes its arguments like C<sprintf> and sets an SV to the formatted
2635 void sv_setpvf _((SV* sv, const char* pat, ...));
2639 Copies an integer into a new SV, optionally blessing the SV. The C<rv>
2640 argument will be upgraded to an RV. That RV will be modified to point to
2641 the new SV. The C<classname> argument indicates the package for the
2642 blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
2643 will be returned and will have a reference count of 1.
2645 SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
2649 Copies a double into a new SV, optionally blessing the SV. The C<rv>
2650 argument will be upgraded to an RV. That RV will be modified to point to
2651 the new SV. The C<classname> argument indicates the package for the
2652 blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
2653 will be returned and will have a reference count of 1.
2655 SV* sv_setref_nv _((SV *rv, char *classname, double nv));
2659 Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
2660 argument will be upgraded to an RV. That RV will be modified to point to
2661 the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
2662 into the SV. The C<classname> argument indicates the package for the
2663 blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
2664 will be returned and will have a reference count of 1.
2666 SV* sv_setref_pv _((SV *rv, char *classname, void* pv));
2668 Do not use with integral Perl types such as HV, AV, SV, CV, because those
2669 objects will become corrupted by the pointer copy process.
2671 Note that C<sv_setref_pvn> copies the string while this copies the pointer.
2675 Copies a string into a new SV, optionally blessing the SV. The length of the
2676 string must be specified with C<n>. The C<rv> argument will be upgraded to
2677 an RV. That RV will be modified to point to the new SV. The C<classname>
2678 argument indicates the package for the blessing. Set C<classname> to
2679 C<Nullch> to avoid the blessing. The new SV will be returned and will have
2680 a reference count of 1.
2682 SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
2684 Note that C<sv_setref_pv> copies the pointer while this copies the string.
2688 Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
2689 The source SV may be destroyed if it is mortal.
2691 void sv_setsv _((SV* dsv, SV* ssv));
2695 Returns the stash of the SV.
2697 HV * SvSTASH (SV* sv)
2701 Integer type flag for scalars. See C<svtype>.
2705 Pointer type flag for scalars. See C<svtype>.
2709 Type flag for arrays. See C<svtype>.
2713 Type flag for code refs. See C<svtype>.
2717 Type flag for hashes. See C<svtype>.
2721 Type flag for blessed scalars. See C<svtype>.
2725 Double type flag for scalars. See C<svtype>.
2729 Returns a boolean indicating whether Perl would evaluate the SV as true or
2730 false, defined or undefined.
2736 Returns the type of the SV. See C<svtype>.
2738 svtype SvTYPE (SV* sv)
2742 An enum of flags for Perl types. These are found in the file B<sv.h> in the
2743 C<svtype> enum. Test these flags with the C<SvTYPE> macro.
2747 Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
2748 the upgrade if necessary. See C<svtype>.
2750 bool SvUPGRADE _((SV* sv, svtype mt));
2754 Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
2758 This is the C<undef> SV. Always refer to this as C<&sv_undef>.
2762 Unsets the RV status of the SV, and decrements the reference count of
2763 whatever was being referenced by the RV. This can almost be thought of
2764 as a reversal of C<newSVrv>. See C<SvROK_off>.
2766 void sv_unref _((SV* sv));
2770 Tells an SV to use C<ptr> to find its string value. Normally the string is
2771 stored inside the SV but sv_usepvn allows the SV to use an outside string.
2772 The C<ptr> should point to memory that was allocated by C<malloc>. The
2773 string length, C<len>, must be supplied. This function will realloc the
2774 memory pointed to by C<ptr>, so that pointer should not be freed or used by
2775 the programmer after giving it to sv_usepvn.
2777 void sv_usepvn _((SV* sv, char* ptr, STRLEN len));
2781 This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
2785 Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
2786 This is always the proper type for the C++ object. See C<CLASS> and
2787 L<perlxs/"Using XS With C++">.
2791 Converts the specified character to lowercase.
2793 int toLOWER (char c)
2797 Converts the specified character to uppercase.
2799 int toUPPER (char c)
2803 This is the XSUB-writer's interface to Perl's C<warn> function. Use this
2804 function the same way you use the C C<printf> function. See C<croak()>.
2808 Push an integer onto the stack, extending the stack if necessary. See
2815 Push a double onto the stack, extending the stack if necessary. See
2822 Push a string onto the stack, extending the stack if necessary. The C<len>
2823 indicates the length of the string. See C<PUSHp>.
2825 XPUSHp(char *c, int len)
2829 Push an SV onto the stack, extending the stack if necessary. See C<PUSHs>.
2835 Macro to declare an XSUB and its C parameter list. This is handled by
2840 Return from XSUB, indicating number of items on the stack. This is usually
2841 handled by C<xsubpp>.
2845 =item XSRETURN_EMPTY
2847 Return an empty list from an XSUB immediately.
2853 Return an integer from an XSUB immediately. Uses C<XST_mIV>.
2859 Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
2865 Return an double from an XSUB immediately. Uses C<XST_mNV>.
2871 Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
2873 XSRETURN_PV(char *v);
2875 =item XSRETURN_UNDEF
2877 Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
2883 Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
2889 Place an integer into the specified position C<i> on the stack. The value is
2890 stored in a new mortal SV.
2892 XST_mIV( int i, IV v );
2896 Place a double into the specified position C<i> on the stack. The value is
2897 stored in a new mortal SV.
2899 XST_mNV( int i, NV v );
2903 Place C<&sv_no> into the specified position C<i> on the stack.
2909 Place a copy of a string into the specified position C<i> on the stack. The
2910 value is stored in a new mortal SV.
2912 XST_mPV( int i, char *v );
2916 Place C<&sv_undef> into the specified position C<i> on the stack.
2918 XST_mUNDEF( int i );
2922 Place C<&sv_yes> into the specified position C<i> on the stack.
2928 The version identifier for an XS module. This is usually handled
2929 automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
2931 =item XS_VERSION_BOOTCHECK
2933 Macro to verify that a PM module's $VERSION variable matches the XS module's
2934 C<XS_VERSION> variable. This is usually handled automatically by
2935 C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
2939 The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
2940 destination, C<n> is the number of items, and C<t> is the type.
2942 (void) Zero( d, n, t );
2948 Jeff Okamoto <F<okamoto@corp.hp.com>>
2950 With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
2951 Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
2952 Bowers, Matthew Green, Tim Bunce, Spider Boardman, and Ulrich Pfeifer.
2954 API Listing by Dean Roehrich <F<roehrich@cray.com>>.
2958 Version 31.6: 1997/4/14