NAME

perlguts - Perl's Internal Functions


DESCRIPTION

This document attempts to describe some of the internal functions of the Perl executable. It is far from complete and probably contains many errors. Please refer any questions or comments to the author below.


Datatypes

Perl has three typedefs that handle Perl's three main data types:

SV Scalar Value AV Array Value HV Hash Value

Each typedef has specific routines that manipulate the various data types.

What is an ``IV''?

Perl uses a special typedef IV which is large enough to hold either an integer or a pointer.

Perl also uses two special typedefs, I32 and I16, which will always be at least 32-bits and 16-bits long, respectively.

Working with SVs

An SV can be created and loaded with one command. There are four types of values that can be loaded: an integer value (IV), a double (NV), a string, (PV), and another scalar (SV).

The four routines are:

SV* newSViv(IV); SV* newSVnv(double); SV* newSVpv(char*, int); SV* newSVsv(SV*);

To change the value of an *already-existing* SV, there are five routines:

void sv_setiv(SV*, IV); void sv_setnv(SV*, double); void sv_setpvn(SV*, char*, int) void sv_setpv(SV*, char*); void sv_setsv(SV*, SV*);

Notice that you can choose to specify the length of the string to be assigned by using sv_setpvn or newSVpv , or you may allow Perl to calculate the length by using sv_setpv or by specifying 0 as the second argument to newSVpv . Be warned, though, that Perl will determine the string's length by using strlen, which depends on the string terminating with a NUL character.

To access the actual value that an SV points to, you can use the macros:

SvIV(SV*) SvNV(SV*) SvPV(SV*, STRLEN len)

which will automatically coerce the actual scalar type into an IV, double, or string.

In the SvPV macro, the length of the string returned is placed into the variable len (this is a macro, so you do not use &len). If you do not care what the length of the data is, use the global variable na . Remember, however, that Perl allows arbitrary strings of data that may both contain NULs and not be terminated by a NUL.

If you simply want to know if the scalar value is TRUE, you can use:

SvTRUE(SV*)

Although Perl will automatically grow strings for you, if you need to force Perl to allocate more memory for your SV, you can use the macro

SvGROW(SV*, STRLEN newlen)

which will determine if more memory needs to be allocated. If so, it will call the function sv_grow . Note that SvGROW can only increase, not decrease, the allocated memory of an SV.

If you have an SV and want to know what kind of data Perl thinks is stored in it, you can use the following macros to check the type of SV you have.

SvIOK(SV*) SvNOK(SV*) SvPOK(SV*)

You can get and set the current length of the string stored in an SV with the following macros:

SvCUR(SV*) SvCUR_set(SV*, I32 val)

You can also get a pointer to the end of the string stored in the SV with the macro:

SvEND(SV*)

But note that these last three macros are valid only if SvPOK() is true.

If you want to append something to the end of string stored in an SV*, you can use the following functions:

void sv_catpv(SV*, char*); void sv_catpvn(SV*, char*, int); void sv_catsv(SV*, SV*);

The first function calculates the length of the string to be appended by using strlen. In the second, you specify the length of the string yourself. The third function extends the string stored in the first SV with the string stored in the second SV. It also forces the second SV to be interpreted as a string.

If you know the name of a scalar variable, you can get a pointer to its SV by using the following:

SV* perl_get_sv("varname", FALSE);

This returns NULL if the variable does not exist.

If you want to know if this variable (or any other SV) is actually defined, you can call:

SvOK(SV*)

The scalar undef value is stored in an SV instance called sv_undef . Its address can be used whenever an SV* is needed.

There are also the two values sv_yes and sv_no , which contain Boolean TRUE and FALSE values, respectively. Like sv_undef , their addresses can be used whenever an SV* is needed.

Do not be fooled into thinking that (SV *) 0 is the same as &sv_undef. Take this code:

SV* sv = (SV*) 0; if (I-am-to-return-a-real-value) { sv = sv_2mortal(newSViv(42)); } sv_setsv(ST(0), sv);

This code tries to return a new SV (which contains the value 42) if it should return a real value, or undef otherwise. Instead it has returned a null pointer which, somewhere down the line, will cause a segmentation violation, or just weird results. Change the zero to &sv_undef in the first line and all will be well.

To free an SV that you've created, call SvREFCNT_dec(SV*) . Normally this call is not necessary. See the section on MORTALITY.

What's Really Stored in an SV?

Recall that the usual method of determining the type of scalar you have is to use Sv*OK macros. Since a scalar can be both a number and a string, usually these macros will always return TRUE and calling the Sv*V macros will do the appropriate conversion of string to integer/double or integer/double to string.

If you really need to know if you have an integer, double, or string pointer in an SV, you can use the following three macros instead:

SvIOKp(SV*) SvNOKp(SV*) SvPOKp(SV*)

These will tell you if you truly have an integer, double, or string pointer stored in your SV. The ``p'' stands for private.

In general, though, it's best to just use the Sv*V macros.

Working with AVs

There are two ways to create and load an AV. The first method just creates an empty AV:

AV* newAV();

The second method both creates the AV and initially populates it with SVs:

AV* av_make(I32 num, SV **ptr);

The second argument points to an array containing num SV*s. Once the AV has been created, the SVs can be destroyed, if so desired.

Once the AV has been created, the following operations are possible on AVs:

void av_push(AV*, SV*); SV* av_pop(AV*); SV* av_shift(AV*); void av_unshift(AV*, I32 num);

These should be familiar operations, with the exception of av_unshift . This routine adds num elements at the front of the array with the undef value. You must then use av_store (described below) to assign values to these new elements.

Here are some other functions:

I32 av_len(AV*); /* Returns highest index value in array */ SV** av_fetch(AV*, I32 key, I32 lval); /* Fetches value at key offset, but it stores an undef value at the offset if lval is non-zero */ SV** av_store(AV*, I32 key, SV* val); /* Stores val at offset key */

Take note that av_fetch and av_store return SV**s, not SV*s.

void av_clear(AV*); /* Clear out all elements, but leave the array */ void av_undef(AV*); /* Undefines the array, removing all elements */ void av_extend(AV*, I32 key); /* Extend the array to a total of key elements */

If you know the name of an array variable, you can get a pointer to its AV by using the following:

AV* perl_get_av("varname", FALSE);

This returns NULL if the variable does not exist.

Working with HVs

To create an HV, you use the following routine:

HV* newHV();

Once the HV has been created, the following operations are possible on HVs:

SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash); SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);

The klen parameter is the length of the key being passed in. The val argument contains the SV pointer to the scalar being stored, and hash is the pre-computed hash value (zero if you want hv_store to calculate it for you). The lval parameter indicates whether this fetch is actually a part of a store operation.

Remember that hv_store and hv_fetch return SV**s and not just SV*. In order to access the scalar value, you must first dereference the return value. However, you should check to make sure that the return value is not NULL before dereferencing it.

These two functions check if a hash table entry exists, and deletes it.

bool hv_exists(HV*, char* key, U32 klen); SV* hv_delete(HV*, char* key, U32 klen, I32 flags);

And more miscellaneous functions:

void hv_clear(HV*); /* Clears all entries in hash table */ void hv_undef(HV*); /* Undefines the hash table */

Perl keeps the actual data in linked list of structures with a typedef of HE. These contain the actual key and value pointers (plus extra administrative overhead). The key is a string pointer; the value is an SV*. However, once you have an HE*, to get the actual key and value, use the routines specified below.

I32 hv_iterinit(HV*); /* Prepares starting point to traverse hash table */ HE* hv_iternext(HV*); /* Get the next entry, and return a pointer to a structure that has both the key and value */ char* hv_iterkey(HE* entry, I32* retlen); /* Get the key from an HE structure and also return the length of the key string */ SV* hv_iterval(HV*, HE* entry); /* Return a SV pointer to the value of the HE structure */ SV* hv_iternextsv(HV*, char** key, I32* retlen); /* This convenience routine combines hv_iternext, hv_iterkey, and hv_iterval. The key and retlen arguments are return values for the key and its length. The value is returned in the SV* argument */

If you know the name of a hash variable, you can get a pointer to its HV by using the following:

HV* perl_get_hv("varname", FALSE);

This returns NULL if the variable does not exist.

The hash algorithm, for those who are interested, is:

i = klen; hash = 0; s = key; while (i--) hash = hash * 33 + *s++;

References

References are a special type of scalar that point to other data types (including references).

To create a reference, use the following command:

SV* newRV((SV*) thing);

The thing argument can be any of an SV*, AV*, or HV*. Once you have a reference, you can use the following macro to dereference the reference:

SvRV(SV*)

then call the appropriate routines, casting the returned SV* to either an AV* or HV*, if required.

To determine if an SV is a reference, you can use the following macro:

SvROK(SV*)

To actually discover what the reference refers to, you must use the following macro and then check the value returned.

SvTYPE(SvRV(SV*))

The most useful types that will be returned are:

SVt_IV Scalar SVt_NV Scalar SVt_PV Scalar SVt_PVAV Array SVt_PVHV Hash SVt_PVCV Code SVt_PVMG Blessed Scalar

Blessed References and Class Objects

References are also used to support object-oriented programming. In the OO lexicon, an object is simply a reference that has been blessed into a package (or class). Once blessed, the programmer may now use the reference to access the various methods in the class.

A reference can be blessed into a package with the following function:

SV* sv_bless(SV* sv, HV* stash);

The sv argument must be a reference. The stash argument specifies which class the reference will belong to. See the ``Stashes'' for information on converting class names into stashes.

/* Still under construction */

Upgrades rv to reference if not already one. Creates new SV for rv to point to. If classname is non-null, the SV is blessed into the specified class. SV is returned.

SV* newSVrv(SV* rv, char* classname);

Copies integer or double into an SV whose reference is rv. SV is blessed if classname is non-null.

SV* sv_setref_iv(SV* rv, char* classname, IV iv); SV* sv_setref_nv(SV* rv, char* classname, NV iv);

Copies pointer (not a string!) into an SV whose reference is rv. SV is blessed if classname is non-null.

SV* sv_setref_pv(SV* rv, char* classname, PV iv);

Copies string into an SV whose reference is rv. Set length to 0 to let Perl calculate the string length. SV is blessed if classname is non-null.

SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length); int sv_isa(SV* sv, char* name); int sv_isobject(SV* sv);


Creating New Variables

To create a new Perl variable, which can be accessed from your Perl script, use the following routines, depending on the variable type.

SV* perl_get_sv("varname", TRUE); AV* perl_get_av("varname", TRUE); HV* perl_get_hv("varname", TRUE);

Notice the use of TRUE as the second parameter. The new variable can now be set, using the routines appropriate to the data type.

There are additional bits that may be OR'ed with the TRUE argument to enable certain extra features. Those bits are:

0x02 Marks the variable as multiply defined, thus preventing the "Identifier <varname> used only once: possible typo" warning. 0x04 Issues a "Had to create <varname> unexpectedly" warning if the variable didn't actually exist. This is useful if you expected the variable to already exist and want to propagate this warning back to the user.

If the varname argument does not contain a package specifier, it is created in the current package.


XSUBs and the Argument Stack

The XSUB mechanism is a simple way for Perl programs to access C subroutines. An XSUB routine will have a stack that contains the arguments from the Perl program, and a way to map from the Perl data structures to a C equivalent.

The stack arguments are accessible through the ST(n) macro, which returns the n'th stack argument. Argument 0 is the first argument passed in the Perl subroutine call. These arguments are SV*, and can be used anywhere an SV* is used.

Most of the time, output from the C routine can be handled through use of the RETVAL and OUTPUT directives. However, there are some cases where the argument stack is not already long enough to handle all the return values. An example is the POSIX tzname() call, which takes no arguments, but returns two, the local timezone's standard and summer time abbreviations.

To handle this situation, the PPCODE directive is used and the stack is extended using the macro:

EXTEND(sp, num);

where sp is the stack pointer, and num is the number of elements the stack should be extended by.

Now that there is room on the stack, values can be pushed on it using the macros to push IVs, doubles, strings, and SV pointers respectively:

PUSHi(IV) PUSHn(double) PUSHp(char*, I32) PUSHs(SV*)

And now the Perl program calling tzname, the two values will be assigned as in:

($standard_abbrev, $summer_abbrev) = POSIX::tzname;

An alternate (and possibly simpler) method to pushing values on the stack is to use the macros:

XPUSHi(IV) XPUSHn(double) XPUSHp(char*, I32) XPUSHs(SV*)

These macros automatically adjust the stack for you, if needed.

For more information, consult the perlxs manpage .


Mortality

In Perl, values are normally ``immortal'' -- that is, they are not freed unless explicitly done so (via the Perl undef call or other routines in Perl itself).

Add cruft about reference counts. int SvREFCNT(SV* sv); void SvREFCNT_inc(SV* sv); void SvREFCNT_dec(SV* sv);

In the above example with tzname, we needed to create two new SVs to push onto the argument stack, that being the two strings. However, we don't want these new SVs to stick around forever because they will eventually be copied into the SVs that hold the two scalar variables.

An SV (or AV or HV) that is ``mortal'' acts in all ways as a normal ``immortal'' SV, AV, or HV, but is only valid in the ``current context''. When the Perl interpreter leaves the current context, the mortal SV, AV, or HV is automatically freed. Generally the ``current context'' means a single Perl statement.

To create a mortal variable, use the functions:

SV* sv_newmortal() SV* sv_2mortal(SV*) SV* sv_mortalcopy(SV*)

The first call creates a mortal SV, the second converts an existing SV to a mortal SV, the third creates a mortal copy of an existing SV.

The mortal routines are not just for SVs -- AVs and HVs can be made mortal by passing their address (and casting them to SV*) to the sv_2mortal or sv_mortalcopy routines.

From Ilya: Beware that the sv_2mortal() call is eventually equivalent to svREFCNT_dec(). A value can happily be mortal in two different contexts, and it will be svREFCNT_dec()ed twice, once on exit from these contexts. It can also be mortal twice in the same context. This means that you should be very careful to make a value mortal exactly as many times as it is needed. The value that go to the Perl stack should be mortal.

You should be careful about creating mortal variables. It is possible for strange things to happen should you make the same value mortal within multiple contexts.


Stashes

A stash is a hash table (associative array) that contains all of the different objects that are contained within a package. Each key of the stash is a symbol name (shared by all the different types of objects that have the same name), and each value in the hash table is called a GV (for Glob Value). This GV in turn contains references to the various objects of that name, including (but not limited to) the following:

Scalar Value Array Value Hash Value File Handle Directory Handle Format Subroutine

Perl stores various stashes in a separate GV structure (for global variable) but represents them with an HV structure. The keys in this larger GV are the various package names; the values are the GV*s which are stashes. It may help to think of a stash purely as an HV, and that the term ``GV'' means the global variable hash.

To get the stash pointer for a particular package, use the function:

HV* gv_stashpv(char* name, I32 create) HV* gv_stashsv(SV*, I32 create)

The first function takes a literal string, the second uses the string stored in the SV. Remember that a stash is just a hash table, so you get back an HV*. The create flag will create a new package if it is set.

The name that gv_stash*v wants is the name of the package whose symbol table you want. The default package is called main. If you have multiply nested packages, pass their names to gv_stash*v, separated by :: as in the Perl language itself.

Alternately, if you have an SV that is a blessed reference, you can find out the stash pointer by using:

HV* SvSTASH(SvRV(SV*));

then use the following to get the package name itself:

char* HvNAME(HV* stash);

If you need to return a blessed value to your Perl script, you can use the following function:

SV* sv_bless(SV*, HV* stash)

where the first argument, an SV*, must be a reference, and the second argument is a stash. The returned SV* can now be used in the same way as any other SV.

For more information on references and blessings, consult the perlref manpage .


Magic

[This section still under construction. Ignore everything here. Post no bills. Everything not permitted is forbidden.]

Any SV may be magical, that is, it has special features that a normal SV does not have. These features are stored in the SV structure in a linked list of struct magics, typedef'ed to MAGIC.

struct magic { MAGIC* mg_moremagic; MGVTBL* mg_virtual; U16 mg_private; char mg_type; U8 mg_flags; SV* mg_obj; char* mg_ptr; I32 mg_len; };

Note this is current as of patchlevel 0, and could change at any time.

Assigning Magic

Perl adds magic to an SV using the sv_magic function:

void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);

The sv argument is a pointer to the SV that is to acquire a new magical feature.

If sv is not already magical, Perl uses the SvUPGRADE macro to set the SVt_PVMG flag for the sv. Perl then continues by adding it to the beginning of the linked list of magical features. Any prior entry of the same type of magic is deleted. Note that this can be overridden, and multiple instances of the same type of magic can be associated with an SV.

The name and namlem arguments are used to associate a string with the magic, typically the name of a variable. namlem is stored in the mg_len field and if name is non-null and namlem >= 0 a malloc'd copy of the name is stored in mg_ptr field.

The sv_magic function uses how to determine which, if any, predefined ``Magic Virtual Table'' should be assigned to the mg_virtual field. See the ``Magic Virtual Table'' section below. The how argument is also stored in the mg_type field.

The obj argument is stored in the mg_obj field of the MAGIC structure. If it is not the same as the sv argument, the reference count of the obj object is incremented. If it is the same, or if the how argument is ``#'', or if it is a null pointer, then obj is merely stored, without the reference count being incremented.

There is also a function to add magic to an HV:

void hv_magic(HV *hv, GV *gv, int how);

This simply calls sv_magic and coerces the gv argument into an SV.

To remove the magic from an SV, call the function sv_unmagic:

void sv_unmagic(SV *sv, int type);

The type argument should be equal to the how value when the SV was initially made magical.

Magic Virtual Tables

The mg_virtual field in the MAGIC structure is a pointer to a MGVTBL, which is a structure of function pointers and stands for ``Magic Virtual Table'' to handle the various operations that might be applied to that variable.

The MGVTBL has five pointers to the following routine types:

int (*svt_get)(SV* sv, MAGIC* mg); int (*svt_set)(SV* sv, MAGIC* mg); U32 (*svt_len)(SV* sv, MAGIC* mg); int (*svt_clear)(SV* sv, MAGIC* mg); int (*svt_free)(SV* sv, MAGIC* mg);

This MGVTBL structure is set at compile-time in perl.h and there are currently 19 types (or 21 with overloading turned on). These different structures contain pointers to various routines that perform additional actions depending on which function is being called.

Function pointer Action taken ---------------- ------------ svt_get Do something after the value of the SV is retrieved. svt_set Do something after the SV is assigned a value. svt_len Report on the SV's length. svt_clear Clear something the SV represents. svt_free Free any extra storage associated with the SV.

For instance, the MGVTBL structure called vtbl_sv (which corresponds to an mg_type of '\0') contains:

{ magic_get, magic_set, magic_len, 0, 0 }

Thus, when an SV is determined to be magical and of type '\0', if a get operation is being performed, the routine magic_get is called. All the various routines for the various magical types begin with magic_.

The current kinds of Magic Virtual Tables are:

mg_type MGVTBL Type of magicalness ------- ------ ------------------- \0 vtbl_sv Regexp??? A vtbl_amagic Operator Overloading a vtbl_amagicelem Operator Overloading c 0 Used in Operator Overloading B vtbl_bm Boyer-Moore??? E vtbl_env %ENV hash e vtbl_envelem %ENV hash element g vtbl_mglob Regexp /g flag??? I vtbl_isa @ISA array i vtbl_isaelem @ISA array element L 0 (but sets RMAGICAL) Perl Module/Debugger??? l vtbl_dbline Debugger? P vtbl_pack Tied Array or Hash p vtbl_packelem Tied Array or Hash element q vtbl_packelem Tied Scalar or Handle S vtbl_sig Signal Hash s vtbl_sigelem Signal Hash element t vtbl_taint Taintedness U vtbl_uvar ??? v vtbl_vec Vector x vtbl_substr Substring??? * vtbl_glob GV??? # vtbl_arylen Array Length . vtbl_pos $. scalar variable ~ Reserved for extensions, but multiple extensions may clash

When an upper-case and lower-case letter both exist in the table, then the upper-case letter is used to represent some kind of composite type (a list or a hash), and the lower-case letter is used to represent an element of that composite type.

Finding Magic

MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */

This routine returns a pointer to the MAGIC structure stored in the SV. If the SV does not have that magical feature, NULL is returned. Also, if the SV is not of type SVt_PVMG, Perl may core-dump.

int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);

This routine checks to see what types of magic sv has. If the mg_type field is an upper-case letter, then the mg_obj is copied to nsv, but the mg_type field is changed to be the lower-case letter.


Double-Typed SVs

Scalar variables normally contain only one type of value, an integer, double, pointer, or reference. Perl will automatically convert the actual scalar data from the stored type into the requested type.

Some scalar variables contain more than one type of scalar data. For example, the variable $! contains either the numeric value of errno or its string equivalent from either strerror or sys_errlist[].

To force multiple data values into an SV, you must do two things: use the sv_set*v routines to add the additional scalar type, then set a flag so that Perl will believe it contains more than one type of data. The four macros to set the flags are:

SvIOK_on SvNOK_on SvPOK_on SvROK_on

The particular macro you must use depends on which sv_set*v routine you called first. This is because every sv_set*v routine turns on only the bit for the particular type of data being set, and turns off all the rest.

For example, to create a new Perl variable called ``dberror'' that contains both the numeric and descriptive string error values, you could use the following code:

extern int dberror; extern char *dberror_list; SV* sv = perl_get_sv("dberror", TRUE); sv_setiv(sv, (IV) dberror); sv_setpv(sv, dberror_list[dberror]); SvIOK_on(sv);

If the order of sv_setiv and sv_setpv had been reversed, then the macro SvPOK_on would need to be called instead of SvIOK_on .


Calling Perl Routines from within C Programs

There are four routines that can be used to call a Perl subroutine from within a C program. These four are:

I32 perl_call_sv(SV*, I32); I32 perl_call_pv(char*, I32); I32 perl_call_method(char*, I32); I32 perl_call_argv(char*, I32, register char**);

The routine most often used is perl_call_sv . The SV* argument contains either the name of the Perl subroutine to be called, or a reference to the subroutine. The second argument consists of flags that control the context in which the subroutine is called, whether or not the subroutine is being passed arguments, how errors should be trapped, and how to treat return values.

All four routines return the number of arguments that the subroutine returned on the Perl stack.

When using any of these routines (except perl_call_argv ), the programmer must manipulate the Perl stack. These include the following macros and functions:

dSP PUSHMARK() PUTBACK SPAGAIN ENTER SAVETMPS FREETMPS LEAVE XPUSH*() POP*()

For more information, consult the perlcall manpage .


Memory Allocation

It is strongly suggested that you use the version of malloc that is distributed with Perl. It keeps pools of various sizes of unallocated memory in order to more quickly satisfy allocation requests. However, on some platforms, it may cause spurious malloc or free errors.

New(x, pointer, number, type); Newc(x, pointer, number, type, cast); Newz(x, pointer, number, type);

These three macros are used to initially allocate memory. The first argument x was a ``magic cookie'' that was used to keep track of who called the macro, to help when debugging memory problems. However, the current code makes no use of this feature (Larry has switched to using a run-time memory checker), so this argument can be any number.

The second argument pointer will point to the newly allocated memory. The third and fourth arguments number and type specify how many of the specified type of data structure should be allocated. The argument type is passed to sizeof. The final argument to Newc , cast, should be used if the pointer argument is different from the type argument.

Unlike the New and Newc macros, the Newz macro calls memzero to zero out all the newly allocated memory.

Renew(pointer, number, type); Renewc(pointer, number, type, cast); Safefree(pointer)

These three macros are used to change a memory buffer size or to free a piece of memory no longer needed. The arguments to Renew and Renewc match those of New and Newc with the exception of not needing the ``magic cookie'' argument.

Move(source, dest, number, type); Copy(source, dest, number, type); Zero(dest, number, type);

These three macros are used to move, copy, or zero out previously allocated memory. The source and dest arguments point to the source and destination starting points. Perl will move, copy, or zero out number instances of the size of the type data structure (using the sizeof function).


API LISTING

This is a listing of functions, macros, flags, and variables that may be useful to extension writers or that may be found while reading other extensions.

AvFILL
See av_len .

av_clear
Clears an array, making it empty.

av_extend
Pre-extend an array. The key is the index to which the array should be extended.

av_fetch
Returns the SV at the specified index in the array. The key is the index. If lval is set then the fetch will be part of a store. Check that the return value is non-null before dereferencing it to a SV*.

SV** av_fetch _((AV* ar, I32 key, I32 lval));

av_len
Returns the highest index in the array. Returns -1 if the array is empty.

av_make
Creates a new AV and populates it with a list of SVs. The SVs are copied into the array, so they may be freed after the call to av_make. The new AV will have a refcount of 1.

AV* av_make _((I32 size, SV** svp));

av_pop
Pops an SV off the end of the array. Returns &sv_undef if the array is empty.

SV* av_pop _((AV* ar));

av_push
Pushes an SV onto the end of the array. The array will grow automatically to accommodate the addition.

av_shift
Shifts an SV off the beginning of the array.

SV* av_shift _((AV* ar));

av_store
Stores an SV in an array. The array index is specified as key. The return value will be null if the operation failed, otherwise it can be dereferenced to get the original SV*.

SV** av_store _((AV* ar, I32 key, SV* val));

av_undef
Undefines the array.

av_unshift
Unshift an SV onto the beginning of the array. The array will grow automatically to accommodate the addition.

CLASS
Variable which is setup by xsubpp to indicate the class name for a C++ XS constructor. This is always a char*. See THIS and ``Using XS With C++''.

Copy
The XSUB-writer's interface to the C memcpy function. The s is the source, d is the destination, n is the number of items, and t is the type.

(void) Copy( s, d, n, t );

croak
This is the XSUB-writer's interface to Perl's die function. Use this function the same way you use the C printf function. See warn .

CvSTASH
Returns the stash of the CV.

HV * CvSTASH( SV* sv )

DBsingle
When Perl is run in debugging mode, with the -d switch, this SV is a boolean which indicates whether subs are being single-stepped. Single-stepping is automatically turned on after every step. This is the C variable which corresponds to Perl's $DB::single variable. See DBsub .

DBsub
When Perl is run in debugging mode, with the -d switch, this GV contains the SV which holds the name of the sub being debugged. This is the C variable which corresponds to Perl's $DB::sub variable. See DBsingle . The sub name can be found by

SvPV( GvSV( DBsub ), na )

DBtrace
Trace variable used when Perl is run in debugging mode, with the -d switch. This is the C variable which corresponds to Perl's $DB::trace variable. See DBsingle .

dMARK
Declare a stack marker variable, mark, for the XSUB. See MARK and dORIGMARK .

dORIGMARK
Saves the original stack mark for the XSUB. See ORIGMARK .

dowarn
The C variable which corresponds to Perl's $^W warning variable.

dSP
Declares a stack pointer variable, sp, for the XSUB. See SP .

dXSARGS
Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is usually handled automatically by xsubpp. Declares the items variable to indicate the number of items on the stack.

dXSI32
Sets up the ix variable for an XSUB which has aliases. This is usually handled automatically by xsubpp.

dXSI32
Sets up the ix variable for an XSUB which has aliases. This is usually handled automatically by xsubpp.

ENTER
Opening bracket on a callback. See LEAVE and the perlcall manpage .

ENTER;

EXTEND
Used to extend the argument stack for an XSUB's return values.

EXTEND( sp, int x );

FREETMPS
Closing bracket for temporaries on a callback. See SAVETMPS and the perlcall manpage .

FREETMPS;

G_ARRAY
Used to indicate array context. See GIMME and the perlcall manpage .

G_DISCARD
Indicates that arguments returned from a callback should be discarded. See the perlcall manpage .

G_EVAL
Used to force a Perl eval wrapper around a callback. See the perlcall manpage .

GIMME
The XSUB-writer's equivalent to Perl's wantarray. Returns G_SCALAR or G_ARRAY for scalar or array context.

G_NOARGS
Indicates that no arguments are being sent to a callback. See the perlcall manpage .

G_SCALAR
Used to indicate scalar context. See GIMME and the perlcall manpage .

gv_stashpv
Returns a pointer to the stash for a specified package. If create is set then the package will be created if it does not already exist. If create is not set and the package does not exist then NULL is returned.

HV* gv_stashpv _((char* name, I32 create));

gv_stashsv
Returns a pointer to the stash for a specified package. See gv_stashpv .

HV* gv_stashsv _((SV* sv, I32 create));

GvSV
Return the SV from the GV.

he_free
Releases a hash entry from an iterator. See hv_iternext .

hv_clear
Clears a hash, making it empty.

hv_delete
Deletes a key/value pair in the hash. The value SV is removed from the hash and returned to the caller. The klen is the length of the key. The flags value will normally be zero; if set to G_DISCARD then null will be returned.

SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));

hv_exists
Returns a boolean indicating whether the specified hash key exists. The klen is the length of the key.

hv_fetch
Returns the SV which corresponds to the specified key in the hash. The klen is the length of the key. If lval is set then the fetch will be part of a store. Check that the return value is non-null before dereferencing it to a SV*.

SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));

hv_iterinit
Prepares a starting point to traverse a hash table.

hv_iterkey
Returns the key from the current position of the hash iterator. See hv_iterinit .

char* hv_iterkey _((HE* entry, I32* retlen));

hv_iternext
Returns entries from a hash iterator. See hv_iterinit .

HE* hv_iternext _((HV* tb));

hv_iternextsv
Performs an hv_iternext , hv_iterkey , and hv_iterval in one operation.

SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));

hv_iterval
Returns the value from the current position of the hash iterator. See hv_iterkey .

SV* hv_iterval _((HV* tb, HE* entry));

hv_magic
Adds magic to a hash. See sv_magic .

HvNAME
Returns the package name of a stash. See SvSTASH , CvSTASH .

char *HvNAME (HV* stash)

hv_store
Stores an SV in a hash. The hash key is specified as key and klen is the length of the key. The hash parameter is the pre-computed hash value; if it is zero then Perl will compute it. The return value will be null if the operation failed, otherwise it can be dereferenced to get the original SV*.

SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));

hv_undef
Undefines the hash.

isALNUM
Returns a boolean indicating whether the C char is an ascii alphanumeric character.

int isALNUM (char c)

isALPHA
Returns a boolean indicating whether the C char is an ascii alphabetic character.

int isALPHA (char c)

isDIGIT
Returns a boolean indicating whether the C char is an ascii digit.

int isDIGIT (char c)

isLOWER
Returns a boolean indicating whether the C char is a lowercase character.

int isLOWER (char c)

isSPACE
Returns a boolean indicating whether the C char is whitespace.

int isSPACE (char c)

isUPPER
Returns a boolean indicating whether the C char is an uppercase character.

int isUPPER (char c)

items
Variable which is setup by xsubpp to indicate the number of items on the stack. See ``Variable-length Parameter Lists''.

ix
Variable which is setup by xsubpp to indicate which of an XSUB's aliases was used to invoke it. See ``The ALIAS: Keyword''.

LEAVE
Closing bracket on a callback. See ENTER and the perlcall manpage .

LEAVE;

MARK
Stack marker variable for the XSUB. See dMARK .

mg_clear
Clear something magical that the SV represents. See sv_magic .

mg_copy
Copies the magic from one SV to another. See sv_magic .

mg_find
Finds the magic pointer for type matching the SV. See sv_magic .

MAGIC* mg_find _((SV* sv, int type));

mg_free
Free any magic storage used by the SV. See sv_magic .

mg_get
Do magic after a value is retrieved from the SV. See sv_magic .

mg_len
Report on the SV's length. See sv_magic .

mg_magical
Turns on the magical status of an SV. See sv_magic .

mg_set
Do magic after a value is assigned to the SV. See sv_magic .

Move
The XSUB-writer's interface to the C memmove function. The s is the source, d is the destination, n is the number of items, and t is the type.

(void) Move( s, d, n, t );

na
A variable which may be used with SvPV to tell Perl to calculate the string length.

New
The XSUB-writer's interface to the C malloc function.

void * New( x, void *ptr, int size, type )

Newc
The XSUB-writer's interface to the C malloc function, with cast.

void * Newc( x, void *ptr, int size, type, cast )

Newz
The XSUB-writer's interface to the C malloc function. The allocated memory is zeroed with memzero.

void * Newz( x, void *ptr, int size, type )

newAV
Creates a new AV. The refcount is set to 1.

AV* newAV _((void));

newHV
Creates a new HV. The refcount is set to 1.

HV* newHV _((void));

newRV
Creates an RV wrapper for an SV. The refcount for the original SV is incremented.

SV* newRV _((SV* ref));

newSV
Creates a new SV. The len parameter indicates the number of bytes of pre-allocated string space the SV should have. The refcount for the new SV is set to 1.

SV* newSV _((STRLEN len));

newSViv
Creates a new SV and copies an integer into it. The refcount for the SV is set to 1.

SV* newSViv _((IV i));

newSVnv
Creates a new SV and copies a double into it. The refcount for the SV is set to 1.

SV* newSVnv _((NV i));

newSVpv
Creates a new SV and copies a string into it. The refcount for the SV is set to 1. If len is zero then Perl will compute the length.

SV* newSVpv _((char* s, STRLEN len));

newSVrv
Creates a new SV for the RV, rv, to point to. If rv is not an RV then it will be upgraded to one. If classname is non-null then the new SV will be blessed in the specified package. The new SV is returned and its refcount is 1.

SV* newSVrv _((SV* rv, char* classname));

newSVsv
Creates a new SV which is an exact duplicate of the original SV.

SV* newSVsv _((SV* old));

newXS
Used by xsubpp to hook up XSUBs as Perl subs.

newXSproto
Used by xsubpp to hook up XSUBs as Perl subs. Adds Perl prototypes to the subs.

Nullav
Null AV pointer.

Nullch
Null character pointer.

Nullcv
Null CV pointer.

Nullhv
Null HV pointer.

Nullsv
Null SV pointer.

ORIGMARK
The original stack mark for the XSUB. See dORIGMARK .

perl_alloc
Allocates a new Perl interpreter. See the perlembed manpage .

perl_call_argv
Performs a callback to the specified Perl sub. See the perlcall manpage .

perl_call_method
Performs a callback to the specified Perl method. The blessed object must be on the stack. See the perlcall manpage .

perl_call_pv
Performs a callback to the specified Perl sub. See the perlcall manpage .

perl_call_sv
Performs a callback to the Perl sub whose name is in the SV. See the perlcall manpage .

perl_construct
Initializes a new Perl interpreter. See the perlembed manpage .

perl_destruct
Shuts down a Perl interpreter. See the perlembed manpage .

perl_eval_sv
Tells Perl to eval the string in the SV.

perl_free
Releases a Perl interpreter. See the perlembed manpage .

perl_get_av
Returns the AV of the specified Perl array. If create is set and the Perl variable does not exist then it will be created. If create is not set and the variable does not exist then null is returned.

AV* perl_get_av _((char* name, I32 create));

perl_get_cv
Returns the CV of the specified Perl sub. If create is set and the Perl variable does not exist then it will be created. If create is not set and the variable does not exist then null is returned.

CV* perl_get_cv _((char* name, I32 create));

perl_get_hv
Returns the HV of the specified Perl hash. If create is set and the Perl variable does not exist then it will be created. If create is not set and the variable does not exist then null is returned.

HV* perl_get_hv _((char* name, I32 create));

perl_get_sv
Returns the SV of the specified Perl scalar. If create is set and the Perl variable does not exist then it will be created. If create is not set and the variable does not exist then null is returned.

SV* perl_get_sv _((char* name, I32 create));

perl_parse
Tells a Perl interpreter to parse a Perl script. See the perlembed manpage .

perl_require_pv
Tells Perl to require a module.

perl_run
Tells a Perl interpreter to run. See the perlembed manpage .

POPi
Pops an integer off the stack.

int POPi();

POPl
Pops a long off the stack.

long POPl();

POPp
Pops a string off the stack.

char * POPp();

POPn
Pops a double off the stack.

double POPn();

POPs
Pops an SV off the stack.

SV* POPs();

PUSHMARK
Opening bracket for arguments on a callback. See PUTBACK and the perlcall manpage .

PUSHMARK(p)

PUSHi
Push an integer onto the stack. The stack must have room for this element. See XPUSHi .

PUSHi(int d)

PUSHn
Push a double onto the stack. The stack must have room for this element. See XPUSHn .

PUSHn(double d)

PUSHp
Push a string onto the stack. The stack must have room for this element. The len indicates the length of the string. See XPUSHp .

PUSHp(char *c, int len )

PUSHs
Push an SV onto the stack. The stack must have room for this element. See XPUSHs .

PUSHs(sv)

PUTBACK
Closing bracket for XSUB arguments. This is usually handled by xsubpp. See PUSHMARK and the perlcall manpage for other uses.

PUTBACK;

Renew
The XSUB-writer's interface to the C realloc function.

void * Renew( void *ptr, int size, type )

Renewc
The XSUB-writer's interface to the C realloc function, with cast.

void * Renewc( void *ptr, int size, type, cast )

RETVAL
Variable which is setup by xsubpp to hold the return value for an XSUB. This is always the proper type for the XSUB. See ``The RETVAL Variable''.

safefree
The XSUB-writer's interface to the C free function.

safemalloc
The XSUB-writer's interface to the C malloc function.

saferealloc
The XSUB-writer's interface to the C realloc function.

savepv
Copy a string to a safe spot. This does not use an SV.

char* savepv _((char* sv));

savepvn
Copy a string to a safe spot. The len indicates number of bytes to copy. This does not use an SV.

char* savepvn _((char* sv, I32 len));

SAVETMPS
Opening bracket for temporaries on a callback. See FREETMPS and the perlcall manpage .

SAVETMPS;

SP
Stack pointer. This is usually handled by xsubpp. See dSP and SPAGAIN .

SPAGAIN
Refetch the stack pointer. Used after a callback. See the perlcall manpage .

SPAGAIN;

ST
Used to access elements on the XSUB's stack.

SV* ST(int x)

strEQ
Test two strings to see if they are equal. Returns true or false.

int strEQ( char *s1, char *s2 )

strGE
Test two strings to see if the first, s1, is greater than or equal to the second, s2. Returns true or false.

int strGE( char *s1, char *s2 )

strGT
Test two strings to see if the first, s1, is greater than the second, s2. Returns true or false.

int strGT( char *s1, char *s2 )

strLE
Test two strings to see if the first, s1, is less than or equal to the second, s2. Returns true or false.

int strLE( char *s1, char *s2 )

strLT
Test two strings to see if the first, s1, is less than the second, s2. Returns true or false.

int strLT( char *s1, char *s2 )

strNE
Test two strings to see if they are different. Returns true or false.

int strNE( char *s1, char *s2 )

strnEQ
Test two strings to see if they are equal. The len parameter indicates the number of bytes to compare. Returns true or false.

int strnEQ( char *s1, char *s2 )

strnNE
Test two strings to see if they are different. The len parameter indicates the number of bytes to compare. Returns true or false.

int strnNE( char *s1, char *s2, int len )

sv_2mortal
Marks an SV as mortal. The SV will be destroyed when the current context ends.

SV* sv_2mortal _((SV* sv));

sv_bless
Blesses an SV into a specified package. The SV must be an RV. The package must be designated by its stash (see gv_stashpv() ). The refcount of the SV is unaffected.

SV* sv_bless _((SV* sv, HV* stash));

sv_catpv
Concatenates the string onto the end of the string which is in the SV.

sv_catpvn
Concatenates the string onto the end of the string which is in the SV. The len indicates number of bytes to copy.

sv_catsv
Concatenates the string from SV ssv onto the end of the string in SV dsv.

sv_cmp
Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the string in sv1 is less than, equal to, or greater than the string in sv2.

sv_cmp
Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the string in sv1 is less than, equal to, or greater than the string in sv2.

SvCUR
Returns the length of the string which is in the SV. See SvLEN .

int SvCUR (SV* sv)

SvCUR_set
Set the length of the string which is in the SV. See SvCUR .

SvCUR_set (SV* sv, int val )

sv_dec
Autodecrement of the value in the SV.

sv_dec
Autodecrement of the value in the SV.

SvEND
Returns a pointer to the last character in the string which is in the SV. See SvCUR . Access the character as

*SvEND(sv)

sv_eq
Returns a boolean indicating whether the strings in the two SVs are identical.

SvGROW
Expands the character buffer in the SV. Calls sv_grow to perform the expansion if necessary. Returns a pointer to the character buffer.

char * SvGROW( SV* sv, int len )

sv_grow
Expands the character buffer in the SV. This will use sv_unref and will upgrade the SV to SVt_PV . Returns a pointer to the character buffer. Use SvGROW .

sv_inc
Autoincrement of the value in the SV.

SvIOK
Returns a boolean indicating whether the SV contains an integer.

int SvIOK (SV* SV)

SvIOK_off
Unsets the IV status of an SV.

SvIOK_off (SV* sv)

SvIOK_on
Tells an SV that it is an integer.

SvIOK_on (SV* sv)

SvIOK_only
Tells an SV that it is an integer and disables all other OK bits.

SvIOK_on (SV* sv)

SvIOK_only
Tells an SV that it is an integer and disables all other OK bits.

SvIOK_on (SV* sv)

SvIOKp
Returns a boolean indicating whether the SV contains an integer. Checks the private setting. Use SvIOK .

int SvIOKp (SV* SV)

sv_isa
Returns a boolean indicating whether the SV is blessed into the specified class. This does not know how to check for subtype, so it doesn't work in an inheritance relationship.

SvIV
Returns the integer which is in the SV.

int SvIV (SV* sv)

sv_isobject
Returns a boolean indicating whether the SV is an RV pointing to a blessed object. If the SV is not an RV, or if the object is not blessed, then this will return false.

SvIVX
Returns the integer which is stored in the SV.

int SvIVX (SV* sv);

SvLEN
Returns the size of the string buffer in the SV. See SvCUR .

int SvLEN (SV* sv)

sv_len
Returns the length of the string in the SV. Use SvCUR .

sv_len
Returns the length of the string in the SV. Use SvCUR .

sv_magic
Adds magic to an SV.

sv_mortalcopy
Creates a new SV which is a copy of the original SV. The new SV is marked as mortal.

SV* sv_mortalcopy _((SV* oldsv));

SvOK
Returns a boolean indicating whether the value is an SV.

int SvOK (SV* sv)

sv_newmortal
Creates a new SV which is mortal. The refcount of the SV is set to 1.

SV* sv_newmortal _((void));

sv_no
This is the false SV. See sv_yes . Always refer to this as &sv_no.

SvNIOK
Returns a boolean indicating whether the SV contains a number, integer or double.

int SvNIOK (SV* SV)

SvNIOK_off
Unsets the NV/IV status of an SV.

SvNIOK_off (SV* sv)

SvNIOKp
Returns a boolean indicating whether the SV contains a number, integer or double. Checks the private setting. Use SvNIOK .

int SvNIOKp (SV* SV)

SvNOK
Returns a boolean indicating whether the SV contains a double.

int SvNOK (SV* SV)

SvNOK_off
Unsets the NV status of an SV.

SvNOK_off (SV* sv)

SvNOK_on
Tells an SV that it is a double.

SvNOK_on (SV* sv)

SvNOK_only
Tells an SV that it is a double and disables all other OK bits.

SvNOK_on (SV* sv)

SvNOK_only
Tells an SV that it is a double and disables all other OK bits.

SvNOK_on (SV* sv)

SvNOKp
Returns a boolean indicating whether the SV contains a double. Checks the private setting. Use SvNOK .

int SvNOKp (SV* SV)

SvNV
Returns the double which is stored in the SV.

double SvNV (SV* sv);

SvNVX
Returns the double which is stored in the SV.

double SvNVX (SV* sv);

SvPOK
Returns a boolean indicating whether the SV contains a character string.

int SvPOK (SV* SV)

SvPOK_off
Unsets the PV status of an SV.

SvPOK_off (SV* sv)

SvPOK_on
Tells an SV that it is a string.

SvPOK_on (SV* sv)

SvPOK_only
Tells an SV that it is a string and disables all other OK bits.

SvPOK_on (SV* sv)

SvPOK_only
Tells an SV that it is a string and disables all other OK bits.

SvPOK_on (SV* sv)

SvPOKp
Returns a boolean indicating whether the SV contains a character string. Checks the private setting. Use SvPOK .

int SvPOKp (SV* SV)

SvPV
Returns a pointer to the string in the SV, or a stringified form of the SV if the SV does not contain a string. If len is na then Perl will handle the length on its own.

char * SvPV (SV* sv, int len )

SvPVX
Returns a pointer to the string in the SV. The SV must contain a string.

char * SvPVX (SV* sv)

SvREFCNT
Returns the value of the object's refcount.

int SvREFCNT (SV* sv);

SvREFCNT_dec
Decrements the refcount of the given SV.

void SvREFCNT_dec (SV* sv)

SvREFCNT_inc
Increments the refcount of the given SV.

void SvREFCNT_inc (SV* sv)

SvROK
Tests if the SV is an RV.

int SvROK (SV* sv)

SvROK_off
Unsets the RV status of an SV.

SvROK_off (SV* sv)

SvROK_on
Tells an SV that it is an RV.

SvROK_on (SV* sv)

SvRV
Dereferences an RV to return the SV.

SV* SvRV (SV* sv);

sv_setiv
Copies an integer into the given SV.

sv_setnv
Copies a double into the given SV.

sv_setpv
Copies a string into an SV. The string must be null-terminated.

sv_setpvn
Copies a string into an SV. The len parameter indicates the number of bytes to be copied.

sv_setref_iv
Copies an integer into a new SV, optionally blessing the SV. The rv argument will be upgraded to an RV. That RV will be modified to point to the new SV. The classname argument indicates the package for the blessing. Set classname to Nullch to avoid the blessing. The new SV will be returned and will have a refcount of 1.

SV* sv_setref_iv _((SV *rv, char *classname, IV iv));

sv_setref_nv
Copies a double into a new SV, optionally blessing the SV. The rv argument will be upgraded to an RV. That RV will be modified to point to the new SV. The classname argument indicates the package for the blessing. Set classname to Nullch to avoid the blessing. The new SV will be returned and will have a refcount of 1.

SV* sv_setref_nv _((SV *rv, char *classname, double nv));

sv_setref_pv
Copies a pointer into a new SV, optionally blessing the SV. The rv argument will be upgraded to an RV. That RV will be modified to point to the new SV. If the pv argument is NULL then sv_undef will be placed into the SV. The classname argument indicates the package for the blessing. Set classname to Nullch to avoid the blessing. The new SV will be returned and will have a refcount of 1.

SV* sv_setref_pv _((SV *rv, char *classname, void* pv));

Do not use with integral Perl types such as HV, AV, SV, CV, because those objects will become corrupted by the pointer copy process.

Note that sv_setref_pvn copies the string while this copies the pointer.

sv_setref_pvn
Copies a string into a new SV, optionally blessing the SV. The length of the string must be specified with n. The rv argument will be upgraded to an RV. That RV will be modified to point to the new SV. The classname argument indicates the package for the blessing. Set classname to Nullch to avoid the blessing. The new SV will be returned and will have a refcount of 1.

SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));

Note that sv_setref_pv copies the pointer while this copies the string.

sv_setsv
Copies the contents of the source SV ssv into the destination SV dsv. The source SV may be destroyed if it is mortal.

SvSTASH
Returns the stash of the SV.

HV * SvSTASH (SV* sv)

SVt_IV
Integer type flag for scalars. See svtype .

SVt_PV
Pointer type flag for scalars. See svtype .

SVt_PVAV
Type flag for arrays. See svtype .

SVt_PVCV
Type flag for code refs. See svtype .

SVt_PVHV
Type flag for hashes. See svtype .

SVt_PVMG
Type flag for blessed scalars. See svtype .

SVt_NV
Double type flag for scalars. See svtype .

SvTRUE
Returns a boolean indicating whether Perl would evaluate the SV as true or false, defined or undefined.

int SvTRUE (SV* sv)

SvTYPE
Returns the type of the SV. See svtype .

svtype
An enum of flags for Perl types. These are found in the file sv.h in the svtype enum. Test these flags with the SvTYPE macro.

SvUPGRADE
Used to upgrade an SV to a more complex form. Uses sv_upgrade to perform the upgrade if necessary. See svtype .

bool SvUPGRADE _((SV* sv, svtype mt));

sv_upgrade
Upgrade an SV to a more complex form. Use SvUPGRADE . See svtype .

sv_undef
This is the undef SV. Always refer to this as &sv_undef.

sv_unref
Unsets the RV status of the SV, and decrements the refcount of whatever was being referenced by the RV. This can almost be thought of as a reversal of newSVrv . See SvROK_off .

void sv_unref _((SV* sv));

sv_usepvn
Tells an SV to use ptr to find its string value. Normally the string is stored inside the SV but sv_usepvn allows the SV to use an outside string. The ptr should point to memory that was allocated by malloc. The string length, len, must be supplied. This function will realloc the memory pointed to by ptr, so that pointer should not be freed or used by the programmer after giving it to sv_usepvn.

sv_yes
This is the true SV. See sv_no . Always refer to this as &sv_yes.

THIS
Variable which is setup by xsubpp to designate the object in a C++ XSUB. This is always the proper type for the C++ object. See CLASS and ``Using XS With C++''.

toLOWER
Converts the specified character to lowercase.

int toLOWER (char c)

toUPPER
Converts the specified character to uppercase.

int toUPPER (char c)

warn
This is the XSUB-writer's interface to Perl's warn function. Use this function the same way you use the C printf function. See croak() .

XPUSHi
Push an integer onto the stack, extending the stack if necessary. See PUSHi .

XPUSHi(int d)

XPUSHn
Push a double onto the stack, extending the stack if necessary. See PUSHn .

XPUSHn(double d)

XPUSHp
Push a string onto the stack, extending the stack if necessary. The len indicates the length of the string. See PUSHp .

XPUSHp(char *c, int len)

XPUSHs
Push an SV onto the stack, extending the stack if necessary. See PUSHs .

XPUSHs(sv)

XS
Macro to declare an XSUB and its C parameter list. This is handled by xsubpp.

XSRETURN
Return from XSUB, indicating number of items on the stack. This is usually handled by xsubpp.

XSRETURN(int x);

XSRETURN_EMPTY
Return an empty list from an XSUB immediately.

XSRETURN_EMPTY;

XSRETURN_IV
Return an integer from an XSUB immediately. Uses XST_mIV .

XSRETURN_IV(IV v);

XSRETURN_NO
Return &sv_no from an XSUB immediately. Uses XST_mNO .

XSRETURN_NO;

XSRETURN_NV
Return an double from an XSUB immediately. Uses XST_mNV .

XSRETURN_NV(NV v);

XSRETURN_PV
Return a copy of a string from an XSUB immediately. Uses XST_mPV .

XSRETURN_PV(char *v);

XSRETURN_UNDEF
Return &sv_undef from an XSUB immediately. Uses XST_mUNDEF .

XSRETURN_UNDEF;

XSRETURN_YES
Return &sv_yes from an XSUB immediately. Uses XST_mYES .

XSRETURN_YES;

XST_mIV
Place an integer into the specified position i on the stack. The value is stored in a new mortal SV.

XST_mIV( int i, IV v );

XST_mNV
Place a double into the specified position i on the stack. The value is stored in a new mortal SV.

XST_mNV( int i, NV v );

XST_mNO
Place &sv_no into the specified position i on the stack.

XST_mNO( int i );

XST_mPV
Place a copy of a string into the specified position i on the stack. The value is stored in a new mortal SV.

XST_mPV( int i, char *v );

XST_mUNDEF
Place &sv_undef into the specified position i on the stack.

XST_mUNDEF( int i );

XST_mYES
Place &sv_yes into the specified position i on the stack.

XST_mYES( int i );

XS_VERSION
The version identifier for an XS module. This is usually handled automatically by ExtUtils::MakeMaker. See XS_VERSION_BOOTCHECK .

XS_VERSION_BOOTCHECK
Macro to verify that a PM module's $VERSION variable matches the XS module's XS_VERSION variable. This is usually handled automatically by xsubpp. See ``The VERSIONCHECK: Keyword''.

Zero
The XSUB-writer's interface to the C memzero function. The d is the destination, n is the number of items, and t is the type.

(void) Zero( d, n, t );


AUTHOR

Jeff Okamoto <okamoto@corp.hp.com>

With lots of help and suggestions from Dean Roehrich, Malcolm Beattie, Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil Bowers, Matthew Green, Tim Bunce, and Spider Boardman.

API Listing by Dean Roehrich <roehrich@cray.com>.


DATE

Version 22: 1996/9/23