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perl5.003_02a
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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 SV's

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 NUL's 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 AV's

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 SV's:

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 SV's can be destroyed, if so desired.

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

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 HV's

To create an HV, you use the following routine:

HV*  newHV();

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

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 section on 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
	  "Indentifier <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.

XSUB's 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 IV's, 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 perlxs.

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 SV's to push onto the argument stack, that being the two strings. However, we don't want these new SV's to stick around forever because they will eventually be copied into the SV's 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 SV's -- AV's and HV's 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 perlref.

Magic

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

# Version 6, 1995/1/27

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 magic's, 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 overriden, 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 SV's

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 perlcall.

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.

void	av_clear _((AV* ar));
av_extend

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

void	av_extend _((AV* ar, I32 key));
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.

I32	av_len _((AV* ar));
av_make

Creats 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.

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.

void	av_push _((AV* ar, SV* val));
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.

void	av_undef _((AV* ar));
av_unshift

Unshift an SV onto the beginning of the array.

void	av_unshift _((AV* ar, I32 num));
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 perlxs.

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. 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. See DBsingle. The sub name can be found by

SvPV( GvSV( DBsub ), na )
dMARK

Declare a stack marker for the XSUB. See MARK and dORIGMARK.

dORIGMARK

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

dSP

Declares a stack pointer 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.

ENTER

Opening bracket on a callback. See LEAVE and perlcall.

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 perlcall.

FREETMPS;
G_ARRAY

Used to indicate array context. See GIMME and perlcall.

G_DISCARD

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

G_EVAL

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

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 perlcall.

G_SCALAR

Used to indicate scalar context. See GIMME and perlcall.

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.

void	hv_clear _((HV* tb));
hv_delete

Deletes a key/value pair in the hash. The value SV is removed from the hash and returned to the caller. The lken 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 lken is the length of the key.

bool	hv_exists _((HV* tb, char* key, U32 klen));
hv_fetch

Returns the SV which corresponds to the specified key in the hash. The lken 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.

I32	hv_iterinit _((HV* tb));
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.

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

void	hv_undef _((HV* tb));
isALNUM

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

int isALNUM (char c)
isALPHA

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

LEAVE

Closing bracket on a callback. See ENTER and perlcall.

LEAVE;
MARK

Stack marker for the XSUB. See dMARK.

mg_clear

Clear something magical that the SV represents. See sv_magic.

int	mg_clear _((SV* sv));
mg_copy

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

int	mg_copy _((SV *, SV *, char *, STRLEN));
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.

int	mg_free _((SV* sv));
mg_get

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

int	mg_get _((SV* sv));
mg_len

Report on the SV's length. See sv_magic.

U32	mg_len _((SV* sv));
mg_magical

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

void	mg_magical _((SV* sv));
mg_set

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

int	mg_set _((SV* sv));
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 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 orignal 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 perlembed.

perl_call_argv

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

I32	perl_call_argv _((char* subname, I32 flags, char** argv));
perl_call_method

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

I32	perl_call_method _((char* methname, I32 flags));
perl_call_pv

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

I32	perl_call_pv _((char* subname, I32 flags));
perl_call_sv

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

I32	perl_call_sv _((SV* sv, I32 flags));
perl_construct

Initializes a new Perl interpreter. See perlembed.

perl_destruct

Shuts down a Perl interpreter. See perlembed.

perl_eval_sv

Tells Perl to eval the string in the SV.

I32	perl_eval_sv _((SV* sv, I32 flags));
perl_free

Releases a Perl interpreter. See perlembed.

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 perlembed.

perl_require_pv

Tells Perl to require a module.

void	perl_require_pv _((char* pv));
perl_run

Tells a Perl interpreter to run. See perlembed.

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 perlcall.

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 perlcall 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 perlxs.

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 perlcall.

SAVETMPS;
SP

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

SPAGAIN

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

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.

void	sv_catpv _((SV* sv, char* ptr));
sv_catpvn

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

void	sv_catpvn _((SV* sv, char* ptr, STRLEN len));
sv_catsv

Concatentates the string from SV ssv onto the end of the string in SV dsv.

void	sv_catsv _((SV* dsv, SV* ssv));
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 )
SvEND

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

*SvEND(sv)
SvGROW

Expands the character buffer in the SV.

char * SvGROW( SV* sv, int len )
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)
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.

int	sv_isa _((SV* sv, char* name));
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.

int	sv_isobject _((SV* sv));
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_magic

Adds magic to an SV.

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

void	sv_setiv _((SV* sv, IV num));
sv_setnv

Copies a double into the given SV.

void	sv_setnv _((SV* sv, double num));
sv_setpv

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

void	sv_setpv _((SV* sv, char* ptr));
sv_setpvn

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

void	sv_setpvn _((SV* sv, char* ptr, STRLEN len));
sv_setref_iv

Copies an integer into an SV, optionally blessing the SV. The SV must be an RV. 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 an SV, optionally blessing the SV. The SV must be an RV. 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 an SV, optionally blessing the SV. The SV must be an RV. 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 an SV, optionally blessing the SV. The lenth of the string must be specified with n. The SV must be an RV. 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. (NOTE: If ssv has the SVs_TEMP bit set, sv_setsv may simply steal the string from ssv and give it to dsv, leaving ssv empty. Caveat caller.)

void	sv_setsv _((SV* dsv, SV* ssv));
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	SvTYPE (SV* sv)
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. See svtype.

sv_undef

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

sv_usepvn

Tells an SV to use ptr to find its string value. Normally the string is stored inside the SV; this allows the SV to use an outside string. 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.

void	sv_usepvn _((SV* sv, char* ptr, STRLEN len));
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 perlxs.

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)
XSRETURN

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

XSRETURN(x);
XSRETURN_EMPTY

Return from an XSUB immediately.

XSRETURN_EMPTY;
XSRETURN_NO

Return false from an XSUB immediately.

XSRETURN_NO;
XSRETURN_UNDEF

Return undef from an XSUB immediately.

XSRETURN_UNDEF;
XSRETURN_YES

Return true from an XSUB immediately.

XSRETURN_YES;
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 20: 1995/12/14