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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 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 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 the perlref
manpage .
---------------------------------------------------------------------------
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 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.
o void av_clear _((AV* ar));
av_extend
Pre-extend an array. The key is the index to which the array should be
extended.
o 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.
o 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.
o 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.
o void av_undef _((AV* ar));
av_unshift
Unshift an SV onto the beginning of the array.
o 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 the perlxs
manpage .
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 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.
o 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.
o 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.
o 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 .
o 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.
o 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 the perlxs manpage .
LEAVE
Closing bracket on a callback. See ENTER and the perlcall manpage .
LEAVE;
MARK
Stack marker for the XSUB. See dMARK .
mg_clear
Clear something magical that the SV represents. See sv_magic .
o int mg_clear _((SV* sv));
mg_copy
Copies the magic from one SV to another. See sv_magic .
o 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 .
o int mg_free _((SV* sv));
mg_get
Do magic after a value is retrieved from the SV. See sv_magic .
o int mg_get _((SV* sv));
mg_len
Report on the SV's length. See sv_magic .
o U32 mg_len _((SV* sv));
mg_magical
Turns on the magical status of an SV. See sv_magic .
o void mg_magical _((SV* sv));
mg_set
Do magic after a value is assigned to the SV. See sv_magic .
o 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 the perlembed manpage .
perl_call_argv
Performs a callback to the specified Perl sub. See the perlcall
manpage .
o 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 the perlcall manpage .
o I32 perl_call_method _((char* methname, I32 flags));
perl_call_pv
Performs a callback to the specified Perl sub. See the perlcall
manpage .
o 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 the
perlcall manpage .
o I32 perl_call_sv _((SV* sv, I32 flags));
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.
o I32 perl_eval_sv _((SV* sv, I32 flags));
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.
o void perl_require_pv _((char* pv));
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 perlxs
manpage .
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.
o 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.
o 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.
o 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.
o 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.
o 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.
o 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.
o void sv_setiv _((SV* sv, IV num));
sv_setnv
Copies a double into the given SV.
o void sv_setnv _((SV* sv, double num));
sv_setpv
Copies a string into an SV. The string must be null-terminated.
o 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.
o 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.
o 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 .
o 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.
o 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
the perlxs manpage .
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
--------------78468901E1B--
--
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