Perl executable. It is far from complete and probably contains many errors.
Please refer any questions or comments to the author below.
-=head1 Datatypes
+=head1 Variables
+
+=head2 Datatypes
Perl has three typedefs that handle Perl's three main data types:
=head2 What is an "IV"?
-Perl uses a special typedef IV which is large enough to hold either an
-integer or a pointer.
+Perl uses a special typedef IV which is a simple integer type that is
+guaranteed to be large enough to hold a pointer (as well as an integer).
Perl also uses two special typedefs, I32 and I16, which will always be at
least 32-bits and 16-bits long, respectively.
SV* newSVpv(char*, int);
SV* newSVsv(SV*);
-To change the value of an *already-existing* scalar, there are five routines:
+To change the value of an *already-existing* SV, there are five routines:
void sv_setiv(SV*, IV);
void sv_setnv(SV*, double);
Notice that you can choose to specify the length of the string to be
assigned by using C<sv_setpvn> or C<newSVpv>, or you may allow Perl to
-calculate the length by using C<sv_setpv> or specifying 0 as the second
+calculate the length by using C<sv_setpv> or by specifying 0 as the second
argument to C<newSVpv>. Be warned, though, that Perl will determine the
string's length by using C<strlen>, which depends on the string terminating
with a NUL character.
+All SV's that will contain strings should, but need not, be terminated
+with a NUL character. If it is not NUL-terminated there is a risk of
+core dumps and corruptions from code which passes the string to C
+functions or system calls which expect a NUL-terminated string.
+Perl's own functions typically add a trailing NUL for this reason.
+Nevertheless, you should be very careful when you pass a string stored
+in an SV to a C function or system call.
+
To access the actual value that an SV points to, you can use the macros:
SvIV(SV*)
variable C<len> (this is a macro, so you do I<not> use C<&len>). If you do not
care what the length of the data is, use the global variable C<na>. Remember,
however, that Perl allows arbitrary strings of data that may both contain
-NUL's and not be terminated by a NUL.
+NUL's and might not be terminated by a NUL.
-If you simply want to know if the scalar value is TRUE, you can use:
+If you want to know if the scalar value is TRUE, you can use:
SvTRUE(SV*)
which will determine if more memory needs to be allocated. If so, it will
call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
-decrease, the allocated memory of an SV.
+decrease, the allocated memory of an SV and that it does not automatically
+add a byte for the a trailing NUL (perl's own string functions typically do
+C<SvGROW(sv, len + 1)>).
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.
SvCUR(SV*)
SvCUR_set(SV*, I32 val)
-But note that these are valid only if C<SvPOK()> is true.
+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 C<SvPOK()> is true.
If you want to append something to the end of string stored in an C<SV*>,
you can use the following functions:
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);
+ SV* perl_get_sv("package::varname", FALSE);
This returns NULL if the variable does not exist.
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 C<&sv_undef> in the first line and
-all will be well.
+bus error, or just weird results. Change the zero to C<&sv_undef> in the first
+line and all will be well.
To free an SV that you've created, call C<SvREFCNT_dec(SV*)>. Normally this
-call is not necessary. See the section on B<MORTALITY>.
+call is not necessary (see L<Reference Counts and Mortality>).
=head2 What's Really Stored in an SV?
Recall that the usual method of determining the type of scalar you have is
-to use C<Sv*OK> macros. Since a scalar can be both a number and a string,
+to use C<Sv*OK> macros. Because a scalar can be both a number and a string,
usually these macros will always return TRUE and calling the C<Sv*V>
macros will do the appropriate conversion of string to integer/double or
integer/double to string.
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 C<Sv*V> macros.
+In general, though, it's best to use the C<Sv*V> macros.
=head2 Working with AV's
-There are two ways to create and load an AV. The first method just creates
-an empty AV:
+There are two ways to create and load an AV. The first method creates an
+empty AV:
AV* newAV();
Here are some other functions:
- I32 av_len(AV*); /* Returns highest index value in array */
-
+ I32 av_len(AV*);
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 these two functions return C<SV**>'s, not C<SV*>'s.
+The C<av_len> function returns the highest index value in array (just
+like $#array in Perl). If the array is empty, -1 is returned. The
+C<av_fetch> function returns the value at index C<key>, but if C<lval>
+is non-zero, then C<av_fetch> will store an undef value at that index.
+The C<av_store> function stores the value C<val> at index C<key>.
+note that C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s
+as their return value.
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);
+
+The C<av_clear> function deletes all the elements in the AV* array, but
+does not actually delete the array itself. The C<av_undef> function will
+delete all the elements in the array plus the array itself. The
+C<av_extend> function extends the array so that it contains C<key>
+elements. If C<key> is less than the current length of the array, then
+nothing is done.
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);
+ AV* perl_get_av("package::varname", FALSE);
This returns NULL if the variable does not exist.
SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
-The C<klen> parameter is the length of the key being passed in. The C<val>
-argument contains the SV pointer to the scalar being stored, and C<hash> is
-the pre-computed hash value (zero if you want C<hv_store> to calculate it
-for you). The C<lval> parameter indicates whether this fetch is actually a
-part of a store operation.
+The C<klen> parameter is the length of the key being passed in (Note that
+you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
+length of the key). The C<val> argument contains the SV pointer to the
+scalar being stored, and C<hash> is the pre-computed hash value (zero if
+you want C<hv_store> to calculate it for you). The C<lval> parameter
+indicates whether this fetch is actually a part of a store operation, in
+which case a new undefined value will be added to the HV with the supplied
+key and C<hv_fetch> will return as if the value had already existed.
Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
-C<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.
+C<SV*>. 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);
+If C<flags> does not include the C<G_DISCARD> flag then C<hv_delete> will
+create and return a mortal copy of the deleted value.
+
And more miscellaneous functions:
void hv_clear(HV*);
- /* Clears all entries in hash table */
void hv_undef(HV*);
- /* Undefines the hash table */
+
+Like their AV counterparts, C<hv_clear> deletes all the entries in the hash
+table but does not actually delete the hash table. The C<hv_undef> deletes
+both the entries and the hash table itself.
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
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);
+ 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);
+ 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
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);
+ HV* perl_get_hv("package::varname", FALSE);
This returns NULL if the variable does not exist.
-The hash algorithm, for those who are interested, is:
+The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
i = klen;
hash = 0;
while (i--)
hash = hash * 33 + *s++;
-=head1 Creating New Variables
+=head2 Hash API Extensions
-To create a new Perl variable, which can be accessed from your Perl script,
-use the following routines, depending on the variable type.
+Beginning with version 5.004, the following functions are also supported:
- SV* perl_get_sv("varname", TRUE);
- AV* perl_get_av("varname", TRUE);
- HV* perl_get_hv("varname", TRUE);
+ HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash);
+ HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash);
+
+ bool hv_exists_ent (HV* tb, SV* key, U32 hash);
+ SV* hv_delete_ent (HV* tb, SV* key, I32 flags, U32 hash);
+
+ SV* hv_iterkeysv (HE* entry);
-Notice the use of TRUE as the second parameter. The new variable can now
-be set, using the routines appropriate to the data type.
+Note that these functions take C<SV*> keys, which simplifies writing
+of extension code that deals with hash structures. These functions
+also allow passing of C<SV*> keys to C<tie> functions without forcing
+you to stringify the keys (unlike the previous set of functions).
+
+They also return and accept whole hash entries (C<HE*>), making their
+use more efficient (since the hash number for a particular string
+doesn't have to be recomputed every time). See L<API LISTING> later in
+this document for detailed descriptions.
+
+The following macros must always be used to access the contents of hash
+entries. Note that the arguments to these macros must be simple
+variables, since they may get evaluated more than once. See
+L<API LISTING> later in this document for detailed descriptions of these
+macros.
+
+ HePV(HE* he, STRLEN len)
+ HeVAL(HE* he)
+ HeHASH(HE* he)
+ HeSVKEY(HE* he)
+ HeSVKEY_force(HE* he)
+ HeSVKEY_set(HE* he, SV* sv)
+
+These two lower level macros are defined, but must only be used when
+dealing with keys that are not C<SV*>s:
-There are additional bits that may be OR'ed with the TRUE argument to enable
-certain extra features. Those bits are:
+ HeKEY(HE* he)
+ HeKLEN(HE* he)
- 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 C<varname> argument does not contain a package specifier, it is
-created in the current package.
=head2 References
References are a special type of scalar that point to other data types
(including references).
-To create a reference, use the following command:
+To create a reference, use either of the following functions:
- SV* newRV((SV*) thing);
+ SV* newRV_inc((SV*) thing);
+ SV* newRV_noinc((SV*) thing);
-The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. Once
-you have a reference, you can use the following macro to dereference the
-reference:
+The C<thing> argument can be any of an C<SV*>, C<AV*>, or C<HV*>. The
+functions are identical except that C<newRV_inc> increments the reference
+count of the C<thing>, while C<newRV_noinc> does not. For historical
+reasons, C<newRV> is a synonym for C<newRV_inc>.
+
+Once you have a reference, you can use the following macro to dereference
+the reference:
SvRV(SV*)
SvROK(SV*)
-To actually discover what the reference refers to, you must use the following
-macro and then check the value returned.
+To discover what type of value the reference refers to, use the following
+macro and then check the return value.
SvTYPE(SvRV(SV*))
SVt_IV Scalar
SVt_NV Scalar
SVt_PV Scalar
+ SVt_RV Scalar
SVt_PVAV Array
SVt_PVHV Hash
SVt_PVCV Code
- SVt_PVMG Blessed Scalar
+ SVt_PVGV Glob (possible a file handle)
+ SVt_PVMG Blessed or Magical Scalar
-=head1 XSUB's and the Argument Stack
+ See the sv.h header file for more details.
-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.
+=head2 Blessed References and Class Objects
-The stack arguments are accessible through the C<ST(n)> macro, which returns
-the C<n>'th stack argument. Argument 0 is the first argument passed in the
-Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
-an C<SV*> is used.
+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.
-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.
+A reference can be blessed into a package with the following function:
-To handle this situation, the PPCODE directive is used and the stack is
-extended using the macro:
+ SV* sv_bless(SV* sv, HV* stash);
- EXTEND(sp, num);
+The C<sv> argument must be a reference. The C<stash> argument specifies
+which class the reference will belong to. See
+L<Stashes and Globs> for information on converting class names into stashes.
-where C<sp> is the stack pointer, and C<num> is the number of elements the
-stack should be extended by.
+/* Still under construction */
-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:
+Upgrades rv to reference if not already one. Creates new SV for rv to
+point to. If C<classname> is non-null, the SV is blessed into the specified
+class. SV is returned.
- PUSHi(IV)
- PUSHn(double)
- PUSHp(char*, I32)
- PUSHs(SV*)
+ SV* newSVrv(SV* rv, char* classname);
-And now the Perl program calling C<tzname>, the two values will be assigned
-as in:
+Copies integer or double into an SV whose reference is C<rv>. SV is blessed
+if C<classname> is non-null.
- ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
+ SV* sv_setref_iv(SV* rv, char* classname, IV iv);
+ SV* sv_setref_nv(SV* rv, char* classname, NV iv);
-An alternate (and possibly simpler) method to pushing values on the stack is
-to use the macros:
+Copies the pointer value (I<the address, not the string!>) into an SV whose
+reference is rv. SV is blessed if C<classname> is non-null.
- XPUSHi(IV)
- XPUSHn(double)
- XPUSHp(char*, I32)
- XPUSHs(SV*)
+ SV* sv_setref_pv(SV* rv, char* classname, PV iv);
-These macros automatically adjust the stack for you, if needed.
+Copies string into an SV whose reference is C<rv>. Set length to 0 to let
+Perl calculate the string length. SV is blessed if C<classname> is non-null.
-For more information, consult L<perlapi>.
+ SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
-=head1 Mortality
+ int sv_isa(SV* sv, char* name);
+ int sv_isobject(SV* sv);
-In Perl, values are normally "immortal" -- that is, they are not freed unless
-explicitly done so (via the Perl C<undef> call or other routines in Perl
-itself).
+=head2 Creating New Variables
-Add cruft about reference counts.
+To create a new Perl variable with an undef value which can be accessed from
+your Perl script, use the following routines, depending on the variable type.
-In the above example with C<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.
+ SV* perl_get_sv("package::varname", TRUE);
+ AV* perl_get_av("package::varname", TRUE);
+ HV* perl_get_hv("package::varname", TRUE);
-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.
+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 macros whose values may be bitwise OR'ed with the
+C<TRUE> argument to enable certain extra features. Those bits are:
+
+ GV_ADDMULTI Marks the variable as multiply defined, thus preventing the
+ "Indentifier <varname> used only once: possible typo" warning.
+ GV_ADDWARN Issues the warning "Had to create <varname> unexpectedly" if
+ the variable did not exist before the function was called.
+
+If you do not specify a package name, the variable is created in the current
+package.
+
+=head2 Reference Counts and Mortality
+
+Perl uses an reference count-driven garbage collection mechanism. SV's,
+AV's, or HV's (xV for short in the following) start their life with a
+reference count of 1. If the reference count of an xV ever drops to 0,
+then it will be destroyed and its memory made available for reuse.
+
+This normally doesn't happen at the Perl level unless a variable is
+undef'ed or the last variable holding a reference to it is changed or
+overwritten. At the internal level, however, reference counts can be
+manipulated with the following macros:
+
+ int SvREFCNT(SV* sv);
+ SV* SvREFCNT_inc(SV* sv);
+ void SvREFCNT_dec(SV* sv);
+
+However, there is one other function which manipulates the reference
+count of its argument. The C<newRV_inc> function, you will recall,
+creates a reference to the specified argument. As a side effect,
+it increments the argument's reference count. If this is not what
+you want, use C<newRV_noinc> instead.
+
+For example, imagine you want to return a reference from an XSUB function.
+Inside the XSUB routine, you create an SV which initially has a reference
+count of one. Then you call C<newRV_inc>, passing it the just-created SV.
+This returns the reference as a new SV, but the reference count of the
+SV you passed to C<newRV_inc> has been incremented to two. Now you
+return the reference from the XSUB routine and forget about the SV.
+But Perl hasn't! Whenever the returned reference is destroyed, the
+reference count of the original SV is decreased to one and nothing happens.
+The SV will hang around without any way to access it until Perl itself
+terminates. This is a memory leak.
+
+The correct procedure, then, is to use C<newRV_noinc> instead of
+C<newRV_inc>. Then, if and when the last reference is destroyed,
+the reference count of the SV will go to zero and it will be destroyed,
+stopping any memory leak.
+
+There are some convenience functions available that can help with the
+destruction of xV's. These functions introduce the concept of "mortality".
+An xV that is mortal has had its reference count marked to be decremented,
+but not actually decremented, until "a short time later". Generally the
+term "short time later" means a single Perl statement, such as a call to
+an XSUB function. The actual determinant for when mortal xV's have their
+reference count decremented depends on two macros, SAVETMPS and FREETMPS.
+See L<perlcall> and L<perlxs> for more details on these macros.
+
+"Mortalization" then is at its simplest a deferred C<SvREFCNT_dec>.
+However, if you mortalize a variable twice, the reference count will
+later be decremented twice.
+
+You should be careful about creating mortal variables. Strange things
+can happen if you make the same value mortal within multiple contexts,
+or if you make a variable mortal multiple times.
To create a mortal variable, use the functions:
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 C<SV*>) to the C<sv_2mortal> or
-C<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 I<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.
-
-=head1 Stashes and Objects
-
-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:
-
+The first call creates a mortal SV, the second converts an existing
+SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and 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 (type-casted to C<SV*>) to the
+C<sv_2mortal> or C<sv_mortalcopy> routines.
+
+=head2 Stashes and Globs
+
+A "stash" is a hash 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 a GV (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
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 C<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.
+There is a single stash called "defstash" that holds the items that exist
+in the "main" package. To get at the items in other packages, append the
+string "::" to the package name. The items in the "Foo" package are in
+the stash "Foo::" in defstash. The items in the "Bar::Baz" package are
+in the stash "Baz::" in "Bar::"'s stash.
To get the stash pointer for a particular package, use the function:
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
-C<HV*>.
+C<HV*>. The C<create> flag will create a new package if it is set.
The name that C<gv_stash*v> wants is the name of the package whose symbol table
you want. The default package is called C<main>. If you have multiply nested
char* HvNAME(HV* stash);
-If you need to return a blessed value to your Perl script, you can use the
-following function:
+If you need to bless or re-bless an object you can use the following
+function:
SV* sv_bless(SV*, HV* stash)
For more information on references and blessings, consult L<perlref>.
-=head1 Magic
+=head2 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 C<$!> contains either the numeric value of C<errno>
+or its string equivalent from either C<strerror> or C<sys_errlist[]>.
+
+To force multiple data values into an SV, you must do two things: use the
+C<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 C<sv_set*v> routine
+you called first. This is because every C<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 C<sv_setiv> and C<sv_setpv> had been reversed, then the
+macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
+
+=head2 Magic Variables
[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 C<struct magic>'s, typedef'ed to C<MAGIC>.
set the C<SVt_PVMG> flag for the C<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
+overridden, and multiple instances of the same type of magic can be
associated with an SV.
The C<name> and C<namlem> arguments are used to associate a string with
The sv_magic function uses C<how> to determine which, if any, predefined
"Magic Virtual Table" should be assigned to the C<mg_virtual> field.
-See the "Magic Virtual Table" section below.
+See the "Magic Virtual Table" section below. The C<how> argument is also
+stored in the C<mg_type> field.
The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
structure. If it is not the same as the C<sv> argument, the reference
the C<how> argument is "#", or if it is a null pointer, then C<obj> is
merely stored, without the reference count being incremented.
+There is also a function to add magic to an C<HV>:
+
+ void hv_magic(HV *hv, GV *gv, int how);
+
+This simply calls C<sv_magic> and coerces the C<gv> argument into an C<SV>.
+
+To remove the magic from an SV, call the function sv_unmagic:
+
+ void sv_unmagic(SV *sv, int type);
+
+The C<type> argument should be equal to the C<how> value when the C<SV>
+was initially made magical.
+
=head2 Magic Virtual Tables
The C<mg_virtual> field in the C<MAGIC> structure is a pointer to a
The current kinds of Magic Virtual Tables are:
- mg_type MGVTBL Type of magicalness
- ------- ------ -------------------
+ mg_type MGVTBL Type of magical
+ ------- ------ ----------------------------
\0 vtbl_sv Regexp???
A vtbl_amagic Operator Overloading
a vtbl_amagicelem Operator Overloading
i vtbl_isaelem @ISA array element
L 0 (but sets RMAGICAL) Perl Module/Debugger???
l vtbl_dbline Debugger?
+ o vtbl_collxfrm Locale transformation
P vtbl_pack Tied Array or Hash
p vtbl_packelem Tied Array or Hash element
q vtbl_packelem Tied Scalar or Handle
U vtbl_uvar ???
v vtbl_vec Vector
x vtbl_substr Substring???
+ y vtbl_itervar Shadow "foreach" iterator variable
* vtbl_glob GV???
# vtbl_arylen Array Length
. vtbl_pos $. scalar variable
- ~ Reserved for extensions, but multiple extensions may clash
+ ~ None Used by certain extensions
-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
+When an uppercase and lowercase letter both exist in the table, then the
+uppercase letter is used to represent some kind of composite type (a list
+or a hash), and the lowercase letter is used to represent an element of
that composite type.
+The '~' magic type is defined specifically for use by extensions and
+will not be used by perl itself. Extensions can use ~ magic to 'attach'
+private information to variables (typically objects). This is especially
+useful because there is no way for normal perl code to corrupt this
+private information (unlike using extra elements of a hash object).
+
+Note that because multiple extensions may be using ~ magic it is
+important for extensions to take extra care with it. Typically only
+using it on objects blessed into the same class as the extension
+is sufficient. It may also be appropriate to add an I32 'signature'
+at the top of the private data area and check that.
+
=head2 Finding Magic
MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
This routine checks to see what types of magic C<sv> has. If the mg_type
-field is an upper-case letter, then the mg_obj is copied to C<nsv>, but
-the mg_type field is changed to be the lower-case letter.
+field is an uppercase letter, then the mg_obj is copied to C<nsv>, but
+the mg_type field is changed to be the lowercase letter.
-=head1 Double-Typed SV's
+=head1 Subroutines
-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.
+=head2 XSUBs and the Argument Stack
-Some scalar variables contain more than one type of scalar data. For
-example, the variable C<$!> contains either the numeric value of C<errno>
-or its string equivalent from either C<strerror> or C<sys_errlist[]>.
+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.
-To force multiple data values into an SV, you must do two things: use the
-C<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:
+The stack arguments are accessible through the C<ST(n)> macro, which returns
+the C<n>'th stack argument. Argument 0 is the first argument passed in the
+Perl subroutine call. These arguments are C<SV*>, and can be used anywhere
+an C<SV*> is used.
- SvIOK_on
- SvNOK_on
- SvPOK_on
- SvROK_on
+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 time zone's standard and summer time abbreviations.
-The particular macro you must use depends on which C<sv_set*v> routine
-you called first. This is because every C<sv_set*v> routine turns on
-only the bit for the particular type of data being set, and turns off
-all the rest.
+To handle this situation, the PPCODE directive is used and the stack is
+extended using the macro:
-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:
+ EXTEND(sp, num);
- extern int dberror;
- extern char *dberror_list;
+where C<sp> is the stack pointer, and C<num> is the number of elements the
+stack should be extended by.
- SV* sv = perl_get_sv("dberror", TRUE);
- sv_setiv(sv, (IV) dberror);
- sv_setpv(sv, dberror_list[dberror]);
- SvIOK_on(sv);
+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:
-If the order of C<sv_setiv> and C<sv_setpv> had been reversed, then the
-macro C<SvPOK_on> would need to be called instead of C<SvIOK_on>.
+ PUSHi(IV)
+ PUSHn(double)
+ PUSHp(char*, I32)
+ PUSHs(SV*)
+
+And now the Perl program calling C<tzname>, the two values will be assigned
+as in:
+
+ ($standard_abbrev, $summer_abbrev) = POSIX::tzname;
-=head1 Calling Perl Routines from within C Programs
+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. Thus, you
+do not need to call C<EXTEND> to extend the stack.
+
+For more information, consult L<perlxs> and L<perlxstut>.
+
+=head2 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:
FREETMPS
LEAVE
XPUSH*()
+ POP*()
-For more information, consult L<perlcall>.
+For a detailed description of calling conventions from C to Perl,
+consult L<perlcall>.
-=head1 Memory Allocation
+=head2 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.
+It is 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 satisfy allocation requests more quickly. 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
-C<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.
+These three macros are used to initially allocate memory.
+
+The first argument C<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 (most Perl developers now
+use run-time memory checkers), so this argument can be any number.
+
+The second argument C<pointer> should be the name of a variable that will
+point to the newly allocated memory.
-The second argument C<pointer> will point to the newly allocated memory.
The third and fourth arguments C<number> and C<type> specify how many of
the specified type of data structure should be allocated. The argument
C<type> is passed to C<sizeof>. The final argument to C<Newc>, C<cast>,
instances of the size of the C<type> data structure (using the C<sizeof>
function).
-=head1 AUTHOR
+=head2 PerlIO
-Jeff Okamoto <okamoto@corp.hp.com>
+The most recent development releases of Perl has been experimenting with
+removing Perl's dependency on the "normal" standard I/O suite and allowing
+other stdio implementations to be used. This involves creating a new
+abstraction layer that then calls whichever implementation of stdio Perl
+was compiled with. All XSUBs should now use the functions in the PerlIO
+abstraction layer and not make any assumptions about what kind of stdio
+is being used.
-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.
+For a complete description of the PerlIO abstraction, consult L<perlapio>.
+
+=head2 Putting a C value on Perl stack
+
+A lot of opcodes (this is an elementary operation in the internal perl
+stack machine) put an SV* on the stack. However, as an optimization
+the corresponding SV is (usually) not recreated each time. The opcodes
+reuse specially assigned SVs (I<target>s) which are (as a corollary)
+not constantly freed/created.
+
+Each of the targets is created only once (but see
+L<Scratchpads and recursion> below), and when an opcode needs to put
+an integer, a double, or a string on stack, it just sets the
+corresponding parts of its I<target> and puts the I<target> on stack.
+
+The macro to put this target on stack is C<PUSHTARG>, and it is
+directly used in some opcodes, as well as indirectly in zillions of
+others, which use it via C<(X)PUSH[pni]>.
+
+=head2 Scratchpads
+
+The question remains on when the SV's which are I<target>s for opcodes
+are created. The answer is that they are created when the current unit --
+a subroutine or a file (for opcodes for statements outside of
+subroutines) -- is compiled. During this time a special anonymous Perl
+array is created, which is called a scratchpad for the current
+unit.
+
+A scratchpad keeps SV's which are lexicals for the current unit and are
+targets for opcodes. One can deduce that an SV lives on a scratchpad
+by looking on its flags: lexicals have C<SVs_PADMY> set, and
+I<target>s have C<SVs_PADTMP> set.
+
+The correspondence between OP's and I<target>s is not 1-to-1. Different
+OP's in the compile tree of the unit can use the same target, if this
+would not conflict with the expected life of the temporary.
+
+=head2 Scratchpads and recursion
+
+In fact it is not 100% true that a compiled unit contains a pointer to
+the scratchpad AV. In fact it contains a pointer to an AV of
+(initially) one element, and this element is the scratchpad AV. Why do
+we need an extra level of indirection?
+
+The answer is B<recursion>, and maybe (sometime soon) B<threads>. Both
+these can create several execution pointers going into the same
+subroutine. For the subroutine-child not write over the temporaries
+for the subroutine-parent (lifespan of which covers the call to the
+child), the parent and the child should have different
+scratchpads. (I<And> the lexicals should be separate anyway!)
+
+So each subroutine is born with an array of scratchpads (of length 1).
+On each entry to the subroutine it is checked that the current
+depth of the recursion is not more than the length of this array, and
+if it is, new scratchpad is created and pushed into the array.
+
+The I<target>s on this scratchpad are C<undef>s, but they are already
+marked with correct flags.
+
+=head1 Compiled code
+
+=head2 Code tree
+
+Here we describe the internal form your code is converted to by
+Perl. Start with a simple example:
+
+ $a = $b + $c;
+
+This is converted to a tree similar to this one:
+
+ assign-to
+ / \
+ + $a
+ / \
+ $b $c
+
+(but slightly more complicated). This tree reflect the way Perl
+parsed your code, but has nothing to do with the execution order.
+There is an additional "thread" going through the nodes of the tree
+which shows the order of execution of the nodes. In our simplified
+example above it looks like:
+
+ $b ---> $c ---> + ---> $a ---> assign-to
+
+But with the actual compile tree for C<$a = $b + $c> it is different:
+some nodes I<optimized away>. As a corollary, though the actual tree
+contains more nodes than our simplified example, the execution order
+is the same as in our example.
+
+=head2 Examining the tree
+
+If you have your perl compiled for debugging (usually done with C<-D
+optimize=-g> on C<Configure> command line), you may examine the
+compiled tree by specifying C<-Dx> on the Perl command line. The
+output takes several lines per node, and for C<$b+$c> it looks like
+this:
+
+ 5 TYPE = add ===> 6
+ TARG = 1
+ FLAGS = (SCALAR,KIDS)
+ {
+ TYPE = null ===> (4)
+ (was rv2sv)
+ FLAGS = (SCALAR,KIDS)
+ {
+ 3 TYPE = gvsv ===> 4
+ FLAGS = (SCALAR)
+ GV = main::b
+ }
+ }
+ {
+ TYPE = null ===> (5)
+ (was rv2sv)
+ FLAGS = (SCALAR,KIDS)
+ {
+ 4 TYPE = gvsv ===> 5
+ FLAGS = (SCALAR)
+ GV = main::c
+ }
+ }
+
+This tree has 5 nodes (one per C<TYPE> specifier), only 3 of them are
+not optimized away (one per number in the left column). The immediate
+children of the given node correspond to C<{}> pairs on the same level
+of indentation, thus this listing corresponds to the tree:
+
+ add
+ / \
+ null null
+ | |
+ gvsv gvsv
+
+The execution order is indicated by C<===E<gt>> marks, thus it is C<3
+4 5 6> (node C<6> is not included into above listing), i.e.,
+C<gvsv gvsv add whatever>.
+
+=head2 Compile pass 1: check routines
+
+The tree is created by the I<pseudo-compiler> while yacc code feeds it
+the constructions it recognizes. Since yacc works bottom-up, so does
+the first pass of perl compilation.
+
+What makes this pass interesting for perl developers is that some
+optimization may be performed on this pass. This is optimization by
+so-called I<check routines>. The correspondence between node names
+and corresponding check routines is described in F<opcode.pl> (do not
+forget to run C<make regen_headers> if you modify this file).
+
+A check routine is called when the node is fully constructed except
+for the execution-order thread. Since at this time there is no
+back-links to the currently constructed node, one can do most any
+operation to the top-level node, including freeing it and/or creating
+new nodes above/below it.
+
+The check routine returns the node which should be inserted into the
+tree (if the top-level node was not modified, check routine returns
+its argument).
+
+By convention, check routines have names C<ck_*>. They are usually
+called from C<new*OP> subroutines (or C<convert>) (which in turn are
+called from F<perly.y>).
+
+=head2 Compile pass 1a: constant folding
+
+Immediately after the check routine is called the returned node is
+checked for being compile-time executable. If it is (the value is
+judged to be constant) it is immediately executed, and a I<constant>
+node with the "return value" of the corresponding subtree is
+substituted instead. The subtree is deleted.
+
+If constant folding was not performed, the execution-order thread is
+created.
+
+=head2 Compile pass 2: context propagation
+
+When a context for a part of compile tree is known, it is propagated
+down through the tree. Aat this time the context can have 5 values
+(instead of 2 for runtime context): void, boolean, scalar, list, and
+lvalue. In contrast with the pass 1 this pass is processed from top
+to bottom: a node's context determines the context for its children.
+
+Additional context-dependent optimizations are performed at this time.
+Since at this moment the compile tree contains back-references (via
+"thread" pointers), nodes cannot be free()d now. To allow
+optimized-away nodes at this stage, such nodes are null()ified instead
+of free()ing (i.e. their type is changed to OP_NULL).
+
+=head2 Compile pass 3: peephole optimization
+
+After the compile tree for a subroutine (or for an C<eval> or a file)
+is created, an additional pass over the code is performed. This pass
+is neither top-down or bottom-up, but in the execution order (with
+additional compilications for conditionals). These optimizations are
+done in the subroutine peep(). Optimizations performed at this stage
+are subject to the same restrictions as in the pass 2.
+
+=head1 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.
+
+=over 8
+
+=item AvFILL
+
+See C<av_len>.
+
+=item av_clear
+
+Clears an array, making it empty.
+
+ void av_clear _((AV* ar));
+
+=item av_extend
+
+Pre-extend an array. The C<key> is the index to which the array should be
+extended.
+
+ void av_extend _((AV* ar, I32 key));
+
+=item av_fetch
+
+Returns the SV at the specified index in the array. The C<key> is the
+index. If C<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 C<SV*>.
+
+ SV** av_fetch _((AV* ar, I32 key, I32 lval));
+
+=item av_len
+
+Returns the highest index in the array. Returns -1 if the array is empty.
+
+ I32 av_len _((AV* ar));
+
+=item av_make
+
+Creates a new AV and populates it with a list of SVs. The SVs are copied
+into the array, so they may be freed after the call to av_make. The new AV
+will have a reference count of 1.
+
+ AV* av_make _((I32 size, SV** svp));
+
+=item av_pop
+
+Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
+empty.
+
+ SV* av_pop _((AV* ar));
+
+=item av_push
+
+Pushes an SV onto the end of the array. The array will grow automatically
+to accommodate the addition.
+
+ void av_push _((AV* ar, SV* val));
+
+=item av_shift
+
+Shifts an SV off the beginning of the array.
+
+ SV* av_shift _((AV* ar));
+
+=item av_store
+
+Stores an SV in an array. The array index is specified as C<key>. The
+return value will be null if the operation failed, otherwise it can be
+dereferenced to get the original C<SV*>.
+
+ SV** av_store _((AV* ar, I32 key, SV* val));
+
+=item av_undef
+
+Undefines the array.
+
+ void av_undef _((AV* ar));
+
+=item av_unshift
+
+Unshift an SV onto the beginning of the array. The array will grow
+automatically to accommodate the addition.
+
+ void av_unshift _((AV* ar, I32 num));
+
+=item CLASS
+
+Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
+constructor. This is always a C<char*>. See C<THIS> and
+L<perlxs/"Using XS With C++">.
+
+=item Copy
+
+The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
+source, C<d> is the destination, C<n> is the number of items, and C<t> is
+the type.
+
+ (void) Copy( s, d, n, t );
+
+=item croak
+
+This is the XSUB-writer's interface to Perl's C<die> function. Use this
+function the same way you use the C C<printf> function. See C<warn>.
+
+=item CvSTASH
+
+Returns the stash of the CV.
+
+ HV * CvSTASH( SV* sv )
+
+=item DBsingle
+
+When Perl is run in debugging mode, with the B<-d> switch, this SV is a
+boolean which indicates whether subs are being single-stepped.
+Single-stepping is automatically turned on after every step. This is the C
+variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
+
+=item DBsub
+
+When Perl is run in debugging mode, with the B<-d> switch, this GV contains
+the SV which holds the name of the sub being debugged. This is the C
+variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
+The sub name can be found by
+
+ SvPV( GvSV( DBsub ), na )
+
+=item DBtrace
+
+Trace variable used when Perl is run in debugging mode, with the B<-d>
+switch. This is the C variable which corresponds to Perl's $DB::trace
+variable. See C<DBsingle>.
+
+=item dMARK
+
+Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
+C<dORIGMARK>.
+
+=item dORIGMARK
+
+Saves the original stack mark for the XSUB. See C<ORIGMARK>.
+
+=item dowarn
+
+The C variable which corresponds to Perl's $^W warning variable.
+
+=item dSP
+
+Declares a stack pointer variable, C<sp>, for the XSUB. See C<SP>.
+
+=item dXSARGS
+
+Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
+usually handled automatically by C<xsubpp>. Declares the C<items> variable
+to indicate the number of items on the stack.
+
+=item dXSI32
+
+Sets up the C<ix> variable for an XSUB which has aliases. This is usually
+handled automatically by C<xsubpp>.
+
+=item dXSI32
+
+Sets up the C<ix> variable for an XSUB which has aliases. This is usually
+handled automatically by C<xsubpp>.
+
+=item ENTER
+
+Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
+
+ ENTER;
+
+=item EXTEND
+
+Used to extend the argument stack for an XSUB's return values.
+
+ EXTEND( sp, int x );
+
+=item FREETMPS
+
+Closing bracket for temporaries on a callback. See C<SAVETMPS> and
+L<perlcall>.
+
+ FREETMPS;
+
+=item G_ARRAY
+
+Used to indicate array context. See C<GIMME> and L<perlcall>.
+
+=item G_DISCARD
+
+Indicates that arguments returned from a callback should be discarded. See
+L<perlcall>.
+
+=item G_EVAL
+
+Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
+
+=item GIMME
+
+The XSUB-writer's equivalent to Perl's C<wantarray>. Returns C<G_SCALAR> or
+C<G_ARRAY> for scalar or array context.
+
+=item G_NOARGS
+
+Indicates that no arguments are being sent to a callback. See L<perlcall>.
+
+=item G_SCALAR
+
+Used to indicate scalar context. See C<GIMME> and L<perlcall>.
+
+=item gv_fetchmeth
+
+Returns the glob with the given C<name> and a defined subroutine or
+C<NULL>. The glob lives in the given C<stash>, or in the stashes
+accessable via @ISA and @<UNIVERSAL>.
+
+The argument C<level> should be either 0 or -1. If C<level==0>, as a
+side-effect creates a glob with the given C<name> in the given
+C<stash> which in the case of success contains an alias for the
+subroutine, and sets up caching info for this glob. Similarly for all
+the searched stashes.
+
+This function grants C<"SUPER"> token as a postfix of the stash name.
+
+The GV returned from C<gv_fetchmeth> may be a method cache entry,
+which is not visible to Perl code. So when calling C<perl_call_sv>,
+you should not use the GV directly; instead, you should use the
+method's CV, which can be obtained from the GV with the C<GvCV> macro.
+
+ GV* gv_fetchmeth _((HV* stash, char* name, STRLEN len, I32 level));
+
+=item gv_fetchmethod
+
+Returns the glob which contains the subroutine to call to invoke the
+method on the C<stash>. In fact in the presense of autoloading this may
+be the glob for "AUTOLOAD". In this case the corresponing variable
+$AUTOLOAD is already setup.
+
+Note that if you want to keep this glob for a long time, you need to
+check for it being "AUTOLOAD", since at the later time the call
+may load a different subroutine due to $AUTOLOAD changing its value.
+Use the glob created via a side effect to do this.
+
+This function grants C<"SUPER"> token as a prefix of the method name.
+
+Has the same side-effects and as C<gv_fetchmeth> with C<level==0>.
+C<name> should be writable if contains C<':'> or C<'\''>.
+The warning against passing the GV returned by C<gv_fetchmeth> to
+C<perl_call_sv> apply equally to C<gv_fetchmethod>.
+
+ GV* gv_fetchmethod _((HV* stash, char* name));
+
+=item gv_stashpv
+
+Returns a pointer to the stash for a specified package. If C<create> is set
+then the package will be created if it does not already exist. If C<create>
+is not set and the package does not exist then NULL is returned.
+
+ HV* gv_stashpv _((char* name, I32 create));
+
+=item gv_stashsv
+
+Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
+
+ HV* gv_stashsv _((SV* sv, I32 create));
+
+=item GvSV
+
+Return the SV from the GV.
+
+=item HEf_SVKEY
+
+This flag, used in the length slot of hash entries and magic
+structures, specifies the structure contains a C<SV*> pointer where a
+C<char*> pointer is to be expected. (For information only--not to be used).
+
+=item HeHASH
+
+Returns the computed hash (type C<U32>) stored in the hash entry.
+
+ HeHASH(HE* he)
+
+=item HeKEY
+
+Returns the actual pointer stored in the key slot of the hash entry.
+The pointer may be either C<char*> or C<SV*>, depending on the value of
+C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
+are usually preferable for finding the value of a key.
+
+ HeKEY(HE* he)
+
+=item HeKLEN
+
+If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
+holds an C<SV*> key. Otherwise, holds the actual length of the key.
+Can be assigned to. The C<HePV()> macro is usually preferable for finding
+key lengths.
+
+ HeKLEN(HE* he)
+
+=item HePV
+
+Returns the key slot of the hash entry as a C<char*> value, doing any
+necessary dereferencing of possibly C<SV*> keys. The length of
+the string is placed in C<len> (this is a macro, so do I<not> use
+C<&len>). If you do not care about what the length of the key is,
+you may use the global variable C<na>. Remember though, that hash
+keys in perl are free to contain embedded nulls, so using C<strlen()>
+or similar is not a good way to find the length of hash keys.
+This is very similar to the C<SvPV()> macro described elsewhere in
+this document.
+
+ HePV(HE* he, STRLEN len)
+
+=item HeSVKEY
+
+Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
+does not contain an C<SV*> key.
+
+ HeSVKEY(HE* he)
+
+=item HeSVKEY_force
+
+Returns the key as an C<SV*>. Will create and return a temporary
+mortal C<SV*> if the hash entry contains only a C<char*> key.
+
+ HeSVKEY_force(HE* he)
+
+=item HeSVKEY_set
+
+Sets the key to a given C<SV*>, taking care to set the appropriate flags
+to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
+
+ HeSVKEY_set(HE* he, SV* sv)
+
+=item HeVAL
+
+Returns the value slot (type C<SV*>) stored in the hash entry.
+
+ HeVAL(HE* he)
+
+=item hv_clear
+
+Clears a hash, making it empty.
+
+ void hv_clear _((HV* tb));
+
+=item hv_delayfree_ent
+
+Releases a hash entry, such as while iterating though the hash, but
+delays actual freeing of key and value until the end of the current
+statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
+and C<hv_free_ent>.
+
+ void hv_delayfree_ent _((HV* hv, HE* entry));
+
+=item hv_delete
+
+Deletes a key/value pair in the hash. The value SV is removed from the hash
+and returned to the caller. The C<klen> is the length of the key. The
+C<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));
+
+=item hv_delete_ent
+
+Deletes a key/value pair in the hash. The value SV is removed from the hash
+and returned to the caller. The C<flags> value will normally be zero; if set
+to G_DISCARD then null will be returned. C<hash> can be a valid pre-computed
+hash value, or 0 to ask for it to be computed.
+
+ SV* hv_delete_ent _((HV* tb, SV* key, I32 flags, U32 hash));
+
+=item hv_exists
+
+Returns a boolean indicating whether the specified hash key exists. The
+C<klen> is the length of the key.
+
+ bool hv_exists _((HV* tb, char* key, U32 klen));
+
+=item hv_exists_ent
+
+Returns a boolean indicating whether the specified hash key exists. C<hash>
+can be a valid pre-computed hash value, or 0 to ask for it to be computed.
+
+ bool hv_exists_ent _((HV* tb, SV* key, U32 hash));
+
+=item hv_fetch
+
+Returns the SV which corresponds to the specified key in the hash. The
+C<klen> is the length of the key. If C<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 C<SV*>.
+
+ SV** hv_fetch _((HV* tb, char* key, U32 klen, I32 lval));
+
+=item hv_fetch_ent
+
+Returns the hash entry which corresponds to the specified key in the hash.
+C<hash> must be a valid pre-computed hash number for the given C<key>, or
+0 if you want the function to compute it. IF C<lval> is set then the
+fetch will be part of a store. Make sure the return value is non-null
+before accessing it. The return value when C<tb> is a tied hash
+is a pointer to a static location, so be sure to make a copy of the
+structure if you need to store it somewhere.
+
+ HE* hv_fetch_ent _((HV* tb, SV* key, I32 lval, U32 hash));
+
+=item hv_free_ent
+
+Releases a hash entry, such as while iterating though the hash. See
+C<hv_iternext> and C<hv_delayfree_ent>.
+
+ void hv_free_ent _((HV* hv, HE* entry));
+
+=item hv_iterinit
+
+Prepares a starting point to traverse a hash table.
+
+ I32 hv_iterinit _((HV* tb));
+
+=item hv_iterkey
+
+Returns the key from the current position of the hash iterator. See
+C<hv_iterinit>.
+
+ char* hv_iterkey _((HE* entry, I32* retlen));
+
+=item hv_iterkeysv
+
+Returns the key as an C<SV*> from the current position of the hash
+iterator. The return value will always be a mortal copy of the
+key. Also see C<hv_iterinit>.
+
+ SV* hv_iterkeysv _((HE* entry));
+
+=item hv_iternext
+
+Returns entries from a hash iterator. See C<hv_iterinit>.
+
+ HE* hv_iternext _((HV* tb));
+
+=item hv_iternextsv
+
+Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
+operation.
+
+ SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));
+
+=item hv_iterval
+
+Returns the value from the current position of the hash iterator. See
+C<hv_iterkey>.
+
+ SV* hv_iterval _((HV* tb, HE* entry));
+
+=item hv_magic
+
+Adds magic to a hash. See C<sv_magic>.
+
+ void hv_magic _((HV* hv, GV* gv, int how));
+
+=item HvNAME
+
+Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
+
+ char *HvNAME (HV* stash)
+
+=item hv_store
+
+Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
+the length of the key. The C<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 C<SV*>.
+
+ SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
+
+=item hv_store_ent
+
+Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
+parameter is the pre-computed hash value; if it is zero then Perl will
+compute it. The return value is the new hash entry so created. It will be
+null if the operation failed or if the entry was stored in a tied hash.
+Otherwise the contents of the return value can be accessed using the
+C<He???> macros described here.
+
+ HE* hv_store_ent _((HV* tb, SV* key, SV* val, U32 hash));
+
+=item hv_undef
+
+Undefines the hash.
+
+ void hv_undef _((HV* tb));
+
+=item isALNUM
+
+Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
+character or digit.
+
+ int isALNUM (char c)
+
+=item isALPHA
+
+Returns a boolean indicating whether the C C<char> is an ascii alphabetic
+character.
+
+ int isALPHA (char c)
+
+=item isDIGIT
+
+Returns a boolean indicating whether the C C<char> is an ascii digit.
+
+ int isDIGIT (char c)
+
+=item isLOWER
+
+Returns a boolean indicating whether the C C<char> is a lowercase character.
+
+ int isLOWER (char c)
+
+=item isSPACE
+
+Returns a boolean indicating whether the C C<char> is whitespace.
+
+ int isSPACE (char c)
+
+=item isUPPER
+
+Returns a boolean indicating whether the C C<char> is an uppercase character.
+
+ int isUPPER (char c)
+
+=item items
+
+Variable which is setup by C<xsubpp> to indicate the number of items on the
+stack. See L<perlxs/"Variable-length Parameter Lists">.
+
+=item ix
+
+Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
+was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
+
+=item LEAVE
+
+Closing bracket on a callback. See C<ENTER> and L<perlcall>.
+
+ LEAVE;
+
+=item MARK
+
+Stack marker variable for the XSUB. See C<dMARK>.
+
+=item mg_clear
+
+Clear something magical that the SV represents. See C<sv_magic>.
+
+ int mg_clear _((SV* sv));
+
+=item mg_copy
+
+Copies the magic from one SV to another. See C<sv_magic>.
+
+ int mg_copy _((SV *, SV *, char *, STRLEN));
+
+=item mg_find
+
+Finds the magic pointer for type matching the SV. See C<sv_magic>.
+
+ MAGIC* mg_find _((SV* sv, int type));
+
+=item mg_free
+
+Free any magic storage used by the SV. See C<sv_magic>.
+
+ int mg_free _((SV* sv));
+
+=item mg_get
+
+Do magic after a value is retrieved from the SV. See C<sv_magic>.
+
+ int mg_get _((SV* sv));
+
+=item mg_len
+
+Report on the SV's length. See C<sv_magic>.
+
+ U32 mg_len _((SV* sv));
+
+=item mg_magical
+
+Turns on the magical status of an SV. See C<sv_magic>.
+
+ void mg_magical _((SV* sv));
+
+=item mg_set
+
+Do magic after a value is assigned to the SV. See C<sv_magic>.
+
+ int mg_set _((SV* sv));
+
+=item Move
+
+The XSUB-writer's interface to the C C<memmove> function. The C<s> is the
+source, C<d> is the destination, C<n> is the number of items, and C<t> is
+the type.
+
+ (void) Move( s, d, n, t );
+
+=item na
+
+A variable which may be used with C<SvPV> to tell Perl to calculate the
+string length.
+
+=item New
+
+The XSUB-writer's interface to the C C<malloc> function.
+
+ void * New( x, void *ptr, int size, type )
+
+=item Newc
+
+The XSUB-writer's interface to the C C<malloc> function, with cast.
+
+ void * Newc( x, void *ptr, int size, type, cast )
+
+=item Newz
+
+The XSUB-writer's interface to the C C<malloc> function. The allocated
+memory is zeroed with C<memzero>.
+
+ void * Newz( x, void *ptr, int size, type )
+
+=item newAV
+
+Creates a new AV. The reference count is set to 1.
+
+ AV* newAV _((void));
+
+=item newHV
+
+Creates a new HV. The reference count is set to 1.
+
+ HV* newHV _((void));
+
+=item newRV_inc
+
+Creates an RV wrapper for an SV. The reference count for the original SV is
+incremented.
+
+ SV* newRV_inc _((SV* ref));
+
+For historical reasons, "newRV" is a synonym for "newRV_inc".
+
+=item newRV_noinc
+
+Creates an RV wrapper for an SV. The reference count for the original
+SV is B<not> incremented.
+
+ SV* newRV_noinc _((SV* ref));
+
+=item newSV
+
+Creates a new SV. The C<len> parameter indicates the number of bytes of
+preallocated string space the SV should have. The reference count for the
+new SV is set to 1.
+
+ SV* newSV _((STRLEN len));
+
+=item newSViv
+
+Creates a new SV and copies an integer into it. The reference count for the
+SV is set to 1.
+
+ SV* newSViv _((IV i));
+
+=item newSVnv
+
+Creates a new SV and copies a double into it. The reference count for the
+SV is set to 1.
+
+ SV* newSVnv _((NV i));
+
+=item newSVpv
+
+Creates a new SV and copies a string into it. The reference count for the
+SV is set to 1. If C<len> is zero then Perl will compute the length.
+
+ SV* newSVpv _((char* s, STRLEN len));
+
+=item newSVrv
+
+Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
+it will be upgraded to one. If C<classname> is non-null then the new SV will
+be blessed in the specified package. The new SV is returned and its
+reference count is 1.
+
+ SV* newSVrv _((SV* rv, char* classname));
+
+=item newSVsv
+
+Creates a new SV which is an exact duplicate of the original SV.
+
+ SV* newSVsv _((SV* old));
+
+=item newXS
+
+Used by C<xsubpp> to hook up XSUBs as Perl subs.
+
+=item newXSproto
+
+Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
+the subs.
+
+=item Nullav
+
+Null AV pointer.
+
+=item Nullch
+
+Null character pointer.
+
+=item Nullcv
+
+Null CV pointer.
+
+=item Nullhv
+
+Null HV pointer.
+
+=item Nullsv
+
+Null SV pointer.
+
+=item ORIGMARK
+
+The original stack mark for the XSUB. See C<dORIGMARK>.
+
+=item perl_alloc
+
+Allocates a new Perl interpreter. See L<perlembed>.
+
+=item perl_call_argv
+
+Performs a callback to the specified Perl sub. See L<perlcall>.
+
+ I32 perl_call_argv _((char* subname, I32 flags, char** argv));
+
+=item perl_call_method
+
+Performs a callback to the specified Perl method. The blessed object must
+be on the stack. See L<perlcall>.
+
+ I32 perl_call_method _((char* methname, I32 flags));
+
+=item perl_call_pv
+
+Performs a callback to the specified Perl sub. See L<perlcall>.
+
+ I32 perl_call_pv _((char* subname, I32 flags));
+
+=item perl_call_sv
+
+Performs a callback to the Perl sub whose name is in the SV. See
+L<perlcall>.
+
+ I32 perl_call_sv _((SV* sv, I32 flags));
+
+=item perl_construct
+
+Initializes a new Perl interpreter. See L<perlembed>.
+
+=item perl_destruct
+
+Shuts down a Perl interpreter. See L<perlembed>.
+
+=item perl_eval_sv
+
+Tells Perl to C<eval> the string in the SV.
+
+ I32 perl_eval_sv _((SV* sv, I32 flags));
+
+=item perl_free
+
+Releases a Perl interpreter. See L<perlembed>.
+
+=item perl_get_av
+
+Returns the AV of the specified Perl array. If C<create> is set and the
+Perl variable does not exist then it will be created. If C<create> is not
+set and the variable does not exist then null is returned.
+
+ AV* perl_get_av _((char* name, I32 create));
+
+=item perl_get_cv
+
+Returns the CV of the specified Perl sub. If C<create> is set and the Perl
+variable does not exist then it will be created. If C<create> is not
+set and the variable does not exist then null is returned.
+
+ CV* perl_get_cv _((char* name, I32 create));
+
+=item perl_get_hv
+
+Returns the HV of the specified Perl hash. If C<create> is set and the Perl
+variable does not exist then it will be created. If C<create> is not
+set and the variable does not exist then null is returned.
+
+ HV* perl_get_hv _((char* name, I32 create));
+
+=item perl_get_sv
+
+Returns the SV of the specified Perl scalar. If C<create> is set and the
+Perl variable does not exist then it will be created. If C<create> is not
+set and the variable does not exist then null is returned.
+
+ SV* perl_get_sv _((char* name, I32 create));
+
+=item perl_parse
+
+Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
+
+=item perl_require_pv
+
+Tells Perl to C<require> a module.
+
+ void perl_require_pv _((char* pv));
+
+=item perl_run
+
+Tells a Perl interpreter to run. See L<perlembed>.
+
+=item POPi
+
+Pops an integer off the stack.
+
+ int POPi();
+
+=item POPl
+
+Pops a long off the stack.
+
+ long POPl();
+
+=item POPp
+
+Pops a string off the stack.
+
+ char * POPp();
+
+=item POPn
+
+Pops a double off the stack.
+
+ double POPn();
+
+=item POPs
+
+Pops an SV off the stack.
+
+ SV* POPs();
+
+=item PUSHMARK
+
+Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
+
+ PUSHMARK(p)
+
+=item PUSHi
+
+Push an integer onto the stack. The stack must have room for this element.
+See C<XPUSHi>.
+
+ PUSHi(int d)
+
+=item PUSHn
+
+Push a double onto the stack. The stack must have room for this element.
+See C<XPUSHn>.
+
+ PUSHn(double d)
+
+=item PUSHp
+
+Push a string onto the stack. The stack must have room for this element.
+The C<len> indicates the length of the string. See C<XPUSHp>.
+
+ PUSHp(char *c, int len )
+
+=item PUSHs
+
+Push an SV onto the stack. The stack must have room for this element. See
+C<XPUSHs>.
+
+ PUSHs(sv)
+
+=item PUTBACK
+
+Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
+See C<PUSHMARK> and L<perlcall> for other uses.
+
+ PUTBACK;
+
+=item Renew
+
+The XSUB-writer's interface to the C C<realloc> function.
+
+ void * Renew( void *ptr, int size, type )
+
+=item Renewc
+
+The XSUB-writer's interface to the C C<realloc> function, with cast.
+
+ void * Renewc( void *ptr, int size, type, cast )
+
+=item RETVAL
+
+Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
+This is always the proper type for the XSUB.
+See L<perlxs/"The RETVAL Variable">.
+
+=item safefree
+
+The XSUB-writer's interface to the C C<free> function.
+
+=item safemalloc
+
+The XSUB-writer's interface to the C C<malloc> function.
+
+=item saferealloc
+
+The XSUB-writer's interface to the C C<realloc> function.
+
+=item savepv
+
+Copy a string to a safe spot. This does not use an SV.
+
+ char* savepv _((char* sv));
+
+=item savepvn
+
+Copy a string to a safe spot. The C<len> indicates number of bytes to
+copy. This does not use an SV.
+
+ char* savepvn _((char* sv, I32 len));
+
+=item SAVETMPS
+
+Opening bracket for temporaries on a callback. See C<FREETMPS> and
+L<perlcall>.
+
+ SAVETMPS;
+
+=item SP
+
+Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
+C<SPAGAIN>.
+
+=item SPAGAIN
+
+Re-fetch the stack pointer. Used after a callback. See L<perlcall>.
+
+ SPAGAIN;
+
+=item ST
+
+Used to access elements on the XSUB's stack.
+
+ SV* ST(int x)
+
+=item strEQ
+
+Test two strings to see if they are equal. Returns true or false.
+
+ int strEQ( char *s1, char *s2 )
+
+=item strGE
+
+Test two strings to see if the first, C<s1>, is greater than or equal to the
+second, C<s2>. Returns true or false.
+
+ int strGE( char *s1, char *s2 )
+
+=item strGT
+
+Test two strings to see if the first, C<s1>, is greater than the second,
+C<s2>. Returns true or false.
+
+ int strGT( char *s1, char *s2 )
+
+=item strLE
+
+Test two strings to see if the first, C<s1>, is less than or equal to the
+second, C<s2>. Returns true or false.
+
+ int strLE( char *s1, char *s2 )
+
+=item strLT
+
+Test two strings to see if the first, C<s1>, is less than the second,
+C<s2>. Returns true or false.
+
+ int strLT( char *s1, char *s2 )
+
+=item strNE
+
+Test two strings to see if they are different. Returns true or false.
+
+ int strNE( char *s1, char *s2 )
+
+=item strnEQ
+
+Test two strings to see if they are equal. The C<len> parameter indicates
+the number of bytes to compare. Returns true or false.
+
+ int strnEQ( char *s1, char *s2 )
+
+=item strnNE
+
+Test two strings to see if they are different. The C<len> parameter
+indicates the number of bytes to compare. Returns true or false.
+
+ int strnNE( char *s1, char *s2, int len )
+
+=item sv_2mortal
+
+Marks an SV as mortal. The SV will be destroyed when the current context
+ends.
+
+ SV* sv_2mortal _((SV* sv));
+
+=item sv_bless
+
+Blesses an SV into a specified package. The SV must be an RV. The package
+must be designated by its stash (see C<gv_stashpv()>). The reference count
+of the SV is unaffected.
+
+ SV* sv_bless _((SV* sv, HV* stash));
+
+=item sv_catpv
+
+Concatenates the string onto the end of the string which is in the SV.
+
+ void sv_catpv _((SV* sv, char* ptr));
+
+=item sv_catpvn
+
+Concatenates the string onto the end of the string which is in the SV. The
+C<len> indicates number of bytes to copy.
+
+ void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
+
+=item sv_catsv
+
+Concatenates the string from SV C<ssv> onto the end of the string in SV
+C<dsv>.
+
+ void sv_catsv _((SV* dsv, SV* ssv));
+
+=item sv_cmp
+
+Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
+string in C<sv1> is less than, equal to, or greater than the string in
+C<sv2>.
+
+ I32 sv_cmp _((SV* sv1, SV* sv2));
+
+=item sv_cmp
+
+Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
+string in C<sv1> is less than, equal to, or greater than the string in
+C<sv2>.
+
+ I32 sv_cmp _((SV* sv1, SV* sv2));
+
+=item SvCUR
+
+Returns the length of the string which is in the SV. See C<SvLEN>.
+
+ int SvCUR (SV* sv)
+
+=item SvCUR_set
+
+Set the length of the string which is in the SV. See C<SvCUR>.
+
+ SvCUR_set (SV* sv, int val )
+
+=item sv_dec
+
+Auto-decrement of the value in the SV.
+
+ void sv_dec _((SV* sv));
+
+=item sv_dec
+
+Auto-decrement of the value in the SV.
+
+ void sv_dec _((SV* sv));
+
+=item SvEND
+
+Returns a pointer to the last character in the string which is in the SV.
+See C<SvCUR>. Access the character as
+
+ *SvEND(sv)
+
+=item sv_eq
+
+Returns a boolean indicating whether the strings in the two SVs are
+identical.
+
+ I32 sv_eq _((SV* sv1, SV* sv2));
+
+=item SvGROW
+
+Expands the character buffer in the SV. Calls C<sv_grow> to perform the
+expansion if necessary. Returns a pointer to the character buffer.
+
+ char * SvGROW( SV* sv, int len )
+
+=item sv_grow
+
+Expands the character buffer in the SV. This will use C<sv_unref> and will
+upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
+Use C<SvGROW>.
+
+=item sv_inc
+
+Auto-increment of the value in the SV.
+
+ void sv_inc _((SV* sv));
+
+=item SvIOK
+
+Returns a boolean indicating whether the SV contains an integer.
+
+ int SvIOK (SV* SV)
+
+=item SvIOK_off
+
+Unsets the IV status of an SV.
+
+ SvIOK_off (SV* sv)
+
+=item SvIOK_on
+
+Tells an SV that it is an integer.
+
+ SvIOK_on (SV* sv)
+
+=item SvIOK_only
+
+Tells an SV that it is an integer and disables all other OK bits.
+
+ SvIOK_on (SV* sv)
+
+=item SvIOK_only
+
+Tells an SV that it is an integer and disables all other OK bits.
+
+ SvIOK_on (SV* sv)
+
+=item SvIOKp
+
+Returns a boolean indicating whether the SV contains an integer. Checks the
+B<private> setting. Use C<SvIOK>.
+
+ int SvIOKp (SV* SV)
+
+=item 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));
+
+=item SvIV
+
+Returns the integer which is in the SV.
+
+ int SvIV (SV* sv)
+
+=item 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));
+
+=item SvIVX
+
+Returns the integer which is stored in the SV.
+
+ int SvIVX (SV* sv);
+
+=item SvLEN
+
+Returns the size of the string buffer in the SV. See C<SvCUR>.
+
+ int SvLEN (SV* sv)
+
+=item sv_len
+
+Returns the length of the string in the SV. Use C<SvCUR>.
+
+ STRLEN sv_len _((SV* sv));
+
+=item sv_len
+
+Returns the length of the string in the SV. Use C<SvCUR>.
+
+ STRLEN sv_len _((SV* sv));
+
+=item sv_magic
+
+Adds magic to an SV.
+
+ void sv_magic _((SV* sv, SV* obj, int how, char* name, I32 namlen));
+
+=item 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));
+
+=item SvOK
+
+Returns a boolean indicating whether the value is an SV.
+
+ int SvOK (SV* sv)
+
+=item sv_newmortal
+
+Creates a new SV which is mortal. The reference count of the SV is set to 1.
+
+ SV* sv_newmortal _((void));
+
+=item sv_no
+
+This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
+
+=item SvNIOK
+
+Returns a boolean indicating whether the SV contains a number, integer or
+double.
+
+ int SvNIOK (SV* SV)
+
+=item SvNIOK_off
+
+Unsets the NV/IV status of an SV.
+
+ SvNIOK_off (SV* sv)
+
+=item SvNIOKp
+
+Returns a boolean indicating whether the SV contains a number, integer or
+double. Checks the B<private> setting. Use C<SvNIOK>.
+
+ int SvNIOKp (SV* SV)
+
+=item SvNOK
+
+Returns a boolean indicating whether the SV contains a double.
+
+ int SvNOK (SV* SV)
+
+=item SvNOK_off
+
+Unsets the NV status of an SV.
+
+ SvNOK_off (SV* sv)
+
+=item SvNOK_on
+
+Tells an SV that it is a double.
+
+ SvNOK_on (SV* sv)
+
+=item SvNOK_only
+
+Tells an SV that it is a double and disables all other OK bits.
+
+ SvNOK_on (SV* sv)
+
+=item SvNOK_only
+
+Tells an SV that it is a double and disables all other OK bits.
+
+ SvNOK_on (SV* sv)
+
+=item SvNOKp
+
+Returns a boolean indicating whether the SV contains a double. Checks the
+B<private> setting. Use C<SvNOK>.
+
+ int SvNOKp (SV* SV)
+
+=item SvNV
+
+Returns the double which is stored in the SV.
+
+ double SvNV (SV* sv);
+
+=item SvNVX
+
+Returns the double which is stored in the SV.
+
+ double SvNVX (SV* sv);
+
+=item SvPOK
+
+Returns a boolean indicating whether the SV contains a character string.
+
+ int SvPOK (SV* SV)
+
+=item SvPOK_off
+
+Unsets the PV status of an SV.
+
+ SvPOK_off (SV* sv)
+
+=item SvPOK_on
+
+Tells an SV that it is a string.
+
+ SvPOK_on (SV* sv)
+
+=item SvPOK_only
+
+Tells an SV that it is a string and disables all other OK bits.
+
+ SvPOK_on (SV* sv)
+
+=item SvPOK_only
+
+Tells an SV that it is a string and disables all other OK bits.
+
+ SvPOK_on (SV* sv)
+
+=item SvPOKp
+
+Returns a boolean indicating whether the SV contains a character string.
+Checks the B<private> setting. Use C<SvPOK>.
+
+ int SvPOKp (SV* SV)
+
+=item 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 C<len> is C<na> then Perl will
+handle the length on its own.
+
+ char * SvPV (SV* sv, int len )
+
+=item SvPVX
+
+Returns a pointer to the string in the SV. The SV must contain a string.
+
+ char * SvPVX (SV* sv)
+
+=item SvREFCNT
+
+Returns the value of the object's reference count.
+
+ int SvREFCNT (SV* sv);
+
+=item SvREFCNT_dec
+
+Decrements the reference count of the given SV.
+
+ void SvREFCNT_dec (SV* sv)
+
+=item SvREFCNT_inc
+
+Increments the reference count of the given SV.
+
+ void SvREFCNT_inc (SV* sv)
+
+=item SvROK
+
+Tests if the SV is an RV.
+
+ int SvROK (SV* sv)
+
+=item SvROK_off
+
+Unsets the RV status of an SV.
+
+ SvROK_off (SV* sv)
+
+=item SvROK_on
+
+Tells an SV that it is an RV.
+
+ SvROK_on (SV* sv)
+
+=item SvRV
+
+Dereferences an RV to return the SV.
+
+ SV* SvRV (SV* sv);
+
+=item sv_setiv
+
+Copies an integer into the given SV.
+
+ void sv_setiv _((SV* sv, IV num));
+
+=item sv_setnv
+
+Copies a double into the given SV.
+
+ void sv_setnv _((SV* sv, double num));
+
+=item sv_setpv
+
+Copies a string into an SV. The string must be null-terminated.
+
+ void sv_setpv _((SV* sv, char* ptr));
+
+=item sv_setpvn
+
+Copies a string into an SV. The C<len> parameter indicates the number of
+bytes to be copied.
+
+ void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
+
+=item sv_setref_iv
+
+Copies an integer into a new SV, optionally blessing the SV. The C<rv>
+argument will be upgraded to an RV. That RV will be modified to point to
+the new SV. The C<classname> argument indicates the package for the
+blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
+will be returned and will have a reference count of 1.
+
+ SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
+
+=item sv_setref_nv
+
+Copies a double into a new SV, optionally blessing the SV. The C<rv>
+argument will be upgraded to an RV. That RV will be modified to point to
+the new SV. The C<classname> argument indicates the package for the
+blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
+will be returned and will have a reference count of 1.
+
+ SV* sv_setref_nv _((SV *rv, char *classname, double nv));
+
+=item sv_setref_pv
+
+Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
+argument will be upgraded to an RV. That RV will be modified to point to
+the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
+into the SV. The C<classname> argument indicates the package for the
+blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
+will be returned and will have a reference count 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 C<sv_setref_pvn> copies the string while this copies the pointer.
+
+=item sv_setref_pvn
+
+Copies a string into a new SV, optionally blessing the SV. The length of the
+string must be specified with C<n>. The C<rv> argument will be upgraded to
+an RV. That RV will be modified to point to the new SV. The C<classname>
+argument indicates the package for the blessing. Set C<classname> to
+C<Nullch> to avoid the blessing. The new SV will be returned and will have
+a reference count of 1.
+
+ SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
+
+Note that C<sv_setref_pv> copies the pointer while this copies the string.
+
+=item sv_setsv
+
+Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
+The source SV may be destroyed if it is mortal.
+
+ void sv_setsv _((SV* dsv, SV* ssv));
+
+=item SvSTASH
+
+Returns the stash of the SV.
+
+ HV * SvSTASH (SV* sv)
+
+=item SVt_IV
+
+Integer type flag for scalars. See C<svtype>.
+
+=item SVt_PV
+
+Pointer type flag for scalars. See C<svtype>.
+
+=item SVt_PVAV
+
+Type flag for arrays. See C<svtype>.
+
+=item SVt_PVCV
+
+Type flag for code refs. See C<svtype>.
+
+=item SVt_PVHV
+
+Type flag for hashes. See C<svtype>.
+
+=item SVt_PVMG
+
+Type flag for blessed scalars. See C<svtype>.
+
+=item SVt_NV
+
+Double type flag for scalars. See C<svtype>.
+
+=item SvTRUE
+
+Returns a boolean indicating whether Perl would evaluate the SV as true or
+false, defined or undefined.
+
+ int SvTRUE (SV* sv)
+
+=item SvTYPE
+
+Returns the type of the SV. See C<svtype>.
+
+ svtype SvTYPE (SV* sv)
+
+=item svtype
+
+An enum of flags for Perl types. These are found in the file B<sv.h> in the
+C<svtype> enum. Test these flags with the C<SvTYPE> macro.
+
+=item SvUPGRADE
+
+Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
+the upgrade if necessary. See C<svtype>.
+
+ bool SvUPGRADE _((SV* sv, svtype mt));
+
+=item sv_upgrade
+
+Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
+
+=item sv_undef
+
+This is the C<undef> SV. Always refer to this as C<&sv_undef>.
+
+=item sv_unref
+
+Unsets the RV status of the SV, and decrements the reference count of
+whatever was being referenced by the RV. This can almost be thought of
+as a reversal of C<newSVrv>. See C<SvROK_off>.
+
+ void sv_unref _((SV* sv));
+
+=item sv_usepvn
+
+Tells an SV to use C<ptr> to find its string value. Normally the string is
+stored inside the SV but sv_usepvn allows the SV to use an outside string.
+The C<ptr> should point to memory that was allocated by C<malloc>. The
+string length, C<len>, must be supplied. This function will realloc the
+memory pointed to by C<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));
+
+=item sv_yes
+
+This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
+
+=item THIS
+
+Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
+This is always the proper type for the C++ object. See C<CLASS> and
+L<perlxs/"Using XS With C++">.
+
+=item toLOWER
+
+Converts the specified character to lowercase.
+
+ int toLOWER (char c)
+
+=item toUPPER
+
+Converts the specified character to uppercase.
+
+ int toUPPER (char c)
+
+=item warn
+
+This is the XSUB-writer's interface to Perl's C<warn> function. Use this
+function the same way you use the C C<printf> function. See C<croak()>.
+
+=item XPUSHi
+
+Push an integer onto the stack, extending the stack if necessary. See
+C<PUSHi>.
+
+ XPUSHi(int d)
+
+=item XPUSHn
+
+Push a double onto the stack, extending the stack if necessary. See
+C<PUSHn>.
+
+ XPUSHn(double d)
+
+=item XPUSHp
+
+Push a string onto the stack, extending the stack if necessary. The C<len>
+indicates the length of the string. See C<PUSHp>.
+
+ XPUSHp(char *c, int len)
+
+=item XPUSHs
+
+Push an SV onto the stack, extending the stack if necessary. See C<PUSHs>.
+
+ XPUSHs(sv)
+
+=item XS
+
+Macro to declare an XSUB and its C parameter list. This is handled by
+C<xsubpp>.
+
+=item XSRETURN
+
+Return from XSUB, indicating number of items on the stack. This is usually
+handled by C<xsubpp>.
+
+ XSRETURN(int x);
+
+=item XSRETURN_EMPTY
+
+Return an empty list from an XSUB immediately.
+
+ XSRETURN_EMPTY;
+
+=item XSRETURN_IV
+
+Return an integer from an XSUB immediately. Uses C<XST_mIV>.
+
+ XSRETURN_IV(IV v);
+
+=item XSRETURN_NO
+
+Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
+
+ XSRETURN_NO;
+
+=item XSRETURN_NV
+
+Return an double from an XSUB immediately. Uses C<XST_mNV>.
+
+ XSRETURN_NV(NV v);
+
+=item XSRETURN_PV
+
+Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
+
+ XSRETURN_PV(char *v);
+
+=item XSRETURN_UNDEF
+
+Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
+
+ XSRETURN_UNDEF;
+
+=item XSRETURN_YES
+
+Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
+
+ XSRETURN_YES;
+
+=item XST_mIV
+
+Place an integer into the specified position C<i> on the stack. The value is
+stored in a new mortal SV.
+
+ XST_mIV( int i, IV v );
+
+=item XST_mNV
+
+Place a double into the specified position C<i> on the stack. The value is
+stored in a new mortal SV.
+
+ XST_mNV( int i, NV v );
+
+=item XST_mNO
+
+Place C<&sv_no> into the specified position C<i> on the stack.
+
+ XST_mNO( int i );
+
+=item XST_mPV
+
+Place a copy of a string into the specified position C<i> on the stack. The
+value is stored in a new mortal SV.
+
+ XST_mPV( int i, char *v );
+
+=item XST_mUNDEF
+
+Place C<&sv_undef> into the specified position C<i> on the stack.
+
+ XST_mUNDEF( int i );
+
+=item XST_mYES
+
+Place C<&sv_yes> into the specified position C<i> on the stack.
+
+ XST_mYES( int i );
+
+=item XS_VERSION
+
+The version identifier for an XS module. This is usually handled
+automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
+
+=item XS_VERSION_BOOTCHECK
+
+Macro to verify that a PM module's $VERSION variable matches the XS module's
+C<XS_VERSION> variable. This is usually handled automatically by
+C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
+
+=item Zero
+
+The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
+destination, C<n> is the number of items, and C<t> is the type.
+
+ (void) Zero( d, n, t );
+
+=back
+
+=head1 EDITOR
+
+Jeff Okamoto <F<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, Spider Boardman, and Ulrich Pfeifer.
+
+API Listing by Dean Roehrich <F<roehrich@cray.com>>.
=head1 DATE
-Version 19: 1995/4/26
+Version 31.3: 1997/3/14
projects / p5sagit/p5-mst-13.2.git / blobdiff