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.
values that can be loaded: an integer value (IV), a double (NV), a string,
(PV), and another scalar (SV).
-The four routines are:
+The six routines are:
SV* newSViv(IV);
SV* newSVnv(double);
- SV* newSVpv(char*, int);
+ SV* newSVpv(const char*, int);
+ SV* newSVpvn(const char*, int);
+ SV* newSVpvf(const char*, ...);
SV* newSVsv(SV*);
-To change the value of an *already-existing* SV, there are five routines:
+To change the value of an *already-existing* SV, there are seven routines:
void sv_setiv(SV*, IV);
+ void sv_setuv(SV*, UV);
void sv_setnv(SV*, double);
- void sv_setpvn(SV*, char*, int)
- void sv_setpv(SV*, char*);
+ void sv_setpv(SV*, const char*);
+ void sv_setpvn(SV*, const char*, int)
+ void sv_setpvf(SV*, const char*, ...);
+ void sv_setpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
void sv_setsv(SV*, SV*);
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 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.
+assigned by using C<sv_setpvn>, C<newSVpvn>, or C<newSVpv>, or you may
+allow Perl to 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.
+
+The arguments of C<sv_setpvf> are processed like C<sprintf>, and the
+formatted output becomes the value.
+
+C<sv_setpvfn> is an analogue of C<vsprintf>, but it allows you to specify
+either a pointer to a variable argument list or the address and length of
+an array of SVs. The last argument points to a boolean; on return, if that
+boolean is true, then locale-specific information has been used to format
+the string, and the string's contents are therefore untrustworthy (see
+L<perlsec>). This pointer may be NULL if that information is not
+important. Note that this function requires you to specify the length of
+the format.
+
+The C<sv_set*()> functions are not generic enough to operate on values
+that have "magic". See L<Magic Virtual Tables> later in this document.
+
+All SVs that contain strings should 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*)
SvNV(SV*)
SvPV(SV*, STRLEN len)
+ SvPV_nolen(SV*)
which will automatically coerce the actual scalar type into an IV, double,
or string.
In the C<SvPV> macro, the length of the string returned is placed into the
-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
-NULs and not be terminated by a NUL.
+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 C<SvPV_nolen> macro.
+Historically the C<SvPV> macro with the global variable C<PL_na> has been
+used in this case. But that can be quite inefficient because C<PL_na> must
+be accessed in thread-local storage in threaded Perl. In any case, remember
+that Perl allows arbitrary strings of data that may both contain NULs and
+might not be terminated by a NUL.
+
+Also remember that C doesn't allow you to safely say C<foo(SvPV(s, len),
+len);>. It might work with your compiler, but it won't work for everyone.
+Break this sort of statement up into separate assignments:
+
+ STRLEN len;
+ char * ptr;
+ ptr = SvPV(len);
+ foo(ptr, len);
-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.
If you want to append something to the end of string stored in an C<SV*>,
you can use the following functions:
- void sv_catpv(SV*, char*);
- void sv_catpvn(SV*, char*, int);
+ void sv_catpv(SV*, const char*);
+ void sv_catpvn(SV*, const char*, STRLEN);
+ void sv_catpvf(SV*, const char*, ...);
+ void sv_catpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
void sv_catsv(SV*, SV*);
The first function calculates the length of the string to be appended by
using C<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.
+yourself. The third function processes its arguments like C<sprintf> and
+appends the formatted output. The fourth function works like C<vsprintf>.
+You can specify the address and length of an array of SVs instead of the
+va_list argument. The fifth 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.
+
+The C<sv_cat*()> functions are not generic enough to operate on values that
+have "magic". See L<Magic Virtual Tables> later in this document.
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.
SvOK(SV*)
-The scalar C<undef> value is stored in an SV instance called C<sv_undef>. Its
+The scalar C<undef> value is stored in an SV instance called C<PL_sv_undef>. Its
address can be used whenever an C<SV*> is needed.
-There are also the two values C<sv_yes> and C<sv_no>, which contain Boolean
-TRUE and FALSE values, respectively. Like C<sv_undef>, their addresses can
+There are also the two values C<PL_sv_yes> and C<PL_sv_no>, which contain Boolean
+TRUE and FALSE values, respectively. Like C<PL_sv_undef>, their addresses can
be used whenever an C<SV*> is needed.
-Do not be fooled into thinking that C<(SV *) 0> is the same as C<&sv_undef>.
+Do not be fooled into thinking that C<(SV *) 0> is the same as C<&PL_sv_undef>.
Take this code:
SV* sv = (SV*) 0;
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
+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<&PL_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 AVs
-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();
AV* av_make(I32 num, SV **ptr);
-The second argument points to an array containing C<num> C<SV*>s. Once the
+The second argument points to an array containing C<num> C<SV*>'s. Once the
AV has been created, the SVs can be destroyed, if so desired.
Once the AV has been created, the following operations are possible on AVs:
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 C<av_fetch> and C<av_store> 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>, and does
+not increment the reference count of C<val>. Thus the caller is responsible
+for taking care of that, and if C<av_store> returns NULL, the caller will
+have to decrement the reference count to avoid a memory leak. 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);
- /* Extend the array to a total of key elements */
+
+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 at least C<key+1>
+elements. If C<key+1> is less than the currently allocated 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.
+See L<Understanding the Magic of Tied Hashes and Arrays> for more
+information on how to use the array access functions on tied arrays.
+
=head2 Working with HVs
To create an HV, you use the following routine:
Once the HV has been created, the following operations are possible on HVs:
- SV** hv_store(HV*, char* key, U32 klen, SV* val, U32 hash);
- SV** hv_fetch(HV*, char* key, U32 klen, I32 lval);
+ SV** hv_store(HV*, const char* key, U32 klen, SV* val, U32 hash);
+ SV** hv_fetch(HV*, const 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 precomputed 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.
+Remember that C<hv_store> and C<hv_fetch> return C<SV**>'s and not just
+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);
+ bool hv_exists(HV*, const char* key, U32 klen);
+ SV* hv_delete(HV*, const 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
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;
- s = key;
- while (i--)
- hash = hash * 33 + *s++;
+ while (klen--)
+ hash = (hash * 33) + *key++;
+ hash = hash + (hash >> 5); /* after 5.6 */
+
+The last step was added in version 5.6 to improve distribution of
+lower bits in the resulting hash value.
+
+See L<Understanding the Magic of Tied Hashes and Arrays> for more
+information on how to use the hash access functions on tied hashes.
+
+=head2 Hash API Extensions
+
+Beginning with version 5.004, the following functions are also supported:
+
+ 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);
+
+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:
+
+ HeKEY(HE* he)
+ HeKLEN(HE* he)
+
+Note that both C<hv_store> and C<hv_store_ent> do not increment the
+reference count of the stored C<val>, which is the caller's responsibility.
+If these functions return a NULL value, the caller will usually have to
+decrement the reference count of C<val> to avoid a memory leak.
=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
+
+ See the sv.h header file for more details.
=head2 Blessed References and Class Objects
SV* sv_bless(SV* sv, HV* stash);
The C<sv> argument must be a reference. The C<stash> argument specifies
-which class the reference will belong to. See the L<"Stashes">
-for information on converting class names into stashes.
+which class the reference will belong to. See
+L<Stashes and Globs> 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.
+point to. If C<classname> is non-null, the SV is blessed into the specified
+class. SV is returned.
- SV* newSVrv(SV* rv, char* classname);
+ SV* newSVrv(SV* rv, const char* classname);
-Copies integer or double into an SV whose reference is rv. SV is blessed
-if classname is non-null.
+Copies integer or double into an SV whose reference is C<rv>. SV is blessed
+if C<classname> is non-null.
- SV* sv_setref_iv(SV* rv, char* classname, IV iv);
- SV* sv_setref_nv(SV* rv, char* classname, NV iv);
+ SV* sv_setref_iv(SV* rv, const char* classname, IV iv);
+ SV* sv_setref_nv(SV* rv, const char* classname, NV iv);
-Copies pointer (I<not a string!>) into an SV whose reference is rv.
-SV is blessed if classname is non-null.
+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.
- SV* sv_setref_pv(SV* rv, char* classname, PV iv);
+ SV* sv_setref_pv(SV* rv, const 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.
+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.
- SV* sv_setref_pvn(SV* rv, char* classname, PV iv, int length);
+ SV* sv_setref_pvn(SV* rv, const char* classname, PV iv, STRLEN length);
- int sv_isa(SV* sv, char* name);
- int sv_isobject(SV* sv);
+Tests whether the SV is blessed into the specified class. It does not
+check inheritance relationships.
-=head1 Creating New Variables
+ int sv_isa(SV* sv, const char* name);
-To create a new Perl variable, which can be accessed from your Perl script,
-use the following routines, depending on the variable type.
-
- SV* perl_get_sv("varname", TRUE);
- AV* perl_get_av("varname", TRUE);
- HV* perl_get_hv("varname", TRUE);
-
-Notice the use of TRUE as the second parameter. The new variable can now
-be set, using the routines appropriate to the data type.
-
-There are additional bits that may be OR'ed with the TRUE argument to enable
-certain extra features. Those bits are:
-
- 0x02 Marks the variable as multiply defined, thus preventing the
- "Identifier <varname> used only once: possible typo" warning.
- 0x04 Issues a "Had to create <varname> unexpectedly" warning if
- the variable didn't actually exist. This is useful if
- you expected the variable to already exist and want to propagate
- this warning back to the user.
-
-If the C<varname> argument does not contain a package specifier, it is
-created in the current package.
-
-=head1 XSUBs and the Argument Stack
-
-The XSUB mechanism is a simple way for Perl programs to access C subroutines.
-An XSUB routine will have a stack that contains the arguments from the Perl
-program, and a way to map from the Perl data structures to a C equivalent.
+Tests whether the SV is a reference to a blessed object.
-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.
+ int sv_isobject(SV* sv);
-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.
+Tests whether the SV is derived from the specified class. SV can be either
+a reference to a blessed object or a string containing a class name. This
+is the function implementing the C<UNIVERSAL::isa> functionality.
-To handle this situation, the PPCODE directive is used and the stack is
-extended using the macro:
+ bool sv_derived_from(SV* sv, const char* name);
- EXTEND(sp, num);
+To check if you've got an object derived from a specific class you have
+to write:
-where C<sp> is the stack pointer, and C<num> is the number of elements the
-stack should be extended by.
+ if (sv_isobject(sv) && sv_derived_from(sv, class)) { ... }
-Now that there is room on the stack, values can be pushed on it using the
-macros to push IVs, doubles, strings, and SV pointers respectively:
+=head2 Creating New Variables
- PUSHi(IV)
- PUSHn(double)
- PUSHp(char*, I32)
- PUSHs(SV*)
+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.
-And now the Perl program calling C<tzname>, the two values will be assigned
-as in:
+ SV* perl_get_sv("package::varname", TRUE);
+ AV* perl_get_av("package::varname", TRUE);
+ HV* perl_get_hv("package::varname", TRUE);
- ($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 L<perlxs>.
-
-=head1 Mortality
-
-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).
-
-Add cruft about reference counts.
- int SvREFCNT(SV* sv);
- void SvREFCNT_inc(SV* sv);
- void SvREFCNT_dec(SV* sv);
-
-In the above example with C<tzname>, we needed to create two new SVs to push
-onto the argument stack, that being the two strings. However, we don't want
-these new SVs to stick around forever because they will eventually be
-copied into the SVs that hold the two scalar variables.
+Notice the use of TRUE as the second parameter. The new variable can now
+be set, using the routines appropriate to the data type.
-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.
+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
+ "Name <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. SVs,
+AVs, or HVs (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 xVs. 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 xVs 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 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 SVs -- AVs and HVs can be made mortal
-by passing their address (and casting them to C<SV*>) to the C<sv_2mortal> or
-C<sv_mortalcopy> routines.
+The mortal routines are not just for SVs -- AVs and HVs can be
+made mortal by passing their address (type-casted 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.
+=head2 Stashes and Globs
-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
-
-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:
+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
- File Handle
- Directory Handle
+ I/O 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 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 "PL_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 PL_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:
- HV* gv_stashpv(char* name, I32 create)
+ HV* gv_stashpv(const char* name, I32 create)
HV* gv_stashsv(SV*, I32 create)
The first function takes a literal string, the second uses the string stored
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 SVs
+
+Scalar variables normally contain only one type of value, an integer,
+double, pointer, or reference. Perl will automatically convert the
+actual scalar data from the stored type into the requested type.
+
+Some scalar variables contain more than one type of scalar data. For
+example, the variable 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.]
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>.
+linked list of C<struct magic>'s, typedef'ed to C<MAGIC>.
struct magic {
MAGIC* mg_moremagic;
Perl adds magic to an SV using the sv_magic function:
- void sv_magic(SV* sv, SV* obj, int how, char* name, I32 namlen);
+ void sv_magic(SV* sv, SV* obj, int how, const char* name, I32 namlen);
The C<sv> argument is a pointer to the SV that is to acquire a new magical
feature.
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 magic, typically the name of a variable. C<namlem> is stored in the
-C<mg_len> field and if C<name> is non-null and C<namlem> E<gt>= 0 a malloc'd
+The C<name> and C<namlen> arguments are used to associate a string with
+the magic, typically the name of a variable. C<namlen> is stored in the
+C<mg_len> field and if C<name> is non-null and C<namlen> >= 0 a malloc'd
copy of the name is stored in C<mg_ptr> field.
The sv_magic function uses C<how> to determine which, if any, predefined
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
count of the C<obj> object is incremented. If it is the same, or if
-the C<how> argument is "#", or if it is a null pointer, then C<obj> is
+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>:
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???
+ mg_type MGVTBL Type of magic
+ ------- ------ ----------------------------
+ \0 vtbl_sv Special scalar variable
+ A vtbl_amagic %OVERLOAD hash
+ a vtbl_amagicelem %OVERLOAD hash element
+ c (none) Holds overload table (AMT) on stash
+ B vtbl_bm Boyer-Moore (fast string search)
E vtbl_env %ENV hash
e vtbl_envelem %ENV hash element
- g vtbl_mglob Regexp /g flag???
+ f vtbl_fm Formline ('compiled' format)
+ g vtbl_mglob m//g target / study()ed string
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
+ k vtbl_nkeys scalar(keys()) lvalue
+ L (none) Debugger %_<filename
+ l vtbl_dbline Debugger %_<filename element
+ 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
+ S vtbl_sig %SIG hash
+ s vtbl_sigelem %SIG 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 $. scalar variable
- ~ Reserved for extensions, but multiple extensions may clash
-
-When an upper-case and lower-case letter both exist in the table, then the
-upper-case letter is used to represent some kind of composite type (a list
-or a hash), and the lower-case letter is used to represent an element of
+ U vtbl_uvar Available for use by extensions
+ v vtbl_vec vec() lvalue
+ x vtbl_substr substr() lvalue
+ y vtbl_defelem Shadow "foreach" iterator variable /
+ smart parameter vivification
+ * vtbl_glob GV (typeglob)
+ # vtbl_arylen Array length ($#ary)
+ . vtbl_pos pos() lvalue
+ ~ (none) Available for use by extensions
+
+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 '~' and 'U' magic types are 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).
+
+Similarly, 'U' magic can be used much like tie() to call a C function
+any time a scalar's value is used or changed. The C<MAGIC>'s
+C<mg_ptr> field points to a C<ufuncs> structure:
+
+ struct ufuncs {
+ I32 (*uf_val)(IV, SV*);
+ I32 (*uf_set)(IV, SV*);
+ IV uf_index;
+ };
+
+When the SV is read from or written to, the C<uf_val> or C<uf_set>
+function will be called with C<uf_index> as the first arg and a
+pointer to the SV as the second. A simple example of how to add 'U'
+magic is shown below. Note that the ufuncs structure is copied by
+sv_magic, so you can safely allocate it on the stack.
+
+ void
+ Umagic(sv)
+ SV *sv;
+ PREINIT:
+ struct ufuncs uf;
+ CODE:
+ uf.uf_val = &my_get_fn;
+ uf.uf_set = &my_set_fn;
+ uf.uf_index = 0;
+ sv_magic(sv, 0, 'U', (char*)&uf, sizeof(uf));
+
+Note that because multiple extensions may be using '~' or 'U' magic,
+it is important for extensions to take extra care to avoid conflict.
+Typically only using the magic on objects blessed into the same class
+as the extension is sufficient. For '~' magic, it may also be
+appropriate to add an I32 'signature' at the top of the private data
+area and check that.
+
+Also note that the C<sv_set*()> and C<sv_cat*()> functions described
+earlier do B<not> invoke 'set' magic on their targets. This must
+be done by the user either by calling the C<SvSETMAGIC()> macro after
+calling these functions, or by using one of the C<sv_set*_mg()> or
+C<sv_cat*_mg()> functions. Similarly, generic C code must call the
+C<SvGETMAGIC()> macro to invoke any 'get' magic if they use an SV
+obtained from external sources in functions that don't handle magic.
+L<API LISTING> later in this document identifies such functions.
+For example, calls to the C<sv_cat*()> functions typically need to be
+followed by C<SvSETMAGIC()>, but they don't need a prior C<SvGETMAGIC()>
+since their implementation handles 'get' magic.
+
=head2 Finding Magic
MAGIC* mg_find(SV*, int type); /* Finds the magic pointer of that type */
This routine returns a pointer to the C<MAGIC> structure stored in the SV.
If the SV does not have that magical feature, C<NULL> is returned. Also,
-if the SV is not of type SVt_PVMG, Perl may core-dump.
+if the SV is not of type SVt_PVMG, Perl may core dump.
- int mg_copy(SV* sv, SV* nsv, char* key, STRLEN klen);
+ int mg_copy(SV* sv, SV* nsv, const 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.
+
+=head2 Understanding the Magic of Tied Hashes and Arrays
+
+Tied hashes and arrays are magical beasts of the 'P' magic type.
+
+WARNING: As of the 5.004 release, proper usage of the array and hash
+access functions requires understanding a few caveats. Some
+of these caveats are actually considered bugs in the API, to be fixed
+in later releases, and are bracketed with [MAYCHANGE] below. If
+you find yourself actually applying such information in this section, be
+aware that the behavior may change in the future, umm, without warning.
+
+The perl tie function associates a variable with an object that implements
+the various GET, SET etc methods. To perform the equivalent of the perl
+tie function from an XSUB, you must mimic this behaviour. The code below
+carries out the necessary steps - firstly it creates a new hash, and then
+creates a second hash which it blesses into the class which will implement
+the tie methods. Lastly it ties the two hashes together, and returns a
+reference to the new tied hash. Note that the code below does NOT call the
+TIEHASH method in the MyTie class -
+see L<Calling Perl Routines from within C Programs> for details on how
+to do this.
+
+ SV*
+ mytie()
+ PREINIT:
+ HV *hash;
+ HV *stash;
+ SV *tie;
+ CODE:
+ hash = newHV();
+ tie = newRV_noinc((SV*)newHV());
+ stash = gv_stashpv("MyTie", TRUE);
+ sv_bless(tie, stash);
+ hv_magic(hash, tie, 'P');
+ RETVAL = newRV_noinc(hash);
+ OUTPUT:
+ RETVAL
+
+The C<av_store> function, when given a tied array argument, merely
+copies the magic of the array onto the value to be "stored", using
+C<mg_copy>. It may also return NULL, indicating that the value did not
+actually need to be stored in the array. [MAYCHANGE] After a call to
+C<av_store> on a tied array, the caller will usually need to call
+C<mg_set(val)> to actually invoke the perl level "STORE" method on the
+TIEARRAY object. If C<av_store> did return NULL, a call to
+C<SvREFCNT_dec(val)> will also be usually necessary to avoid a memory
+leak. [/MAYCHANGE]
+
+The previous paragraph is applicable verbatim to tied hash access using the
+C<hv_store> and C<hv_store_ent> functions as well.
+
+C<av_fetch> and the corresponding hash functions C<hv_fetch> and
+C<hv_fetch_ent> actually return an undefined mortal value whose magic
+has been initialized using C<mg_copy>. Note the value so returned does not
+need to be deallocated, as it is already mortal. [MAYCHANGE] But you will
+need to call C<mg_get()> on the returned value in order to actually invoke
+the perl level "FETCH" method on the underlying TIE object. Similarly,
+you may also call C<mg_set()> on the return value after possibly assigning
+a suitable value to it using C<sv_setsv>, which will invoke the "STORE"
+method on the TIE object. [/MAYCHANGE]
+
+[MAYCHANGE]
+In other words, the array or hash fetch/store functions don't really
+fetch and store actual values in the case of tied arrays and hashes. They
+merely call C<mg_copy> to attach magic to the values that were meant to be
+"stored" or "fetched". Later calls to C<mg_get> and C<mg_set> actually
+do the job of invoking the TIE methods on the underlying objects. Thus
+the magic mechanism currently implements a kind of lazy access to arrays
+and hashes.
+
+Currently (as of perl version 5.004), use of the hash and array access
+functions requires the user to be aware of whether they are operating on
+"normal" hashes and arrays, or on their tied variants. The API may be
+changed to provide more transparent access to both tied and normal data
+types in future versions.
+[/MAYCHANGE]
+
+You would do well to understand that the TIEARRAY and TIEHASH interfaces
+are mere sugar to invoke some perl method calls while using the uniform hash
+and array syntax. The use of this sugar imposes some overhead (typically
+about two to four extra opcodes per FETCH/STORE operation, in addition to
+the creation of all the mortal variables required to invoke the methods).
+This overhead will be comparatively small if the TIE methods are themselves
+substantial, but if they are only a few statements long, the overhead
+will not be insignificant.
+
+=head2 Localizing changes
+
+Perl has a very handy construction
+
+ {
+ local $var = 2;
+ ...
+ }
+
+This construction is I<approximately> equivalent to
+
+ {
+ my $oldvar = $var;
+ $var = 2;
+ ...
+ $var = $oldvar;
+ }
+
+The biggest difference is that the first construction would
+reinstate the initial value of $var, irrespective of how control exits
+the block: C<goto>, C<return>, C<die>/C<eval> etc. It is a little bit
+more efficient as well.
+
+There is a way to achieve a similar task from C via Perl API: create a
+I<pseudo-block>, and arrange for some changes to be automatically
+undone at the end of it, either explicit, or via a non-local exit (via
+die()). A I<block>-like construct is created by a pair of
+C<ENTER>/C<LEAVE> macros (see L<perlcall/"Returning a Scalar">).
+Such a construct may be created specially for some important localized
+task, or an existing one (like boundaries of enclosing Perl
+subroutine/block, or an existing pair for freeing TMPs) may be
+used. (In the second case the overhead of additional localization must
+be almost negligible.) Note that any XSUB is automatically enclosed in
+an C<ENTER>/C<LEAVE> pair.
+
+Inside such a I<pseudo-block> the following service is available:
+
+=over
+
+=item C<SAVEINT(int i)>
-=head1 Double-Typed SVs
+=item C<SAVEIV(IV i)>
-Scalar variables normally contain only one type of value, an integer,
-double, pointer, or reference. Perl will automatically convert the
-actual scalar data from the stored type into the requested type.
+=item C<SAVEI32(I32 i)>
-Some scalar variables contain more than one type of scalar data. For
-example, the variable C<$!> contains either the numeric value of C<errno>
-or its string equivalent from either C<strerror> or C<sys_errlist[]>.
+=item C<SAVELONG(long i)>
-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:
+These macros arrange things to restore the value of integer variable
+C<i> at the end of enclosing I<pseudo-block>.
- SvIOK_on
- SvNOK_on
- SvPOK_on
- SvROK_on
+=item C<SAVESPTR(s)>
-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.
+=item C<SAVEPPTR(p)>
-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:
+These macros arrange things to restore the value of pointers C<s> and
+C<p>. C<s> must be a pointer of a type which survives conversion to
+C<SV*> and back, C<p> should be able to survive conversion to C<char*>
+and back.
- extern int dberror;
- extern char *dberror_list;
+=item C<SAVEFREESV(SV *sv)>
- SV* sv = perl_get_sv("dberror", TRUE);
- sv_setiv(sv, (IV) dberror);
- sv_setpv(sv, dberror_list[dberror]);
- SvIOK_on(sv);
+The refcount of C<sv> would be decremented at the end of
+I<pseudo-block>. This is similar to C<sv_2mortal>, which should (?) be
+used instead.
-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>.
+=item C<SAVEFREEOP(OP *op)>
+
+The C<OP *> is op_free()ed at the end of I<pseudo-block>.
+
+=item C<SAVEFREEPV(p)>
+
+The chunk of memory which is pointed to by C<p> is Safefree()ed at the
+end of I<pseudo-block>.
+
+=item C<SAVECLEARSV(SV *sv)>
+
+Clears a slot in the current scratchpad which corresponds to C<sv> at
+the end of I<pseudo-block>.
+
+=item C<SAVEDELETE(HV *hv, char *key, I32 length)>
+
+The key C<key> of C<hv> is deleted at the end of I<pseudo-block>. The
+string pointed to by C<key> is Safefree()ed. If one has a I<key> in
+short-lived storage, the corresponding string may be reallocated like
+this:
+
+ SAVEDELETE(PL_defstash, savepv(tmpbuf), strlen(tmpbuf));
+
+=item C<SAVEDESTRUCTOR(f,p)>
+
+At the end of I<pseudo-block> the function C<f> is called with the
+only argument (of type C<void*>) C<p>.
+
+=item C<SAVESTACK_POS()>
+
+The current offset on the Perl internal stack (cf. C<SP>) is restored
+at the end of I<pseudo-block>.
+
+=back
+
+The following API list contains functions, thus one needs to
+provide pointers to the modifiable data explicitly (either C pointers,
+or Perlish C<GV *>s). Where the above macros take C<int>, a similar
+function takes C<int *>.
+
+=over
+
+=item C<SV* save_scalar(GV *gv)>
+
+Equivalent to Perl code C<local $gv>.
+
+=item C<AV* save_ary(GV *gv)>
+
+=item C<HV* save_hash(GV *gv)>
+
+Similar to C<save_scalar>, but localize C<@gv> and C<%gv>.
+
+=item C<void save_item(SV *item)>
+
+Duplicates the current value of C<SV>, on the exit from the current
+C<ENTER>/C<LEAVE> I<pseudo-block> will restore the value of C<SV>
+using the stored value.
+
+=item C<void save_list(SV **sarg, I32 maxsarg)>
+
+A variant of C<save_item> which takes multiple arguments via an array
+C<sarg> of C<SV*> of length C<maxsarg>.
+
+=item C<SV* save_svref(SV **sptr)>
+
+Similar to C<save_scalar>, but will reinstate a C<SV *>.
+
+=item C<void save_aptr(AV **aptr)>
+
+=item C<void save_hptr(HV **hptr)>
+
+Similar to C<save_svref>, but localize C<AV *> and C<HV *>.
+
+=back
+
+The C<Alias> module implements localization of the basic types within the
+I<caller's scope>. People who are interested in how to localize things in
+the containing scope should take a look there too.
+
+=head1 Subroutines
+
+=head2 XSUBs and the Argument Stack
-=head1 Calling Perl Routines from within C Programs
+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 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.
+
+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.
+
+To handle this situation, the PPCODE directive is used and the stack is
+extended using the macro:
+
+ EXTEND(SP, num);
+
+where C<SP> is the macro that represents the local copy of the stack pointer,
+and C<num> is the number of elements the stack should be extended by.
+
+Now that there is room on the stack, values can be pushed on it using the
+macros to push IVs, doubles, strings, and SV pointers respectively:
+
+ PUSHi(IV)
+ PUSHn(double)
+ PUSHp(char*, I32)
+ PUSHs(SV*)
+
+And now the Perl program calling C<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. 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:
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**);
+ I32 perl_call_pv(const char*, I32);
+ I32 perl_call_method(const char*, I32);
+ I32 perl_call_argv(const char*, I32, register char**);
The routine most often used is C<perl_call_sv>. The C<SV*> argument
contains either the name of the Perl subroutine to be called, or a
functions:
dSP
+ SP
PUSHMARK()
PUTBACK
SPAGAIN
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.
+All memory meant to be used with the Perl API functions should be manipulated
+using the macros described in this section. The macros provide the necessary
+transparency between differences in the actual malloc implementation that is
+used within perl.
+
+It is suggested that you enable 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).
+=head2 PerlIO
+
+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.
+
+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 SVs 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 SVs 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 OPs and I<target>s is not 1-to-1. Different
+OPs 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 reflects 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 are 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. At 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 complications 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 The Perl Internal API
+
+WARNING: This information is subject to radical changes prior to
+the Perl 5.6 release. Use with caution.
+
+=head2 Background and PERL_IMPLICIT_CONTEXT
+
+The Perl interpreter can be regarded as a closed box: it has an API
+for feeding it code or otherwise making it do things, but it also has
+functions for its own use. This smells a lot like an object, and
+there are ways for you to build Perl so that you can have multiple
+interpreters, with one interpreter represented either as a C++ object,
+a C structure, or inside a thread. The thread, the C structure, or
+the C++ object will contain all the context, the state of that
+interpreter.
+
+Three macros control the major Perl build flavors: MULTIPLICITY,
+USE_THREADS and PERL_OBJECT. The MULTIPLICITY build has a C structure
+that packages all the interpreter state, there is a similar thread-specific
+data structure under USE_THREADS, and the PERL_OBJECT build has a C++
+class to maintain interpreter state. In all three cases,
+PERL_IMPLICIT_CONTEXT is also normally defined, and enables the
+support for passing in a "hidden" first argument that represents all three
+data structures.
+
+All this obviously requires a way for the Perl internal functions to be
+C++ methods, subroutines taking some kind of structure as the first
+argument, or subroutines taking nothing as the first argument. To
+enable these three very different ways of building the interpreter,
+the Perl source (as it does in so many other situations) makes heavy
+use of macros and subroutine naming conventions.
+
+First problem: deciding which functions will be public API functions and
+which will be private. Those functions whose names begin C<Perl_> are
+public, and those whose names begin C<S_> are private (think "S" for
+"secret" or "static").
+
+Some functions have no prefix (e.g., restore_rsfp in toke.c). These
+are not parts of the object or pseudo-structure because you need to
+pass pointers to them to other subroutines.
+
+Second problem: there must be a syntax so that the same subroutine
+declarations and calls can pass a structure as their first argument,
+or pass nothing. To solve this, the subroutines are named and
+declared in a particular way. Here's a typical start of a static
+function used within the Perl guts:
+
+ STATIC void
+ S_incline(pTHX_ char *s)
+
+STATIC becomes "static" in C, and is #define'd to nothing in C++.
+
+A public function (i.e. part of the internal API, but not necessarily
+sanctioned for use in extensions) begins like this:
+
+ void
+ Perl_sv_setsv(pTHX_ SV* dsv, SV* ssv)
+
+C<pTHX_> is one of a number of macros (in perl.h) that hide the
+details of the interpreter's context. THX stands for "thread", "this",
+or "thingy", as the case may be. (And no, George Lucas is not involved. :-)
+The first character could be 'p' for a B<p>rototype, 'a' for B<a>rgument,
+or 'd' for B<d>eclaration.
+
+When Perl is built without PERL_IMPLICIT_CONTEXT, there is no first
+argument containing the interpreter's context. The trailing underscore
+in the pTHX_ macro indicates that the macro expansion needs a comma
+after the context argument because other arguments follow it. If
+PERL_IMPLICIT_CONTEXT is not defined, pTHX_ will be ignored, and the
+subroutine is not prototyped to take the extra argument. The form of the
+macro without the trailing underscore is used when there are no additional
+explicit arguments.
+
+When a core function calls another, it must pass the context. This
+is normally hidden via macros. Consider C<sv_setsv>. It expands
+something like this:
+
+ ifdef PERL_IMPLICIT_CONTEXT
+ define sv_setsv(a,b) Perl_sv_setsv(aTHX_ a, b)
+ /* can't do this for vararg functions, see below */
+ else
+ define sv_setsv Perl_sv_setsv
+ endif
+
+This works well, and means that XS authors can gleefully write:
+
+ sv_setsv(foo, bar);
+
+and still have it work under all the modes Perl could have been
+compiled with.
+
+Under PERL_OBJECT in the core, that will translate to either:
+
+ CPerlObj::Perl_sv_setsv(foo,bar); # in CPerlObj functions,
+ # C++ takes care of 'this'
+ or
+
+ pPerl->Perl_sv_setsv(foo,bar); # in truly static functions,
+ # see objXSUB.h
+
+Under PERL_OBJECT in extensions (aka PERL_CAPI), or under
+MULTIPLICITY/USE_THREADS w/ PERL_IMPLICIT_CONTEXT in both core
+and extensions, it will be:
+
+ Perl_sv_setsv(aTHX_ foo, bar); # the canonical Perl "API"
+ # for all build flavors
+
+This doesn't work so cleanly for varargs functions, though, as macros
+imply that the number of arguments is known in advance. Instead we
+either need to spell them out fully, passing C<aTHX_> as the first
+argument (the Perl core tends to do this with functions like
+Perl_warner), or use a context-free version.
+
+The context-free version of Perl_warner is called
+Perl_warner_nocontext, and does not take the extra argument. Instead
+it does dTHX; to get the context from thread-local storage. We
+C<#define warner Perl_warner_nocontext> so that extensions get source
+compatibility at the expense of performance. (Passing an arg is
+cheaper than grabbing it from thread-local storage.)
+
+You can ignore [pad]THX[xo] when browsing the Perl headers/sources.
+Those are strictly for use within the core. Extensions and embedders
+need only be aware of [pad]THX.
+
+=head2 How do I use all this in extensions?
+
+When Perl is built with PERL_IMPLICIT_CONTEXT, extensions that call
+any functions in the Perl API will need to pass the initial context
+argument somehow. The kicker is that you will need to write it in
+such a way that the extension still compiles when Perl hasn't been
+built with PERL_IMPLICIT_CONTEXT enabled.
+
+There are three ways to do this. First, the easy but inefficient way,
+which is also the default, in order to maintain source compatibility
+with extensions: whenever XSUB.h is #included, it redefines the aTHX
+and aTHX_ macros to call a function that will return the context.
+Thus, something like:
+
+ sv_setsv(asv, bsv);
+
+in your extesion will translate to this when PERL_IMPLICIT_CONTEXT is
+in effect:
+
+ Perl_sv_setsv(GetPerlInterpreter(), asv, bsv);
+
+or to this otherwise:
+
+ Perl_sv_setsv(asv, bsv);
+
+You have to do nothing new in your extension to get this; since
+the Perl library provides GetPerlInterpreter(), it will all just
+work.
+
+The second, more efficient way is to use the following template for
+your Foo.xs:
+
+ #define PERL_NO_GET_CONTEXT /* we want efficiency */
+ #include "EXTERN.h"
+ #include "perl.h"
+ #include "XSUB.h"
+
+ static my_private_function(int arg1, int arg2);
+
+ static SV *
+ my_private_function(int arg1, int arg2)
+ {
+ dTHX; /* fetch context */
+ ... call many Perl API functions ...
+ }
+
+ [... etc ...]
+
+ MODULE = Foo PACKAGE = Foo
+
+ /* typical XSUB */
+
+ void
+ my_xsub(arg)
+ int arg
+ CODE:
+ my_private_function(arg, 10);
+
+Note that the only two changes from the normal way of writing an
+extension is the addition of a C<#define PERL_NO_GET_CONTEXT> before
+including the Perl headers, followed by a C<dTHX;> declaration at
+the start of every function that will call the Perl API. (You'll
+know which functions need this, because the C compiler will complain
+that there's an undeclared identifier in those functions.) No changes
+are needed for the XSUBs themselves, because the XS() macro is
+correctly defined to pass in the implicit context if needed.
+
+The third, even more efficient way is to ape how it is done within
+the Perl guts:
+
+
+ #define PERL_NO_GET_CONTEXT /* we want efficiency */
+ #include "EXTERN.h"
+ #include "perl.h"
+ #include "XSUB.h"
+
+ /* pTHX_ only needed for functions that call Perl API */
+ static my_private_function(pTHX_ int arg1, int arg2);
+
+ static SV *
+ my_private_function(pTHX_ int arg1, int arg2)
+ {
+ /* dTHX; not needed here, because THX is an argument */
+ ... call Perl API functions ...
+ }
+
+ [... etc ...]
+
+ MODULE = Foo PACKAGE = Foo
+
+ /* typical XSUB */
+
+ void
+ my_xsub(arg)
+ int arg
+ CODE:
+ my_private_function(aTHX_ arg, 10);
+
+This implementation never has to fetch the context using a function
+call, since it is always passed as an extra argument. Depending on
+your needs for simplicity or efficiency, you may mix the previous
+two approaches freely.
+
+Never add a comma after C<pTHX> yourself--always use the form of the
+macro with the underscore for functions that take explicit arguments,
+or the form without the argument for functions with no explicit arguments.
+
+=head2 Future Plans and PERL_IMPLICIT_SYS
+
+Just as PERL_IMPLICIT_CONTEXT provides a way to bundle up everything
+that the interpreter knows about itself and pass it around, so too are
+there plans to allow the interpreter to bundle up everything it knows
+about the environment it's running on. This is enabled with the
+PERL_IMPLICIT_SYS macro. Currently it only works with PERL_OBJECT,
+but is mostly there for MULTIPLICITY and USE_THREADS (see inside
+iperlsys.h).
+
+This allows the ability to provide an extra pointer (called the "host"
+environment) for all the system calls. This makes it possible for
+all the system stuff to maintain their own state, broken down into
+seven C structures. These are thin wrappers around the usual system
+calls (see win32/perllib.c) for the default perl executable, but for a
+more ambitious host (like the one that would do fork() emulation) all
+the extra work needed to pretend that different interpreters are
+actually different "processes", would be done here.
+
+The Perl engine/interpreter and the host are orthogonal entities.
+There could be one or more interpreters in a process, and one or
+more "hosts", with free association between them.
+
=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
+used by extension writers. The interfaces of any functions that are not
+listed here are subject to change without notice. For this reason,
+blindly using functions listed in proto.h is to be avoided when writing
extensions.
-=over 8
+Note that all Perl API global variables must be referenced with the C<PL_>
+prefix. Some macros are provided for compatibility with the older,
+unadorned names, but this support may be disabled in a future release.
-=item AvFILL
+The sort order of the listing is case insensitive, with any
+occurrences of '_' ignored for the purpose of sorting.
-See C<av_len>.
+=over 8
=item av_clear
-Clears an array, making it empty.
+Clears an array, making it empty. Does not free the memory used by the
+array itself.
- void av_clear _((AV* ar));
+ 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));
+ void av_extend (AV* ar, I32 key)
=item av_fetch
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));
+See L<Understanding the Magic of Tied Hashes and Arrays> for more
+information on how to use this function on tied arrays.
+
+ SV** av_fetch (AV* ar, I32 key, I32 lval)
+
+=item AvFILL
+
+Same as C<av_len()>. Deprecated, use C<av_len()> instead.
=item av_len
Returns the highest index in the array. Returns -1 if the array is empty.
- I32 av_len _((AV* ar));
+ 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 refcount of 1.
+will have a reference count of 1.
- AV* av_make _((I32 size, SV** svp));
+ 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
+Pops an SV off the end of the array. Returns C<&PL_sv_undef> if the array is
empty.
- SV* av_pop _((AV* ar));
+ 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));
+ void av_push (AV* ar, SV* val)
=item av_shift
Shifts an SV off the beginning of the array.
- SV* av_shift _((AV* ar));
+ 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*>.
+return value will be NULL if the operation failed or if the value did not
+need to be actually stored within the array (as in the case of tied arrays).
+Otherwise it can be dereferenced to get the original C<SV*>. Note that the
+caller is responsible for suitably incrementing the reference count of C<val>
+before the call, and decrementing it if the function returned NULL.
+
+See L<Understanding the Magic of Tied Hashes and Arrays> for more
+information on how to use this function on tied arrays.
- SV** av_store _((AV* ar, I32 key, SV* val));
+ SV** av_store (AV* ar, I32 key, SV* val)
=item av_undef
-Undefines the array.
+Undefines the array. Frees the memory used by the array itself.
- void av_undef _((AV* ar));
+ 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.
+Unshift the given number of C<undef> values onto the beginning of the
+array. The array will grow automatically to accommodate the addition.
+You must then use C<av_store> to assign values to these new elements.
- void av_unshift _((AV* ar, I32 num));
+ void av_unshift (AV* ar, I32 num)
=item CLASS
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.
+the type. May fail on overlapping copies. See also C<Move>.
- (void) Copy( s, d, n, t );
+ void Copy( s, d, n, t )
=item croak
Returns the stash of the CV.
- HV * CvSTASH( SV* sv )
+ HV* CvSTASH( SV* sv )
-=item DBsingle
+=item PL_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>.
+variable which corresponds to Perl's $DB::single variable. See C<PL_DBsub>.
-=item DBsub
+=item PL_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>.
+variable which corresponds to Perl's $DB::sub variable. See C<PL_DBsingle>.
The sub name can be found by
- SvPV( GvSV( DBsub ), na )
+ SvPV( GvSV( PL_DBsub ), len )
-=item DBtrace
+=item PL_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>.
+variable. See C<PL_DBsingle>.
=item dMARK
Saves the original stack mark for the XSUB. See C<ORIGMARK>.
-=item dowarn
+=item PL_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>.
+Declares a local copy of perl's stack pointer for the XSUB, available via
+the C<SP> macro. See C<SP>.
=item dXSARGS
Sets up the C<ix> variable for an XSUB which has aliases. This is usually
handled automatically by C<xsubpp>.
-=item dXSI32
+=item do_binmode
-Sets up the C<ix> variable for an XSUB which has aliases. This is usually
-handled automatically by C<xsubpp>.
+Switches filehandle to binmode. C<iotype> is what C<IoTYPE(io)> would
+contain.
+
+ do_binmode(fp, iotype, TRUE);
=item ENTER
Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
- ENTER;
+ ENTER;
+
+=item EXTEND
+
+Used to extend the argument stack for an XSUB's return values.
+
+ EXTEND( sp, int x )
+
+=item fbm_compile
+
+Analyses the string in order to make fast searches on it using fbm_instr() --
+the Boyer-Moore algorithm.
+
+ void fbm_compile(SV* sv, U32 flags)
+
+=item fbm_instr
+
+Returns the location of the SV in the string delimited by C<str> and
+C<strend>. It returns C<Nullch> if the string can't be found. The
+C<sv> does not have to be fbm_compiled, but the search will not be as
+fast then.
+
+ char* fbm_instr(char *str, char *strend, SV *sv, U32 flags)
+
+=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_V>, 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
+
+A backward-compatible version of C<GIMME_V> which can only return
+C<G_SCALAR> or C<G_ARRAY>; in a void context, it returns C<G_SCALAR>.
+
+=item GIMME_V
+
+The XSUB-writer's equivalent to Perl's C<wantarray>. Returns
+C<G_VOID>, C<G_SCALAR> or C<G_ARRAY> for void, scalar or array
+context, respectively.
+
+=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_V>, 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
+accessible 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, const char* name, STRLEN len, I32 level)
+
+=item gv_fetchmethod
+
+=item gv_fetchmethod_autoload
+
+Returns the glob which contains the subroutine to call to invoke the
+method on the C<stash>. In fact in the presence of autoloading this may
+be the glob for "AUTOLOAD". In this case the corresponding variable
+$AUTOLOAD is already setup.
+
+The third parameter of C<gv_fetchmethod_autoload> determines whether AUTOLOAD
+lookup is performed if the given method is not present: non-zero means
+yes, look for AUTOLOAD; zero means no, don't look for AUTOLOAD. Calling
+C<gv_fetchmethod> is equivalent to calling C<gv_fetchmethod_autoload> with a
+non-zero C<autoload> parameter.
+
+These functions grant C<"SUPER"> token as a prefix of the method name.
+
+Note that if you want to keep the returned 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.
+
+These functions have 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 these functions.
+
+ GV* gv_fetchmethod (HV* stash, const char* name)
+ GV* gv_fetchmethod_autoload (HV* stash, const char* name, I32 autoload)
+
+=item G_VOID
+
+Used to indicate void context. See C<GIMME_V> and L<perlcall>.
+
+=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 (const 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 EXTEND
+=item GvSV
-Used to extend the argument stack for an XSUB's return values.
+Return the SV from the GV.
- EXTEND( sp, int x );
+=item HEf_SVKEY
-=item FREETMPS
+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).
-Closing bracket for temporaries on a callback. See C<SAVETMPS> and
-L<perlcall>.
+=item HeHASH
- FREETMPS;
+Returns the computed hash stored in the hash entry.
-=item G_ARRAY
+ U32 HeHASH(HE* he)
-Used to indicate array context. See C<GIMME> and L<perlcall>.
+=item HeKEY
-=item G_DISCARD
+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.
-Indicates that arguments returned from a callback should be discarded. See
-L<perlcall>.
+ char* HeKEY(HE* he)
-=item G_EVAL
+=item HeKLEN
-Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
+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.
-=item GIMME
+ int HeKLEN(HE* he)
-The XSUB-writer's equivalent to Perl's C<wantarray>. Returns C<G_SCALAR> or
-C<G_ARRAY> for scalar or array context.
+=item HePV
-=item G_NOARGS
+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<PL_na>, though this is rather less
+efficient than using a local variable. 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.
-Indicates that no arguments are being sent to a callback. See L<perlcall>.
+ char* HePV(HE* he, STRLEN len)
-=item G_SCALAR
+=item HeSVKEY
-Used to indicate scalar context. See C<GIMME> and L<perlcall>.
+Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
+does not contain an C<SV*> key.
-=item gv_stashpv
+ HeSVKEY(HE* he)
-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.
+=item HeSVKEY_force
- HV* gv_stashpv _((char* name, I32 create));
+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.
-=item gv_stashsv
+ HeSVKEY_force(HE* he)
-Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
+=item HeSVKEY_set
- HV* gv_stashsv _((SV* sv, I32 create));
+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*>.
-=item GvSV
+ HeSVKEY_set(HE* he, SV* sv)
-Return the SV from the GV.
+=item HeVAL
-=item he_free
+Returns the value slot (type C<SV*>) stored in the hash entry.
-Releases a hash entry from an iterator. See C<hv_iternext>.
+ HeVAL(HE* he)
=item hv_clear
Clears a hash, making it empty.
- void hv_clear _((HV* tb));
+ void hv_clear (HV* tb)
=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
+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));
+ SV* hv_delete (HV* tb, const 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 precomputed
+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));
+ bool hv_exists (HV* tb, const char* key, U32 klen)
+
+=item hv_exists_ent
+
+Returns a boolean indicating whether the specified hash key exists. C<hash>
+can be a valid precomputed hash value, or 0 to ask for it to be computed.
+
+ bool hv_exists_ent (HV* tb, SV* key, U32 hash)
=item hv_fetch
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));
+See L<Understanding the Magic of Tied Hashes and Arrays> for more
+information on how to use this function on tied hashes.
+
+ SV** hv_fetch (HV* tb, const 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 precomputed 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.
+
+See L<Understanding the Magic of Tied Hashes and Arrays> for more
+information on how to use this function on tied hashes.
+
+ HE* hv_fetch_ent (HV* tb, SV* key, I32 lval, U32 hash)
=item hv_iterinit
Prepares a starting point to traverse a hash table.
- I32 hv_iterinit _((HV* tb));
+ I32 hv_iterinit (HV* tb)
+
+Returns the number of keys in the hash (i.e. the same as C<HvKEYS(tb)>).
+The return value is currently only meaningful for hashes without tie
+magic.
+
+NOTE: Before version 5.004_65, C<hv_iterinit> used to return the number
+of hash buckets that happen to be in use. If you still need that
+esoteric value, you can get it through the macro C<HvFILL(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));
+ 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));
+ 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));
+ 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));
+ 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));
+ 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)
+ 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
+the length of the key. The C<hash> parameter is the precomputed 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*>.
+NULL if the operation failed or if the value did not need to be actually
+stored within the hash (as in the case of tied hashes). Otherwise it can
+be dereferenced to get the original C<SV*>. Note that the caller is
+responsible for suitably incrementing the reference count of C<val>
+before the call, and decrementing it if the function returned NULL.
+
+See L<Understanding the Magic of Tied Hashes and Arrays> for more
+information on how to use this function on tied hashes.
+
+ SV** hv_store (HV* tb, const char* key, U32 klen, SV* val, U32 hash)
+
+=item hv_store_ent
- SV** hv_store _((HV* tb, char* key, U32 klen, SV* val, U32 hash));
+Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
+parameter is the precomputed 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 value did not need to be actually
+stored within the hash (as in the case of tied hashes). Otherwise the
+contents of the return value can be accessed using the C<He???> macros
+described here. Note that the caller is responsible for suitably
+incrementing the reference count of C<val> before the call, and decrementing
+it if the function returned NULL.
+
+See L<Understanding the Magic of Tied Hashes and Arrays> for more
+information on how to use this function on tied hashes.
+
+ HE* hv_store_ent (HV* tb, SV* key, SV* val, U32 hash)
=item hv_undef
Undefines the hash.
- void hv_undef _((HV* tb));
+ void hv_undef (HV* tb)
=item isALNUM
Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
-character.
+character or digit.
- int isALNUM (char c)
+ int isALNUM (char c)
=item isALPHA
Returns a boolean indicating whether the C C<char> is an ascii alphabetic
character.
- int isALPHA (char c)
+ int isALPHA (char c)
=item isDIGIT
Returns a boolean indicating whether the C C<char> is an ascii digit.
- int isDIGIT (char c)
+ int isDIGIT (char c)
=item isLOWER
Returns a boolean indicating whether the C C<char> is a lowercase character.
- int isLOWER (char c)
+ int isLOWER (char c)
=item isSPACE
Returns a boolean indicating whether the C C<char> is whitespace.
- int isSPACE (char c)
+ int isSPACE (char c)
=item isUPPER
Returns a boolean indicating whether the C C<char> is an uppercase character.
- int isUPPER (char c)
+ int isUPPER (char c)
=item items
LEAVE;
+=item looks_like_number
+
+Test if an the content of an SV looks like a number (or is a number).
+
+ int looks_like_number(SV*)
+
+
=item MARK
Stack marker variable for the XSUB. See C<dMARK>.
Clear something magical that the SV represents. See C<sv_magic>.
- int mg_clear _((SV* sv));
+ 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));
+ int mg_copy (SV *, SV *, const 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));
+ 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));
+ 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));
+ int mg_get (SV* sv)
=item mg_len
Report on the SV's length. See C<sv_magic>.
- U32 mg_len _((SV* sv));
+ 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));
+ 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));
+ int mg_set (SV* sv)
+
+=item modglobal
+
+C<modglobal> is a general purpose, interpreter global HV for use by
+extensions that need to keep information on a per-interpreter basis.
+In a pinch, it can also be used as a symbol table for extensions
+to share data among each other. It is a good idea to use keys
+prefixed by the package name of the extension that owns the data.
=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.
+the type. Can do overlapping moves. See also C<Copy>.
- (void) Move( s, d, n, t );
+ void Move( s, d, n, t )
-=item na
+=item PL_na
-A variable which may be used with C<SvPV> to tell Perl to calculate the
-string length.
+A convenience variable which is typically used with C<SvPV> when one doesn't
+care about the length of the string. It is usually more efficient to
+either declare a local variable and use that instead or to use the C<SvPV_nolen>
+macro.
=item New
The XSUB-writer's interface to the C C<malloc> function.
- void * New( x, void *ptr, int size, type )
+ void* New( x, void *ptr, int size, type )
-=item Newc
+=item newAV
-The XSUB-writer's interface to the C C<malloc> function, with cast.
+Creates a new AV. The reference count is set to 1.
- void * Newc( x, void *ptr, int size, type, cast )
+ AV* newAV (void)
-=item Newz
+=item Newc
-The XSUB-writer's interface to the C C<malloc> function. The allocated
-memory is zeroed with C<memzero>.
+The XSUB-writer's interface to the C C<malloc> function, with cast.
- void * Newz( x, void *ptr, int size, type )
+ void* Newc( x, void *ptr, int size, type, cast )
-=item newAV
+=item newCONSTSUB
-Creates a new AV. The refcount is set to 1.
+Creates a constant sub equivalent to Perl C<sub FOO () { 123 }>
+which is eligible for inlining at compile-time.
- AV* newAV _((void));
+ void newCONSTSUB(HV* stash, char* name, SV* sv)
=item newHV
-Creates a new HV. The refcount is set to 1.
+Creates a new HV. The reference count is set to 1.
- HV* newHV _((void));
+ HV* newHV (void)
-=item newRV
+=item newRV_inc
-Creates an RV wrapper for an SV. The refcount for the original SV is
+Creates an RV wrapper for an SV. The reference count for the original SV is
incremented.
- SV* newRV _((SV* ref));
+ SV* newRV_inc (SV* ref)
+
+For historical reasons, "newRV" is a synonym for "newRV_inc".
+
+=item newRV_noinc
-=item newSV
+Creates an RV wrapper for an SV. The reference count for the original
+SV is B<not> incremented.
-Creates a new SV. The C<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* newRV_noinc (SV* ref)
- SV* newSV _((STRLEN len));
+=item NEWSV
+
+Creates a new SV. A non-zero C<len> parameter indicates the number of
+bytes of preallocated string space the SV should have. An extra byte
+for a tailing NUL is also reserved. (SvPOK is not set for the SV even
+if string space is allocated.) The reference count for the new SV is
+set to 1. C<id> is an integer id between 0 and 1299 (used to identify
+leaks).
+
+ SV* NEWSV (int id, STRLEN len)
=item newSViv
-Creates a new SV and copies an integer into it. The refcount for the SV is
-set to 1.
+Creates a new SV and copies an integer into it. The reference count for the
+SV is set to 1.
- SV* newSViv _((IV i));
+ SV* newSViv (IV i)
=item newSVnv
-Creates a new SV and copies a double into it. The refcount for the SV is
-set to 1.
+Creates a new SV and copies a double into it. The reference count for the
+SV is set to 1.
- SV* newSVnv _((NV i));
+ SV* newSVnv (NV i)
=item newSVpv
-Creates a new SV and copies a string into it. The refcount for the SV is
-set to 1. If C<len> is zero then Perl will compute the length.
+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, Perl will compute the length using
+strlen(). For efficiency, consider using C<newSVpvn> instead.
+
+ SV* newSVpv (const char* s, STRLEN len)
+
+=item newSVpvf
- SV* newSVpv _((char* s, STRLEN len));
+Creates a new SV an initialize it with the string formatted like
+C<sprintf>.
+
+ SV* newSVpvf(const char* pat, ...)
+
+=item newSVpvn
+
+Creates a new SV and copies a string into it. The reference count for the
+SV is set to 1. Note that if C<len> is zero, Perl will create a zero length
+string. You are responsible for ensuring that the source string is at least
+C<len> bytes long.
+
+ SV* newSVpvn (const 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
-refcount is 1.
+reference count is 1.
- SV* newSVrv _((SV* rv, char* classname));
+ SV* newSVrv (SV* rv, const char* classname)
=item newSVsv
Creates a new SV which is an exact duplicate of the original SV.
- SV* newSVsv _((SV* old));
+ SV* newSVsv (SV* old)
=item newXS
Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
the subs.
+=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 Nullav
Null AV pointer.
Performs a callback to the specified Perl sub. See L<perlcall>.
- I32 perl_call_argv _((char* subname, I32 flags, char** argv));
+ I32 perl_call_argv (const 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));
+ I32 perl_call_method (const 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));
+ I32 perl_call_pv (const 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));
+ I32 perl_call_sv (SV* sv, I32 flags)
=item perl_construct
Tells Perl to C<eval> the string in the SV.
- I32 perl_eval_sv _((SV* sv, I32 flags));
+ I32 perl_eval_sv (SV* sv, I32 flags)
+
+=item perl_eval_pv
+
+Tells Perl to C<eval> the given string and return an SV* result.
+
+ SV* perl_eval_pv (const char* p, I32 croak_on_error)
=item perl_free
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.
+set and the variable does not exist then NULL is returned.
- AV* perl_get_av _((char* name, I32 create));
+ AV* perl_get_av (const 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.
+Returns the CV of the specified Perl subroutine. If C<create> is set and
+the Perl subroutine does not exist then it will be declared (which has
+the same effect as saying C<sub name;>). If C<create> is not
+set and the subroutine does not exist then NULL is returned.
- CV* perl_get_cv _((char* name, I32 create));
+ CV* perl_get_cv (const 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.
+set and the variable does not exist then NULL is returned.
- HV* perl_get_hv _((char* name, I32 create));
+ HV* perl_get_hv (const 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.
+set and the variable does not exist then NULL is returned.
- SV* perl_get_sv _((char* name, I32 create));
+ SV* perl_get_sv (const char* name, I32 create)
=item perl_parse
Tells Perl to C<require> a module.
- void perl_require_pv _((char* pv));
+ void perl_require_pv (const char* pv)
=item perl_run
Pops an integer off the stack.
- int POPi();
+ int POPi()
=item POPl
Pops a long off the stack.
- long POPl();
+ long POPl()
=item POPp
Pops a string off the stack.
- char * POPp();
+ char* POPp()
=item POPn
Pops a double off the stack.
- double POPn();
+ double POPn()
=item POPs
Pops an SV off the stack.
- SV* POPs();
+ SV* POPs()
=item PUSHMARK
=item PUSHi
Push an integer onto the stack. The stack must have room for this element.
-See C<XPUSHi>.
+Handles 'set' magic. See C<XPUSHi>.
- PUSHi(int d)
+ void PUSHi(int d)
=item PUSHn
Push a double onto the stack. The stack must have room for this element.
-See C<XPUSHn>.
+Handles 'set' magic. See C<XPUSHn>.
- PUSHn(double d)
+ void 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>.
+The C<len> indicates the length of the string. Handles 'set' magic. See
+C<XPUSHp>.
- PUSHp(char *c, int len )
+ void PUSHp(char *c, int len )
=item PUSHs
-Push an SV onto the stack. The stack must have room for this element. See
-C<XPUSHs>.
+Push an SV onto the stack. The stack must have room for this element. Does
+not handle 'set' magic. See C<XPUSHs>.
+
+ void PUSHs(sv)
+
+=item PUSHu
+
+Push an unsigned integer onto the stack. The stack must have room for
+this element. See C<XPUSHu>.
+
+ void PUSHu(unsigned int d)
- PUSHs(sv)
=item PUTBACK
The XSUB-writer's interface to the C C<realloc> function.
- void * Renew( void *ptr, int size, type )
+ 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 )
+ void* Renewc( void *ptr, int size, type, cast )
=item RETVAL
Copy a string to a safe spot. This does not use an SV.
- char* savepv _((char* sv));
+ char* savepv (const 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));
+ char* savepvn (const char* sv, I32 len)
=item SAVETMPS
Used to access elements on the XSUB's stack.
- SV* ST(int x)
+ 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 )
+ 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 )
+ 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 )
+ 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 )
+ 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 )
+ 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 )
+ 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 )
+ 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 )
+ 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));
+ 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 refcount of the
-SV is unaffected.
+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));
+ SV* sv_bless (SV* sv, HV* stash)
=item sv_catpv
Concatenates the string onto the end of the string which is in the SV.
+Handles 'get' magic, but not 'set' magic. See C<sv_catpv_mg>.
+
+ void sv_catpv (SV* sv, const char* ptr)
+
+=item sv_catpv_mg
- void sv_catpv _((SV* sv, char* ptr));
+Like C<sv_catpv>, but also handles 'set' magic.
+
+ void sv_catpvn (SV* sv, const 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.
+C<len> indicates number of bytes to copy. Handles 'get' magic, but not
+'set' magic. See C<sv_catpvn_mg>.
+
+ void sv_catpvn (SV* sv, const char* ptr, STRLEN len)
+
+=item sv_catpvn_mg
+
+Like C<sv_catpvn>, but also handles 'set' magic.
- void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
+ void sv_catpvn_mg (SV* sv, const char* ptr, STRLEN len)
+
+=item sv_catpvf
+
+Processes its arguments like C<sprintf> and appends the formatted output
+to an SV. Handles 'get' magic, but not 'set' magic. C<SvSETMAGIC()> must
+typically be called after calling this function to handle 'set' magic.
+
+ void sv_catpvf (SV* sv, const char* pat, ...)
+
+=item sv_catpvf_mg
+
+Like C<sv_catpvf>, but also handles 'set' magic.
+
+ void sv_catpvf_mg (SV* sv, const char* pat, ...)
=item sv_catsv
Concatenates the string from SV C<ssv> onto the end of the string in SV
-C<dsv>.
+C<dsv>. Handles 'get' magic, but not 'set' magic. See C<sv_catsv_mg>.
- void sv_catsv _((SV* dsv, SV* ssv));
+ void sv_catsv (SV* dsv, SV* ssv)
-=item sv_cmp
+=item sv_catsv_mg
-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>.
+Like C<sv_catsv>, but also handles 'set' magic.
+
+ void sv_catsv_mg (SV* dsv, SV* ssv)
+
+=item sv_chop
+
+Efficient removal of characters from the beginning of the string
+buffer. SvPOK(sv) must be true and the C<ptr> must be a pointer to
+somewhere inside the string buffer. The C<ptr> becomes the first
+character of the adjusted string.
+
+ void sv_chop(SV* sv, const char *ptr)
- I32 sv_cmp _((SV* sv1, SV* sv2));
=item sv_cmp
string in C<sv1> is less than, equal to, or greater than the string in
C<sv2>.
- I32 sv_cmp _((SV* sv1, SV* 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)
+ 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 )
+ void SvCUR_set (SV* sv, int val)
=item sv_dec
-Autodecrement of the value in the SV.
+Auto-decrement of the value in the SV.
- void sv_dec _((SV* sv));
+ void sv_dec (SV* sv)
-=item sv_dec
+=item sv_derived_from
-Autodecrement of the value in the SV.
+Returns a boolean indicating whether the SV is derived from the specified
+class. This is the function that implements C<UNIVERSAL::isa>. It works
+for class names as well as for objects.
- void sv_dec _((SV* sv));
+ bool sv_derived_from (SV* sv, const char* name);
=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)
+ char* 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));
+ I32 sv_eq (SV* sv1, SV* sv2)
+
+=item SvGETMAGIC
+
+Invokes C<mg_get> on an SV if it has 'get' magic. This macro evaluates
+its argument more than once.
+
+ void SvGETMAGIC(SV *sv)
=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.
+Expands the character buffer in the SV so that it has room for the
+indicated number of bytes (remember to reserve space for an extra
+trailing NUL character). Calls C<sv_grow> to perform the expansion if
+necessary. Returns a pointer to the character buffer.
- char * SvGROW( SV* sv, int len )
+ char* SvGROW(SV* sv, STRLEN len)
=item sv_grow
=item sv_inc
-Autoincrement of the value in the SV.
+Auto-increment of the value in the SV.
+
+ void sv_inc (SV* sv)
+
+=item sv_insert
- void sv_inc _((SV* sv));
+Inserts a string at the specified offset/length within the SV.
+Similar to the Perl substr() function.
+
+ void sv_insert(SV *sv, STRLEN offset, STRLEN len,
+ char *str, STRLEN strlen)
=item SvIOK
Returns a boolean indicating whether the SV contains an integer.
- int SvIOK (SV* SV)
+ int SvIOK (SV* SV)
=item SvIOK_off
Unsets the IV status of an SV.
- SvIOK_off (SV* sv)
+ void 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)
+ void 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)
+ void SvIOK_only (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)
+ 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
+class. This does not check for subtypes; use C<sv_derived_from> to verify
an inheritance relationship.
- int sv_isa _((SV* sv, char* name));
-
-=item SvIV
-
-Returns the integer which is in the SV.
-
- int SvIV (SV* sv)
+ int sv_isa (SV* sv, char* name)
=item sv_isobject
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));
+ int sv_isobject (SV* sv)
-=item SvIVX
+=item SvIV
-Returns the integer which is stored in the SV.
+Coerces the given SV to an integer and returns it.
- int SvIVX (SV* sv);
+ int SvIV (SV* sv)
-=item SvLEN
+=item SvIVX
-Returns the size of the string buffer in the SV. See C<SvCUR>.
+Returns the integer which is stored in the SV, assuming SvIOK is true.
- int SvLEN (SV* sv)
+ int SvIVX (SV* sv)
-=item sv_len
+=item SvLEN
-Returns the length of the string in the SV. Use C<SvCUR>.
+Returns the size of the string buffer in the SV. See C<SvCUR>.
- STRLEN sv_len _((SV* sv));
+ int SvLEN (SV* sv)
=item sv_len
Returns the length of the string in the SV. Use C<SvCUR>.
- STRLEN sv_len _((SV* sv));
+ 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));
+ void sv_magic (SV* sv, SV* obj, int how, const 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)
+ SV* sv_mortalcopy (SV* oldsv)
=item sv_newmortal
-Creates a new SV which is mortal. The refcount of the SV is set to 1.
-
- SV* sv_newmortal _((void));
-
-=item sv_no
+Creates a new SV which is mortal. The reference count of the SV is set to 1.
-This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
+ SV* sv_newmortal (void)
=item SvNIOK
Returns a boolean indicating whether the SV contains a number, integer or
double.
- int SvNIOK (SV* SV)
+ int SvNIOK (SV* SV)
=item SvNIOK_off
Unsets the NV/IV status of an SV.
- SvNIOK_off (SV* sv)
+ void 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)
+ int SvNIOKp (SV* SV)
+
+=item PL_sv_no
+
+This is the C<false> SV. See C<PL_sv_yes>. Always refer to this as C<&PL_sv_no>.
=item SvNOK
Returns a boolean indicating whether the SV contains a double.
- int SvNOK (SV* SV)
+ int SvNOK (SV* SV)
=item SvNOK_off
Unsets the NV status of an SV.
- SvNOK_off (SV* sv)
+ void 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)
+ void 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)
+ void SvNOK_only (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)
+ int SvNOKp (SV* SV)
=item SvNV
-Returns the double which is stored in the SV.
+Coerce the given SV to a double and return it.
- double SvNV (SV* sv);
+ double SvNV (SV* sv)
=item SvNVX
-Returns the double which is stored in the SV.
+Returns the double which is stored in the SV, assuming SvNOK is true.
+
+ double SvNVX (SV* sv)
- double SvNVX (SV* sv);
+=item SvOK
+
+Returns a boolean indicating whether the value is an SV.
+
+ int SvOK (SV* sv)
+
+=item SvOOK
+
+Returns a boolean indicating whether the SvIVX is a valid offset value
+for the SvPVX. This hack is used internally to speed up removal of
+characters from the beginning of a SvPV. When SvOOK is true, then the
+start of the allocated string buffer is really (SvPVX - SvIVX).
+
+ int SvOOK(SV* sv)
=item SvPOK
Returns a boolean indicating whether the SV contains a character string.
- int SvPOK (SV* SV)
+ int SvPOK (SV* SV)
=item SvPOK_off
Unsets the PV status of an SV.
- SvPOK_off (SV* sv)
+ void 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)
+ void 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)
+ void SvPOK_only (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)
+ 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.
+if the SV does not contain a string. Handles 'get' magic.
+
+ char* SvPV (SV* sv, STRLEN len)
+
+=item SvPV_force
+
+Like <SvPV> but will force the SV into becoming a string (SvPOK). You
+want force if you are going to update the SvPVX directly.
+
+ char* SvPV_force(SV* sv, STRLEN len)
+
+=item SvPV_nolen
+
+Returns a pointer to the string in the SV, or a stringified form of the SV
+if the SV does not contain a string. Handles 'get' magic.
- char * SvPV (SV* sv, int len )
+ char* SvPV_nolen (SV* sv)
=item SvPVX
Returns a pointer to the string in the SV. The SV must contain a string.
- char * SvPVX (SV* sv)
+ char* SvPVX (SV* sv)
=item SvREFCNT
-Returns the value of the object's refcount.
+Returns the value of the object's reference count.
- int SvREFCNT (SV* sv);
+ int SvREFCNT (SV* sv)
=item SvREFCNT_dec
-Decrements the refcount of the given SV.
+Decrements the reference count of the given SV.
- void SvREFCNT_dec (SV* sv)
+ void SvREFCNT_dec (SV* sv)
=item SvREFCNT_inc
-Increments the refcount of the given SV.
+Increments the reference count of the given SV.
- void SvREFCNT_inc (SV* sv)
+ void SvREFCNT_inc (SV* sv)
=item SvROK
Tests if the SV is an RV.
- int SvROK (SV* sv)
+ int SvROK (SV* sv)
=item SvROK_off
Unsets the RV status of an SV.
- SvROK_off (SV* sv)
+ void SvROK_off (SV* sv)
=item SvROK_on
Tells an SV that it is an RV.
- SvROK_on (SV* sv)
+ void SvROK_on (SV* sv)
=item SvRV
Dereferences an RV to return the SV.
- SV* SvRV (SV* sv);
+ SV* SvRV (SV* sv)
+
+=item SvSETMAGIC
+
+Invokes C<mg_set> on an SV if it has 'set' magic. This macro evaluates
+its argument more than once.
+
+ void SvSETMAGIC( SV *sv )
=item sv_setiv
-Copies an integer into the given SV.
+Copies an integer into the given SV. Does not handle 'set' magic.
+See C<sv_setiv_mg>.
+
+ void sv_setiv (SV* sv, IV num)
+
+=item sv_setiv_mg
- void sv_setiv _((SV* sv, IV num));
+Like C<sv_setiv>, but also handles 'set' magic.
+
+ void sv_setiv_mg (SV* sv, IV num)
=item sv_setnv
-Copies a double into the given SV.
+Copies a double into the given SV. Does not handle 'set' magic.
+See C<sv_setnv_mg>.
+
+ void sv_setnv (SV* sv, double num)
+
+=item sv_setnv_mg
+
+Like C<sv_setnv>, but also handles 'set' magic.
- void sv_setnv _((SV* sv, double num));
+ void sv_setnv_mg (SV* sv, double num)
=item sv_setpv
Copies a string into an SV. The string must be null-terminated.
+Does not handle 'set' magic. See C<sv_setpv_mg>.
+
+ void sv_setpv (SV* sv, const char* ptr)
+
+=item sv_setpv_mg
+
+Like C<sv_setpv>, but also handles 'set' magic.
+
+ void sv_setpv_mg (SV* sv, const char* ptr)
- void sv_setpv _((SV* sv, char* ptr));
+=item sv_setpviv
+
+Copies an integer into the given SV, also updating its string value.
+Does not handle 'set' magic. See C<sv_setpviv_mg>.
+
+ void sv_setpviv (SV* sv, IV num)
+
+=item sv_setpviv_mg
+
+Like C<sv_setpviv>, but also handles 'set' magic.
+
+ void sv_setpviv_mg (SV* sv, IV num)
=item sv_setpvn
Copies a string into an SV. The C<len> parameter indicates the number of
-bytes to be copied.
+bytes to be copied. Does not handle 'set' magic. See C<sv_setpvn_mg>.
+
+ void sv_setpvn (SV* sv, const char* ptr, STRLEN len)
+
+=item sv_setpvn_mg
+
+Like C<sv_setpvn>, but also handles 'set' magic.
- void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
+ void sv_setpvn_mg (SV* sv, const char* ptr, STRLEN len)
+
+=item sv_setpvf
+
+Processes its arguments like C<sprintf> and sets an SV to the formatted
+output. Does not handle 'set' magic. See C<sv_setpvf_mg>.
+
+ void sv_setpvf (SV* sv, const char* pat, ...)
+
+=item sv_setpvf_mg
+
+Like C<sv_setpvf>, but also handles 'set' magic.
+
+ void sv_setpvf_mg (SV* sv, const char* pat, ...)
=item sv_setref_iv
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 refcount of 1.
+will be returned and will have a reference count of 1.
- SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
+ SV* sv_setref_iv (SV *rv, char *classname, IV iv)
=item sv_setref_nv
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 refcount of 1.
+will be returned and will have a reference count of 1.
- SV* sv_setref_nv _((SV *rv, char *classname, double nv));
+ 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
+the new SV. If the C<pv> argument is NULL then C<PL_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 refcount of 1.
+will be returned and will have a reference count of 1.
- SV* sv_setref_pv _((SV *rv, char *classname, void* pv));
+ 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.
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 refcount of 1.
+a reference count of 1.
- SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
+ 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 SvSetSV
+
+Calls C<sv_setsv> if dsv is not the same as ssv. May evaluate arguments
+more than once.
+
+ void SvSetSV (SV* dsv, SV* ssv)
+
+=item SvSetSV_nosteal
+
+Calls a non-destructive version of C<sv_setsv> if dsv is not the same as ssv.
+May evaluate arguments more than once.
+
+ void SvSetSV_nosteal (SV* dsv, SV* ssv)
+
=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.
+The source SV may be destroyed if it is mortal. Does not handle 'set' magic.
+See the macro forms C<SvSetSV>, C<SvSetSV_nosteal> and C<sv_setsv_mg>.
+
+ void sv_setsv (SV* dsv, SV* ssv)
+
+=item sv_setsv_mg
+
+Like C<sv_setsv>, but also handles 'set' magic.
+
+ void sv_setsv_mg (SV* dsv, SV* ssv)
- void sv_setsv _((SV* dsv, SV* ssv));
+=item sv_setuv
+
+Copies an unsigned integer into the given SV. Does not handle 'set' magic.
+See C<sv_setuv_mg>.
+
+ void sv_setuv (SV* sv, UV num)
+
+=item sv_setuv_mg
+
+Like C<sv_setuv>, but also handles 'set' magic.
+
+ void sv_setuv_mg (SV* sv, UV num)
=item SvSTASH
Returns the stash of the SV.
- HV * SvSTASH (SV* sv)
+ HV* SvSTASH (SV* sv)
+
+=item SvTAINT
+
+Taints an SV if tainting is enabled
+
+ void SvTAINT (SV* sv)
+
+=item SvTAINTED
+
+Checks to see if an SV is tainted. Returns TRUE if it is, FALSE if not.
+
+ int SvTAINTED (SV* sv)
+
+=item SvTAINTED_off
+
+Untaints an SV. Be I<very> careful with this routine, as it short-circuits
+some of Perl's fundamental security features. XS module authors should
+not use this function unless they fully understand all the implications
+of unconditionally untainting the value. Untainting should be done in
+the standard perl fashion, via a carefully crafted regexp, rather than
+directly untainting variables.
+
+ void SvTAINTED_off (SV* sv)
+
+=item SvTAINTED_on
+
+Marks an SV as tainted.
+
+ void SvTAINTED_on (SV* sv)
=item SVt_IV
=item SvTRUE
Returns a boolean indicating whether Perl would evaluate the SV as true or
-false, defined or undefined.
+false, defined or undefined. Does not handle 'get' magic.
- int SvTRUE (SV* sv)
+ int SvTRUE (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
+=item PL_sv_undef
-Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
-the upgrade if necessary. See C<svtype>.
+This is the C<undef> SV. Always refer to this as C<&PL_sv_undef>.
- bool SvUPGRADE _((SV* sv, svtype mt));
+=item sv_unref
-=item sv_upgrade
+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>.
-Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
+ void sv_unref (SV* sv)
-=item sv_undef
+=item SvUPGRADE
-This is the C<undef> SV. Always refer to this as C<&sv_undef>.
+Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
+the upgrade if necessary. See C<svtype>.
-=item sv_unref
+ bool SvUPGRADE (SV* sv, svtype mt)
-Unsets the RV status of the SV, and decrements the refcount of whatever was
-being referenced by the RV. This can almost be thought of as a reversal of
-C<newSVrv>. See C<SvROK_off>.
+=item sv_upgrade
- void sv_unref _((SV* sv));
+Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
=item sv_usepvn
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.
+the programmer after giving it to sv_usepvn. Does not handle 'set' magic.
+See C<sv_usepvn_mg>.
+
+ void sv_usepvn (SV* sv, char* ptr, STRLEN len)
+
+=item sv_usepvn_mg
+
+Like C<sv_usepvn>, but also handles 'set' magic.
- void sv_usepvn _((SV* sv, char* ptr, STRLEN len));
+ void sv_usepvn_mg (SV* sv, char* ptr, STRLEN len)
-=item sv_yes
+=item sv_vcatpvfn
-This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
+Processes its arguments like C<vsprintf> and appends the formatted output
+to an SV. Uses an array of SVs if the C style variable argument list is
+missing (NULL). When running with taint checks enabled, indicates via
+C<maybe_tainted> if results are untrustworthy (often due to the use of
+locales).
+
+ void sv_catpvfn (SV* sv, const char* pat, STRLEN patlen,
+ va_list *args, SV **svargs, I32 svmax,
+ bool *maybe_tainted);
+
+=item sv_vsetpvfn
+
+Works like C<vcatpvfn> but copies the text into the SV instead of
+appending it.
+
+ void sv_setpvfn (SV* sv, const char* pat, STRLEN patlen,
+ va_list *args, SV **svargs, I32 svmax,
+ bool *maybe_tainted);
+
+=item SvUV
+
+Coerces the given SV to an unsigned integer and returns it.
+
+ UV SvUV(SV* sv)
+
+=item SvUVX
+
+Returns the unsigned integer which is stored in the SV, assuming SvIOK is true.
+
+ UV SvUVX(SV* sv)
+
+=item PL_sv_yes
+
+This is the C<true> SV. See C<PL_sv_no>. Always refer to this as C<&PL_sv_yes>.
=item THIS
Converts the specified character to lowercase.
- int toLOWER (char c)
+ int toLOWER (char c)
=item toUPPER
Converts the specified character to uppercase.
- int toUPPER (char c)
+ int toUPPER (char c)
=item warn
=item XPUSHi
-Push an integer onto the stack, extending the stack if necessary. See
-C<PUSHi>.
+Push an integer onto the stack, extending the stack if necessary. Handles
+
'set' magic. See C<PUSHi>.
XPUSHi(int d)
=item XPUSHn
-Push a double onto the stack, extending the stack if necessary. See
-C<PUSHn>.
+Push a double onto the stack, extending the stack if necessary. Handles 'set'
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>.
+indicates the length of the string.
Handles 'set' magic. See C<PUSHp>.
XPUSHp(char *c, int len)
=item XPUSHs
-Push an SV onto the stack, extending the stack if necessary. See C<PUSHs>.
+Push an SV onto the stack, extending the stack if necessary. Does not
+handle 'set' magic. See C<PUSHs>.
XPUSHs(sv)
+=item XPUSHu
+
+Push an unsigned integer onto the stack, extending the stack if
+necessary. See C<PUSHu>.
+
=item XS
Macro to declare an XSUB and its C parameter list. This is handled by
Return from XSUB, indicating number of items on the stack. This is usually
handled by C<xsubpp>.
- XSRETURN(int x);
+ XSRETURN(int x)
=item XSRETURN_EMPTY
Return an integer from an XSUB immediately. Uses C<XST_mIV>.
- XSRETURN_IV(IV v);
+ XSRETURN_IV(IV v)
=item XSRETURN_NO
-Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
+Return C<&PL_sv_no> from an XSUB immediately. Uses C<XST_mNO>.
XSRETURN_NO;
Return an double from an XSUB immediately. Uses C<XST_mNV>.
- XSRETURN_NV(NV v);
+ 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);
+ XSRETURN_PV(char *v)
=item XSRETURN_UNDEF
-Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
+Return C<&PL_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>.
+Return C<&PL_sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
XSRETURN_YES;
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 );
+ 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 );
+ XST_mNV( int i, NV v )
=item XST_mNO
-Place C<&sv_no> into the specified position C<i> on the stack.
+Place C<&PL_sv_no> into the specified position C<i> on the stack.
- XST_mNO( int i );
+ 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 );
+ XST_mPV( int i, char *v )
=item XST_mUNDEF
-Place C<&sv_undef> into the specified position C<i> on the stack.
+Place C<&PL_sv_undef> into the specified position C<i> on the stack.
- XST_mUNDEF( int i );
+ XST_mUNDEF( int i )
=item XST_mYES
-Place C<&sv_yes> into the specified position C<i> on the stack.
+Place C<&PL_sv_yes> into the specified position C<i> on the stack.
- XST_mYES( int i );
+ XST_mYES( int i )
=item XS_VERSION
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 );
+ void Zero( d, n, t )
=back
-=head1 AUTHOR
+=head1 AUTHORS
-Jeff Okamoto E<lt>F<okamoto@corp.hp.com>E<gt>
+Until May 1997, this document was maintained by Jeff Okamoto
+<okamoto@corp.hp.com>. It is now maintained as part of Perl itself.
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 E<lt>F<roehrich@cray.com>E<gt>.
-
-=head1 DATE
+Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
+Stephen McCamant, and Gurusamy Sarathy.
-Version 22: 1996/9/23
+API Listing originally by Dean Roehrich <roehrich@cray.com>.
https://perl5.git.perl.org / perl5.git / blobdiff