=head1 NAME
-perlguts - Perl's Internal Functions
+perlguts - Introduction to the Perl API
=head1 DESCRIPTION
-This document attempts to describe some of the internal functions of the
-Perl executable. It is far from complete and probably contains many errors.
-Please refer any questions or comments to the author below.
+This document attempts to describe how to use the Perl API, as well as containing
+some info on the basic workings of the Perl core. It is far from complete
+and probably contains many errors. Please refer any questions or
+comments to the author below.
=head1 Variables
=head2 What is an "IV"?
-Perl uses a special typedef IV which is a simple integer type that is
+Perl uses a special typedef IV which is a simple signed integer type that is
guaranteed to be large enough to hold a pointer (as well as an integer).
+Additionally, there is the UV, which is simply an unsigned IV.
Perl also uses two special typedefs, I32 and I16, which will always be at
-least 32-bits and 16-bits long, respectively.
+least 32-bits and 16-bits long, respectively. (Again, there are U32 and U16,
+as well.)
=head2 Working with SVs
An SV can be created and loaded with one command. There are four types of
-values that can be loaded: an integer value (IV), a double (NV), a string,
-(PV), and another scalar (SV).
+values that can be loaded: an integer value (IV), a double (NV),
+a string (PV), and another scalar (SV).
-The five 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 six 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_setpv(SV*, char*);
- void sv_setpvn(SV*, char*, int)
+ 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. The arguments of C<sv_setpvf> are processed like
-C<sprintf>, and the formatted output becomes the value.
-
-All SVs that will contain strings should, but need not, be terminated
-with a NUL character. If it is not NUL-terminated there is a risk of
+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.
To access the actual value that an SV points to, you can use the macros:
SvIV(SV*)
+ SvUV(SV*)
SvNV(SV*)
SvPV(SV*, STRLEN len)
+ SvPV_nolen(SV*)
-which will automatically coerce the actual scalar type into an IV, double,
+which will automatically coerce the actual scalar type into an IV, UV, 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 might 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:
+
+ SV *s;
+ STRLEN len;
+ char * ptr;
+ ptr = SvPV(s, len);
+ foo(ptr, len);
If you want to know if the scalar value is TRUE, you can use:
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 processes its arguments like C<sprintf> and
-appends the formatted output. The fourth 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.
+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("package::varname", FALSE);
+ SV* 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;
This code tries to return a new SV (which contains the value 42) if it should
return a real value, or undef otherwise. Instead it has returned a NULL
pointer which, somewhere down the line, will cause a segmentation violation,
-bus error, or just weird results. Change the zero to C<&sv_undef> in the first
+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
The C<av_clear> function deletes all the elements in the AV* array, but
does not actually delete the array itself. The C<av_undef> function will
delete all the elements in the array plus the array itself. The
-C<av_extend> function extends the array so that it contains C<key>
-elements. If C<key> is less than the current length of the array, then
-nothing is done.
+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("package::varname", FALSE);
+ AV* get_av("package::varname", FALSE);
This returns NULL if the variable does not exist.
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 (Note that
you cannot pass 0 in as a value of C<klen> to tell Perl to measure the
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.
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("package::varname", FALSE);
+ HV* get_hv("package::varname", FALSE);
This returns NULL if the variable does not exist.
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.
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
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.
+doesn't have to be recomputed every time). See L<perlapi> 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.
+L<perlapi> for detailed descriptions of these macros.
HePV(HE* he, STRLEN len)
HeVAL(HE* he)
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 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 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 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);
+
+Tests whether the SV is blessed into the specified class. It does not
+check inheritance relationships.
+
+ int sv_isa(SV* sv, const char* name);
+
+Tests whether the SV is a reference to a blessed object.
+
+ int sv_isobject(SV* sv);
- int sv_isa(SV* sv, char* name);
- int sv_isobject(SV* sv);
+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.
+
+ bool sv_derived_from(SV* sv, const char* name);
+
+To check if you've got an object derived from a specific class you have
+to write:
+
+ if (sv_isobject(sv) && sv_derived_from(sv, class)) { ... }
=head2 Creating New Variables
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.
- SV* perl_get_sv("package::varname", TRUE);
- AV* perl_get_av("package::varname", TRUE);
- HV* perl_get_hv("package::varname", TRUE);
+ SV* get_sv("package::varname", TRUE);
+ AV* get_av("package::varname", TRUE);
+ HV* get_hv("package::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.
Scalar Value
Array Value
Hash Value
- File Handle
- Directory Handle
+ I/O Handle
Format
Subroutine
-There is a single stash called "defstash" that holds the items that exist
+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 defstash. The items in the "Bar::Baz" package are
+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
extern int dberror;
extern char *dberror_list;
- SV* sv = perl_get_sv("dberror", TRUE);
+ SV* sv = get_sv("dberror", TRUE);
sv_setiv(sv, (IV) dberror);
sv_setpv(sv, dberror_list[dberror]);
SvIOK_on(sv);
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.
Thus, when an SV is determined to be magical and of type '\0', if a get
operation is being performed, the routine C<magic_get> is called. All
the various routines for the various magical types begin with C<magic_>.
+NOTE: the magic routines are not considered part of the Perl API, and may
+not be exported by the Perl library.
The current kinds of Magic Virtual Tables are:
a vtbl_amagicelem %OVERLOAD hash element
c (none) Holds overload table (AMT) on stash
B vtbl_bm Boyer-Moore (fast string search)
+ D vtbl_regdata Regex match position data (@+ and @- vars)
+ d vtbl_regdatum Regex match position data element
E vtbl_env %ENV hash
e vtbl_envelem %ENV hash element
f vtbl_fm Formline ('compiled' format)
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.
+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.
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.
+See L<perlapi> for a description of these 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 */
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.
- 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 uppercase letter, then the mg_obj is copied to C<nsv>, but
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
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)>
+
+=item C<SAVEIV(IV i)>
+
+=item C<SAVEI32(I32 i)>
+
+=item C<SAVELONG(long i)>
+
+These macros arrange things to restore the value of integer variable
+C<i> at the end of enclosing I<pseudo-block>.
+
+=item C<SAVESPTR(s)>
+
+=item C<SAVEPPTR(p)>
+
+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.
+
+=item C<SAVEFREESV(SV *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.
+
+=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(DESTRUCTORFUNC_NOCONTEXT_t f, void *p)>
+
+At the end of I<pseudo-block> the function C<f> is called with the
+only argument C<p>.
+
+=item C<SAVEDESTRUCTOR_X(DESTRUCTORFUNC_t f, void *p)>
+
+At the end of I<pseudo-block> the function C<f> is called with the
+implicit context argument (if any), and 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
To handle this situation, the PPCODE directive is used and the stack is
extended using the macro:
- EXTEND(sp, num);
+ EXTEND(SP, num);
-where C<sp> is the stack pointer, and C<num> is the number of elements the
-stack should be extended by.
+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:
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 call_sv(SV*, I32);
+ I32 call_pv(const char*, I32);
+ I32 call_method(const char*, I32);
+ I32 call_argv(const char*, I32, register char**);
-The routine most often used is C<perl_call_sv>. The C<SV*> argument
+The routine most often used is C<call_sv>. The C<SV*> argument
contains either the name of the Perl subroutine to be called, or a
reference to the subroutine. The second argument consists of flags
that control the context in which the subroutine is called, whether
All four routines return the number of arguments that the subroutine returned
on the Perl stack.
-When using any of these routines (except C<perl_call_argv>), the programmer
+These routines used to be called C<perl_call_sv> etc., before Perl v5.6.0,
+but those names are now deprecated; macros of the same name are provided for
+compatibility.
+
+When using any of these routines (except C<call_argv>), the programmer
must manipulate the Perl stack. These include the following macros and
functions:
dSP
+ SP
PUSHMARK()
PUTBACK
SPAGAIN
=head2 Memory Allocation
-It is suggested that you use the version of malloc that is distributed
+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.
instances of the size of the C<type> data structure (using the C<sizeof>
function).
+Here is a handy table of equivalents between ordinary C and Perl's
+memory abstraction layer:
+
+ Instead Of: Use:
+
+ malloc New
+ calloc Newz
+ realloc Renew
+ memcopy Copy
+ memmove Move
+ free Safefree
+ strdup savepv
+ strndup savepvn (Hey, strndup doesn't exist!)
+ memcpy/*(struct foo *) StructCopy
+
=head2 PerlIO
The most recent development releases of Perl has been experimenting with
/ \
$b $c
-(but slightly more complicated). This tree reflect the way Perl
+(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
=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 tree is created by the compiler while I<yacc> code feeds it
+the constructions it recognizes. Since I<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
+so-called "check routines". The correspondence between node names
and corresponding check routines is described in F<opcode.pl> (do not
forget to run C<make regen_headers> if you modify this file).
A check routine is called when the node is fully constructed except
-for the execution-order thread. Since at this time there is no
+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.
=head2 Compile pass 2: context propagation
When a context for a part of compile tree is known, it is propagated
-down through the tree. Aat this time the context can have 5 values
+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.
After the compile tree for a subroutine (or for an C<eval> or a file)
is created, an additional pass over the code is performed. This pass
is neither top-down or bottom-up, but in the execution order (with
-additional compilications for conditionals). These optimizations are
+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 API LISTING
-
-This is a listing of functions, macros, flags, and variables that may be
-useful to extension writers or that may be found while reading other
-extensions.
-
-=over 8
-
-=item AvFILL
-
-See C<av_len>.
-
-=item av_clear
-
-Clears an array, making it empty. Does not free the memory used by the
-array itself.
-
- void av_clear _((AV* ar));
-
-=item av_extend
-
-Pre-extend an array. The C<key> is the index to which the array should be
-extended.
-
- void av_extend _((AV* ar, I32 key));
-
-=item av_fetch
-
-Returns the SV at the specified index in the array. The C<key> is the
-index. If C<lval> is set then the fetch will be part of a store. Check
-that the return value is non-null before dereferencing it to a C<SV*>.
-
-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 av_len
-
-Returns the highest index in the array. Returns -1 if the array is empty.
-
- I32 av_len _((AV* ar));
-
-=item av_make
-
-Creates a new AV and populates it with a list of SVs. The SVs are copied
-into the array, so they may be freed after the call to av_make. The new AV
-will have a reference count of 1.
-
- AV* av_make _((I32 size, SV** svp));
-
-=item av_pop
-
-Pops an SV off the end of the array. Returns C<&sv_undef> if the array is
-empty.
-
- SV* av_pop _((AV* ar));
-
-=item av_push
-
-Pushes an SV onto the end of the array. The array will grow automatically
-to accommodate the addition.
-
- void av_push _((AV* ar, SV* val));
-
-=item av_shift
-
-Shifts an SV off the beginning of the array.
-
- SV* av_shift _((AV* ar));
-
-=item av_store
-
-Stores an SV in an array. The array index is specified as C<key>. The
-return value will be NULL if the operation failed 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));
-
-=item av_undef
-
-Undefines the array. Frees the memory used by the array itself.
-
- void av_undef _((AV* ar));
-
-=item av_unshift
-
-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));
-
-=item CLASS
-
-Variable which is setup by C<xsubpp> to indicate the class name for a C++ XS
-constructor. This is always a C<char*>. See C<THIS> and
-L<perlxs/"Using XS With C++">.
-
-=item Copy
-
-The XSUB-writer's interface to the C C<memcpy> function. The C<s> is the
-source, C<d> is the destination, C<n> is the number of items, and C<t> is
-the type. May fail on overlapping copies. See also C<Move>.
-
- (void) Copy( s, d, n, t );
-
-=item croak
-
-This is the XSUB-writer's interface to Perl's C<die> function. Use this
-function the same way you use the C C<printf> function. See C<warn>.
-
-=item CvSTASH
-
-Returns the stash of the CV.
-
- HV * CvSTASH( SV* sv )
-
-=item DBsingle
-
-When Perl is run in debugging mode, with the B<-d> switch, this SV is a
-boolean which indicates whether subs are being single-stepped.
-Single-stepping is automatically turned on after every step. This is the C
-variable which corresponds to Perl's $DB::single variable. See C<DBsub>.
-
-=item DBsub
+=head1 How multiple interpreters and concurrency are supported
+
+=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. All functions whose names begin C<S_> are private
+(think "S" for "secret" or "static"). All other functions begin with
+"Perl_", but just because a function begins with "Perl_" does not mean it is
+part of the API. (See L</Internal Functions>.) The easiest way to be B<sure> a
+function is part of the API is to find its entry in L<perlapi>.
+If it exists in L<perlapi>, it's part of the API. If it doesn't, and you
+think it should be (i.e., you need it for your extension), send mail via
+L<perlbug> explaining why you think it should be.
+
+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.
-When Perl is run in debugging mode, with the B<-d> switch, this GV contains
-the SV which holds the name of the sub being debugged. This is the C
-variable which corresponds to Perl's $DB::sub variable. See C<DBsingle>.
-The sub name can be found by
+=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.
- SvPV( GvSV( DBsub ), na )
+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:
-=item DBtrace
+ sv_setsv(asv, bsv);
-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>.
+in your extension will translate to this when PERL_IMPLICIT_CONTEXT is
+in effect:
-=item dMARK
+ Perl_sv_setsv(Perl_get_context(), asv, bsv);
-Declare a stack marker variable, C<mark>, for the XSUB. See C<MARK> and
-C<dORIGMARK>.
+or to this otherwise:
-=item dORIGMARK
+ Perl_sv_setsv(asv, bsv);
-Saves the original stack mark for the XSUB. See C<ORIGMARK>.
+You have to do nothing new in your extension to get this; since
+the Perl library provides Perl_get_context(), it will all just
+work.
+
+The second, more efficient way is to use the following template for
+your Foo.xs:
-=item dowarn
+ #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);
-The C variable which corresponds to Perl's $^W warning variable.
+ static SV *
+ my_private_function(int arg1, int arg2)
+ {
+ dTHX; /* fetch context */
+ ... call many Perl API functions ...
+ }
+
+ [... etc ...]
-=item dSP
+ MODULE = Foo PACKAGE = Foo
-Declares a stack pointer variable, C<sp>, for the XSUB. See C<SP>.
+ /* typical XSUB */
-=item dXSARGS
+ void
+ my_xsub(arg)
+ int arg
+ CODE:
+ my_private_function(arg, 10);
-Sets up stack and mark pointers for an XSUB, calling dSP and dMARK. This is
-usually handled automatically by C<xsubpp>. Declares the C<items> variable
-to indicate the number of items on the stack.
+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.
-=item dXSI32
+The third, even more efficient way is to ape how it is done within
+the Perl guts:
-Sets up the C<ix> variable for an XSUB which has aliases. This is usually
-handled automatically by C<xsubpp>.
-=item ENTER
+ #define PERL_NO_GET_CONTEXT /* we want efficiency */
+ #include "EXTERN.h"
+ #include "perl.h"
+ #include "XSUB.h"
-Opening bracket on a callback. See C<LEAVE> and L<perlcall>.
+ /* pTHX_ only needed for functions that call Perl API */
+ static my_private_function(pTHX_ int arg1, int arg2);
- ENTER;
+ static SV *
+ my_private_function(pTHX_ int arg1, int arg2)
+ {
+ /* dTHX; not needed here, because THX is an argument */
+ ... call Perl API functions ...
+ }
-=item EXTEND
+ [... etc ...]
-Used to extend the argument stack for an XSUB's return values.
+ MODULE = Foo PACKAGE = Foo
- EXTEND( sp, int x );
+ /* typical XSUB */
-=item FREETMPS
+ void
+ my_xsub(arg)
+ int arg
+ CODE:
+ my_private_function(aTHX_ arg, 10);
-Closing bracket for temporaries on a callback. See C<SAVETMPS> and
-L<perlcall>.
+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.
- FREETMPS;
+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.
-=item G_ARRAY
+=head2 Future Plans and PERL_IMPLICIT_SYS
-Used to indicate array context. See C<GIMME_V>, C<GIMME> and L<perlcall>.
+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).
-=item G_DISCARD
+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.
-Indicates that arguments returned from a callback should be discarded. See
-L<perlcall>.
+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.
-=item G_EVAL
+=head1 Internal Functions
-Used to force a Perl C<eval> wrapper around a callback. See L<perlcall>.
+All of Perl's internal functions which will be exposed to the outside
+world are be prefixed by C<Perl_> so that they will not conflict with XS
+functions or functions used in a program in which Perl is embedded.
+Similarly, all global variables begin with C<PL_>. (By convention,
+static functions start with C<S_>)
-=item GIMME
+Inside the Perl core, you can get at the functions either with or
+without the C<Perl_> prefix, thanks to a bunch of defines that live in
+F<embed.h>. This header file is generated automatically from
+F<embed.pl>. F<embed.pl> also creates the prototyping header files for
+the internal functions, generates the documentation and a lot of other
+bits and pieces. It's important that when you add a new function to the
+core or change an existing one, you change the data in the table at the
+end of F<embed.pl> as well. Here's a sample entry from that table:
-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>.
+ Apd |SV** |av_fetch |AV* ar|I32 key|I32 lval
-=item GIMME_V
+The second column is the return type, the third column the name. Columns
+after that are the arguments. The first column is a set of flags:
-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.
+=over 3
-=item G_NOARGS
+=item A
-Indicates that no arguments are being sent to a callback. See L<perlcall>.
+This function is a part of the public API.
-=item G_SCALAR
+=item p
-Used to indicate scalar context. See C<GIMME_V>, C<GIMME>, and L<perlcall>.
+This function has a C<Perl_> prefix; ie, it is defined as C<Perl_av_fetch>
-=item G_VOID
+=item d
-Used to indicate void context. See C<GIMME_V> and L<perlcall>.
+This function has documentation using the C<apidoc> feature which we'll
+look at in a second.
-=item gv_fetchmeth
-
-Returns the glob with the given C<name> and a defined subroutine or
-C<NULL>. The glob lives in the given C<stash>, or in the stashes
-accessable via @ISA and @<UNIVERSAL>.
-
-The argument C<level> should be either 0 or -1. If C<level==0>, as a
-side-effect creates a glob with the given C<name> in the given
-C<stash> which in the case of success contains an alias for the
-subroutine, and sets up caching info for this glob. Similarly for all
-the searched stashes.
-
-This function grants C<"SUPER"> token as a postfix of the stash name.
-
-The GV returned from C<gv_fetchmeth> may be a method cache entry,
-which is not visible to Perl code. So when calling C<perl_call_sv>,
-you should not use the GV directly; instead, you should use the
-method's CV, which can be obtained from the GV with the C<GvCV> macro.
-
- GV* gv_fetchmeth _((HV* stash, char* name, STRLEN len, I32 level));
-
-=item gv_fetchmethod
-
-=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 presense 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, char* name));
- GV* gv_fetchmethod_autoload _((HV* stash, char* name,
- I32 autoload));
-
-=item gv_stashpv
-
-Returns a pointer to the stash for a specified package. If C<create> is set
-then the package will be created if it does not already exist. If C<create>
-is not set and the package does not exist then NULL is returned.
-
- HV* gv_stashpv _((char* name, I32 create));
-
-=item gv_stashsv
-
-Returns a pointer to the stash for a specified package. See C<gv_stashpv>.
-
- HV* gv_stashsv _((SV* sv, I32 create));
-
-=item GvSV
-
-Return the SV from the GV.
-
-=item HEf_SVKEY
-
-This flag, used in the length slot of hash entries and magic
-structures, specifies the structure contains a C<SV*> pointer where a
-C<char*> pointer is to be expected. (For information only--not to be used).
-
-=item HeHASH
-
-Returns the computed hash (type C<U32>) stored in the hash entry.
-
- HeHASH(HE* he)
-
-=item HeKEY
-
-Returns the actual pointer stored in the key slot of the hash entry.
-The pointer may be either C<char*> or C<SV*>, depending on the value of
-C<HeKLEN()>. Can be assigned to. The C<HePV()> or C<HeSVKEY()> macros
-are usually preferable for finding the value of a key.
-
- HeKEY(HE* he)
-
-=item HeKLEN
-
-If this is negative, and amounts to C<HEf_SVKEY>, it indicates the entry
-holds an C<SV*> key. Otherwise, holds the actual length of the key.
-Can be assigned to. The C<HePV()> macro is usually preferable for finding
-key lengths.
-
- HeKLEN(HE* he)
-
-=item HePV
-
-Returns the key slot of the hash entry as a C<char*> value, doing any
-necessary dereferencing of possibly C<SV*> keys. The length of
-the string is placed in C<len> (this is a macro, so do I<not> use
-C<&len>). If you do not care about what the length of the key is,
-you may use the global variable C<na>. Remember though, that hash
-keys in perl are free to contain embedded nulls, so using C<strlen()>
-or similar is not a good way to find the length of hash keys.
-This is very similar to the C<SvPV()> macro described elsewhere in
-this document.
-
- HePV(HE* he, STRLEN len)
-
-=item HeSVKEY
-
-Returns the key as an C<SV*>, or C<Nullsv> if the hash entry
-does not contain an C<SV*> key.
-
- HeSVKEY(HE* he)
-
-=item HeSVKEY_force
-
-Returns the key as an C<SV*>. Will create and return a temporary
-mortal C<SV*> if the hash entry contains only a C<char*> key.
-
- HeSVKEY_force(HE* he)
-
-=item HeSVKEY_set
-
-Sets the key to a given C<SV*>, taking care to set the appropriate flags
-to indicate the presence of an C<SV*> key, and returns the same C<SV*>.
-
- HeSVKEY_set(HE* he, SV* sv)
-
-=item HeVAL
-
-Returns the value slot (type C<SV*>) stored in the hash entry.
-
- HeVAL(HE* he)
-
-=item hv_clear
-
-Clears a hash, making it empty.
-
- void hv_clear _((HV* tb));
-
-=item hv_delayfree_ent
-
-Releases a hash entry, such as while iterating though the hash, but
-delays actual freeing of key and value until the end of the current
-statement (or thereabouts) with C<sv_2mortal>. See C<hv_iternext>
-and C<hv_free_ent>.
-
- void hv_delayfree_ent _((HV* hv, HE* entry));
-
-=item hv_delete
-
-Deletes a key/value pair in the hash. The value SV is removed from the hash
-and returned to the caller. The C<klen> is the length of the key. The
-C<flags> value will normally be zero; if set to G_DISCARD then NULL will be
-returned.
-
- SV* hv_delete _((HV* tb, char* key, U32 klen, I32 flags));
-
-=item hv_delete_ent
-
-Deletes a key/value pair in the hash. The value SV is removed from the hash
-and returned to the caller. The C<flags> value will normally be zero; if set
-to G_DISCARD then NULL will be returned. C<hash> can be a valid 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));
-
-=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
-
-Returns the SV which corresponds to the specified key in the hash. The
-C<klen> is the length of the key. If C<lval> is set then the fetch will be
-part of a store. Check that the return value is non-null before
-dereferencing it to a C<SV*>.
-
-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, 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_free_ent
-
-Releases a hash entry, such as while iterating though the hash. See
-C<hv_iternext> and C<hv_delayfree_ent>.
-
- void hv_free_ent _((HV* hv, HE* entry));
-
-=item hv_iterinit
-
-Prepares a starting point to traverse a hash table.
-
- I32 hv_iterinit _((HV* tb));
-
-=item hv_iterkey
-
-Returns the key from the current position of the hash iterator. See
-C<hv_iterinit>.
-
- char* hv_iterkey _((HE* entry, I32* retlen));
-
-=item hv_iterkeysv
-
-Returns the key as an C<SV*> from the current position of the hash
-iterator. The return value will always be a mortal copy of the
-key. Also see C<hv_iterinit>.
-
- SV* hv_iterkeysv _((HE* entry));
-
-=item hv_iternext
-
-Returns entries from a hash iterator. See C<hv_iterinit>.
-
- HE* hv_iternext _((HV* tb));
-
-=item hv_iternextsv
-
-Performs an C<hv_iternext>, C<hv_iterkey>, and C<hv_iterval> in one
-operation.
-
- SV * hv_iternextsv _((HV* hv, char** key, I32* retlen));
-
-=item hv_iterval
-
-Returns the value from the current position of the hash iterator. See
-C<hv_iterkey>.
-
- SV* hv_iterval _((HV* tb, HE* entry));
-
-=item hv_magic
-
-Adds magic to a hash. See C<sv_magic>.
-
- void hv_magic _((HV* hv, GV* gv, int how));
-
-=item HvNAME
-
-Returns the package name of a stash. See C<SvSTASH>, C<CvSTASH>.
-
- char *HvNAME (HV* stash)
-
-=item hv_store
-
-Stores an SV in a hash. The hash key is specified as C<key> and C<klen> is
-the length of the key. The C<hash> parameter is the precomputed hash
-value; if it is zero then Perl will compute it. The return value 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 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, char* key, U32 klen, SV* val, U32 hash));
-
-=item hv_store_ent
-
-Stores C<val> in a hash. The hash key is specified as C<key>. The C<hash>
-parameter is the 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));
-
-=item isALNUM
-
-Returns a boolean indicating whether the C C<char> is an ascii alphanumeric
-character or digit.
-
- int isALNUM (char c)
-
-=item isALPHA
-
-Returns a boolean indicating whether the C C<char> is an ascii alphabetic
-character.
-
- int isALPHA (char c)
-
-=item isDIGIT
-
-Returns a boolean indicating whether the C C<char> is an ascii digit.
+=back
- int isDIGIT (char c)
+Other available flags are:
-=item isLOWER
+=over 3
-Returns a boolean indicating whether the C C<char> is a lowercase character.
+=item s
- int isLOWER (char c)
+This is a static function and is defined as C<S_whatever>.
-=item isSPACE
+=item n
-Returns a boolean indicating whether the C C<char> is whitespace.
+This does not use C<aTHX_> and C<pTHX> to pass interpreter context. (See
+L<perlguts/Background and PERL_IMPLICIT_CONTEXT>.)
- int isSPACE (char c)
+=item r
-=item isUPPER
+This function never returns; C<croak>, C<exit> and friends.
-Returns a boolean indicating whether the C C<char> is an uppercase character.
+=item f
- int isUPPER (char c)
+This function takes a variable number of arguments, C<printf> style.
+The argument list should end with C<...>, like this:
-=item items
+ Afprd |void |croak |const char* pat|...
-Variable which is setup by C<xsubpp> to indicate the number of items on the
-stack. See L<perlxs/"Variable-length Parameter Lists">.
+=item m
-=item ix
+This function is part of the experimental development API, and may change
+or disappear without notice.
-Variable which is setup by C<xsubpp> to indicate which of an XSUB's aliases
-was used to invoke it. See L<perlxs/"The ALIAS: Keyword">.
+=item o
-=item LEAVE
+This function should not have a compatibility macro to define, say,
+C<Perl_parse> to C<parse>. It must be called as C<Perl_parse>.
-Closing bracket on a callback. See C<ENTER> and L<perlcall>.
+=item j
- LEAVE;
+This function is not a member of C<CPerlObj>. If you don't know
+what this means, don't use it.
-=item MARK
+=item x
-Stack marker variable for the XSUB. See C<dMARK>.
+This function isn't exported out of the Perl core.
-=item mg_clear
+=back
-Clear something magical that the SV represents. See C<sv_magic>.
+If you edit F<embed.pl>, you will need to run C<make regen_headers> to
+force a rebuild of F<embed.h> and other auto-generated files.
- int mg_clear _((SV* sv));
+=head2 Formatted Printing of IVs and UVs
-=item mg_copy
+If you are printing IVs or UVs instead of the stdio(3) style formatting
+codes like C<%d> you should use the following macros for portability
-Copies the magic from one SV to another. See C<sv_magic>.
+ IVdf IV in decimal
+ UVuf UV in decimal
+ UVof UV in octal
+ UVxf UV in hexadecimal
- int mg_copy _((SV *, SV *, char *, STRLEN));
+For example: printf("IV is %"IVdf"\n", iv); That will expand
+to whatever is the correct format for the IVs.
-=item mg_find
+=head2 Source Documentation
-Finds the magic pointer for type matching the SV. See C<sv_magic>.
+There's an effort going on to document the internal functions and
+automatically produce reference manuals from them - L<perlapi> is one
+such manual which details all the functions which are available to XS
+writers. L<perlintern> is the autogenerated manual for the functions
+which are not part of the API and are supposedly for internal use only.
- MAGIC* mg_find _((SV* sv, int type));
+Source documentation is created by putting POD comments into the C
+source, like this:
-=item mg_free
+ /*
+ =for apidoc sv_setiv
-Free any magic storage used by the SV. See C<sv_magic>.
+ Copies an integer into the given SV. Does not handle 'set' magic. See
+ C<sv_setiv_mg>.
- int mg_free _((SV* sv));
+ =cut
+ */
+
+Please try and supply some documentation if you add functions to the
+Perl core.
+
+=head1 Unicode Support
+
+Perl 5.6.0 introduced Unicode support. It's important for porters and XS
+writers to understand this support and make sure that the code they
+write does not corrupt Unicode data.
+
+=head2 What B<is> Unicode, anyway?
+
+In the olden, less enlightened times, we all used to use ASCII. Most of
+us did, anyway. The big problem with ASCII is that it's American. Well,
+no, that's not actually the problem; the problem is that it's not
+particularly useful for people who don't use the Roman alphabet. What
+used to happen was that particular languages would stick their own
+alphabet in the upper range of the sequence, between 128 and 255. Of
+course, we then ended up with plenty of variants that weren't quite
+ASCII, and the whole point of it being a standard was lost.
+
+Worse still, if you've got a language like Chinese or
+Japanese that has hundreds or thousands of characters, then you really
+can't fit them into a mere 256, so they had to forget about ASCII
+altogether, and build their own systems using pairs of numbers to refer
+to one character.
+
+To fix this, some people formed Unicode, Inc. and
+produced a new character set containing all the characters you can
+possibly think of and more. There are several ways of representing these
+characters, and the one Perl uses is called UTF8. UTF8 uses
+a variable number of bytes to represent a character, instead of just
+one. You can learn more about Unicode at
+L<http://www.unicode.org/|http://www.unicode.org/>
+
+=head2 How can I recognise a UTF8 string?
+
+You can't. This is because UTF8 data is stored in bytes just like
+non-UTF8 data. The Unicode character 200, (C<0xC8> for you hex types)
+capital E with a grave accent, is represented by the two bytes
+C<v196.172>. Unfortunately, the non-Unicode string C<chr(196).chr(172)>
+has that byte sequence as well. So you can't tell just by looking - this
+is what makes Unicode input an interesting problem.
+
+The API function C<is_utf8_string> can help; it'll tell you if a string
+contains only valid UTF8 characters. However, it can't do the work for
+you. On a character-by-character basis, C<is_utf8_char> will tell you
+whether the current character in a string is valid UTF8.
+
+=head2 How does UTF8 represent Unicode characters?
+
+As mentioned above, UTF8 uses a variable number of bytes to store a
+character. Characters with values 1...128 are stored in one byte, just
+like good ol' ASCII. Character 129 is stored as C<v194.129>; this
+contines up to character 191, which is C<v194.191>. Now we've run out of
+bits (191 is binary C<10111111>) so we move on; 192 is C<v195.128>. And
+so it goes on, moving to three bytes at character 2048.
+
+Assuming you know you're dealing with a UTF8 string, you can find out
+how long the first character in it is with the C<UTF8SKIP> macro:
+
+ char *utf = "\305\233\340\240\201";
+ I32 len;
+
+ len = UTF8SKIP(utf); /* len is 2 here */
+ utf += len;
+ len = UTF8SKIP(utf); /* len is 3 here */
+
+Another way to skip over characters in a UTF8 string is to use
+C<utf8_hop>, which takes a string and a number of characters to skip
+over. You're on your own about bounds checking, though, so don't use it
+lightly.
+
+All bytes in a multi-byte UTF8 character will have the high bit set, so
+you can test if you need to do something special with this character
+like this:
+
+ UV uv;
+
+ if (utf & 0x80)
+ /* Must treat this as UTF8 */
+ uv = utf8_to_uv(utf);
+ else
+ /* OK to treat this character as a byte */
+ uv = *utf;
+
+You can also see in that example that we use C<utf8_to_uv> to get the
+value of the character; the inverse function C<uv_to_utf8> is available
+for putting a UV into UTF8:
+
+ if (uv > 0x80)
+ /* Must treat this as UTF8 */
+ utf8 = uv_to_utf8(utf8, uv);
+ else
+ /* OK to treat this character as a byte */
+ *utf8++ = uv;
-=item mg_get
+You B<must> convert characters to UVs using the above functions if
+you're ever in a situation where you have to match UTF8 and non-UTF8
+characters. You may not skip over UTF8 characters in this case. If you
+do this, you'll lose the ability to match hi-bit non-UTF8 characters;
+for instance, if your UTF8 string contains C<v196.172>, and you skip
+that character, you can never match a C<chr(200)> in a non-UTF8 string.
+So don't do that!
+
+=head2 How does Perl store UTF8 strings?
+
+Currently, Perl deals with Unicode strings and non-Unicode strings
+slightly differently. If a string has been identified as being UTF-8
+encoded, Perl will set a flag in the SV, C<SVf_UTF8>. You can check and
+manipulate this flag with the following macros:
-Do magic after a value is retrieved from the SV. See C<sv_magic>.
+ SvUTF8(sv)
+ SvUTF8_on(sv)
+ SvUTF8_off(sv)
- int mg_get _((SV* sv));
+This flag has an important effect on Perl's treatment of the string: if
+Unicode data is not properly distinguished, regular expressions,
+C<length>, C<substr> and other string handling operations will have
+undesirable results.
-=item mg_len
+The problem comes when you have, for instance, a string that isn't
+flagged is UTF8, and contains a byte sequence that could be UTF8 -
+especially when combining non-UTF8 and UTF8 strings.
-Report on the SV's length. See C<sv_magic>.
+Never forget that the C<SVf_UTF8> flag is separate to the PV value; you
+need be sure you don't accidentally knock it off while you're
+manipulating SVs. More specifically, you cannot expect to do this:
- U32 mg_len _((SV* sv));
+ SV *sv;
+ SV *nsv;
+ STRLEN len;
+ char *p;
-=item mg_magical
+ p = SvPV(sv, len);
+ frobnicate(p);
+ nsv = newSVpvn(p, len);
-Turns on the magical status of an SV. See C<sv_magic>.
+The C<char*> string does not tell you the whole story, and you can't
+copy or reconstruct an SV just by copying the string value. Check if the
+old SV has the UTF8 flag set, and act accordingly:
- void mg_magical _((SV* sv));
+ p = SvPV(sv, len);
+ frobnicate(p);
+ nsv = newSVpvn(p, len);
+ if (SvUTF8(sv))
+ SvUTF8_on(nsv);
-=item mg_set
+In fact, your C<frobnicate> function should be made aware of whether or
+not it's dealing with UTF8 data, so that it can handle the string
+appropriately.
-Do magic after a value is assigned to the SV. See C<sv_magic>.
+=head2 How do I convert a string to UTF8?
- int mg_set _((SV* sv));
+If you're mixing UTF8 and non-UTF8 strings, you might find it necessary
+to upgrade one of the strings to UTF8. If you've got an SV, the easiest
+way to do this is:
-=item Move
+ sv_utf8_upgrade(sv);
-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. Can do overlapping moves. See also C<Copy>.
+However, you must not do this, for example:
- (void) Move( s, d, n, t );
+ if (!SvUTF8(left))
+ sv_utf8_upgrade(left);
-=item na
+If you do this in a binary operator, you will actually change one of the
+strings that came into the operator, and, while it shouldn't be noticable
+by the end user, it can cause problems.
-A variable which may be used with C<SvPV> to tell Perl to calculate the
-string length.
+Instead, C<bytes_to_utf8> will give you a UTF8-encoded B<copy> of its
+string argument. This is useful for having the data available for
+comparisons and so on, without harming the orginal SV. There's also
+C<utf8_to_bytes> to go the other way, but naturally, this will fail if
+the string contains any characters above 255 that can't be represented
+in a single byte.
-=item New
+=head2 Is there anything else I need to know?
-The XSUB-writer's interface to the C C<malloc> function.
+Not really. Just remember these things:
- void * New( x, void *ptr, int size, type )
+=over 3
-=item Newc
+=item *
-The XSUB-writer's interface to the C C<malloc> function, with cast.
+There's no way to tell if a string is UTF8 or not. You can tell if an SV
+is UTF8 by looking at is C<SvUTF8> flag. Don't forget to set the flag if
+something should be UTF8. Treat the flag as part of the PV, even though
+it's not - if you pass on the PV to somewhere, pass on the flag too.
- void * Newc( x, void *ptr, int size, type, cast )
+=item *
-=item Newz
+If a string is UTF8, B<always> use C<utf8_to_uv> to get at the value,
+unless C<!(*s & 0x80)> in which case you can use C<*s>.
-The XSUB-writer's interface to the C C<malloc> function. The allocated
-memory is zeroed with C<memzero>.
+=item *
- void * Newz( x, void *ptr, int size, type )
+When writing to a UTF8 string, B<always> use C<uv_to_utf8>, unless
+C<uv < 0x80> in which case you can use C<*s = uv>.
-=item newAV
+=item *
-Creates a new AV. The reference count is set to 1.
+Mixing UTF8 and non-UTF8 strings is tricky. Use C<bytes_to_utf8> to get
+a new string which is UTF8 encoded. There are tricks you can use to
+delay deciding whether you need to use a UTF8 string until you get to a
+high character - C<HALF_UPGRADE> is one of those.
- AV* newAV _((void));
+=back
-=item newHV
+=head1 AUTHORS
-Creates a new HV. The reference count is set to 1.
+Until May 1997, this document was maintained by Jeff Okamoto
+<okamoto@corp.hp.com>. It is now maintained as part of Perl itself
+by the Perl 5 Porters <perl5-porters@perl.org>.
- HV* newHV _((void));
+With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
+Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
+Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer,
+Stephen McCamant, and Gurusamy Sarathy.
-=item newRV_inc
-
-Creates an RV wrapper for an SV. The reference count for the original SV is
-incremented.
-
- SV* newRV_inc _((SV* ref));
-
-For historical reasons, "newRV" is a synonym for "newRV_inc".
-
-=item newRV_noinc
-
-Creates an RV wrapper for an SV. The reference count for the original
-SV is B<not> incremented.
-
- SV* newRV_noinc _((SV* ref));
-
-=item newSV
-
-Creates a new SV. The C<len> parameter indicates the number of bytes of
-preallocated string space the SV should have. The reference count for the
-new SV is set to 1.
-
- SV* newSV _((STRLEN len));
-
-=item newSViv
-
-Creates a new SV and copies an integer into it. The reference count for the
-SV is set to 1.
-
- SV* newSViv _((IV i));
-
-=item newSVnv
-
-Creates a new SV and copies a double into it. The reference count for the
-SV is set to 1.
-
- SV* newSVnv _((NV i));
-
-=item newSVpv
-
-Creates a new SV and copies a string into it. The reference count for the
-SV is set to 1. If C<len> is zero then Perl will compute the length.
-
- SV* newSVpv _((char* s, STRLEN len));
-
-=item newSVrv
-
-Creates a new SV for the RV, C<rv>, to point to. If C<rv> is not an RV then
-it will be upgraded to one. If C<classname> is non-null then the new SV will
-be blessed in the specified package. The new SV is returned and its
-reference count is 1.
-
- SV* newSVrv _((SV* rv, char* classname));
-
-=item newSVsv
-
-Creates a new SV which is an exact duplicate of the original SV.
-
- SV* newSVsv _((SV* old));
-
-=item newXS
-
-Used by C<xsubpp> to hook up XSUBs as Perl subs.
-
-=item newXSproto
-
-Used by C<xsubpp> to hook up XSUBs as Perl subs. Adds Perl prototypes to
-the subs.
-
-=item Nullav
-
-Null AV pointer.
-
-=item Nullch
-
-Null character pointer.
-
-=item Nullcv
-
-Null CV pointer.
-
-=item Nullhv
-
-Null HV pointer.
-
-=item Nullsv
-
-Null SV pointer.
-
-=item ORIGMARK
-
-The original stack mark for the XSUB. See C<dORIGMARK>.
-
-=item perl_alloc
-
-Allocates a new Perl interpreter. See L<perlembed>.
-
-=item perl_call_argv
-
-Performs a callback to the specified Perl sub. See L<perlcall>.
-
- I32 perl_call_argv _((char* subname, I32 flags, char** argv));
-
-=item perl_call_method
-
-Performs a callback to the specified Perl method. The blessed object must
-be on the stack. See L<perlcall>.
-
- I32 perl_call_method _((char* methname, I32 flags));
-
-=item perl_call_pv
-
-Performs a callback to the specified Perl sub. See L<perlcall>.
-
- I32 perl_call_pv _((char* subname, I32 flags));
-
-=item perl_call_sv
-
-Performs a callback to the Perl sub whose name is in the SV. See
-L<perlcall>.
-
- I32 perl_call_sv _((SV* sv, I32 flags));
-
-=item perl_construct
-
-Initializes a new Perl interpreter. See L<perlembed>.
-
-=item perl_destruct
-
-Shuts down a Perl interpreter. See L<perlembed>.
-
-=item perl_eval_sv
-
-Tells Perl to C<eval> the string in the SV.
-
- I32 perl_eval_sv _((SV* sv, I32 flags));
-
-=item perl_eval_pv
-
-Tells Perl to C<eval> the given string and return an SV* result.
-
- SV* perl_eval_pv _((char* p, I32 croak_on_error));
-
-=item perl_free
-
-Releases a Perl interpreter. See L<perlembed>.
-
-=item perl_get_av
-
-Returns the AV of the specified Perl array. If C<create> is set and the
-Perl variable does not exist then it will be created. If C<create> is not
-set and the variable does not exist then NULL is returned.
-
- AV* perl_get_av _((char* name, I32 create));
-
-=item perl_get_cv
-
-Returns the CV of the specified Perl sub. If C<create> is set and the Perl
-variable does not exist then it will be created. If C<create> is not
-set and the variable does not exist then NULL is returned.
-
- CV* perl_get_cv _((char* name, I32 create));
-
-=item perl_get_hv
-
-Returns the HV of the specified Perl hash. If C<create> is set and the Perl
-variable does not exist then it will be created. If C<create> is not
-set and the variable does not exist then NULL is returned.
-
- HV* perl_get_hv _((char* name, I32 create));
-
-=item perl_get_sv
-
-Returns the SV of the specified Perl scalar. If C<create> is set and the
-Perl variable does not exist then it will be created. If C<create> is not
-set and the variable does not exist then NULL is returned.
-
- SV* perl_get_sv _((char* name, I32 create));
-
-=item perl_parse
-
-Tells a Perl interpreter to parse a Perl script. See L<perlembed>.
-
-=item perl_require_pv
-
-Tells Perl to C<require> a module.
-
- void perl_require_pv _((char* pv));
-
-=item perl_run
-
-Tells a Perl interpreter to run. See L<perlembed>.
-
-=item POPi
-
-Pops an integer off the stack.
-
- int POPi();
-
-=item POPl
-
-Pops a long off the stack.
-
- long POPl();
-
-=item POPp
-
-Pops a string off the stack.
-
- char * POPp();
-
-=item POPn
-
-Pops a double off the stack.
-
- double POPn();
-
-=item POPs
-
-Pops an SV off the stack.
-
- SV* POPs();
-
-=item PUSHMARK
-
-Opening bracket for arguments on a callback. See C<PUTBACK> and L<perlcall>.
-
- PUSHMARK(p)
-
-=item PUSHi
-
-Push an integer onto the stack. The stack must have room for this element.
-See C<XPUSHi>.
-
- PUSHi(int d)
-
-=item PUSHn
-
-Push a double onto the stack. The stack must have room for this element.
-See C<XPUSHn>.
-
- PUSHn(double d)
-
-=item PUSHp
-
-Push a string onto the stack. The stack must have room for this element.
-The C<len> indicates the length of the string. See C<XPUSHp>.
-
- PUSHp(char *c, int len )
-
-=item PUSHs
-
-Push an SV onto the stack. The stack must have room for this element. See
-C<XPUSHs>.
-
- PUSHs(sv)
-
-=item PUTBACK
-
-Closing bracket for XSUB arguments. This is usually handled by C<xsubpp>.
-See C<PUSHMARK> and L<perlcall> for other uses.
-
- PUTBACK;
-
-=item Renew
-
-The XSUB-writer's interface to the C C<realloc> function.
-
- void * Renew( void *ptr, int size, type )
-
-=item Renewc
-
-The XSUB-writer's interface to the C C<realloc> function, with cast.
-
- void * Renewc( void *ptr, int size, type, cast )
-
-=item RETVAL
-
-Variable which is setup by C<xsubpp> to hold the return value for an XSUB.
-This is always the proper type for the XSUB.
-See L<perlxs/"The RETVAL Variable">.
-
-=item safefree
-
-The XSUB-writer's interface to the C C<free> function.
-
-=item safemalloc
-
-The XSUB-writer's interface to the C C<malloc> function.
-
-=item saferealloc
-
-The XSUB-writer's interface to the C C<realloc> function.
-
-=item savepv
-
-Copy a string to a safe spot. This does not use an SV.
-
- char* savepv _((char* sv));
-
-=item savepvn
-
-Copy a string to a safe spot. The C<len> indicates number of bytes to
-copy. This does not use an SV.
-
- char* savepvn _((char* sv, I32 len));
-
-=item SAVETMPS
-
-Opening bracket for temporaries on a callback. See C<FREETMPS> and
-L<perlcall>.
-
- SAVETMPS;
-
-=item SP
-
-Stack pointer. This is usually handled by C<xsubpp>. See C<dSP> and
-C<SPAGAIN>.
-
-=item SPAGAIN
-
-Refetch the stack pointer. Used after a callback. See L<perlcall>.
-
- SPAGAIN;
-
-=item ST
-
-Used to access elements on the XSUB's stack.
-
- SV* ST(int x)
-
-=item strEQ
-
-Test two strings to see if they are equal. Returns true or false.
-
- int strEQ( char *s1, char *s2 )
-
-=item strGE
-
-Test two strings to see if the first, C<s1>, is greater than or equal to the
-second, C<s2>. Returns true or false.
-
- int strGE( char *s1, char *s2 )
-
-=item strGT
-
-Test two strings to see if the first, C<s1>, is greater than the second,
-C<s2>. Returns true or false.
-
- int strGT( char *s1, char *s2 )
-
-=item strLE
-
-Test two strings to see if the first, C<s1>, is less than or equal to the
-second, C<s2>. Returns true or false.
-
- int strLE( char *s1, char *s2 )
-
-=item strLT
-
-Test two strings to see if the first, C<s1>, is less than the second,
-C<s2>. Returns true or false.
-
- int strLT( char *s1, char *s2 )
-
-=item strNE
-
-Test two strings to see if they are different. Returns true or false.
-
- int strNE( char *s1, char *s2 )
-
-=item strnEQ
-
-Test two strings to see if they are equal. The C<len> parameter indicates
-the number of bytes to compare. Returns true or false.
-
- int strnEQ( char *s1, char *s2 )
-
-=item strnNE
-
-Test two strings to see if they are different. The C<len> parameter
-indicates the number of bytes to compare. Returns true or false.
-
- int strnNE( char *s1, char *s2, int len )
-
-=item sv_2mortal
-
-Marks an SV as mortal. The SV will be destroyed when the current context
-ends.
-
- SV* sv_2mortal _((SV* sv));
-
-=item sv_bless
-
-Blesses an SV into a specified package. The SV must be an RV. The package
-must be designated by its stash (see C<gv_stashpv()>). The reference count
-of the SV is unaffected.
-
- SV* sv_bless _((SV* sv, HV* stash));
-
-=item sv_catpv
-
-Concatenates the string onto the end of the string which is in the SV.
-
- void sv_catpv _((SV* sv, char* ptr));
-
-=item sv_catpvn
-
-Concatenates the string onto the end of the string which is in the SV. The
-C<len> indicates number of bytes to copy.
-
- void sv_catpvn _((SV* sv, char* ptr, STRLEN len));
-
-=item sv_catpvf
-
-Processes its arguments like C<sprintf> and appends the formatted output
-to an SV.
-
- void sv_catpvf _((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>.
-
- void sv_catsv _((SV* dsv, SV* ssv));
-
-=item sv_cmp
-
-Compares the strings in two SVs. Returns -1, 0, or 1 indicating whether the
-string in C<sv1> is less than, equal to, or greater than the string in
-C<sv2>.
-
- I32 sv_cmp _((SV* sv1, SV* sv2));
-
-=item SvCUR
-
-Returns the length of the string which is in the SV. See C<SvLEN>.
-
- int SvCUR (SV* sv)
-
-=item SvCUR_set
-
-Set the length of the string which is in the SV. See C<SvCUR>.
-
- SvCUR_set (SV* sv, int val )
-
-=item sv_dec
-
-Auto-decrement of the value in the SV.
-
- void sv_dec _((SV* sv));
-
-=item SvEND
-
-Returns a pointer to the last character in the string which is in the SV.
-See C<SvCUR>. Access the character as
-
- *SvEND(sv)
-
-=item sv_eq
-
-Returns a boolean indicating whether the strings in the two SVs are
-identical.
-
- I32 sv_eq _((SV* sv1, SV* sv2));
-
-=item SvGROW
-
-Expands the character buffer in the SV. Calls C<sv_grow> to perform the
-expansion if necessary. Returns a pointer to the character buffer.
-
- char * SvGROW( SV* sv, int len )
-
-=item sv_grow
-
-Expands the character buffer in the SV. This will use C<sv_unref> and will
-upgrade the SV to C<SVt_PV>. Returns a pointer to the character buffer.
-Use C<SvGROW>.
-
-=item sv_inc
-
-Auto-increment of the value in the SV.
-
- void sv_inc _((SV* sv));
-
-=item SvIOK
-
-Returns a boolean indicating whether the SV contains an integer.
-
- int SvIOK (SV* SV)
-
-=item SvIOK_off
-
-Unsets the IV status of an SV.
-
- SvIOK_off (SV* sv)
-
-=item SvIOK_on
-
-Tells an SV that it is an integer.
-
- SvIOK_on (SV* sv)
-
-=item SvIOK_only
-
-Tells an SV that it is an integer and disables all other OK bits.
-
- SvIOK_on (SV* sv)
-
-=item SvIOKp
-
-Returns a boolean indicating whether the SV contains an integer. Checks the
-B<private> setting. Use C<SvIOK>.
-
- int SvIOKp (SV* SV)
-
-=item sv_isa
-
-Returns a boolean indicating whether the SV is blessed into the specified
-class. This does not know how to check for subtype, so it doesn't work in
-an inheritance relationship.
-
- int sv_isa _((SV* sv, char* name));
-
-=item SvIV
-
-Returns the integer which is in the SV.
-
- int SvIV (SV* sv)
-
-=item sv_isobject
-
-Returns a boolean indicating whether the SV is an RV pointing to a blessed
-object. If the SV is not an RV, or if the object is not blessed, then this
-will return false.
-
- int sv_isobject _((SV* sv));
-
-=item SvIVX
-
-Returns the integer which is stored in the SV.
-
- int SvIVX (SV* sv);
-
-=item SvLEN
-
-Returns the size of the string buffer in the SV. See C<SvCUR>.
-
- int SvLEN (SV* sv)
-
-=item sv_len
-
-Returns the length of the string in the SV. Use C<SvCUR>.
-
- STRLEN sv_len _((SV* sv));
-
-=item sv_magic
-
-Adds magic to an SV.
-
- void sv_magic _((SV* sv, SV* obj, int how, char* name, I32 namlen));
-
-=item sv_mortalcopy
-
-Creates a new SV which is a copy of the original SV. The new SV is marked
-as mortal.
-
- SV* sv_mortalcopy _((SV* oldsv));
-
-=item SvOK
-
-Returns a boolean indicating whether the value is an SV.
-
- int SvOK (SV* sv)
-
-=item sv_newmortal
-
-Creates a new SV which is mortal. The reference count of the SV is set to 1.
-
- SV* sv_newmortal _((void));
-
-=item sv_no
-
-This is the C<false> SV. See C<sv_yes>. Always refer to this as C<&sv_no>.
-
-=item SvNIOK
-
-Returns a boolean indicating whether the SV contains a number, integer or
-double.
-
- int SvNIOK (SV* SV)
-
-=item SvNIOK_off
-
-Unsets the NV/IV status of an SV.
-
- SvNIOK_off (SV* sv)
-
-=item SvNIOKp
-
-Returns a boolean indicating whether the SV contains a number, integer or
-double. Checks the B<private> setting. Use C<SvNIOK>.
-
- int SvNIOKp (SV* SV)
-
-=item SvNOK
-
-Returns a boolean indicating whether the SV contains a double.
-
- int SvNOK (SV* SV)
-
-=item SvNOK_off
-
-Unsets the NV status of an SV.
-
- SvNOK_off (SV* sv)
-
-=item SvNOK_on
-
-Tells an SV that it is a double.
-
- SvNOK_on (SV* sv)
-
-=item SvNOK_only
-
-Tells an SV that it is a double and disables all other OK bits.
-
- SvNOK_on (SV* sv)
-
-=item SvNOKp
-
-Returns a boolean indicating whether the SV contains a double. Checks the
-B<private> setting. Use C<SvNOK>.
-
- int SvNOKp (SV* SV)
-
-=item SvNV
-
-Returns the double which is stored in the SV.
-
- double SvNV (SV* sv);
-
-=item SvNVX
-
-Returns the double which is stored in the SV.
-
- double SvNVX (SV* sv);
-
-=item SvPOK
-
-Returns a boolean indicating whether the SV contains a character string.
-
- int SvPOK (SV* SV)
-
-=item SvPOK_off
-
-Unsets the PV status of an SV.
-
- SvPOK_off (SV* sv)
-
-=item SvPOK_on
-
-Tells an SV that it is a string.
-
- SvPOK_on (SV* sv)
-
-=item SvPOK_only
-
-Tells an SV that it is a string and disables all other OK bits.
-
- SvPOK_on (SV* sv)
-
-=item SvPOKp
-
-Returns a boolean indicating whether the SV contains a character string.
-Checks the B<private> setting. Use C<SvPOK>.
-
- int SvPOKp (SV* SV)
-
-=item SvPV
-
-Returns a pointer to the string in the SV, or a stringified form of the SV
-if the SV does not contain a string. If C<len> is C<na> then Perl will
-handle the length on its own.
-
- char * SvPV (SV* sv, int len )
-
-=item SvPVX
-
-Returns a pointer to the string in the SV. The SV must contain a string.
-
- char * SvPVX (SV* sv)
-
-=item SvREFCNT
-
-Returns the value of the object's reference count.
-
- int SvREFCNT (SV* sv);
-
-=item SvREFCNT_dec
-
-Decrements the reference count of the given SV.
-
- void SvREFCNT_dec (SV* sv)
-
-=item SvREFCNT_inc
-
-Increments the reference count of the given SV.
-
- void SvREFCNT_inc (SV* sv)
-
-=item SvROK
-
-Tests if the SV is an RV.
-
- int SvROK (SV* sv)
-
-=item SvROK_off
-
-Unsets the RV status of an SV.
-
- SvROK_off (SV* sv)
-
-=item SvROK_on
-
-Tells an SV that it is an RV.
-
- SvROK_on (SV* sv)
-
-=item SvRV
-
-Dereferences an RV to return the SV.
-
- SV* SvRV (SV* sv);
-
-=item sv_setiv
-
-Copies an integer into the given SV.
-
- void sv_setiv _((SV* sv, IV num));
-
-=item sv_setnv
-
-Copies a double into the given SV.
-
- void sv_setnv _((SV* sv, double num));
-
-=item sv_setpv
-
-Copies a string into an SV. The string must be null-terminated.
-
- void sv_setpv _((SV* sv, char* ptr));
-
-=item sv_setpvn
-
-Copies a string into an SV. The C<len> parameter indicates the number of
-bytes to be copied.
-
- void sv_setpvn _((SV* sv, char* ptr, STRLEN len));
-
-=item sv_setpvf
-
-Processes its arguments like C<sprintf> and sets an SV to the formatted
-output.
-
- void sv_setpvf _((SV* sv, const char* pat, ...));
-
-=item sv_setref_iv
-
-Copies an integer into a new SV, optionally blessing the SV. The C<rv>
-argument will be upgraded to an RV. That RV will be modified to point to
-the new SV. The C<classname> argument indicates the package for the
-blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
-will be returned and will have a reference count of 1.
-
- SV* sv_setref_iv _((SV *rv, char *classname, IV iv));
-
-=item sv_setref_nv
-
-Copies a double into a new SV, optionally blessing the SV. The C<rv>
-argument will be upgraded to an RV. That RV will be modified to point to
-the new SV. The C<classname> argument indicates the package for the
-blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
-will be returned and will have a reference count of 1.
-
- SV* sv_setref_nv _((SV *rv, char *classname, double nv));
-
-=item sv_setref_pv
-
-Copies a pointer into a new SV, optionally blessing the SV. The C<rv>
-argument will be upgraded to an RV. That RV will be modified to point to
-the new SV. If the C<pv> argument is NULL then C<sv_undef> will be placed
-into the SV. The C<classname> argument indicates the package for the
-blessing. Set C<classname> to C<Nullch> to avoid the blessing. The new SV
-will be returned and will have a reference count of 1.
-
- SV* sv_setref_pv _((SV *rv, char *classname, void* pv));
-
-Do not use with integral Perl types such as HV, AV, SV, CV, because those
-objects will become corrupted by the pointer copy process.
-
-Note that C<sv_setref_pvn> copies the string while this copies the pointer.
-
-=item sv_setref_pvn
-
-Copies a string into a new SV, optionally blessing the SV. The length of the
-string must be specified with C<n>. The C<rv> argument will be upgraded to
-an RV. That RV will be modified to point to the new SV. The C<classname>
-argument indicates the package for the blessing. Set C<classname> to
-C<Nullch> to avoid the blessing. The new SV will be returned and will have
-a reference count of 1.
-
- SV* sv_setref_pvn _((SV *rv, char *classname, char* pv, I32 n));
-
-Note that C<sv_setref_pv> copies the pointer while this copies the string.
-
-=item sv_setsv
-
-Copies the contents of the source SV C<ssv> into the destination SV C<dsv>.
-The source SV may be destroyed if it is mortal.
-
- void sv_setsv _((SV* dsv, SV* ssv));
-
-=item SvSTASH
-
-Returns the stash of the SV.
-
- HV * SvSTASH (SV* sv)
-
-=item SVt_IV
-
-Integer type flag for scalars. See C<svtype>.
-
-=item SVt_PV
-
-Pointer type flag for scalars. See C<svtype>.
-
-=item SVt_PVAV
-
-Type flag for arrays. See C<svtype>.
-
-=item SVt_PVCV
-
-Type flag for code refs. See C<svtype>.
-
-=item SVt_PVHV
-
-Type flag for hashes. See C<svtype>.
-
-=item SVt_PVMG
-
-Type flag for blessed scalars. See C<svtype>.
-
-=item SVt_NV
-
-Double type flag for scalars. See C<svtype>.
-
-=item SvTRUE
-
-Returns a boolean indicating whether Perl would evaluate the SV as true or
-false, defined or undefined.
-
- int SvTRUE (SV* sv)
-
-=item SvTYPE
-
-Returns the type of the SV. See C<svtype>.
-
- svtype SvTYPE (SV* sv)
-
-=item svtype
-
-An enum of flags for Perl types. These are found in the file B<sv.h> in the
-C<svtype> enum. Test these flags with the C<SvTYPE> macro.
-
-=item SvUPGRADE
-
-Used to upgrade an SV to a more complex form. Uses C<sv_upgrade> to perform
-the upgrade if necessary. See C<svtype>.
-
- bool SvUPGRADE _((SV* sv, svtype mt));
-
-=item sv_upgrade
-
-Upgrade an SV to a more complex form. Use C<SvUPGRADE>. See C<svtype>.
-
-=item sv_undef
-
-This is the C<undef> SV. Always refer to this as C<&sv_undef>.
-
-=item sv_unref
-
-Unsets the RV status of the SV, and decrements the reference count of
-whatever was being referenced by the RV. This can almost be thought of
-as a reversal of C<newSVrv>. See C<SvROK_off>.
-
- void sv_unref _((SV* sv));
-
-=item sv_usepvn
-
-Tells an SV to use C<ptr> to find its string value. Normally the string is
-stored inside the SV but sv_usepvn allows the SV to use an outside string.
-The C<ptr> should point to memory that was allocated by C<malloc>. The
-string length, C<len>, must be supplied. This function will realloc the
-memory pointed to by C<ptr>, so that pointer should not be freed or used by
-the programmer after giving it to sv_usepvn.
-
- void sv_usepvn _((SV* sv, char* ptr, STRLEN len));
-
-=item sv_yes
-
-This is the C<true> SV. See C<sv_no>. Always refer to this as C<&sv_yes>.
-
-=item THIS
-
-Variable which is setup by C<xsubpp> to designate the object in a C++ XSUB.
-This is always the proper type for the C++ object. See C<CLASS> and
-L<perlxs/"Using XS With C++">.
-
-=item toLOWER
-
-Converts the specified character to lowercase.
-
- int toLOWER (char c)
-
-=item toUPPER
-
-Converts the specified character to uppercase.
-
- int toUPPER (char c)
-
-=item warn
-
-This is the XSUB-writer's interface to Perl's C<warn> function. Use this
-function the same way you use the C C<printf> function. See C<croak()>.
-
-=item XPUSHi
-
-Push an integer onto the stack, extending the stack if necessary. See
-C<PUSHi>.
-
- XPUSHi(int d)
-
-=item XPUSHn
-
-Push a double onto the stack, extending the stack if necessary. See
-C<PUSHn>.
-
- XPUSHn(double d)
-
-=item XPUSHp
-
-Push a string onto the stack, extending the stack if necessary. The C<len>
-indicates the length of the string. See C<PUSHp>.
-
- XPUSHp(char *c, int len)
-
-=item XPUSHs
-
-Push an SV onto the stack, extending the stack if necessary. See C<PUSHs>.
-
- XPUSHs(sv)
-
-=item XS
-
-Macro to declare an XSUB and its C parameter list. This is handled by
-C<xsubpp>.
-
-=item XSRETURN
-
-Return from XSUB, indicating number of items on the stack. This is usually
-handled by C<xsubpp>.
-
- XSRETURN(int x);
-
-=item XSRETURN_EMPTY
-
-Return an empty list from an XSUB immediately.
-
- XSRETURN_EMPTY;
-
-=item XSRETURN_IV
-
-Return an integer from an XSUB immediately. Uses C<XST_mIV>.
-
- XSRETURN_IV(IV v);
-
-=item XSRETURN_NO
-
-Return C<&sv_no> from an XSUB immediately. Uses C<XST_mNO>.
-
- XSRETURN_NO;
-
-=item XSRETURN_NV
-
-Return an double from an XSUB immediately. Uses C<XST_mNV>.
-
- XSRETURN_NV(NV v);
-
-=item XSRETURN_PV
-
-Return a copy of a string from an XSUB immediately. Uses C<XST_mPV>.
-
- XSRETURN_PV(char *v);
-
-=item XSRETURN_UNDEF
-
-Return C<&sv_undef> from an XSUB immediately. Uses C<XST_mUNDEF>.
-
- XSRETURN_UNDEF;
-
-=item XSRETURN_YES
-
-Return C<&sv_yes> from an XSUB immediately. Uses C<XST_mYES>.
-
- XSRETURN_YES;
-
-=item XST_mIV
-
-Place an integer into the specified position C<i> on the stack. The value is
-stored in a new mortal SV.
-
- XST_mIV( int i, IV v );
-
-=item XST_mNV
-
-Place a double into the specified position C<i> on the stack. The value is
-stored in a new mortal SV.
-
- XST_mNV( int i, NV v );
-
-=item XST_mNO
-
-Place C<&sv_no> into the specified position C<i> on the stack.
-
- XST_mNO( int i );
-
-=item XST_mPV
-
-Place a copy of a string into the specified position C<i> on the stack. The
-value is stored in a new mortal SV.
-
- XST_mPV( int i, char *v );
-
-=item XST_mUNDEF
-
-Place C<&sv_undef> into the specified position C<i> on the stack.
-
- XST_mUNDEF( int i );
-
-=item XST_mYES
-
-Place C<&sv_yes> into the specified position C<i> on the stack.
-
- XST_mYES( int i );
-
-=item XS_VERSION
-
-The version identifier for an XS module. This is usually handled
-automatically by C<ExtUtils::MakeMaker>. See C<XS_VERSION_BOOTCHECK>.
-
-=item XS_VERSION_BOOTCHECK
-
-Macro to verify that a PM module's $VERSION variable matches the XS module's
-C<XS_VERSION> variable. This is usually handled automatically by
-C<xsubpp>. See L<perlxs/"The VERSIONCHECK: Keyword">.
-
-=item Zero
-
-The XSUB-writer's interface to the C C<memzero> function. The C<d> is the
-destination, C<n> is the number of items, and C<t> is the type.
-
- (void) Zero( d, n, t );
-
-=back
-
-=head1 EDITOR
-
-Jeff Okamoto <F<okamoto@corp.hp.com>>
-
-With lots of help and suggestions from Dean Roehrich, Malcolm Beattie,
-Andreas Koenig, Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil
-Bowers, Matthew Green, Tim Bunce, Spider Boardman, Ulrich Pfeifer, and
-Stephen McCamant.
+API Listing originally by Dean Roehrich <roehrich@cray.com>.
-API Listing by Dean Roehrich <F<roehrich@cray.com>>.
+Modifications to autogenerate the API listing (L<perlapi>) by Benjamin
+Stuhl.
-=head1 DATE
+=head1 SEE ALSO
-Version 31.8: 1997/5/17
+perlapi(1), perlintern(1), perlxs(1), perlembed(1)
projects / p5sagit/p5-mst-13.2.git / blobdiff