An SV can be created and loaded with one command. There are five types of
values that can be loaded: an integer value (IV), an unsigned integer
value (UV), a double (NV), a string (PV), and another scalar (SV).
+("PV" stands for "Pointer Value". You might think that it is misnamed
+because it is described as pointing only to strings. However, it is
+possible to have it point to other things For example, it could point
+to an array of UVs. But,
+using it for non-strings requires care, as the underlying assumption of
+much of the internals is that PVs are just for strings. Often, for
+example, a trailing NUL is tacked on automatically. The non-string use
+is documented only in this paragraph.)
The seven routines are:
F<config.h>) guaranteed to be large enough to represent the size of
any string that perl can handle.
-In the unlikely case of a SV requiring more complex initialisation, you
+In the unlikely case of a SV requiring more complex initialization, you
can create an empty SV with newSV(len). If C<len> is 0 an empty SV of
type NULL is returned, else an SV of type PV is returned with len + 1 (for
the NUL) bytes of storage allocated, accessible via SvPVX. In both cases
-the SV has value undef.
+the SV has the undef value.
SV *sv = newSV(0); /* no storage allocated */
- SV *sv = newSV(10); /* 10 (+1) bytes of uninitialised storage allocated */
+ SV *sv = newSV(10); /* 10 (+1) bytes of uninitialised storage
+ * allocated */
To change the value of an I<already-existing> SV, there are eight routines:
void sv_setpv(SV*, const char*);
void sv_setpvn(SV*, const char*, STRLEN)
void sv_setpvf(SV*, const char*, ...);
- void sv_vsetpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool *);
+ void sv_vsetpvfn(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
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.
+string terminating with a NUL character, and not otherwise containing
+NULs.
The arguments of C<sv_setpvf> are processed like C<sprintf>, and the
formatted output becomes the value.
SV *s;
STRLEN len;
- char * ptr;
+ char *ptr;
ptr = SvPV(s, len);
foo(ptr, len);
which will determine if more memory needs to be allocated. If so, it will
call the function C<sv_grow>. Note that C<SvGROW> can only increase, not
decrease, the allocated memory of an SV and that it does not automatically
-add a byte for the a trailing NUL (perl's own string functions typically do
+add space for the trailing NUL byte (perl's own string functions typically do
C<SvGROW(sv, len + 1)>).
If you have an SV and want to know what kind of data Perl thinks is stored
void sv_catpv(SV*, const char*);
void sv_catpvn(SV*, const char*, STRLEN);
void sv_catpvf(SV*, const char*, ...);
- void sv_vcatpvfn(SV*, const char*, STRLEN, va_list *, SV **, I32, bool);
+ void sv_vcatpvfn(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
pointer. The efficiency comes by means of a little hack: instead of
actually removing the characters, C<sv_chop> sets the flag C<OOK>
(offset OK) to signal to other functions that the offset hack is in
-effect, and it puts the number of bytes chopped off into the IV field
-of the SV. It then moves the PV pointer (called C<SvPVX>) forward that
-many bytes, and adjusts C<SvCUR> and C<SvLEN>.
+effect, and it moves the PV pointer (called C<SvPVX>) forward
+by the number of bytes chopped off, and adjusts C<SvCUR> and C<SvLEN>
+accordingly. (A portion of the space between the old and new PV
+pointers is used to store the count of chopped bytes.)
Hence, at this point, the start of the buffer that we allocated lives
at C<SvPVX(sv) - SvIV(sv)> in memory and the PV pointer is pointing
These will tell you if you truly have an integer, double, or string pointer
stored in your SV. The "p" stands for private.
-The are various ways in which the private and public flags may differ.
+There are various ways in which the private and public flags may differ.
For example, a tied SV may have a valid underlying value in the IV slot
(so SvIOKp is true), but the data should be accessed via the FETCH
routine rather than directly, so SvIOK is false. Another is when
The second argument points to an array containing C<num> C<SV*>'s. Once the
AV has been created, the SVs can be destroyed, if so desired.
-Once the AV has been created, the following operations are possible on AVs:
+Once the AV has been created, the following operations are possible on it:
void av_push(AV*, SV*);
SV* av_pop(AV*);
Here are some other functions:
- I32 av_len(AV*);
+ I32 av_top_index(AV*);
SV** av_fetch(AV*, I32 key, I32 lval);
SV** av_store(AV*, I32 key, SV* val);
-The C<av_len> function returns the highest index value in array (just
+The C<av_top_index> function returns the highest index value in an array (just
like $#array in Perl). If the array is empty, -1 is returned. The
C<av_fetch> function returns the value at index C<key>, but if C<lval>
is non-zero, then C<av_fetch> will store an undef value at that index.
C<av_fetch> and C<av_store> both return C<SV**>'s, not C<SV*>'s as their
return value.
+A few more:
+
void av_clear(AV*);
void av_undef(AV*);
void av_extend(AV*, I32 key);
HV* newHV();
-Once the HV has been created, the following operations are possible on HVs:
+Once the HV has been created, the following operations are possible on it:
SV** hv_store(HV*, const char* key, U32 klen, SV* val, U32 hash);
SV** hv_fetch(HV*, const char* key, U32 klen, I32 lval);
value. However, you should check to make sure that the return value is
not NULL before dereferencing it.
-These two functions check if a hash table entry exists, and deletes it.
+The first of these two functions checks if a hash table entry exists, and the
+second deletes it.
bool hv_exists(HV*, const char* key, U32 klen);
SV* hv_delete(HV*, const char* key, U32 klen, I32 flags);
table but does not actually delete the hash table. The C<hv_undef> deletes
both the entries and the hash table itself.
-Perl keeps the actual data in linked list of structures with a typedef of HE.
+Perl keeps the actual data in a linked list of structures with a typedef of HE.
These contain the actual key and value pointers (plus extra administrative
overhead). The key is a string pointer; the value is an C<SV*>. However,
once you have an C<HE*>, to get the actual key and value, use the routines
This returns NULL if the variable does not exist.
-The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
+The hash algorithm is defined in the C<PERL_HASH> macro:
- hash = 0;
- while (klen--)
- hash = (hash * 33) + *key++;
- hash = hash + (hash >> 5); /* after 5.6 */
+ PERL_HASH(hash, key, klen)
-The last step was added in version 5.6 to improve distribution of
-lower bits in the resulting hash value.
+The exact implementation of this macro varies by architecture and version
+of perl, and the return value may change per invocation, so the value
+is only valid for the duration of a single perl process.
See L<Understanding the Magic of Tied Hashes and Arrays> for more
information on how to use the hash access functions on tied hashes.
=head2 References
References are a special type of scalar that point to other data types
-(including references).
+(including other references).
To create a reference, use either of the following functions:
The most useful types that will be returned are:
- SVt_IV Scalar
- SVt_NV Scalar
- SVt_PV Scalar
- SVt_RV Scalar
- SVt_PVAV Array
- SVt_PVHV Hash
- SVt_PVCV Code
- SVt_PVGV Glob (possible a file handle)
- SVt_PVMG Blessed or Magical Scalar
+ < SVt_PVAV Scalar
+ SVt_PVAV Array
+ SVt_PVHV Hash
+ SVt_PVCV Code
+ SVt_PVGV Glob (possibly a file handle)
-See the F<sv.h> header file for more details.
+See L<perlapi/svtype> for more details.
=head2 Blessed References and Class Objects
/* Still under construction */
-Upgrades rv to reference if not already one. Creates new SV for rv to
-point to. If C<classname> is non-null, the SV is blessed into the specified
-class. SV is returned.
+The following function upgrades rv to reference if not already one.
+Creates a new SV for rv to point to. If C<classname> is non-null, the SV
+is blessed into the specified class. SV is returned.
SV* newSVrv(SV* rv, const char* classname);
-Copies integer, unsigned integer or double into an SV whose reference is C<rv>. SV is blessed
-if C<classname> is non-null.
+The following three functions copy integer, unsigned 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, const char* classname, IV iv);
SV* sv_setref_uv(SV* rv, const char* classname, UV uv);
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.
+The following function 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, const char* classname, PV iv);
+ SV* sv_setref_pv(SV* rv, const char* classname, void* pv);
-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.
+The following function copies a 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, const char* classname, PV iv, STRLEN length);
+ SV* sv_setref_pvn(SV* rv, const char* classname, char* pv,
+ STRLEN length);
-Tests whether the SV is blessed into the specified class. It does not
-check inheritance relationships.
+The following function 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.
+The following function tests whether the SV is a reference to a blessed object.
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.
+The following function 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);
The first call creates a mortal SV (with no value), the second converts an existing
SV to a mortal SV (and thus defers a call to C<SvREFCNT_dec>), and the
third creates a mortal copy of an existing SV.
-Because C<sv_newmortal> gives the new SV no value,it must normally be given one
+Because C<sv_newmortal> gives the new SV no value, it must normally be given one
via C<sv_setpv>, C<sv_setiv>, etc. :
SV *tmp = sv_newmortal();
can happen if you make the same value mortal within multiple contexts,
or if you make a variable mortal multiple times. Thinking of "Mortalization"
as deferred C<SvREFCNT_dec> should help to minimize such problems.
-For example if you are passing an SV which you I<know> has high enough REFCNT
+For example if you are passing an SV which you I<know> has a high enough REFCNT
to survive its use on the stack you need not do any mortalization.
If you are not sure then doing an C<SvREFCNT_inc> and C<sv_2mortal>, or
making a C<sv_mortalcopy> is safer.
Perl adds magic to an SV using the sv_magic function:
- void sv_magic(SV* sv, SV* obj, int how, const 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.
int (*svt_clear)(SV* sv, MAGIC* mg);
int (*svt_free)(SV* sv, MAGIC* mg);
- int (*svt_copy)(SV *sv, MAGIC* mg, SV *nsv, const char *name, I32 namlen);
+ int (*svt_copy)(SV *sv, MAGIC* mg, SV *nsv,
+ const char *name, I32 namlen);
int (*svt_dup)(MAGIC *mg, CLONE_PARAMS *param);
int (*svt_local)(SV *nsv, MAGIC *mg);
routines that perform additional actions depending on which function is
being called.
- Function pointer Action taken
- ---------------- ------------
- svt_get Do something before the value of the SV is retrieved.
- svt_set Do something after the SV is assigned a value.
- svt_len Report on the SV's length.
- svt_clear Clear something the SV represents.
- svt_free Free any extra storage associated with the SV.
+ Function pointer Action taken
+ ---------------- ------------
+ svt_get Do something before the value of the SV is
+ retrieved.
+ svt_set Do something after the SV is assigned a value.
+ svt_len Report on the SV's length.
+ svt_clear Clear something the SV represents.
+ svt_free Free any extra storage associated with the SV.
- svt_copy copy tied variable magic to a tied element
- svt_dup duplicate a magic structure during thread cloning
- svt_local copy magic to local value during 'local'
+ svt_copy copy tied variable magic to a tied element
+ svt_dup duplicate a magic structure during thread cloning
+ svt_local copy magic to local value during 'local'
For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
to an C<mg_type> of C<PERL_MAGIC_sv>) contains:
The current kinds of Magic Virtual Tables are:
- mg_type
- (old-style char and macro) MGVTBL Type of magic
- -------------------------- ------ -------------
- \0 PERL_MAGIC_sv vtbl_sv Special scalar variable
- A PERL_MAGIC_overload vtbl_amagic %OVERLOAD hash
- a PERL_MAGIC_overload_elem vtbl_amagicelem %OVERLOAD hash element
- c PERL_MAGIC_overload_table (none) Holds overload table (AMT)
- on stash
- B PERL_MAGIC_bm vtbl_bm Boyer-Moore (fast string search)
- D PERL_MAGIC_regdata vtbl_regdata Regex match position data
- (@+ and @- vars)
- d PERL_MAGIC_regdatum vtbl_regdatum Regex match position data
- element
- E PERL_MAGIC_env vtbl_env %ENV hash
- e PERL_MAGIC_envelem vtbl_envelem %ENV hash element
- f PERL_MAGIC_fm vtbl_fm Formline ('compiled' format)
- g PERL_MAGIC_regex_global vtbl_mglob m//g target / study()ed string
- H PERL_MAGIC_hints vtbl_hints %^H hash
- h PERL_MAGIC_hintselem vtbl_hintselem %^H hash element
- I PERL_MAGIC_isa vtbl_isa @ISA array
- i PERL_MAGIC_isaelem vtbl_isaelem @ISA array element
- k PERL_MAGIC_nkeys vtbl_nkeys scalar(keys()) lvalue
- L PERL_MAGIC_dbfile (none) Debugger %_<filename
- l PERL_MAGIC_dbline vtbl_dbline Debugger %_<filename element
- o PERL_MAGIC_collxfrm vtbl_collxfrm Locale collate transformation
- P PERL_MAGIC_tied vtbl_pack Tied array or hash
- p PERL_MAGIC_tiedelem vtbl_packelem Tied array or hash element
- q PERL_MAGIC_tiedscalar vtbl_packelem Tied scalar or handle
- r PERL_MAGIC_qr vtbl_qr precompiled qr// regex
- S PERL_MAGIC_sig vtbl_sig %SIG hash
- s PERL_MAGIC_sigelem vtbl_sigelem %SIG hash element
- t PERL_MAGIC_taint vtbl_taint Taintedness
- U PERL_MAGIC_uvar vtbl_uvar Available for use by extensions
- v PERL_MAGIC_vec vtbl_vec vec() lvalue
- V PERL_MAGIC_vstring (none) v-string scalars
- w PERL_MAGIC_utf8 vtbl_utf8 UTF-8 length+offset cache
- x PERL_MAGIC_substr vtbl_substr substr() lvalue
- y PERL_MAGIC_defelem vtbl_defelem Shadow "foreach" iterator
- variable / smart parameter
- vivification
- # PERL_MAGIC_arylen vtbl_arylen Array length ($#ary)
- . PERL_MAGIC_pos vtbl_pos pos() lvalue
- < PERL_MAGIC_backref vtbl_backref back pointer to a weak ref
- ~ PERL_MAGIC_ext (none) Available for use by extensions
- : PERL_MAGIC_symtab (none) hash used as symbol table
- % PERL_MAGIC_rhash (none) hash used as restricted hash
- @ PERL_MAGIC_arylen_p vtbl_arylen_p pointer to $#a from @a
-
+=for comment
+This table is generated by regen/mg_vtable.pl. Any changes made here
+will be lost.
+
+=for mg_vtable.pl begin
+
+ mg_type
+ (old-style char and macro) MGVTBL Type of magic
+ -------------------------- ------ -------------
+ \0 PERL_MAGIC_sv vtbl_sv Special scalar variable
+ # PERL_MAGIC_arylen vtbl_arylen Array length ($#ary)
+ % PERL_MAGIC_rhash (none) extra data for restricted
+ hashes
+ & PERL_MAGIC_proto (none) my sub prototype CV
+ . PERL_MAGIC_pos vtbl_pos pos() lvalue
+ : PERL_MAGIC_symtab (none) extra data for symbol
+ tables
+ < PERL_MAGIC_backref vtbl_backref for weak ref data
+ @ PERL_MAGIC_arylen_p (none) to move arylen out of XPVAV
+ B PERL_MAGIC_bm vtbl_regexp Boyer-Moore
+ (fast string search)
+ c PERL_MAGIC_overload_table vtbl_ovrld Holds overload table
+ (AMT) on stash
+ D PERL_MAGIC_regdata vtbl_regdata Regex match position data
+ (@+ and @- vars)
+ d PERL_MAGIC_regdatum vtbl_regdatum Regex match position data
+ element
+ E PERL_MAGIC_env vtbl_env %ENV hash
+ e PERL_MAGIC_envelem vtbl_envelem %ENV hash element
+ f PERL_MAGIC_fm vtbl_regexp Formline
+ ('compiled' format)
+ g PERL_MAGIC_regex_global vtbl_mglob m//g target
+ H PERL_MAGIC_hints vtbl_hints %^H hash
+ h PERL_MAGIC_hintselem vtbl_hintselem %^H hash element
+ I PERL_MAGIC_isa vtbl_isa @ISA array
+ i PERL_MAGIC_isaelem vtbl_isaelem @ISA array element
+ k PERL_MAGIC_nkeys vtbl_nkeys scalar(keys()) lvalue
+ L PERL_MAGIC_dbfile (none) Debugger %_<filename
+ l PERL_MAGIC_dbline vtbl_dbline Debugger %_<filename
+ element
+ N PERL_MAGIC_shared (none) Shared between threads
+ n PERL_MAGIC_shared_scalar (none) Shared between threads
+ o PERL_MAGIC_collxfrm vtbl_collxfrm Locale transformation
+ P PERL_MAGIC_tied vtbl_pack Tied array or hash
+ p PERL_MAGIC_tiedelem vtbl_packelem Tied array or hash element
+ q PERL_MAGIC_tiedscalar vtbl_packelem Tied scalar or handle
+ r PERL_MAGIC_qr vtbl_regexp precompiled qr// regex
+ S PERL_MAGIC_sig (none) %SIG hash
+ s PERL_MAGIC_sigelem vtbl_sigelem %SIG hash element
+ t PERL_MAGIC_taint vtbl_taint Taintedness
+ U PERL_MAGIC_uvar vtbl_uvar Available for use by
+ extensions
+ u PERL_MAGIC_uvar_elem (none) Reserved for use by
+ extensions
+ V PERL_MAGIC_vstring (none) SV was vstring literal
+ v PERL_MAGIC_vec vtbl_vec vec() lvalue
+ w PERL_MAGIC_utf8 vtbl_utf8 Cached UTF-8 information
+ x PERL_MAGIC_substr vtbl_substr substr() lvalue
+ y PERL_MAGIC_defelem vtbl_defelem Shadow "foreach" iterator
+ variable / smart parameter
+ vivification
+ ] PERL_MAGIC_checkcall vtbl_checkcall inlining/mutation of call
+ to this CV
+ ~ PERL_MAGIC_ext (none) Available for use by
+ extensions
+
+=for mg_vtable.pl end
When an uppercase and lowercase letter both exist in the table, then the
uppercase letter is typically used to represent some kind of composite type
=head2 Finding Magic
- MAGIC *mg_find(SV *sv, int type); /* Finds the magic pointer of that type */
+ MAGIC *mg_find(SV *sv, int type); /* Finds the magic pointer of that
+ * type */
This routine returns a pointer to a C<MAGIC> structure stored in the SV.
If the SV does not have that magical feature, C<NULL> is returned. If the
SV has multiple instances of that magical feature, the first one will be
returned. C<mg_findext> can be used to find a C<MAGIC> structure of an SV
-based on both it's magic type and it's magic virtual table:
+based on both its magic type and its magic virtual table:
MAGIC *mg_findext(SV *sv, int type, MGVTBL *vtbl);
PUSHs(sv_2mortal(newSVuv(an_unsigned_integer)))
PUSHs(sv_2mortal(newSVnv(a_double)))
PUSHs(sv_2mortal(newSVpv("Some String",0)))
- /* Although the last example is better written as the more efficient: */
+ /* Although the last example is better written as the more
+ * efficient: */
PUSHs(newSVpvs_flags("Some String", SVs_TEMP))
And now the Perl program calling C<tzname>, the two values will be assigned
XPUSHs(SV*)
-This macro automatically adjust the stack for you, if needed. Thus, you
+This macro automatically adjusts the stack for you, if needed. Thus, you
do not need to call C<EXTEND> to extend the stack.
Despite their suggestions in earlier versions of this document the macros
For more information, consult L<perlxs> and L<perlxstut>.
+=head2 Autoloading with XSUBs
+
+If an AUTOLOAD routine is an XSUB, as with Perl subroutines, Perl puts the
+fully-qualified name of the autoloaded subroutine in the $AUTOLOAD variable
+of the XSUB's package.
+
+But it also puts the same information in certain fields of the XSUB itself:
+
+ HV *stash = CvSTASH(cv);
+ const char *subname = SvPVX(cv);
+ STRLEN name_length = SvCUR(cv); /* in bytes */
+ U32 is_utf8 = SvUTF8(cv);
+
+C<SvPVX(cv)> contains just the sub name itself, not including the package.
+For an AUTOLOAD routine in UNIVERSAL or one of its superclasses,
+C<CvSTASH(cv)> returns NULL during a method call on a nonexistent package.
+
+B<Note>: Setting $AUTOLOAD stopped working in 5.6.1, which did not support
+XS AUTOLOAD subs at all. Perl 5.8.0 introduced the use of fields in the
+XSUB itself. Perl 5.16.0 restored the setting of $AUTOLOAD. If you need
+to support 5.8-5.14, use the XSUB's fields.
+
=head2 Calling Perl Routines from within C Programs
There are four routines that can be used to call a Perl subroutine from
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**);
+ I32 call_argv(const char*, I32, char**);
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
=head2 PerlIO
-The most recent development releases of Perl has been experimenting with
+The most recent development releases of Perl have been experimenting with
removing Perl's dependency on the "normal" standard I/O suite and allowing
other stdio implementations to be used. This involves creating a new
abstraction layer that then calls whichever implementation of stdio Perl
array is created, which is called a scratchpad for the current unit.
A scratchpad keeps SVs which are lexicals for the current unit and are
-targets for opcodes. One can deduce that an SV lives on a scratchpad
+targets for opcodes. A previous version of this document
+stated that one can deduce that an SV lives on a scratchpad
by looking on its flags: lexicals have C<SVs_PADMY> set, and
-I<target>s have C<SVs_PADTMP> set.
+I<target>s have C<SVs_PADTMP> set. But this have never been fully true.
+C<SVs_PADMY> could be set on a variable that no longer resides in any pad.
+While I<target>s do have C<SVs_PADTMP> set, it can also be set on variables
+that have never resided in a pad, but nonetheless act like I<target>s.
The correspondence between OPs and I<target>s is not 1-to-1. Different
OPs in the compile tree of the unit can use the same target, if this
static void my_peep(pTHX_ OP *o)
{
/* custom per-subroutine optimisation goes here */
- prev_peepp(o);
+ prev_peepp(aTHX_ o);
/* custom per-subroutine optimisation may also go here */
}
BOOT:
for(; o; o = o->op_next) {
/* custom per-op optimisation goes here */
}
- prev_rpeepp(orig_o);
+ prev_rpeepp(aTHX_ orig_o);
}
BOOT:
prev_rpeepp = PL_rpeepp;
the function Perl_GetVars(). The PERL_GLOBAL_STRUCT_PRIVATE goes
one step further, there is still a single struct (allocated in main()
either from heap or from stack) but there are no global data symbols
-pointing to it. In either case the global struct should be initialised
+pointing to it. In either case the global struct should be initialized
as the very first thing in main() using Perl_init_global_struct() and
correspondingly tear it down after perl_free() using Perl_free_global_struct(),
please see F<miniperlmain.c> for usage details. You may also need
S_incline(pTHX_ char *s)
STATIC becomes "static" in C, and may be #define'd to nothing in some
-configurations in future.
+configurations in the future.
A public function (i.e. part of the internal API, but not necessarily
sanctioned for use in extensions) begins like this:
Perl_sv_setiv(sv, num);
-You have to do nothing new in your extension to get this; since
+You don't have to do anything new in your extension to get this; since
the Perl library provides Perl_get_context(), it will all just
work.
=item n
-This does not need a interpreter context, so the definition has no
+This does not need an interpreter context, so the definition has no
C<pTHX>, and it follows that callers don't use C<aTHX>. (See
L</Background and PERL_IMPLICIT_CONTEXT>.)
In general, you either have to know what you're dealing with, or you
have to guess. The API function C<is_utf8_string> can help; it'll tell
you if a string contains only valid UTF-8 characters. However, it can't
-do the work for you. On a character-by-character basis, C<is_utf8_char>
+do the work for you. On a character-by-character basis,
+C<is_utf8_char_buf>
will tell you whether the current character in a string is valid UTF-8.
=head2 How does UTF-8 represent Unicode characters?
All bytes in a multi-byte UTF-8 character will have the high bit set,
so you can test if you need to do something special with this
character like this (the UTF8_IS_INVARIANT() is a macro that tests
-whether the byte can be encoded as a single byte even in UTF-8):
+whether the byte is encoded as a single byte even in UTF-8):
U8 *utf;
+ U8 *utf_end; /* 1 beyond buffer pointed to by utf */
UV uv; /* Note: a UV, not a U8, not a char */
+ STRLEN len; /* length of character in bytes */
if (!UTF8_IS_INVARIANT(*utf))
/* Must treat this as UTF-8 */
- uv = utf8_to_uv(utf);
+ uv = utf8_to_uvchr_buf(utf, utf_end, &len);
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
+You can also see in that example that we use C<utf8_to_uvchr_buf> to get the
+value of the character; the inverse function C<uvchr_to_utf8> is available
for putting a UV into UTF-8:
if (!UTF8_IS_INVARIANT(uv))
/* Must treat this as UTF8 */
- utf8 = uv_to_utf8(utf8, uv);
+ utf8 = uvchr_to_utf8(utf8, uv);
else
/* OK to treat this character as a byte */
*utf8++ = uv;
=item *
There's no way to tell if a string is UTF-8 or not. You can tell if an SV
-is UTF-8 by looking at is C<SvUTF8> flag. Don't forget to set the flag if
+is UTF-8 by looking at its C<SvUTF8> flag. Don't forget to set the flag if
something should be UTF-8. 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.
=item *
-If a string is UTF-8, B<always> use C<utf8_to_uv> to get at the value,
+If a string is UTF-8, B<always> use C<utf8_to_uvchr_buf> to get at the value,
unless C<UTF8_IS_INVARIANT(*s)> in which case you can use C<*s>.
=item *
When writing a character C<uv> to a UTF-8 string, B<always> use
-C<uv_to_utf8>, unless C<UTF8_IS_INVARIANT(uv))> in which case
+C<uvchr_to_utf8>, unless C<UTF8_IS_INVARIANT(uv))> in which case
you can use C<*s = uv>.
=item *
=head1 Custom Operators
-Custom operator support is a new experimental feature that allows you to
+Custom operator support is an experimental feature that allows you to
define your own ops. This is primarily to allow the building of
interpreters for other languages in the Perl core, but it also allows
optimizations through the creation of "macro-ops" (ops which perform the
a custom peephole optimizer with the C<optimize> module.
When you do this, you replace ordinary Perl ops with custom ops by
-creating ops with the type C<OP_CUSTOM> and the C<pp_addr> of your own
+creating ops with the type C<OP_CUSTOM> and the C<op_ppaddr> of your own
PP function. This should be defined in XS code, and should look like
the PP ops in C<pp_*.c>. You are responsible for ensuring that your op
takes the appropriate number of values from the stack, and you are
https://perl5.git.perl.org / perl5.git / blobdiff