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, inversion
+lists, used in regular expression data structures, are scalars, each
+consisting of an array of UVs which are accessed through PVs. 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:
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 an array (just
+The C<av_top_index> function returns the highest index value in an array (just
like $#array in Perl). If the array is empty, -1 is returned. The
C<av_fetch> function returns the value at index C<key>, but if C<lval>
is non-zero, then C<av_fetch> will store an undef value at that index.
This returns NULL if the variable does not exist.
-The hash algorithm is defined in the C<PERL_HASH(hash, key, klen)> macro:
+The hash algorithm is defined in the C<PERL_HASH> macro:
- hash = 0;
- while (klen--)
- hash = (hash * 33) + *key++;
- hash = hash + (hash >> 5); /* after 5.6 */
+ PERL_HASH(hash, key, klen)
-The last step was added in version 5.6 to improve distribution of
-lower bits in the resulting hash value.
+The exact implementation of this macro varies by architecture and version
+of perl, and the return value may change per invocation, so the value
+is only valid for the duration of a single perl process.
See L<Understanding the Magic of Tied Hashes and Arrays> for more
information on how to use the hash access functions on tied hashes.
The most useful types that will be returned are:
- SVt_IV Scalar
- SVt_NV Scalar
- SVt_PV Scalar
- SVt_RV Scalar
- SVt_PVAV Array
- SVt_PVHV Hash
- SVt_PVCV Code
- SVt_PVGV Glob (possibly a file handle)
- SVt_PVMG Blessed or Magical Scalar
+ < SVt_PVAV Scalar
+ SVt_PVAV Array
+ SVt_PVHV Hash
+ SVt_PVCV Code
+ SVt_PVGV Glob (possibly a file handle)
-See the F<sv.h> header file for more details.
+See L<perlapi/svtype> for more details.
=head2 Blessed References and Class Objects
=for mg_vtable.pl begin
mg_type
- (old-style char and macro) MGVTBL Type of magic
- -------------------------- ------ -------------
- \0 PERL_MAGIC_sv vtbl_sv Special scalar variable
- # PERL_MAGIC_arylen vtbl_arylen Array length ($#ary)
- % PERL_MAGIC_rhash (none) extra data for restricted
- hashes
- . PERL_MAGIC_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
- A PERL_MAGIC_overload vtbl_amagic %OVERLOAD hash
- a PERL_MAGIC_overload_elem vtbl_amagicelem %OVERLOAD hash element
- 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_regdata Formline
- ('compiled' format)
- G PERL_MAGIC_study vtbl_regexp study()ed string
- 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 vtbl_vstring 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 (none) inlining/mutation of call
- to this CV
- ~ PERL_MAGIC_ext (none) Available for use by
- extensions
+ (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
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.
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
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;
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?
whether the byte can be 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_uvchr(utf, &len);
+ 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_uvchr> to get the
+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:
=item *
-If a string is UTF-8, B<always> use C<utf8_to_uvchr> 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 *
=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