=head1 DESCRIPTION
-As of Perl 5.9.5 there is a new interface for using other regexp engines than
-the default one. Each engine is supposed to provide access to a constant
-structure of the following format:
+As of Perl 5.9.5 there is a new interface for plugging and using other
+regular expression engines than the default one.
+
+Each engine is supposed to provide access to a constant structure of the
+following format:
typedef struct regexp_engine {
- regexp* (*comp) (pTHX_ char* exp, char* xend, U32 pm_flags);
- I32 (*exec) (pTHX_ regexp* prog, char* stringarg, char* strend,
- char* strbeg, I32 minend, SV* screamer,
- void* data, U32 flags);
- char* (*intuit) (pTHX_ regexp *prog, SV *sv, char *strpos,
- char *strend, U32 flags,
- struct re_scream_pos_data_s *data);
- SV* (*checkstr) (pTHX_ regexp *prog);
- void (*free) (pTHX_ struct regexp* r);
- SV* (*numbered_buff_get) (pTHX_ const REGEXP * const rx, I32 paren, SV* usesv);
- SV* (*named_buff_get)(pTHX_ const REGEXP * const rx, SV* namesv, U32 flags);
- SV* (*qr_pkg)(pTHX_ const REGEXP * const rx);
+ REGEXP* (*comp) (pTHX_ const SV * const pattern, const U32 flags);
+ I32 (*exec) (pTHX_ REGEXP * const rx, char* stringarg, char* strend,
+ char* strbeg, I32 minend, SV* screamer,
+ void* data, U32 flags);
+ char* (*intuit) (pTHX_ REGEXP * const rx, SV *sv, char *strpos,
+ char *strend, U32 flags,
+ struct re_scream_pos_data_s *data);
+ SV* (*checkstr) (pTHX_ REGEXP * const rx);
+ void (*free) (pTHX_ REGEXP * const rx);
+ void (*numbered_buff_FETCH) (pTHX_ REGEXP * const rx, const I32 paren,
+ SV * const sv);
+ void (*numbered_buff_STORE) (pTHX_ REGEXP * const rx, const I32 paren,
+ SV const * const value);
+ I32 (*numbered_buff_LENGTH) (pTHX_ REGEXP * const rx, const SV * const sv,
+ const I32 paren);
+ SV* (*named_buff) (pTHX_ REGEXP * const rx, SV * const key,
+ SV * const value, U32 flags);
+ SV* (*named_buff_iter) (pTHX_ REGEXP * const rx, const SV * const lastkey,
+ const U32 flags);
+ SV* (*qr_package)(pTHX_ REGEXP * const rx);
#ifdef USE_ITHREADS
- void* (*dupe) (pTHX_ const regexp *r, CLONE_PARAMS *param);
+ void* (*dupe) (pTHX_ REGEXP * const rx, CLONE_PARAMS *param);
#endif
- } regexp_engine;
When a regexp is compiled, its C<engine> field is then set to point at
-the appropriate structure so that when it needs to be used Perl can find
+the appropriate structure, so that when it needs to be used Perl can find
the right routines to do so.
In order to install a new regexp handler, C<$^H{regcomp}> is set
the interpreter that is executing the regexp. So under threading all
routines get an extra argument.
-The routines are as follows:
+=head1 Callbacks
=head2 comp
- regexp* comp(char *exp, char *xend, U32 flags);
+ REGEXP* comp(pTHX_ const SV * const pattern, const U32 flags);
-Compile the pattern between exp and xend using the given flags and return a
-pointer to a prepared regexp structure that can perform the match. See L</The
-REGEXP structure> below for an explanation of the individual fields in the
-REGEXP struct.
+Compile the pattern stored in C<pattern> using the given C<flags> and
+return a pointer to a prepared C<REGEXP> structure that can perform
+the match. See L</The REGEXP structure> below for an explanation of
+the individual fields in the REGEXP struct.
-The C<flags> paramater is a bitfield which indicates which of the
-C<msixk> flags the regex was compiled with. In addition it contains
-info about whether C<use locale> is in effect and optimization info
-for C<split>. A regex engine might want to use the same split
-optimizations with a different syntax, for instance a Perl6 engine
-would treat C<split /^^/> equivalently to perl's C<split /^/>, see
-L<split documentation|perlfunc> and the relevant code in C<pp_split>
-in F<pp.c> to find out whether your engine should be setting these.
+The C<pattern> parameter is the scalar that was used as the
+pattern. previous versions of perl would pass two C<char*> indicating
+the start and end of the stringified pattern, the following snippet can
+be used to get the old parameters:
-The C<eogc> flags are stripped out before being passed to the comp
-routine. The regex engine does not need to know whether any of these
-are set.
+ STRLEN plen;
+ char* exp = SvPV(pattern, plen);
+ char* xend = exp + plen;
-=over 4
+Since any scalar can be passed as a pattern it's possible to implement
+an engine that does something with an array (C<< "ook" =~ [ qw/ eek
+hlagh / ] >>) or with the non-stringified form of a compiled regular
+expression (C<< "ook" =~ qr/eek/ >>). perl's own engine will always
+stringify everything using the snippet above but that doesn't mean
+other engines have to.
-=item RXf_SKIPWHITE
+The C<flags> parameter is a bitfield which indicates which of the
+C<msixp> flags the regex was compiled with. It also contains
+additional info such as whether C<use locale> is in effect.
+
+The C<eogc> flags are stripped out before being passed to the comp
+routine. The regex engine does not need to know whether any of these
+are set as those flags should only affect what perl does with the
+pattern and its match variables, not how it gets compiled and
+executed.
-C<split ' '> or C<split> with no arguments (which really means
-C<split(' ', $_> see L<split|perlfunc>).
+By the time the comp callback is called, some of these flags have
+already had effect (noted below where applicable). However most of
+their effect occurs after the comp callback has run in routines that
+read the C<< rx->extflags >> field which it populates.
-=item RXf_START_ONLY
+In general the flags should be preserved in C<< rx->extflags >> after
+compilation, although the regex engine might want to add or delete
+some of them to invoke or disable some special behavior in perl. The
+flags along with any special behavior they cause are documented below:
-Set if the pattern is C</^/> (C<<r->prelen == 1 && r->precomp[0] ==
-'^'>>). Will be used by the C<split> operator to split the given
-string on C<\n> (even under C</^/s>, see L<split|perlfunc>).
+The pattern modifiers:
-=item RXf_WHITE
+=over 4
-Set if the pattern is exactly C</\s+/> and used by C<split>, the
-definition of whitespace varies depending on whether RXf_UTF8 or
-RXf_PMf_LOCALE is set.
+=item C</m> - RXf_PMf_MULTILINE
-=item RXf_PMf_LOCALE
+If this is in C<< rx->extflags >> it will be passed to
+C<Perl_fbm_instr> by C<pp_split> which will treat the subject string
+as a multi-line string.
-Makes C<split> use the locale dependant definition of whitespace under C<use
-locale> when RXf_SKIPWHITE or RXf_WHITE is in effect. Under ASCII whitespace is
-defined as per L<isSPACE|perlapi/ISSPACE>, and by the internal macros
-C<is_utf8_space> under UTF-8 and C<isSPACE_LC> under C<use locale>.
+=item C</s> - RXf_PMf_SINGLELINE
-=item RXf_PMf_MULTILINE
+=item C</i> - RXf_PMf_FOLD
-The C</m> flag, this ends up being passed to C<Perl_fbm_instr> by
-C<pp_split> regardless of the engine.
+=item C</x> - RXf_PMf_EXTENDED
-=item RXf_PMf_SINGLELINE
+If present on a regex C<#> comments will be handled differently by the
+tokenizer in some cases.
-The C</s> flag. Guaranteed not to be used outside the regex engine.
+TODO: Document those cases.
-=item RXf_PMf_FOLD
+=item C</p> - RXf_PMf_KEEPCOPY
-The C</i> flag. Guaranteed not to be used outside the regex engine.
+=item Character set
-=item RXf_PMf_EXTENDED
+The character set semantics are determined by an enum that is contained
+in this field. This is still experimental and subject to change, but
+the current interface returns the rules by use of the in-line function
+C<get_regex_charset(const U32 flags)>. The only currently documented
+value returned from it is REGEX_LOCALE_CHARSET, which is set if
+C<use locale> is in effect. If present in C<< rx->extflags >>
+C<split> will use the locale dependent definition of whitespace under
+when RXf_SKIPWHITE or RXf_WHITE are in effect. Under ASCII whitespace
+is defined as per L<isSPACE|perlapi/isSPACE>, and by the internal
+macros C<is_utf8_space> under UTF-8 and C<isSPACE_LC> under C<use
+locale>.
-The C</x> flag. Guaranteed not to be used outside the regex
-engine. However if present on a regex C<#> comments will be stripped
-by the tokenizer regardless of the engine currently in use.
+=back
-=item RXf_PMf_KEEPCOPY
+Additional flags:
-The C</k> flag.
+=over 4
=item RXf_UTF8
Set if the pattern is L<SvUTF8()|perlapi/SvUTF8>, set by Perl_pmruntime.
+A regex engine may want to set or disable this flag during
+compilation. The perl engine for instance may upgrade non-UTF-8
+strings to UTF-8 if the pattern includes constructs such as C<\x{...}>
+that can only match Unicode values.
+
+=item RXf_SPLIT
+
+If C<split> is invoked as C<split ' '> or with no arguments (which
+really means C<split(' ', $_)>, see L<split|perlfunc/split>), perl will
+set this flag. The regex engine can then check for it and set the
+SKIPWHITE and WHITE extflags. To do this the perl engine does:
+
+ if (flags & RXf_SPLIT && r->prelen == 1 && r->precomp[0] == ' ')
+ r->extflags |= (RXf_SKIPWHITE|RXf_WHITE);
+
=back
-In general these flags should be preserved in regex->extflags after
-compilation, although it is possible the regex includes constructs
-that changes them. The perl engine for instance may upgrade non-utf8
-strings to utf8 if the pattern includes constructs such as C<\x{...}>
-that can only match unicode values. RXf_SKIPWHITE should always be
-preserved verbatim in regex->extflags.
+These flags can be set during compilation to enable optimizations in
+the C<split> operator.
+
+=over 4
+
+=item RXf_SKIPWHITE
+
+If the flag is present in C<< rx->extflags >> C<split> will delete
+whitespace from the start of the subject string before it's operated
+on. What is considered whitespace depends on whether the subject is a
+UTF-8 string and whether the C<RXf_PMf_LOCALE> flag is set.
+
+If RXf_WHITE is set in addition to this flag C<split> will behave like
+C<split " "> under the perl engine.
+
+=item RXf_START_ONLY
+
+Tells the split operator to split the target string on newlines
+(C<\n>) without invoking the regex engine.
+
+Perl's engine sets this if the pattern is C</^/> (C<plen == 1 && *exp
+== '^'>), even under C</^/s>, see L<split|perlfunc>. Of course a
+different regex engine might want to use the same optimizations
+with a different syntax.
+
+=item RXf_WHITE
+
+Tells the split operator to split the target string on whitespace
+without invoking the regex engine. The definition of whitespace varies
+depending on whether the target string is a UTF-8 string and on
+whether RXf_PMf_LOCALE is set.
+
+Perl's engine sets this flag if the pattern is C<\s+>.
+
+=item RXf_NULL
+
+Tells the split operator to split the target string on
+characters. The definition of character varies depending on whether
+the target string is a UTF-8 string.
+
+Perl's engine sets this flag on empty patterns, this optimization
+makes C<split //> much faster than it would otherwise be. It's even
+faster than C<unpack>.
+
+=back
=head2 exec
- I32 exec(regexp* prog,
+ I32 exec(pTHX_ REGEXP * const rx,
char *stringarg, char* strend, char* strbeg,
I32 minend, SV* screamer,
void* data, U32 flags);
=head2 intuit
- char* intuit( regexp *prog,
+ char* intuit(pTHX_ REGEXP * const rx,
SV *sv, char *strpos, char *strend,
- U32 flags, struct re_scream_pos_data_s *data);
+ const U32 flags, struct re_scream_pos_data_s *data);
Find the start position where a regex match should be attempted,
or possibly whether the regex engine should not be run because the
=head2 checkstr
- SV* checkstr(regexp *prog);
+ SV* checkstr(pTHX_ REGEXP * const rx);
Return a SV containing a string that must appear in the pattern. Used
by C<split> for optimising matches.
=head2 free
- void free(regexp *prog);
+ void free(pTHX_ REGEXP * const rx);
Called by perl when it is freeing a regexp pattern so that the engine
can release any resources pointed to by the C<pprivate> member of the
regexp structure. This is only responsible for freeing private data;
perl will handle releasing anything else contained in the regexp structure.
-=head2 numbered_buff_get
+=head2 Numbered capture callbacks
+
+Called to get/set the value of C<$`>, C<$'>, C<$&> and their named
+equivalents, ${^PREMATCH}, ${^POSTMATCH} and $^{MATCH}, as well as the
+numbered capture groups (C<$1>, C<$2>, ...).
+
+The C<paren> parameter will be C<-2> for C<$`>, C<-1> for C<$'>, C<0>
+for C<$&>, C<1> for C<$1> and so forth.
+
+The names have been chosen by analogy with L<Tie::Scalar> methods
+names with an additional B<LENGTH> callback for efficiency. However
+named capture variables are currently not tied internally but
+implemented via magic.
+
+=head3 numbered_buff_FETCH
+
+ void numbered_buff_FETCH(pTHX_ REGEXP * const rx, const I32 paren,
+ SV * const sv);
+
+Fetch a specified numbered capture. C<sv> should be set to the scalar
+to return, the scalar is passed as an argument rather than being
+returned from the function because when it's called perl already has a
+scalar to store the value, creating another one would be
+redundant. The scalar can be set with C<sv_setsv>, C<sv_setpvn> and
+friends, see L<perlapi>.
+
+This callback is where perl untaints its own capture variables under
+taint mode (see L<perlsec>). See the C<Perl_reg_numbered_buff_fetch>
+function in F<regcomp.c> for how to untaint capture variables if
+that's something you'd like your engine to do as well.
+
+=head3 numbered_buff_STORE
+
+ void (*numbered_buff_STORE) (pTHX_ REGEXP * const rx, const I32 paren,
+ SV const * const value);
+
+Set the value of a numbered capture variable. C<value> is the scalar
+that is to be used as the new value. It's up to the engine to make
+sure this is used as the new value (or reject it).
+
+Example:
+
+ if ("ook" =~ /(o*)/) {
+ # `paren' will be `1' and `value' will be `ee'
+ $1 =~ tr/o/e/;
+ }
+
+Perl's own engine will croak on any attempt to modify the capture
+variables, to do this in another engine use the following callback
+(copied from C<Perl_reg_numbered_buff_store>):
+
+ void
+ Example_reg_numbered_buff_store(pTHX_ REGEXP * const rx, const I32 paren,
+ SV const * const value)
+ {
+ PERL_UNUSED_ARG(rx);
+ PERL_UNUSED_ARG(paren);
+ PERL_UNUSED_ARG(value);
+
+ if (!PL_localizing)
+ Perl_croak(aTHX_ PL_no_modify);
+ }
+
+Actually perl will not I<always> croak in a statement that looks
+like it would modify a numbered capture variable. This is because the
+STORE callback will not be called if perl can determine that it
+doesn't have to modify the value. This is exactly how tied variables
+behave in the same situation:
+
+ package CaptureVar;
+ use base 'Tie::Scalar';
+
+ sub TIESCALAR { bless [] }
+ sub FETCH { undef }
+ sub STORE { die "This doesn't get called" }
+
+ package main;
+
+ tie my $sv => "CaptureVar";
+ $sv =~ y/a/b/;
+
+Because C<$sv> is C<undef> when the C<y///> operator is applied to it
+the transliteration won't actually execute and the program won't
+C<die>. This is different to how 5.8 and earlier versions behaved
+since the capture variables were READONLY variables then, now they'll
+just die when assigned to in the default engine.
+
+=head3 numbered_buff_LENGTH
+
+ I32 numbered_buff_LENGTH (pTHX_ REGEXP * const rx, const SV * const sv,
+ const I32 paren);
+
+Get the C<length> of a capture variable. There's a special callback
+for this so that perl doesn't have to do a FETCH and run C<length> on
+the result, since the length is (in perl's case) known from an offset
+stored in C<< rx->offs >> this is much more efficient:
+
+ I32 s1 = rx->offs[paren].start;
+ I32 s2 = rx->offs[paren].end;
+ I32 len = t1 - s1;
+
+This is a little bit more complex in the case of UTF-8, see what
+C<Perl_reg_numbered_buff_length> does with
+L<is_utf8_string_loclen|perlapi/is_utf8_string_loclen>.
+
+=head2 Named capture callbacks
+
+Called to get/set the value of C<%+> and C<%-> as well as by some
+utility functions in L<re>.
+
+There are two callbacks, C<named_buff> is called in all the cases the
+FETCH, STORE, DELETE, CLEAR, EXISTS and SCALAR L<Tie::Hash> callbacks
+would be on changes to C<%+> and C<%-> and C<named_buff_iter> in the
+same cases as FIRSTKEY and NEXTKEY.
+
+The C<flags> parameter can be used to determine which of these
+operations the callbacks should respond to, the following flags are
+currently defined:
+
+Which L<Tie::Hash> operation is being performed from the Perl level on
+C<%+> or C<%+>, if any:
+
+ RXapif_FETCH
+ RXapif_STORE
+ RXapif_DELETE
+ RXapif_CLEAR
+ RXapif_EXISTS
+ RXapif_SCALAR
+ RXapif_FIRSTKEY
+ RXapif_NEXTKEY
+
+Whether C<%+> or C<%-> is being operated on, if any.
- SV* numbered_buff_get(pTHX_ const REGEXP * const rx, I32 paren, SV* usesv);
+ RXapif_ONE /* %+ */
+ RXapif_ALL /* %- */
-TODO: document
+Whether this is being called as C<re::regname>, C<re::regnames> or
+C<re::regnames_count>, if any. The first two will be combined with
+C<RXapif_ONE> or C<RXapif_ALL>.
-=head2 named_buff_get
+ RXapif_REGNAME
+ RXapif_REGNAMES
+ RXapif_REGNAMES_COUNT
- SV* named_buff_get(pTHX_ const REGEXP * const rx, SV* namesv, U32 flags);
+Internally C<%+> and C<%-> are implemented with a real tied interface
+via L<Tie::Hash::NamedCapture>. The methods in that package will call
+back into these functions. However the usage of
+L<Tie::Hash::NamedCapture> for this purpose might change in future
+releases. For instance this might be implemented by magic instead
+(would need an extension to mgvtbl).
-TODO: document
+=head3 named_buff
-=head2 qr_pkg
+ SV* (*named_buff) (pTHX_ REGEXP * const rx, SV * const key,
+ SV * const value, U32 flags);
- SV* qr_pkg(pTHX_ const REGEXP * const rx);
+=head3 named_buff_iter
+
+ SV* (*named_buff_iter) (pTHX_ REGEXP * const rx, const SV * const lastkey,
+ const U32 flags);
+
+=head2 qr_package
+
+ SV* qr_package(pTHX_ REGEXP * const rx);
The package the qr// magic object is blessed into (as seen by C<ref
-qr//>). It is recommended that engines change this to its package
-name, for instance:
+qr//>). It is recommended that engines change this to their package
+name for identification regardless of whether they implement methods
+on the object.
+
+The package this method returns should also have the internal
+C<Regexp> package in its C<@ISA>. C<< qr//->isa("Regexp") >> should always
+be true regardless of what engine is being used.
+
+Example implementation might be:
SV*
- Example_reg_qr_pkg(pTHX_ const REGEXP * const rx)
+ Example_qr_package(pTHX_ REGEXP * const rx)
{
PERL_UNUSED_ARG(rx);
return newSVpvs("re::engine::Example");
my $re = qr//;
$re->meth; # dispatched to re::engine::Example::meth()
-To retrieve the C<REGEXP> object from the scalar in an XS function use the
-following snippet:
-
- void meth(SV * rv)
- PPCODE:
- MAGIC * mg;
- REGEXP * re;
-
- if (SvMAGICAL(sv))
- mg_get(sv);
- if (SvROK(sv) &&
- (sv = (SV*)SvRV(sv)) && /* assignment deliberate */
- SvTYPE(sv) == SVt_PVMG &&
- (mg = mg_find(sv, PERL_MAGIC_qr))) /* assignment deliberate */
- {
- re = (REGEXP *)mg->mg_obj;
- }
-
-Or use the (CURRENTLY UNDOCUMENETED!) C<Perl_get_re_arg> function:
+To retrieve the C<REGEXP> object from the scalar in an XS function use
+the C<SvRX> macro, see L<"REGEXP Functions" in perlapi|perlapi/REGEXP
+Functions>.
void meth(SV * rv)
PPCODE:
- const REGEXP * const re = (REGEXP *)Perl_get_re_arg( aTHX_ rv, 0, NULL );
+ REGEXP * re = SvRX(sv);
=head2 dupe
- void* dupe(const regexp *r, CLONE_PARAMS *param);
+ void* dupe(pTHX_ REGEXP * const rx, CLONE_PARAMS *param);
On threaded builds a regexp may need to be duplicated so that the pattern
-can be used by mutiple threads. This routine is expected to handle the
+can be used by multiple threads. This routine is expected to handle the
duplication of any private data pointed to by the C<pprivate> member of
the regexp structure. It will be called with the preconstructed new
regexp structure as an argument, the C<pprivate> member will point at
-the B<old> private structue, and it is this routine's responsibility to
+the B<old> private structure, and it is this routine's responsibility to
construct a copy and return a pointer to it (which perl will then use to
overwrite the field as passed to this routine.)
some way, or what flags were used during the compile, or whether the
program contains special constructs that perl needs to be aware of.
-In addition it contains two fields that are intended for the private use
-of the regex engine that compiled the pattern. These are the C<intflags>
-and pprivate members. The C<pprivate> is a void pointer to an arbitrary
-structure whose use and management is the responsibility of the compiling
-engine. perl will never modify either of these values.
+In addition it contains two fields that are intended for the private
+use of the regex engine that compiled the pattern. These are the
+C<intflags> and C<pprivate> members. C<pprivate> is a void pointer to
+an arbitrary structure whose use and management is the responsibility
+of the compiling engine. perl will never modify either of these
+values.
typedef struct regexp {
/* what engine created this regexp? */
in the final match, used for optimisations */
struct reg_substr_data *substrs;
- U32 nparens; /* number of capture buffers */
+ U32 nparens; /* number of capture groups */
/* private engine specific data */
U32 intflags; /* Engine Specific Internal flags */
I32 prelen; /* length of precomp */
const char *precomp; /* pre-compilation regular expression */
- /* wrapped can't be const char*, as it is returned by sv_2pv_flags */
char *wrapped; /* wrapped version of the pattern */
I32 wraplen; /* length of wrapped */
The fields are discussed in more detail below:
-=over 4
-
-=item C<engine>
+=head2 C<engine>
This field points at a regexp_engine structure which contains pointers
to the subroutines that are to be used for performing a match. It
C<$^H{regcomp}>, perl's own set of callbacks can be accessed in the struct
pointed to by C<RE_ENGINE_PTR>.
-=item C<mother_re>
+=head2 C<mother_re>
TODO, see L<http://www.mail-archive.com/perl5-changes@perl.org/msg17328.html>
-=item C<extflags>
+=head2 C<extflags>
-This will be used by perl to see what flags the regexp was compiled with, this
-will normally be set to the value of the flags parameter on L</comp>.
+This will be used by perl to see what flags the regexp was compiled
+with, this will normally be set to the value of the flags parameter by
+the L<comp|/comp> callback. See the L<comp|/comp> documentation for
+valid flags.
-=item C<minlen> C<minlenret>
+=head2 C<minlen> C<minlenret>
The minimum string length required for the pattern to match. This is used to
prune the search space by not bothering to match any closer to the end of a
where the C<minlen> would be 3 but C<minlenret> would only be 2 as the \d is
required to match but is not actually included in the matched content. This
distinction is particularly important as the substitution logic uses the
-C<minlenret> to tell whether it can do in-place substition which can result in
+C<minlenret> to tell whether it can do in-place substitution which can result in
considerable speedup.
-=item C<gofs>
+=head2 C<gofs>
Left offset from pos() to start match at.
-=item C<substrs>
+=head2 C<substrs>
-TODO: document
+Substring data about strings that must appear in the final match. This
+is currently only used internally by perl's engine for but might be
+used in the future for all engines for optimisations.
-=item C<nparens>, C<lasparen>, and C<lastcloseparen>
+=head2 C<nparens>, C<lasparen>, and C<lastcloseparen>
These fields are used to keep track of how many paren groups could be matched
in the pattern, which was the last open paren to be entered, and which was
the last close paren to be entered.
-=item C<intflags>
+=head2 C<intflags>
The engine's private copy of the flags the pattern was compiled with. Usually
-this is the same as C<extflags> unless the engine chose to modify one of them
+this is the same as C<extflags> unless the engine chose to modify one of them.
A void* pointing to an engine-defined data structure. The perl engine uses the
C<regexp_internal> structure (see L<perlreguts/Base Structures>) but a custom
engine should use something else.
-=item C<swap>
+=head2 C<swap>
-TODO: document
+Unused. Left in for compatibility with perl 5.10.0.
-=item C<offs>
+=head2 C<offs>
A C<regexp_paren_pair> structure which defines offsets into the string being
matched which correspond to the C<$&> and C<$1>, C<$2> etc. captures, the
} regexp_paren_pair;
If C<< ->offs[num].start >> or C<< ->offs[num].end >> is C<-1> then that
-capture buffer did not match. C<< ->offs[0].start/end >> represents C<$&> (or
+capture group did not match. C<< ->offs[0].start/end >> represents C<$&> (or
C<${^MATCH> under C<//p>) and C<< ->offs[paren].end >> matches C<$$paren> where
C<$paren >= 1>.
-=
item C<precomp> C<prelen>
+=
head2 C<precomp> C<prelen>
-Used for debugging purposes. C<precomp> holds a copy of the pattern
-that was compiled and C<prelen> its length.
+Used for optimisations. C<precomp> holds a copy of the pattern that
+was compiled and C<prelen> its length. When a new pattern is to be
+compiled (such as inside a loop) the internal C<regcomp> operator
+checks whether the last compiled C<REGEXP>'s C<precomp> and C<prelen>
+are equivalent to the new one, and if so uses the old pattern instead
+of compiling a new one.
-=item C<paren_names>
+The relevant snippet from C<Perl_pp_regcomp>:
-This is a hash used internally to track named capture buffers and their
+ if (!re || !re->precomp || re->prelen != (I32)len ||
+ memNE(re->precomp, t, len))
+ /* Compile a new pattern */
+
+=head2 C<paren_names>
+
+This is a hash used internally to track named capture groups and their
offsets. The keys are the names of the buffers the values are dualvars,
with the IV slot holding the number of buffers with the given name and the
pv being an embedded array of I32. The values may also be contained
independently in the data array in cases where named backreferences are
used.
-=item C<reg_substr_data>
+=head2 C<substrs>
Holds information on the longest string that must occur at a fixed
offset from the start of the pattern, and the longest string that must
Fast-Boyer-Moore searches on the string to find out if its worth using
the regex engine at all, and if so where in the string to search.
-=item C<startp>, C<endp>
-
-These fields store arrays that are used to hold the offsets of the begining
-and end of each capture group that has matched. -1 is used to indicate no match.
-
-These are the source for @- and @+.
-
-=item C<subbeg> C<sublen> C<saved_copy>
-
- #define SAVEPVN(p,n) ((p) ? savepvn(p,n) : NULL)
- if (RX_MATCH_COPIED(ret))
- ret->subbeg = SAVEPVN(ret->subbeg, ret->sublen);
- else
- ret->subbeg = NULL;
+=head2 C<subbeg> C<sublen> C<saved_copy>
-C<PL_sawampersand || rx->extflags & RXf_PMf_KEEPCOPY>
+Used during execution phase for managing search and replace patterns.
-These are used during execution phase for managing search and replace
-patterns.
+=head2 C<wrapped> C<wraplen>
-=item C<wrapped> C<wraplen>
+Stores the string C<qr//> stringifies to. The perl engine for example
+stores C<(?^:eek)> in the case of C<qr/eek/>.
-Stores the string C<qr//> stringifies to, for example C<(?-xism:eek)>
-in the case of C<qr/eek/>.
-
-When using a custom engine that doesn't support the C<(?:)> construct for
-inline modifiers it's best to have C<qr//> stringify to the supplied pattern,
-note that this will create invalid patterns in cases such as:
+When using a custom engine that doesn't support the C<(?:)> construct
+for inline modifiers, it's probably best to have C<qr//> stringify to
+the supplied pattern, note that this will create undesired patterns in
+cases such as:
my $x = qr/a|b/; # "a|b"
- my $y = qr/c/; # "c"
+ my $y = qr/c/i; # "c"
my $z = qr/$x$y/; # "a|bc"
-There's no solution for such problems other than making the custom engine
-understand some for of inline modifiers.
-
-The C<Perl_reg_stringify> in F<regcomp.c> does the stringification work.
+There's no solution for this problem other than making the custom
+engine understand a construct like C<(?:)>.
-=item C<seen_evals>
+=head2 C<seen_evals>
This stores the number of eval groups in the pattern. This is used for security
purposes when embedding compiled regexes into larger patterns with C<qr//>.
-=item C<refcnt>
+=head2 C<refcnt>
The number of times the structure is referenced. When this falls to 0 the
regexp is automatically freed by a call to pregfree. This should be set to 1 in
each engine's L</comp> routine.
-=back
-
-=head2 De-allocation and Cloning
-
-Any patch that adds data items to the REGEXP struct will need to include
-changes to F<sv.c> (C<Perl_re_dup()>) and F<regcomp.c> (C<pregfree()>). This
-involves freeing or cloning items in the regexp's data array based on the data
-item's type.
-
=head1 HISTORY
Originally part of L<perlreguts>.
https://perl5.git.perl.org / perl5.git / blobdiff