=head1 NAME
-perlreapi - perl regular expression plugin interface
+perlreapi - Perl regular expression plugin interface
=head1 DESCRIPTION
-As of Perl 5.9.5 there is a new interface for plugging and using other
-regular expression engines than the default one.
+As of Perl 5.9.5 there is a new interface for plugging and using
+regular expression engines other 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_ const SV * const pattern, const U32 flags);
- I32 (*exec) (pTHX_ REGEXP * const rx, char* stringarg, char* strend,
- char* strbeg, I32 minend, SV* screamer,
+ REGEXP* (*comp) (pTHX_
+ const SV * const pattern, const U32 flags);
+ I32 (*exec) (pTHX_
+ REGEXP * const rx,
+ char* stringarg,
+ char* strend, char* strbeg,
+ SSize_t minend, SV* sv,
void* data, U32 flags);
- char* (*intuit) (pTHX_ REGEXP * const rx, SV *sv, char *strpos,
- char *strend, U32 flags,
+ char* (*intuit) (pTHX_
+ REGEXP * const rx, SV *sv,
+ const char * const strbeg,
+ 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,
+ 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
In order to install a new regexp handler, C<$^H{regcomp}> is set
to an integer which (when casted appropriately) resolves to one of these
-structures. When compiling, the C<comp> method is executed, and the
-resulting regexp structure's engine field is expected to point back at
+structures. When compiling, the C<comp> method is executed, and the
+resulting C<regexp> structure's engine field is expected to point back at
the same structure.
-The pTHX_ symbol in the definition is a macro used by perl under threading
+The pTHX_ symbol in the definition is a macro used by Perl under threading
to provide an extra argument to the routine holding a pointer back to
the interpreter that is executing the regexp. So under threading all
routines get an extra argument.
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 match. See L</The REGEXP structure> below for an explanation of
the individual fields in the REGEXP struct.
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
+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:
STRLEN plen;
char* exp = SvPV(pattern, plen);
char* xend = exp + plen;
-Since any scalar can be passed as a pattern it's possible to implement
+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
+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.
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.
+C<msixp> flags the regex was compiled with. It also contains
+additional info, such as if 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
+routine. The regex engine does not need to know if 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.
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
+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.
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
+some of them to invoke or disable some special behavior in Perl. The
flags along with any special behavior they cause are documented below:
The pattern modifiers:
=item C</x> - RXf_PMf_EXTENDED
-If present on a regex C<#> comments will be handled differently by the
+If present on a regex, C<"#"> comments will be handled differently by the
tokenizer in some cases.
TODO: Document those cases.
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
-when RXf_SKIPWHITE or RXf_WHITE is in effect. ASCII whitespace
+when RXf_SKIPWHITE or RXf_WHITE is in effect. 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 RXf_SPLIT
+This flag was removed in perl 5.18.0. C<split ' '> is now special-cased
+solely in the parser. RXf_SPLIT is still #defined, so you can test for it.
+This is how it used to work:
+
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:
+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);
=item RXf_SKIPWHITE
+This flag was removed in perl 5.18.0. It is still #defined, so you can
+set it, but doing so will have no effect. This is how it used to work:
+
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.
+on. What is considered whitespace depends on if the subject is a
+UTF-8 string and if 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.
+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
(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
+== '^'>), 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.
+without invoking the regex engine. The definition of whitespace varies
+depending on if the target string is a UTF-8 string and on
+if 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
+characters. The definition of character varies depending on if
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
+makes C<split //> much faster than it would otherwise be. It's even
faster than C<unpack>.
+=item RXf_NO_INPLACE_SUBST
+
+Added in perl 5.18.0, this flag indicates that a regular expression might
+perform an operation that would interfere with inplace substitution. For
+instance it might contain lookbehind, or assign to non-magical variables
+(such as $REGMARK and $REGERROR) during matching. C<s///> will skip
+certain optimisations when this is set.
+
=back
=head2 exec
I32 exec(pTHX_ REGEXP * const rx,
char *stringarg, char* strend, char* strbeg,
- I32 minend, SV* screamer,
+ SSize_t minend, SV* sv,
void* data, U32 flags);
Execute a regexp. The arguments are
The regular expression to execute.
-=item screamer
+=item sv
-This strangely-named arg is the SV to be matched against. Note that the
+This is the SV to be matched against. Note that the
actual char array to be matched against is supplied by the arguments
described below; the SV is just used to determine UTF8ness, C<pos()> etc.
=item strend
Pointer to the character following the physical end of the string (i.e.
-the \0).
+the C<\0>, if any).
=item stringarg
=head2 intuit
- char* intuit(pTHX_ REGEXP * const rx,
- SV *sv, char *strpos, char *strend,
- const U32 flags, struct re_scream_pos_data_s *data);
+ char* intuit(pTHX_
+ REGEXP * const rx,
+ SV *sv,
+ const char * const strbeg,
+ char *strpos,
+ char *strend,
+ 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
-pattern can't match. This is called as appropriate by the core
-depending on the values of the extflags member of the regexp
+or possibly if the regex engine should not be run because the
+pattern can't match. This is called, as appropriate, by the core,
+depending on the values of the C<extflags> member of the C<regexp>
structure.
+Arguments:
+
+ rx: the regex to match against
+ sv: the SV being matched: only used for utf8 flag; the string
+ itself is accessed via the pointers below. Note that on
+ something like an overloaded SV, SvPOK(sv) may be false
+ and the string pointers may point to something unrelated to
+ the SV itself.
+ strbeg: real beginning of string
+ strpos: the point in the string at which to begin matching
+ strend: pointer to the byte following the last char of the string
+ flags currently unused; set to 0
+ data: currently unused; set to NULL
+
+
=head2 checkstr
SV* checkstr(pTHX_ REGEXP * const rx);
void free(pTHX_ REGEXP * const rx);
-Called by perl when it is freeing a regexp pattern so that the engine
+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.
+C<regexp> structure. This is only responsible for freeing private data;
+Perl will handle releasing anything else contained in the C<regexp> structure.
=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
+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 C<paren> parameter will be C<1> for C<$1>, C<2> for C<$2> and so
+forth, and have these symbolic values for the special variables:
+
+ ${^PREMATCH} RX_BUFF_IDX_CARET_PREMATCH
+ ${^POSTMATCH} RX_BUFF_IDX_CARET_POSTMATCH
+ ${^MATCH} RX_BUFF_IDX_CARET_FULLMATCH
+ $` RX_BUFF_IDX_PREMATCH
+ $' RX_BUFF_IDX_POSTMATCH
+ $& RX_BUFF_IDX_FULLMATCH
+
+Note that in Perl 5.17.3 and earlier, the last three constants were also
+used for the caret variants of the variables.
+
The names have been chosen by analogy with L<Tie::Scalar> methods
-names with an additional B<LENGTH> callback for efficiency. However
+names with an additional B<LENGTH> callback for efficiency. However
named capture variables are currently not tied internally but
implemented via magic.
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
+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
+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
+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>
+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,
+ 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
+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:
(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)
+ 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_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
+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;
tie my $sv => "CaptureVar";
$sv =~ y/a/b/;
-Because C<$sv> is C<undef> when the C<y///> operator is applied to it
+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
+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,
+ 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:
+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;
=head2 Named capture callbacks
-Called to get/set the value of C<%+> and C<%-> as well as by some
+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
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
+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
RXapif_FIRSTKEY
RXapif_NEXTKEY
-Whether C<%+> or C<%-> is being operated on, if any.
+If C<%+> or C<%-> is being operated on, if any.
RXapif_ONE /* %+ */
RXapif_ALL /* %- */
-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
+If 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>.
RXapif_REGNAME
RXapif_REGNAMES_COUNT
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
+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
+releases. For instance this might be implemented by magic instead
(would need an extension to mgvtbl).
=head3 named_buff
=head3 named_buff_iter
- SV* (*named_buff_iter) (pTHX_ REGEXP * const rx, const SV * const lastkey,
+ 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 their package
-name for identification regardless of whether they implement methods
+qr//>). It is recommended that engines change this to their package
+name for identification regardless of if 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
+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:
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 multiple 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 C<regexp> structure. It will be called with the preconstructed new
+
C<regexp> structure as an argument, the C<pprivate> member will point at
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
+construct a copy and return a pointer to it (which Perl will then use to
overwrite the field as passed to this routine.)
This allows the engine to dupe its private data but also if necessary
=head2 op_comp
-This is private to the perl core and subject to change. Should be left
+This is private to the Perl core and subject to change. Should be left
null.
=head1 The REGEXP structure
-The REGEXP struct is defined in F<regexp.h>. All regex engines must be able to
+The REGEXP struct is defined in F<regexp.h>.
+All regex engines must be able to
correctly build such a structure in their L</comp> routine.
-The REGEXP structure contains all the data that perl needs to be aware of
-to properly work with the regular expression. It includes data about
-optimisations that perl can use to determine if the regex engine should
+The REGEXP structure contains all the data that Perl needs to be aware of
+to properly work with the regular expression. It includes data about
+optimisations that Perl can use to determine if the regex engine should
really be used, and various other control info that is needed to properly
-execute patterns in various contexts such as is the pattern anchored in
-some way, or what flags were used during the compile, or whether the
-program contains special constructs that perl needs to be aware of.
+execute patterns in various contexts, such as if the pattern anchored in
+some way, or what flags were used during the compile, or if 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 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
+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 re is this a lightweight copy of? */
struct regexp* mother_re;
- /* Information about the match that the perl core uses to manage things */
+ /* Information about the match that the Perl core uses to manage
+ * things */
U32 extflags; /* Flags used both externally and internally */
- I32 minlen; /* mininum possible length of string to match */
- I32 minlenret; /* mininum possible length of $& */
+ I32 minlen; /* mininum possible number of chars in */
+ string to match */
+ I32 minlenret; /* mininum possible number of chars in $& */
U32 gofs; /* chars left of pos that we search from */
/* substring data about strings that must appear
void *pprivate; /* Data private to the regex engine which
created this object. */
- /* Data about the last/current match. These are modified during matching*/
+ /* Data about the last/current match. These are modified during
+ * matching*/
U32 lastparen; /* highest close paren matched ($+) */
U32 lastcloseparen; /* last close paren matched ($^N) */
regexp_paren_pair *swap; /* Swap copy of *offs */
- regexp_paren_pair *offs; /* Array of offsets for (@-) and (@+) */
+ regexp_paren_pair *offs; /* Array of offsets for (@-) and
+ (@+) */
- char *subbeg; /* saved or original string so \digit works forever. */
+ char *subbeg; /* saved or original string so \digit works
+ forever. */
SV_SAVED_COPY /* If non-NULL, SV which is COW from original */
I32 sublen; /* Length of string pointed by subbeg */
- I32 suboffset; /* byte offset of subbeg from logical start of str */
+ I32 suboffset; /* byte offset of subbeg from logical start of
+ str */
I32 subcoffset; /* suboffset equiv, but in chars (for @-/@+) */
/* Information about the match that isn't often used */
char *wrapped; /* wrapped version of the pattern */
I32 wraplen; /* length of wrapped */
- I32 seen_evals; /* number of eval groups in the pattern - for security checks */
+ I32 seen_evals; /* number of eval groups in the pattern - for
+ security checks */
HV *paren_names; /* Optional hash of paren names */
/* Refcount of this regexp */
=head2 C<engine>
-This field points at a regexp_engine structure which contains pointers
-to the subroutines that are to be used for performing a match. It
+This field points at a C<regexp_engine> structure which contains pointers
+to the subroutines that are to be used for performing a match. It
is the compiling routine's responsibility to populate this field before
returning the regexp object.
Internally this is set to C<NULL> unless a custom engine is specified in
-C<$^H{regcomp}>, perl's own set of callbacks can be accessed in the struct
+C<$^H{regcomp}>, Perl's own set of callbacks can be accessed in the struct
pointed to by C<RE_ENGINE_PTR>.
=head2 C<mother_re>
=head2 C<extflags>
-This will be used by perl to see what flags the regexp was compiled
+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
+the L<comp|/comp> callback. See the L<comp|/comp> documentation for
valid flags.
=head2 C<minlen> C<minlenret>
-The minimum string length required for the pattern to match. This is used to
+The minimum string length (in characters) 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
-string than would allow a match. For instance there is no point in even
+string than would allow a match. For instance there is no point in even
starting the regex engine if the minlen is 10 but the string is only 5
-characters long. There is no way that the pattern can match.
+characters long. There is no way that the pattern can match.
-C<minlenret> is the minimum length of the string that would be found
-in $& after a match.
+C<minlenret> is the minimum length (in characters) of the string that would
+be found in $& after a match.
The difference between C<minlen> and C<minlenret> can be seen in the
following pattern:
/ns(?=\d)/
where the C<minlen> would be 3 but C<minlenret> would only be 2 as the \d is
-required to match but is not actually included in the matched content. This
+required to match but is not actually
+included in the matched content. This
distinction is particularly important as the substitution logic uses the
-C<minlenret> to tell whether it can do in-place substitution which can result in
-considerable speedup.
+C<minlenret> to tell if it can do in-place substitutions (these can
+result in considerable speed-up).
=head2 C<gofs>
=head2 C<substrs>
-Substring data about strings that must appear in the final match. This
-is currently only used internally by perl's engine for but might be
+Substring data about strings that must appear in the final match. This
+is currently only used internally by Perl's engine, but might be
used in the future for all engines for optimisations.
=head2 C<nparens>, C<lastparen>, and C<lastcloseparen>
=head2 C<pprivate>
-A void* pointing to an engine-defined data structure. The perl engine uses the
+A void* pointing to an engine-defined
+data structure. The Perl engine uses the
C<regexp_internal> structure (see L<perlreguts/Base Structures>) but a custom
engine should use something else.
=head2 C<swap>
-Unused. Left in for compatibility with perl 5.10.0.
+Unused. Left in for compatibility with Perl 5.10.0.
=head2 C<offs>
} regexp_paren_pair;
If C<< ->offs[num].start >> or C<< ->offs[num].end >> is C<-1> then that
-capture group did not match. C<< ->offs[0].start/end >> represents C<$&> (or
-C<${^MATCH> under C<//p>) and C<< ->offs[paren].end >> matches C<$$paren> where
+capture group did not match.
+C<< ->offs[0].start/end >> represents C<$&> (or
+C<${^MATCH}> under C<//p>) and C<< ->offs[paren].end >> matches C<$$paren> where
C<$paren >= 1>.
=head2 C<precomp> C<prelen>
-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
+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>
+checks
if 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.
=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,
+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
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
-occur at a floating offset from the start of the pattern. Used to do
+occur at a floating offset from the start of the pattern. Used to do
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.
the C<REXEC_COPY_SKIP_PRE> or C<REXEC_COPY_SKIP_POST> flags, an engine
can choose not to copy the full buffer (although it must still do so in
the presence of C<RXf_PMf_KEEPCOPY> or the relevant bits being set in
-C<PL_sawampersand>). In this case, it may set C<suboffset> to indicate the
+C<PL_sawampersand>). In this case, it may set C<suboffset> to indicate the
number of bytes from the logical start of the buffer to the physical start
-(i.e. C<subbeg>). It should also set C<subcoffset>, the number of
+(i.e. C<subbeg>). It should also set C<subcoffset>, the number of
characters in the offset. The latter is needed to support C<@-> and C<@+>
which work in characters, not bytes.
=head2 C<wrapped> C<wraplen>
-Stores the string C<qr//> stringifies to. The perl engine for example
+Stores the string C<qr//> stringifies to. The Perl engine for example
stores C<(?^:eek)> in the case of C<qr/eek/>.
When using a custom engine that doesn't support the C<(?:)> construct
=head2 C<seen_evals>
-This stores the number of eval groups in the pattern. This is used for security
+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//>.
=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
+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.
=head1 HISTORY
https://perl5.git.perl.org / perl5.git / blobdiff