=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_ const SV * const pattern, const U32 flags);
#ifdef USE_ITHREADS
void* (*dupe) (pTHX_ REGEXP * const rx, CLONE_PARAMS *param);
#endif
+ REGEXP* (*op_comp) (...);
+
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 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 stringifed pattern, the following snippet can
+the start and end of the stringified pattern, the following snippet can
be used to get the old parameters:
STRLEN plen;
stringify everything using the snippet above but that doesn't mean
other engines have to.
-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<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 & executed.
+pattern and its match variables, not how it gets compiled and
+executed.
-=over 4
+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_SKIPWHITE
+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:
-C<split ' '> or C<split> with no arguments (which really means
-C<split(' ', $_> see L<split|perlfunc>).
+The pattern modifiers:
-=item RXf_START_ONLY
+=over 4
-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>).
+=item C</m> - RXf_PMf_MULTILINE
-=item RXf_WHITE
+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.
-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</s> - RXf_PMf_SINGLELINE
-=item RXf_PMf_LOCALE
+=item C</i> - RXf_PMf_FOLD
-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</x> - RXf_PMf_EXTENDED
-=item RXf_PMf_MULTILINE
+If present on a regex C<#> comments will be handled differently by the
+tokenizer in some cases.
-The C</m> flag, this ends up being passed to C<Perl_fbm_instr> by
-C<pp_split> regardless of the engine.
+TODO: Document those cases.
-=item RXf_PMf_SINGLELINE
+=item C</p> - RXf_PMf_KEEPCOPY
-The C</s> flag. Guaranteed not to be used outside the regex engine.
+TODO: Document this
-=item RXf_PMf_FOLD
+=item Character set
-The C</i> flag. Guaranteed not to be used outside the regex engine.
+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
+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_PMf_EXTENDED
+=back
-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.
+Additional flags:
-=item RXf_PMf_KEEPCOPY
+=over 4
-The C</p> flag.
+=item RXf_SPLIT
-=item RXf_UTF8
+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:
-Set if the pattern is L<SvUTF8()|perlapi/SvUTF8>, set by Perl_pmruntime.
+ 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 C<< rx->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 C<< 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 minend, SV* screamer,
void* data, U32 flags);
-Execute a regexp.
+Execute a regexp. The arguments are
+
+=over 4
+
+=item rx
+
+The regular expression to execute.
+
+=item screamer
+
+This strangely-named arg 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 strbeg
+
+Pointer to the physical start of the string.
+
+=item strend
+
+Pointer to the character following the physical end of the string (i.e.
+the \0).
+
+=item stringarg
+
+Pointer to the position in the string where matching should start; it might
+not be equal to C<strbeg> (for example in a later iteration of C</.../g>).
+
+=item minend
+
+Minimum length of string (measured in bytes from C<stringarg>) that must
+match; if the engine reaches the end of the match but hasn't reached this
+position in the string, it should fail.
+
+=item data
+
+Optimisation data; subject to change.
+
+=item flags
+
+Optimisation flags; subject to change.
+
+=back
=head2 intuit
Called to get/set the value of C<$`>, C<$'>, C<$&> and their named
equivalents, ${^PREMATCH}, ${^POSTMATCH} and $^{MATCH}, as well as the
-numbered capture buffers (C<$1>, C<$2>, ...).
+numbered capture groups (C<$1>, C<$2>, ...).
+
+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
+ $& RX_BUFF_IDX_FULLMATCH
+
+Note that in perl 5.17.3 and earlier, the last three constants were also
+used for the caret variants of the variables.
-The C<paren> paramater will be C<-2> for C<$`>, 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
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_get>
+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.
Example:
if ("ook" =~ /(o*)/) {
- # `paren' will be `1' and `value' will be `ee'
+ # '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 callack
+variables, to do this in another engine use the following callback
(copied from C<Perl_reg_numbered_buff_store>):
void
Perl_croak(aTHX_ PL_no_modify);
}
-Actually perl
5.10 will not I<always> croak in a statement that looks
+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
package main;
- tie my $sv => "CatptureVar";
+ tie my $sv => "CaptureVar";
$sv =~ y/a/b/;
Because C<$sv> is C<undef> when the C<y///> operator is applied to it
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:
+stored in C<< rx->offs >> this is much more efficient:
I32 s1 = rx->offs[paren].start;
I32 s2 = rx->offs[paren].end;
Which L<Tie::Hash> operation is being performed from the Perl level on
C<%+> or C<%+>, if any:
- RXf_HASH_FETCH
- RXf_HASH_STORE
- RXf_HASH_DELETE
- RXf_HASH_CLEAR
- RXf_HASH_EXISTS
- RXf_HASH_SCALAR
- RXf_HASH_FIRSTKEY
- RXf_HASH_NEXTKEY
+ 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.
- RXf_HASH_ONE /* %+ */
- RXf_HASH_ALL /* %- */
+ RXapif_ONE /* %+ */
+ RXapif_ALL /* %- */
Whether this is being called as C<re::regname>, C<re::regnames> or
-C<C<re::regnames_count>, if any. The first two will be combined with
-C<RXf_HASH_ONE> or C<RXf_HASH_ALL>.
+C<re::regnames_count>, if any. The first two will be combined with
+C<RXapif_ONE> or C<RXapif_ALL>.
- RXf_HASH_REGNAME
- RXf_HASH_REGNAMES
- RXf_HASH_REGNAMES_COUNT
+ RXapif_REGNAME
+ RXapif_REGNAMES
+ 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
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:
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:
+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:
- 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;
- }
+ REGEXP * re = SvRX(sv);
=head2 dupe
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.)
On unthreaded builds this field doesn't exist.
+=head2 op_comp
+
+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
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 */
created this object. */
/* Data about the last/current match. These are modified during matching*/
- U32 lastparen; /* last open paren matched */
- U32 lastcloseparen; /* last close paren matched */
+ 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 (@+) */
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 subcoffset; /* suboffset equiv, but in chars (for @-/@+) */
/* Information about the match that isn't often used */
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 */
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.
+the L<comp|/comp> callback. See the L<comp|/comp> documentation for
+valid flags.
=head2 C<minlen> C<minlenret>
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.
=head2 C<gofs>
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 like C<minlen>.
+used in the future for all engines for optimisations.
-=head2 C<nparens>, C<lasparen>, and C<lastcloseparen>
+=head2 C<nparens>, C<lastparen>, 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
=head2 C<swap>
-TODO: document
+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 buffer 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<$paren >= 1>.
=head2 C<precomp> C<prelen>
=head2 C<paren_names>
-This is a hash used internally to track named capture buffers and their
+This is a hash used internally to track named capture groups and their
offsets. The keys are the names of the buffers the values are dualvars,
with the IV slot holding the number of buffers with the given name and the
pv being an embedded array of I32. The values may also be contained
independently in the data array in cases where named backreferences are
used.
-=head2 C<reg_substr_data>
+=head2 C<substrs>
Holds information on the longest string that must occur at a fixed
offset from the start of the pattern, and the longest string that must
Fast-Boyer-Moore searches on the string to find out if its worth using
the regex engine at all, and if so where in the string to search.
-=head2 C<subbeg> C<sublen> C<saved_copy>
-
- #define SAVEPVN(p,n) ((p) ? savepvn(p,n) : NULL)
- if (RX_MATCH_COPIED(ret))
- ret->subbeg = SAVEPVN(ret->subbeg, ret->sublen);
- else
- ret->subbeg = NULL;
+=head2 C<subbeg> C<sublen> C<saved_copy> C<suboffset> C<subcoffset>
-C<PL_sawampersand || rx->extflags & RXf_PMf_KEEPCOPY>
+Used during the execution phase for managing search and replace patterns,
+and for providing the text for C<$&>, C<$1> etc. C<subbeg> points to a
+buffer (either the original string, or a copy in the case of
+C<RX_MATCH_COPIED(rx)>), and C<sublen> is the length of the buffer. The
+C<RX_OFFS> start and end indices index into this buffer.
-These are used during execution phase for managing search and replace
-patterns.
+In the presence of the C<REXEC_COPY_STR> flag, but with the addition of
+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
+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
+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, for example C<(?-xism:eek)>
-in the case of C<qr/eek/>.
+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 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/i; # "c"
There's no solution for this problem other than making the custom
engine understand a construct like C<(?:)>.
-The C<Perl_reg_stringify> in F<regcomp.c> does the stringification work.
-
=head2 C<seen_evals>
This stores the number of eval groups in the pattern. This is used for security
https://perl5.git.perl.org / perl5.git / blobdiff