this document are expected to understand perl's regex syntax and its
usage in detail. If you want to learn about the basics of Perl's
regular expressions, see L<perlre>. And if you want to replace the
-regex engine with your own
see see L<perlreapi>.
+regex engine with your own
, see L<perlreapi>.
=head1 OVERVIEW
additional 4-byte (32-bit) bitmap indicating which POSIX char classes
have been included.
- regnode_charclass_class U32 arg1;
- char bitmap[ANYOF_BITMAP_SIZE];
- char classflags[ANYOF_CLASSBITMAP_SIZE];
+ regnode_charclass_class U32 arg1;
+ char bitmap[ANYOF_BITMAP_SIZE];
+ char classflags[ANYOF_CLASSBITMAP_SIZE];
=back
=item *
There is the "next regop" from a given regop/regnode. This is the
-regop physically located after the the current one, as determined by
+regop physically located after the current one, as determined by
the size of the current regop. This is often useful, such as when
dumping the structure we use this order to traverse. Sometimes the code
assumes that the "next regnode" is the same as the "next regop", or in
The call graph looks like this:
- reg() # parse a top level regex, or inside of parens
- regbranch() # parse a single branch of an alternation
- regpiece() # parse a pattern followed by a quantifier
- regatom() # parse a simple pattern
- regclass() # used to handle a class
- reg() # used to handle a parenthesised subpattern
- ....
- ...
- regtail() # finish off the branch
- ...
- regtail() # finish off the branch sequence. Tie each
- # branch's tail to the tail of the sequence
- # (NEW) In Debug mode this is
- # regtail_study().
+ reg() # parse a top level regex, or inside of
+ # parens
+ regbranch() # parse a single branch of an alternation
+ regpiece() # parse a pattern followed by a quantifier
+ regatom() # parse a simple pattern
+ regclass() # used to handle a class
+ reg() # used to handle a parenthesised
+ # subpattern
+ ....
+ ...
+ regtail() # finish off the branch
+ ...
+ regtail() # finish off the branch sequence. Tie each
+ # branch's tail to the tail of the
+ # sequence
+ # (NEW) In Debug mode this is
+ # regtail_study().
A grammar form might be something like this:
atom
>)$< 34 tail~ BRANCH (28)
36 tsdy~ BRANCH (END) (31)
- ~ attach to CLOSE1 (34) offset to 3
+ ~ attach to CLOSE1 (34) offset to 3
tsdy~ EXACT <foo> (EXACT) (29)
- ~ attach to CLOSE1 (34) offset to 5
+ ~ attach to CLOSE1 (34) offset to 5
tsdy~ EXACT <bar> (EXACT) (32)
- ~ attach to CLOSE1 (34) offset to 2
+ ~ attach to CLOSE1 (34) offset to 2
>$< tail~ BRANCH (3)
~ BRANCH (9)
~ TAIL (25)
The two entry points are C<re_intuit_start()> and C<pregexec()>. These routines
have a somewhat incestuous relationship with overlap between their functions,
and C<pregexec()> may even call C<re_intuit_start()> on its own. Nevertheless
-other parts of the the perl source code may call into either, or both.
+other parts of the perl source code may call into either, or both.
Execution of the interpreter itself used to be recursive, but thanks to the
efforts of Dave Mitchell in the 5.9.x development track, that has changed: now an
internal stack is maintained on the heap and the routine is fully
iterative. This can make it tricky as the code is quite conservative
-about what state it stores, with the result that that two consecutive lines in the
+about what state it stores, with the result that two consecutive lines in the
code can actually be running in totally different contexts due to the
simulated recursion.
bytes to represent characters from the ASCII character set, and sequences
of two or more bytes for all other characters. (See L<perlunitut>
for more information about the relationship between UTF-8 and perl's
-encoding, utf8 -- the difference isn't important for this discussion.)
+encoding, utf8. The difference isn't important for this discussion.)
No matter how you look at it, Unicode support is going to be a pain in a
regex engine. Tricks that might be fine when you have 256 possible
The other structure is pointed to be the C<regexp> struct's
C<pprivate> and is in addition to C<intflags> in the same struct
considered to be the property of the regex engine which compiled the
-regular expression;
+regular expression;
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
regex engine. Since it is specific to perl it is only of curiosity
value to other engine implementations.
- typedef struct regexp_internal {
- regexp_paren_ofs *swap; /* Swap copy of *startp / *endp */
- U32 *offsets; /* offset annotations 20001228 MJD
- data about mapping the program to the
- string*/
- regnode *regstclass; /* Optional startclass as identified or constructed
- by the optimiser */
- struct reg_data *data; /* Additional miscellaneous data used by the program.
- Used to make it easier to clone and free arbitrary
- data that the regops need. Often the ARG field of
- a regop is an index into this structure */
- regnode program[1]; /* Unwarranted chumminess with compiler. */
- } regexp_internal;
+ typedef struct regexp_internal {
+ regexp_paren_ofs *swap; /* Swap copy of *startp / *endp */
+ U32 *offsets; /* offset annotations 20001228 MJD
+ * data about mapping the program to
+ * the string*/
+ regnode *regstclass; /* Optional startclass as identified or
+ * constructed by the optimiser */
+ struct reg_data *data; /* Additional miscellaneous data used
+ * by the program. Used to make it
+ * easier to clone and free arbitrary
+ * data that the regops need. Often the
+ * ARG field of a regop is an index
+ * into this structure */
+ regnode program[1]; /* Unwarranted chumminess with
+ * compiler. */
+ } regexp_internal;
=over 5
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