;;; -*- Mode: LISP; Syntax: COMMON-LISP; Package: CL-PPCRE; Base: 10 -*-
;;; $Header$
;;; Here the parse tree is converted into its internal representation
;;; using REGEX objects. At the same time some optimizations are
;;; already applied.
;;; Copyright (c) 2002-2006, Dr. Edmund Weitz. All rights reserved.
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;; * Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;; * Redistributions in binary form must reproduce the above
;;; copyright notice, this list of conditions and the following
;;; disclaimer in the documentation and/or other materials
;;; provided with the distribution.
;;; THIS SOFTWARE IS PROVIDED BY THE AUTHOR 'AS IS' AND ANY EXPRESSED
;;; OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
;;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
;;; ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
;;; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
;;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
;;; GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
;;; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
;;; WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
(in-package #:cl-ppcre)
;;; The flags that represent the "ism" modifiers are always kept
;;; together in a three-element list. We use the following macros to
;;; access individual elements.
(defmacro case-insensitive-mode-p (flags)
"Accessor macro to extract the first flag out of a three-element flag list."
`(first ,flags))
(defmacro multi-line-mode-p (flags)
"Accessor macro to extract the second flag out of a three-element flag list."
`(second ,flags))
(defmacro single-line-mode-p (flags)
"Accessor macro to extract the third flag out of a three-element flag list."
`(third ,flags))
(defun set-flag (token)
(declare #.*standard-optimize-settings*)
(declare (special flags))
"Reads a flag token and sets or unsets the corresponding entry in
the special FLAGS list."
(case token
((:case-insensitive-p)
(setf (case-insensitive-mode-p flags) t))
((:case-sensitive-p)
(setf (case-insensitive-mode-p flags) nil))
((:multi-line-mode-p)
(setf (multi-line-mode-p flags) t))
((:not-multi-line-mode-p)
(setf (multi-line-mode-p flags) nil))
((:single-line-mode-p)
(setf (single-line-mode-p flags) t))
((:not-single-line-mode-p)
(setf (single-line-mode-p flags) nil))
(otherwise
(signal-ppcre-syntax-error "Unknown flag token ~A" token))))
(defun add-range-to-hash (hash from to)
(declare #.*standard-optimize-settings*)
(declare (special flags))
"Adds all characters from character FROM to character TO (inclusive)
to the char class hash HASH. Does the right thing with respect to
case-(in)sensitivity as specified by the special variable FLAGS."
(let ((from-code (char-code from))
(to-code (char-code to)))
(when (> from-code to-code)
(signal-ppcre-syntax-error "Invalid range from ~A to ~A in char-class"
from to))
(cond ((case-insensitive-mode-p flags)
(loop for code from from-code to to-code
for chr = (code-char code)
do (setf (gethash (char-upcase chr) hash) t
(gethash (char-downcase chr) hash) t)))
(t
(loop for code from from-code to to-code
do (setf (gethash (code-char code) hash) t))))
hash))
(defun convert-char-class-to-hash (list)
(declare #.*standard-optimize-settings*)
"Combines all items in LIST into one char class hash and returns it.
Items can be single characters, character ranges like \(:RANGE #\\A
#\\E), or special character classes like :DIGIT-CLASS. Does the right
thing with respect to case-\(in)sensitivity as specified by the
special variable FLAGS."
(loop with hash = (make-hash-table :size (ceiling (expt *regex-char-code-limit* (/ 1 4)))
:rehash-size (float (expt *regex-char-code-limit* (/ 1 4)))
:rehash-threshold #-genera 1.0 #+genera 0.99)
for item in list
if (characterp item)
;; treat a single character C like a range (:RANGE C C)
do (add-range-to-hash hash item item)
else if (symbolp item)
;; special character classes
do (setq hash
(case item
((:digit-class)
(merge-hash hash +digit-hash+))
((:non-digit-class)
(merge-inverted-hash hash +digit-hash+))
((:whitespace-char-class)
(merge-hash hash +whitespace-char-hash+))
((:non-whitespace-char-class)
(merge-inverted-hash hash +whitespace-char-hash+))
((:word-char-class)
(merge-hash hash +word-char-hash+))
((:non-word-char-class)
(merge-inverted-hash hash +word-char-hash+))
(otherwise
(signal-ppcre-syntax-error
"Unknown symbol ~A in character class"
item))))
else if (and (consp item)
(eq (car item) :range))
;; proper ranges
do (add-range-to-hash hash
(second item)
(third item))
else do (signal-ppcre-syntax-error "Unknown item ~A in char-class list"
item)
finally (return hash)))
(defun maybe-split-repetition (regex
greedyp
minimum
maximum
min-len
length
reg-seen)
(declare #.*standard-optimize-settings*)
(declare (type fixnum minimum)
(type (or fixnum null) maximum))
"Splits a REPETITION object into a constant and a varying part if
applicable, i.e. something like
a{3,} -> a{3}a*
The arguments to this function correspond to the REPETITION slots of
the same name."
;; note the usage of COPY-REGEX here; we can't use the same REGEX
;; object in both REPETITIONS because they will have different
;; offsets
(when maximum
(when (zerop maximum)
;; trivial case: don't repeat at all
(return-from maybe-split-repetition
(make-instance 'void)))
(when (= 1 minimum maximum)
;; another trivial case: "repeat" exactly once
(return-from maybe-split-repetition
regex)))
;; first set up the constant part of the repetition
;; maybe that's all we need
(let ((constant-repetition (if (plusp minimum)
(make-instance 'repetition
:regex (copy-regex regex)
:greedyp greedyp
:minimum minimum
:maximum minimum
:min-len min-len
:len length
:contains-register-p reg-seen)
;; don't create garbage if minimum is 0
nil)))
(when (and maximum
(= maximum minimum))
(return-from maybe-split-repetition
;; no varying part needed because min = max
constant-repetition))
;; now construct the varying part
(let ((varying-repetition
(make-instance 'repetition
:regex regex
:greedyp greedyp
:minimum 0
:maximum (if maximum (- maximum minimum) nil)
:min-len min-len
:len length
:contains-register-p reg-seen)))
(cond ((zerop minimum)
;; min = 0, no constant part needed
varying-repetition)
((= 1 minimum)
;; min = 1, constant part needs no REPETITION wrapped around
(make-instance 'seq
:elements (list (copy-regex regex)
varying-repetition)))
(t
;; general case
(make-instance 'seq
:elements (list constant-repetition
varying-repetition)))))))
;; During the conversion of the parse tree we keep track of the start
;; of the parse tree in the special variable STARTS-WITH which'll
;; either hold a STR object or an EVERYTHING object. The latter is the
;; case if the regex starts with ".*" which implicitely anchors the
;; regex at the start (perhaps modulo #\Newline).
(defun maybe-accumulate (str)
(declare #.*standard-optimize-settings*)
(declare (special accumulate-start-p starts-with))
(declare (ftype (function (t) fixnum) len))
"Accumulate STR into the special variable STARTS-WITH if
ACCUMULATE-START-P (also special) is true and STARTS-WITH is either
NIL or a STR object of the same case mode. Always returns NIL."
(when accumulate-start-p
(etypecase starts-with
(str
;; STARTS-WITH already holds a STR, so we check if we can
;; concatenate
(cond ((eq (case-insensitive-p starts-with)
(case-insensitive-p str))
;; we modify STARTS-WITH in place
(setf (len starts-with)
(+ (len starts-with) (len str)))
;; note that we use SLOT-VALUE because the accessor
;; STR has a declared FTYPE which doesn't fit here
(adjust-array (slot-value starts-with 'str)
(len starts-with)
:fill-pointer t)
(setf (subseq (slot-value starts-with 'str)
(- (len starts-with) (len str)))
(str str)
;; STR objects that are parts of STARTS-WITH
;; always have their SKIP slot set to true
;; because the SCAN function will take care of
;; them, i.e. the matcher can ignore them
(skip str) t))
(t (setq accumulate-start-p nil))))
(null
;; STARTS-WITH is still empty, so we create a new STR object
(setf starts-with
(make-instance 'str
:str ""
:case-insensitive-p (case-insensitive-p str))
;; INITIALIZE-INSTANCE will coerce the STR to a simple
;; string, so we have to fill it afterwards
(slot-value starts-with 'str)
(make-array (len str)
:initial-contents (str str)
:element-type 'character
:fill-pointer t
:adjustable t)
(len starts-with)
(len str)
;; see remark about SKIP above
(skip str) t))
(everything
;; STARTS-WITH already holds an EVERYTHING object - we can't
;; concatenate
(setq accumulate-start-p nil))))
nil)
(defun convert-aux (parse-tree)
(declare #.*standard-optimize-settings*)
(declare (special flags reg-num accumulate-start-p starts-with max-back-ref))
"Converts the parse tree PARSE-TREE into a REGEX object and returns it.
Will also
- split and optimize repetitions,
- accumulate strings or EVERYTHING objects into the special variable
STARTS-WITH,
- keep track of all registers seen in the special variable REG-NUM,
- keep track of the highest backreference seen in the special
variable MAX-BACK-REF,
- maintain and adher to the currently applicable modifiers in the special
variable FLAGS, and
- maybe even wash your car..."
(cond ((consp parse-tree)
(case (first parse-tree)
;; (:SEQUENCE {<regex>}*)
((:sequence)
(cond ((cddr parse-tree)
;; this is essentially like
;; (MAPCAR 'CONVERT-AUX (REST PARSE-TREE))
;; but we don't cons a new list
(loop for parse-tree-rest on (rest parse-tree)
while parse-tree-rest
do (setf (car parse-tree-rest)
(convert-aux (car parse-tree-rest))))
(make-instance 'seq
:elements (rest parse-tree)))
(t (convert-aux (second parse-tree)))))
;; (:GROUP {<regex>}*)
;; this is a syntactical construct equivalent to :SEQUENCE
;; intended to keep the effect of modifiers local
((:group)
;; make a local copy of FLAGS and shadow the global
;; value while we descend into the enclosed regexes
(let ((flags (copy-list flags)))
(declare (special flags))
(cond ((cddr parse-tree)
(loop for parse-tree-rest on (rest parse-tree)
while parse-tree-rest
do (setf (car parse-tree-rest)
(convert-aux (car parse-tree-rest))))
(make-instance 'seq
:elements (rest parse-tree)))
(t (convert-aux (second parse-tree))))))
;; (:ALTERNATION {<regex>}*)
((:alternation)
;; we must stop accumulating objects into STARTS-WITH
;; once we reach an alternation
(setq accumulate-start-p nil)
(loop for parse-tree-rest on (rest parse-tree)
while parse-tree-rest
do (setf (car parse-tree-rest)
(convert-aux (car parse-tree-rest))))
(make-instance 'alternation
:choices (rest parse-tree)))
;; (:BRANCH <test> <regex>)
;; <test> must be look-ahead, look-behind or number;
;; if <regex> is an alternation it must have one or two
;; choices
((:branch)
(setq accumulate-start-p nil)
(let* ((test-candidate (second parse-tree))
(test (cond ((numberp test-candidate)
(when (zerop (the fixnum test-candidate))
(signal-ppcre-syntax-error
"Register 0 doesn't exist: ~S"
parse-tree))
(1- (the fixnum test-candidate)))
(t (convert-aux test-candidate))))
(alternations (convert-aux (third parse-tree))))
(when (and (not (numberp test))
(not (typep test 'lookahead))
(not (typep test 'lookbehind)))
(signal-ppcre-syntax-error
"Branch test must be look-ahead, look-behind or number: ~S"
parse-tree))
(typecase alternations
(alternation
(case (length (choices alternations))
((0)
(signal-ppcre-syntax-error "No choices in branch: ~S"
parse-tree))
((1)
(make-instance 'branch
:test test
:then-regex (first
(choices alternations))))
((2)
(make-instance 'branch
:test test
:then-regex (first
(choices alternations))
:else-regex (second
(choices alternations))))
(otherwise
(signal-ppcre-syntax-error
"Too much choices in branch: ~S"
parse-tree))))
(t
(make-instance 'branch
:test test
:then-regex alternations)))))
;; (:POSITIVE-LOOKAHEAD|:NEGATIVE-LOOKAHEAD <regex>)
((:positive-lookahead :negative-lookahead)
;; keep the effect of modifiers local to the enclosed
;; regex and stop accumulating into STARTS-WITH
(setq accumulate-start-p nil)
(let ((flags (copy-list flags)))
(declare (special flags))
(make-instance 'lookahead
:regex (convert-aux (second parse-tree))
:positivep (eq (first parse-tree)
:positive-lookahead))))
;; (:POSITIVE-LOOKBEHIND|:NEGATIVE-LOOKBEHIND <regex>)
((:positive-lookbehind :negative-lookbehind)
;; keep the effect of modifiers local to the enclosed
;; regex and stop accumulating into STARTS-WITH
(setq accumulate-start-p nil)
(let* ((flags (copy-list flags))
(regex (convert-aux (second parse-tree)))
(len (regex-length regex)))
(declare (special flags))
;; lookbehind assertions must be of fixed length
(unless len
(signal-ppcre-syntax-error
"Variable length look-behind not implemented (yet): ~S"
parse-tree))
(make-instance 'lookbehind
:regex regex
:positivep (eq (first parse-tree)
:positive-lookbehind)
:len len)))
;; (:GREEDY-REPETITION|:NON-GREEDY-REPETITION <min> <max> <regex>)
((:greedy-repetition :non-greedy-repetition)
;; remember the value of ACCUMULATE-START-P upon entering
(let ((local-accumulate-start-p accumulate-start-p))
(let ((minimum (second parse-tree))
(maximum (third parse-tree)))
(declare (type fixnum minimum))
(declare (type (or null fixnum) maximum))
(unless (and maximum
(= 1 minimum maximum))
;; set ACCUMULATE-START-P to NIL for the rest of
;; the conversion because we can't continue to
;; accumulate inside as well as after a proper
;; repetition
(setq accumulate-start-p nil))
(let* (reg-seen
(regex (convert-aux (fourth parse-tree)))
(min-len (regex-min-length regex))
(greedyp (eq (first parse-tree) :greedy-repetition))
(length (regex-length regex)))
;; note that this declaration already applies to
;; the call to CONVERT-AUX above
(declare (special reg-seen))
(when (and local-accumulate-start-p
(not starts-with)
(zerop minimum)
(not maximum))
;; if this repetition is (equivalent to) ".*"
;; and if we're at the start of the regex we
;; remember it for ADVANCE-FN (see the SCAN
;; function)
(setq starts-with (everythingp regex)))
(if (or (not reg-seen)
(not greedyp)
(not length)
(zerop length)
(and maximum (= minimum maximum)))
;; the repetition doesn't enclose a register, or
;; it's not greedy, or we can't determine it's
;; (inner) length, or the length is zero, or the
;; number of repetitions is fixed; in all of
;; these cases we don't bother to optimize
(maybe-split-repetition regex
greedyp
minimum
maximum
min-len
length
reg-seen)
;; otherwise we make a transformation that looks
;; roughly like one of
;; <regex>* -> (?:<regex'>*<regex>)?
;; <regex>+ -> <regex'>*<regex>
;; where the trick is that as much as possible
;; registers from <regex> are removed in
;; <regex'>
(let* (reg-seen ; new instance for REMOVE-REGISTERS
(remove-registers-p t)
(inner-regex (remove-registers regex))
(inner-repetition
;; this is the "<regex'>" part
(maybe-split-repetition inner-regex
;; always greedy
t
;; reduce minimum by 1
;; unless it's already 0
(if (zerop minimum)
0
(1- minimum))
;; reduce maximum by 1
;; unless it's NIL
(and maximum
(1- maximum))
min-len
length
reg-seen))
(inner-seq
;; this is the "<regex'>*<regex>" part
(make-instance 'seq
:elements (list inner-repetition
regex))))
;; note that this declaration already applies
;; to the call to REMOVE-REGISTERS above
(declare (special remove-registers-p reg-seen))
;; wrap INNER-SEQ with a greedy
;; {0,1}-repetition (i.e. "?") if necessary
(if (plusp minimum)
inner-seq
(maybe-split-repetition inner-seq
t
0
1
min-len
nil
t))))))))
;; (:REGISTER <regex>)
((:register)
;; keep the effect of modifiers local to the enclosed
;; regex; also, assign the current value of REG-NUM to
;; the corresponding slot of the REGISTER object and
;; increase this counter afterwards
(let ((flags (copy-list flags))
(stored-reg-num reg-num))
(declare (special flags reg-seen))
(setq reg-seen t)
(incf (the fixnum reg-num))
(make-instance 'register
:regex (convert-aux (second parse-tree))
:num stored-reg-num)))
;; (:FILTER <function> &optional <length>)
((:filter)
;; stop accumulating into STARTS-WITH
(setq accumulate-start-p nil)
(make-instance 'filter
:fn (second parse-tree)
:len (third parse-tree)))
;; (:STANDALONE <regex>)
((:standalone)
;; stop accumulating into STARTS-WITH
(setq accumulate-start-p nil)
;; keep the effect of modifiers local to the enclosed
;; regex
(let ((flags (copy-list flags)))
(declare (special flags))
(make-instance 'standalone
:regex (convert-aux (second parse-tree)))))
;; (:BACK-REFERENCE <number>)
((:back-reference)
(let ((backref-number (second parse-tree)))
(declare (type fixnum backref-number))
(when (or (not (typep backref-number 'fixnum))
(<= backref-number 0))
(signal-ppcre-syntax-error
"Illegal back-reference: ~S"
parse-tree))
;; stop accumulating into STARTS-WITH and increase
;; MAX-BACK-REF if necessary
(setq accumulate-start-p nil
max-back-ref (max (the fixnum max-back-ref)
backref-number))
(make-instance 'back-reference
;; we start counting from 0 internally
:num (1- backref-number)
:case-insensitive-p (case-insensitive-mode-p
flags))))
;; (:REGEX <string>)
((:regex)
(let ((regex (second parse-tree)))
(convert-aux (parse-string regex))))
;; (:CHAR-CLASS|:INVERTED-CHAR-CLASS {<item>}*)
;; where item is one of
;; - a character
;; - a character range: (:RANGE <char1> <char2>)
;; - a special char class symbol like :DIGIT-CHAR-CLASS
((:char-class :inverted-char-class)
;; first create the hash-table and some auxiliary values
(let* (hash
hash-keys
(count most-positive-fixnum)
(item-list (rest parse-tree))
(invertedp (eq (first parse-tree) :inverted-char-class))
word-char-class-p)
(cond ((every (lambda (item) (eq item :word-char-class))
item-list)
;; treat "[\\w]" like "\\w"
(setq word-char-class-p t))
((every (lambda (item) (eq item :non-word-char-class))
item-list)
;; treat "[\\W]" like "\\W"
(setq word-char-class-p t)
(setq invertedp (not invertedp)))
(t
(setq hash (convert-char-class-to-hash item-list)
count (hash-table-count hash))
(when (<= count 2)
;; collect the hash-table keys into a list if
;; COUNT is smaller than 3
(setq hash-keys
(loop for chr being the hash-keys of hash
collect chr)))))
(cond ((and (not invertedp)
(= count 1))
;; convert one-element hash table into a STR
;; object and try to accumulate into
;; STARTS-WITH
(let ((str (make-instance 'str
:str (string
(first hash-keys))
:case-insensitive-p nil)))
(maybe-accumulate str)
str))
((and (not invertedp)
(= count 2)
(char-equal (first hash-keys) (second hash-keys)))
;; convert two-element hash table into a
;; case-insensitive STR object and try to
;; accumulate into STARTS-WITH if the two
;; characters are CHAR-EQUAL
(let ((str (make-instance 'str
:str (string
(first hash-keys))
:case-insensitive-p t)))
(maybe-accumulate str)
str))
(t
;; the general case; stop accumulating into STARTS-WITH
(setq accumulate-start-p nil)
(make-instance 'char-class
:hash hash
:case-insensitive-p
(case-insensitive-mode-p flags)
:invertedp invertedp
:word-char-class-p word-char-class-p)))))
;; (:FLAGS {<flag>}*)
;; where flag is a modifier symbol like :CASE-INSENSITIVE-P
((:flags)
;; set/unset the flags corresponding to the symbols
;; following :FLAGS
(mapc #'set-flag (rest parse-tree))
;; we're only interested in the side effect of
;; setting/unsetting the flags and turn this syntactical
;; construct into a VOID object which'll be optimized
;; away when creating the matcher
(make-instance 'void))
(otherwise
(signal-ppcre-syntax-error
"Unknown token ~A in parse-tree"
(first parse-tree)))))
((or (characterp parse-tree) (stringp parse-tree))
;; turn characters or strings into STR objects and try to
;; accumulate into STARTS-WITH
(let ((str (make-instance 'str
:str (string parse-tree)
:case-insensitive-p
(case-insensitive-mode-p flags))))
(maybe-accumulate str)
str))
(t
;; and now for the tokens which are symbols
(case parse-tree
((:void)
(make-instance 'void))
((:word-boundary)
(make-instance 'word-boundary :negatedp nil))
((:non-word-boundary)
(make-instance 'word-boundary :negatedp t))
;; the special character classes
((:digit-class
:non-digit-class
:word-char-class
:non-word-char-class
:whitespace-char-class
:non-whitespace-char-class)
;; stop accumulating into STARTS-WITH
(setq accumulate-start-p nil)
(make-instance 'char-class
;; use the constants defined in util.lisp
:hash (case parse-tree
((:digit-class
:non-digit-class)
+digit-hash+)
((:word-char-class
:non-word-char-class)
nil)
((:whitespace-char-class
:non-whitespace-char-class)
+whitespace-char-hash+))
;; this value doesn't really matter but
;; NIL should result in slightly faster
;; matchers
:case-insensitive-p nil
:invertedp (member parse-tree
'(:non-digit-class
:non-word-char-class
:non-whitespace-char-class)
:test #'eq)
:word-char-class-p (member parse-tree
'(:word-char-class
:non-word-char-class)
:test #'eq)))
((:start-anchor ; Perl's "^"
:end-anchor ; Perl's "$"
:modeless-end-anchor-no-newline
; Perl's "\z"
:modeless-start-anchor ; Perl's "\A"
:modeless-end-anchor) ; Perl's "\Z"
(make-instance 'anchor
:startp (member parse-tree
'(:start-anchor
:modeless-start-anchor)
:test #'eq)
;; set this value according to the
;; current settings of FLAGS (unless it's
;; a modeless anchor)
:multi-line-p
(and (multi-line-mode-p flags)
(not (member parse-tree
'(:modeless-start-anchor
:modeless-end-anchor
:modeless-end-anchor-no-newline)
:test #'eq)))
:no-newline-p
(eq parse-tree
:modeless-end-anchor-no-newline)))
((:everything)
;; stop accumulating into STARTS-WITHS
(setq accumulate-start-p nil)
(make-instance 'everything
:single-line-p (single-line-mode-p flags)))
;; special tokens corresponding to Perl's "ism" modifiers
((:case-insensitive-p
:case-sensitive-p
:multi-line-mode-p
:not-multi-line-mode-p
:single-line-mode-p
:not-single-line-mode-p)
;; we're only interested in the side effect of
;; setting/unsetting the flags and turn these tokens
;; into VOID objects which'll be optimized away when
;; creating the matcher
(set-flag parse-tree)
(make-instance 'void))
(otherwise
(let ((translation (and (symbolp parse-tree)
(parse-tree-synonym parse-tree))))
(if translation
(convert-aux (copy-tree translation))
(signal-ppcre-syntax-error "Unknown token ~A in parse-tree"
parse-tree))))))))
(defun convert (parse-tree)
(declare #.*standard-optimize-settings*)
"Converts the parse tree PARSE-TREE into an equivalent REGEX object
and returns three values: the REGEX object, the number of registers
seen and an object the regex starts with which is either a STR object
or an EVERYTHING object (if the regex starts with something like
\".*\") or NIL."
;; this function basically just initializes the special variables
;; and then calls CONVERT-AUX to do all the work
(let* ((flags (list nil nil nil))
(reg-num 0)
(accumulate-start-p t)
starts-with
(max-back-ref 0)
(converted-parse-tree (convert-aux parse-tree)))
(declare (special flags reg-num accumulate-start-p starts-with max-back-ref))
;; make sure we don't reference registers which aren't there
(when (> (the fixnum max-back-ref)
(the fixnum reg-num))
(signal-ppcre-syntax-error
"Backreference to register ~A which has not been defined"
max-back-ref))
(when (typep starts-with 'str)
(setf (slot-value starts-with 'str)
(coerce (slot-value starts-with 'str) 'simple-string)))
(values converted-parse-tree reg-num starts-with)))