172 lines
5.2 KiB
Scheme
172 lines
5.2 KiB
Scheme
;;; Parse Spencer-style regexps into the regexp ADT.
|
|
;;; Olin Shivers, July 1998.
|
|
|
|
;;; One export: (posix-string->regexp s)
|
|
|
|
;;; Need better error checking on {m,n} brace parsing.
|
|
|
|
(define (parse-posix-regexp-string s)
|
|
(receive (re i) (parse-posix-exp s 0)
|
|
(if (= i (string-length s)) re
|
|
(error "Illegal Posix regexp -- terminated early" s i))))
|
|
|
|
(define posix-string->regexp parse-posix-regexp-string)
|
|
|
|
;;; An complete expression is a sequence of |-separated branches.
|
|
|
|
(define (parse-posix-exp s i)
|
|
(let ((len (string-length s)))
|
|
(if (< i len)
|
|
(let lp ((i i) (branches '()))
|
|
(receive (branch i) (parse-posix-branch s i)
|
|
(let ((branches (cons branch branches)))
|
|
(if (and (< i len)
|
|
(char=? #\| (string-ref s i)))
|
|
(lp (+ i 1) branches)
|
|
(values (re-choice (reverse branches)) i)))))
|
|
(values re-trivial i))))
|
|
|
|
|
|
;;; A branch is a sequence of pieces -- stuff that goes in-between |'s.
|
|
|
|
(define (parse-posix-branch s i)
|
|
(let ((len (string-length s)))
|
|
(let lp ((i i) (pieces '()))
|
|
(if (< i len)
|
|
(receive (piece i) (parse-posix-piece s i)
|
|
(let ((pieces (cons piece pieces)))
|
|
(if (< i len)
|
|
(case (string-ref s i)
|
|
((#\) #\|) (values (re-seq (reverse pieces)) i))
|
|
(else (lp i pieces)))
|
|
(values (re-seq (reverse pieces)) i))))
|
|
|
|
(values (re-seq (reverse pieces)) i)))))
|
|
|
|
|
|
;;; A piece is an atom possibly followed by a * ? + or {...} multiplier.
|
|
;;; I.e. an element of a branch sequence.
|
|
|
|
(define (parse-posix-piece s i)
|
|
(let ((len (string-length s)))
|
|
(receive (atom i) (parse-posix-atom s i)
|
|
(if (< i len)
|
|
(case (string-ref s i)
|
|
((#\* #\+ #\?)
|
|
(receive (from to) (case (string-ref s i)
|
|
((#\*) (values 0 #f))
|
|
((#\+) (values 1 #f))
|
|
((#\?) (values 0 1)))
|
|
(values (re-repeat from to atom) (+ i 1))))
|
|
|
|
((#\{) (receive (from to i) (parse-posix-braces s (+ i 1))
|
|
(values (re-repeat from to atom) i)))
|
|
|
|
(else (values atom i)))
|
|
|
|
(values atom i)))))
|
|
|
|
|
|
;;; An atom is something that would bind to a following * operator --
|
|
;;; a letter, [...] charset, ^, $, or (...).
|
|
|
|
(define (parse-posix-atom s i)
|
|
(let ((len (string-length s)))
|
|
(if (< i (string-length s))
|
|
(let ((c (string-ref s i)))
|
|
(case c
|
|
((#\^) (values re-bos (+ i 1)))
|
|
((#\$) (values re-eos (+ i 1)))
|
|
((#\.) (values re-any (+ i 1)))
|
|
|
|
((#\[) (parse-posix-bracket s (+ i 1)))
|
|
|
|
((#\() (receive (re i) (parse-posix-exp s (+ i 1))
|
|
(if (and (< i len) (char=? #\) (string-ref s i)))
|
|
(values (re-submatch re) (+ i 1))
|
|
(error "Regexp subexpression has no terminating close parenthesis" s i))))
|
|
|
|
((#\\) (let ((i (+ i 1)))
|
|
(if (< i len)
|
|
(values (make-re-string (string (string-ref s i)))
|
|
(+ i 1))
|
|
(error "Regexps may not terminate with a backslash" s))))
|
|
|
|
((#\) #\| #\* #\+ #\? #\{) (values re-trivial i))
|
|
|
|
(else (values (make-re-string (string c)) (+ i 1)))))
|
|
|
|
(values re-trivial i))))
|
|
|
|
|
|
;;; Parse a [...] or [^...] bracket expression into a regexp.
|
|
;;; I is the index of the char following the left bracket.
|
|
|
|
(define db-cset (char-set #\. #\= #\:)) ; Not allowed after a #\[.
|
|
|
|
(define (parse-posix-bracket s i)
|
|
(let ((len (string-length s)))
|
|
(if (>= i len) (error "Missing close right bracket in regexp" s i)
|
|
|
|
(receive (negate? i0) (let ((c (string-ref s i)))
|
|
(if (char=? c #\^)
|
|
(values #t (+ i 1))
|
|
(values #f i)))
|
|
(let lp ((i i0) (cset (char-set-copy char-set:empty)))
|
|
(if (>= i len) (error "Missing close right bracket in regexp" s i)
|
|
|
|
(let ((c (string-ref s i))
|
|
(i1 (+ i 1)))
|
|
(case c
|
|
((#\[)
|
|
;; We don't handle [..] [==] [::] frobs.
|
|
(if (and (< i1 len)
|
|
(char-set-contains? db-cset (string-ref s i1)))
|
|
(error "double-bracket regexps not supported." s i)
|
|
(lp i1 (char-set-adjoin! cset #\[))))
|
|
|
|
((#\]) (if (= i i0)
|
|
(lp i1 (char-set-adjoin! cset #\]))
|
|
(let ((cset (if negate?
|
|
(char-set-complement! cset)
|
|
cset)))
|
|
(values (make-re-char-set cset) i1))))
|
|
|
|
((#\-) (if (or (= i i0) ; first char or last char
|
|
(and (< i1 len)
|
|
(char=? #\] (string-ref s i1))))
|
|
(lp i1 (char-set-adjoin! cset #\-))
|
|
(error "Illegal - in [...] regexp" s i)))
|
|
|
|
;; Regular letter -- either alone, or startpoint of a range.
|
|
(else (if (and (< (+ i1 1) len)
|
|
(char=? #\- (string-ref s i1)))
|
|
|
|
;; Range
|
|
(let* ((i-tochar (+ i1 1))
|
|
(to (char->ascii (string-ref s i-tochar))))
|
|
(do ((j (char->ascii c) (+ j 1))
|
|
(cset cset (char-set-adjoin! cset (ascii->char j))))
|
|
((> j to) (lp (+ i-tochar 1) cset))))
|
|
|
|
;; Just a letter
|
|
(lp i1 (char-set-adjoin! cset c))))))))))))
|
|
|
|
|
|
;;; Parse out a [from,to] repetition pair from a {m,n} {m} or {m,} expression.
|
|
;;; I is the index of the char following the left brace.
|
|
|
|
(define (parse-posix-braces s i)
|
|
(let ((comma (string-index s #\, i))
|
|
(rb (string-index s #\} i)))
|
|
(if rb
|
|
(if (and comma (< comma rb))
|
|
(values (string->number (substring s i comma))
|
|
(and (not (= (+ comma 1) rb))
|
|
(string->number (substring s (+ comma 1) rb)))
|
|
(+ rb 1))
|
|
(let ((m (string->number (substring s i rb))))
|
|
(values m m (+ rb 1))))
|
|
(error "Missing close brace in regexp" s i))))
|
|
|