scsh-0.5/scsh/re.scm

255 lines
7.7 KiB
Scheme

;;; Regular expression matching for scsh
;;; Copyright (c) 1994 by Olin Shivers.
(foreign-source
"/* Make sure foreign-function stubs interface to the C funs correctly: */"
"#include \"re1.h\""
"" ""
)
;;; Match data for regexp matches.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define-record regexp-match
string ; The string against which we matched.
start ; 10 elt vec
end) ; 10 elt vec
(define (match:start match . maybe-index)
(vector-ref (regexp-match:start match)
(:optional maybe-index 0)))
(define (match:end match . maybe-index)
(vector-ref (regexp-match:end match)
(:optional maybe-index 0)))
(define (match:substring match . maybe-index)
(let* ((i (:optional maybe-index 0))
(start (vector-ref (regexp-match:start match) i)))
(and start (substring (regexp-match:string match)
start
(vector-ref (regexp-match:end match) i)))))
;;; Compiling regexps
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define-record %regexp
string ; The string form of the regexp.
bytes ; The compiled representation, stuffed into a Scheme string.
((disclose self) (list "Regexp" (%regexp:string self))))
(define regexp? %regexp?)
(define (make-regexp pattern)
(receive (err len) (%regexp-compiled-length pattern)
(if err (error err make-regexp pattern)
(let ((buf (make-string len)))
(%regexp-compile pattern buf)
(make-%regexp pattern buf)))))
(define-foreign %regexp-compiled-length (re_byte_len (string pattern))
static-string ; Error msg or #f
integer) ; number of bytes needed to compile REGEXP.
(define-foreign %regexp-compile (re_compile (string pattern)
(string-desc bytes))
static-string) ; Error msg or #f
(define (->regexp x)
(cond ((string? x) (make-regexp x))
((regexp? x) x)
(else (error "Not a regexp or string." x))))
;;; Executing compiled regexps
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (regexp-exec regexp str . maybe-start)
(let ((start (:optional maybe-start 0))
(start-vec (make-vector 10))
(end-vec (make-vector 10)))
(receive (err match?)
(%regexp-exec (%regexp:bytes regexp) str start start-vec end-vec)
(if err (error err regexp-exec regexp str start)
(and match?
(make-regexp-match str start-vec end-vec))))))
(define-foreign %regexp-exec (re_exec (string-desc compiled-regexp)
(string s)
(integer start)
(vector-desc start-vec)
(vector-desc end-vec))
static-string ; Error msg or #f
bool) ; Matched?
;;; Compile&match regexps in one go
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; I could do this with the separate compile and execute procedures,
;;; but I go straight to C just for fun.
(define (string-match pattern string . maybe-start)
(let ((start (:optional maybe-start 0))
(start-vec (make-vector 10))
(end-vec (make-vector 10)))
(receive (err match?) (%string-match pattern string start
start-vec end-vec)
(if err (error err string-match pattern string start)
(and match? (make-regexp-match string start-vec end-vec))))))
(define-foreign %string-match (re_match (string pattern)
(string s)
(integer start)
(vector-desc start-vec)
(vector-desc end-vec))
static-string ; Error string or #f if all is ok.
bool) ; match?
;;; Substitutions
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (regexp-substitute port match . items)
(let* ((str (regexp-match:string match))
(sv (regexp-match:start match))
(ev (regexp-match:end match))
(range (lambda (item) ; Return start & end of
(cond ((integer? item) ; ITEM's range in STR.
(values (vector-ref sv item)
(vector-ref ev item)))
((eq? 'pre item) (values 0 (vector-ref sv 0)))
((eq? 'post item) (values (vector-ref ev 0)
(string-length str)))
(else (error "Illegal substitution item."
item
regexp-substitute))))))
(if port
;; Output port case.
(for-each (lambda (item)
(if (string? item) (write-string item port)
(receive (si ei) (range item)
(write-string str port si ei))))
items)
;; Here's the string case. Make two passes -- one to
;; compute the length of the target string, one to fill it in.
(let* ((len (reduce (lambda (i item)
(+ i (if (string? item) (string-length item)
(receive (si ei) (range item) (- ei si)))))
0 items))
(ans (make-string len)))
(reduce (lambda (index item)
(cond ((string? item)
(string-replace! ans index item)
(+ index (string-length item)))
(else (receive (si ei) (range item)
(substring-replace! ans index str si ei)
(+ index (- ei si))))))
0 items)
ans))))
(define (regexp-substitute/global port re str . items)
(let ((re (->regexp re))
(range (lambda (start sv ev item) ; Return start & end of
(cond ((integer? item) ; ITEM's range in STR.
(values (vector-ref sv item)
(vector-ref ev item)))
((eq? 'pre item) (values start (vector-ref sv 0)))
(else (error "Illegal substitution item."
item
regexp-substitute/global)))))
(num-posts (reduce (lambda (count item)
(+ count (if (eq? item 'post) 1 0)))
0 items)))
(if (and port (< num-posts 2))
;; Output port case, with zero or one POST items.
(let recur ((start 0))
(let ((match (regexp-exec re str start)))
(if match
(let* ((sv (regexp-match:start match))
(ev (regexp-match:end match)))
(for-each (lambda (item)
(cond ((string? item) (write-string item port))
((procedure? item) (write-string (item match) port))
((eq? 'post item) (recur (vector-ref ev 0)))
(else (receive (si ei)
(range start sv ev item)
(write-string str port si ei)))))
items))
(write-string str port start)))) ; No match.
(let* ((pieces (let recur ((start 0))
(let ((match (regexp-exec re str start))
(cached-post #f))
(if match
(let* ((sv (regexp-match:start match))
(ev (regexp-match:end match)))
(reduce (lambda (pieces item)
(cond ((string? item)
(cons item pieces))
((procedure? item)
(cons (item match) pieces))
((eq? 'post item)
(if (not cached-post)
(set! cached-post
(recur (vector-ref ev 0))))
(append cached-post pieces))
(else (receive (si ei)
(range start sv ev item)
(cons (substring str si ei)
pieces)))))
'() items))
;; No match. Return str[start,end].
(list (if (zero? start) str
(substring str start (string-length str))))))))
(pieces (reverse pieces)))
(if port (for-each (lambda (p) (write-string p port)) pieces)
(apply string-append pieces))))))
;;; Miscellaneous
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Convert a string into a regex pattern that matches that string exactly --
;;; in other words, quote the special chars with backslashes.
(define (regexp-quote string)
(let lp ((i (- (string-length string) 1))
(result '()))
(if (< i 0) (list->string result)
(lp (- i 1)
(let* ((c (string-ref string i))
(result (cons c result)))
(if (memv c '(#\[ #\] #\. #\* #\? #\( #\) #\| #\\ #\$ #\^ #\+))
(cons #\\ result)
result))))))
;;; Count the number of possible sub-matches in a regexp
;;; (i.e., the number of left parens).
(define (regexp-num-submatches s)
(let* ((len (string-length s))
(len-1 (- len 1)))
(let lp ((i 0) (nsm 0))
(if (= i len) nsm
(case (string-ref s i)
((#\\) (if (< i len-1) (lp (+ i 2) nsm) nsm))
((#\() (lp (+ i 1) (+ nsm 1)))
(else (lp (+ i 1) nsm)))))))