thin-provisioning-tools/functional-tests/regex.scm

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(library
(regex)
(export regex)
(import (chezscheme)
(fmt fmt)
(loops)
(prefix (parser-combinators) p:)
(srfi s8 receive)
(matchable)
(utils))
;; Simple regex library, because it's friday and I'm bored.
;; Playing with the ideas in: https://swtch.com/~rsc/regexp/regexp2.html
;; which reminded me of reading through the source code to Sam in '93.
;; Rather than parsing a string we'll use expressions.
;; (lit <string>)
;; (seq rx1 rx2)
;; (alt rx1 rx2)
;; (opt rx)
;; (star rx)
;; (plus rx)
;;
;; The expressions get compiled into a vector of vm instructions.
;; (char pred) ; where fn :: char -> bool
;; (match)
;; (jmp x)
;; (split x y)
(define (append-instr code . i) (append code i))
(define (label-instr l) `(label ,l))
(define (jmp-instr l) `(jmp ,l))
(define (char-instr fn) `(char ,fn))
(define (split-instr l1 l2) `(split ,l1 ,l2))
(define (match-instr) '(match))
(define (match-instr? instr) (equal? '(match) instr))
(define (label-code label code)
(cons (label-instr label) code))
;; Compiles to a list of labelled instructions that can later be flattened
;; into a linear sequence.
(define (lit str)
(map (lambda (c1)
(char-instr
(lambda (c2)
(char=? c1 c2))))
(string->list str)))
(define (seq rx1 rx2)
(append rx1 rx2))
(define (alt rx1 rx2)
(let ((label1 (gensym))
(label2 (gensym))
(tail (gensym)))
(let ((c1 (label-code label1
(append-instr rx1 (jmp-instr tail))))
(c2 (label-code label2 rx2)))
(cons (split-instr label1 label2)
(append-instr (append c1 c2) (label-instr tail))))))
(define (opt rx)
(let ((head (gensym))
(tail (gensym)))
(cons (split-instr head tail)
(label-code head
(append-instr rx (label-instr tail))))))
(define (star rx)
(let ((head (gensym))
(body (gensym))
(tail (gensym)))
(label-code head
(cons (split-instr body tail)
(label-code body
(append-instr rx
(jmp-instr head)
(label-instr tail)))))))
(define (plus rx)
(let ((head (gensym))
(tail (gensym)))
(label-code head
(append-instr rx
(split-instr head tail)
(label-instr tail)))))
(define (label-locations code)
(let ((locs (make-eq-hashtable)))
(let loop ((pc 0)
(code code))
(if (null? code)
locs
(match (car code)
(('label l)
(begin
(hashtable-set! locs l pc)
(loop pc (cdr code))))
(instr
(loop (+ 1 pc) (cdr code))))))))
(define (remove-labels code locs)
(let loop ((pc 0)
(code code)
(acc '()))
(if (null? code)
(reverse acc)
(match (car code)
(('label l)
(loop pc (cdr code) acc))
(('jmp l)
(loop (+ 1 pc) (cdr code)
(cons `(jmp ,(hashtable-ref locs l #f)) acc)))
(('split l1 l2)
(loop (+ 1 pc) (cdr code)
(cons `(split ,(hashtable-ref locs l1 #f)
,(hashtable-ref locs l2 #f))
acc)))
(instr (loop (+ 1 pc) (cdr code) (cons instr acc)))))))
(define (optimise-jumps! code)
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(define (single-pass)
(let ((changed #f))
(upto (n (vector-length code))
(match (vector-ref code n)
(('jmp l)
(when (match-instr? (vector-ref code l))
(set! changed #t)
(vector-set! code n (match-instr))))
(('split l1 l2)
(when (or (match-instr? (vector-ref code l1))
(match-instr? (vector-ref code l2)))
(set! changed #t)
(vector-set! code n (match-instr))))
(_ _)))
changed))
(let loop ()
(when (single-pass)
(loop)))
code)
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(define (compile-to-symbols rx)
(let ((rx (append-instr rx (match-instr))))
(optimise-jumps!
(list->vector
(remove-labels rx (label-locations rx))))))
;; A 'thread' consists of an index into the instructions. A 'yarn holds the
;; current threads. Note there cannot be more threads than instructions, so
;; a yarn is represented as a vector the same length as the instructions.
;; Threads are run in lock step, all taking the same input.
(define-record-type yarn
(fields (mutable size)
(mutable stack)
(mutable seen)))
(define (mk-yarn count)
(make-yarn 0 (make-vector count) (make-vector count #f)))
(define (clear-yarn! y)
(yarn-size-set! y 0)
(vector-fill! (yarn-seen y) #f))
(define (add-thread! y i)
(unless (vector-ref (yarn-seen y) i)
(vector-set! (yarn-seen y) i #t)
(vector-set! (yarn-stack y) (yarn-size y) i)
(yarn-size-set! y (+ 1 (yarn-size y)))))
(define (pop-thread! y)
(if (zero? (yarn-size y))
#f
(begin
(yarn-size-set! y (- (yarn-size y) 1))
(vector-ref (yarn-stack y) (yarn-size y)))))
(define (no-threads? y)
(zero? (yarn-size y)))
;; FIXME: hack
(define end-of-string #\x0)
(define (compile-rx rx)
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(let* ((sym-code (compile-to-symbols rx))
(code-len (vector-length sym-code))
(threads (mk-yarn code-len))
(next-threads (mk-yarn code-len))
(code #f))
(define (compile-instr instr)
(match instr
(('match)
(lambda (in-c pc) 'match))
(('char fn)
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(lambda (in-c pc)
;; use eq? because in-c isn't always a char
(when (fn in-c)
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(add-thread! next-threads (+ 1 pc)))))
(('jmp l)
(lambda (in-c pc)
(add-thread! threads l)))
(('split l1 l2)
(lambda (in-c pc)
(add-thread! threads l1)
(add-thread! threads l2)))))
(define (step in-c)
(let loop ((pc (pop-thread! threads)))
(and pc
(if (eq? 'match ((vector-ref code pc) in-c pc))
'match
(loop (pop-thread! threads))))))
;(fmt #t (dsp "running ") (pretty code) nl)
;; compile to closures to avoid calling match in the loop.
(upto (n code-len)
(set! code (vector-map compile-instr sym-code)))
(lambda (txt)
(add-thread! threads 0)
(let ((txt-len (string-length txt)))
(let c-loop ((c-index 0))
(if (< c-index txt-len)
;; FIXME: make step return a bool
(if (eq? 'match (step (string-ref txt c-index)))
#t
(if (no-threads? next-threads)
#f
(begin
(swap! threads next-threads)
(clear-yarn! next-threads)
(c-loop (+ 1 c-index)))))
(eq? 'match (step end-of-string))))))))
;;;--------------------------------------------------------
;;; Parser
;; FIXME: ^ and ? aren't in the grammar, and eos/$ isn't wired up
(define raw-char
(let ((meta-chars (string->list "\\^$*+?[]()|")))
(define (not-meta c)
(not (member c meta-chars)))
(p:alt (p:parse-m (p:<- c (p:accept-char not-meta))
(p:pure c))
(p:>> (p:lit "\\")
(p:accept-char (lambda (c) #t))))))
(define (bracket before after ma)
(p:>> before (p:<* ma after)))
(define (negate fn)
(lambda (c)
(not (fn c))))
;;-----------------------------------------------------------
;; Low level char combinators. These build char predicates.
;; char-rx := any non metacharacter | "\" metacharacter
;; builds a predicate that accepts the char
(define char-rx
(p:parse-m (p:<- c1 raw-char)
(p:pure (lambda (c2)
(char=? c1 c2)))))
;; range := char-rx "-" char-rx
(define range
(p:parse-m (p:<- c1 raw-char)
(p:lit "-")
(p:<- c2 raw-char)
(p:pure (lambda (c)
(char<=? c1 c c2)))))
;; set-items := range | char-rx
(define set-item (p:alt range char-rx))
(define (or-preds preds)
(lambda (c)
(let loop ((preds preds))
(if (null? preds)
#f
(or ((car preds) c)
(loop (cdr preds)))))))
;; set-items := set-item+
(define set-items
(p:lift or-preds (p:many+ set-item)))
;; negative-set := "[^" set-items "]"
(define negative-set
(bracket (p:lit "[^")
(p:lit "]")
(p:lift negate set-items)))
;; positive-set := "[" set-items "]"
(define positive-set
(bracket (p:lit "[")
(p:lit "]")
set-items))
;; set := positive-set | negative-set
(define set (p:alt positive-set negative-set))
;; eos := "$"
;; FIXME: ???
(define eos (p:lit "$"))
;; any := "."
(define any (p:>> (p:lit ".") (p:pure (lambda (_) #t))))
(define (combine rs)
(fold-left seq (car rs) (cdr rs)))
;;-----------------------------------------------------------
;; Higher level combinators, these build a symbolic rx
;; FIXME: move a hotpatch form to (utils)
(define rx
(let ((this (lambda xs #f)))
(lambda args
(if (and (= (length args) 2)
(eq? (car args) 'hotpatch))
(set! this (cadr args))
(apply this args)))))
;; group := "(" rx ")"
(define group
(bracket (p:lit "(")
(p:lit ")")
rx))
;; elementary-rx := group | any | eos | char-rx | set
;; FIXME: put eos and group back in
(define elementary-rx
(p:alt (p:lift (lambda (fn)
(list (char-instr fn)))
(p:one-of any char-rx set))
group))
;; plus-rx := elementary-rx "+"
(define plus-rx
(p:lift plus (p:<* elementary-rx (p:lit "+"))))
;; star-rx := elementary-rx "*"
(define star-rx
(p:lift star (p:<* elementary-rx (p:lit "*"))))
;; basic-rx := star-rx | plus-rx | elementary-rx
(define basic-rx
(p:one-of star-rx plus-rx elementary-rx))
;; simple-rx := basic-rx+
(define simple-rx
(p:lift combine (p:many+ basic-rx)))
;;-----------------------------------------------------------------------
;; The top level routine, parses the regex string and compiles it into a
;; matcher, or returns false if the parse failed.
;; regex :: string -> (matcher <string>)
;; FIXME: it's tempting to return a function that raises if there's a parse error.
(define regex
(let ((patched #f))
(lambda (str)
(unless patched
(set! patched #t)
;; rx := simple-rx ("|" simple-rx)*
(rx 'hotpatch
(p:lift2 (lambda (r rs)
(fold-left alt r rs))
simple-rx
(p:many* (p:>> (p:lit "|") simple-rx)))))
(receive (v st) (p:parse rx str)
(if (p:success? st)
(compile-rx v)
#f))))))