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usr
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share
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guile
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2.2
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ice-9
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peg
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cache.scm
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;;;; cache.scm --- cache the results of parsing ;;;; ;;;; Copyright (C) 2010, 2011 Free Software Foundation, Inc. ;;;; ;;;; This library is free software; you can redistribute it and/or ;;;; modify it under the terms of the GNU Lesser General Public ;;;; License as published by the Free Software Foundation; either ;;;; version 3 of the License, or (at your option) any later version. ;;;; ;;;; This library is distributed in the hope that it will be useful, ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ;;;; Lesser General Public License for more details. ;;;; ;;;; You should have received a copy of the GNU Lesser General Public ;;;; License along with this library; if not, write to the Free Software ;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA ;;;; (define-module (ice-9 peg cache) #:export (cg-cached-parser)) ;; The results of parsing using a nonterminal are cached. Think of it like a ;; hash with no conflict resolution. Process for deciding on the cache size ;; wasn't very scientific; just ran the benchmarks and stopped a little after ;; the point of diminishing returns on my box. (define *cache-size* 512) (define (make-cache) (make-vector *cache-size* #f)) ;; given a syntax object which is a parser function, returns syntax ;; which, if evaluated, will become a parser function that uses a cache. (define (cg-cached-parser parser) #`(let ((cache (make-cache))) (lambda (str strlen at) (let* ((vref (vector-ref cache (modulo at *cache-size*)))) ;; Check to see whether the value is cached. (if (and vref (eq? (car vref) str) (= (cadr vref) at)) (caddr vref);; If it is return it. (let ((fres ;; Else calculate it and cache it. (#,parser str strlen at))) (vector-set! cache (modulo at *cache-size*) (list str at fres)) fres))))))