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;;; Guile VM code converters
;; Copyright (C) 2001 Free Software Foundation, Inc.
;; This program is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.
;;
;; This program 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 General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program; see the file COPYING. If not, write to
;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
;;; Code:
(define-module (language assembly decompile-bytecode)
#:use-module (system vm instruction)
#:use-module (system base pmatch)
#:use-module (srfi srfi-4)
#:use-module (language assembly)
#:export (decompile-bytecode))
(define (decompile-bytecode x env opts)
(let ((i 0) (size (u8vector-length x)))
(define (pop)
(let ((b (cond ((< i size) (u8vector-ref x i))
((= i size) #f)
(else (error "tried to decode too many bytes")))))
(if b (set! i (1+ i)))
b))
(let ((ret (decode-load-program pop)))
(if (= i size)
(values ret env)
(error "bad bytecode: only decoded ~a out of ~a bytes" i size)))))
(define (decode-load-program pop)
(let* ((nargs (pop)) (nrest (pop)) (nlocs (pop)) (nexts (pop))
(a (pop)) (b (pop)) (c (pop)) (d (pop))
(len (+ a (ash b 8) (ash c 16) (ash d 24)))
(i 0))
(define (sub-pop) ;; ...records. ha. ha.
(let ((b (cond ((< i len) (pop))
((= i len) #f)
(else (error "tried to decode too many bytes")))))
(if b (set! i (1+ i)))
b))
(let lp ((out '()))
(cond ((> i len)
(error "error decoding program -- read too many bytes" out))
((= i len)
`(load-program ,nargs ,nrest ,nlocs ,nexts () ,len
,@(reverse! out)))
(else
(let ((exp (decode-bytecode sub-pop)))
;; replace with labels?
(lp (cons exp out))))))))
(define (decode-bytecode pop)
(and=> (pop)
(lambda (opcode)
(let ((inst (opcode->instruction opcode)))
(cond
((eq? inst 'load-program)
(decode-load-program pop))
((< (instruction-length inst) 0)
(let* ((len (decode-length pop))
(str (make-string len)))
(let lp ((i 0))
(if (= i len)
`(,inst ,str)
(begin
(string-set! str i (integer->char (pop)))
(lp (1+ i)))))))
(else
;; fixed length
(let lp ((n (instruction-length inst)) (out (list inst)))
(if (zero? n)
(reverse! out)
(lp (1- n) (cons (pop) out))))))))))
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