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;;; Guile Virtual Machine Assembly
;; Copyright (C) 2001, 2009 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)
#:use-module (rnrs bytevector)
#:use-module (system base pmatch)
#:use-module (system vm instruction)
#:use-module ((srfi srfi-1) #:select (fold))
#:export (byte-length
addr+ align-program align-code
assembly-pack assembly-unpack
object->assembly assembly->object))
;; nargs, nrest, nlocs, nexts, len, metalen
(define *program-header-len* (+ 1 1 1 1 4 4))
;; lengths are encoded in 3 bytes
(define *len-len* 3)
(define (byte-length assembly)
(pmatch assembly
(,label (guard (not (pair? label)))
0)
((load-unsigned-integer ,str)
(+ 1 *len-len* (string-length str)))
((load-integer ,str)
(+ 1 *len-len* (string-length str)))
((load-number ,str)
(+ 1 *len-len* (string-length str)))
((load-string ,str)
(+ 1 *len-len* (string-length str)))
((load-symbol ,str)
(+ 1 *len-len* (string-length str)))
((load-keyword ,str)
(+ 1 *len-len* (string-length str)))
((load-array ,bv)
(+ 1 *len-len* (bytevector-length bv)))
((define ,str)
(+ 1 *len-len* (string-length str)))
((load-program ,nargs ,nrest ,nlocs ,nexts ,labels ,len ,meta . ,code)
(+ 1 *program-header-len* len (if meta (1- (byte-length meta)) 0)))
((,inst . _) (guard (>= (instruction-length inst) 0))
(+ 1 (instruction-length inst)))
(else (error "unknown instruction" assembly))))
(define *program-alignment* 8)
(define (addr+ addr code)
(fold (lambda (x len) (+ (byte-length x) len))
addr
code))
(define (align-code code addr alignment header-len)
`(,@(make-list (modulo (- alignment
(modulo (+ addr header-len) alignment))
alignment)
'(nop))
,code))
(define (align-program prog addr)
(align-code prog addr *program-alignment* 1))
;;;
;;; Code compress/decompression
;;;
(define *abbreviations*
'(((make-int8 0) . (make-int8:0))
((make-int8 1) . (make-int8:1))))
(define *expansions*
(map (lambda (x) (cons (cdr x) (car x))) *abbreviations*))
(define (assembly-pack code)
(or (assoc-ref *abbreviations* code)
code))
(define (assembly-unpack code)
(or (assoc-ref *expansions* code)
code))
;;;
;;; Encoder/decoder
;;;
(define (object->assembly x)
(cond ((eq? x #t) `(make-true))
((eq? x #f) `(make-false))
((null? x) `(make-eol))
((and (integer? x) (exact? x))
(cond ((and (<= -128 x) (< x 128))
`(make-int8 ,(modulo x 256)))
((and (<= -32768 x) (< x 32768))
(let ((n (if (< x 0) (+ x 65536) x)))
`(make-int16 ,(quotient n 256) ,(modulo n 256))))
(else #f)))
((char? x) `(make-char8 ,(char->integer x)))
(else #f)))
(define (assembly->object code)
(pmatch code
((make-true) #t)
((make-false) #f) ;; FIXME: Same as the `else' case!
((make-eol) '())
((make-int8 ,n)
(if (< n 128) n (- n 256)))
((make-int16 ,n1 ,n2)
(let ((n (+ (* n1 256) n2)))
(if (< n 32768) n (- n 65536))))
((make-char8 ,n)
(integer->char n))
((load-string ,s) s)
((load-symbol ,s) (string->symbol s))
((load-keyword ,s) (symbol->keyword (string->symbol s)))
(else #f)))
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