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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 (system vm conv)
:use-module ((system vm core)
:select (instruction? instruction-length
instruction->opcode opcode->instruction))
:use-module (system base pmatch)
:use-module (ice-9 regex)
:use-module (srfi srfi-4)
:use-module (srfi srfi-1)
:export (code-pack code-unpack object->code code->object code->bytes
make-byte-decoder))
;;;
;;; Code compress/decompression
;;;
(define (code-pack code)
(pmatch code
((inst ,n) (guard (integer? n))
(cond ((< n 10)
(let ((abbrev (string->symbol (format #f "~A:~A" inst n))))
(if (instruction? abbrev) (list abbrev) code)))
(else code)))
(else code)))
(define (code-unpack code)
(let ((inst (symbol->string (car code))))
(cond
((string-match "^([^:]*):([0-9]+)$" inst) =>
(lambda (data)
(cons* (string->symbol (match:substring data 1))
(string->number (match:substring data 2))
(cdr code))))
(else code))))
;;;
;;; Encoder/decoder
;;;
(define (object->code 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 (code->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)))
; (let ((c->o code->object))
; (set! code->object
; (lambda (code)
; (format #t "code->object: ~a~%" code)
; (let ((ret (c->o code)))
; (format #t "code->object returned ~a~%" ret)
; ret))))
(define (code->bytes code)
(define (string->u8vector str)
(apply u8vector (map char->integer (string->list str))))
(let* ((code (code-pack code))
(inst (car code))
(rest (cdr code))
(len (instruction-length inst))
(head (instruction->opcode inst)))
(cond ((< len 0)
;; Variable-length code
;; Typical instructions are `link' and `load-program'.
(if (string? (car rest))
(set-car! rest (string->u8vector (car rest))))
(let* ((str (car rest))
(str-len (u8vector-length str))
(encoded-len (encode-length str-len))
(encoded-len-len (u8vector-length encoded-len)))
(apply u8vector
(append (cons head (u8vector->list encoded-len))
(u8vector->list str)))))
((= len (length rest))
;; Fixed-length code
(apply u8vector (cons head rest)))
(else
(error "Invalid code:" code)))))
; (let ((c->b code->bytes))
; ;; XXX: Debugging output
; (set! code->bytes
; (lambda (code)
; (format #t "code->bytes: ~a~%" code)
; (let ((result (c->b code)))
; (format #t "code->bytes: returned ~a~%" result)
; result))))
(define (make-byte-decoder bytes)
(let ((addr 0) (size (u8vector-length bytes)))
(define (pop)
(let ((byte (u8vector-ref bytes addr)))
(set! addr (1+ addr))
byte))
(define (sublist lst start end)
(take (drop lst start) (- end start)))
(lambda ()
(if (< addr size)
(let* ((start addr)
(inst (opcode->instruction (pop)))
(n (instruction-length inst))
(code (if (< n 0)
;; variable length
(let* ((end (+ (decode-length pop) addr))
(subbytes (sublist
(u8vector->list bytes)
addr end))
(->string? (not (eq? inst 'load-program))))
(set! addr end)
(list inst
(if ->string?
(list->string
(map integer->char subbytes))
(apply u8vector subbytes))))
;; fixed length
(do ((n n (1- n))
(l '() (cons (pop) l)))
((= n 0) (cons* inst (reverse! l)))))))
(values start code))
#f))))
;;;
;;; Variable-length interface
;;;
;; NOTE: decoded in vm_fetch_length in vm.c as well.
(define (encode-length len)
(cond ((< len 254) (u8vector len))
((< len (* 256 256))
(u8vector 254 (quotient len 256) (modulo len 256)))
((< len most-positive-fixnum)
(u8vector 255
(quotient len (* 256 256 256))
(modulo (quotient len (* 256 256)) 256)
(modulo (quotient len 256) 256)
(modulo len 256)))
(else (error "Too long code length:" len))))
(define (decode-length pop)
(let ((len (pop)))
(cond ((< len 254) len)
((= len 254) (+ (* (pop) 256) (pop)))
(else (+ (* (pop) 256 256 256)
(* (pop) 256 256)
(* (pop) 256)
(pop))))))
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