org.armedbear.lisp.byte-io.lisp Maven / Gradle / Ivy
;;; byte-io.lisp
;;;
;;; Copyright (C) 2004-2005 Peter Graves
;;; $Id$
;;;
;;; 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
;;; of the License, 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; if not, write to the Free Software
;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
;;;
;;; As a special exception, the copyright holders of this library give you
;;; permission to link this library with independent modules to produce an
;;; executable, regardless of the license terms of these independent
;;; modules, and to copy and distribute the resulting executable under
;;; terms of your choice, provided that you also meet, for each linked
;;; independent module, the terms and conditions of the license of that
;;; module. An independent module is a module which is not derived from
;;; or based on this library. If you modify this library, you may extend
;;; this exception to your version of the library, but you are not
;;; obligated to do so. If you do not wish to do so, delete this
;;; exception statement from your version.
(in-package #:system)
(defun write-byte (byte stream)
(declare (type stream stream))
(let ((element-type (expand-deftype (stream-element-type stream))))
(require-type byte element-type)
(let ((width (cadr element-type)))
(if (= width 8)
(write-8-bits (the (unsigned-byte 8) byte) stream)
(let ((bytes ()))
(dotimes (i (/ width 8))
(push (logand byte #xff) bytes)
(setf byte (ash byte -8)))
(dolist (b bytes)
(write-8-bits (the (unsigned-byte 8) b) stream)))))
byte))
(defun read-byte (stream &optional (eof-error-p t) eof-value)
(declare (type stream stream))
(let* ((element-type (expand-deftype (stream-element-type stream))))
(unless element-type
(if eof-error-p
(error 'end-of-file :stream stream)
(return-from read-byte eof-value)))
(unless (consp element-type)
(error 'simple-type-error
:format-control "READ-BYTE: unsupported element type ~S."
:format-arguments (list element-type)))
(let ((width (cadr element-type)))
(if (= width 8)
(read-8-bits stream eof-error-p eof-value)
(let ((result 0))
(dotimes (i (/ width 8))
(let ((byte (read-8-bits stream eof-error-p eof-value)))
(when (eq byte eof-value)
(return-from read-byte eof-value))
(setf result (ash result 8))
(setf result (+ result byte))))
(if (and (eq (car element-type) 'signed-byte)
(not (zerop (logand result (expt 2 (1- width))))))
(- result (expt 2 width))
result))))))