From f67f8d68b33a5d0b2ae2409a81c30d852a475ebe Mon Sep 17 00:00:00 2001 From: Masaya Tojo Date: Fri, 9 Aug 2024 02:28:45 +0900 Subject: Add `unsafe?` option for image creation procedures - Add (private bitwise) module and use it - Add (private checker) module and use it - Add (private double-byte) module and use it --- pnm/private/double-byte.scm | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) create mode 100644 pnm/private/double-byte.scm (limited to 'pnm/private/double-byte.scm') diff --git a/pnm/private/double-byte.scm b/pnm/private/double-byte.scm new file mode 100644 index 0000000..fd40336 --- /dev/null +++ b/pnm/private/double-byte.scm @@ -0,0 +1,29 @@ +;;; R7RS-PNM --- Library for reading and writing PNM (Portable Any Map) files for R7RS +;;; Copyright © 2024 Masaya Tojo +;;; +;;; This file is part of R7RS-PNM. +;;; +;;; R7RS-PNM 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. +;;; +;;; R7RS-PNM 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 R7RS-PNM. If not, see . + +(define-library (pnm private double-byte) + (export split-double-byte combine-bytes) + (import (scheme base) + (pnm private bitwise)) + (begin + (define (split-double-byte v) + (values (arithmetic-shift v -8) + (bitwise-and v 255))) + + (define (combine-bytes l r) + (bitwise-ior (arithmetic-shift l 8) r)))) -- cgit v1.2.3