124 lines
4.7 KiB
Java
124 lines
4.7 KiB
Java
/*
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* Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package com.sun.imageio.plugins.common;
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import java.io.IOException;
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import javax.imageio.stream.ImageOutputStream;
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/*
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* Came from GIFEncoder initially.
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* Modified - to allow for output compressed data without the block counts
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* which breakup the compressed data stream for GIF.
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*/
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public class BitFile {
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ImageOutputStream output;
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byte buffer[];
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int index;
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int bitsLeft; // bits left at current index that are avail.
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/** note this also indicates gif format BITFile. **/
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boolean blocks = false;
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/*
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* @param output destination for output data
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* @param blocks GIF LZW requires block counts for output data
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*/
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public BitFile(ImageOutputStream output, boolean blocks) {
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this.output = output;
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this.blocks = blocks;
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buffer = new byte[256];
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index = 0;
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bitsLeft = 8;
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}
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public void flush() throws IOException {
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int numBytes = index + (bitsLeft == 8 ? 0 : 1);
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if (numBytes > 0) {
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if (blocks) {
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output.write(numBytes);
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}
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output.write(buffer, 0, numBytes);
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buffer[0] = 0;
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index = 0;
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bitsLeft = 8;
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}
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}
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public void writeBits(int bits, int numbits) throws IOException {
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int bitsWritten = 0;
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int numBytes = 255; // gif block count
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do {
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// This handles the GIF block count stuff
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if ((index == 254 && bitsLeft == 0) || index > 254) {
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if (blocks) {
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output.write(numBytes);
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}
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output.write(buffer, 0, numBytes);
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buffer[0] = 0;
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index = 0;
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bitsLeft = 8;
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}
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if (numbits <= bitsLeft) { // bits contents fit in current index byte
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if (blocks) { // GIF
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buffer[index] |= (bits & ((1 << numbits) - 1)) << (8 - bitsLeft);
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bitsWritten += numbits;
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bitsLeft -= numbits;
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numbits = 0;
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} else {
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buffer[index] |= (bits & ((1 << numbits) - 1)) << (bitsLeft - numbits);
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bitsWritten += numbits;
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bitsLeft -= numbits;
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numbits = 0;
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}
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} else { // bits overflow from current byte to next.
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if (blocks) { // GIF
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// if bits > space left in current byte then the lowest order bits
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// of code are taken and put in current byte and rest put in next.
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buffer[index] |= (bits & ((1 << bitsLeft) - 1)) << (8 - bitsLeft);
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bitsWritten += bitsLeft;
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bits >>= bitsLeft;
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numbits -= bitsLeft;
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buffer[++index] = 0;
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bitsLeft = 8;
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} else {
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// if bits > space left in current byte then the highest order bits
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// of code are taken and put in current byte and rest put in next.
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// at highest order bit location !!
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int topbits = (bits >>> (numbits - bitsLeft)) & ((1 << bitsLeft) - 1);
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buffer[index] |= topbits;
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numbits -= bitsLeft; // ok this many bits gone off the top
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bitsWritten += bitsLeft;
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buffer[++index] = 0; // next index
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bitsLeft = 8;
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}
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}
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} while (numbits != 0);
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}
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}
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