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