/*
 * Copyright (c) 2005, 2018, 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,
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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.
/** 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); } }