/*

 * 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);

    }

}