CompressOutputStream.java

/*
 * Copyright (c) 1998, 2008, 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.
 *
 * 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.
 */

/*
 */

import java.io.*;

class CompressOutputStream extends FilterOutputStream
    implements CompressConstants
{

    public CompressOutputStream(OutputStream out) {
        super(out);
    }

    // buffer of 6-bit codes to pack into next 32-bit word
    int buf[] = new int[5];

    // number of valid codes pending in buffer
    int bufPos = 0;

    public void write(int b) throws IOException {
        b &= 0xFF;                      // force argument to a byte

        int pos = codeTable.indexOf((char)b);
        if (pos != -1)
            writeCode(BASE + pos);
        else {
            writeCode(RAW);
            writeCode(b >> 4);
            writeCode(b & 0xF);
        }
    }

    public void write(byte b[], int off, int len) throws IOException {
        /*
         * This is quite an inefficient implementation, because it has to
         * call the other write method for every byte in the array.  It
         * could be optimized for performance by doing all the processing
         * in this method.
         */
        for (int i = 0; i < len; i++)
            write(b[off + i]);
    }

    public void flush() throws IOException {
        while (bufPos > 0)
            writeCode(NOP);
    }

    private void writeCode(int c) throws IOException {
        buf[bufPos++] = c;
        if (bufPos == 5) {      // write next word when we have 5 codes
            int pack = (buf[0] << 24) | (buf[1] << 18) | (buf[2] << 12) |
                       (buf[3] << 6) | buf[4];
            out.write((pack >>> 24) & 0xFF);
            out.write((pack >>> 16) & 0xFF);
            out.write((pack >>> 8)  & 0xFF);
            out.write((pack >>> 0)  & 0xFF);
            bufPos = 0;
        }
    }
}