Java example source code file (CompressInputStream.java)

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Java - Java tags/keywords

base, compressconstants, compressinputstream, eofexception, filterinputstream, ioexception, nop, raw

The CompressInputStream.java Java example source code

/*
 * 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 CompressInputStream extends FilterInputStream
    implements CompressConstants
{

    public CompressInputStream(InputStream in) {
        super(in);
    }

    // buffer of unpacked 6-bit codes from last 32-word read
    int buf[] = new int[5];

    // position of next code to read in buffer (5 == end of buffer)
    int bufPos = 5;

    public int read() throws IOException {
        try {
            int code;
            do {
                code = readCode();
            } while (code == NOP);      // ignore NOP codes

            if (code >= BASE)
                return codeTable.charAt(code - BASE);
            else if (code == RAW) {
                int high = readCode();
                int low = readCode();
                return (high << 4) | low;
            } else
                throw new IOException("unknown compression code: " + code);
        } catch (EOFException e) {
            return -1;
        }
    }

    public int read(byte b[], int off, int len) throws IOException {
        if (len <= 0) {
            return 0;
        }

        int c = read();
        if (c == -1) {
            return -1;
        }
        b[off] = (byte)c;

        int i = 1;
/*****
        try {
            for (; i < len ; i++) {
                c = read();
                if (c == -1) {
                    break;
                }
                if (b != null) {
                    b[off + i] = (byte)c;
                }
            }
        } catch (IOException ee) {
        }
 *****/
        return i;
    }

    private int readCode() throws IOException {
        if (bufPos == 5) {
            int b1 = in.read();
            int b2 = in.read();
            int b3 = in.read();
            int b4 = in.read();
            if ((b1 | b2 | b3 | b4) < 0)
                throw new EOFException();
            int pack = (b1 << 24) | (b2 << 16) | (b3 << 8) | b4;
            buf[0] = (pack >>> 24) & 0x3F;
            buf[1] = (pack >>> 18) & 0x3F;
            buf[2] = (pack >>> 12) & 0x3F;
            buf[3] = (pack >>>  6) & 0x3F;
            buf[4] = (pack >>>  0) & 0x3F;
            bufPos = 0;
        }
        return buf[bufPos++];
    }
}