src/java/org/apache/xmlgraphics/util/io/ASCII85OutputStream.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* $Id$ */

package org.apache.xmlgraphics.util.io;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * This class applies a ASCII85 encoding to the stream.
 *
 * @version $Id$
 */
public class ASCII85OutputStream extends FilterOutputStream
            implements ASCII85Constants, Finalizable {

    private static final boolean DEBUG = false;

    private int pos = 0;
    private long buffer = 0;
    private int posinline = 0;
    private int bw = 0;

    /** @see java.io.FilterOutputStream **/
    public ASCII85OutputStream(OutputStream out) {
        super(out);
    }

    /** @see java.io.FilterOutputStream **/
    public void write(int b) throws IOException {
        if (pos == 0) {
            buffer += (b << 24) & 0xff000000L;
        } else if (pos == 1) {
            buffer += (b << 16) & 0xff0000L;
        } else if (pos == 2) {
            buffer += (b << 8) & 0xff00L;
        } else {
            buffer += b & 0xffL;
        }
        pos++;

        if (pos > 3) {
            checkedWrite(convertWord(buffer));
            buffer = 0;
            pos = 0;
        }
    }

    /* UNUSED ATM
    private void checkedWrite(int b) throws IOException {
        if (posinline == 80) {
            out.write(EOL); bw++;
            posinline = 0;
        }
        checkedWrite(b);
        posinline++;
        bw++;
    }*/

    private void checkedWrite(byte[] buf) throws IOException {
        checkedWrite(buf, buf.length, false);
    }

    private void checkedWrite(byte[] buf, boolean nosplit) throws IOException {
        checkedWrite(buf, buf.length, nosplit);
    }

    private void checkedWrite(byte[] buf , int len) throws IOException {
        checkedWrite(buf, len, false);
    }

    private void checkedWrite(byte[] buf , int len, boolean nosplit) throws IOException {
        if (posinline + len > 80) {
            int firstpart = (nosplit ? 0 : len - (posinline + len - 80));
            if (firstpart > 0) {
                out.write(buf, 0, firstpart);
            }
            out.write(EOL);
            bw++;
            int rest = len - firstpart;
            if (rest > 0) {
                out.write(buf, firstpart, rest);
            }
            posinline = rest;
        } else {
            out.write(buf, 0, len);
            posinline += len;
        }
        bw += len;
    }

    /**
     * This converts a 32 bit value (4 bytes) into 5 bytes using base 85.
     * each byte in the result starts with zero at the '!' character so
     * the resulting base85 number fits into printable ascii chars
     *
     * @param word the 32 bit unsigned (hence the long datatype) word
     * @return 5 bytes (or a single byte of the 'z' character for word
     * values of 0)
     */
    private byte[] convertWord(long word) {
        word = word & 0xffffffff;

        if (word == 0) {
            return ZERO_ARRAY;
        } else {
            if (word < 0) {
                word = -word;
            }
            byte c1 =
                (byte)((word
                        / POW85[0]) & 0xFF);
            byte c2 =
                (byte)(((word - (c1 * POW85[0]))
                        / POW85[1]) & 0xFF);
            byte c3 =
                (byte)(((word - (c1 * POW85[0])
                              - (c2 * POW85[1]))
                        / POW85[2]) & 0xFF);
            byte c4 =
                (byte)(((word - (c1 * POW85[0])
                              - (c2 * POW85[1])
                              - (c3 * POW85[2]))
                        / POW85[3]) & 0xFF);
            byte c5 =
                (byte)(((word - (c1 * POW85[0])
                              - (c2 * POW85[1])
                              - (c3 * POW85[2])
                              - (c4 * POW85[3])))
                        & 0xFF);

            byte[] ret = {
                (byte)(c1 + START), (byte)(c2 + START),
                (byte)(c3 + START), (byte)(c4 + START),
                (byte)(c5 + START)
            };

            if (DEBUG) {
                for (int i = 0; i < ret.length; i++) {
                    if (ret[i] < 33 || ret[i] > 117) {
                        System.out.println("Illegal char value "
                                        + new Integer(ret[i]));
                    }
                }
            }
            return ret;
        }
    }

    /** @see Finalizable **/
    public void finalizeStream() throws IOException {
        // now take care of the trailing few bytes.
        // with n leftover bytes, we append 0 bytes to make a full group of 4
        // then convert like normal (except not applying the special zero rule)
        // and write out the first n+1 bytes from the result
        if (pos > 0) {
            int rest = pos;
            /*
            byte[] lastdata = new byte[4];
            int i = 0;
            for (int j = 0; j < 4; j++) {
                if (j < rest) {
                    lastdata[j] = data[i++];
                } else {
                    lastdata[j] = 0;
                }
            }

            long val = ((lastdata[0] << 24) & 0xff000000L)
                       + ((lastdata[1] << 16) & 0xff0000L)
                       + ((lastdata[2] << 8) & 0xff00L)
                       + (lastdata[3] & 0xffL);
            */

            byte[] conv;
            // special rule for handling zeros at the end
            if (buffer != 0) {
                conv = convertWord(buffer);
            } else {
                conv = new byte[5];
                for (int j = 0; j < 5; j++) {
                    conv[j] = (byte)'!';
                }
            }
            // assert rest+1 <= 5
            checkedWrite(conv, rest + 1);
        }
        // finally write the two character end of data marker
        checkedWrite(EOD, true);

        flush();
        if (out instanceof Finalizable) {
            ((Finalizable)out).finalizeStream();
        }
    }

    /** @see java.io.FilterOutputStream **/
    public void close() throws IOException {
        finalizeStream();
        super.close();
    }

}