/*
* JBoss, Home of Professional Open Source.
* Copyright 2008, Red Hat Middleware LLC, and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.test.jrmp.ejb;
import java.io.*;
class CompressionOutputStream extends FilterOutputStream
implements CompressionConstants
{
/*
* Constructor calls constructor of superclass.
*/
public CompressionOutputStream(OutputStream out) {
super(out);
}
/*
* Buffer of 6-bit codes to pack into next 32-bit word
* Five 6-bit codes fit into 4 words.
*/
int buf[] = new int[5];
/*
* Index of valid codes waiting in buf.
*/
int bufPos = 0;
/*
* This method writes one byte to the socket stream.
*/
public void write(int b) throws IOException {
// force argument to one byte
b &= 0xFF;
// Look up pos in codeTable to get its encoding.
int pos = codeTable.indexOf((char)b);
if (pos != -1){
// If pos is in the codeTable, write BASE + pos into buf.
// By adding BASE to pos, we know that the characters in
// the codeTable will always have a code between 2 and 63
// inclusive. This allows us to use RAW (RAW is equal to
// 1) to signify that the next two groups of 6-bits are
// necessary for decompression of the next character.
writeCode(BASE + pos);
} else {
// Otherwise, write RAW into buf to signify that the
// Character is being sent in 12 bits.
writeCode(RAW);
// Write the last 4 bits of b into the buf.
writeCode(b >> 4);
// Truncate b to contain data in only the first 4 bits,
// and write the first 4 bits of b into buf.
writeCode(b & 0xF);
}
}
/*
* This method writes up to len bytes to the socket stream.
*/
public void write(byte b[], int off, int len) throws IOException {
/*
* This implementation is quite inefficient 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]);
}
/*
* Clears buffer of all data (zeroes it out).
*/
public void flush() throws IOException {
while (bufPos > 0)
writeCode(NOP);
}
/*
* This method actually puts the data into the output stream after
* packing the data from all 5 bytes in buf into one word.
* Remember, each byte has, at most, 6 significant bits.
*/
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;
}
}
}