/*
 
* Copyright (c) 1996, 2013, 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
 
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*/

package java.util.zip;

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

/**
 
* This class implements a stream filter for writing compressed data in
 
* the GZIP file format.
 
* @author
      
David Connelly
 
*
 
*/

public
class
GZIPOutputStream extends DeflaterOutputStream {
    
/**
     
* CRC-32 of uncompressed data.
     
*/
    
protected CRC32 crc = new CRC32();

    
/*
     
* GZIP header magic number.
     
*/
    
private final static int GZIP_MAGIC = 0x8b1f;

    
/*
     
* Trailer size in bytes.
     
*
     
*/
    
private final static int TRAILER_SIZE = 8;

    
/**
     
* Creates a new output stream with the specified buffer size.
     
*
     
* <p>The new output stream instance is created as if by invoking
     
* the 3-argument constructor GZIPOutputStream(out, size, false).
     
*
     
* @param out the output stream
     
* @param size the output buffer size
     
* @exception IOException If an I/O error has occurred.
     
* @exception IllegalArgumentException if {@code size <= 0}
     
*/

    
public GZIPOutputStream(OutputStream out, int size) throws IOException {
        
this(out, size, false);
    
}

    
/**
     
* Creates a new output stream with the specified buffer size and
     
* flush mode.
     
*
     
* @param out the output stream
     
* @param size the output buffer size
     
* @param syncFlush
     
*
        
if {@code true} invocation of the inherited
     
*
        
{@link DeflaterOutputStream#flush() flush()} method of
     
*
        
this instance flushes the compressor with flush mode
     
*
        
{@link Deflater#SYNC_FLUSH} before flushing the output
     
*
        
stream, otherwise only flushes the output stream
     
* @exception IOException If an I/O error has occurred.
     
* @exception IllegalArgumentException if {@code size <= 0}
     
*
     
* @since 1.7
     
*/

    
public GZIPOutputStream(OutputStream out, int size, boolean syncFlush)
        
throws IOException
    
{
        
super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true),
              
size,
              
syncFlush);
        
usesDefaultDeflater = true;
        
writeHeader();
        
crc.reset();
    
}


    
/**
     
* Creates a new output stream with a default buffer size.
     
*
     
* <p>The new output stream instance is created as if by invoking
     
* the 2-argument constructor GZIPOutputStream(out, false).
     
*
     
* @param out the output stream
     
* @exception IOException If an I/O error has occurred.
     
*/

    
public GZIPOutputStream(OutputStream out) throws IOException {
        
this(out, 512, false);
    
}

    
/**
     
* Creates a new output stream with a default buffer size and
     
* the specified flush mode.
     
*
     
* @param out the output stream
     
* @param syncFlush
     
*
        
if {@code true} invocation of the inherited
     
*
        
{@link DeflaterOutputStream#flush() flush()} method of
     
*
        
this instance flushes the compressor with flush mode
     
*
        
{@link Deflater#SYNC_FLUSH} before flushing the output
     
*
        
stream, otherwise only flushes the output stream
     
*
     
* @exception IOException If an I/O error has occurred.
     
*
     
* @since 1.7
     
*/

    
public GZIPOutputStream(OutputStream out, boolean syncFlush)
        
throws IOException
    
{
        
this(out, 512, syncFlush);
    
}

    
/**
     
* Writes array of bytes to the compressed output stream. This method
     
* will block until all the bytes are written.
     
* @param buf the data to be written
     
* @param off the start offset of the data
     
* @param len the length of the data
     
* @exception IOException If an I/O error has occurred.
     
*/

    
public synchronized void write(byte[] buf, int off, int len)
        
throws IOException
    
{
        
super.write(buf, off, len);
        
crc.update(buf, off, len);
    
}

    
/**
     
* Finishes writing compressed data to the output stream without closing
     
* the underlying stream. Use this method when applying multiple filters
     
* in succession to the same output stream.
     
* @exception IOException if an I/O error has occurred
     
*/

    
public void finish() throws IOException {
        
if (!def.finished()) {
            
def.finish();
            
while (!def.finished()) {
                
int len = def.deflate(buf, 0, buf.length);
                
if (def.finished() && len <= buf.length - TRAILER_SIZE) {
                    
// last deflater buffer. Fit trailer at the end
                    
writeTrailer(buf, len);
                    
len = len + TRAILER_SIZE;
                    
out.write(buf, 0, len);
                    
return;
                
}
                
if (len > 0)
                    
out.write(buf, 0, len);
            
}
            
// if we can't fit the trailer at the end of the last
            
// deflater buffer, we write it separately
            
byte[] trailer = new byte[TRAILER_SIZE];
            
writeTrailer(trailer, 0);
            
out.write(trailer);
        
}
    
}

    
/*
     
* Writes GZIP member header.
     
*/
    
private void writeHeader() throws IOException {
        
out.write(new byte[] {
                      
(byte) GZIP_MAGIC,
        
// Magic number (short)
                      
(byte)(GZIP_MAGIC >> 8),
  
// Magic number (short)
                      
Deflater.DEFLATED,
        
// Compression method (CM)
                      
0,
                        
// Flags (FLG)
                      
0,
                        
// Modification time MTIME (int)
                      
0,
                        
// Modification time MTIME (int)
                      
0,
                        
// Modification time MTIME (int)
                      
0,
                        
// Modification time MTIME (int)
                      
0,
                        
// Extra flags (XFLG)
                      
0
                         
// Operating system (OS)
                  
});
    
}

    
/*
     
* Writes GZIP member trailer to a byte array, starting at a given
     
* offset.
     
*/

    
private void writeTrailer(byte[] buf, int offset) throws IOException {
        
writeInt((int)crc.getValue(), buf, offset); // CRC-32 of uncompr. data
        
writeInt(def.getTotalIn(), buf, offset + 4); // Number of uncompr. bytes
    
}

    
/*
     
* Writes integer in Intel byte order to a byte array, starting at a
     
* given offset.
     
*/

    
private void writeInt(int i, byte[] buf, int offset) throws IOException {
        
writeShort(i & 0xffff, buf, offset);
        
writeShort((i >> 16) & 0xffff, buf, offset + 2);
    
}

    
/*
     
* Writes short integer in Intel byte order to a byte array, starting
     
* at a given offset
     
*/

    
private void writeShort(int s, byte[] buf, int offset) throws IOException {
        
buf[offset] = (byte)(s & 0xff);
        
buf[offset + 1] = (byte)((s >> 8) & 0xff);
    
}
}