org.hd.d.pg2k.webSvr.util
Class FlushableGZIPOutputStream

java.lang.Object
  java.io.OutputStream
      java.io.FilterOutputStream
          net.sf.jazzlib.DeflaterOutputStream
              org.hd.d.pg2k.webSvr.util.FlushableGZIPOutputStream

All Implemented Interfaces:

java.io.Closeable, java.io.Flushable

public class FlushableGZIPOutputStream
extends net.sf.jazzlib.DeflaterOutputStream

Substitute for GZIPOutputStream that maximises compression and has a usable flush(). This is also more careful about its output writes for efficiency, and indeed buffers them to minimise the number of write()s downstream. This is especially useful where each write() potentially has a significant cost such as an OS call, a disc write, or a network packet.

This will automatically throttle back from maximum to default compression (which usually yields nearly as good results on significantly less effort) when the system is conserving power/energy.

crc

private final java.util.zip.CRC32 crc

GZIP_MAGIC

private static final int GZIP_MAGIC

See Also:

Constant Field Values

os

private final java.io.OutputStream os

somethingWritten

private boolean somethingWritten

Note when input has arrived and not yet been compressed and flushed downstream.

header

private static final byte[] header

Constant (10-byte) header array. All zeros except magic number and algorithm.

TRAILER_BYTES

private static final int TRAILER_BYTES

Length of the trailer in bytes.

See Also:

Constant Field Values

FlushableGZIPOutputStream

public FlushableGZIPOutputStream(java.io.OutputStream os)
                          throws java.io.IOException

Creates flush()able equivalent of GZIPOutputStream, with maximum/best compression and default output buffer size. Useful for, for example, HTTP compression.

Parameters:

os - underlying output stream; must not be null

Throws:

java.io.IOException

FlushableGZIPOutputStream

public FlushableGZIPOutputStream(java.io.OutputStream os,
                                 int bufsize)
                          throws java.io.IOException

Creates flush()able equivalent of GZIPOutputStream, with good compression. Useful for, for example, HTTP compression.

Parameters:

os - underlying output stream; must not be null

bufsize - output buffer size; must be positive

Throws:

java.io.IOException

write

public void write(byte[] buf,
                  int off,
                  int len)
           throws java.io.IOException

All output is written via this routine.

Overrides:

write in class net.sf.jazzlib.DeflaterOutputStream

Throws:

java.io.IOException

flush

public void flush()
           throws java.io.IOException

Flush any accumulated input downstream in compressed form. We overcome some bugs/misfeatures here so that:

• We won't allow the GZIP header to be flushed on its own without real compressed data in the same write downstream.
• We ensure that any accumulated uncompressed data really is forced through the compressor.
• We prevent spurious empty compressed blocks being produced from successive flush()es with no intervening new data.

Specified by:

flush in interface java.io.Flushable

Overrides:

flush in class net.sf.jazzlib.DeflaterOutputStream

Throws:

java.io.IOException

close

public void close()
           throws java.io.IOException

Flush out any remaining compressed data, add the trailer, and close the stream.

Specified by:

close in interface java.io.Closeable

Overrides:

close in class net.sf.jazzlib.DeflaterOutputStream

Throws:

java.io.IOException

writeHeader

private void writeHeader()
                  throws java.io.IOException

Write header directly downstream.

Throws:

java.io.IOException

generateTrailer

private byte[] generateTrailer()

Return header to write downstream.