org.archive.io
Class GzipHeader

java.lang.Object
  org.archive.io.GzipHeader

public class GzipHeader
extends java.lang.Object

Read in the GZIP header. See RFC1952 for specification on what the header looks like. Assumption is that stream is cued-up with the gzip header as the next thing to be read.

Of Java and unsigned bytes. That is, its always a signed int in java no matter what the qualifier whether byte, char, etc.

Add accessors for optional filename, comment and MTIME.

Author:

stack

Field Summary

protected int	flg The GZIP header FLG byte.
protected int	length Total length of the gzip header.
static int	MINIMAL_GZIP_HEADER_LENGTH Length of minimal GZIP header.

Constructor Summary

GzipHeader()
Shutdown constructor.

GzipHeader(java.io.InputStream in)
Constructor.

Method Summary

byte[]	getFextra()
int	getFlg()
int	getLength()
int	getMtime()
int	getOs()
int	getXfl()
protected int	readByte(java.io.InputStream in) Read a byte.
protected int	readByte(java.io.InputStream in, java.util.zip.CRC32 crc) Read a byte.
protected int	readByte(java.io.InputStream in, java.util.zip.CRC32 crc, byte[] buffer, int offset, int length) Read a byte.
void	readHeader(java.io.InputStream in) Read in gzip header.
boolean	testGzipMagic(java.io.InputStream in) Test gzip magic is next in the stream.
boolean	testGzipMagic(java.io.InputStream in, java.util.zip.CRC32 crc) Test gzip magic is next in the stream.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MINIMAL_GZIP_HEADER_LENGTH

public static final int MINIMAL_GZIP_HEADER_LENGTH

Length of minimal GZIP header. See RFC1952 for explaination of value of 10.

See Also:

Constant Field Values

length

protected int length

Total length of the gzip header.

flg

protected int flg

The GZIP header FLG byte.

Constructor Detail

GzipHeader

public GzipHeader()

Shutdown constructor. Must pass an input stream.

GzipHeader

public GzipHeader(java.io.InputStream in)
           throws java.io.IOException

Constructor. This constructor advances the stream past any gzip header found.

Parameters:

in - InputStream to read from.

Throws:

java.io.IOException

Method Detail

readHeader

public void readHeader(java.io.InputStream in)
                throws java.io.IOException

Read in gzip header. Advances the stream past the gzip header.

Parameters:

in - InputStream.

Throws:

java.io.IOException - Throws if does not start with GZIP Header.

testGzipMagic

public boolean testGzipMagic(java.io.InputStream in)
                      throws java.io.IOException

Test gzip magic is next in the stream. Reads two bytes. Caller needs to manage resetting stream.

Parameters:

in - InputStream to read.

Returns:

true if found gzip magic. False otherwise or an IOException (including EOFException).

Throws:

java.io.IOException

testGzipMagic

public boolean testGzipMagic(java.io.InputStream in,
                             java.util.zip.CRC32 crc)
                      throws java.io.IOException

Test gzip magic is next in the stream. Reads two bytes. Caller needs to manage resetting stream.

Parameters:

in - InputStream to read.

crc - CRC to update.

Returns:

true if found gzip magic. False otherwise or an IOException (including EOFException).

Throws:

java.io.IOException

readByte

protected int readByte(java.io.InputStream in)
                throws java.io.IOException

Read a byte. We do not expect to get a -1 reading. If we do, we throw exception. Update the crc as we go.

Parameters:

in - InputStream to read.

Returns:

Byte read.

Throws:

java.io.IOException

readByte

protected int readByte(java.io.InputStream in,
                       java.util.zip.CRC32 crc)
                throws java.io.IOException

Read a byte. We do not expect to get a -1 reading. If we do, we throw exception. Update the crc as we go.

Parameters:

in - InputStream to read.

crc - CRC to update.

Returns:

Byte read.

Throws:

java.io.IOException

readByte

protected int readByte(java.io.InputStream in,
                       java.util.zip.CRC32 crc,
                       byte[] buffer,
                       int offset,
                       int length)
                throws java.io.IOException

Read a byte. We do not expect to get a -1 reading. If we do, we throw exception. Update the crc as we go.

Parameters:

in - InputStream to read.

crc - CRC to update.

buffer - Buffer to read into.

offset - Offset to start filling buffer at.

length - How much to read.

Returns:

Bytes read.

Throws:

java.io.IOException

getFextra

public byte[] getFextra()

Returns:

Returns the fextra.

getFlg

public int getFlg()

Returns:

Returns the flg.

getOs

public int getOs()

Returns:

Returns the os.

getXfl

public int getXfl()

Returns:

Returns the xfl.

getMtime

public int getMtime()

Returns:

Returns the mtime.

getLength

public int getLength()

Returns:

Returns the length.