com.jcraft.jsch

Interface Compression

public interface Compression

Usually not to be used by applications. An object supporting compression and decompression of data streams. If during key exchange some compression protocol was negiotated, this protocol name is looked up in the session configuration to retrieve the class name to be used for compressing/decompressing the data stream. Then an instance is created with the no-argument constructor, and initialized with the init(int, int) method. One Compression object will be used either for compression or decompression, not both.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFLATER Constant for deflating (compressing) mode.
static int	INFLATER Constant for inflating (decompressing) mode.

Method Summary

Modifier and Type	Method and Description
byte[]	compress(byte[] buf, int start, int[] len) Compresses a chunk of data.
void	init(int type, int level) Initializes the compression engine.
byte[]	uncompress(byte[] buf, int start, int[] len) Uncompresses a chunk of data.

Field Detail

INFLATER

static final int INFLATER

Constant for inflating (decompressing) mode.

See Also:

Constant Field Values

DEFLATER

static final int DEFLATER

Constant for deflating (compressing) mode.

See Also:

Constant Field Values

Method Detail

init

void init(int type,
          int level)

Initializes the compression engine.

Parameters:

type - one of INFLATER or DEFLATER. In the first case the library later will only call uncompress(byte[], int, int[]), in the second case only compress(byte[], int, int[]).

level - the compression level. This is only relevant for the DEFLATER mode.

compress

byte[] compress(byte[] buf,
                int start,
                int[] len)

Compresses a chunk of data.

Parameters:

buf - the buffer containing the uncompressed data.

start - the position in the buffer where the uncompressed data starts. At the same position we will put the compressed data.

len - an array, containing in len[0] the length of the uncompressed chunk. After returning, this will contain the length of the compressed version of this chunk.

Returns:

an array containing the compressed data. This will either be buf (if there was enough space), or a new array.

uncompress

byte[] uncompress(byte[] buf,
                  int start,
                  int[] len)

Uncompresses a chunk of data.

Parameters:

buf - the buffer containing the compressed data. We will put the uncompressed data in the same buffer, if there is enough space. Otherwise, there will be a new buffer created.

start - the position in buf where the chunk of compressed data starts.

len - an array, containing in len[0] the length of the compressed chunk. After returning, it will contain the length of the uncompressed version of this chunk.

Returns:

either buf (if there was enough space for the uncompressed data) or a new buffer containing all the data from buf before start and then the result of uncompressing the compressed chunk.