Package org.jpedal.io.filter

Class LZWInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

org.jpedal.io.filter.LZWInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class LZWInputStream
extends FilterInputStream

An input stream that lazily decodes LZW encoded data from the wrapped stream

Data encoded using the LZW compression method shall consist of a sequence of codes that are 9 to 12 bits long. Each code shall represent a single character of input data (0–255), a clear-table marker (256), an EOD marker (257), or a table entry representing a multiple-character sequence that has been encountered previously in the input (258 or greater).

Initially, the code length shall be 9 bits and the LZW table shall contain only entries for the 258 fixed codes. As encoding proceeds, entries shall be appended to the table, associating new codes with longer and longer sequences of input characters. The encoder and the decoder shall maintain identical copies of this table.

Whenever both the encoder and the decoder independently (but synchronously) realise that the current code length is no longer sufficient to represent the number of entries in the table, they shall increase the number of bits per code by 1. The first output code that is 10 bits long shall be the one following the creation of table entry 511, and similarly for 11 (1023) and 12 (2047) bits. Codes shall never be longer than 12 bits; therefore, entry 4095 is the last entry of the LZW table.

For more details on decoding, check the Adobe TIFF Revision 6.0 spec, which defines the full algorithm.

Constructor Summary

Constructors

Constructor	Description
LZWInputStream(InputStream in)
LZWInputStream(InputStream in, boolean earlyChange)
LZWInputStream(InputStream in, LZWFilterOptions filterOptions)

Method Summary

Modifier and Type	Method	Description
int	available()
boolean	markSupported()
int	read()
int	read(byte[] outputBytes, int offset, int byteCount)
long	skip(long n)

Methods inherited from class java.io.FilterInputStream

close, mark, read, reset

Methods inherited from class java.io.InputStream

nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

Methods inherited from class java.lang.Object

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

Constructor Details

LZWInputStream

public LZWInputStream(InputStream in)

LZWInputStream

public LZWInputStream(InputStream in,
 LZWFilterOptions filterOptions)

LZWInputStream

public LZWInputStream(InputStream in,
 boolean earlyChange)

Method Details

read

public int read()
         throws IOException

Overrides:

read in class FilterInputStream

Throws:

IOException

read

public int read(byte[] outputBytes,
 int offset,
 int byteCount)
         throws IOException

Overrides:

read in class FilterInputStream

Throws:

IOException

skip

public long skip(long n)
          throws IOException

Overrides:

skip in class FilterInputStream

Throws:

IOException

available

public int available()
              throws IOException

Overrides:

available in class FilterInputStream

Throws:

IOException

markSupported

public boolean markSupported()

Overrides:

markSupported in class FilterInputStream