net.freeutils.tnef

Class CompressedRTFInputStream

java.lang.Object

java.io.InputStream

net.freeutils.tnef.CompressedRTFInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public class CompressedRTFInputStream
extends java.io.InputStream

The CompressedRTFInputStream class provides decompression of compressed RTF data.

Since:

2009-10-12

Author:

Amichai Rothman

Field Summary

Fields

Modifier and Type	Field and Description
protected byte[]	buf
protected int	bufend
protected int	bufstart
protected static byte[]	COMPRESSED_RTF_PREBUF Prebuffered bytes used in RTF-compressed format.
protected int	compressedSize
protected int	crc
protected int	crc32
protected static int[]	CRC32_TABLE The lookup table used in the CRC32 calculation
protected byte[]	dict
protected static int	DICT_SIZE
protected int	dictstart
protected int	flagCount
protected int	flags
protected java.io.InputStream	in
protected int	magic
protected static int	MAGIC_COMPRESSED
protected static int	MAGIC_UNCOMPRESSED
protected int	out
protected int	uncompressedSize

Constructor Summary

Constructors

Constructor and Description
CompressedRTFInputStream(java.io.InputStream in) Constructs a new CompressedRTFInputStream which reads the compressed data from the given underlying stream.

Method Summary

Modifier and Type	Method and Description
int	available() Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream.
static int	calculateCRC32(byte[] buf, int off, int len) Calculates the CRC32 of the given bytes.
void	close() Closes this input stream and releases any system resources associated with the stream.
static byte[]	decompressRTF(byte[] src) Decompresses compressed-RTF data.
protected void	init() Initializes this stream by reading the compressed RTF header data.
protected boolean	more() Reads more data into the dictionary buffer.
protected boolean	moreCompressed() Reads (and decompresses) more compressed data into the dictionary buffer.
protected boolean	moreUncompressed() Reads more uncompressed data into the dictionary buffer.
int	read() Reads the next byte of data from the input stream.
int	read(byte[] b, int off, int len) Reads up to len bytes of data from the input stream into an array of bytes.

Methods inherited from class java.io.InputStream

mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

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

Field Detail

MAGIC_COMPRESSED

protected static final int MAGIC_COMPRESSED

See Also:

Constant Field Values

MAGIC_UNCOMPRESSED

protected static final int MAGIC_UNCOMPRESSED

See Also:

Constant Field Values

DICT_SIZE

protected static final int DICT_SIZE

See Also:

Constant Field Values

COMPRESSED_RTF_PREBUF

protected static byte[] COMPRESSED_RTF_PREBUF

Prebuffered bytes used in RTF-compressed format.

CRC32_TABLE

protected static int[] CRC32_TABLE

The lookup table used in the CRC32 calculation

in

protected final java.io.InputStream in

buf

protected final byte[] buf

dict

protected final byte[] dict

bufstart

protected int bufstart

bufend

protected int bufend

crc

protected int crc

out

protected int out

dictstart

protected int dictstart

flagCount

protected int flagCount

flags

protected int flags

compressedSize

protected int compressedSize

uncompressedSize

protected int uncompressedSize

magic

protected int magic

crc32

protected int crc32

Constructor Detail

CompressedRTFInputStream

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

Constructs a new CompressedRTFInputStream which reads the compressed data from the given underlying stream.

Parameters:

in - the stream containing the compressed data

Throws:

java.io.IOException - if an error occurs

Method Detail

calculateCRC32

public static int calculateCRC32(byte[] buf,
                                 int off,
                                 int len)

Calculates the CRC32 of the given bytes. The CRC32 calculation is similar to the standard one as demonstrated in RFC 1952, but with the inversion (before and after the calculation) omitted.

Parameters:

buf - the byte array to calculate CRC32 on

off - the offset of buf at which the CRC32 calculation will start

len - the number of bytes on which to calculate the CRC32

Returns:

the CRC32 value

decompressRTF

public static byte[] decompressRTF(byte[] src)

Decompresses compressed-RTF data.

This standalone method decompresses the data using a somewhat different algorithm than this stream's algorithm. It trades memory footprint (twice the size of the entire output is kept in memory) for speed (an order of magnitude faster than the stream version).

It also serves as a concise reference implementation for the decompression algorithm.

Parameters:

src - the compressed-RTF data bytes

Returns:

an array containing the decompressed bytes

Throws:

java.lang.IllegalArgumentException - if src does not contain valid compressed-RTF bytes

init

protected void init()
             throws java.io.IOException

Initializes this stream by reading the compressed RTF header data.

Throws:

java.io.IOException - if an error occurs

moreCompressed

protected boolean moreCompressed()
                          throws java.io.IOException

Reads (and decompresses) more compressed data into the dictionary buffer.

Returns:

true if more data was read, false if there is no more data available

Throws:

java.io.IOException - if an error occurs

moreUncompressed

protected boolean moreUncompressed()
                            throws java.io.IOException

Reads more uncompressed data into the dictionary buffer.

Returns:

true if more data was read, false if there is no more data available

Throws:

java.io.IOException - if an error occurs

more

protected boolean more()
                throws java.io.IOException

Reads more data into the dictionary buffer.

Returns:

true if more data was read, false if there is no more data available

Throws:

java.io.IOException - if an error occurs

available

public int available()
              throws java.io.IOException

Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking by the next invocation of a method for this input stream.

Overrides:

available in class java.io.InputStream

Returns:

an estimate of the number of bytes that can be read (or skipped over) from this input stream without blocking or 0 when it reaches the end of the input stream.

Throws:

java.io.IOException - if an error occurs

close

public void close()
           throws java.io.IOException

Closes this input stream and releases any system resources associated with the stream.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Overrides:

close in class java.io.InputStream

Throws:

java.io.IOException - if an error occurs

read

public int read()
         throws java.io.IOException

Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

Specified by:

read in class java.io.InputStream

Returns:

the next byte of data, or -1 if the end of the stream is reached

Throws:

java.io.IOException - if an error occurs

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException

Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of file is detected, or an exception is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

Overrides:

read in class java.io.InputStream

Parameters:

b - the buffer into which the data is read

off - the start offset in array b at which the data is written

len - the maximum number of bytes to read

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached

Throws:

java.io.IOException - If the first byte cannot be read for any reason other than end of file, or if the input stream has been closed, or if some other I/O error occurs

java.lang.NullPointerException - If b is null

java.lang.IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off