ewe.io
Class CompressedRandomStream

java.lang.Object
  ewe.io.RandomStream
      ewe.io.CompressedRandomStream

public class CompressedRandomStream

extends RandomStream

A CompressedRandomStream is a read-only RandomStream that has been compressed for storage, but optimized for random access reading. This is unlike a stream that has been zipped where the entire stream is zipped into one entire zipped file. A CompressedRandomStream is compressed in blocks (of a size that you can select on creation) and a directory of the locations of each block is maintained, allowing for quick location and decompression of specific bytes within the file.

Any file may be converted to a CompressedRandomStream, using the static compressStream() methods or you can run the main() method of CompressedRandomStream to compress a File from the command line.

Field Summary

protected RandomStream	inputStream
static byte[]	signature These are the signature bytes of a CompressedRandomStream.

Fields inherited from class ewe.io.RandomStream

closed, noWritingAllowed, ras

Constructor Summary

CompressedRandomStream(RandomAccessStream compressedFile)
Create a CompressedRandomStream from a RandomAccessStream.

CompressedRandomStream(RandomStream compressedFile)
Create a CompressedRandomStream from a RandomStream.

Method Summary

boolean	canWrite()
void	close()
static boolean	compressStream(Handle handle, InputStream input, RandomStream out, int blockSize) Compress an InputStream into a CompressedRandomStream.
static boolean	compressStream(Handle handle, InputStream input, RandomStream out, int blockSize, int compressionLevel, long knownSize) Compress an InputStream into a CompressedRandomStream.
long	getCacheSize() Get the number of bytes to cache in memory.
static boolean	isCompressedRandomStream(File input) Check if a File has the CompressedRandomStream signature.
long	length()
static void	main(String[] args) This method can be used to convert a File into a CompressedRandomStream.
int	read() Reads the next byte of data from this input stream.
int	read(byte[] buffer, int start, int length) Read in a number of bytes of data from the input stream.
void	seek(long position)
void	setCacheSize(long cacheSize) Set the number of bytes to cache in memory.
long	tell()

Methods inherited from class ewe.io.RandomStream

available, cantWrite, checkClosed, flush, getFastStream, read, readSingleByteFromMultiByteRead, setLength, shutdown, skip, toInputStream, toOutputStream, toRandomAccessStream, toReadableStream, toWritableStream, write, write, write, writeSingleByteToMultiByteWrite

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, toString

Field Detail

signature

public static final byte[] signature

These are the signature bytes of a CompressedRandomStream.

inputStream

protected RandomStream inputStream

Constructor Detail

CompressedRandomStream

public CompressedRandomStream(RandomAccessStream compressedFile)
                       throws IOException

Create a CompressedRandomStream from a RandomAccessStream.

Parameters:

compressedFile - the compressed file.

Throws:

IOException - if there was an error reading the file.

CompressedRandomStream

public CompressedRandomStream(RandomStream compressedFile)
                       throws IOException

Create a CompressedRandomStream from a RandomStream.

Parameters:

compressedFile - the compressed file.

Throws:

IOException - if there was an error reading the file.

Method Detail

compressStream

public static boolean compressStream(Handle handle,
                                     InputStream input,
                                     RandomStream out,
                                     int blockSize)
                              throws IOException

Compress an InputStream into a CompressedRandomStream.

Parameters:

handle - an optional handle that can be used to abort the process.

input - the source stream.

out - an output RandomStream.

blockSize - the block size to use. A default of 1024 is used if this is zero.

Returns:

true if the operation completed, false if it was aborted because stop() was called on the Handle.

Throws:

IOException - if an IO error occured.

compressStream

public static boolean compressStream(Handle handle,
                                     InputStream input,
                                     RandomStream out,
                                     int blockSize,
                                     int compressionLevel,
                                     long knownSize)
                              throws IOException

Compress an InputStream into a CompressedRandomStream.

Parameters:

handle - an optional handle that can be used to abort the process.

input - the source stream.

out - an output RandomStream.

blockSize - the block size to use. A default of 1024 is used if this is zero.

compressionLevel - one of the ZipConstant.Z_xxx_COMPRESSION values, or zero for default.

knownSize - the size of the input stream if it is known, or -1 if it is not known.

Returns:

true if the operation completed, false if it was aborted because stop() was called on the Handle.

Throws:

IOException - if an IO error occured.

isCompressedRandomStream

public static boolean isCompressedRandomStream(File input)
                                        throws IOException

Check if a File has the CompressedRandomStream signature.

Parameters:

input - the input file.

Returns:

true if the file has the CompressedRandomStream signature.

Throws:

IOException - if there is an error reading from the file.

setCacheSize

public void setCacheSize(long cacheSize)

Set the number of bytes to cache in memory.

Parameters:

cacheSize - the number of bytes to cache in memory.

getCacheSize

public long getCacheSize()

Get the number of bytes to cache in memory.

main

public static void main(String[] args)
                 throws IOException,
                        InterruptedException

This method can be used to convert a File into a CompressedRandomStream.

use the command line:

        Ewe ewe.io.CompressedRandomStream input_file output_file [block_size]

The default block_size is 1024 bytes.

Throws:

IOException

InterruptedException

read

public int read(byte[] buffer,
                int start,
                int length)
         throws IOException

Description copied from class: RandomStream

Read in a number of bytes of data from the input stream.

Overrides:

read in class RandomStream

Parameters:

buffer - a destination buffer for the data.

start - The start offset in the destination buffer.

length - The 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:

IOException - if an I/O error occurs during reading.

read

public int read()
         throws IOException

Description copied from class: RandomStream

Reads the next byte of data from this 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.

Overrides:

read in class RandomStream

Returns:

the byte read or -1 on end of stream.

Throws:

IOException - if an I/O error occured.

close

public void close()
           throws IOException

Overrides:

close in class RandomStream

Throws:

IOException

seek

public void seek(long position)
          throws IOException

Overrides:

seek in class RandomStream

Throws:

IOException

tell

public long tell()
          throws IOException

Overrides:

tell in class RandomStream

Throws:

IOException

length

public long length()
            throws IOException

Overrides:

length in class RandomStream

Throws:

IOException

canWrite

public boolean canWrite()

Overrides:

canWrite in class RandomStream