org.terrier.compression
Class BitFileInMemory

java.lang.Object
  org.terrier.compression.BitFileInMemory

All Implemented Interfaces:

java.io.Closeable, BitInSeekable

public class BitFileInMemory
extends java.lang.Object
implements BitInSeekable

Class which enables a bit compressed file to be read wholly into memory and accessed from there with low latency. This file cannot handle files larger than Integer.MAX_VALUE (2GB)

Author:

Craig Macdonald

Field Summary

protected byte[]	inBuffer buffer in memory for the entire compressed file
protected static org.apache.log4j.Logger	logger The logger used

Constructor Summary

BitFileInMemory(byte[] buffer)
Create an object using the specified data as the compressed data

BitFileInMemory(java.io.InputStream is, long length)
Loads the entire specified inputstream into memory.

BitFileInMemory(java.lang.String filename)
Loads the entire file represented by filename into memory

Method Summary

void	close() Close this object.
BitIn	readReset(long startByteOffset, byte startBitOffset) Reads from the file a specific number of bytes and after this call, a sequence of read calls may follow.
BitIn	readReset(long startByteOffset, byte startBitOffset, long endByteOffset, byte endBitOffset) Reads from the file a specific number of bytes and after this call, a sequence of read calls may follow.

Methods inherited from class java.lang.Object

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

Field Detail

logger

protected static final org.apache.log4j.Logger logger

The logger used

inBuffer

protected final byte[] inBuffer

buffer in memory for the entire compressed file

Constructor Detail

BitFileInMemory

public BitFileInMemory(java.lang.String filename)
                throws java.io.IOException

Loads the entire file represented by filename into memory

Parameters:

filename - Location of bit file to read into memory

Throws:

java.io.IOException - if anything goes wrong reading the file

BitFileInMemory

public BitFileInMemory(java.io.InputStream is,
                       long length)
                throws java.io.IOException

Loads the entire specified inputstream into memory. Length is assumed to be as specified.

Parameters:

is - InputStream containing the compressed bitfile

length - Expected length of the input stream

Throws:

java.io.IOException - if anything goes wrong reading the inputstream

BitFileInMemory

public BitFileInMemory(byte[] buffer)

Create an object using the specified data as the compressed data

Method Detail

readReset

public BitIn readReset(long startByteOffset,
                       byte startBitOffset,
                       long endByteOffset,
                       byte endBitOffset)

Reads from the file a specific number of bytes and after this call, a sequence of read calls may follow. The offsets given as arguments are inclusive. For example, if we call this method with arguments 0, 2, 1, 7, it will read in a buffer the contents of the underlying file from the third bit of the first byte to the last bit of the second byte.

Specified by:

readReset in interface BitInSeekable

Parameters:

startByteOffset - the starting byte to read from

startBitOffset - the bit offset in the starting byte

endByteOffset - the ending byte

endBitOffset - the bit offset in the ending byte. This bit is the last bit of this entry.

Returns:

Returns the BitIn object to use to read that data

readReset

public BitIn readReset(long startByteOffset,
                       byte startBitOffset)

Reads from the file a specific number of bytes and after this call, a sequence of read calls may follow. The offsets given as arguments are inclusive. For example, if we call this method with arguments 0, 2, 1, 7, it will read in a buffer the contents of the underlying file from the third bit of the first byte to the last bit of the second byte.

Specified by:

readReset in interface BitInSeekable

Parameters:

startByteOffset - the starting byte to read from

startBitOffset - the bit offset in the starting byte

Returns:

Returns the BitIn object to use to read that data

close

public void close()

Close this object. Does nothing.

Specified by:

close in interface java.io.Closeable