fiftyone.mobile.detection.readers
Class TrieReader

java.lang.Object
  fiftyone.mobile.detection.readers.TrieReader

public class TrieReader
extends Object

Due to the size of the Trie tree structure, the data cannot fit into a single ByteBuffer. Therefore, this class is used to wrap the file channel and and become logically one channel.

Nested Class Summary

private static class

TrieReader.DataType Defines what data type is being read from a given buffer.

Field Summary

private int	_bufferIndex The index of the buffer that _position is pointed at.
private ArrayList<MappedByteBuffer>	_buffers Buffers mapped to the files channel.
private long	_globalPosition
private long	_position Logical position of the data needed in the file.
private long	_start The start position of the tree in the trie file.
private FileChannel	_triFile The File Channel linked to the trie data.

Constructor Summary

TrieReader(FileChannel reader)
Creates the class by creating multiple ByteBuffers that can be read from.

Method Summary

void	close() Clears the ByteBuffers and closes the File Channel.
private byte	getNextByte() Gets the MappedByteBuffer for that this class is currently positioned on, automatically incrementing position and changing buffer if required.
long	getPos() Returns the current logical position value.
private byte[]	getValue(TrieReader.DataType dataType) Reads a certain data type from the file e.g.
byte	readByte()
byte[]	readBytes(int length)
int	readInt() Read an signed integer from the file at the current location.
long	readLong() Read an signed long from the file at the current location.
long	readLong(long position) Read an signed long from the file at a specified location.
short	readUByte() Read an Unsigned byte from the file at the current location.
short	readUByte(long position) Read an Unsigned byte from the file at a specified location.
long	readUInt() Read an Unsigned integer from the file at the current location.
int	readUShort() Read an Unsigned short from the file at the current location.
int	readUShort(long position) Read an Unsigned short from the file at a specified location.
void	setPos(long position) Sets the logical position in the file.

Methods inherited from class java.lang.Object

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

Field Detail

_buffers

private ArrayList<MappedByteBuffer> _buffers

Buffers mapped to the files channel.

_triFile

private final FileChannel _triFile

The File Channel linked to the trie data.

_start

private final long _start

The start position of the tree in the trie file.

_position

private long _position

Logical position of the data needed in the file.

_bufferIndex

private int _bufferIndex

The index of the buffer that _position is pointed at.

_globalPosition

private long _globalPosition

Constructor Detail

TrieReader

public TrieReader(FileChannel reader)
           throws IOException

Creates the class by creating multiple ByteBuffers that can be read from.

Parameters:

reader - File channel to read from.

Throws:

IOException

Method Detail

getPos

public long getPos()

Returns the current logical position value.

Returns:

the current logical position in the file.

setPos

public void setPos(long position)

Sets the logical position in the file.

Parameters:

position - position value.

readUByte

public short readUByte()

Read an Unsigned byte from the file at the current location.

Returns:

The value read.

readUByte

public short readUByte(long position)

Read an Unsigned byte from the file at a specified location.

Parameters:

position - Position to read from.

Returns:

The value read.

readUShort

public int readUShort()

Read an Unsigned short from the file at the current location.

Returns:

The value read.

readUShort

public int readUShort(long position)

Read an Unsigned short from the file at a specified location.

Parameters:

position - Position to read from.

Returns:

The value read.

readUInt

public long readUInt()
              throws IOException

Read an Unsigned integer from the file at the current location.

Returns:

The Value read.

Throws:

IOException

readInt

public int readInt()
            throws IOException

Read an signed integer from the file at the current location.

Returns:

The Value read.

Throws:

IOException

readLong

public long readLong()

Read an signed long from the file at the current location.

Returns:

The Value read.

Throws:

IOException

readLong

public long readLong(long position)
              throws IOException

Read an signed long from the file at a specified location.

Parameters:

position - Position to read from.

Returns:

The value read.

Throws:

IOException

getNextByte

private byte getNextByte()

Gets the MappedByteBuffer for that this class is currently positioned on, automatically incrementing position and changing buffer if required.

readByte

public byte readByte()

readBytes

public byte[] readBytes(int length)

getValue

private byte[] getValue(TrieReader.DataType dataType)

Reads a certain data type from the file e.g. byte, Unsigned Integer etc.

Parameters:

dataType - Type of data to read.

Returns:

byte array of data.

close

public void close()
           throws IOException

Clears the ByteBuffers and closes the File Channel.

Throws:

IOException