com.sun.labs.minion.util.buffer
Class ChannelReadableBuffer

java.lang.Object
  com.sun.labs.minion.util.buffer.StdReadableImpl
      com.sun.labs.minion.util.buffer.ChannelReadableBuffer

All Implemented Interfaces:

Buffer, ReadableBuffer

public class ChannelReadableBuffer
extends StdReadableImpl

A readable buffer that's backed by a channel and an in-memory buffer.

Field Summary

protected long	be The offset in the file of the end of the buffer that we represent.
protected long	bs The offset in the file of the buffer that we represent.
protected java.nio.ByteBuffer	buff The in-memory buffer.
protected java.nio.channels.FileChannel	chan The channel containing the buffer.
protected static int	DEFAULT_BUFF_SIZE The default buffer size, 1KB.
protected static java.lang.String	logTag A tag for our log entries.
protected long	me The offset in the file of the end of our in-memory buffer.
protected long	ms The offset in the file of the start of our in-memory buffer.
protected long	pos The offset of the current position in the buffer we're representing.

Constructor Summary

ChannelReadableBuffer(java.nio.channels.FileChannel chan, long offset, int limit, int buffSize)
Creates a buffer backed by a channel.

ChannelReadableBuffer(java.io.RandomAccessFile raf, long offset, int limit)
Creates a buffer backed by a channel.

ChannelReadableBuffer(java.io.RandomAccessFile raf, long offset, int limit, int buffSize)
Creates a buffer backed by a channel.

Method Summary

protected int	checkBounds(long p) Checks whether the given position is within the bounds of our in memory buffer.
ReadableBuffer	duplicate() Duplicates this buffer, so that it can be used safely by other readers.
byte	get() Gets the next byte in the buffer.
byte	get(int i) Gets the byte at the given position in the buffer.
int	limit() Gets the limit of this buffer, i.e., the last readable position.
void	limit(int l) Sets the limit of this buffer, i.e., the last readable position.
int	position() Gets the position of the buffer.
void	position(int i) Positions the buffer.
protected int	read(long off) Reads a given number of bytes from the channel.
int	remaining() Gets the number of bytes remaining to be read.
ReadableBuffer	slice(int p, int s) Slices this buffer so that a sub-buffer can be used.
java.lang.String	toString() Gets a string representation of the buffer.

Methods inherited from class com.sun.labs.minion.util.buffer.StdReadableImpl

byteDecode, byteDecode, byteDecode, byteDecodeLong, byteDecodeLong, byteDecodeLong, countBits, decodeFloat, getString, skipByteEncoded, test, toString, toString

Methods inherited from class java.lang.Object

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

Field Detail

chan

protected java.nio.channels.FileChannel chan

The channel containing the buffer.

ms

protected long ms

The offset in the file of the start of our in-memory buffer.

me

protected long me

The offset in the file of the end of our in-memory buffer.

bs

protected long bs

The offset in the file of the buffer that we represent.

be

protected long be

The offset in the file of the end of the buffer that we represent.

pos

protected long pos

The offset of the current position in the buffer we're representing.

buff

protected java.nio.ByteBuffer buff

The in-memory buffer.

logTag

protected static java.lang.String logTag

A tag for our log entries.

DEFAULT_BUFF_SIZE

protected static final int DEFAULT_BUFF_SIZE

The default buffer size, 1KB.

See Also:

Constant Field Values

Constructor Detail

ChannelReadableBuffer

public ChannelReadableBuffer(java.io.RandomAccessFile raf,
                             long offset,
                             int limit)

Creates a buffer backed by a channel.

Parameters:

raf - The file that will provide the channel backing this buffer.

offset - The offset in the file where our buffer is located.

limit - The number of bytes in our buffer.

ChannelReadableBuffer

public ChannelReadableBuffer(java.io.RandomAccessFile raf,
                             long offset,
                             int limit,
                             int buffSize)

Creates a buffer backed by a channel.

Parameters:

buffSize - The size of the in-memory buffer to use.

raf - The file that will provide the channel backing this buffer.

offset - The offset in the file where our buffer is located.

limit - The number of bytes in our buffer.

ChannelReadableBuffer

public ChannelReadableBuffer(java.nio.channels.FileChannel chan,
                             long offset,
                             int limit,
                             int buffSize)

Creates a buffer backed by a channel.

Parameters:

chan - The channel backing our buffer.

buffSize - The size of the in-memory buffer to use.

offset - The offset in the file where our buffer is located.

limit - The number of bytes in our buffer.

Method Detail

read

protected int read(long off)

Reads a given number of bytes from the channel.

Parameters:

off - The offset in the file from which the bytes should be read.

Returns:

The number of bytes actually read.

checkBounds

protected int checkBounds(long p)

Checks whether the given position is within the bounds of our in memory buffer. If it's not, data will be read into the in-memory buffer.

Parameters:

p - The position that we want to check

Returns:

The index in the in-memory buffer that can be read for this position.

remaining

public int remaining()

Gets the number of bytes remaining to be read.

Returns:

The number of bytes remaining to be read.

duplicate

public ReadableBuffer duplicate()

Duplicates this buffer, so that it can be used safely by other readers. Note that this duplicates the data in the buffer, since it must not be changed by subsequent reads.

Returns:

A new buffer that is backed by the same channel. The in-memory buffer and position are independent in the new buffer.

slice

public ReadableBuffer slice(int p,
                            int s)

Slices this buffer so that a sub-buffer can be used. The buffer is sliced from the current position. Note that this actually duplicates the data in the buffer, since it must not be changed by subsequent reads.

Parameters:

p - The position at which the buffer should be sliced.

s - The number of bytes that should be in the sliced buffer.

Returns:

A new buffer backed by the same channel. The first position in the new buffer will be the given position and the new buffer will contain the given number of bytes.

limit

public int limit()

Gets the limit of this buffer, i.e., the last readable position.

Returns:

The last readable position in the buffer.

limit

public void limit(int l)

Sets the limit of this buffer, i.e., the last readable position.

Parameters:

l - The limit to set.

get

public byte get(int i)

Gets the byte at the given position in the buffer.

Parameters:

i - The position from which we want to get a byte.

Returns:

The byte at the given position.

get

public byte get()

Gets the next byte in the buffer.

Returns:

Gets the byte at the current position and advances the current position.

position

public int position()

Gets the position of the buffer.

Returns:

The current position of the buffer.

position

public void position(int i)

Positions the buffer.

Parameters:

i - The position to which we want to set the buffer.

toString

public java.lang.String toString()

Gets a string representation of the buffer.

Overrides:

toString in class StdReadableImpl

Returns:

A string representation of the buffer.