loci.common

Class NIOByteBufferProvider

java.lang.Object

loci.common.NIOByteBufferProvider

public class NIOByteBufferProvider
extends Object

Provides a facade to byte buffer allocation that enables FileChannel.map() usage on platforms where it's unlikely to give us problems and heap allocation where it is. References:

• http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5092131
• http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6417205

Author:

Chris Allan

Field Summary

Fields

Modifier and Type	Field and Description
private FileChannel	channel File channel to allocate or map data from.
private static org.slf4j.Logger	LOGGER Logger for this class.
private FileChannel.MapMode	mapMode If we are to use memory mapped I/O, the map mode.
static int	MINIMUM_JAVA_VERSION The minimum Java version we know is safe for memory mapped I/O.
private static boolean	useMappedByteBuffer Whether or not we are to use memory mapped I/O.

Constructor Summary

Constructors

Constructor and Description
NIOByteBufferProvider(FileChannel channel, FileChannel.MapMode mapMode) Default constructor.

Method Summary

Methods

Modifier and Type	Method and Description
ByteBuffer	allocate(long bufferStartPosition, int newSize) Allocates or maps the desired file data into memory.
protected ByteBuffer	allocateDirect(long bufferStartPosition, int newSize) Allocates memory and copies the desired file data into it.
protected ByteBuffer	allocateMappedByteBuffer(long bufferStartPosition, int newSize) Memory maps the desired file data into memory.

Methods inherited from class java.lang.Object

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

Field Detail

MINIMUM_JAVA_VERSION

public static final int MINIMUM_JAVA_VERSION

The minimum Java version we know is safe for memory mapped I/O.

See Also:

Constant Field Values

LOGGER

private static final org.slf4j.Logger LOGGER

Logger for this class.

useMappedByteBuffer

private static boolean useMappedByteBuffer

Whether or not we are to use memory mapped I/O.

channel

private FileChannel channel

File channel to allocate or map data from.

mapMode

private FileChannel.MapMode mapMode

If we are to use memory mapped I/O, the map mode.

Constructor Detail

NIOByteBufferProvider

public NIOByteBufferProvider(FileChannel channel,
                     FileChannel.MapMode mapMode)

Default constructor.

Parameters:

channel - File channel to allocate or map byte buffers from.

mapMode - The map mode. Required but only used if memory mapped I/O is to occur.

Method Detail

allocate

public ByteBuffer allocate(long bufferStartPosition,
                  int newSize)
                    throws IOException

Allocates or maps the desired file data into memory.

Parameters:

bufferStartPosition - The absolute position of the start of the buffer.

newSize - The buffer size.

Returns:

A newly allocated or mapped NIO byte buffer.

Throws:

IOException - If there is an issue mapping, aligning or allocating the buffer.

allocateDirect

protected ByteBuffer allocateDirect(long bufferStartPosition,
                        int newSize)
                             throws IOException

Allocates memory and copies the desired file data into it.

Parameters:

bufferStartPosition - The absolute position of the start of the buffer.

newSize - The buffer size.

Returns:

A newly allocated NIO byte buffer.

Throws:

IOException - If there is an issue aligning or allocating the buffer.

allocateMappedByteBuffer

protected ByteBuffer allocateMappedByteBuffer(long bufferStartPosition,
                                  int newSize)
                                       throws IOException

Memory maps the desired file data into memory.

Parameters:

bufferStartPosition - The absolute position of the start of the buffer.

newSize - The buffer size.

Returns:

A newly mapped NIO byte buffer.

Throws:

IOException - If there is an issue mapping, aligning or allocating the buffer.