org.jboss.netty.channel

Interface FileRegion

All Superinterfaces:

ExternalResourceReleasable

All Known Implementing Classes:

DefaultFileRegion

public interface FileRegion
extends ExternalResourceReleasable

A region of a file that is sent via a Channel which supports zero-copy file transfer.

Upgrade your JDK / JRE

FileChannel.transferTo(long, long, WritableByteChannel) has at least four known bugs in the old versions of Sun JDK and perhaps its derived ones. Please upgrade your JDK to 1.6.0_18 or later version if you are going to use zero-copy file transfer.

• 5103988 - FileChannel.transferTo() should return -1 for EAGAIN instead throws IOException
• 6253145 - FileChannel.transferTo() on Linux fails when going beyond 2GB boundary
• 6427312 - FileChannel.transferTo() throws IOException "system call interrupted"
• 6470086 - FileChannel.transferTo(2147483647, 1, channel) causes "Value too large" exception

Check your operating system and JDK / JRE

If your operating system (or JDK / JRE) does not support zero-copy file transfer, sending a file with FileRegion might fail or yield worse performance. For example, sending a large file doesn't work well in Windows.

Not all transports support it

Currently, the NIO transport is the only transport that supports FileRegion. Attempting to write a FileRegion to non-NIO Channel will trigger a ClassCastException or a similar exception.

Method Summary

Modifier and Type	Method and Description
long	getCount() Returns the number of bytes to transfer.
long	getPosition() Returns the offset in the file where the transfer began.
long	transferTo(java.nio.channels.WritableByteChannel target, long position) Transfers the content of this file region to the specified channel.

Methods inherited from interface org.jboss.netty.util.ExternalResourceReleasable

releaseExternalResources

Method Detail

getPosition

long getPosition()

Returns the offset in the file where the transfer began.

getCount

long getCount()

Returns the number of bytes to transfer.

transferTo

long transferTo(java.nio.channels.WritableByteChannel target,
                long position)
         throws java.io.IOException

Transfers the content of this file region to the specified channel.

Parameters:

target - the destination of the transfer

position - the relative offset of the file where the transfer begins from. For example, 0 will make the transfer start from getPosition()th byte and getCount() - 1 will make the last byte of the region transferred.

Throws:

java.io.IOException