org.simpleframework.util.buffer
Class FileAllocator

java.lang.Object
  org.simpleframework.util.buffer.FileAllocator

All Implemented Interfaces:

Closeable, Allocator

public class FileAllocator
extends Object
implements Allocator

The FileAllocator object is used to create buffers that can be written to the file system. This creates buffers as files if they are larger than the specified limit. This ensures that buffers of arbitrary large size can be created. All buffer sizes under the limit are created using byte arrays allocated on the executing VM heap. This ensures that optimal performance is maintained for buffers of reasonable size.

Author:

Niall Gallagher

Constructor Summary

FileAllocator()
Constructor for the FileAllocator object.

FileAllocator(int limit)
Constructor for the FileAllocator object.

FileAllocator(String prefix)
Constructor for the FileAllocator object.

FileAllocator(String prefix, int limit)
Constructor for the FileAllocator object.

Method Summary

Buffer	allocate() This will allocate a file buffer which will write data for the buffer to a file.
Buffer	allocate(long size) This will allocate a file buffer which will write data for the buffer to a file.
void	close() This method is used to close the allocator so that resources that are occupied by the allocator can be freed.

Methods inherited from class java.lang.Object

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

Constructor Detail

FileAllocator

public FileAllocator()

Constructor for the FileAllocator object. This is used to create buffers in memory up to a threshold size. If a buffer is required over the threshold size then the data is written to a file, where it can be retrieved at a later point.

FileAllocator

public FileAllocator(int limit)

Constructor for the FileAllocator object. This is used to create buffers in memory up to a threshold size. If a buffer is required over the threshold size then the data is written to a file, where it can be retrieved at a later point.

Parameters:

limit - this is the maximum size for a heap buffer

FileAllocator

public FileAllocator(String prefix)

Constructor for the FileAllocator object. This is used to create buffers in memory up to a threshold size. If a buffer is required over the threshold size then the data is written to a file, where it can be retrieved at a later point.

Parameters:

prefix - this is the file prefix for the file buffers

FileAllocator

public FileAllocator(String prefix,
                     int limit)

Constructor for the FileAllocator object. This is used to create buffers in memory up to a threshold size. If a buffer is required over the threshold size then the data is written to a file, where it can be retrieved at a later point.

Parameters:

prefix - this is the file prefix for the file buffers

limit - this is the maximum size for a heap buffer

Method Detail

allocate

public Buffer allocate()
                throws IOException

This will allocate a file buffer which will write data for the buffer to a file. Buffers allocated by this method can be of arbitrary size as data is appended directly to a temporary file. This ensures there is no upper limit for appended data.

Specified by:

allocate in interface Allocator

Returns:

a buffer which will write to a temporary file

Throws:

IOException

allocate

public Buffer allocate(long size)
                throws IOException

This will allocate a file buffer which will write data for the buffer to a file. Buffers allocated by this method can be of arbitrary size as data is appended directly to a temporary file. This ensures there is no upper limit for appended data. If the size required is less than the limit then the buffer is an in memory array which provides optimal performance.

Specified by:

allocate in interface Allocator

Parameters:

size - this is the size of the buffer to be created

Returns:

a buffer which will write to a created temporary file

Throws:

IOException

close

public void close()
           throws IOException

This method is used to close the allocator so that resources that are occupied by the allocator can be freed. This will allow the allocator to be created and closed repeatedly in a single process without holding on to resources such as mapped file buffers or threads.

Specified by:

close in interface Closeable

Specified by:

close in interface Allocator

Throws:

IOException