java.nio

Class MappedByteBuffer

java.lang.Object

java.nio.Buffer

java.nio.ByteBuffer

java.nio.MappedByteBuffer

All Implemented Interfaces:

Comparable<ByteBuffer>

public abstract class MappedByteBuffer
extends ByteBuffer

MappedByteBuffer is a special kind of direct byte buffer which maps a region of file to memory.

MappedByteBuffer can be created by calling FileChannel.map. Once created, the mapping between the byte buffer and the file region remains valid until the byte buffer is garbage collected.

All or part of a MappedByteBuffer's content may change or become inaccessible at any time, since the mapped file region can be modified by another thread or process at any time. If this happens, the behavior of the MappedByteBuffer is undefined.

Method Summary

Modifier and Type	Method and Description
MappedByteBuffer	clear() Clears this buffer.
MappedByteBuffer	flip() Flips this buffer.
MappedByteBuffer	force() Flushes changes made to the in-memory buffer back to the mapped file.
boolean	isLoaded() Returns true if there is a high probability that every page of this buffer is currently loaded in RAM, meaning that accesses will not cause a page fault.
MappedByteBuffer	limit(int newLimit) Sets the limit of this buffer.
MappedByteBuffer	load() Attempts to load every page of this buffer into RAM.
MappedByteBuffer	mark() Marks the current position, so that the position may return to this point later by calling reset().
MappedByteBuffer	position(int newPosition) Sets the position of this buffer.
MappedByteBuffer	reset() Resets the position of this buffer to the mark.
MappedByteBuffer	rewind() Rewinds this buffer.

Methods inherited from class java.nio.ByteBuffer

allocate, allocateDirect, array, arrayOffset, asCharBuffer, asDoubleBuffer, asFloatBuffer, asIntBuffer, asLongBuffer, asReadOnlyBuffer, asShortBuffer, compact, compareTo, duplicate, equals, get, get, get, get, getChar, getChar, getDouble, getDouble, getFloat, getFloat, getInt, getInt, getLong, getLong, getShort, getShort, hasArray, hashCode, isAccessible, isDirect, mismatch, order, order, put, put, put, put, put, putChar, putChar, putDouble, putDouble, putFloat, putFloat, putInt, putInt, putLong, putLong, putShort, putShort, setAccessible, slice, wrap, wrap

Methods inherited from class java.nio.Buffer

capacity, getElementSizeShift, hasRemaining, isReadOnly, limit, position, remaining, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

isLoaded

public final boolean isLoaded()

Returns true if there is a high probability that every page of this buffer is currently loaded in RAM, meaning that accesses will not cause a page fault. It is impossible to give a strong guarantee since this is only a snapshot of a dynamic situation.

load

public final MappedByteBuffer load()

Attempts to load every page of this buffer into RAM. See isLoaded().

Returns:

this buffer.

force

public final MappedByteBuffer force()

Flushes changes made to the in-memory buffer back to the mapped file. Unless you call this, changes may not be written back until the finalizer runs. This method waits for the write to complete before returning.

Returns:

this buffer.

position

public final MappedByteBuffer position(int newPosition)

Sets the position of this buffer.

If the mark is set and it is greater than the new position, then it is cleared.

Overrides:

position in class ByteBuffer

Parameters:

newPosition - the new position, must be not negative and not greater than limit.

Returns:

this buffer.

limit

public final MappedByteBuffer limit(int newLimit)

Sets the limit of this buffer.

If the current position in the buffer is in excess of newLimit then, on returning from this call, it will have been adjusted to be equivalent to newLimit. If the mark is set and is greater than the new limit, then it is cleared.

Overrides:

limit in class ByteBuffer

Parameters:

newLimit - the new limit, must not be negative and not greater than capacity.

Returns:

this buffer.

mark

public final MappedByteBuffer mark()

Marks the current position, so that the position may return to this point later by calling reset().

Overrides:

mark in class ByteBuffer

Returns:

this buffer.

reset

public final MappedByteBuffer reset()

Resets the position of this buffer to the mark.

Overrides:

reset in class ByteBuffer

Returns:

this buffer.

clear

public final MappedByteBuffer clear()

Clears this buffer.

While the content of this buffer is not changed, the following internal changes take place: the current position is reset back to the start of the buffer, the value of the buffer limit is made equal to the capacity and mark is cleared.

Overrides:

clear in class ByteBuffer

Returns:

this buffer.

flip

public final MappedByteBuffer flip()

Flips this buffer.

The limit is set to the current position, then the position is set to zero, and the mark is cleared.

The content of this buffer is not changed.

Overrides:

flip in class ByteBuffer

Returns:

this buffer.

rewind

public final MappedByteBuffer rewind()

Rewinds this buffer.

The position is set to zero, and the mark is cleared. The content of this buffer is not changed.

Overrides:

rewind in class ByteBuffer

Returns:

this buffer.