decaf::nio::Buffer Class Reference

A container for data of a specific primitive type. More...

#include <src/main/decaf/nio/Buffer.h>

Inheritance diagram for decaf::nio::Buffer:

Public Member Functions
	Buffer (int capactiy)
	Buffer (const Buffer &other)
virtual	~Buffer ()
virtual int	capacity () const
virtual int	position () const
virtual Buffer &	position (int newPosition)
	Sets this buffer's position.
virtual int	limit () const
virtual Buffer &	limit (int newLimit)
	Sets this buffer's limit.
virtual Buffer &	mark ()
	Sets this buffer's mark at its position.
virtual Buffer &	reset ()
	Resets this buffer's position to the previously-marked position.
virtual Buffer &	clear ()
	Clears this buffer.
virtual Buffer &	flip ()
	Flips this buffer.
virtual Buffer &	rewind ()
	Rewinds this buffer.
virtual int	remaining () const
	Returns the number of elements between the current position and the limit.
virtual bool	hasRemaining () const
	Tells whether there are any elements between the current position and the limit.
virtual bool	isReadOnly () const =0
	Tells whether or not this buffer is read-only.

Protected Attributes
int	_position
int	_capacity
int	_limit
int	_mark
bool	_markSet

Detailed Description

A container for data of a specific primitive type.

A buffer is a linear, finite sequence of elements of a specific primitive type. Aside from its content, the essential properties of a buffer are its capacity, limit, and position:

A buffer's capacity is the number of elements it contains. The capacity of a buffer is never negative and never changes.

A buffer's limit is the index of the first element that should not be read or written. A buffer's limit is never negative and is never greater than its capacity.

A buffer's position is the index of the next element to be read or written. A buffer's position is never negative and is never greater than its limit.

There is one subclass of this class for each non-boolean primitive type.

Transferring data: Each subclass of this class defines two categories of get and put operations:

• Relative operations read or write one or more elements starting at the current position and then increment the position by the number of elements transferred. If the requested transfer exceeds the limit then a relative get operation throws a BufferUnderflowException and a relative put operation throws a BufferOverflowException; in either case, no data is transferred.
• Absolute operations take an explicit element index and do not affect the position. Absolute get and put operations throw an IndexOutOfBoundsException if the index argument exceeds the limit.

Data may also, of course, be transferred in to or out of a buffer by the I/O operations of an appropriate channel, which are always relative to the current position.

Marking and resetting:

A buffer's mark is the index to which its position will be reset when the reset method is invoked. The mark is not always defined, but when it is defined it is never negative and is never greater than the position. If the mark is defined then it is discarded when the position or the limit is adjusted to a value smaller than the mark. If the mark is not defined then invoking the reset method causes an InvalidMarkException to be thrown.

Invariants:

The following invariant holds for the mark, position, limit, and capacity values: 0 <= mark <= position <= limit <= capacity

A newly-created buffer always has a position of zero and a mark that is undefined. The initial limit may be zero, or it may be some other value that depends upon the type of the buffer and the manner in which it is constructed. The initial content of a buffer is, in general, undefined.

Clearing, flipping, and rewinding:

In addition to methods for accessing the position, limit, and capacity values and for marking and resetting, this class also defines the following operations upon buffers:

clear() makes a buffer ready for a new sequence of channel-read or relative put operations: It sets the limit to the capacity and the position to zero.

flip() makes a buffer ready for a new sequence of channel-write or relative get operations: It sets the limit to the current position and then sets the position to zero.

rewind() makes a buffer ready for re-reading the data that it already contains: It leaves the limit unchanged and sets the position to zero.

Read-only buffers:

Every buffer is readable, but not every buffer is writable. The mutation methods of each buffer class are specified as optional operations that will throw a ReadOnlyBufferException when invoked upon a read-only buffer. A read-only buffer does not allow its content to be changed, but its mark, position, and limit values are mutable. Whether or not a buffer is read-only may be determined by invoking its isReadOnly method.

Thread safety:

Buffers are not safe for use by multiple concurrent threads. If a buffer is to be used by more than one thread then access to the buffer should be controlled by appropriate synchronization.

Invocation chaining:

Methods in this class that do not otherwise have a value to return are specified to return the buffer upon which they are invoked. This allows method invocations to be chained; for example, the sequence of statements

b.flip(); b.position(23); b.limit(42);

can be replaced by the single, more compact statement b.flip().position(23).limit(42);

Constructor & Destructor Documentation

decaf::nio::Buffer::Buffer

(

int

capactiy

)

decaf::nio::Buffer::Buffer

(

const Buffer &

other

)

virtual decaf::nio::Buffer::~Buffer ( )

inlinevirtual

Member Function Documentation

virtual int decaf::nio::Buffer::capacity ( ) const

inlinevirtual

Returns

this buffer's capacity.

virtual Buffer& decaf::nio::Buffer::clear ( )

virtual

Clears this buffer.

The position is set to zero, the limit is set to the capacity, and the mark is discarded.

Invoke this method before using a sequence of channel-read or put operations to fill this buffer. For example:

buf.clear(); // Prepare buffer for reading in.read(buf); // Read data

This method does not actually erase the data in the buffer, but it is named as if it did because it will most often be used in situations in which that might as well be the case.

Returns

a reference to this buffer.

virtual Buffer& decaf::nio::Buffer::flip ( )

virtual

Flips this buffer.

The limit is set to the current position and then the position is set to zero. If the mark is defined then it is discarded.

After a sequence of channel-read or put operations, invoke this method to prepare for a sequence of channel-write or relative get operations. For example:

buf.put(magic);    // Prepend header
in.read(buf);      // Read data into rest of buffer
buf.flip();        // Flip buffer
out.write(buf);    // Write header + data to channel

This method is often used in conjunction with the compact method when transferring data from one place to another.

Returns

a reference to this buffer.

virtual bool decaf::nio::Buffer::hasRemaining ( ) const

inlinevirtual

Tells whether there are any elements between the current position and the limit.

Returns

true if, and only if, there is at least one element remaining in this buffer.

virtual bool decaf::nio::Buffer::isReadOnly ( ) const

pure virtual

Tells whether or not this buffer is read-only.

Returns

true if, and only if, this buffer is read-only.

Implemented in decaf::nio::ByteBuffer, decaf::internal::nio::ByteArrayBuffer, decaf::internal::nio::CharArrayBuffer, decaf::internal::nio::DoubleArrayBuffer, decaf::internal::nio::FloatArrayBuffer, decaf::internal::nio::IntArrayBuffer, decaf::internal::nio::LongArrayBuffer, and decaf::internal::nio::ShortArrayBuffer.

virtual int decaf::nio::Buffer::limit ( ) const

inlinevirtual

Returns

this buffers Limit

virtual Buffer& decaf::nio::Buffer::limit ( int  newLimit )

virtual

Sets this buffer's limit.

If the position is larger than the new limit then it is set to the new limit. If the mark is defined and larger than the new limit then it is discarded.

Parameters

newLimit

The new limit value; must be no larger than this buffer's capacity.

Returns

A reference to This buffer

Exceptions

IllegalArgumentException

if preconditions on the new pos don't hold.

virtual Buffer& decaf::nio::Buffer::mark ( )

virtual

Sets this buffer's mark at its position.

Returns

a reference to this buffer.

virtual int decaf::nio::Buffer::position ( ) const

inlinevirtual

Returns

the current position in the buffer

virtual Buffer& decaf::nio::Buffer::position ( int  newPosition )

virtual

Sets this buffer's position.

If the mark is defined and larger than the new position then it is discarded.

Parameters

newPosition

The new postion in the buffer to set.

Returns

a reference to This buffer.

Exceptions

IllegalArgumentException

if preconditions on the new pos don't hold.

virtual int decaf::nio::Buffer::remaining ( ) const

inlinevirtual

Returns the number of elements between the current position and the limit.

Returns

The number of elements remaining in this buffer

virtual Buffer& decaf::nio::Buffer::reset ( )

virtual

Resets this buffer's position to the previously-marked position.

Returns

a reference to this buffer.

Exceptions

InvalidMarkException

- If the mark has not been set

virtual Buffer& decaf::nio::Buffer::rewind ( )

virtual

Rewinds this buffer.

The position is set to zero and the mark is discarded.

Invoke this method before a sequence of channel-write or get operations, assuming that the limit has already been set appropriately. For example:

out.write(buf); // Write remaining data buf.rewind(); // Rewind buffer buf.get(array); // Copy data into array

Returns

a reference to this buffer.

Field Documentation

int decaf::nio::Buffer::_capacity

protected

int decaf::nio::Buffer::_limit

protected

int decaf::nio::Buffer::_mark

protected

bool decaf::nio::Buffer::_markSet

protected

int decaf::nio::Buffer::_position

mutableprotected

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The documentation for this class was generated from the following file:

• src/main/decaf/nio/Buffer.h