BMemoryIO Class Reference

A BPositionIO derived class that works on memory buffers. More...

Inherits BPositionIO.

Public Member Functions
	BMemoryIO (const void *data, size_t length)
	Create a read-only object.
	BMemoryIO (void *data, size_t length)
	Create a read/write object.
virtual	~BMemoryIO ()
	The destructor does nothing.
virtual off_t	Position () const
	Return the current position.
virtual ssize_t	ReadAt (off_t position, void *buffer, size_t size)
	Read from a given position.
virtual off_t	Seek (off_t position, uint32 seekMode)
	Move the cursor to a given position.
virtual status_t	SetSize (off_t size)
	Resize the buffer.
virtual ssize_t	WriteAt (off_t position, const void *buffer, size_t size)
	Write at a given position.
Public Member Functions inherited from BPositionIO
	BPositionIO ()
	This constructor does nothing.
virtual	~BPositionIO ()
	This destructor does nothing.
virtual status_t	GetSize (off_t *size) const
	Get the size of the object or data.
virtual off_t	Position () const =0
	Pure virtual to return the current position of the cursor.
virtual ssize_t	Read (void *buffer, size_t size)
	Read data from current position.
virtual ssize_t	ReadAt (off_t position, void *buffer, size_t size)=0
	Pure virtual to read data from a certain position.
status_t	ReadAtExactly (off_t position, void *buffer, size_t size, size_t *_bytesRead=NULL)
	Reads an exact amount of data from the object at the specified position into a buffer.
virtual off_t	Seek (off_t position, uint32 seekMode)=0
	Pure virtual to move the cursor to a certain position.
virtual status_t	SetSize (off_t size)
	Set the size of the object or data.
virtual ssize_t	Write (const void *buffer, size_t size)
	Write data to the current position.
virtual ssize_t	WriteAt (off_t position, const void *buffer, size_t size)=0
	Pure virtual to write data to a certain position.
status_t	WriteAtExactly (off_t position, const void *buffer, size_t size, size_t *_bytesWritten=NULL)
	Writes an exact amount of data from a buffer to the object at the specified position.
Public Member Functions inherited from BDataIO
	BDataIO ()
	This constructor does nothing.
virtual	~BDataIO ()
	This destructor does nothing.
virtual status_t	Flush ()
	Writes pending data to underlying storage.
virtual ssize_t	Read (void *buffer, size_t size)
	Reads data from the object into a buffer.
status_t	ReadExactly (void *buffer, size_t size, size_t *_bytesRead=NULL)
	Reads an exact amount of data from the object into a buffer.
virtual ssize_t	Write (const void *buffer, size_t size)
	Writes data from a buffer to the object.
status_t	WriteExactly (const void *buffer, size_t size, size_t *_bytesWritten=NULL)
	Writes an exact amount of data from a buffer to the object.

Detailed Description

A BPositionIO derived class that works on memory buffers.

This class is used if you require access that confirms to the BPositionIO interface on memory buffers that you created. If you would like to use that interface on new buffers, have a look at BMallocIO.

This class is particularly useful if you would like to use a class or method that are written to make use of the BPositionIO interface. It might also be used for 'secure' reading and writing from buffers, since this class automatically checks the bounds of anything you might want to do.

This class reimplements the Read(), Write(), ReadAt(), Writeat(), Seek() and Position() interface from BPositionIO.

Since

BeOS R3

Constructor & Destructor Documentation

BMemoryIO() [1/2]

BMemoryIO::BMemoryIO	(	void *	data,
		size_t	length
	)

Create a read/write object.

Parameters

data	A pointer to the buffer to adopt.
length	The size of the buffer.

See also

BMemoryIO(const void *buffer, size_t length) for a read-only implementation.

Since

BeOS R3

BMemoryIO() [2/2]

BMemoryIO::BMemoryIO	(	const void *	buffer,
		size_t	length
	)

Create a read-only object.

Parameters

buffer	A pointer to the const (read-only) buffer to adopt.
length	The size of the buffer.

See also

BMemoryIO(void *buffer, size_t length) for a read-write implementation.

Since

BeOS R3

~BMemoryIO()

BMemoryIO::~BMemoryIO ( )

virtual

The destructor does nothing.

Since

BeOS R3

Member Function Documentation

Position()

off_t BMemoryIO::Position ( ) const

virtual

Return the current position.

Returns

The current position as an off_t.

Since

BeOS R3

Implements BPositionIO.

ReadAt()

ssize_t BMemoryIO::ReadAt ( off_t  pos, void *  buffer, size_t  size  )

virtual

Read from a given position.

Parameters

[in]	pos	The offset where to start reading data.
[out]	buffer	The buffer to copy the read bytes into.
[in]	size	The size of the buffer.

Returns

The amount of read bytes or an error code.

Return values

B_BAD_VALUE

The position is less than zero or the buffer given on construction is invalid.

Since

BeOS R3

Implements BPositionIO.

Seek()

off_t BMemoryIO::Seek ( off_t  position, uint32  seek_mode  )

virtual

Move the cursor to a given position.

Parameters

position	The position to move the cursor to.
seek_mode	The mode determines where the cursor is placed. Possibilities include: SEEK_SET The cursor is set to position. SEEK_CUR The position is added to the current position of the cursor. SEEK_END The cursor is put at the end of the data, plus position added to it.

Returns

The new position.

Since

BeOS R3

Implements BPositionIO.

SetSize()

status_t BMemoryIO::SetSize ( off_t  size )

virtual

Resize the buffer.

This method does not actually resize the buffer. If the new size is greater than the size of the buffer, resizing will fail. It will only succeed if the new size is less than the size of the buffer. The buffer itself will not be resized though.

This method might be useful in some cases. If the buffer is larger than the data it holds, changing the size will enable you to use the Seek() method with the flag SEEK_END and not get an error if you read or write from that position, since you actually have a buffer at the end.

Return values

B_OK	The buffer is resized.
B_NOT_ALLOWED	The buffer is read-only.
B_ERROR	The size is larger than the size of the buffer.

Since

BeOS R3

Reimplemented from BPositionIO.

WriteAt()

ssize_t BMemoryIO::WriteAt ( off_t  pos, const void *  buffer, size_t  size  )

virtual

Write at a given position.

Parameters

pos	The offset to write to.
buffer	The buffer to copy the bytes from.
size	The number of bytes to write.

Returns

The amount of bytes written or an error code.

Return values

B_NOT_ALLOWED	The object is constructed as a read-only object.
B_BAD_VALUE	The position is less than zero or the buffer given on construction is invalid.

Since

BeOS R3

Implements BPositionIO.