indri::file::SequentialWriteBuffer Class Reference

#include <SequentialWriteBuffer.hpp>

List of all members.

Public Member Functions
	SequentialWriteBuffer (File &file, size_t length)
void	seek (UINT64 position)
char *	write (size_t length)
void	write (const void *buffer, size_t length)
void	unwrite (size_t length)
UINT64	tell () const
void	flush ()
void	flushRegion (UINT64 start, UINT64 length)
Private Attributes
File &	_file
InternalFileBuffer	_current
UINT64	_position
UINT64	_eof

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Detailed Description

Wraps an instance of indri::file::File, and provides buffering support. This class works much like the BufferedWriter class in Java; every write is stored in a memory buffer until that buffer fills, then the data is transferred to disk en masse.

There are at least two good reasons to buffer data before writing. The first is to avoid system call overhead for little tiny writes. If this is all you care about, you can keep this write buffer fairly small; perhaps a few kilobytes.

However, a write buffer can also keep the disk from seeking unnecessarily if you're writing to a few files simultaenously. For this kind of application, consider using a megabyte or so. This also helps keep file fragmentation down.

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Constructor & Destructor Documentation

indri::file::SequentialWriteBuffer::SequentialWriteBuffer (  File &  file, size_t  length )  [inline]

Constructs a new instance of the SequentialWriteBuffer class. The file pointer is set to the end of the file. Parameters: file  The File object to wrap. length  Number of bytes to buffer.

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Member Function Documentation

void indri::file::SequentialWriteBuffer::flush (   )  [inline]

Flushes data in the buffer out to the file.

void indri::file::SequentialWriteBuffer::flushRegion (  UINT64  start, UINT64  length )  [inline]

void indri::file::SequentialWriteBuffer::seek (  UINT64  position  )  [inline]

Seek to position bytes into the file.

UINT64 indri::file::SequentialWriteBuffer::tell (   )  const [inline]

Returns: Current file position.

void indri::file::SequentialWriteBuffer::unwrite (  size_t  length  )  [inline]

Move the file pointer back by length bytes, and remove all of those bytes from the buffer. It's as if you didn't write those length bytes at all. Parameters: length  Number of bytes to unwrite.

void indri::file::SequentialWriteBuffer::write (  const void *  buffer, size_t  length )  [inline]

Writes length bytes of data from buffer into the file. Parameters: buffer  Buffer containing data to be written to the file. length  Bytes to copy from the buffer into the file.

char* indri::file::SequentialWriteBuffer::write (  size_t  length  )  [inline]

Allocate space in the buffer for some new data. This is roughly equivalent to memory-mapping the next length bytes of the file. This buffer space is valid until your next call to a SequentialWriteBuffer method. Parameters: length  Number of bytes to write. Returns: Returns a pointer to memory where you can write your data.

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Member Data Documentation

InternalFileBuffer indri::file::SequentialWriteBuffer::_current [private]

UINT64 indri::file::SequentialWriteBuffer::_eof [private]

File& indri::file::SequentialWriteBuffer::_file [private]

UINT64 indri::file::SequentialWriteBuffer::_position [private]

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

• SequentialWriteBuffer.hpp

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