Basic buffer with read/write cursors. More...

#include <ReadWriteBuffer.h>

Public Member Functions
	ReadWriteBuffer ()
	constructor
	ReadWriteBuffer (const ReadWriteBuffer &)
	Create an internal buffer copy of the supplied buffer.
ReadWriteBuffer &	operator= (const ReadWriteBuffer &)
	Copy the supplied buffer to an internal buffer.
	~ReadWriteBuffer ()
	destructor
void	Deallocate ()
	Deallocate and clear out any existing buffer.
void	SetEmpty ()
	Clear the existing buffer to zero lengths for read and write buffers.
void	SetExternalBuffer (void *a_pBuf, size_t a_nBufSiz, size_t a_nBufLen=0, size_t a_nGrowBy=0)
	Set the buffer as an alias to an external buffer.
void	SetInternalBuffer (size_t a_nInitialSize, size_t a_nGrowBy=1024)
	Replace the current buffer with an internal growable buffer.
char *	GetWriteBuffer (size_t a_nMinBytes=0)
	Get a write pointer into the buffer guaranteeing that the specified number of bytes are available.
void	CommitWriteBytes (size_t a_nBytes)
	Commit the specified number of bytes to the buffer.
size_t	GetWriteSize () const
	Get the available buffer size for writing.
void	WriteBytes (const void *a_pBuf, size_t a_nBufLen)
	Write the supplied data to the write buffer.
const char *	GetReadBuffer () const
	Get the read buffer.
void	CommitReadBytes (size_t a_nBytes)
	Update the read bytes available.
size_t	GetReadSize () const
	Get the available buffer size for reading.
void	ReadBytes (void *a_pBuf, size_t a_nBufLen)
	Read the data from the buffer.
void	Compact ()
	Compact the buffer.
bool	operator== (const ReadWriteBuffer &) const
	Do a memcmp on the read buffers.
Private Attributes
size_t	mBufSiz
	max buf size
size_t	mBufLen
	committed writes
size_t	mBufIdx
	committed reads
size_t	mGrowBy
	growby rate
bool	mIsExt
	is this an external buffer?
char *	mBuf
	buffer

Detailed Description

Basic buffer with read/write cursors.

The buffer may be backed by either an internally allocated and managed growable buffer, or a statically sized external buffer may be used.

Example:

        ReadWriteBuffer buf;

        char * p = buf.GetWriteBuffer(sizeof(data1));
        memcpy(p, data1, sizeof(data1));
        buf.CommitWriteBytes(sizeof(data1));

        p = buf.GetWriteBuffer(sizeof(data2));
        memcpy(p, data2, sizeof(data2));
        buf.CommitWriteBytes(sizeof(data2));

        while (buf.GetReadSize() > 0) {
            fputc(*buf.GetReadBuffer(), fp);
            buf.CommitReadBytes(1);
        }

Definition at line 42 of file ReadWriteBuffer.h.

Constructor & Destructor Documentation

ReadWriteBuffer::ReadWriteBuffer ( const ReadWriteBuffer & rhs )

Create an internal buffer copy of the supplied buffer.

Only the committed data will be copied. The available bytes may be different to the source buffer.

Definition at line 25 of file ReadWriteBuffer.cpp.

References operator=().

Member Function Documentation

void ReadWriteBuffer::CommitReadBytes ( size_t a_nBytes )

Update the read bytes available.

Indicate that the specified number of bytes have been read and are not necessary anymore. These bytes are now available for reclaiming by Compact().

Parameters:

a_nBytes Number of bytes read

Exceptions:

std::invalid_argument if more bytes were committed then is available

Definition at line 195 of file ReadWriteBuffer.cpp.

References mBufIdx, and mBufLen.

Referenced by ReadBytes(), and MemCacheClient::Store().

void ReadWriteBuffer::CommitWriteBytes ( size_t a_nBytes )

Commit the specified number of bytes to the buffer.

This function should be called after the buffer returned by GetWriteBuffer() is written to. After calling this function, the specified bytes will then be available for reading from the GetReadBuffer() and GetReadSize() functions.

Parameters:

a_nBytes Number of bytes written

Exceptions:

std::invalid_argument if more bytes were committed then is available

Definition at line 163 of file ReadWriteBuffer.cpp.

References mBufLen, and mBufSiz.

Referenced by MemCacheClient::HandleGetResponse(), and WriteBytes().

void ReadWriteBuffer::Compact ( )

Compact the buffer.

All remaining unread bytes are moved to the beginning of the buffer leaving the largest size available for writing.

Definition at line 225 of file ReadWriteBuffer.cpp.

References GetReadBuffer(), GetReadSize(), mBuf, mBufIdx, and mBufLen.

const char * ReadWriteBuffer::GetReadBuffer ( ) const

Get the read buffer.

See GetReadSize() for the number of bytes available to be read from this pointer.

Returns:: Pointer to the data to be read.

Definition at line 189 of file ReadWriteBuffer.cpp.

References mBuf, and mBufIdx.

Referenced by Compact(), operator==(), and ReadBytes().

size_t ReadWriteBuffer::GetReadSize ( ) const

Get the available buffer size for reading.

Returns:: number of bytes available for reading

Definition at line 204 of file ReadWriteBuffer.cpp.

References mBufIdx, and mBufLen.

Referenced by Compact(), operator==(), ReadBytes(), and MemCacheClient::Store().

char * ReadWriteBuffer::GetWriteBuffer ( size_t a_nMinBytes = 0 )

Get a write pointer into the buffer guaranteeing that the specified number of bytes are available.

Call CommitWriteBytes() after accessing the buffer to specify the number of bytes actually written.

Parameters:

a_nMinBytes Minimum writable size required for the returned pointer. If 0 then the currently available buffer will be returned without resizing it. The available bytes for writing can be determined via GetWriteSize().

Exceptions:

std::overflow_error	when an external buffer is used, conversion to an internal buffer on overflow is disabled, and a_nMinBytes is not available in the buffer.
std::bad_alloc	when using an internal buffer and there was an out of memory error on resizing.

Returns:: Writable pointer to a buffer with at least the requested number of bytes available for writing. See the function GetWriteSize() to find the actual number of bytes available.

Definition at line 134 of file ReadWriteBuffer.cpp.

References mBuf, mBufLen, mBufSiz, mGrowBy, mIsExt, and roundup().

Referenced by MemCacheClient::HandleGetResponse(), operator=(), and WriteBytes().

size_t ReadWriteBuffer::GetWriteSize ( ) const

Get the available buffer size for writing.

Returns:: number of bytes available in the write buffer returned from GetWriteBuffer()

Definition at line 172 of file ReadWriteBuffer.cpp.

References mBufLen, and mBufSiz.

ReadWriteBuffer & ReadWriteBuffer::operator= ( const ReadWriteBuffer & rhs )

Copy the supplied buffer to an internal buffer.

Only the committed data will be copied. The available bytes may be different to the source buffer.

Definition at line 39 of file ReadWriteBuffer.cpp.

References Deallocate(), GetWriteBuffer(), mBuf, mBufIdx, mBufLen, mBufSiz, mGrowBy, and SetInternalBuffer().

Referenced by ReadWriteBuffer().

void ReadWriteBuffer::ReadBytes	(	void *	a_pBuf,
		size_t	a_nBufLen
	)

Read the data from the buffer.

This function is a simple wrapper around calls to GetReadSize, GetReadBuffer, memcpy, CommitReadBytes.

Parameters:

a_pBuf	Location for the buffer data to be copied to
a_nBufLen	Length of the data in bytes to copy

Exceptions:

std::invalid_argument not enough bytes in the buffer

Definition at line 210 of file ReadWriteBuffer.cpp.

References CommitReadBytes(), GetReadBuffer(), and GetReadSize().

void ReadWriteBuffer::SetExternalBuffer	(	void *	a_pBuf,
		size_t	a_nBufSiz,
		size_t	a_nBufLen = `0`,
		size_t	a_nGrowBy = `0`
	)

Set the buffer as an alias to an external buffer.

Parameters:

a_pBuf	Buffer to use as external store.
a_nBufSiz	Maximum size of the buffer for writing.
a_nBufLen	Current length of readable data in buffer.
a_nGrowBy	When 0, running out of space in the buffer throws an exception. When > 0, the buffer is automatically converted to an internal buffer with this growby value.

Exceptions:

std::invalid_argument

Definition at line 82 of file ReadWriteBuffer.cpp.

References Deallocate(), mBuf, mBufIdx, mBufLen, mBufSiz, mGrowBy, and mIsExt.

void ReadWriteBuffer::SetInternalBuffer	(	size_t	a_nInitialSize,
		size_t	a_nGrowBy = `1024`
	)

Replace the current buffer with an internal growable buffer.

Internal buffers will be grown by adding a_nMinBytes rounded up to an even multiples of a_nGrowBy.

Parameters:

a_nInitialSize	Initial size to create the internal buffer at
a_nGrowBy	Number of bytes to grow the buffer by whenever it runs out of space.

Definition at line 115 of file ReadWriteBuffer.cpp.

References Deallocate(), mBuf, mBufSiz, mGrowBy, and roundup().

Referenced by operator=().

void ReadWriteBuffer::WriteBytes	(	const void *	a_pBuf,
		size_t	a_nBufLen
	)

Write the supplied data to the write buffer.

This function is a simple wrapper around calls to GetWriteBuffer, memcpy, CommitWriteBytes.

Parameters:

a_pBuf	Data to copy to the buffer
a_nBufLen	Length of the data in bytes to copy

Exceptions:

std::overflow_error	when an external buffer is used and a_nBufLen is not available.
std::bad_alloc	when using an internal buffer and there was an out of memory error on resizing.

Definition at line 178 of file ReadWriteBuffer.cpp.

References CommitWriteBytes(), and GetWriteBuffer().

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

ReadWriteBuffer Class Reference

Public Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation