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// --------------------------------------------------------------------------
//
// File
// Name: BufferedStream.cpp
// Purpose: Buffering read-only wrapper around IOStreams
// Created: 2007/01/16
//
// --------------------------------------------------------------------------
#include "Box.h"
#include "BufferedStream.h"
#include "CommonException.h"
#include <string.h>
#include "MemLeakFindOn.h"
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::BufferedStream(const char *, int, int)
// Purpose: Constructor, set up buffer
// Created: 2007/01/16
//
// --------------------------------------------------------------------------
BufferedStream::BufferedStream(IOStream& rSource)
: mrSource(rSource), mBufferSize(0), mBufferPosition(0)
{ }
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::Read(void *, int)
// Purpose: Reads bytes from the file
// Created: 2007/01/16
//
// --------------------------------------------------------------------------
int BufferedStream::Read(void *pBuffer, int NBytes, int Timeout)
{
if (mBufferSize == mBufferPosition)
{
// buffer is empty, fill it.
int numBytesRead = mrSource.Read(mBuffer, sizeof(mBuffer),
Timeout);
if (numBytesRead < 0)
{
return numBytesRead;
}
mBufferSize = numBytesRead;
}
int sizeToReturn = mBufferSize - mBufferPosition;
if (sizeToReturn > NBytes)
{
sizeToReturn = NBytes;
}
memcpy(pBuffer, mBuffer + mBufferPosition, sizeToReturn);
mBufferPosition += sizeToReturn;
if (mBufferPosition == mBufferSize)
{
// clear out the buffer
mBufferSize = 0;
mBufferPosition = 0;
}
return sizeToReturn;
}
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::BytesLeftToRead()
// Purpose: Returns number of bytes to read (may not be most efficient function ever)
// Created: 2007/01/16
//
// --------------------------------------------------------------------------
IOStream::pos_type BufferedStream::BytesLeftToRead()
{
return mrSource.BytesLeftToRead() + mBufferSize - mBufferPosition;
}
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::Write(void *, int)
// Purpose: Writes bytes to the underlying stream (not supported)
// Created: 2003/07/31
//
// --------------------------------------------------------------------------
void BufferedStream::Write(const void *pBuffer, int NBytes, int Timeout)
{
THROW_EXCEPTION(CommonException, NotSupported);
}
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::GetPosition()
// Purpose: Get position in stream
// Created: 2003/08/21
//
// --------------------------------------------------------------------------
IOStream::pos_type BufferedStream::GetPosition() const
{
return mrSource.GetPosition() - mBufferSize + mBufferPosition;
}
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::Seek(pos_type, int)
// Purpose: Seeks within file, as lseek, invalidate buffer
// Created: 2003/07/31
//
// --------------------------------------------------------------------------
void BufferedStream::Seek(IOStream::pos_type Offset, int SeekType)
{
switch (SeekType)
{
case SeekType_Absolute:
{
// just go there
mrSource.Seek(Offset, SeekType);
}
break;
case SeekType_Relative:
{
// Actual underlying file position is
// (mBufferSize - mBufferPosition) ahead of us.
// Need to subtract that amount from the seek
// to seek forward that much less, putting the
// real pointer in the right place.
mrSource.Seek(Offset - mBufferSize + mBufferPosition,
SeekType);
}
break;
case SeekType_End:
{
// Actual underlying file position is
// (mBufferSize - mBufferPosition) ahead of us.
// Need to add that amount to the seek
// to seek backwards that much more, putting the
// real pointer in the right place.
mrSource.Seek(Offset + mBufferSize - mBufferPosition,
SeekType);
}
}
// always clear the buffer for now (may be slightly wasteful)
mBufferSize = 0;
mBufferPosition = 0;
}
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::Close()
// Purpose: Closes the underlying stream (not needed)
// Created: 2003/07/31
//
// --------------------------------------------------------------------------
void BufferedStream::Close()
{
THROW_EXCEPTION(CommonException, NotSupported);
}
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::StreamDataLeft()
// Purpose: Any data left to write?
// Created: 2003/08/02
//
// --------------------------------------------------------------------------
bool BufferedStream::StreamDataLeft()
{
// Return true if either the source has data left to read, or we have
// buffered data still to be read.
return mrSource.StreamDataLeft() || (mBufferPosition < mBufferSize);
}
// --------------------------------------------------------------------------
//
// Function
// Name: BufferedStream::StreamClosed()
// Purpose: Is the stream closed?
// Created: 2003/08/02
//
// --------------------------------------------------------------------------
bool BufferedStream::StreamClosed()
{
return mrSource.StreamClosed();
}
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