source: box/trunk/lib/common/ZeroStream.cpp @ 3105

// --------------------------------------------------------------------------
//
// File
//              Name:    ZeroStream.cpp
//              Purpose: An IOStream which returns all zeroes up to a certain size
//              Created: 2007/04/28
//
// --------------------------------------------------------------------------

#include "Box.h"
#include "ZeroStream.h"
#include "CommonException.h"

#include <string.h>

#include "MemLeakFindOn.h"

// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::ZeroStream(IOStream::pos_type)
//              Purpose: Constructor
//              Created: 2007/04/28
//
// --------------------------------------------------------------------------
ZeroStream::ZeroStream(IOStream::pos_type size)
: mSize(size), mPosition(0)
{ }


// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::Read(void *, int)
//              Purpose: Reads bytes from the file
//              Created: 2007/01/16
//
// --------------------------------------------------------------------------
int ZeroStream::Read(void *pBuffer, int NBytes, int Timeout)
{
        ASSERT(NBytes > 0);

        int bytesToRead = NBytes;
        
        if (bytesToRead > mSize - mPosition)
        {
                bytesToRead = mSize - mPosition;
        }

        memset(pBuffer, 0, bytesToRead);
        mPosition += bytesToRead;

        return bytesToRead;
}


// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::BytesLeftToRead()
//              Purpose: Returns number of bytes to read (may not be most efficient function ever)
//              Created: 2007/01/16
//
// --------------------------------------------------------------------------
IOStream::pos_type ZeroStream::BytesLeftToRead()
{
        return mSize - mPosition;
}


// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::Write(void *, int)
//              Purpose: Writes bytes to the underlying stream (not supported)
//              Created: 2003/07/31
//
// --------------------------------------------------------------------------
void ZeroStream::Write(const void *pBuffer, int NBytes)
{
        THROW_EXCEPTION(CommonException, NotSupported);
}


// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::GetPosition()
//              Purpose: Get position in stream
//              Created: 2003/08/21
//
// --------------------------------------------------------------------------
IOStream::pos_type ZeroStream::GetPosition() const
{
        return mPosition;
}


// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::Seek(pos_type, int)
//              Purpose: Seeks within file, as lseek, invalidate buffer
//              Created: 2003/07/31
//
// --------------------------------------------------------------------------
void ZeroStream::Seek(IOStream::pos_type Offset, int SeekType)
{
        switch (SeekType)
        {
                case SeekType_Absolute:
                {
                        mPosition = Offset;
                }
                break;

                case SeekType_Relative:
                {
                        mPosition += Offset;
                }
                break;

                case SeekType_End:
                {
                        mPosition = mSize - Offset;
                }
        }
}


// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::Close()
//              Purpose: Closes the underlying stream (not needed)
//              Created: 2003/07/31
//
// --------------------------------------------------------------------------
void ZeroStream::Close()
{
        THROW_EXCEPTION(CommonException, NotSupported);
}


// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::StreamDataLeft()
//              Purpose: Any data left to write?
//              Created: 2003/08/02
//
// --------------------------------------------------------------------------
bool ZeroStream::StreamDataLeft()
{
        return (BytesLeftToRead() > 0);
}

// --------------------------------------------------------------------------
//
// Function
//              Name:    ZeroStream::StreamClosed()
//              Purpose: Is the stream closed?
//              Created: 2003/08/02
//
// --------------------------------------------------------------------------
bool ZeroStream::StreamClosed()
{
        return false;
}