source: box/trunk/lib/common/PartialReadStream.cpp @ 2127

// --------------------------------------------------------------------------
//
// File
//              Name:    PartialReadStream.h
//              Purpose: Read part of another stream
//              Created: 2003/08/26
//
// --------------------------------------------------------------------------

#include "Box.h"
#include "PartialReadStream.h"
#include "CommonException.h"

#include "MemLeakFindOn.h"

// --------------------------------------------------------------------------
//
// Function
//              Name:    PartialReadStream::PartialReadStream(IOStream &,
//                       pos_type)
//              Purpose: Constructor, taking another stream and the number of
//                       bytes to be read from it.
//              Created: 2003/08/26
//
// --------------------------------------------------------------------------
PartialReadStream::PartialReadStream(IOStream &rSource,
        pos_type BytesToRead)
        : mrSource(rSource),
          mBytesLeft(BytesToRead)
{
        ASSERT(BytesToRead > 0);
}

// --------------------------------------------------------------------------
//
// Function
//              Name:    PartialReadStream::~PartialReadStream()
//              Purpose: Destructor. Won't absorb any unread bytes.
//              Created: 2003/08/26
//
// --------------------------------------------------------------------------
PartialReadStream::~PartialReadStream()
{
        // Warn in debug mode
        if(mBytesLeft != 0)
        {
                BOX_TRACE("PartialReadStream destroyed with " << mBytesLeft <<
                        " bytes remaining");
        }
}

// --------------------------------------------------------------------------
//
// Function
//              Name:    PartialReadStream::Read(void *, int, int)
//              Purpose: As interface.
//              Created: 2003/08/26
//
// --------------------------------------------------------------------------
int PartialReadStream::Read(void *pBuffer, int NBytes, int Timeout)
{
        // Finished?
        if(mBytesLeft <= 0)
        {
                return 0;
        }

        // Asking for more than is allowed?
        if(NBytes > mBytesLeft)
        {
                // Adjust downwards
                NBytes = mBytesLeft;
        }
        
        // Route the request to the source
        int read = mrSource.Read(pBuffer, NBytes, Timeout);
        ASSERT(read <= mBytesLeft);
        
        // Adjust the count
        mBytesLeft -= read;
        
        // Return the number read
        return read;
}

// --------------------------------------------------------------------------
//
// Function
//              Name:    PartialReadStream::BytesLeftToRead()
//              Purpose: As interface.
//              Created: 2003/08/26
//
// --------------------------------------------------------------------------
IOStream::pos_type PartialReadStream::BytesLeftToRead()
{
        return mBytesLeft;
}

// --------------------------------------------------------------------------
//
// Function
//              Name:    PartialReadStream::Write(const void *, int)
//              Purpose: As interface. But will exception.
//              Created: 2003/08/26
//
// --------------------------------------------------------------------------
void PartialReadStream::Write(const void *pBuffer, int NBytes)
{
        THROW_EXCEPTION(CommonException, CantWriteToPartialReadStream)
}

// --------------------------------------------------------------------------
//
// Function
//              Name:    PartialReadStream::StreamDataLeft()
//              Purpose: As interface.
//              Created: 2003/08/26
//
// --------------------------------------------------------------------------
bool PartialReadStream::StreamDataLeft()
{
        return mBytesLeft != 0;
}

// --------------------------------------------------------------------------
//
// Function
//              Name:    PartialReadStream::StreamClosed()
//              Purpose: As interface.
//              Created: 2003/08/26
//
// --------------------------------------------------------------------------
bool PartialReadStream::StreamClosed()
{
        // always closed
        return true;
}