void DZeroCopyLoopbackDevice::ReceiveDataCallback()
{
// Copy buffer from send queue (it's like our receive hardware) to receive queue
DCommsBuf* srcBuf = iSendQueue.HeadBuffer();
if(!iReceiveQueue.IsFull() && !iSendQueue.IsEmpty())
{
// Alloc a new buffer in to which we will copy the received (sent) buffer (mimicking DMA in the non zerocopy case)
DCommsBuf newBuf;
TInt result = iLdd->Pond().Alloc(newBuf);
if(result == KErrNone)
{
// Copy our buffer and set the new buffer's properties
TInt srcPayloadLength = srcBuf->Length();
newBuf.SetOffset(0);
newBuf.SetLength(srcPayloadLength);
// Do the copy
TUint8* srcPayloadPtr = srcBuf->Ptr();
TUint8* destPayloadPtr = newBuf.Ptr();
memcpy(destPayloadPtr, srcPayloadPtr, srcPayloadLength);
// Put the new buffer in the receive queue
DCommsBuf* destBuf = iReceiveQueue.TailBuffer();
*destBuf = newBuf;
iReceiveQueue.Push();
// Drop the incoming buffer
srcBuf->Free();
// Step the queue
iSendQueue.Pop();
}
// We can now complete any outstanding request for received data - if indeed we managed to alloc a receive buffer
if(iPendingRead && !iReceiveQueue.IsEmpty())
{
iPendingRead = FALSE;
// Tell LDD we're done
iLdd->ReceiveDataComplete(KErrNone);
}
}
}
DCommsBuf* DZeroCopyLoopbackDevice::ReceiveBuffer()
{
return iReceiveQueue.HeadBuffer();
}