/*++

Copyright (c) 1992  Microsoft Corporation

Module Name:

    slipread.c

Abstract:


Author:

    Thomas J. Dimitri  (TommyD) 08-May-1992

Environment:

    Kernel Mode - Or whatever is the equivalent on OS/2 and DOS.

Revision History:


--*/

#include "asyncall.h"

NTSTATUS
AsyncWaitMaskCompletionRoutine(
    IN PDEVICE_OBJECT DeviceObject,
    IN PIRP Irp,
    IN PVOID Context);


NTSTATUS
AsyncPPPWaitMask(
    IN PASYNC_INFO Info);


NTSTATUS
AsyncSLIPCompletionRoutine(
    IN PDEVICE_OBJECT DeviceObject,
    IN PIRP Irp,
    IN PVOID Context)

/*++

    This is the IO Completion routine for ReadFrame.

--*/
{
    NTSTATUS        status;
    PASYNC_INFO     pInfo;
    ULONG           bytesReceived;

    PASYNC_FRAME    pFrame;
    PUCHAR          frameStart, frameEnd;
    PUCHAR          frameEnd2,frameStart2;
    ULONG           bitMask;
    LONG            bytesWanted;        // keep this a long ( < 0 is used)


    DeviceObject;       // prevent compiler warnings

    status = Irp->IoStatus.Status;
    bytesReceived=(ULONG)Irp->IoStatus.Information;

    IoFreeIrp(Irp);

    pInfo=Context;

    pFrame=pInfo->AsyncFrame;

    switch (status) {

    case STATUS_SUCCESS:


        //
        // Any bytes to process?  This can happen if
        // the WaitMask completes late and by the time
        // we process the read, another event character has come
        // in.
        //
        if (bytesReceived==0) {
            break;
        }

        //
        // Update num of bytes read total for this frame
        //
        pInfo->BytesRead = bytesReceived = pInfo->BytesRead + bytesReceived;

        //
        // Set frameEnd to last byte processed.  Initially,
        // we have processed nothing (i.e. processed up to
        // the start of the first byte).
        //
        frameStart=pFrame->Frame + PPP_PADDING;

PROCESS_FRAME:
        //
        // Now we have actuallyRead bytes unused
        // Also, we may have a complete frame.
        //
        while (*frameStart == SLIP_END_BYTE && --bytesReceived) {
            frameStart++;
        }

        //
        // If we reach here, there is no end FLAG
        //
        if (bytesReceived == 0) {
            break;
        }

        //
        // frameEnd is set to the first byte not yet processed.
        // If we are starting out, that is the first byte!
        //
        frameEnd=frameStart;

        //
        // Assume the start of the frame has the SLIP_END_BYTE
        // Look for the second SLIP_END_BYTE (end of frame)
        //
        while (*frameEnd != SLIP_END_BYTE && --bytesReceived) {
            frameEnd++;
        }

        //
        // if bytesReceived is 0, we got nothing
        //
        // NOTE: if BytesRead gets too high we trash the frame
        // because we could not find the FLAG_BYTE
        //
        if (bytesReceived==0) {
            break;
        }
        
        if (*(pFrame->Frame+PPP_PADDING) != SLIP_END_BYTE) {
            //
            // We had garbage at the start.  Remove the garbage.
            //

            pInfo->SerialStats.AlignmentErrors++;

            //
            //  Tell the transport above us that we dropped a packet
            //  Hopefully, it will quickly resync.
            //
            AsyncIndicateFragment(
                pInfo,
                WAN_ERROR_ALIGNMENT);

            goto NEXT_SLIP_FRAME;
        }

        //
        // Length of frame is frameEnd - frameStart
        //
        bytesWanted = (LONG)(frameEnd - frameStart);

        bitMask = pInfo->Adapter->WanInfo.DesiredACCM;

        frameEnd2 = frameStart2 = frameStart;

        //
        // Replace back all control chars, ESC, and FLAG chars
        //
        while (bytesWanted-- > 0) {
            if ((*frameEnd2=*frameStart2++) == SLIP_ESC_BYTE) {

                //
                // We have not run the CRC check yet!!
                // We have be careful about sending bytesWanted
                // back to -1 on corrupted data
                //

                bytesWanted--;

                *frameEnd2 = SLIP_END_BYTE;

                if (*frameStart2++ == SLIP_ESC_ESC_BYTE) {
                    *frameEnd2 = SLIP_ESC_BYTE;
                }
            }

            frameEnd2++;
        }

        //
        // Change the bytesWanted field to what it normally is,
        // the length of the frame.
        //
        bytesWanted = (LONG)(frameEnd2 - frameStart);

        // Keep those stats up to date
        {
            KIRQL       irql;
            NTSTATUS    Status;
            PASYNC_ADAPTER  Adapter = pInfo->Adapter;

            KeRaiseIrql( (KIRQL)DISPATCH_LEVEL, &irql );

            //
            // Compressed TCP/IP packets must at least 3 bytes long
            //
            if (bytesWanted >= 3) {
        
                NdisMWanIndicateReceive(
                    &Status,
                    Adapter->MiniportHandle,
                    pInfo->NdisLinkContext,
                    frameStart,
                    bytesWanted);
    
                NdisMWanIndicateReceiveComplete(
                    Adapter->MiniportHandle,
                    pInfo->NdisLinkContext);

            } else {

                pInfo->SerialStats.AlignmentErrors++;

                //
                //  Tell the transport above us that we dropped a packet
                //  Hopefully, it will quickly resync.
                //
                AsyncIndicateFragment(
                    pInfo,
                    WAN_ERROR_ALIGNMENT);

                DbgTracef(-2,("SLIP: Frame too small %u\n", bytesWanted));
            }


            KeLowerIrql( irql );
        }

    NEXT_SLIP_FRAME:

        //
        // if bytesReceived == 0 no frame was found
        // thus we must keep the current frame and continue
        // processing
        //
        if (bytesReceived) {

            //
            // Calculate how much of what we received
            // just got passed up as a frame and move the
            // rest to the beginning.
            //
            frameStart=pFrame->Frame + PPP_PADDING;
            frameEnd2=frameStart + pInfo->BytesRead;
            pInfo->BytesRead =
                            bytesReceived = (LONG)(frameEnd2-frameEnd);

            ASYNC_MOVE_MEMORY(
                frameStart,         // dest
                frameEnd,           // src
                bytesReceived);     // length

            //
            // Need at least four bytes for a frame to exist
            //
            if (bytesReceived > 3) {
                goto PROCESS_FRAME;
            }
        }

        break;

    case STATUS_CANCELLED:
        // else this is an anomally!
        DbgTracef(-2,("---ASYNC: Status cancelled on read for unknown reason!!\n"));
        break;

    case STATUS_PENDING:
        DbgTracef(0,("---ASYNC: Status PENDING on read\n"));
        break;

    default:
        DbgTracef(-2,("---ASYNC: Unknown status 0x%.8x on read",status));
        break;

    }

    //
    // Here we are at the end of processing this IRP so we go
    // ahead and post another read from the serial port.
    //
    AsyncPPPWaitMask(pInfo);

    // We return STATUS_MORE_PROCESSING_REQUIRED so that the
    // IoCompletionRoutine will stop working on the IRP.
    return(STATUS_MORE_PROCESSING_REQUIRED);
}