NT4/private/ntos/mailslot/writesup.c

/*++

Copyright (c) 1989  Microsoft Corporation

Module Name:

    writesup.c

Abstract:

    This module implements the write support routine.  This is a common
    write function that is called by write and mailslot write.

Author:

    Manny Weiser (mannyw)   16-Jan-1991

Revision History:

--*/

#include "mailslot.h"

//
//  The debug trace level
//

#define Dbg                              (DEBUG_TRACE_WRITESUP)

#ifdef ALLOC_PRAGMA
#pragma alloc_text( PAGE, MsWriteDataQueue )
#endif

BOOLEAN
MsWriteDataQueue (
    IN PDATA_QUEUE WriteQueue,
    IN PUCHAR WriteBuffer,
    IN ULONG WriteLength
    )

/*++

Routine Description:

    This function writes data from the write buffer into read entries in
    the write queue.  It will also dequeue entries in the queue as necessary.

    *** This function must be called from within a try statement.

Arguments:

    WriteQueue - Provides the write queue to process.

    WriteBuffer - Provides the buffer from which to read the data.

    WriteLength  - Provides the length, in bytes, of WriteBuffer.

Return Value:

    BOOLEAN - TRUE if the operation wrote everything and FALSE otherwise.

--*/

{
    BOOLEAN result;

    PDATA_ENTRY dataEntry;
    PLIST_ENTRY listEntry;
    PFCB fcb;

    PUCHAR readBuffer;
    ULONG readLength;
    PIRP readIrp;
    NTSTATUS readStatus = STATUS_UNSUCCESSFUL;

    PWORK_CONTEXT workContext;
    PKTIMER timer;

    PAGED_CODE();
    DebugTrace(+1, Dbg, "MsWriteDataQueue\n", 0);
    DebugTrace( 0, Dbg, "WriteQueue  = %08lx\n", (ULONG)WriteQueue);
    DebugTrace( 0, Dbg, "WriteBuffer = %08lx\n", (ULONG)WriteBuffer);
    DebugTrace( 0, Dbg, "WriteLength = %08lx\n", WriteLength);

    //
    // Now while the write queue has some read entries in it and
    // we have not successfully completed a read then we'll do the
    // following main loop.
    //

    for (listEntry = MsGetNextDataQueueEntry( WriteQueue );

         MsIsDataQueueReaders(WriteQueue) && !NT_SUCCESS(readStatus);

         listEntry = MsGetNextDataQueueEntry( WriteQueue )) {

        dataEntry = CONTAINING_RECORD( listEntry, DATA_ENTRY, ListEntry );
        readBuffer = dataEntry->DataPointer;
        readLength = dataEntry->DataSize;

        DebugTrace(0, Dbg, "Top of write loop...\n", 0);
        DebugTrace(0, Dbg, "ReadBuffer      = %08lx\n", (ULONG)readBuffer);
        DebugTrace(0, Dbg, "ReadLength      = %08lx\n", readLength);

        //
        // We are about to complete a read IRP, so dequeue it.
        //

        readIrp = MsRemoveDataQueueEntry( WriteQueue, dataEntry );
        ASSERT( readIrp != NULL );

        //
        // If the buffer for this read operation is large enough
        // copy the data.
        //

        if ( readLength >= WriteLength ) {

            //
            // Copy the data from the write buffer to the read buffer.
            //

            RtlMoveMemory( readBuffer,
                           WriteBuffer,
                           WriteLength);

            readIrp->IoStatus.Information = WriteLength;
            readStatus = STATUS_SUCCESS;

        } else {

            //
            // This read buffer was overflowed.
            //

            readIrp->IoStatus.Information = 0;
            readStatus = STATUS_BUFFER_TOO_SMALL;

        }

        //
        // Complete the read IRP.
        //

        workContext = dataEntry->TimeoutWorkContext;
        if (workContext != NULL) {

            DebugTrace( 0, Dbg, "Cancelling a timer\n", 0);

            //
            // There was a timer on this read operation.  Attempt
            // to cancel the operation.  If the cancel operation
            // is successful, then we must cleanup after the operation.
            // If it was unsuccessful the timer DPC will run, and
            // will eventually cleanup.
            //

            timer = &workContext->Timer;

            if (KeCancelTimer( timer ) ) {

                //
                // Release the reference to the FCB.
                //

                MsDereferenceFcb( workContext->Fcb );

                //
                // Free the memory from the work context, the timer,
                // and the DPC.
                //

                ExFreePool( workContext );

            }

        }

        //
        // Update the FCB last access time and complete the read request.
        //

        fcb = CONTAINING_RECORD( WriteQueue, FCB, DataQueue );
        if ( NT_SUCCESS( readStatus ) ) {
            KeQuerySystemTime( &fcb->Specific.Fcb.LastAccessTime );
        }

        MsCompleteRequest( readIrp, readStatus );

    }

    DebugTrace(0, Dbg, "Finished loop...\n", 0);

    //
    // At this point we've finished off all of the read entries in the
    // queue and we might not have written the write data.  If that
    // is the case then we'll set our result to FALSE otherwise we're
    // done so we'll return TRUE.
    //

    if ( !NT_SUCCESS( readStatus ) ) {

        ASSERT( !MsIsDataQueueReaders( WriteQueue ));
        result = FALSE;

    } else {

        result = TRUE;
    }

    DebugTrace(-1, Dbg, "MsWriteDataQueue -> %08lx\n", result);
    return result;

}