263 lines
4.8 KiB
C++
263 lines
4.8 KiB
C++
/*++
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Copyright (c) 1998, Microsoft Corporation
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Module Name:
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buffer.c
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Abstract:
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This module contains code for buffer-management.
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Author:
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Abolade Gbadegesin (aboladeg) 2-Mar-1998
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Revision History:
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--*/
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#include "stdafx.h"
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#include "nathlpp.h"
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#include "list.h"
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//#include "socket.h"
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LIST_ENTRY NhpBufferQueue;
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LONG NhpBufferQueueLength;
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CRITICAL_SECTION NhpBufferQueueLock;
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PNH_BUFFER
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NhAcquireFixedLengthBuffer(
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VOID
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)
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/*++
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Routine Description:
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This routine is invoked to acquire an I/O buffer.
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If no buffer is available on the buffer queue, a new one is obtained.
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Arguments:
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none.
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Return Value:
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PNH_BUFFER - the buffer allocated
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--*/
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{
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PNH_BUFFER Buffer;
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PLIST_ENTRY Link;
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EnterCriticalSection(&NhpBufferQueueLock);
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if (!IsListEmpty(&NhpBufferQueue)) {
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Link = RemoveHeadList(&NhpBufferQueue);
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LeaveCriticalSection(&NhpBufferQueueLock);
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InterlockedDecrement(&NhpBufferQueueLength);
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Buffer = CONTAINING_RECORD(Link, NH_BUFFER, Link);
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Buffer->Type = NhFixedLengthBufferType;
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return Buffer;
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}
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LeaveCriticalSection(&NhpBufferQueueLock);
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Buffer = NH_ALLOCATE_BUFFER();
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if (Buffer) {
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Buffer->Type = NhFixedLengthBufferType;
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}
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return Buffer;
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} // NhAcquireFixedLengthBuffer
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PNH_BUFFER
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NhAcquireVariableLengthBuffer(
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ULONG Length
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)
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/*++
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Routine Description:
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This routine is invoked to acquire an I/O buffer of non-standard size.
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If the length requested is less than or equal to 'NH_BUFFER_SIZE',
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a buffer from the shared buffer-queue is returned.
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Otherwise, a buffer is especially allocated for the caller.
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Arguments:
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Length - the length of the buffer required.
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Return Value:
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PNH_BUFFER - the buffer allocated.
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--*/
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{
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PNH_BUFFER Buffer;
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if (Length <= NH_BUFFER_SIZE) {
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return NhAcquireFixedLengthBuffer();
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}
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Buffer = reinterpret_cast<PNH_BUFFER>(
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NH_ALLOCATE(FIELD_OFFSET(NH_BUFFER, Buffer[Length]))
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);
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if (Buffer) { Buffer->Type = NhVariableLengthBufferType; }
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return Buffer;
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} // NhAcquireVariableLengthBuffer
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PNH_BUFFER
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NhDuplicateBuffer(
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PNH_BUFFER Bufferp
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)
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/*++
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Routine Description:
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This routine creates a duplicate of the given buffer,
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including both its data and its control information.
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N.B. Variable-length buffers cannot be duplicated by this routine.
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Arguments:
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Bufferp - the buffer to be duplicated
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Return Value:
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PNH_BUFFER - a pointer to the duplicate
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--*/
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{
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PNH_BUFFER Duplicatep;
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//ASSERT(Bufferp->Type == NhFixedLengthBufferType);
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if (!(Duplicatep = NhAcquireBuffer())) { return NULL; }
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*Duplicatep = *Bufferp;
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return Duplicatep;
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} // NhDuplicateBuffer
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ULONG
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NhInitializeBufferManagement(
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VOID
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)
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/*++
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Routine Description:
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This routine readies the buffer-management for operation.
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Arguments:
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none.
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Return Value:
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ULONG - Win32 status code.
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--*/
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{
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ULONG Error = NO_ERROR;
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InitializeListHead(&NhpBufferQueue);
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NhpBufferQueueLength = 0;
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__try {
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InitializeCriticalSection(&NhpBufferQueueLock);
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} __except(EXCEPTION_EXECUTE_HANDLER) {
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/*
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NhTrace(
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TRACE_FLAG_BUFFER,
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"NhInitializeBufferManagement: exception %d creating lock",
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Error = GetExceptionCode()
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);*/
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}
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return Error;
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} // NhInitializeBufferManagement
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VOID
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NhReleaseBuffer(
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PNH_BUFFER Bufferp
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)
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/*++
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Routine Description:
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This routine is called to release a buffer to the buffer queue.
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It attempts to place the buffer on the queue for re-use, unless
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the queue is full in which case the buffer is immediately freed.
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Arguments:
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Bufferp - the buffer to be released
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Return Value:
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none.
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--*/
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{
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if (NhpBufferQueueLength > NH_MAX_BUFFER_QUEUE_LENGTH ||
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Bufferp->Type != NhFixedLengthBufferType) {
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NH_FREE_BUFFER(Bufferp);
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} else {
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EnterCriticalSection(&NhpBufferQueueLock);
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InsertHeadList(&NhpBufferQueue, &Bufferp->Link);
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LeaveCriticalSection(&NhpBufferQueueLock);
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InterlockedIncrement(&NhpBufferQueueLength);
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}
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} // NhReleaseBuffer
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VOID
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NhShutdownBufferManagement(
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VOID
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)
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/*++
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Routine Description:
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This routine cleans up resources used by the buffer-management module.
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It assumes the list will not be accessed while the clean up is in progress.
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Arguments:
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none.
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Return Value:
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none.
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--*/
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{
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PLIST_ENTRY Link;
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PNH_BUFFER Bufferp;
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while (!IsListEmpty(&NhpBufferQueue)) {
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Link = RemoveHeadList(&NhpBufferQueue);
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Bufferp = CONTAINING_RECORD(Link, NH_BUFFER, Link);
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NH_FREE_BUFFER(Bufferp);
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}
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DeleteCriticalSection(&NhpBufferQueueLock);
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NhpBufferQueueLength = 0;
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} // NhShutdownBufferManagement
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