读书笔记——Windows核心编程(8)Interlocked单向链式栈

SLists使用了无锁算法来保证原子同步,以提升系统性能,避免了诸如优先级挂和互锁的问题。

注意:所有的链表项必须对齐到MEMORY_ALLOCATION_ALIGNMENT。否则会出现奇葩的错误。

(PS:看英文MSDN的API解释,我感觉这是从前插又从前取,是个栈的样子。)

InitializeSListHead创建一个空栈

void WINAPI InitializeSListHead(
  __inout  PSLIST_HEADER ListHead//SLIST_HEADER类型的链头,供系统使用。
);
InterlockedFlushSList清空(感觉这个返回值没什么用的样子,难道可以先全部得到,然后根据链表中元素数量再一个一个地用?求解释。)

PSLIST_ENTRY WINAPI InterlockedFlushSList(
  __inout  PSLIST_HEADER ListHead//创建空栈时用的那个链头
);
InterlockedPushEntrySList在头添加(区别于从尾部添加),返回值为之前的第一项,如果之前为空链,则返回NULL。
PSLIST_ENTRY WINAPI InterlockedPushEntrySList(
  __inout  PSLIST_HEADER ListHead,//创建空栈时用的那个链头
  __inout  PSLIST_ENTRY ListEntry//插入项
);
InterlockedPopEntrySList在头取出(区别于从尾部取出),返回值就是取的那个项的指针,如果之前为空链,则返回NULL。
PSLIST_ENTRY WINAPI InterlockedPopEntrySList(
  __inout  PSLIST_HEADER ListHead
);
QueryDepthSList返回元素的数量
USHORT WINAPI QueryDepthSList(
  __in  PSLIST_HEADER ListHead
);

微软的MSDN上有个例子,我复制了下来,链接: http://msdn.microsoft.com/en-us/library/windows/desktop/ms686962。代码如下。

#include <windows.h>
#include <malloc.h>
#include <stdio.h>

// Structure to be used for a list item; the first member is the 
// SLIST_ENTRY structure, and additional members are used for data.
// Here, the data is simply a signature for testing purposes. 


typedef struct _PROGRAM_ITEM {
    SLIST_ENTRY ItemEntry;
    ULONG Signature; 
} PROGRAM_ITEM, *PPROGRAM_ITEM;

int main( )
{
    ULONG Count;
    PSLIST_ENTRY pFirstEntry, pListEntry;
    PSLIST_HEADER pListHead;
    PPROGRAM_ITEM pProgramItem;

    // Initialize the list header to a MEMORY_ALLOCATION_ALIGNMENT boundary.
    pListHead = (PSLIST_HEADER)_aligned_malloc(sizeof(SLIST_HEADER),
       MEMORY_ALLOCATION_ALIGNMENT);
    if( NULL == pListHead )
    {
        printf("Memory allocation failed.\n");
        return -1;
    }
    InitializeSListHead(pListHead);

    // Insert 10 items into the list.
    for( Count = 1; Count <= 10; Count += 1 )
    {
        pProgramItem = (PPROGRAM_ITEM)_aligned_malloc(sizeof(PROGRAM_ITEM),
            MEMORY_ALLOCATION_ALIGNMENT);
        if( NULL == pProgramItem )
        {
            printf("Memory allocation failed.\n");
            return -1;
        }
        pProgramItem->Signature = Count;
        pFirstEntry = InterlockedPushEntrySList(pListHead, 
                       &(pProgramItem->ItemEntry)); 
    }

    // Remove 10 items from the list and display the signature.
    for( Count = 10; Count >= 1; Count -= 1 )
    {
        pListEntry = InterlockedPopEntrySList(pListHead);

        if( NULL == pListEntry )
        {
            printf("List is empty.\n");
            return -1;
        }
  
        pProgramItem = (PPROGRAM_ITEM)pListEntry;
        printf("Signature is %d\n", pProgramItem->Signature);

    // This example assumes that the SLIST_ENTRY structure is the 
    // first member of the structure. If your structure does not 
    // follow this convention, you must compute the starting address 
    // of the structure before calling the free function.

        _aligned_free(pListEntry);
    }

    // Flush the list and verify that the items are gone.
    pListEntry = InterlockedFlushSList(pListHead);
    pFirstEntry = InterlockedPopEntrySList(pListHead);
    if (pFirstEntry != NULL)
    {
        printf("Error: List is not empty.\n");
        return -1;
    }

    _aligned_free(pListHead);

    return 1;
}

这里略微解释下吧!

微软自己定义的那个结构体PROGRAM_ITEM的第一项是SLIST_ENTRY类型的变量。

往InterlockedPushEntrySList和InterlockedPopEntrySList传递时传递的是自定义结构体的第一项。

结构体的地址和它的第一项的地址是同一个。

转载请注明出处http://blog.csdn.net/wlsgzl/article/details/17021551

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