`_InterlockedCompareExchange` 內建函式

文章
10/12/2023

Microsoft 特定的

進行相互鎖定的比較和交換。

語法

long _InterlockedCompareExchange(
   long volatile * Destination,
   long Exchange,
   long Comparand
);
long _InterlockedCompareExchange_acq(
   long volatile * Destination,
   long Exchange,
   long Comparand
);
long _InterlockedCompareExchange_HLEAcquire(
   long volatile * Destination,
   long Exchange,
   long Comparand
);
long _InterlockedCompareExchange_HLERelease(
   long volatile * Destination,
   long Exchange,
   long Comparand
);
long _InterlockedCompareExchange_nf(
   long volatile * Destination,
   long Exchange,
   long Comparand
);
long _InterlockedCompareExchange_np(
   long volatile * Destination,
   long Exchange,
   long Comparand
);
long _InterlockedCompareExchange_rel(
   long volatile * Destination,
   long Exchange,
   long Comparand
);
char _InterlockedCompareExchange8(
   char volatile * Destination,
   char Exchange,
   char Comparand
);
char _InterlockedCompareExchange8_acq(
   char volatile * Destination,
   char Exchange,
   char Comparand
);
char _InterlockedCompareExchange8_nf(
   char volatile * Destination,
   char Exchange,
   char Comparand
);
char _InterlockedCompareExchange8_rel(
   char volatile * Destination,
   char Exchange,
   char Comparand
);
short _InterlockedCompareExchange16(
   short volatile * Destination,
   short Exchange,
   short Comparand
);
short _InterlockedCompareExchange16_acq(
   short volatile * Destination,
   short Exchange,
   short Comparand
);
short _InterlockedCompareExchange16_nf(
   short volatile * Destination,
   short Exchange,
   short Comparand
);
short _InterlockedCompareExchange16_np(
   short volatile * Destination,
   short Exchange,
   short Comparand
);
short _InterlockedCompareExchange16_rel(
   short volatile * Destination,
   short Exchange,
   short Comparand
);
__int64 _InterlockedCompareExchange64(
   __int64 volatile * Destination,
   __int64 Exchange,
   __int64 Comparand
);
__int64 _InterlockedCompareExchange64_acq(
   __int64 volatile * Destination,
   __int64 Exchange,
   __int64 Comparand
);
__int64 _InterlockedCompareExchange64_HLEAcquire (
   __int64 volatile * Destination,
   __int64 Exchange,
   __int64 Comparand
);
__int64 _InterlockedCompareExchange64_HLERelease(
   __int64 volatile * Destination,
   __int64 Exchange,
   __int64 Comparand
);
__int64 _InterlockedCompareExchange64_nf(
   __int64 volatile * Destination,
   __int64 Exchange,
   __int64 Comparand
);
__int64 _InterlockedCompareExchange64_np(
   __int64 volatile * Destination,
   __int64 Exchange,
   __int64 Comparand
);
__int64 _InterlockedCompareExchange64_rel(
   __int64 volatile * Destination,
   __int64 Exchange,
   __int64 Comparand
);

參數

Destination
[in， out]目的地值的指標。會忽略正負號。

Exchange
[in]Exchange 值。會忽略正負號。

Comparand
[in]要與所 Destination 指向之值比較的值。會忽略正負號。

傳回值

傳回值是指標所 Destination 指向的初始值。

需求

內建	架構	標題
`_InterlockedCompareExchange`, `_InterlockedCompareExchange8`, `_InterlockedCompareExchange16`, `_InterlockedCompareExchange64`	x86、ARM、x64、ARM64	<intrin.h>
`_InterlockedCompareExchange_acq`, `_InterlockedCompareExchange_nf`, `_InterlockedCompareExchange_rel`, `_InterlockedCompareExchange8_acq`, `_InterlockedCompareExchange8_nf`, `_InterlockedCompareExchange8_rel`,`_InterlockedCompareExchange16_acq`, `_InterlockedCompareExchange16_nf`, `_InterlockedCompareExchange16_rel`, `_InterlockedCompareExchange64_acq`, `_InterlockedCompareExchange64_nf`, `_InterlockedCompareExchange64_rel`,	ARM、ARM64	<intrin.h>
`_InterlockedCompareExchange_np`, `_InterlockedCompareExchange16_np`, `_InterlockedCompareExchange64_np`	x64	<intrin.h>
`_InterlockedCompareExchange_HLEAcquire`, `_InterlockedCompareExchange_HLERelease`, `_InterlockedCompareExchange64_HLEAcquire`, `_InterlockedCompareExchange64_HLERelease`	x86、x64	<immintrin.h>

備註

_InterlockedCompareExchange 會使用值對所 DestinationComparand 指向的值執行不可部分完成的比較。如果 Destination 值等於 Comparand 值，則 Exchange 值會儲存在 Destination 所指定的位址。否則，不會執行任何作業。

_InterlockedCompareExchange 提供 Win32 Windows SDK InterlockedCompareExchange 函式的編譯器內建支援。

有數種變化 _InterlockedCompareExchange 會根據所牽涉的資料類型以及使用處理器特定的取得或發行語意而有所不同。

雖然函 _InterlockedCompareExchange 式在 32 位整數值上運作， _InterlockedCompareExchange8 但會以 8 位 long 整數值運作、 _InterlockedCompareExchange16 在 16 位 short 整數值上運作，並以 _InterlockedCompareExchange64 64 位整數值運作。如需 128 位值類似內建函式的詳細資訊，請參閱 _InterlockedCompareExchange128 。

在所有 ARM 平臺上，使用內建和 _acq_rel 尾碼取得和發行語意，例如在重要區段的開頭和結尾。具有（「無柵欄」）尾碼的 ARM 內部 _nf 函數不會作為記憶體屏障。

搭配 _np (「不預先擷取」) 字尾使用內建函式，可避免編譯器插入可能的預先提取作業。

在支援 Hardware Lock Elision (HLE) 指令的 Intel 平台上，搭配 _HLEAcquire 和 _HLERelease 字尾的內建函式會包含對處理器的提示，提示其可以藉由消除硬體中鎖定寫入 (lock write) 的階段以加速效能。如果在不支援 HLE 的平臺上呼叫這些內建函式，則會忽略提示。

這些常式僅以內建函式的形式供您使用。

範例

在下列範例中，_InterlockedCompareExchange 會用於簡單的低層級執行緒同步處理。方法有其限制，作為多執行緒程式設計的基礎;其呈現方式說明內建的一般用法。為求最佳結果，請使用 Windows API。如需多執行緒程式設計的詳細資訊，請參閱撰寫多執行緒 Win32 程式。

// intrinExample.cpp
// compile with: /EHsc /O2
// Simple example of using _Interlocked* intrinsics to
// do manual synchronization
//
// Add [-DSKIP_LOCKING] to the command line to disable
// the locking. This will cause the threads to execute out
// of sequence.

#define _CRT_RAND_S

#include "windows.h"

#include <iostream>
#include <queue>
#include <intrin.h>

using namespace std;

// --------------------------------------------------------------------

// if defined, will not do any locking on shared data
//#define SKIP_LOCKING

// A common way of locking using _InterlockedCompareExchange.
// Refer to other sources for a discussion of the many issues
// involved. For example, this particular locking scheme performs well
// when lock contention is low, as the while loop overhead is small and
// locks are acquired very quickly, but degrades as many callers want
// the lock and most threads are doing a lot of interlocked spinning.
// There are also no guarantees that a caller will ever acquire the
// lock.
namespace MyInterlockedIntrinsicLock
{
    typedef unsigned LOCK, *PLOCK;

#pragma intrinsic(_InterlockedCompareExchange, _InterlockedExchange)

    enum {LOCK_IS_FREE = 0, LOCK_IS_TAKEN = 1};

    void Lock(PLOCK pl)
    {
#if !defined(SKIP_LOCKING)
        // If *pl == LOCK_IS_FREE, it is set to LOCK_IS_TAKEN
        // atomically, so only 1 caller gets the lock.
        // If *pl == LOCK_IS_TAKEN,
        // the result is LOCK_IS_TAKEN, and the while loop keeps spinning.
        while (_InterlockedCompareExchange((long *)pl,
                                           LOCK_IS_TAKEN, // exchange
                                           LOCK_IS_FREE)  // comparand
               == LOCK_IS_TAKEN)
        {
            // spin!
        }
        // This will also work.
        //while (_InterlockedExchange(pl, LOCK_IS_TAKEN) ==
        //                             LOCK_IS_TAKEN)
        //{
        //    // spin!
        //}

        // At this point, the lock is acquired.
#endif
    }

    void Unlock(PLOCK pl) {
#if !defined(SKIP_LOCKING)
        _InterlockedExchange((long *)pl, LOCK_IS_FREE);
#endif
    }
}

// ------------------------------------------------------------------
// Data shared by threads

queue<int> SharedQueue;
MyInterlockedIntrinsicLock::LOCK SharedLock;
int TicketNumber;

// ------------------------------------------------------------------

DWORD WINAPI
ProducerThread(
    LPVOID unused
    )
{
    unsigned int randValue;
    while (1) {
        // Acquire shared data. Enter critical section.
        MyInterlockedIntrinsicLock::Lock(&SharedLock);

        //cout << ">" << TicketNumber << endl;
        SharedQueue.push(TicketNumber++);

        // Release shared data. Leave critical section.
        MyInterlockedIntrinsicLock::Unlock(&SharedLock);

        rand_s(&randValue);
        Sleep(randValue % 20);
    }

    return 0;
}

DWORD WINAPI
ConsumerThread(
    LPVOID unused
    )
{
    while (1) {
        // Acquire shared data. Enter critical section
        MyInterlockedIntrinsicLock::Lock(&SharedLock);

        if (!SharedQueue.empty()) {
            int x = SharedQueue.front();
            cout << "<" << x << endl;
            SharedQueue.pop();
        }

        // Release shared data. Leave critical section
        MyInterlockedIntrinsicLock::Unlock(&SharedLock);

        unsigned int randValue;
        rand_s(&randValue);
        Sleep(randValue % 20);
    }
    return 0;
}

int main(
    void
    )
{
    const int timeoutTime = 500;
    int unused1, unused2;
    HANDLE threads[4];

    // The program creates 4 threads:
    // two producer threads adding to the queue
    // and two consumers taking data out and printing it.
    threads[0] = CreateThread(NULL,
                              0,
                              ProducerThread,
                              &unused1,
                              0,
                              (LPDWORD)&unused2);

    threads[1] = CreateThread(NULL,
                              0,
                              ConsumerThread,
                              &unused1,
                              0,
                              (LPDWORD)&unused2);

    threads[2] = CreateThread(NULL,
                              0,
                              ProducerThread,
                              &unused1,
                              0,
                              (LPDWORD)&unused2);

    threads[3] = CreateThread(NULL,
                              0,
                              ConsumerThread,
                              &unused1,
                              0,
                              (LPDWORD)&unused2);

    WaitForMultipleObjects(4, threads, TRUE, timeoutTime);

    return 0;
}

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END Microsoft 特定的

另請參閱

_InterlockedCompareExchange128
_InterlockedCompareExchangePointer 內建函式
 編譯器內建函式
 關鍵字
 與 x86 編譯器衝突

分享方式：

`_InterlockedCompareExchange` 內建函式

語法

參數

傳回值

需求

備註

範例

另請參閱

意見反映

意見反映

更多資源

分享方式：

_InterlockedCompareExchange 內建函式

語法

參數

傳回值

需求

備註

範例

另請參閱

意見反映

意見反映

更多資源

`_InterlockedCompareExchange` 內建函式