Critical Sections
并不是核心對象。因此沒有
handle
這樣的東西。它和核心對象不同，它存在于進程的內存空間中。你不需要使用想“
Create
”這樣的
API
函數獲得一個
critical section handle
。你應該做的是將一個類型為
CRITICAL_SECTION
的局部變量初始化，方法是調用
InitializeCriticalSection():
The InitializeCriticalSection function initializes a critical section object.
VOID InitializeCriticalSection(
??? LPCRITICAL_SECTION lpCriticalSection ?????????????? // address of critical section object?
?? );?????????
?Parameters
lpCriticalSection
Points to the critical section object.
Return Values
This function does not return a value.
當你用畢
critical section
時，你必須調用
DeleteCriticalSection()
清除它。這個函數并沒有“釋放對象”的意義在里頭，不要把它和
C++
的
delete
運算符混淆了。
The DeleteCriticalSection function releases all resources used by an unowned critical section object.
VOID DeleteCriticalSection(
??? LPCRITICAL_SECTION lpCriticalSection ?????????????? // pointer to critical section object?
?? );?????????
Parameters
lpCriticalSection
Points to the critical section object.
Return Values
This function does not return a value.
一旦
critical section
被初始化，每一個線程就可以進入其中——只要他通過了
EnterCriticalSection()
這一關：
The EnterCriticalSection function waits for ownership of the specified critical section object. The function returns when the calling thread is granted ownership.
VOID EnterCriticalSection(
??? LPCRITICAL_SECTION lpCriticalSection ?????????????? // pointer to critical section object?
?? );?????????
Parameters
lpCriticalSection
Points to the critical section object.
Return Values
This function does not return a value.
當線程準備好離開
critical section
的時候，他必須調用
LeaveCriticalSection():
The LeaveCriticalSection function releases ownership of the specified critical section object.
VOID LeaveCriticalSection(
??? LPCRITICAL_SECTION lpCriticalSection ?????????????? // address of critical section object?
?? );?????????
Parameters
lpCriticalSection
Points to the critical section object.
Return Values
This function does not return a value.
下面是一個很簡單的使用例子，只是為了演示如何使用，沒有其它目的：
#include
<stdio.h>
#include
<windows.h>
const
int numThreads = 3;
//?¨ò?ò???critical section±?á?
CRITICAL_SECTION gCS;
?
DWORD WINAPI helloFunc(LPVOID pArg)
{
??????
//??è?critical section
?????? EnterCriticalSection(&gCS);
??????
??????
int num = (int) pArg;
?????? printf("Hello Thread %d\n", num);
?
??????
//??3ìó?±?￡???μ?μ÷ó?′?oˉê?à??acritical section?￡￡¨Enter**ó?Leave**μ?ê?á?òa????￡?
?????? LeaveCriticalSection(&gCS);
??????
return 0;
}
?
int
main()
{?????
??????
//3?ê??ˉcritical section
?????? InitializeCriticalSection(&gCS);
?????? HANDLE hThread[numThreads];
?????? DWORD begin = GetTickCount();
?
??????
for (int i = 0; i < numThreads; i++)
?????? {
????????????? hThread[i] = CreateThread(NULL, 0, helloFunc, (LPVOID)i, 0, NULL);
?????? }
?
?????? WaitForMultipleObjects(numThreads, hThread, TRUE, INFINITE);
?????? DWORD elapse = GetTickCount() - begin;
?????? printf("elapse time: %d\n", elapse);
?
??????
//?ùó???3ì?′??íê±?oó￡?deleteμ?critical section
?????? DeleteCriticalSection(&gCS);
??????
return 0;
}
?
?