最近一直在学习OBS源码，遇到很多多线程的知识，也算是恶补了一下之前没搞明白一直没机会用的信号量。
一、相关的函数和头文件介绍

//头文件
#include <windows.h>

//创建信号量API
HANDLE WINAPI CreateSemaphore(
 _In_opt_ LPSECURITY_ATTRIBUTES lpSemaphoreAttributes,//指向SECURITY_ATTRIBUTES的指针;
 _In_     LONG                  lInitialCount,          //信号量对象的初始值；
 _In_     LONG                  lMaximumCount,  //信号量对象的最大值，这个值必须大于0;
 _In_opt_ LPCTSTR               lpName                 //信号量对象的名称；
);

//等待信号量API
DWORD WINAPI WaitForSingleObject(
  _In_ HANDLE hHandle,          //信号量对象句柄
  _In_ DWORD  dwMilliseconds    //等待信号量时间，INFINET代表永久等待；
);
返回值：
WAIT_ABANDONED(0x00000080L) 表示拥有信号量的线程再终止前未释放该信号量；
WAIT_OBJECT_0(0x00000000L)  表示等到了信号量；
WAIT_TIMEOUT(0x00000102L)   表示等待超时；
WAIT_FAILED((DWORD)0xFFFFFFFF)  表示该函数执行失败，用GetLastError()得到错误码；  

//释放信号量句柄
BOOL WINAPI ReleaseSemaphore(
  _In_      HANDLE hSemaphore,         //信号量对象句柄；
  _In_      LONG   lReleaseCount,      //信号量释放的值，必须大于0；
  _Out_opt_ LPLONG lpPreviousCount     //前一次信号量值的指针，不需要可置为空；
);
返回值：成功返回非0；

二、win32平台下的demo

//#include "stdafx.h"
#include<windows.h>
#include<iostream>
using namespace std;

int number = 1; //定义全局变量
HANDLE hSemaphore;  //定义信号量句柄

unsigned long __stdcall ThreadProc1(void* lp)
{
    long count;
    while (number < 100)
    {
        WaitForSingleObject(hSemaphore, INFINITE);  //等待信号量为有信号状态
        cout << "thread 1 :" << number << endl;
        ++number;
        Sleep(100);
        ReleaseSemaphore(hSemaphore, 1, &count);
    }

    return 0;
}

unsigned long __stdcall ThreadProc2(void* lp)
{
    long count;
    while (number < 100)
    {
        WaitForSingleObject(hSemaphore, INFINITE);  //等待信号量为有信号状态
        cout << "thread 2 :" << number << endl;
        ++number;
        Sleep(100);
        ReleaseSemaphore(hSemaphore, 1, &count);
    }

    return 0;
}

int main()
{
    LPCWSTR lpName = L"mm";
    hSemaphore = CreateSemaphore(NULL, 1, 100, lpName);

    CreateThread(NULL, 0, ThreadProc1, NULL, 0, NULL);
    CreateThread(NULL, 0, ThreadProc2, NULL, 0, NULL);

    Sleep(10 * 1000);

    system("pause");
    return 0;
}

三、运行结果

thread 1 :1
thread 2 :2
thread 1 :3
thread 2 :4
thread 1 :5
thread 2 :6
thread 1 :7
thread 2 :8
thread 1 :9
thread 2 :10
thread 1 :11
thread 2 :12
thread 1 :13
thread 2 :14
thread 1 :15
thread 2 :16
thread 1 :17
thread 2 :18
thread 1 :19
thread 2 :20
thread 1 :21
thread 2 :22
thread 1 :23
thread 2 :24
thread 1 :25
thread 2 :26
thread 1 :27
thread 2 :28
thread 1 :29
thread 2 :30
thread 1 :31
thread 2 :32
thread 1 :33
thread 2 :34
thread 1 :35
thread 2 :36
thread 1 :37
thread 2 :38
thread 1 :39
thread 2 :40
thread 1 :41
thread 2 :42
thread 1 :43
thread 2 :44
thread 1 :45
thread 2 :46
thread 1 :47
thread 2 :48
thread 1 :49
thread 2 :50
thread 1 :51
thread 2 :52
thread 1 :53
thread 2 :54
thread 1 :55
thread 2 :56
thread 1 :57
thread 2 :58
thread 1 :59
thread 2 :60
thread 1 :61
thread 2 :62
thread 1 :63
thread 2 :64
thread 1 :65
thread 2 :66
thread 1 :67
thread 2 :68
thread 1 :69
thread 2 :70
thread 1 :71
thread 2 :72
thread 1 :73
thread 2 :74
thread 1 :75
thread 2 :76
thread 1 :77
thread 2 :78
thread 1 :79
thread 2 :80
thread 1 :81
thread 2 :82
thread 1 :83
thread 2 :84
thread 1 :85
thread 2 :86
thread 1 :87
thread 2 :88
thread 1 :89
thread 2 :90
thread 1 :91
thread 2 :92
thread 1 :93
thread 2 :9请按任意键继续. . . 4
thread 1 :95
thread 2 :96
thread 1 :97
thread 2 :98
thread 1 :99
thread 2 :100