//读者与写者问题
#include
#include
#include
#ifdef _MT
//设置控制台输出颜色
BOOL SetConsoleColor(WORD wAttributes)
{
HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
if (hConsole == INVALID_HANDLE_VALUE)
return FALSE;
return SetConsoleTextAttribute(hConsole, wAttributes);
}
const int READER_NUM = 5; //读者个数
//关键段和事件
CRITICAL_SECTION g_cs, g_cs_writer_count;
HANDLE g_hEventWriter, g_hEventNoReader;
int g_nReaderCount;
//读者线程输出函数(变参函数的实现)
void ReaderPrintf(char *pszFormat, ...)
{
va_list pArgList;
va_start(pArgList, pszFormat);
EnterCriticalSection(&g_cs);
vfprintf(stdout, pszFormat, pArgList);
LeaveCriticalSection(&g_cs);
va_end(pArgList);
}
//读者线程函数
unsigned int __stdcall ReaderThreadFun(PVOID pM)
{
ReaderPrintf(" 编号为%d的读者进入等待中...\n", GetCurrentThreadId());
//等待写者完成
WaitForSingleObject(g_hEventWriter, INFINITE);
//读者个数增加
EnterCriticalSection(&g_cs_writer_count);
g_nReaderCount++;
if (g_nReaderCount == 1)
ResetEvent(g_hEventNoReader);
LeaveCriticalSection(&g_cs_writer_count);
//读取文件
ReaderPrintf("编号为%d的读者开始读取文件...\n", GetCurrentThreadId());
Sleep(rand() % 100);
//结束阅读,读者个数减小,空位增加
ReaderPrintf(" 编号为%d的读者结束读取文件\n", GetCurrentThreadId());
//读者个数减少
EnterCriticalSection(&g_cs_writer_count);
g_nReaderCount--;
if (g_nReaderCount == 0)
SetEvent(g_hEventNoReader);
LeaveCriticalSection(&g_cs_writer_count);
return 0;
}
//写者线程输出函数
void WriterPrintf(char *pszStr)
{
EnterCriticalSection(&g_cs);
SetConsoleColor(FOREGROUND_GREEN);
printf(" %s\n", pszStr);
SetConsoleColor(FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_BLUE);
LeaveCriticalSection(&g_cs);
}
//写者线程函数
unsigned int __stdcall WriterThreadFun(PVOID pM)
{
WriterPrintf("写者线程进入等待中...");
//等待读文件的读者为零
WaitForSingleObject(g_hEventNoReader, INFINITE);
//标记写者正在写文件
ResetEvent(g_hEventWriter);
//写文件
WriterPrintf(" 写者开始写文件.....");
Sleep(rand() % 100);
WriterPrintf(" 写者结束写文件");
//标记写者结束写文件
SetEvent(g_hEventWriter);
return 0;
}
int main()
{
printf(" 读者写者问题\n");
//初始化事件和信号量
InitializeCriticalSection(&g_cs);
InitializeCriticalSection(&g_cs_writer_count);
//手动置位,初始已触发
g_hEventWriter = CreateEvent(NULL, TRUE, TRUE, NULL);
g_hEventNoReader = CreateEvent(NULL, FALSE, TRUE, NULL);
g_nReaderCount = 0;
int i;
HANDLE hThread[READER_NUM + 1];
//先启动二个读者线程
for (i = 1; i <= 2; i++)
hThread[i] = (HANDLE)_beginthreadex(NULL, 0, ReaderThreadFun, NULL, 0, NULL);
//启动写者线程
hThread[0] = (HANDLE)_beginthreadex(NULL, 0, WriterThreadFun, NULL, 0, NULL);
Sleep(50);
//最后启动其它读者结程
for ( ; i <= READER_NUM; i++)
hThread[i] = (HANDLE)_beginthreadex(NULL, 0, ReaderThreadFun, NULL, 0, NULL);
WaitForMultipleObjects(READER_NUM + 1, hThread, TRUE, INFINITE);
for (i = 0; i < READER_NUM + 1; i++)
CloseHandle(hThread[i]);
//销毁事件和信号量
CloseHandle(g_hEventWriter);
CloseHandle(g_hEventNoReader);
DeleteCriticalSection(&g_cs);
DeleteCriticalSection(&g_cs_writer_count);
return 0;
}
