C与Java哪个难，java线程本地存储_[并发并行]_[C/C++]_[使用线程本地存储Thread Local Storage(TLS)-win32和pth

场景:

C与Java哪个难，1.  需要统计某个线程的对象上创建的个数.

2. 当创建的堆空间需要根据线程需要创建和结束时销毁时.

国二C简单还是java简单？3. 因为范围是线程只能看到自己的存储数据，所以不需要临界区或互斥量来维护自己的堆内存. 加入如果用全局std::map实现,那么必须在put和get时加锁，这是很损耗资源的.

4. 可以用在维护一个连接，比如socket,database连接.

说明:

1. Java也有自己的线程本地存储ThreadLocal

例子test_TSL.cpp:

#include "stdafx.h"

#include

#include

#include

#include

#include

#include "pthread.h"

#define THREADCOUNT 4

DWORD dwTlsIndex;

VOID ErrorExit(const char*);

static pthread_barrier_t barrier = NULL;

static pthread_once_t random_is_initialized = PTHREAD_ONCE_INIT;

static pthread_key_t key;

VOID CommonFunc(VOID)

{

LPVOID lpvData;

// Retrieve a data pointer for the current thread.

lpvData = TlsGetValue(dwTlsIndex);

if ((lpvData == 0) && (GetLastError() != ERROR_SUCCESS))

ErrorExit("TlsGetValue error");

// Use the data stored for the current thread.

int64_t* value = (int64_t*)lpvData;

printf("common: thread %d: lpvData=%lx : value=%lld\n",

GetCurrentThreadId(), lpvData,*value);

Sleep(5000);

}

DWORD WINAPI ThreadFunc(VOID)

{

LPVOID lpvData;

// Initialize the TLS index for this thread.

lpvData = (LPVOID) LocalAlloc(LPTR, 8);

if (! TlsSetValue(dwTlsIndex, lpvData))

ErrorExit("TlsSetValue error");

int64_t* value = (int64_t*)lpvData;

*value = GetCurrentThreadId();

printf("thread %d: lpvData=%lx\n", GetCurrentThreadId(), lpvData);

CommonFunc();

// Release the dynamic memory before the thread returns.

lpvData = TlsGetValue(dwTlsIndex);

if (lpvData != 0)

LocalFree((HLOCAL) lpvData);

return 0;

}

void TestWin32TLS()

{

DWORD IDThread;

HANDLE hThread[THREADCOUNT];

int i;

// Allocate a TLS index.

if ((dwTlsIndex = TlsAlloc()) == TLS_OUT_OF_INDEXES)

ErrorExit("TlsAlloc failed");

//1. 注意,这个dwTlsIndex 并不是从0开始.

printf("dwTlsIndex %ld\n",dwTlsIndex);

// Create multiple threads.

for (i = 0; i < THREADCOUNT; i++)

{

hThread[i] = CreateThread(NULL, // default security attributes

0, // use default stack size

(LPTHREAD_START_ROUTINE) ThreadFunc, // thread function

NULL, // no thread function argument

0, // use default creation flags

&IDThread); // returns thread identifier

// Check the return value for success.

if (hThread[i] == NULL)

ErrorExit("CreateThread error\n");

}

for (i = 0; i < THREADCOUNT; i++)

WaitForSingleObject(hThread[i], INFINITE);

TlsFree(dwTlsIndex);

}

void CommonFuncPthread(void)

{

void* lpvData = pthread_getspecific(key);

int64_t* value = (int64_t*)lpvData;

printf("common: thread %d: lpvData=%lx : value=%lld\n",

GetCurrentThreadId(), lpvData,*value);

}

void* StartPthread(void* data)

{

int64_t *buf = (int64_t*)malloc(256);

*buf = GetCurrentThreadId();

pthread_setspecific(key, buf);

CommonFuncPthread();

free(buf);

pthread_barrier_wait(&barrier);

return NULL;

}

//1.只调用一次,可以放在随意一个work thread执行函数里都可以,会随机找一个线程执行.

//2.类似win32的DLL_PROCESS_ATTACH只执行一次.

void TestPthreadTLS()

{

pthread_key_create(&key, NULL);

pthread_barrier_init(&barrier,NULL, THREADCOUNT + 1);

for(int i = 0; i< THREADCOUNT; ++i)

{

pthread_t t;

pthread_create(&t,NULL,StartPthread,NULL);

pthread_detach(t);

}

//1.等待其他线程执行完.

pthread_barrier_wait(&barrier);

pthread_key_delete(key);

}

DWORD main(VOID)

{

//1.win32TLS

printf("TestWin32TLS\n");

TestWin32TLS();

//1.pthread TLS

printf("TestPthreadTLS\n");

TestPthreadTLS();

return 0;

}

VOID ErrorExit (const char* lpszMessage)

{

fprintf(stderr, "%s\n", lpszMessage);

ExitProcess(0);

}

.

输出:

TestWin32TLS

dwTlsIndex 26

thread 8452: lpvData=714f50

common: thread 8452: lpvData=714f50 : value=8452

thread 8460: lpvData=7153d0

common: thread 8460: lpvData=7153d0 : value=8460

thread 8456: lpvData=715610

common: thread 8456: lpvData=715610 : value=8456

thread 8464: lpvData=715190

common: thread 8464: lpvData=715190 : value=8464

TestPthreadTLS

common: thread 8520: lpvData=3b4eb0 : value=8520

common: thread 8512: lpvData=3b4ff0 : value=8512

common: thread 8516: lpvData=3b4eb0 : value=8516

common: thread 8524: lpvData=3b4ff0 : value=8524

参考: