TLS

为了避免线程同步导致的效率问题，微软发明了TLS，即线程局部存储

1. 静态使用，操作系统会保证每个TLS变量的下标都一样
2. dll程序不能静态使用，因为dll中的代码可以在任何线程中运行，所以下标就不能固定了，而静态使用是下标一定是固定的

动态使用

int g_Number = 0;

DWORD WINAPI WordThread(LPVOID lpParameter) {
    DWORD index=TlsAlloc();

    TlsSetValue(index, 0);

    for (int i = 0;i < 100000000; i++) {
        TlsSetValue(index, LPVOID((int)TlsGetValue(index) + 1)); //g_Number++
    }

    //TlsFree(index);  释放了里面存储的值就是0了

    return (int)TlsGetValue(index);
}

#define MAX_THREADS  2


int main() {
  DWORD Start = GetTickCount();
  HANDLE hThreads[MAX_THREADS] = {0};
  for (int i = 0; i < MAX_THREADS; i++) {
    hThreads[i] = CreateThread(NULL, 0, WordThread, NULL, 0, NULL);
  }

  WaitForMultipleObjects(MAX_THREADS, hThreads, TRUE, -1);
  DWORD End = GetTickCount();

  DWORD sum = 0;
  for (int i = 0; i < MAX_THREADS; i++) {
    DWORD dwExitCode = 0;
    (int)GetExitCodeThread(hThreads[i], &dwExitCode);
    sum += dwExitCode;
  }

  printf("time:%d g_Number:%d\n", End - Start, sum);

  return 0;
}

静态使用

 1 __declspec(thread)  int g_Number = 0;
 2 
 3 DWORD WINAPI WordThread(LPVOID lpParameter) {
 4 
 5     for (int i = 0;i < 100000000; i++) {
 6         g_Number++；
 7     }
 8 
 9     return g_Number;
10 }

TLS回调函数

VOID NTAPI TlsInit2(PVOID DllHandle, DWORD Reason, PVOID Reserved) {

  if (Reason == DLL_PROCESS_ATTACH) {
    printf("TlsInit2 DLL_PROCESS_ATTACH\n");
  }
  else if (Reason == DLL_THREAD_ATTACH) {
    printf("TlsInit2 DLL_THREAD_ATTACH\n");
  }
  else if (Reason == DLL_THREAD_DETACH) {
    printf("TlsInit2 DLL_THREAD_DETACH\n");
  }
  else if (Reason == DLL_PROCESS_DETACH) {
    printf("TlsInit2 DLL_PROCESS_ATTACH\n");
  }
}

#pragma data_seg(".CRT$XLB")   //最后一个字符不固定，但不能是A
PIMAGE_TLS_CALLBACK g_Callbacks[] = {
  &TlsAntiDebug,   //&是标准写法，不加上的话换个编译器可能就报错了
   &TlsInit1,
   &TlsInit2, 
   NULL
};
#pragma data_seg()