第21章 线程局部存储

DWORD g_dwTlsIndex; //假设这个全局变量是通过TlsAlloc函数来初始化的

void MyFunction(PSOMESTRUCT PSomeStruct){

    if (pSomeStruct != NULL){
        //调用者正在启用该函数，就像strok函数第一次传入非NULL，
        //以后传为NULL

        //检查是否己经为数据分配存储空间
        if (TlsGetValue(g_dwTlsIndex) == NULL)
            //线程第一次调用该函数时，该空间尚未分配
            //TlsAlloc函数返回之前，会将进程中所有线程的g_dwTlsIndex元素
            //清零，以保证这句代码不会出错非空的现象！

            //通过TLS能保证分配的空间只与调用线程相关联
            TlsSetValue(g_dwTlsIndex,  
                        HeapAlloc(GetProcessHeap(), 0, sizeof(*pSomeStruct));
        }

        //将传入的pSomeStruct数据保存刚才那个只与调用线程相关的存储空间中
        memcpy(TlsGetValue(g_dwTlsIndex), pSomeStruct, sizeof(*pSomeStruct));
    } else{ 
        //调用者己经第二次（或以上）调用该函数，会传入NULL参数

        //取出数据
        pSomeStruct = (PSOMESTRUCT)TlsGetValue(g_dwTlsIndex);

        //以下可以开始pSomeStruct这个数据了。
        ...
    }
}

/************************************************************************
Module: DllTls.h
************************************************************************/
#pragma  once
#include <windows.h>

#ifdef DLLTLS_EXPORT
//DLLTLS_EXPORT必须在Dll源文件包含该头件前被定义
#define DLLTLSAPI extern "C" __declspec(dllexport)
//本例中所有的函数和变量都会被导出
#else
#define DLLTLSAPI extern "C" __declspec(dllimport)
#endif

//定义要导出的函数的原型
DLLTLSAPI VOID* GetThreadBuf();
DLLTLSAPI UINT GetThreadBufSize();

#include <tchar.h>
#include <windows.h>
#include <strsafe.h>
#include <locale.h>

//在这个DLL源文件定义要导出的函数和变量
#define DLLTLS_EXPORT   //这个源文件中须定义这个宏，以告诉编译器函数要
//__declspect(dllexport)，这个宏须在包含MyLib.h
//之前被定义

#include "DllTls.h"

#define GRS_ALLOC(sz)    HeapAlloc(GetProcessHeap(),0,sz)
#define GRS_CALLOC(sz)   HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,sz)
#define GRS_SAFEFREE(p)  if(NULL!=p){HeapFree(GetProcessHeap(),0,p);p=NULL;}

static DWORD g_dwTLS = 0;
static UINT g_nBufSize = 256;

BOOL APIENTRY DllMain(HANDLE hDllHandle, DWORD dwReason, LPVOID lpreserved){
    switch (dwReason)
    {
    case DLL_PROCESS_ATTACH:
        {
            _tsetlocale(LC_ALL, _T("chs"));
            g_dwTLS = TlsAlloc();
            if (TLS_OUT_OF_INDEXES == g_dwTLS){
                _tprintf(_T("为进程[ID:0x%X]分配TLS索引失败！n"),
                         GetCurrentProcessId());
                return FALSE;
            }

            _tprintf(_T("为进程[ID:0x%X]分配TLS索引:%u！n"),
                     GetCurrentProcessId(),g_dwTLS);
        }
        break;

    case DLL_THREAD_ATTACH:
        {
            PVOID pThdData = GRS_CALLOC(g_nBufSize);

            if (!TlsSetValue(g_dwTLS,pThdData)){
                _tprintf(_T("为线程[ID:0x%X]设置TLS索引[%u]变量[0x%08X]失败！n"),
                         GetCurrentThreadId(), g_dwTLS,pThdData);
                GRS_SAFEFREE(pThdData);
                return FALSE;
            }

            _tprintf(_T("为线程[ID:0x%X]设置TLS索引[%u]变量[0x%08X]！n"),
                     GetCurrentThreadId(), g_dwTLS, pThdData);
        }
        break;

    case DLL_THREAD_DETACH:
        {
            PVOID pThdData = TlsGetValue(g_dwTLS);

            if (!pThdData){
                _tprintf(_T("为线程[ID:0x%X]获取TLS索引[%u]变量[0x%08X]失败！n"),
                         GetCurrentThreadId(), g_dwTLS, pThdData);
                return FALSE;
            }

            _tprintf(_T("为线程[ID:0x%X]获取TLS索引[%u]变量[0x%08X]并销毁！n"),
                     GetCurrentThreadId(), g_dwTLS, pThdData);
            GRS_SAFEFREE(pThdData);
        }
        break;

    case DLL_PROCESS_DETACH:
        {
            _tprintf(_T("释放进程[ID:0x%X]TLS索引[%u]n"),
                 GetCurrentProcessId(), g_dwTLS);
            TlsFree(g_dwTLS);
        }
        break;
    }

    return TRUE;
}

VOID* GetThreadBuf()
{
    return TlsGetValue(g_dwTLS);
}

UINT GetThreadBufSize(){
    return g_nBufSize;
}

#include <windows.h>
#include <tchar.h>
#include <strsafe.h>
#include <locale.h>
#include "../../Chap21/21_DLLTls/DllTls.h"

#pragma comment(lib,"../../Debug/21_DLLTls.lib")

#define GRS_CREATETHREAD(Fun,Param) CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)Fun,Param,0,NULL)

DWORD WINAPI ThreadProc(LPVOID pvParam){
    TCHAR* pTlsBuf = (TCHAR*)GetThreadBuf();
    UINT nSize = GetThreadBufSize();
    if (NULL !=pTlsBuf && 0 != nSize){
        _tprintf(_T("线程[0x%X]取得缓冲区[地址:0x%08X 大小(字节):%u]，写入数据n"),
                 GetCurrentThreadId(),pTlsBuf,nSize);
        StringCchPrintf(pTlsBuf, nSize / sizeof(TCHAR), _T("ID：0x%X"), GetCurrentThreadId());
        Sleep(1000);
        _tprintf(_T("线程[0x%X]取得缓冲区[地址:0x%08X 大小(字节):%u]，写入的数据为[%s]n"),
                 GetCurrentThreadId(), pTlsBuf, nSize,pTlsBuf);
    }
    _tprintf(_T("线程[0x%X]退出n"),GetCurrentThreadId());
    return 0;
}

#define THREADCNT  2
int _tmain(){

    _tsetlocale(LC_ALL, _T("chs"));

    HANDLE phThread[THREADCNT] = {};
    for (int i = 0; i < THREADCNT; i++){
        phThread[i] = GRS_CREATETHREAD(ThreadProc, NULL);
    }

    WaitForMultipleObjects(THREADCNT, phThread, TRUE, INFINITE);
    for (int i = 0; i < THREADCNT;i++){
        CloseHandle(phThread[i]);
    }
    _tsystem(_T("PAUSE"));
    return 0;
}