C++中使用内存映射文件存取struct，并用指针访问

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#include <iostream>#include <Windows.h>#define OK 0#define MMF_FILE_SIZE (1024*512)const char* mmf_file_name = "d:\\mmf.txt";const char* mmf_share_name = "testmmf";//定义内存映射文件相关的全局变量HANDLE file_handle      = NULL;HANDLE mfile_handle     = NULL;void* mview_ptr         = NULL;//打开内存映射文件和映射视图int open_mmf();//关闭内存映射文件相关资源void close_mmf();//定义指针struct Foo{    unsigned int id;    char code[30];    char name[30];};using namespace std;int main(){    int open_status = open_mmf();    if(open_status){        cout<<"打开内存映射文件出错，错误号："<<open_status<<endl;    }else{        cout<<"成功打开了内存映射文件"<<endl;        Foo* foo_ptr = (Foo*)mview_ptr;        Foo foo;        const size_t foo_size = sizeof(Foo);        int count = MMF_FILE_SIZE / foo_size - 1;        for(int i=0;i<=count;i++){            foo.id = i+1;            sprintf(foo.name,"+%d",foo.id);            sprintf(foo.code,"-%d",foo.id);            memcpy(foo_ptr+i,&foo,foo_size);            printf("copy %d\r",i);        }        cout<<"保存数据完毕"<<endl;        cout<<"尝试读取数据"<<endl;        for(int i=0;i<=count;i++){            foo = *(foo_ptr+i);            cout<<"foo:"<<foo.id<<","<<foo.code<<","<<foo.name<<endl;        }        cout<<"读取数据完毕"<<endl;    }    system("pause");    close_mmf();    return EXIT_SUCCESS;}//打开内存映射文件int open_mmf(){    file_handle = CreateFile(mmf_file_name,        GENERIC_ALL,        FILE_SHARE_READ|FILE_SHARE_WRITE,        NULL,        OPEN_ALWAYS,        FILE_FLAG_SEQUENTIAL_SCAN,        NULL);    if(INVALID_HANDLE_VALUE == file_handle){        return GetLastError();    }    mfile_handle = CreateFileMapping(file_handle,        NULL,        PAGE_READWRITE,        0,        MMF_FILE_SIZE,        mmf_share_name);    if(INVALID_HANDLE_VALUE == mfile_handle){        return GetLastError();    }    mview_ptr = MapViewOfFile(mfile_handle,        FILE_MAP_ALL_ACCESS,        0,        0,        MMF_FILE_SIZE);    return OK;}//释放内存映射文件占用的资源。void close_mmf(){    if(NULL != mview_ptr){        UnmapViewOfFile(mview_ptr);        mview_ptr = NULL;    }    if(NULL != mfile_handle){        CloseHandle(mfile_handle);        mfile_handle = NULL;    }    if(NULL != file_handle){        CloseHandle(file_handle);        file_handle = NULL;    }}

本文转自：(http://www.cnblogs.com/yukaizhao/archive/2011/05/19/memorymapfile_struct.html)

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