苹果电脑上不了网:C++使用内存映射文件入门

本文介绍如何使用CreateFileMapping,MapViewOfFile创建内存映射文件，如何向内存映射文件中写入数据，读取数据。

view sourceprint? #include #include #include #include #define BAD_POS 0xFFFFFFFF // returned by SetFilePointer and GetFileSize #define SUCCESS 0 using namespace std; typedef DWORD mmf_share_mode; typedef DWORD mmf_access_mode; typedef DWORD mmf_flags; int main(){ cout<<"create memorymapfile..."< const char* shared_name = "testMmf"; const char* file_name = "d:\\testMmf.mmf"; const DWORD mmf_size = 512*1024; //存取模式 mmf_access_mode access_mode = (GENERIC_READ|GENERIC_WRITE); //共享模式 mmf_share_mode share_mode = FILE_SHARE_READ | FILE_SHARE_WRITE; //文件属性 mmf_flags flags = FILE_FLAG_SEQUENTIAL_SCAN;//|FILE_FLAG_WRITE_THROUGH|FILE_FLAG_NO_BUFFERING; DWORD error_code; //创建文件 HANDLE mmHandle = CreateFile(file_name, access_mode, share_mode, NULL, OPEN_ALWAYS, flags, NULL); if (mmHandle == INVALID_HANDLE_VALUE) { error_code = GetLastError(); cout<<"创建mmf失败:"< }else{ DWORD high_size; DWORD file_size = GetFileSize(mmHandle, &high_size); if (file_size == BAD_POS && (error_code = GetLastError()) != SUCCESS) { CloseHandle(mmHandle); cout<<"error："< } cout<<"create mmf sucessfully"< //assert(file_size == 0); DWORD size_high = 0; //创建文件映射，如果要创建内存页面文件的映射，第一个参数设置为INVALID_HANDLE_VALUE HANDLE mmfm = CreateFileMapping(mmHandle, NULL, PAGE_READWRITE, size_high, mmf_size, shared_name); error_code = GetLastError(); if(SUCCESS != error_code){ cout<<"createFileMapping error"< }else{ if(mmfm == NULL){ if(mmHandle != INVALID_HANDLE_VALUE){ CloseHandle(mmHandle); } }else{ //char write_chars[] = "hello chars"; //size_t position = 0; //DWORD written = 0; //const size_t write_chars_size = sizeof(write_chars); //WriteFile(mmHandle,write_chars,write_chars_size,&written,NULL); size_t view_size = 1024*256; DWORD view_access = FILE_MAP_ALL_ACCESS; //获得映射视图 char* mmfm_base_address = (char*)MapViewOfFile(mmfm,view_access,0,0,view_size); if(mmfm_base_address == NULL){ error_code = GetLastError(); if(error_code != SUCCESS){ cout<<"error code "< } }else{ char write_chars[] = "hello chars"; const size_t write_chars_size = sizeof(write_chars); //向内存映射视图中写数据 CopyMemory((PVOID)mmfm_base_address, write_chars, write_chars_size); //memcpy(mmfm_base_address,write_chars,write_chars_size); size_t position = 0; char read_chars[write_chars_size]; //读数据 memcpy(read_chars,mmfm_base_address,write_chars_size); cout<<"read chars "< //卸载映射 UnmapViewOfFile(mmfm_base_address); //关闭内存映射文件 CloseHandle(mmfm); //关闭文件 CloseHandle(mmHandle); } } } } system("pause"); exit(0); return EXIT_SUCCESS; }

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