VC++采用内存映射方式高效率读写大数据

// t_CreateFileMapping.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。 // #include "pch.h" #include <iostream> #include <assert.h> #include <Windows.h> #include <WinBase.h> #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..." << endl; 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(L"d:\\testMmf.mmf", access_mode, share_mode, NULL, OPEN_ALWAYS, flags, NULL); if (mmHandle == INVALID_HANDLE_VALUE) { error_code = GetLastError(); cout << "创建mmf失败:" << error_code << endl; } else { DWORD high_size; DWORD file_size = GetFileSize(mmHandle, &high_size); if (file_size == BAD_POS && (error_code = GetLastError()) != SUCCESS) { CloseHandle(mmHandle); cout << "error：" << error_code << endl; } cout << "create mmf sucessfully" << endl; //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, L"testMmf"); error_code = GetLastError(); if (SUCCESS != error_code) { cout << "createFileMapping error" << error_code << endl; } 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 " << error_code << endl; } } 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 " << read_chars << endl; //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; }