{"id":23944,"date":"2024-03-16T02:17:55","date_gmt":"2024-03-16T02:17:55","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/implementation-of-quick-file-reading-using-memory-mapping-in-c\/"},"modified":"2024-03-22T02:29:46","modified_gmt":"2024-03-22T02:29:46","slug":"implementation-of-quick-file-reading-using-memory-mapping-in-c","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/implementation-of-quick-file-reading-using-memory-mapping-in-c\/","title":{"rendered":"Implementation of quick file reading using memory mapping in C++."},"content":{"rendered":"<p>In C++, the CreateFileMapping function can be used to create a file mapping object to map a file into the virtual address space of a process. Subsequently, the MapViewOfFile function can be used to map the file into memory, enabling fast file reading operations.<\/p>\n<p>Here is an example code demonstrating how to quickly read a file using memory mapping.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;iostream&gt;<\/span><\/span>\r\n<span class=\"hljs-meta\">#<span class=\"hljs-keyword\">include<\/span> <span class=\"hljs-string\">&lt;Windows.h&gt;<\/span><\/span>\r\n\r\n<span class=\"hljs-function\"><span class=\"hljs-type\">int<\/span> <span class=\"hljs-title\">main<\/span><span class=\"hljs-params\">()<\/span> <\/span>{\r\n    HANDLE hFile = <span class=\"hljs-built_in\">CreateFile<\/span>(<span class=\"hljs-string\">L\"example.txt\"<\/span>, GENERIC_READ, FILE_SHARE_READ, <span class=\"hljs-literal\">NULL<\/span>, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, <span class=\"hljs-literal\">NULL<\/span>);\r\n    <span class=\"hljs-keyword\">if<\/span> (hFile == INVALID_HANDLE_VALUE) {\r\n        std::cout &lt;&lt; <span class=\"hljs-string\">\"Failed to open file.\"<\/span> &lt;&lt; std::endl;\r\n        <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">1<\/span>;\r\n    }\r\n\r\n    HANDLE hMapFile = <span class=\"hljs-built_in\">CreateFileMapping<\/span>(hFile, <span class=\"hljs-literal\">NULL<\/span>, PAGE_READONLY, <span class=\"hljs-number\">0<\/span>, <span class=\"hljs-number\">0<\/span>, <span class=\"hljs-literal\">NULL<\/span>);\r\n    <span class=\"hljs-keyword\">if<\/span> (hMapFile == <span class=\"hljs-literal\">NULL<\/span>) {\r\n        std::cout &lt;&lt; <span class=\"hljs-string\">\"Failed to create file mapping.\"<\/span> &lt;&lt; std::endl;\r\n        <span class=\"hljs-built_in\">CloseHandle<\/span>(hFile);\r\n        <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">1<\/span>;\r\n    }\r\n\r\n    LPVOID pData = <span class=\"hljs-built_in\">MapViewOfFile<\/span>(hMapFile, FILE_MAP_READ, <span class=\"hljs-number\">0<\/span>, <span class=\"hljs-number\">0<\/span>, <span class=\"hljs-number\">0<\/span>);\r\n    <span class=\"hljs-keyword\">if<\/span> (pData == <span class=\"hljs-literal\">NULL<\/span>) {\r\n        std::cout &lt;&lt; <span class=\"hljs-string\">\"Failed to map view of file.\"<\/span> &lt;&lt; std::endl;\r\n        <span class=\"hljs-built_in\">CloseHandle<\/span>(hMapFile);\r\n        <span class=\"hljs-built_in\">CloseHandle<\/span>(hFile);\r\n        <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">1<\/span>;\r\n    }\r\n\r\n    <span class=\"hljs-comment\">\/\/ \u8bfb\u53d6\u6587\u4ef6\u5185\u5bb9<\/span>\r\n    <span class=\"hljs-type\">char<\/span>* pFileData = <span class=\"hljs-built_in\">static_cast<\/span>&lt;<span class=\"hljs-type\">char<\/span>*&gt;(pData);\r\n    std::cout &lt;&lt; <span class=\"hljs-string\">\"File content: \"<\/span> &lt;&lt; pFileData &lt;&lt; std::endl;\r\n\r\n    <span class=\"hljs-built_in\">UnmapViewOfFile<\/span>(pData);\r\n    <span class=\"hljs-built_in\">CloseHandle<\/span>(hMapFile);\r\n    <span class=\"hljs-built_in\">CloseHandle<\/span>(hFile);\r\n\r\n    <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">0<\/span>;\r\n}\r\n<\/code><\/pre>\n<p>In the example above, the file example.txt is first opened using the CreateFile function. Then, a file mapping object hMapFile is created using the CreateFileMapping function. Next, the file is mapped into memory with the MapViewOfFile function, returning a pointer to the file content pData. Finally, by casting pData to type char*, we can access and manipulate the file content.<\/p>\n<p>It is important to note that after using file mapping, you need to call the UnmapViewOfFile function and CloseHandle function to release resources.<\/p>\n<p>The method of quickly reading files using the CreateFileMapping function in C++ has been described. When dealing with larger files, memory mapping can offer more efficient reading performance.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In C++, the CreateFileMapping function can be used to create a file mapping object to map a file into the virtual address space of a process. Subsequently, the MapViewOfFile function can be used to map the file into memory, enabling fast file reading operations. Here is an example code demonstrating how to quickly read a [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[],"class_list":["post-23944","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Implementation of quick file reading using memory mapping in C++. - Blog - Silicon Cloud<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.silicloud.com\/blog\/implementation-of-quick-file-reading-using-memory-mapping-in-c\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Implementation of quick file reading using memory mapping in C++.\" \/>\n<meta property=\"og:description\" content=\"In C++, the CreateFileMapping function can be used to create a file mapping object to map a file into the virtual address space of a process. 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