{"id":26831,"date":"2024-03-16T07:24:45","date_gmt":"2024-03-16T07:24:45","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/implement-fast-file-reading-using-memory-mapping-in-c-createfilemapping\/"},"modified":"2024-03-22T09:32:46","modified_gmt":"2024-03-22T09:32:46","slug":"implement-fast-file-reading-using-memory-mapping-in-c-createfilemapping","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/implement-fast-file-reading-using-memory-mapping-in-c-createfilemapping\/","title":{"rendered":"Implement fast file reading using memory mapping in C++ CreateFileMapping."},"content":{"rendered":"<p>In C++, one can create a memory mapping of a file using the CreateFileMapping function, and then map the file to memory using MapViewOfFile function to easily read the file by accessing the memory.<\/p>\n<p>Below is a sample code demonstrating how to use the CreateFileMapping and MapViewOfFile functions to achieve fast file reading:<\/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    <span class=\"hljs-comment\">\/\/ \u6253\u5f00\u6587\u4ef6<\/span>\r\n    HANDLE fileHandle = <span class=\"hljs-built_in\">CreateFile<\/span>(<span class=\"hljs-string\">\"test.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> (fileHandle == 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    <span class=\"hljs-comment\">\/\/ \u83b7\u53d6\u6587\u4ef6\u5927\u5c0f<\/span>\r\n    DWORD fileSize = <span class=\"hljs-built_in\">GetFileSize<\/span>(fileHandle, <span class=\"hljs-literal\">NULL<\/span>);\r\n\r\n    <span class=\"hljs-comment\">\/\/ \u521b\u5efa\u6587\u4ef6\u6620\u5c04<\/span>\r\n    HANDLE mappingHandle = <span class=\"hljs-built_in\">CreateFileMapping<\/span>(fileHandle, <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> (mappingHandle == <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>(fileHandle);\r\n        <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">1<\/span>;\r\n    }\r\n\r\n    <span class=\"hljs-comment\">\/\/ \u6620\u5c04\u6587\u4ef6\u5230\u5185\u5b58<\/span>\r\n    LPVOID fileMapping = <span class=\"hljs-built_in\">MapViewOfFile<\/span>(mappingHandle, FILE_MAP_READ, <span class=\"hljs-number\">0<\/span>, <span class=\"hljs-number\">0<\/span>, fileSize);\r\n    <span class=\"hljs-keyword\">if<\/span> (fileMapping == <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>(mappingHandle);\r\n        <span class=\"hljs-built_in\">CloseHandle<\/span>(fileHandle);\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>* fileData = <span class=\"hljs-built_in\">static_cast<\/span>&lt;<span class=\"hljs-type\">char<\/span>*&gt;(fileMapping);\r\n    <span class=\"hljs-keyword\">for<\/span> (DWORD i = <span class=\"hljs-number\">0<\/span>; i &lt; fileSize; i++) {\r\n        std::cout &lt;&lt; fileData[i];\r\n    }\r\n\r\n    <span class=\"hljs-comment\">\/\/ \u5173\u95ed\u6620\u5c04\u548c\u6587\u4ef6\u53e5\u67c4<\/span>\r\n    <span class=\"hljs-built_in\">UnmapViewOfFile<\/span>(fileMapping);\r\n    <span class=\"hljs-built_in\">CloseHandle<\/span>(mappingHandle);\r\n    <span class=\"hljs-built_in\">CloseHandle<\/span>(fileHandle);\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 this example, the file is first opened using the CreateFile function to obtain its size. Next, a file mapping object is created with the CreateFileMapping function and the file is mapped into memory using MapViewOfFile. Finally, the file contents are quickly read by accessing the memory.<\/p>\n<p>Please remember to release resources by calling functions like UnmapViewOfFile and CloseHandle after use.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In C++, one can create a memory mapping of a file using the CreateFileMapping function, and then map the file to memory using MapViewOfFile function to easily read the file by accessing the memory. Below is a sample code demonstrating how to use the CreateFileMapping and MapViewOfFile functions to achieve fast file reading: #include &lt;iostream&gt; [&hellip;]<\/p>\n","protected":false},"author":7,"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-26831","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>Implement fast file reading using memory mapping in C++ CreateFileMapping. - 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\/implement-fast-file-reading-using-memory-mapping-in-c-createfilemapping\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Implement fast file reading using memory mapping in C++ CreateFileMapping.\" \/>\n<meta property=\"og:description\" content=\"In C++, one can create a memory mapping of a file using the CreateFileMapping function, and then map the file to memory using MapViewOfFile function to easily read the file by accessing the memory. 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