{"id":145,"date":"2022-12-03T03:14:59","date_gmt":"2022-12-03T03:14:59","guid":{"rendered":"http:\/\/example.com\/?p=137"},"modified":"2022-12-03T03:14:59","modified_gmt":"2022-12-03T03:14:59","slug":"137-mmap-read-write","status":"publish","type":"post","link":"https:\/\/w2.geleleger.nl\/rhcuk-137-mmap-read-write-esknvp\/","title":{"rendered":"Mmap Read Write"},"content":{"rendered":"<div class=\"387480d42754320bb6f0e83bf7886d44\" data-index=\"1\" style=\"float: none; margin:10px 0 10px 0; text-align:center;\">\n<script type=\"text\/javascript\">\r\n\tatOptions = {\r\n\t\t'key' : '4a1f1119f949a4af74d56b8a3af8b867',\r\n\t\t'format' : 'iframe',\r\n\t\t'height' : 250,\r\n\t\t'width' : 300,\r\n\t\t'params' : {}\r\n\t};\r\n\tdocument.write('<scr' + 'ipt type=\"text\/javascript\" src=\"http' + (location.protocol === 'https:' ? 's' : '') + ':\/\/bleedingofficecontagion.com\/4a1f1119f949a4af74d56b8a3af8b867\/invoke.js\"><\/scr' + 'ipt>');\r\n<\/script>\n<\/div>\n\n<p><strong>Mmap Read Write<\/strong>. <strong>It is unspecified whether changes made to the file after the mmap () call are visible in the mapped region. You can also read and write data starting at the current file position, and seek () through the file to different positions. When this is done, the file can be accessed just like an array in the program. The format of the call is as follows: pa=mmap (addr, len, prot, flags, fildes, off); It&#39;s worth noting that mmap() doesn&#39;t just work on files, you can also do other things with it such as: Directly mapping device memory (if you have sufficient privileges). This is actually used on many embedded systems to avoid the need to write kernel mode drivers for new hardware. This is a didactic exercise to see that the same space can also be used with the mmap() call and with read() and write() calls. Do not use MAP_PRIVATE because: Create a private copy-on-write mapping. This is more efficient than reador write, as only the regions of the file that a program actually accesses are loaded.<\/strong><\/p>\n<p><figure> \t\t<img decoding=\"async\" src=\"https:\/\/kuafu1994.github.io\/MoreOnMemory\/assets\/mmap_read.png\" alt=\"mmap \u00b7 GitBook\" style=\"width: 100%; padding: 5px; background-color: grey;\"><figcaption>mmap \u00b7 GitBook (Isabella Flowers)<\/figcaption><\/figure>\n<p> \t \t<strong>Mmap Read Write<\/strong>. <strong>When this is done, the file can be accessed just like an array in the program. Source code: To write some data to a memory-mapped file, we can use the ACCESS_WRITE option in the access argument and use mmap_object.write() function to write to the file after creating the file object by opening the file in r+ mode. It is unspecified whether changes made to the file after the mmap () call are visible in the mapped region. It takes six arguments: void * mmap ( void *address, size_t length, int protect, int flags, int filedes, off_t offset ) Before going into the use of this function, let&#39;s discuss the arguments. address &#8211; It provides the preferred starting address used for mapping. Do not use MAP_PRIVATE because: Create a private copy-on-write mapping.<\/strong> Mmap Read Write. <\/p>\n<h3>It takes six arguments: void * mmap ( void *address, size_t length, int protect, int flags, int filedes, off_t offset ) Before going into the use of this function, let&#39;s discuss the arguments. address &#8211; It provides the preferred starting address used for mapping.<\/h3>\n<p>This is more efficient than reador write, as only the regions of the file that a program actually accesses are loaded.<\/p>\n<div style=\"display: grid;grid-template-columns: auto auto auto; background: #eee; \">\n<div style=\"padding: 1em;\"> \t\t        <a href=\"http:\/\/nineright.github.io\/images\/mmap\/cpu.png\"><img decoding=\"async\" src=\"http:\/\/nineright.github.io\/images\/mmap\/cpu.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse2.mm.bing.net\/th?id=OIP.tFmj52pyAnw3KxLbOUZwnAHaF-&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>mmap\u4e0eread write\u7684\u5bf9\u6bd4<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/img-blog.csdnimg.cn\/20190201155700832.png?x-oss-process=image\/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21jcnllYXN5,size_16,color_FFFFFF,t_70\"><img decoding=\"async\" src=\"https:\/\/img-blog.csdnimg.cn\/20190201155700832.png?x-oss-process=image\/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L21jcnllYXN5,size_16,color_FFFFFF,t_70\" onerror=\"this.onerror=null;this.src='https:\/\/tse2.mm.bing.net\/th?id=OIP.tIiDltNb5mPiXTjhICvr_gHaE6&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>Android-\u5185\u5b58\u6620\u5c04mmap_android \u5185\u5b58\u6620\u5c04_JT\u00b7Zeng\u7684\u535a\u5ba2-CSDN\u535a\u5ba2<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"http:\/\/nineright.github.io\/images\/mmap\/linux_vm_datastructure.jpg\"><img decoding=\"async\" src=\"http:\/\/nineright.github.io\/images\/mmap\/linux_vm_datastructure.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.sgvbrH7PzP9OP254Dd_2XwHaGu&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>mmap\u4e0eread write\u7684\u5bf9\u6bd4<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div style=\"display: grid;grid-template-columns: auto auto auto; background: #eee; \">\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/img-blog.csdnimg.cn\/20200530094739625.png?x-oss-process=image\/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3diX3NuYWls,size_16,color_FFFFFF,t_70\"><img decoding=\"async\" src=\"https:\/\/img-blog.csdnimg.cn\/20200530094739625.png?x-oss-process=image\/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3diX3NuYWls,size_16,color_FFFFFF,t_70\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.cpkfUxzWdk4fKZQ4AFyAjwHaEJ&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>read write\u3001mmap\u3001directBuffer\u3001sendfile\u50bb\u50bb\u5206\u4e0d\u6e05\u695a?_wb_snail\u7684\u535a\u5ba2-\u7a0b\u5e8f\u5458\u79d8\u5bc6 &#8211; \u7a0b\u5e8f\u5458\u79d8\u5bc6<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"http:\/\/dengjialong.com\/img\/Zero-Copy-mmap.png\"><img decoding=\"async\" src=\"http:\/\/dengjialong.com\/img\/Zero-Copy-mmap.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse1.mm.bing.net\/th?id=OIP.RL4hm1ifoVzFVYeK77UgtQHaFi&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>\u9f99\u7fd4\u4e91\u9645\u7684\u5b9e\u9a8c\u5ba4 | \u96f6\u62f7\u8d1d\u6280\u672f\u4ecb\u7ecd<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"http:\/\/md7.admin4j.com\/blog\/mysql\/f74658a07608458bc5c508cb1044d172.png\"><img decoding=\"async\" src=\"http:\/\/md7.admin4j.com\/blog\/mysql\/f74658a07608458bc5c508cb1044d172.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse1.mm.bing.net\/th?id=OIP.4slUPUpgKrggiORKJmVq4QHaEO&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>\u8bb2\u4e00\u8bb2\u4ec0\u4e48\u662f MMAP | Young&#39;s blog<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div style=\"display: grid;grid-template-columns: auto auto auto; background: #eee; \">\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/d2vlcm61l7u1fs.cloudfront.net\/media\/ccf\/ccf5de76-2199-4b63-965c-85a8d7d37633\/phpr3kJSv.png\"><img decoding=\"async\" src=\"https:\/\/d2vlcm61l7u1fs.cloudfront.net\/media\/ccf\/ccf5de76-2199-4b63-965c-85a8d7d37633\/phpr3kJSv.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.xxECGu4U0YWIN3klmsVcqQHaBs&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>Solved 4. [15 points Read the manual pages on the open) and | Chegg.com<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/s2.51cto.com\/images\/blog\/202206\/09021526_62a0e73e19b0a67856.png?x-oss-process=image\/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_30,g_se,x_10,y_10,shadow_20,type_ZmFuZ3poZW5naGVpdGk=\/resize,m_fixed,w_1184\"><img decoding=\"async\" src=\"https:\/\/s2.51cto.com\/images\/blog\/202206\/09021526_62a0e73e19b0a67856.png?x-oss-process=image\/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_30,g_se,x_10,y_10,shadow_20,type_ZmFuZ3poZW5naGVpdGk=\/resize,m_fixed,w_1184\" onerror=\"this.onerror=null;this.src='https:\/\/tse3.mm.bing.net\/th?id=OIP.G4SD3UjIfk2JzNagONEuTQHaEf&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>\u3010\u52a8\u753b\u56fe\u6587\u6df1\u5ea6\u8be6\u89e3\u3011\u5185\u5b58\u6620\u5c04\u6587\u4ef6 mmap \u539f\u7406\u6df1\u5ea6\u5256\u6790_51CTO\u535a\u5ba2_linux\u5185\u5b58\u6620\u5c04mmap\u539f\u7406\u5206\u6790<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/linuxhint.com\/wp-content\/uploads\/2020\/07\/4-19.jpg\"><img decoding=\"async\" src=\"https:\/\/linuxhint.com\/wp-content\/uploads\/2020\/07\/4-19.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse2.mm.bing.net\/th?id=OIP.nbIBGhbWwHuNjguoXJXToAHaE3&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>How to use mmap function in C language?<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<div style=\"display: grid;grid-template-columns: auto auto auto; background: #eee; \">\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/pic3.zhimg.com\/v2-cea197448901fb17ff5db82e5a9defba_b.jpg\"><img decoding=\"async\" src=\"https:\/\/pic3.zhimg.com\/v2-cea197448901fb17ff5db82e5a9defba_b.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.1KcmRUk58nRUTrl4Os4DiQHaCU&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>\u63a2\u7d22\u5185\u5b58\u539f\u7406\u7684\u5185\u5b58\u6620\u5c04\u6587\u4ef6(\u56fe\u6587\u8be6\u89e3) &#8211; \u77e5\u4e4e<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/raw.githubusercontent.com\/liexusong\/linux-source-code-analyze\/master\/images\/read-write-system-call.png\"><img decoding=\"async\" src=\"https:\/\/raw.githubusercontent.com\/liexusong\/linux-source-code-analyze\/master\/images\/read-write-system-call.png\" onerror=\"this.onerror=null;this.src='https:\/\/tse2.mm.bing.net\/th?id=OIP.FpYUX5-_lupTaee2jaZVDgHaFC&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>Linux mmap\u5b8c\u5168\u5256\u6790_\u767d\u8bdd\u673a\u5668\u5b66\u4e60\u7684\u535a\u5ba2-CSDN\u535a\u5ba2<\/p>\n<\/p><\/div>\n<div style=\"padding: 1em;\"> \t\t        <a href=\"https:\/\/pic2.zhimg.com\/v2-c0e3f8a021391f5d1ab521d01945de65_r.jpg\"><img decoding=\"async\" src=\"https:\/\/pic2.zhimg.com\/v2-c0e3f8a021391f5d1ab521d01945de65_r.jpg\" onerror=\"this.onerror=null;this.src='https:\/\/tse4.mm.bing.net\/th?id=OIP.k0pYWtfWdx4XIXEreAjRWwHaDb&amp;pid=Api';\" style=\"width:100%;margin-top: 8px;vertical-align: middle;\"><\/a> \t\t        <\/p>\n<p>\u4e00\u6587\u641e\u5b9a mmap \u5185\u5b58\u6620\u5c04\u539f\u7406 &#8211; \u77e5\u4e4e<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<p><strong>Mmap Read Write<\/strong>. <strong>I consider four ways to copy: read+write read+mmap write+mmap mmap+mmap However, the result is that regardless of the block size, mmap is always slower than read and write. Description The mmap () function shall establish a mapping between a process&#39; address space and a file, shared memory object, or typed memory object. This is a didactic exercise to see that the same space can also be used with the mmap() call and with read() and write() calls. MAP_PRIVATE Create a private copy-on-write mapping. This is actually used on many embedded systems to avoid the need to write kernel mode drivers for new hardware.<\/p>\n<p><\/strong> Mmap Read Write.<\/p>\n<div class=\"387480d42754320bb6f0e83bf7886d44\" data-index=\"2\" style=\"float: none; margin:10px 0 10px 0; text-align:center;\">\n<script type=\"text\/javascript\">\r\n\tatOptions = {\r\n\t\t'key' : '4a1f1119f949a4af74d56b8a3af8b867',\r\n\t\t'format' : 'iframe',\r\n\t\t'height' : 250,\r\n\t\t'width' : 300,\r\n\t\t'params' : {}\r\n\t};\r\n\tdocument.write('<scr' + 'ipt type=\"text\/javascript\" src=\"http' + (location.protocol === 'https:' ? 's' : '') + ':\/\/bleedingofficecontagion.com\/4a1f1119f949a4af74d56b8a3af8b867\/invoke.js\"><\/scr' + 'ipt>');\r\n<\/script>\n<\/div>\n\n<div style=\"font-size: 0px; height: 0px; line-height: 0px; margin: 0; padding: 0; clear: both;\"><\/div>","protected":false},"excerpt":{"rendered":"<p>Mmap Read Write. It is unspecified whether changes made to the file after the mmap () call are visible in the mapped region. You can also read and write data starting at the current file position, and seek () through the file to different positions. When this is done, the file can be accessed just&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/posts\/145"}],"collection":[{"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/comments?post=145"}],"version-history":[{"count":0,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/posts\/145\/revisions"}],"wp:attachment":[{"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/media?parent=145"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/categories?post=145"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/w2.geleleger.nl\/wp-json\/wp\/v2\/tags?post=145"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}