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External Data Representation
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<h2 id="history">History</h2> <p>XDR was developed in the mid 1980s at <a href="/facts/Sun_Microsystems/VJ9EzEFd">Sun Microsystems</a>, and first widely published in 1987.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> XDR became an <a href="/facts/IETF/tIcCsFhX">IETF</a> <a href="/facts/Internet_standard/LT6VEfhg">standard</a> in 1995. </p><p>The XDR data format is in use by many systems, including: </p> <ul><li><a href="/facts/Network_File_System_(protocol)/jWRRALVo">Network File System (protocol)</a></li> <li><a href="/facts/ZFS/cmh5BHlp">ZFS</a> File System</li> <li><a href="/facts/NDMP/QGooj0W9">NDMP</a> Network Data Management Protocol</li> <li><a href="/facts/Open_Network_Computing_Remote_Procedure_Call/oSR4C7hH">Open Network Computing Remote Procedure Call</a></li> <li><a href="/facts/EMC_NetWorker/AyD3QHoQ">Legato NetWorker</a> backup software (later sold by EMC)</li> <li><a href="/facts/NetCDF/DUwTEW7n">NetCDF</a> (a scientific data format)</li> <li>The <a href="/facts/R_programming_language/LSrkr8K8">R language and environment for statistical computing</a></li> <li>The <a href="http://www.w3.org/Protocols/HTTP-NG/http-ng-status.html">HTTP-NG</a> Binary Wire Protocol</li> <li>The <a href="/facts/SpiderMonkey_(Javascript_engine)/YosPe1Bv">SpiderMonkey</a> JavaScript engine, to serialize/deserialize compiled JavaScript code</li> <li>The <a href="/facts/Ganglia_(software)/BtmLHKUM">Ganglia</a> distributed monitoring system</li> <li>The <a href="/facts/SFlow/e2E64s6o">sFlow</a> network monitoring standard</li> <li>The <a href="/facts/Libvirt/9YwAkRsr">libvirt</a> virtualization library, <a href="/facts/Application_Programming_Interface/GMlN4vUr">API</a> and <a href="/facts/User_Interface/e9sPEWVD">UI</a></li> <li>The <a href="/facts/Firebird_(database_server)/hKVdDnBR">Firebird (database server)</a> for Remote Binary Wire Protocol</li> <li><a href="/facts/Stellar_(payment_network)/YITjaA2T">Stellar Payment Network</a></li></ul> <h2 id="xdr-data-types">XDR data types</h2> <ul><li><a href="/facts/Boolean_data_type/0GWYLDoC">boolean</a></li> <li>int – 32-bit <a href="/facts/Integer_(computer_science)/zWabo5M9">integer</a></li> <li>unsigned int – unsigned 32-bit <a href="/facts/Integer_(computer_science)/zWabo5M9">integer</a></li> <li>hyper – 64-bit <a href="/facts/Integer_(computer_science)/zWabo5M9">integer</a></li> <li>unsigned hyper – unsigned 64-bit <a href="/facts/Integer_(computer_science)/zWabo5M9">integer</a></li> <li><a href="/facts/IEEE_754/dD3e7zAl">IEEE</a> <a href="/facts/Floating_point/eIckahxe">float</a></li> <li>IEEE <a href="/facts/Double_precision/JYyXXYFM">double</a></li> <li><a href="/facts/Quadruple_precision/50oPmapW">quadruple</a> (new in RFC1832)</li> <li><a href="/facts/Enumerated_type/oQITgIYb">enumeration</a></li> <li><a href="/facts/Record_(computer_science)/1fvSgenB">structure</a></li> <li><a href="/facts/String_(computer_science)/4ChJu5WS">string</a></li> <li>fixed length <a href="/facts/Array_data_structure/BKGvF8AM">array</a></li> <li>variable length <a href="/facts/Array_data_structure/BKGvF8AM">array</a></li> <li><a href="/facts/Tagged_union/uMFenvCQ">union</a> – discriminated union</li> <li>fixed length <a href="/facts/Opaque_data_type/yMAgh1Kj">opaque</a> data</li> <li>variable length <a href="/facts/Opaque_data_type/yMAgh1Kj">opaque</a> data</li> <li><a href="/facts/Void_type/qbMrxVtl">void</a> – zero byte quantity</li> <li>optional – optional data is notated similarly to C pointers, but is represented as the data type "pointed to" with a Boolean "present or not" flag. Semantically this is <a href="/facts/Option_type/B0QX5wGB">option type</a>.</li></ul> <h2 id="see-also">See also</h2> <ul><li>Structured Data eXchange Format (<a href="/facts/SDXF/kMIeNHpn">SDXF</a>)</li> <li><a href="/facts/Remote_Procedure_Call/uMMb9CQw">Remote Procedure Call</a></li> <li><a href="/facts/Abstract_Syntax_Notation_One/ryUN7doc">Abstract Syntax Notation One</a></li> <li><a href="/facts/Data_Format_Description_Language/THnVXTNz">Data Format Description Language</a></li> <li><a href="/facts/Comparison_of_data_serialization_formats/YGkeqybD">Comparison of data serialization formats</a></li></ul> <h2 id="external-links">External links</h2> <p>The XDR standard exists in three different versions in the following RFCs: </p> <ul><li>RFC <a href="https://datatracker.ietf.org/doc/html/rfc4506">4506</a> 2006 This document makes no technical changes to RFC 1832 and is published for the purposes of noting IANA considerations, augmenting security considerations, and distinguishing normative from informative references.</li> <li>RFC <a href="https://datatracker.ietf.org/doc/html/rfc1832">1832</a> 1995 version. Added Quadruple precision floating point to RFC 1014.</li> <li>RFC <a href="https://datatracker.ietf.org/doc/html/rfc1014">1014</a> 1987 version.</li> <li><a href="http://www.cisco.com/en/US/docs/ios/sw_upgrades/interlink/r2_0/rpc_pr/rpxdesc.html">Cisco's XDR: Technical Notes</a></li> <li><a href="https://archive.today/20130415090003/http://lxr.mozilla.org/seamonkey/source/js/src/jsxdrapi.c">jsxdrapi.c</a>, the main source file of SpiderMonkey that uses XDR</li> <li><a href="http://sourceforge.net/p/firebird/code/59328/tree/firebird/trunk/src/remote/protocol.cpp">protocol.cpp</a> main xdr source file used in Firebird remote protocol</li> <li><a href="https://archive.today/20150213112723/https://sourceware.org/git/?p=glibc.git;a=tree;f=sunrpc;hb=HEAD">The GNU Libc implementation of rpcgen, the XDR parser.</a></li> <li><a href="https://web.archive.org/web/20080908103558/http://labs.mudynamics.com/2008/03/24/ruby-xdr-parser/">Mu Dynamics Research Labs racc grammar for XDR</a></li> <li><a href="http://ivmaiasn.sourceforge.net/">IvmaiAsn ASN1/ECN/XDR Tools</a> (a collection of tools containing an XDR/RPC-to-ASN.1 converter)</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Sun Microsystems (1987). "XDR: External Data Representation Standard". RFC 1014. Network Working Group. doi:10.17487/RFC1014. Retrieved July 11, 2011. <a href="http://tools.ietf.org/html/rfc1014" target="_blank">http://tools.ietf.org/html/rfc1014</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> </ol>