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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Virtual Table Instance Object</title><style type="text/css">body { margin: auto; font-family: "Verdana" "sans-serif"; padding: 8px 1%;}a { color: #45735f }a:visited { color: #734559 }.logo { position:absolute; margin:3px; }.tagline { float:right; text-align:right; font-style:italic; width:240px; margin:12px; margin-top:58px;}.toolbar { font-variant: small-caps; text-align: center; line-height: 1.6em; margin: 0; padding:1px 8px;}.toolbar a { color: white; text-decoration: none; padding: 6px 12px; }.toolbar a:visited { color: white; }.toolbar a:hover { color: #80a796; background: white; }.content { margin: 5%; }.content dt { font-weight:bold; }.content dd { margin-bottom: 25px; margin-left:20%; }.content ul { padding:0px; padding-left: 15px; margin:0px; }/* rounded corners */.se { background: url(../images/se.png) 100% 100% no-repeat #80a796}.sw { background: url(../images/sw.png) 0% 100% no-repeat }.ne { background: url(../images/ne.png) 100% 0% no-repeat }.nw { background: url(../images/nw.png) 0% 0% no-repeat }</style><meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head><body><div><!-- container div to satisfy validator --><a href="../index.html"><img class="logo" src="../images/SQLite.gif" alt="SQLite Logo" border="0"></a><div><!-- IE hack to prevent disappearing logo--></div><div class="tagline">Small. Fast. Reliable.<br>Choose any three.</div><table width=100% style="clear:both"><tr><td> <div class="se"><div class="sw"><div class="ne"><div class="nw"> <div class="toolbar"> <a href="../about.html">About</a> <a href="../sitemap.html">Sitemap</a> <a href="../docs.html">Documentation</a> <a href="../download.html">Download</a> <a href="../copyright.html">License</a> <a href="../news.html">News</a> <a href="http://www.sqlite.org/cvstrac/index">Developers</a> <a href="../support.html">Support</a> </div></div></div></div></div></td></tr></table> <a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Virtual Table Instance Object</h2><blockquote><pre>struct sqlite3_vtab { const sqlite3_module *pModule; /* The module for this virtual table */ int nRef; /* Used internally */ char *zErrMsg; /* Error message from sqlite3_mprintf() */ /* Virtual table implementations will typically add additional fields */};</pre></blockquote><p>Every module implementation uses a subclass of the following structureto describe a particular instance of the module. Each subclass willbe tailored to the specific needs of the module implementation. Thepurpose of this superclass is to define certain fields that are commonto all module implementations.</p><p>Virtual tables methods can set an error message by assigning astring obtained from sqlite3_mprintf() to zErrMsg. The method shouldtake care that any prior string is freed by a call to sqlite3_free()prior to assigning a new string to zErrMsg. After the error messageis delivered up to the client application, the string will be automaticallyfreed by sqlite3_free() and the zErrMsg field will be zeroed. Notethat sqlite3_mprintf() and sqlite3_free() are used on the zErrMsg fieldsince virtual tables are commonly implemented in loadable extensions whichdo not have access to sqlite3MPrintf() or sqlite3Free().</p><p>See also lists of <a href="objlist.html">Objects</a>, <a href="constlist.html">Constants</a>, and <a href="funclist.html">Functions</a>.</p><hr><small><i>This page last modified 2008/05/12 13:08:44 UTC</i></small></div></body></html>⌨️ 快捷键说明
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