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diff --git a/www/c3ref/get_auxdata.html b/www/c3ref/get_auxdata.html new file mode 100644 index 0000000..57bb1e9 --- /dev/null +++ b/www/c3ref/get_auxdata.html @@ -0,0 +1,194 @@ +<!DOCTYPE html> +<html><head> +<meta name="viewport" content="width=device-width, initial-scale=1.0"> +<meta http-equiv="content-type" content="text/html; charset=UTF-8"> +<link href="../sqlite.css" rel="stylesheet"> +<title>Function Auxiliary Data</title> +<!-- path=../ --> +</head> +<body> +<div class=nosearch> +<a href="../index.html"> +<img class="logo" src="../images/sqlite370_banner.gif" alt="SQLite" border="0"> +</a> +<div><!-- IE hack to prevent disappearing logo --></div> +<div class="tagline desktoponly"> +Small. Fast. Reliable.<br>Choose any three. +</div> +<div class="menu mainmenu"> +<ul> +<li><a href="../index.html">Home</a> +<li class='mobileonly'><a href="javascript:void(0)" onclick='toggle_div("submenu")'>Menu</a> +<li class='wideonly'><a href='../about.html'>About</a> +<li class='desktoponly'><a href="../docs.html">Documentation</a> +<li class='desktoponly'><a href="../download.html">Download</a> +<li class='wideonly'><a href='../copyright.html'>License</a> +<li class='desktoponly'><a href="../support.html">Support</a> +<li class='desktoponly'><a href="../prosupport.html">Purchase</a> +<li class='search' id='search_menubutton'> +<a href="javascript:void(0)" onclick='toggle_search()'>Search</a> +</ul> +</div> +<div class="menu submenu" id="submenu"> +<ul> +<li><a href='../about.html'>About</a> +<li><a href='../docs.html'>Documentation</a> +<li><a href='../download.html'>Download</a> +<li><a href='../support.html'>Support</a> +<li><a href='../prosupport.html'>Purchase</a> +</ul> +</div> +<div class="searchmenu" id="searchmenu"> +<form method="GET" action="../search"> +<select name="s" id="searchtype"> +<option value="d">Search Documentation</option> +<option value="c">Search Changelog</option> +</select> +<input type="text" name="q" id="searchbox" value=""> +<input type="submit" value="Go"> +</form> +</div> +</div> +<script> +function toggle_div(nm) { +var w = document.getElementById(nm); +if( w.style.display=="block" ){ +w.style.display = "none"; +}else{ +w.style.display = "block"; +} +} +function toggle_search() { +var w = document.getElementById("searchmenu"); +if( w.style.display=="block" ){ +w.style.display = "none"; +} else { +w.style.display = "block"; +setTimeout(function(){ +document.getElementById("searchbox").focus() +}, 30); +} +} +function div_off(nm){document.getElementById(nm).style.display="none";} +window.onbeforeunload = function(e){div_off("submenu");} +/* Disable the Search feature if we are not operating from CGI, since */ +/* Search is accomplished using CGI and will not work without it. */ +if( !location.origin || !location.origin.match || !location.origin.match(/http/) ){ +document.getElementById("search_menubutton").style.display = "none"; +} +/* Used by the Hide/Show button beside syntax diagrams, to toggle the */ +function hideorshow(btn,obj){ +var x = document.getElementById(obj); +var b = document.getElementById(btn); +if( x.style.display!='none' ){ +x.style.display = 'none'; +b.innerHTML='show'; +}else{ +x.style.display = ''; +b.innerHTML='hide'; +} +return false; +} +var antiRobot = 0; +function antiRobotGo(){ +if( antiRobot!=3 ) return; +antiRobot = 7; +var j = document.getElementById("mtimelink"); +if(j && j.hasAttribute("data-href")) j.href=j.getAttribute("data-href"); +} +function antiRobotDefense(){ +document.body.onmousedown=function(){ +antiRobot |= 2; +antiRobotGo(); +document.body.onmousedown=null; +} +document.body.onmousemove=function(){ +antiRobot |= 2; +antiRobotGo(); +document.body.onmousemove=null; +} +setTimeout(function(){ +antiRobot |= 1; +antiRobotGo(); +}, 100) +antiRobotGo(); +} +antiRobotDefense(); +</script> +<!-- keywords: sqlite3_get_auxdata sqlite3_set_auxdata --> +<div class=nosearch> +<a href="../c3ref/intro.html"><h2>SQLite C Interface</h2></a> +<h2>Function Auxiliary Data</h2> +</div> +<blockquote><pre> +void *sqlite3_get_auxdata(sqlite3_context*, int N); +void sqlite3_set_auxdata(sqlite3_context*, int N, void*, void (*)(void*)); +</pre></blockquote> +<p> +These functions may be used by (non-aggregate) SQL functions to +associate auxiliary data with argument values. If the same argument +value is passed to multiple invocations of the same SQL function during +query execution, under some circumstances the associated auxiliary data +might be preserved. An example of where this might be useful is in a +regular-expression matching function. The compiled version of the regular +expression can be stored as auxiliary data associated with the pattern string. +Then as long as the pattern string remains the same, +the compiled regular expression can be reused on multiple +invocations of the same function.</p> + +<p>The sqlite3_get_auxdata(C,N) interface returns a pointer to the auxiliary data +associated by the sqlite3_set_auxdata(C,N,P,X) function with the Nth argument +value to the application-defined function. N is zero for the left-most +function argument. If there is no auxiliary data +associated with the function argument, the sqlite3_get_auxdata(C,N) interface +returns a NULL pointer.</p> + +<p>The sqlite3_set_auxdata(C,N,P,X) interface saves P as auxiliary data for the +N-th argument of the application-defined function. Subsequent +calls to sqlite3_get_auxdata(C,N) return P from the most recent +sqlite3_set_auxdata(C,N,P,X) call if the auxiliary data is still valid or +NULL if the auxiliary data has been discarded. +After each call to sqlite3_set_auxdata(C,N,P,X) where X is not NULL, +SQLite will invoke the destructor function X with parameter P exactly +once, when the auxiliary data is discarded. +SQLite is free to discard the auxiliary data at any time, including: <ul> +<li> when the corresponding function parameter changes, or +<li> when <a href="../c3ref/reset.html">sqlite3_reset()</a> or <a href="../c3ref/finalize.html">sqlite3_finalize()</a> is called for the +SQL statement, or +<li> when sqlite3_set_auxdata() is invoked again on the same +parameter, or +<li> during the original sqlite3_set_auxdata() call when a memory +allocation error occurs. +<li> during the original sqlite3_set_auxdata() call if the function +is evaluated during query planning instead of during query execution, +as sometimes happens with <a href="../compile.html#enable_stat4">SQLITE_ENABLE_STAT4</a>. </ul></p> + +<p>Note the last two bullets in particular. The destructor X in +sqlite3_set_auxdata(C,N,P,X) might be called immediately, before the +sqlite3_set_auxdata() interface even returns. Hence sqlite3_set_auxdata() +should be called near the end of the function implementation and the +function implementation should not make any use of P after +sqlite3_set_auxdata() has been called. Furthermore, a call to +sqlite3_get_auxdata() that occurs immediately after a corresponding call +to sqlite3_set_auxdata() might still return NULL if an out-of-memory +condition occurred during the sqlite3_set_auxdata() call or if the +function is being evaluated during query planning rather than during +query execution.</p> + +<p>In practice, auxiliary data is preserved between function calls for +function parameters that are compile-time constants, including literal +values and <a href="../lang_expr.html#varparam">parameters</a> and expressions composed from the same.</p> + +<p>The value of the N parameter to these interfaces should be non-negative. +Future enhancements may make use of negative N values to define new +kinds of function caching behavior.</p> + +<p>These routines must be called from the same thread in which +the SQL function is running.</p> + +<p>See also: <a href="../c3ref/get_clientdata.html">sqlite3_get_clientdata()</a> and <a href="../c3ref/get_clientdata.html">sqlite3_set_clientdata()</a>. +</p><p>See also lists of + <a href="../c3ref/objlist.html">Objects</a>, + <a href="../c3ref/constlist.html">Constants</a>, and + <a href="../c3ref/funclist.html">Functions</a>.</p> + |