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diff --git a/www/c3ref/create_collation.html b/www/c3ref/create_collation.html new file mode 100644 index 0000000..71e4b87 --- /dev/null +++ b/www/c3ref/create_collation.html @@ -0,0 +1,228 @@ +<!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>Define New Collating Sequences</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. 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+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_create_collation sqlite3_create_collation16 sqlite3_create_collation_v2 --> +<div class=nosearch> +<a href="intro.html"><h2>SQLite C Interface</h2></a> +<h2>Define New Collating Sequences</h2> +</div> +<blockquote><pre> +int sqlite3_create_collation( + sqlite3*, + const char *zName, + int eTextRep, + void *pArg, + int(*xCompare)(void*,int,const void*,int,const void*) +); +int sqlite3_create_collation_v2( + sqlite3*, + const char *zName, + int eTextRep, + void *pArg, + int(*xCompare)(void*,int,const void*,int,const void*), + void(*xDestroy)(void*) +); +int sqlite3_create_collation16( + sqlite3*, + const void *zName, + int eTextRep, + void *pArg, + int(*xCompare)(void*,int,const void*,int,const void*) +); +</pre></blockquote> +<p> +These functions add, remove, or modify a <a href="../datatype3.html#collation">collation</a> associated +with the <a href="../c3ref/sqlite3.html">database connection</a> specified as the first argument.</p> + +<p>The name of the collation is a UTF-8 string +for sqlite3_create_collation() and sqlite3_create_collation_v2() +and a UTF-16 string in native byte order for sqlite3_create_collation16(). +Collation names that compare equal according to <a href="../c3ref/stricmp.html">sqlite3_strnicmp()</a> are +considered to be the same name.</p> + +<p>The third argument (eTextRep) must be one of the constants: +<ul> +<li> <a href="../c3ref/c_any.html">SQLITE_UTF8</a>, +<li> <a href="../c3ref/c_any.html">SQLITE_UTF16LE</a>, +<li> <a href="../c3ref/c_any.html">SQLITE_UTF16BE</a>, +<li> <a href="../c3ref/c_any.html">SQLITE_UTF16</a>, or +<li> <a href="../c3ref/c_any.html">SQLITE_UTF16_ALIGNED</a>. +</ul> +The eTextRep argument determines the encoding of strings passed +to the collating function callback, xCompare. +The <a href="../c3ref/c_any.html">SQLITE_UTF16</a> and <a href="../c3ref/c_any.html">SQLITE_UTF16_ALIGNED</a> values for eTextRep +force strings to be UTF16 with native byte order. +The <a href="../c3ref/c_any.html">SQLITE_UTF16_ALIGNED</a> value for eTextRep forces strings to begin +on an even byte address.</p> + +<p>The fourth argument, pArg, is an application data pointer that is passed +through as the first argument to the collating function callback.</p> + +<p>The fifth argument, xCompare, is a pointer to the collating function. +Multiple collating functions can be registered using the same name but +with different eTextRep parameters and SQLite will use whichever +function requires the least amount of data transformation. +If the xCompare argument is NULL then the collating function is +deleted. When all collating functions having the same name are deleted, +that collation is no longer usable.</p> + +<p>The collating function callback is invoked with a copy of the pArg +application data pointer and with two strings in the encoding specified +by the eTextRep argument. The two integer parameters to the collating +function callback are the length of the two strings, in bytes. The collating +function must return an integer that is negative, zero, or positive +if the first string is less than, equal to, or greater than the second, +respectively. A collating function must always return the same answer +given the same inputs. If two or more collating functions are registered +to the same collation name (using different eTextRep values) then all +must give an equivalent answer when invoked with equivalent strings. +The collating function must obey the following properties for all +strings A, B, and C:</p> + +<p><ol> +<li> If A==B then B==A. +<li> If A==B and B==C then A==C. +<li> If A<B THEN B>A. +<li> If A<B and B<C then A<C. +</ol></p> + +<p>If a collating function fails any of the above constraints and that +collating function is registered and used, then the behavior of SQLite +is undefined.</p> + +<p>The sqlite3_create_collation_v2() works like sqlite3_create_collation() +with the addition that the xDestroy callback is invoked on pArg when +the collating function is deleted. +Collating functions are deleted when they are overridden by later +calls to the collation creation functions or when the +<a href="../c3ref/sqlite3.html">database connection</a> is closed using <a href="../c3ref/close.html">sqlite3_close()</a>.</p> + +<p>The xDestroy callback is <u>not</u> called if the +sqlite3_create_collation_v2() function fails. Applications that invoke +sqlite3_create_collation_v2() with a non-NULL xDestroy argument should +check the return code and dispose of the application data pointer +themselves rather than expecting SQLite to deal with it for them. +This is different from every other SQLite interface. The inconsistency +is unfortunate but cannot be changed without breaking backwards +compatibility.</p> + +<p>See also: <a href="../c3ref/collation_needed.html">sqlite3_collation_needed()</a> and <a href="../c3ref/collation_needed.html">sqlite3_collation_needed16()</a>. +</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> + |