diff options
Diffstat (limited to 'www/c3ref/mutex_methods.html')
-rw-r--r-- | www/c3ref/mutex_methods.html | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/www/c3ref/mutex_methods.html b/www/c3ref/mutex_methods.html new file mode 100644 index 0000000..2d47826 --- /dev/null +++ b/www/c3ref/mutex_methods.html @@ -0,0 +1,203 @@ +<!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>Mutex Methods Object</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_mutex_methods --> +<div class=nosearch> +<a href="../c3ref/intro.html"><h2>SQLite C Interface</h2></a> +<h2>Mutex Methods Object</h2> +</div> +<blockquote><pre> +typedef struct sqlite3_mutex_methods sqlite3_mutex_methods; +struct sqlite3_mutex_methods { + int (*xMutexInit)(void); + int (*xMutexEnd)(void); + sqlite3_mutex *(*xMutexAlloc)(int); + void (*xMutexFree)(sqlite3_mutex *); + void (*xMutexEnter)(sqlite3_mutex *); + int (*xMutexTry)(sqlite3_mutex *); + void (*xMutexLeave)(sqlite3_mutex *); + int (*xMutexHeld)(sqlite3_mutex *); + int (*xMutexNotheld)(sqlite3_mutex *); +}; +</pre></blockquote> +<p> +An instance of this structure defines the low-level routines +used to allocate and use mutexes.</p> + +<p>Usually, the default mutex implementations provided by SQLite are +sufficient, however the application has the option of substituting a custom +implementation for specialized deployments or systems for which SQLite +does not provide a suitable implementation. In this case, the application +creates and populates an instance of this structure to pass +to sqlite3_config() along with the <a href="../c3ref/c_config_covering_index_scan.html#sqliteconfigmutex">SQLITE_CONFIG_MUTEX</a> option. +Additionally, an instance of this structure can be used as an +output variable when querying the system for the current mutex +implementation, using the <a href="../c3ref/c_config_covering_index_scan.html#sqliteconfiggetmutex">SQLITE_CONFIG_GETMUTEX</a> option.</p> + +<p>The xMutexInit method defined by this structure is invoked as +part of system initialization by the sqlite3_initialize() function. +The xMutexInit routine is called by SQLite exactly once for each +effective call to <a href="../c3ref/initialize.html">sqlite3_initialize()</a>.</p> + +<p>The xMutexEnd method defined by this structure is invoked as +part of system shutdown by the sqlite3_shutdown() function. The +implementation of this method is expected to release all outstanding +resources obtained by the mutex methods implementation, especially +those obtained by the xMutexInit method. The xMutexEnd() +interface is invoked exactly once for each call to <a href="../c3ref/initialize.html">sqlite3_shutdown()</a>.</p> + +<p>The remaining seven methods defined by this structure (xMutexAlloc, +xMutexFree, xMutexEnter, xMutexTry, xMutexLeave, xMutexHeld and +xMutexNotheld) implement the following interfaces (respectively):</p> + +<p><ul> +<li> <a href="../c3ref/mutex_alloc.html">sqlite3_mutex_alloc()</a> </li> +<li> <a href="../c3ref/mutex_alloc.html">sqlite3_mutex_free()</a> </li> +<li> <a href="../c3ref/mutex_alloc.html">sqlite3_mutex_enter()</a> </li> +<li> <a href="../c3ref/mutex_alloc.html">sqlite3_mutex_try()</a> </li> +<li> <a href="../c3ref/mutex_alloc.html">sqlite3_mutex_leave()</a> </li> +<li> <a href="../c3ref/mutex_held.html">sqlite3_mutex_held()</a> </li> +<li> <a href="../c3ref/mutex_held.html">sqlite3_mutex_notheld()</a> </li> +</ul></p> + +<p>The only difference is that the public sqlite3_XXX functions enumerated +above silently ignore any invocations that pass a NULL pointer instead +of a valid mutex handle. The implementations of the methods defined +by this structure are not required to handle this case. The results +of passing a NULL pointer instead of a valid mutex handle are undefined +(i.e. it is acceptable to provide an implementation that segfaults if +it is passed a NULL pointer).</p> + +<p>The xMutexInit() method must be threadsafe. It must be harmless to +invoke xMutexInit() multiple times within the same process and without +intervening calls to xMutexEnd(). Second and subsequent calls to +xMutexInit() must be no-ops.</p> + +<p>xMutexInit() must not use SQLite memory allocation (<a href="../c3ref/free.html">sqlite3_malloc()</a> +and its associates). Similarly, xMutexAlloc() must not use SQLite memory +allocation for a static mutex. However xMutexAlloc() may use SQLite +memory allocation for a fast or recursive mutex.</p> + +<p>SQLite will invoke the xMutexEnd() method when <a href="../c3ref/initialize.html">sqlite3_shutdown()</a> is +called, but only if the prior call to xMutexInit returned SQLITE_OK. +If xMutexInit fails in any way, it is expected to clean up after itself +prior to returning. +</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> + |