<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<!-- /tmp/qt-3.0-reggie-28534/qt-x11-free-3.0.2/doc/qasciicache.doc:41 -->
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>QAsciiCache Class</title>
<style type="text/css"><!--
h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm; }
a:link { color: #004faf; text-decoration: none }
a:visited { color: #672967; text-decoration: none }
body { background: #ffffff; color: black; }
--></style>
</head>
<body>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr bgcolor="#E5E5E5">
<td valign=center>
<a href="index.html">
<font color="#004faf">Home</font></a>
| <a href="classes.html">
<font color="#004faf">All Classes</font></a>
| <a href="mainclasses.html">
<font color="#004faf">Main Classes</font></a>
| <a href="annotated.html">
<font color="#004faf">Annotated</font></a>
| <a href="groups.html">
<font color="#004faf">Grouped Classes</font></a>
| <a href="functions.html">
<font color="#004faf">Functions</font></a>
</td>
<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QAsciiCache Class Reference</h1>
<p>The QAsciiCache class is a template class that provides a cache based on char* keys.
<a href="#details">More...</a>
<p><tt>#include <<a href="qasciicache-h.html">qasciicache.h</a>></tt>
<p><a href="qasciicache-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li><div class=fn><a href="#QAsciiCache-2"><b>QAsciiCache</b></a> ( int maxCost = 100, int size = 17, bool caseSensitive = TRUE, bool copyKeys = TRUE )</div></li>
<li><div class=fn><a href="#~QAsciiCache"><b>~QAsciiCache</b></a> ()</div></li>
<li><div class=fn>int <a href="#maxCost"><b>maxCost</b></a> () const</div></li>
<li><div class=fn>int <a href="#totalCost"><b>totalCost</b></a> () const</div></li>
<li><div class=fn>void <a href="#setMaxCost"><b>setMaxCost</b></a> ( int m )</div></li>
<li><div class=fn>virtual uint <a href="#count"><b>count</b></a> () const</div></li>
<li><div class=fn>uint <a href="#size"><b>size</b></a> () const</div></li>
<li><div class=fn>bool <a href="#isEmpty"><b>isEmpty</b></a> () const</div></li>
<li><div class=fn>virtual void <a href="#clear"><b>clear</b></a> ()</div></li>
<li><div class=fn>bool <a href="#insert"><b>insert</b></a> ( const char * k, const type * d, int c = 1, int p = 0 )</div></li>
<li><div class=fn>bool <a href="#remove"><b>remove</b></a> ( const char * k )</div></li>
<li><div class=fn>type * <a href="#take"><b>take</b></a> ( const char * k )</div></li>
<li><div class=fn>type * <a href="#find"><b>find</b></a> ( const char * k, bool ref = TRUE ) const</div></li>
<li><div class=fn>type * <a href="#operator[]"><b>operator[]</b></a> ( const char * k ) const</div></li>
<li><div class=fn>void <a href="#statistics"><b>statistics</b></a> () const</div></li>
</ul>
<hr><a name="details"></a><h2>Detailed Description</h2>
<p> The QAsciiCache class is a template class that provides a cache based on char* keys.
<p>
<p> QAsciiCache is implemented as a template class. Define a template
instance QAsciiCache<X> to create a cache that operates on pointers to
X, or X*.
<p> A cache is a least recently used (LRU) list of cache items. The
cache items are accessed via <tt>char*</tt> keys. QAsciiCache cannot handle
Unicode keys; use the <a href="qcache.html">QCache</a> template instead, which uses <a href="qstring.html">QString</a>
keys. A QCache has the same performace as a QAsciiCache.
<p> Each cache item has a cost. The sum of item costs, <a href="#totalCost">totalCost</a>(), will not
exceed the maximum cache cost, <a href="#maxCost">maxCost</a>(). If inserting a new item
would cause the total cost to exceed the maximum cost, the least
recently used items in the cache are removed.
<p> Apart from <a href="#insert">insert</a>(), by far the most important function is <a href="#find">find</a>()
(which also exists as operator[]). This function looks up an item,
returns it, and by default marks it as being the most recently used
item.
<p> There are also methods to <a href="#remove">remove</a>() or <a href="#take">take</a>() an object from the
cache. Calling setAutoDelete(TRUE) for a cache tells it to delete
items that are removed. The default is to not delete items when
then are removed (i.e., remove() and take() are equivalent).
<p> When inserting an item into the cache, only the pointer is copied, not
the item itself. This is called a <a href="shclass.html#shallow-copy">shallow copy</a>. It is possible to make the
cache copy all of the item's data (known as a <a href="shclass.html#deep-copy">deep copy</a>) when an
item is inserted. insert() calls the virtual function
<a href="qptrcollection.html#newItem">QPtrCollection::newItem</a>() for the item to be inserted.
Inherit a cache and reimplement it if you want deep copies.
<p> When removing a cache item the virtual function
<a href="qptrcollection.html#deleteItem">QPtrCollection::deleteItem</a>() is called. Its default implementation
in QAsciiCache is to delete the item if auto-deletion is enabled.
<p> There is a <a href="qasciicacheiterator.html">QAsciiCacheIterator</a> which may be used to traverse the
items in the cache in arbitrary order.
<p> <p>See also <a href="qasciicacheiterator.html">QAsciiCacheIterator</a>, <a href="qcache.html">QCache</a>, <a href="qintcache.html">QIntCache</a>, <a href="collection.html">Collection Classes</a> and <a href="tools.html">Non-GUI Classes</a>.
<hr><h2>Member Function Documentation</h2>
<h3 class=fn><a name="QAsciiCache-2"></a>QAsciiCache::QAsciiCache ( int maxCost = 100, int size = 17, bool caseSensitive = TRUE, bool copyKeys = TRUE )
</h3>
<p> Constructs a cache whose contents will never have a total cost
greater than <em>maxCost</em> and which is expected to contain less than
<em>size</em> items.
<p> <em>size</em> is actually the size of an internal hash array; it's usually
best to make it prime and at least 50% bigger than the largest
expected number of items in the cache.
<p> Each inserted item has an associated cost. When inserting a new
item, if the total cost of all items in the cache will exceed
<em>maxCost</em>, the cache will start throwing out the older (least
recently used) items until there is enough room for the new item to be
inserted.
<p> If <em>caseSensitive</em> is TRUE (the default), the cache keys are case
sensitive; if it is FALSE, they are
case-insensitive. Case-insensitive comparison includes only the 26
letters in US-ASCII. If <em>copyKeys</em> is TRUE (the default),
QAsciiCache makes a copy of the cache keys, otherwise it copies just
the const char * pointer - slightly faster if you can guarantee that
the keys will never change, but very risky.
<h3 class=fn><a name="~QAsciiCache"></a>QAsciiCache::~QAsciiCache ()
</h3>
<p> Removes all items from the cache and destroys it.
All iterators that access this cache will be reset.
<h3 class=fn>void <a name="clear"></a>QAsciiCache::clear ()<tt> [virtual]</tt>
</h3>
<p> Removes all items from the cache, and deletes them if auto-deletion
has been enabled.
<p> All cache iterators that operate this on cache are reset.
<p> <p>See also <a href="#remove">remove</a>() and <a href="#take">take</a>().
<h3 class=fn>uint <a name="count"></a>QAsciiCache::count () const<tt> [virtual]</tt>
</h3>
<p> Returns the number of items in the cache.
<p> <p>See also <a href="#totalCost">totalCost</a>().
<h3 class=fn>type * <a name="find"></a>QAsciiCache::find ( const char * k, bool ref = TRUE ) const
</h3>
<p> Returns the item associated with <em>k</em>, or null if the key does not
exist in the cache. If <em>ref</em> is TRUE (the default), the item is
moved to the front of the least recently used list.
<p> If there are two or more items with equal keys, the one that
was inserted last is returned.
<h3 class=fn>bool <a name="insert"></a>QAsciiCache::insert ( const char * k, const type * d, int c = 1, int p = 0 )
</h3>
<p> Inserts the item <em>d</em> into the cache with key <em>k</em> and cost <em>c</em>. Returns TRUE if it is successful and FALSE if it fails.
<p> The cache's size is limited, and if the total cost is too high,
QAsciiCache will remove old, least recently used items until there is
room for this new item.
<p> The parameter <em>p</em> is internal and should be left at the default
value (0).
<p> <b>Warning:</b> If this function returns FALSE, you must delete <em>d</em>
yourself. Additionally, be very careful about using <em>d</em> after
calling this function, because any other insertions into the cache, from
anywhere in the application or within Qt itself, could cause the
object to be discarded from the cache and the pointer to become
invalid.
<h3 class=fn>bool <a name="isEmpty"></a>QAsciiCache::isEmpty () const
</h3>
<p> Returns TRUE if the cache is empty, or FALSE if there is at least one
object in it.
<h3 class=fn>int <a name="maxCost"></a>QAsciiCache::maxCost () const
</h3>
<p> Returns the maximum allowed total cost of the cache.
<p>See also <a href="#setMaxCost">setMaxCost</a>() and <a href="#totalCost">totalCost</a>().
<h3 class=fn>type * <a name="operator[]"></a>QAsciiCache::operator[] ( const char * k ) const
</h3>
<p> Returns the item associated with <em>k</em>, or null if <em>k</em> does not
exist in the cache, and moves the item to the front of the least
recently used list.
<p> If there are two or more items with equal keys, the one that
was inserted last is returned.
<p> This is the same as <a href="#find">find</a>( k, TRUE ).
<p> <p>See also <a href="#find">find</a>().
<h3 class=fn>bool <a name="remove"></a>QAsciiCache::remove ( const char * k )
</h3>
<p> Removes the item associated with <em>k</em> and returns TRUE if the item
was present in the cache, or FALSE if it was not.
<p> The item is deleted if auto-deletion has been enabled, i.e., you have
called setAutoDelete(TRUE).
<p> If there are two or more items with equal keys, the one that
was inserted last is removed.
<p> All iterators that refer to the removed item are set to point to the
next item in the cache's traversal order.
<p> <p>See also <a href="#take">take</a>() and <a href="#clear">clear</a>().
<h3 class=fn>void <a name="setMaxCost"></a>QAsciiCache::setMaxCost ( int m )
</h3>
<p> Sets the maximum allowed total cost of the cache to <em>m</em>. If the
current total cost is greater than <em>m</em>, some items are removed
immediately.
<p> <p>See also <a href="#maxCost">maxCost</a>() and <a href="#totalCost">totalCost</a>().
<h3 class=fn>uint <a name="size"></a>QAsciiCache::size () const
</h3>
<p> Returns the size of the hash array used to implement the cache.
This should be a bit bigger than <a href="#count">count</a>() is likely to be.
<h3 class=fn>void <a name="statistics"></a>QAsciiCache::statistics () const
</h3>
<p> A debug-only utility function. Prints out cache usage, hit/miss, and
distribution information using <a href="qapplication.html#qDebug">qDebug</a>(). This function does nothing
in the release library.
<h3 class=fn>type * <a name="take"></a>QAsciiCache::take ( const char * k )
</h3>
<p> Takes the item associated with <em>k</em> out of the cache without
deleting it and returns a pointer to the item taken out, or null if
the key does not exist in the cache.
<p> If there are two or more items with equal keys, the one that
was inserted last is taken.
<p> All iterators that refer to the taken item are set to point to the
next item in the cache's traversal order.
<p> <p>See also <a href="#remove">remove</a>() and <a href="#clear">clear</a>().
<h3 class=fn>int <a name="totalCost"></a>QAsciiCache::totalCost () const
</h3>
<p> Returns the total cost of the items in the cache. This is an
integer in the range 0 to <a href="#maxCost">maxCost</a>().
<p> <p>See also <a href="#setMaxCost">setMaxCost</a>().
<!-- eof -->
<hr><p>
This file is part of the <a href="index.html">Qt toolkit</a>.
Copyright © 1995-2001
<a href="http://www.trolltech.com/">Trolltech</a>. All Rights Reserved.<p><address><hr><div align=center>
<table width=100% cellspacing=0 border=0><tr>
<td>Copyright © 2001
<a href="http://www.trolltech.com">Trolltech</a><td><a href="http://www.trolltech.com/trademarks.html">Trademarks</a>
<td align=right><div align=right>Qt version 3.0.2</div>
</table></div></address></body>
</html>
distrib
>
Mandriva
>
8.2
>
i586
>
media
>
contrib
>
by-pkgid
>
112b0974ad288f6cd55bf971ee6026a9
>
files
>
867
