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boost 2: shared_ptr wraps resource handles

, 16 Nov 2004
Using boost, we can write "almost perfect" wrappers for GDI and other resource handles, in a few lines of code.
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HandleRef
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<title>HandleRef:  TemplateCHandleRefT&lt; HDL, DELETER &gt; class Reference</title>
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<h1>CHandleRefT&lt; HDL, DELETER &gt; Class Template Reference</h1><code>#include &lt;<a class="el" href="handleref_8h-source.html">handleref.h</a>&gt;</code>
<p>
<hr><a name="_details"></a><h2>Detailed Description</h2>
<h3>template&lt;class HDL, class DELETER&gt;<br>
 class CHandleRefT&lt; HDL, DELETER &gt;</h3>

Template class implementing a counted reference to a windows resource handle. 
<p>
Usage rules are similar to a reference counted smart pointer.<p>
<dl compact><dt><b>template parameters:</b></dt><dd><ul>
<li><code>HDL</code> : type of the resource handle (e.g. HFONT)</li><li><code>DELETER</code> : a functor releasing the resources of Handle of type HDL (e.g. a functor calling DeleteObject). The handle is passed as void *.</li></ul>
</dd></dl>
<dl compact><dt><b>Automatic vs. manual handles</b></dt><dd>When constructing a HandleRef from a raw handle, you pass a <code>bDeleteOnRelease</code> flag indicating if the handle should be released automatically when the last reference to it goes out of scope. <br>
<br>
 For an automatic handle, assign the raw handle to a HandleRef immediately after construction, specifying bDeleteOnRelease=true. Then then pass it around only as HandleRef. This guarantees the handle is deleted when it is no longer used. <br>
<br>
 For a manual handle, that you will delete yourself manually, or that must not be deleted, specify <code>bDeleteOnRelease=false</code>. <br>
<br>
 The idea here is that you can pass around, copy, store, or return a HandleRef, it remembers it's deletion policy.</dd></dl>
<dl compact><dt><b>Guidelines</b></dt><dd>Utility functions that merely receive and use a resource handle (without storing it) may use the raw handle as argument. However, when the Handle is stored (e.g. as a class member) or used as a return value from a function, a HandleRef is recommended. </dd></dl>

<p>

<p>
Definition at line <a class="el" href="handleref_8h-source.html#l00160">160</a> of file <a class="el" href="handleref_8h-source.html">handleref.h</a>.<table border=0 cellpadding=0 cellspacing=0>
<tr><td></td></tr>
<tr><td colspan=2><br><h2>Public Member Functions</h2></td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>&nbsp;</td><td class="memItemRight" valign=bottom><a class="el" href="classCHandleRefT.html#a0">CHandleRefT</a> ()</td></tr>

<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">creates a null handle  <a href="#a0"></a><br><br></td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>&nbsp;</td><td class="memItemRight" valign=bottom><a class="el" href="classCHandleRefT.html#a1">CHandleRefT</a> (HDL h, bool deleteOnRelease)</td></tr>

<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">Initialize the Handle Reference with a handle.  <a href="#a1"></a><br><br></td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>&nbsp;</td><td class="memItemRight" valign=bottom><a class="el" href="classCHandleRefT.html#a2">operator HDL</a> () const </td></tr>

<tr><td class="mdescLeft">&nbsp;</td><td class="mdescRight">automatic cast to the handle type  <a href="#a2"></a><br><br></td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>void&nbsp;</td><td class="memItemRight" valign=bottom><a class="el" href="classCHandleRefT.html#a3">reset</a> ()</td></tr>

<tr><td colspan=2><br><h2>Protected Types</h2></td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top>typedef boost::shared_ptr&lt;<br>
 void &gt;&nbsp;</td><td class="memItemRight" valign=bottom><a class="el" href="classCHandleRefT.html#x0">tBoostSP</a></td></tr>

<tr><td colspan=2><br><h2>Protected Attributes</h2></td></tr>
<tr><td class="memItemLeft" nowrap align=right valign=top><a class="el" href="classCHandleRefT.html#x0">tBoostSP</a>&nbsp;</td><td class="memItemRight" valign=bottom><a class="el" href="classCHandleRefT.html#p0">m_ptr</a></td></tr>

</table>
<hr><h2>Member Typedef Documentation</h2>
<a class="anchor" name="x0" doxytag="CHandleRefT::tBoostSP" ></a><p>
<table class="mdTable" width="100%" cellpadding="2" cellspacing="0">
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template&lt;class HDL, class DELETER&gt; </td>
        </tr>
        <tr>
          <td class="md" nowrap valign="top"> typedef boost::shared_ptr&lt;void&gt; <a class="el" href="classCHandleRefT.html">CHandleRefT</a>&lt; HDL, DELETER &gt;::<a class="el" href="classCHandleRefT.html#x0">tBoostSP</a><code> [protected]</code>
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    </td>
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  <tr>
    <td>
      &nbsp;
    </td>
    <td>

<p>

<p>
Definition at line <a class="el" href="handleref_8h-source.html#l00163">163</a> of file <a class="el" href="handleref_8h-source.html">handleref.h</a>.    </td>
  </tr>
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<hr><h2>Constructor &amp; Destructor Documentation</h2>
<a class="anchor" name="a0" doxytag="CHandleRefT::CHandleRefT" ></a><p>
<table class="mdTable" width="100%" cellpadding="2" cellspacing="0">
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template&lt;class HDL, class DELETER&gt; </td>
        </tr>
        <tr>
          <td class="md" nowrap valign="top"> <a class="el" href="classCHandleRefT.html">CHandleRefT</a>&lt; HDL, DELETER &gt;::<a class="el" href="classCHandleRefT.html">CHandleRefT</a> </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="mdname1" valign="top" nowrap>          </td>
          <td class="md" valign="top">&nbsp;)&nbsp;</td>
          <td class="md" nowrap><code> [inline]</code></td>
        </tr>

      </table>
    </td>
  </tr>
</table>
<table cellspacing=5 cellpadding=0 border=0>
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    <td>
      &nbsp;
    </td>
    <td>

<p>
creates a null handle 
<p>

<p>
Definition at line <a class="el" href="handleref_8h-source.html#l00169">169</a> of file <a class="el" href="handleref_8h-source.html">handleref.h</a>.    </td>
  </tr>
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<a class="anchor" name="a1" doxytag="CHandleRefT::CHandleRefT" ></a><p>
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template&lt;class HDL, class DELETER&gt; </td>
        </tr>
        <tr>
          <td class="md" nowrap valign="top"> <a class="el" href="classCHandleRefT.html">CHandleRefT</a>&lt; HDL, DELETER &gt;::<a class="el" href="classCHandleRefT.html">CHandleRefT</a> </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="md" nowrap valign="top">HDL&nbsp;</td>
          <td class="mdname" nowrap> <em>h</em>, </td>
        </tr>
        <tr>
          <td></td>
          <td></td>
          <td class="md" nowrap>bool&nbsp;</td>
          <td class="mdname" nowrap> <em>deleteOnRelease</em></td>
        </tr>
        <tr>
          <td></td>
          <td class="md">)&nbsp;</td>
          <td class="md" colspan="2"><code> [inline, explicit]</code></td>
        </tr>

      </table>
    </td>
  </tr>
</table>
<table cellspacing=5 cellpadding=0 border=0>
  <tr>
    <td>
      &nbsp;
    </td>
    <td>

<p>
Initialize the Handle Reference with a handle. 
<p>
<dl compact><dt><b>Parameters:</b></dt><dd>
  <table border="0" cellspacing="2" cellpadding="0">
    <tr><td valign=top><em>h</em>&nbsp;</td><td>: Handle to the resource to (of type <code>HDL</code>) </td></tr>
    <tr><td valign=top><em>deleteOnRelease</em>&nbsp;</td><td>[bool]: if true, the handle is deleted automatically (using the specified <code>DELETER</code>) when the last HandleRef goes put of scope. </td></tr>
  </table>
</dl>

<p>
Definition at line <a class="el" href="handleref_8h-source.html#l00175">175</a> of file <a class="el" href="handleref_8h-source.html">handleref.h</a>.    </td>
  </tr>
</table>
<hr><h2>Member Function Documentation</h2>
<a class="anchor" name="a2" doxytag="CHandleRefT::operator HDL" ></a><p>
<table class="mdTable" width="100%" cellpadding="2" cellspacing="0">
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template&lt;class HDL, class DELETER&gt; </td>
        </tr>
        <tr>
          <td class="md" nowrap valign="top"> <a class="el" href="classCHandleRefT.html">CHandleRefT</a>&lt; HDL, DELETER &gt;::operator HDL </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="mdname1" valign="top" nowrap>          </td>
          <td class="md" valign="top">&nbsp;)&nbsp;</td>
          <td class="md" nowrap> const<code> [inline]</code></td>
        </tr>

      </table>
    </td>
  </tr>
</table>
<table cellspacing=5 cellpadding=0 border=0>
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    <td>
      &nbsp;
    </td>
    <td>

<p>
automatic cast to the handle type 
<p>

<p>
Definition at line <a class="el" href="handleref_8h-source.html#l00184">184</a> of file <a class="el" href="handleref_8h-source.html">handleref.h</a>.    </td>
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<a class="anchor" name="a3" doxytag="CHandleRefT::reset" ></a><p>
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template&lt;class HDL, class DELETER&gt; </td>
        </tr>
        <tr>
          <td class="md" nowrap valign="top"> void <a class="el" href="classCHandleRefT.html">CHandleRefT</a>&lt; HDL, DELETER &gt;::reset </td>
          <td class="md" valign="top">(&nbsp;</td>
          <td class="mdname1" valign="top" nowrap>          </td>
          <td class="md" valign="top">&nbsp;)&nbsp;</td>
          <td class="md" nowrap><code> [inline]</code></td>
        </tr>

      </table>
    </td>
  </tr>
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<table cellspacing=5 cellpadding=0 border=0>
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      &nbsp;
    </td>
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<p>

<p>
Definition at line <a class="el" href="handleref_8h-source.html#l00186">186</a> of file <a class="el" href="handleref_8h-source.html">handleref.h</a>.    </td>
  </tr>
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<hr><h2>Field Documentation</h2>
<a class="anchor" name="p0" doxytag="CHandleRefT::m_ptr" ></a><p>
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template&lt;class HDL, class DELETER&gt; </td>
        </tr>
        <tr>
          <td class="md" nowrap valign="top"> <a class="el" href="classCHandleRefT.html#x0">tBoostSP</a> <a class="el" href="classCHandleRefT.html">CHandleRefT</a>&lt; HDL, DELETER &gt;::<a class="el" href="classCHandleRefT.html#p0">m_ptr</a><code> [protected]</code>
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      &nbsp;
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<p>

<p>
Definition at line <a class="el" href="handleref_8h-source.html#l00164">164</a> of file <a class="el" href="handleref_8h-source.html">handleref.h</a>.    </td>
  </tr>
</table>
<hr>The documentation for this class was generated from the following file:<ul>
<li><a class="el" href="handleref_8h-source.html">handleref.h</a></ul>
<hr size="1"><address style="align: right;"><small>Generated on Tue Nov 16 22:21:51 2004 for HandleRef by
<a href="http://www.doxygen.org/index.html">
<img src="doxygen.png" alt="doxygen" align="middle" border=0 > 
</a>1.3.5 </small></address>
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