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| <a name="glib-Type-Conversion-Macros"></a><div class="titlepage"></div> |
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| <td valign="top"> |
| <h2><span class="refentrytitle"><a name="glib-Type-Conversion-Macros.top_of_page"></a>Type Conversion Macros</span></h2> |
| <p>Type Conversion Macros — portably storing integers in pointer variables</p> |
| </td> |
| <td class="gallery_image" valign="top" align="right"></td> |
| </tr></table></div> |
| <div class="refsect1"> |
| <a name="glib-Type-Conversion-Macros.functions"></a><h2>Functions</h2> |
| <div class="informaltable"><table class="informaltable" width="100%" border="0"> |
| <colgroup> |
| <col width="150px" class="functions_return"> |
| <col class="functions_name"> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td class="define_keyword">#define</td> |
| <td class="function_name"> |
| <a class="link" href="glib-Type-Conversion-Macros.html#GINT-TO-POINTER:CAPS" title="GINT_TO_POINTER()">GINT_TO_POINTER</a><span class="c_punctuation">()</span> |
| </td> |
| </tr> |
| <tr> |
| <td class="define_keyword">#define</td> |
| <td class="function_name"> |
| <a class="link" href="glib-Type-Conversion-Macros.html#GPOINTER-TO-INT:CAPS" title="GPOINTER_TO_INT()">GPOINTER_TO_INT</a><span class="c_punctuation">()</span> |
| </td> |
| </tr> |
| <tr> |
| <td class="define_keyword">#define</td> |
| <td class="function_name"> |
| <a class="link" href="glib-Type-Conversion-Macros.html#GUINT-TO-POINTER:CAPS" title="GUINT_TO_POINTER()">GUINT_TO_POINTER</a><span class="c_punctuation">()</span> |
| </td> |
| </tr> |
| <tr> |
| <td class="define_keyword">#define</td> |
| <td class="function_name"> |
| <a class="link" href="glib-Type-Conversion-Macros.html#GPOINTER-TO-UINT:CAPS" title="GPOINTER_TO_UINT()">GPOINTER_TO_UINT</a><span class="c_punctuation">()</span> |
| </td> |
| </tr> |
| <tr> |
| <td class="define_keyword">#define</td> |
| <td class="function_name"> |
| <a class="link" href="glib-Type-Conversion-Macros.html#GSIZE-TO-POINTER:CAPS" title="GSIZE_TO_POINTER()">GSIZE_TO_POINTER</a><span class="c_punctuation">()</span> |
| </td> |
| </tr> |
| <tr> |
| <td class="define_keyword">#define</td> |
| <td class="function_name"> |
| <a class="link" href="glib-Type-Conversion-Macros.html#GPOINTER-TO-SIZE:CAPS" title="GPOINTER_TO_SIZE()">GPOINTER_TO_SIZE</a><span class="c_punctuation">()</span> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <div class="refsect1"> |
| <a name="glib-Type-Conversion-Macros.includes"></a><h2>Includes</h2> |
| <pre class="synopsis">#include <glib.h> |
| </pre> |
| </div> |
| <div class="refsect1"> |
| <a name="glib-Type-Conversion-Macros.description"></a><h2>Description</h2> |
| <p>Many times GLib, GTK+, and other libraries allow you to pass "user |
| data" to a callback, in the form of a void pointer. From time to time |
| you want to pass an integer instead of a pointer. You could allocate |
| an integer, with something like:</p> |
| <div class="informalexample"> |
| <table class="listing_frame" border="0" cellpadding="0" cellspacing="0"> |
| <tbody> |
| <tr> |
| <td class="listing_lines" align="right"><pre>1 |
| 2</pre></td> |
| <td class="listing_code"><pre class="programlisting"><span class="type">int</span><span class="normal"> </span><span class="symbol">*</span><span class="normal">ip </span><span class="symbol">=</span><span class="normal"> </span><span class="function"><a href="glib-Memory-Allocation.html#g-new">g_new</a></span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="symbol">,</span><span class="normal"> </span><span class="number">1</span><span class="symbol">);</span> |
| <span class="symbol">*</span><span class="normal">ip </span><span class="symbol">=</span><span class="normal"> </span><span class="number">42</span><span class="symbol">;</span></pre></td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| |
| <p> |
| But this is inconvenient, and it's annoying to have to free the |
| memory at some later time.</p> |
| <p>Pointers are always at least 32 bits in size (on all platforms GLib |
| intends to support). Thus you can store at least 32-bit integer values |
| in a pointer value. Naively, you might try this, but it's incorrect:</p> |
| <div class="informalexample"> |
| <table class="listing_frame" border="0" cellpadding="0" cellspacing="0"> |
| <tbody> |
| <tr> |
| <td class="listing_lines" align="right"><pre>1 |
| 2 |
| 3 |
| 4</pre></td> |
| <td class="listing_code"><pre class="programlisting"><span class="usertype">gpointer</span><span class="normal"> p</span><span class="symbol">;</span> |
| <span class="type">int</span><span class="normal"> i</span><span class="symbol">;</span> |
| <span class="normal">p </span><span class="symbol">=</span><span class="normal"> </span><span class="symbol">(</span><span class="type">void</span><span class="symbol">*)</span><span class="normal"> </span><span class="number">42</span><span class="symbol">;</span> |
| <span class="normal">i </span><span class="symbol">=</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="symbol">)</span><span class="normal"> p</span><span class="symbol">;</span></pre></td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| |
| <p> |
| Again, that example was not correct, don't copy it. |
| The problem is that on some systems you need to do this:</p> |
| <div class="informalexample"> |
| <table class="listing_frame" border="0" cellpadding="0" cellspacing="0"> |
| <tbody> |
| <tr> |
| <td class="listing_lines" align="right"><pre>1 |
| 2 |
| 3 |
| 4</pre></td> |
| <td class="listing_code"><pre class="programlisting"><span class="usertype">gpointer</span><span class="normal"> p</span><span class="symbol">;</span> |
| <span class="type">int</span><span class="normal"> i</span><span class="symbol">;</span> |
| <span class="normal">p </span><span class="symbol">=</span><span class="normal"> </span><span class="symbol">(</span><span class="type">void</span><span class="symbol">*)</span><span class="normal"> </span><span class="symbol">(</span><span class="type">long</span><span class="symbol">)</span><span class="normal"> </span><span class="number">42</span><span class="symbol">;</span> |
| <span class="normal">i </span><span class="symbol">=</span><span class="normal"> </span><span class="symbol">(</span><span class="type">int</span><span class="symbol">)</span><span class="normal"> </span><span class="symbol">(</span><span class="type">long</span><span class="symbol">)</span><span class="normal"> p</span><span class="symbol">;</span></pre></td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| |
| <p> |
| The GLib macros <a class="link" href="glib-Type-Conversion-Macros.html#GPOINTER-TO-INT:CAPS" title="GPOINTER_TO_INT()"><code class="function">GPOINTER_TO_INT()</code></a>, <a class="link" href="glib-Type-Conversion-Macros.html#GINT-TO-POINTER:CAPS" title="GINT_TO_POINTER()"><code class="function">GINT_TO_POINTER()</code></a>, etc. take care |
| to do the right thing on the every platform.</p> |
| <p>Warning: You may not store pointers in integers. This is not |
| portable in any way, shape or form. These macros only allow storing |
| integers in pointers, and only preserve 32 bits of the integer; values |
| outside the range of a 32-bit integer will be mangled.</p> |
| </div> |
| <div class="refsect1"> |
| <a name="glib-Type-Conversion-Macros.functions_details"></a><h2>Functions</h2> |
| <div class="refsect2"> |
| <a name="GINT-TO-POINTER:CAPS"></a><h3>GINT_TO_POINTER()</h3> |
| <pre class="programlisting">#define GINT_TO_POINTER(i) ((gpointer) (glong) (i)) |
| </pre> |
| <p>Stuffs an integer into a pointer type.</p> |
| <p>Remember, you may not store pointers in integers. This is not portable |
| in any way, shape or form. These macros only allow storing integers in |
| pointers, and only preserve 32 bits of the integer; values outside the |
| range of a 32-bit integer will be mangled.</p> |
| <div class="refsect3"> |
| <a name="GINT-TO-POINTER.parameters"></a><h4>Parameters</h4> |
| <div class="informaltable"><table class="informaltable" width="100%" border="0"> |
| <colgroup> |
| <col width="150px" class="parameters_name"> |
| <col class="parameters_description"> |
| <col width="200px" class="parameters_annotations"> |
| </colgroup> |
| <tbody><tr> |
| <td class="parameter_name"><p>i</p></td> |
| <td class="parameter_description"><p>integer to stuff into a pointer</p></td> |
| <td class="parameter_annotations"> </td> |
| </tr></tbody> |
| </table></div> |
| </div> |
| </div> |
| <hr> |
| <div class="refsect2"> |
| <a name="GPOINTER-TO-INT:CAPS"></a><h3>GPOINTER_TO_INT()</h3> |
| <pre class="programlisting">#define GPOINTER_TO_INT(p) ((gint) (glong) (p)) |
| </pre> |
| <p>Extracts an integer from a pointer. The integer must have |
| been stored in the pointer with <a class="link" href="glib-Type-Conversion-Macros.html#GINT-TO-POINTER:CAPS" title="GINT_TO_POINTER()"><code class="function">GINT_TO_POINTER()</code></a>.</p> |
| <p>Remember, you may not store pointers in integers. This is not portable |
| in any way, shape or form. These macros only allow storing integers in |
| pointers, and only preserve 32 bits of the integer; values outside the |
| range of a 32-bit integer will be mangled.</p> |
| <div class="refsect3"> |
| <a name="GPOINTER-TO-INT.parameters"></a><h4>Parameters</h4> |
| <div class="informaltable"><table class="informaltable" width="100%" border="0"> |
| <colgroup> |
| <col width="150px" class="parameters_name"> |
| <col class="parameters_description"> |
| <col width="200px" class="parameters_annotations"> |
| </colgroup> |
| <tbody><tr> |
| <td class="parameter_name"><p>p</p></td> |
| <td class="parameter_description"><p>pointer containing an integer</p></td> |
| <td class="parameter_annotations"> </td> |
| </tr></tbody> |
| </table></div> |
| </div> |
| </div> |
| <hr> |
| <div class="refsect2"> |
| <a name="GUINT-TO-POINTER:CAPS"></a><h3>GUINT_TO_POINTER()</h3> |
| <pre class="programlisting">#define GUINT_TO_POINTER(u) ((gpointer) (gulong) (u)) |
| </pre> |
| <p>Stuffs an unsigned integer into a pointer type.</p> |
| <div class="refsect3"> |
| <a name="GUINT-TO-POINTER.parameters"></a><h4>Parameters</h4> |
| <div class="informaltable"><table class="informaltable" width="100%" border="0"> |
| <colgroup> |
| <col width="150px" class="parameters_name"> |
| <col class="parameters_description"> |
| <col width="200px" class="parameters_annotations"> |
| </colgroup> |
| <tbody><tr> |
| <td class="parameter_name"><p>u</p></td> |
| <td class="parameter_description"><p>unsigned integer to stuff into the pointer</p></td> |
| <td class="parameter_annotations"> </td> |
| </tr></tbody> |
| </table></div> |
| </div> |
| </div> |
| <hr> |
| <div class="refsect2"> |
| <a name="GPOINTER-TO-UINT:CAPS"></a><h3>GPOINTER_TO_UINT()</h3> |
| <pre class="programlisting">#define GPOINTER_TO_UINT(p) ((guint) (gulong) (p)) |
| </pre> |
| <p>Extracts an unsigned integer from a pointer. The integer must have |
| been stored in the pointer with <a class="link" href="glib-Type-Conversion-Macros.html#GUINT-TO-POINTER:CAPS" title="GUINT_TO_POINTER()"><code class="function">GUINT_TO_POINTER()</code></a>.</p> |
| <div class="refsect3"> |
| <a name="GPOINTER-TO-UINT.parameters"></a><h4>Parameters</h4> |
| <div class="informaltable"><table class="informaltable" width="100%" border="0"> |
| <colgroup> |
| <col width="150px" class="parameters_name"> |
| <col class="parameters_description"> |
| <col width="200px" class="parameters_annotations"> |
| </colgroup> |
| <tbody><tr> |
| <td class="parameter_name"><p>p</p></td> |
| <td class="parameter_description"><p>pointer to extract an unsigned integer from</p></td> |
| <td class="parameter_annotations"> </td> |
| </tr></tbody> |
| </table></div> |
| </div> |
| </div> |
| <hr> |
| <div class="refsect2"> |
| <a name="GSIZE-TO-POINTER:CAPS"></a><h3>GSIZE_TO_POINTER()</h3> |
| <pre class="programlisting">#define GSIZE_TO_POINTER(s) ((gpointer) (gsize) (s)) |
| </pre> |
| <p>Stuffs a <a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a> into a pointer type.</p> |
| <div class="refsect3"> |
| <a name="GSIZE-TO-POINTER.parameters"></a><h4>Parameters</h4> |
| <div class="informaltable"><table class="informaltable" width="100%" border="0"> |
| <colgroup> |
| <col width="150px" class="parameters_name"> |
| <col class="parameters_description"> |
| <col width="200px" class="parameters_annotations"> |
| </colgroup> |
| <tbody><tr> |
| <td class="parameter_name"><p>s</p></td> |
| <td class="parameter_description"><p><a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a> to stuff into the pointer</p></td> |
| <td class="parameter_annotations"> </td> |
| </tr></tbody> |
| </table></div> |
| </div> |
| </div> |
| <hr> |
| <div class="refsect2"> |
| <a name="GPOINTER-TO-SIZE:CAPS"></a><h3>GPOINTER_TO_SIZE()</h3> |
| <pre class="programlisting">#define GPOINTER_TO_SIZE(p) ((gsize) (p)) |
| </pre> |
| <p>Extracts a <a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a> from a pointer. The <a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a> must have |
| been stored in the pointer with <a class="link" href="glib-Type-Conversion-Macros.html#GSIZE-TO-POINTER:CAPS" title="GSIZE_TO_POINTER()"><code class="function">GSIZE_TO_POINTER()</code></a>.</p> |
| <div class="refsect3"> |
| <a name="GPOINTER-TO-SIZE.parameters"></a><h4>Parameters</h4> |
| <div class="informaltable"><table class="informaltable" width="100%" border="0"> |
| <colgroup> |
| <col width="150px" class="parameters_name"> |
| <col class="parameters_description"> |
| <col width="200px" class="parameters_annotations"> |
| </colgroup> |
| <tbody><tr> |
| <td class="parameter_name"><p>p</p></td> |
| <td class="parameter_description"><p>pointer to extract a <a class="link" href="glib-Basic-Types.html#gsize" title="gsize"><span class="type">gsize</span></a> from</p></td> |
| <td class="parameter_annotations"> </td> |
| </tr></tbody> |
| </table></div> |
| </div> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a name="glib-Type-Conversion-Macros.other_details"></a><h2>Types and Values</h2> |
| </div> |
| </div> |
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