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<tr><td colspan="5" class="shortcuts"><nobr><a href="#id3302655" class="shortcut">Top</a>
 | 
<a href="#id3303016" class="shortcut">Description</a></nobr></td></tr>
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<div class="refentry" lang="en">
<a name="glib-Relations-and-Tuples"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2>
<a name="id3302655"></a><span class="refentrytitle">Relations and Tuples</span>
</h2>
<p>Relations and Tuples — tables of data which can be indexed on any number of fields.</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<pre class="synopsis">
#include <glib.h>
<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a>;
<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a>* <a href="glib-Relations-and-Tuples.html#g-relation-new">g_relation_new</a> (<a href="glib-Basic-Types.html#gint">gint</a> fields);
void <a href="glib-Relations-and-Tuples.html#g-relation-index">g_relation_index</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
<a href="glib-Basic-Types.html#gint">gint</a> field,
<a href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_func,
<a href="glib-Hash-Tables.html#GEqualFunc">GEqualFunc</a> key_equal_func);
void <a href="glib-Relations-and-Tuples.html#g-relation-insert">g_relation_insert</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
...);
<a href="glib-Basic-Types.html#gboolean">gboolean</a> <a href="glib-Relations-and-Tuples.html#g-relation-exists">g_relation_exists</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
...);
<a href="glib-Basic-Types.html#gint">gint</a> <a href="glib-Relations-and-Tuples.html#g-relation-count">g_relation_count</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
<a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key,
<a href="glib-Basic-Types.html#gint">gint</a> field);
<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a>* <a href="glib-Relations-and-Tuples.html#g-relation-select">g_relation_select</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
<a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key,
<a href="glib-Basic-Types.html#gint">gint</a> field);
<a href="glib-Basic-Types.html#gint">gint</a> <a href="glib-Relations-and-Tuples.html#g-relation-delete">g_relation_delete</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
<a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key,
<a href="glib-Basic-Types.html#gint">gint</a> field);
void <a href="glib-Relations-and-Tuples.html#g-relation-destroy">g_relation_destroy</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation);
void <a href="glib-Relations-and-Tuples.html#g-relation-print">g_relation_print</a> (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation);
<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a>;
void <a href="glib-Relations-and-Tuples.html#g-tuples-destroy">g_tuples_destroy</a> (<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a> *tuples);
<a href="glib-Basic-Types.html#gpointer">gpointer</a> <a href="glib-Relations-and-Tuples.html#g-tuples-index">g_tuples_index</a> (<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a> *tuples,
<a href="glib-Basic-Types.html#gint">gint</a> index_,
<a href="glib-Basic-Types.html#gint">gint</a> field);
</pre>
</div>
<div class="refsect1" lang="en">
<a name="id3303016"></a><h2>Description</h2>
<p>
A <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> is a table of data which can be indexed on any number of fields,
rather like simple database tables. A <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> contains a number of
records, called tuples. Each record contains a number of fields.
Records are not ordered, so it is not possible to find the record at a
particular index.
</p>
<p>
Note that <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> tables are currently limited to 2 fields.
</p>
<p>
To create a GRelation, use <a href="glib-Relations-and-Tuples.html#g-relation-new"><code class="function">g_relation_new()</code></a>.
</p>
<p>
To specify which fields should be indexed, use <a href="glib-Relations-and-Tuples.html#g-relation-index"><code class="function">g_relation_index()</code></a>.
Note that this must be called before any tuples are added to the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</p>
<p>
To add records to a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> use <a href="glib-Relations-and-Tuples.html#g-relation-insert"><code class="function">g_relation_insert()</code></a>.
</p>
<p>
To determine if a given record appears in a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>, use
<a href="glib-Relations-and-Tuples.html#g-relation-exists"><code class="function">g_relation_exists()</code></a>. Note that fields are compared directly, so pointers
must point to the exact same position (i.e. different copies of the same
string will not match.)
</p>
<p>
To count the number of records which have a particular value in a given
field, use <a href="glib-Relations-and-Tuples.html#g-relation-count"><code class="function">g_relation_count()</code></a>.
</p>
<p>
To get all the records which have a particular value in a given field,
use <a href="glib-Relations-and-Tuples.html#g-relation-select"><code class="function">g_relation_select()</code></a>. To access fields of the resulting records,
use <a href="glib-Relations-and-Tuples.html#g-tuples-index"><code class="function">g_tuples_index()</code></a>. To free the resulting records use <a href="glib-Relations-and-Tuples.html#g-tuples-destroy"><code class="function">g_tuples_destroy()</code></a>.
</p>
<p>
To delete all records which have a particular value in a given field,
use <a href="glib-Relations-and-Tuples.html#g-relation-delete"><code class="function">g_relation_delete()</code></a>.
</p>
<p>
To destroy the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>, use <a href="glib-Relations-and-Tuples.html#g-relation-destroy"><code class="function">g_relation_destroy()</code></a>.
</p>
<p>
To help debug <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> objects, use <a href="glib-Relations-and-Tuples.html#g-relation-print"><code class="function">g_relation_print()</code></a>.
</p>
</div>
<div class="refsect1" lang="en">
<a name="id3303260"></a><h2>Details</h2>
<div class="refsect2" lang="en">
<a name="id3303270"></a><h3>
<a name="GRelation"></a>GRelation</h3>
<a class="indexterm" name="id3303283"></a><pre class="programlisting">typedef struct _GRelation GRelation;</pre>
<p>
The <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> struct is an opaque data structure to represent a
<a href="glib-Relations-and-Tuples.html" title="Relations and Tuples">Relation</a>.
It should only be accessed via the following functions.
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3303317"></a><h3>
<a name="g-relation-new"></a>g_relation_new ()</h3>
<a class="indexterm" name="id3303329"></a><pre class="programlisting"><a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a>* g_relation_new (<a href="glib-Basic-Types.html#gint">gint</a> fields);</pre>
<p>
Creates a new <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> with the given number of fields.
Note that currently the number of fields must be 2.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>fields</code></em> :</span></td>
<td>the number of fields.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>a new <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3303404"></a><h3>
<a name="g-relation-index"></a>g_relation_index ()</h3>
<a class="indexterm" name="id3303416"></a><pre class="programlisting">void g_relation_index (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
<a href="glib-Basic-Types.html#gint">gint</a> field,
<a href="glib-Hash-Tables.html#GHashFunc">GHashFunc</a> hash_func,
<a href="glib-Hash-Tables.html#GEqualFunc">GEqualFunc</a> key_equal_func);</pre>
<p>
Creates an index on the given field.
Note that this must be called before any records are added to the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>relation</code></em> :</span></td>
<td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>field</code></em> :</span></td>
<td>the field to index, counting from 0.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>hash_func</code></em> :</span></td>
<td>a function to produce a hash value from the field data.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>key_equal_func</code></em> :</span></td>
<td>a function to compare two values of the given field.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3303546"></a><h3>
<a name="g-relation-insert"></a>g_relation_insert ()</h3>
<a class="indexterm" name="id3303559"></a><pre class="programlisting">void g_relation_insert (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
...);</pre>
<p>
Inserts a record into a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>relation</code></em> :</span></td>
<td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>...</code></em> :</span></td>
<td>the fields of the record to add. These must match the number of
fields in the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>, and of type <a href="glib-Basic-Types.html#gpointer"><span class="type">gpointer</span></a> or <a href="glib-Basic-Types.html#gconstpointer"><span class="type">gconstpointer</span></a>.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3303660"></a><h3>
<a name="g-relation-exists"></a>g_relation_exists ()</h3>
<a class="indexterm" name="id3303674"></a><pre class="programlisting"><a href="glib-Basic-Types.html#gboolean">gboolean</a> g_relation_exists (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
...);</pre>
<p>
Returns <a href="glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if a record with the given values exists in a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
Note that the values are compared directly, so that, for example, two
copies of the same string will not match.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>relation</code></em> :</span></td>
<td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>...</code></em> :</span></td>
<td>the fields of the record to compare. The number must match the
number of fields in the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>
<a href="glib-Standard-Macros.html#TRUE:CAPS"><code class="literal">TRUE</code></a> if a record matches.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3303791"></a><h3>
<a name="g-relation-count"></a>g_relation_count ()</h3>
<a class="indexterm" name="id3303804"></a><pre class="programlisting"><a href="glib-Basic-Types.html#gint">gint</a> g_relation_count (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
<a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key,
<a href="glib-Basic-Types.html#gint">gint</a> field);</pre>
<p>
Returns the number of tuples in a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> that have the given value
in the given field.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>relation</code></em> :</span></td>
<td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>key</code></em> :</span></td>
<td>the value to compare with.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>field</code></em> :</span></td>
<td>the field of each record to match.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>the number of matches.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3303921"></a><h3>
<a name="g-relation-select"></a>g_relation_select ()</h3>
<a class="indexterm" name="id3303935"></a><pre class="programlisting"><a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a>* g_relation_select (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
<a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key,
<a href="glib-Basic-Types.html#gint">gint</a> field);</pre>
<p>
Returns all of the tuples which have the given key in the given field.
Use <a href="glib-Relations-and-Tuples.html#g-tuples-index"><code class="function">g_tuples_index()</code></a> to access the returned records.
The returned records should be freed with <a href="glib-Relations-and-Tuples.html#g-tuples-destroy"><code class="function">g_tuples_destroy()</code></a>.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>relation</code></em> :</span></td>
<td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>key</code></em> :</span></td>
<td>the value to compare with.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>field</code></em> :</span></td>
<td>the field of each record to match.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>the records (tuples) that matched.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3304066"></a><h3>
<a name="g-relation-delete"></a>g_relation_delete ()</h3>
<a class="indexterm" name="id3304079"></a><pre class="programlisting"><a href="glib-Basic-Types.html#gint">gint</a> g_relation_delete (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation,
<a href="glib-Basic-Types.html#gconstpointer">gconstpointer</a> key,
<a href="glib-Basic-Types.html#gint">gint</a> field);</pre>
<p>
Deletes any records from a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> that have the given key value in
the given field.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>relation</code></em> :</span></td>
<td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>key</code></em> :</span></td>
<td>the value to compare with.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>field</code></em> :</span></td>
<td>the field of each record to match.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>the number of records deleted.
</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3304196"></a><h3>
<a name="g-relation-destroy"></a>g_relation_destroy ()</h3>
<a class="indexterm" name="id3304209"></a><pre class="programlisting">void g_relation_destroy (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation);</pre>
<p>
Destroys the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>, freeing all memory allocated.
However, it does not free memory allocated for the
tuple data, so you should free that first if appropriate.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>relation</code></em> :</span></td>
<td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3304274"></a><h3>
<a name="g-relation-print"></a>g_relation_print ()</h3>
<a class="indexterm" name="id3304287"></a><pre class="programlisting">void g_relation_print (<a href="glib-Relations-and-Tuples.html#GRelation">GRelation</a> *relation);</pre>
<p>
Outputs information about all records in a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>, as well as the indexes.
It is for debugging.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>relation</code></em> :</span></td>
<td>a <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id3304350"></a><h3>
<a name="GTuples"></a>GTuples</h3>
<a class="indexterm" name="id3304363"></a><pre class="programlisting">typedef struct {
guint len;
} GTuples;
</pre>
<p>
The <a href="glib-Relations-and-Tuples.html#GTuples"><span class="type">GTuples</span></a> struct is used to return records (or tuples) from the
<a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a> by <a href="glib-Relations-and-Tuples.html#g-relation-select"><code class="function">g_relation_select()</code></a>.
It only contains one public member - the number of records that matched.
To access the matched records, you must use <a href="glib-Relations-and-Tuples.html#g-tuples-index"><code class="function">g_tuples_index()</code></a>.
</p>
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<td>
<span class="term"><a href="glib-Basic-Types.html#guint">guint</a> <em class="structfield"><code>len</code></em>;</span></td>
<td>the number of records that matched.
</td>
</tr></tbody>
</table></div>
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<div class="refsect2" lang="en">
<a name="id3304443"></a><h3>
<a name="g-tuples-destroy"></a>g_tuples_destroy ()</h3>
<a class="indexterm" name="id3304455"></a><pre class="programlisting">void g_tuples_destroy (<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a> *tuples);</pre>
<p>
Frees the records which were returned by <a href="glib-Relations-and-Tuples.html#g-relation-select"><code class="function">g_relation_select()</code></a>.
This should always be called after <a href="glib-Relations-and-Tuples.html#g-relation-select"><code class="function">g_relation_select()</code></a> when you are
finished with the records.
The records are not removed from the <a href="glib-Relations-and-Tuples.html#GRelation"><span class="type">GRelation</span></a>.
</p>
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<td>
<span class="term"><em class="parameter"><code>tuples</code></em> :</span></td>
<td>the tuple data to free.
</td>
</tr></tbody>
</table></div>
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<div class="refsect2" lang="en">
<a name="id3304533"></a><h3>
<a name="g-tuples-index"></a>g_tuples_index ()</h3>
<a class="indexterm" name="id3304546"></a><pre class="programlisting"><a href="glib-Basic-Types.html#gpointer">gpointer</a> g_tuples_index (<a href="glib-Relations-and-Tuples.html#GTuples">GTuples</a> *tuples,
<a href="glib-Basic-Types.html#gint">gint</a> index_,
<a href="glib-Basic-Types.html#gint">gint</a> field);</pre>
<p>
Gets a field from the records returned by <a href="glib-Relations-and-Tuples.html#g-relation-select"><code class="function">g_relation_select()</code></a>.
It returns the given field of the record at the given index.
The returned value should not be changed.
</p>
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<td>
<span class="term"><em class="parameter"><code>tuples</code></em> :</span></td>
<td>the tuple data, returned by <a href="glib-Relations-and-Tuples.html#g-relation-select"><code class="function">g_relation_select()</code></a>.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>index_</code></em> :</span></td>
<td>the index of the record.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>field</code></em> :</span></td>
<td>the field to return.
</td>
</tr>
<tr>
<td>
<span class="term"><span class="emphasis"><em>Returns</em></span> :</span></td>
<td>the field of the record.
</td>
</tr>
</tbody>
</table></div>
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