generic_values.sgml

GLib是GTK+和GNOME工程的基础底层核心程序库

<refsect2>
<title><anchor id="g-value-copy">g_value_copy ()</title>
<programlisting>void        g_value_copy                    (const <link linkend="GValue">GValue</link> *src_value,
                                             <link linkend="GValue">GValue</link> *dest_value);</programlisting>
<para>
Copies the value of <parameter>src_value</parameter> into <parameter>dest_value</parameter>.
</para><informaltable pgwide="1" frame="none" role="params">
<tgroup cols="2">
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<row><entry align="right"><parameter>src_value</parameter>&nbsp;:</entry>
<entry>	An initialized <link linkend="GValue">GValue</link> structure.
</entry></row>
<row><entry align="right"><parameter>dest_value</parameter>&nbsp;:</entry>
<entry>	An initialized <link linkend="GValue">GValue</link> structure of the same type as <parameter>src_value</parameter>.


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-value-reset">g_value_reset ()</title>
<programlisting><link linkend="GValue">GValue</link>*     g_value_reset                   (<link linkend="GValue">GValue</link> *value);</programlisting>
<para>
Clears the current value in <parameter>value</parameter> and resets it to the default value
(as if the value had just been initialized).
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>value</parameter>&nbsp;:</entry>
<entry>	An initialized <link linkend="GValue">GValue</link> structure.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-value-unset">g_value_unset ()</title>
<programlisting>void        g_value_unset                   (<link linkend="GValue">GValue</link> *value);</programlisting>
<para>
Clears the current value in <parameter>value</parameter> and "unsets" the type,
this releases all resources associated with this GValue.
An unset value is the same as an uninitialized (zero-filled)
<link linkend="GValue">GValue</link> structure.
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>value</parameter>&nbsp;:</entry>
<entry>	An initialized <link linkend="GValue">GValue</link> structure.


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-value-fits-pointer">g_value_fits_pointer ()</title>
<programlisting><link linkend="gboolean">gboolean</link>    g_value_fits_pointer            (const <link linkend="GValue">GValue</link> *value);</programlisting>
<para>
Determines if <parameter>value</parameter> will fit inside the size of a pointer value.
This is an internal function introduced mainly for C marshallers.
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>value</parameter>&nbsp;:</entry>
<entry>		An initialized <link linkend="GValue">GValue</link> structure.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>	<link linkend="TRUE-CAPS">TRUE</link> if <parameter>value</parameter> will fit inside a pointer value.


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-value-peek-pointer">g_value_peek_pointer ()</title>
<programlisting><link linkend="gpointer">gpointer</link>    g_value_peek_pointer            (const <link linkend="GValue">GValue</link> *value);</programlisting>
<para>
Return the value contents as pointer. This function asserts that
<link linkend="g-value-fits-pointer">g_value_fits_pointer</link>() returned <link linkend="TRUE-CAPS">TRUE</link> for the passed in value.
This is an internal function introduced mainly for C marshallers.
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>value</parameter>&nbsp;:</entry>
<entry>		An initialized <link linkend="GValue">GValue</link> structure.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>	<link linkend="TRUE-CAPS">TRUE</link> if <parameter>value</parameter> will fit inside a pointer value.


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-value-type-compatible">g_value_type_compatible ()</title>
<programlisting><link linkend="gboolean">gboolean</link>    g_value_type_compatible         (<link linkend="GType">GType</link> src_type,
                                             <link linkend="GType">GType</link> dest_type);</programlisting>
<para>
Returns whether a <link linkend="GValue">GValue</link> of type <parameter>src_type</parameter> can be copied into
a <link linkend="GValue">GValue</link> of type <parameter>dest_type</parameter>.
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>src_type</parameter>&nbsp;:</entry>
<entry> source type to be copied.
</entry></row>
<row><entry align="right"><parameter>dest_type</parameter>&nbsp;:</entry>
<entry>destination type for copying.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>  <literal>TRUE</literal> if <link linkend="g-value-copy">g_value_copy</link>() is possible with <parameter>src_type</parameter> and <parameter>dest_type</parameter>.


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-value-type-transformable">g_value_type_transformable ()</title>
<programlisting><link linkend="gboolean">gboolean</link>    g_value_type_transformable      (<link linkend="GType">GType</link> src_type,
                                             <link linkend="GType">GType</link> dest_type);</programlisting>
<para>
Check whether <link linkend="g-value-transform">g_value_transform</link>() is able to transform values
of type <parameter>src_type</parameter> into values of type <parameter>dest_type</parameter>.
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>src_type</parameter>&nbsp;:</entry>
<entry> Source type.
</entry></row>
<row><entry align="right"><parameter>dest_type</parameter>&nbsp;:</entry>
<entry>Target type.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>  <literal>TRUE</literal> if the transformation is possible, <literal>FALSE</literal> otherwise.


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-value-transform">g_value_transform ()</title>
<programlisting><link linkend="gboolean">gboolean</link>    g_value_transform               (const <link linkend="GValue">GValue</link> *src_value,
                                             <link linkend="GValue">GValue</link> *dest_value);</programlisting>
<para>
Tries to cast the contents of <parameter>src_value</parameter> into a type apropriate
to store in <parameter>dest_value</parameter>, e.g. to transform a <literal>G_TYPE_INT</literal> value
into a <literal>G_TYPE_FLOAT</literal> value. Performing transformations between
value types might incour precision lossage. Especially
transformations into strings might reveal seemingly arbitrary
results and shouldn't be relied upon for production code (such
as rcfile value or object property serialization).
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>src_value</parameter>&nbsp;:</entry>
<entry> Source value.
</entry></row>
<row><entry align="right"><parameter>dest_value</parameter>&nbsp;:</entry>
<entry>Target value.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>   Whether a transformation rule was found and could be applied.
             Upon failing transformations, <parameter>dest_value</parameter> is left untouched.


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="GValueTransform">GValueTransform ()</title>
<programlisting>void        (*GValueTransform)              (const <link linkend="GValue">GValue</link> *src_value,
                                             <link linkend="GValue">GValue</link> *dest_value);</programlisting>
<para>

</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>src_value</parameter>&nbsp;:</entry>
<entry>
</entry></row>
<row><entry align="right"><parameter>dest_value</parameter>&nbsp;:</entry>
<entry>


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-value-register-transform-func">g_value_register_transform_func ()</title>
<programlisting>void        g_value_register_transform_func (<link linkend="GType">GType</link> src_type,
                                             <link linkend="GType">GType</link> dest_type,
                                             <link linkend="GValueTransform">GValueTransform</link> transform_func);</programlisting>
<para>

</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>src_type</parameter>&nbsp;:</entry>
<entry>
</entry></row>
<row><entry align="right"><parameter>dest_type</parameter>&nbsp;:</entry>
<entry>
</entry></row>
<row><entry align="right"><parameter>transform_func</parameter>&nbsp;:</entry>
<entry>


</entry></row>
</tbody></tgroup></informaltable></refsect2>
<refsect2>
<title><anchor id="g-strdup-value-contents">g_strdup_value_contents ()</title>
<programlisting><link linkend="gchar">gchar</link>*      g_strdup_value_contents         (const <link linkend="GValue">GValue</link> *value);</programlisting>
<para>
Return a newly allocated string, which describes the contents of a <link linkend="GValue">GValue</link>.
The main purpose of this function is to describe <link linkend="GValue">GValue</link> contents for debugging
output, the way in which the contents are described may change between different
GLib versions.
</para><informaltable pgwide="1" frame="none" role="params">
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<row><entry align="right"><parameter>value</parameter>&nbsp;:</entry>
<entry>  <link linkend="GValue">GValue</link> which contents are to be described.
</entry></row>
<row><entry align="right"><emphasis>Returns</emphasis> :</entry><entry>Newly allocated string.


</entry></row>
</tbody></tgroup></informaltable></refsect2>

</refsect1>



<refsect1>
<title>See Also</title>
<para>
The fundamental types which all support <link linkend="GValue">GValue</link> operations and thus
can be used as a type initializer for <link linkend="g-value-init">g_value_init</link>() are defined by
a separate interface.  See the Standard Values API for details.
</para>
</refsect1>

</refentry>