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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glGetBufferParameter">
    <info>
        <copyright>
            <year>2005</year>
            <holder>Sams Publishing</holder>
        </copyright>
        <copyright>
            <year>2010-2014</year>
            <holder>Khronos Group</holder>
        </copyright>
    </info>
    <refmeta>
        <refentrytitle>glGetBufferParameter</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glGetBufferParameter</refname>
        <refpurpose>return parameters of a buffer object</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glGetBufferParameteriv</function></funcdef>
                <paramdef>GLenum <parameter>target</parameter></paramdef>
                <paramdef>GLenum <parameter>value</parameter></paramdef>
                <paramdef>GLint * <parameter>data</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glGetBufferParameteri64v</function></funcdef>
                <paramdef>GLenum <parameter>target</parameter></paramdef>
                <paramdef>GLenum <parameter>value</parameter></paramdef>
                <paramdef>GLint64 * <parameter>data</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 xml:id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>target</parameter></term>
            <listitem>
                <para>
                    Specifies the target buffer object.
                    The symbolic constant must be <constant>GL_ARRAY_BUFFER</constant>,
                    <constant>GL_COPY_READ_BUFFER</constant>,
                    <constant>GL_COPY_WRITE_BUFFER</constant>,
                    <constant>GL_ELEMENT_ARRAY_BUFFER</constant>,
                    <constant>GL_PIXEL_PACK_BUFFER</constant>,
                    <constant>GL_PIXEL_UNPACK_BUFFER</constant>,
                    <constant>GL_TRANSFORM_FEEDBACK_BUFFER</constant>, or
                    <constant>GL_UNIFORM_BUFFER</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>value</parameter></term>
            <listitem>
                <para>
                    Specifies the symbolic name of a buffer object parameter.
                    Accepted values are <constant>GL_BUFFER_ACCESS_FLAGS</constant>, <constant>GL_BUFFER_MAPPED</constant>,
                    <constant>GL_BUFFER_MAP_LENGTH</constant>, <constant>GL_BUFFER_MAP_OFFSET</constant>,
                                        <constant>GL_BUFFER_SIZE</constant>, or <constant>GL_BUFFER_USAGE</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>data</parameter></term>
            <listitem>
                <para>
                    Returns the requested parameter.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="description"><title>Description</title>
        <para>
            <function>glGetBufferParameteriv</function> and <function>glGetBufferParameteri64v</function>
                        return in <parameter>data</parameter> a selected parameter of the buffer object
            specified by <parameter>target</parameter>.
        </para>
        <para>
            <parameter>value</parameter> names a specific buffer object parameter, as follows:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_BUFFER_ACCESS_FLAGS</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns the access policy set while mapping the buffer object.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_BUFFER_MAPPED</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns a flag indicating whether the buffer object is currently
                        mapped. The initial value is <constant>GL_FALSE</constant>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_BUFFER_MAP_LENGTH</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns the length of the buffer object mapping,
                                                measured in bytes.
                                                The initial value is 0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_BUFFER_MAP_OFFSET</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns the offset (start) of the buffer object mapping,
                                                measured in bytes.
                                                The initial value is 0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_BUFFER_SIZE</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns the size of the buffer object, measured in bytes.
                        The initial value is 0.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_BUFFER_USAGE</constant></term>
                <listitem>
                    <para>
                        <parameter>params</parameter> returns the buffer object's usage pattern.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="notes"><title>Notes</title>
        <para>
            If an error is generated,
            no change is made to the contents of <parameter>data</parameter>.
        </para>
        <para>
            If <function>glGetBufferParameteriv</function> is used to query a <parameter>value</parameter> of
                        <constant>GL_BUFFER_SIZE</constant>, values greater than or equal to
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                                <!-- eqn: 2 sup 31: -->
                                <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mfenced open="" close="">
                                                <mml:msub><mml:mi mathvariant="italic">31</mml:mi></mml:msub>
                                        </mml:mfenced>
                                        </mml:msup>
                                </mml:mrow>
                        </mml:math></inlineequation>
                        will be clamped to
                        <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                                <!-- eqn: 2 sup 31 - 1: -->
                                <mml:mrow>
                                        <mml:msup><mml:mn>2</mml:mn>
                                        <mml:mfenced open="" close="">
                                                <mml:msub><mml:mi mathvariant="italic">31</mml:mi></mml:msub>
                                        </mml:mfenced>
                                        </mml:msup>
                                        <mml:mo>-</mml:mo>
                                        <mml:mn>1</mml:mn>
                                </mml:mrow>
                        </mml:math></inlineequation>.
        </para>
    </refsect1>
    <refsect1 xml:id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> or <parameter>value</parameter> is not an
            accepted value.
        </para>
        <para>
            <constant>GL_INVALID_OPERATION</constant> is generated if the reserved buffer object name 0 is bound to <parameter>target</parameter>.
        </para>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <function>glGetBufferParameteri64v</function> is used to query a <parameter>value</parameter> of
            <constant>GL_BUFFER_ACCESS_FLAGS</constant>, <constant>GL_BUFFER_MAPPED</constant> or <constant>GL_BUFFER_USAGE</constant>.
        </para>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <function>glGetBufferParameteriv</function> is used to query a <parameter>value</parameter> of
            <constant>GL_BUFFER_MAP_LENGTH</constant> or <constant>GL_BUFFER_MAP_OFFSET</constant>.
        </para>
    </refsect1>
    <refsect1 xml:id="versions">
        <title>API Version Support</title>
        <informaltable>
            <tgroup cols="3" align="left">
                <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apifunchead.xml" xpointer="xpointer(/*/*)"/>
                <tbody>
                    <row>
                        <entry><function>glGetBufferParameteriv</function></entry>
                        <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='es20']/*)"/>
                    </row>
                    <row>
                        <entry><function>glGetBufferParameteri64v</function></entry>
                        <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='es30']/*)"/>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect1>
    <refsect1 xml:id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glBufferData</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glMapBufferRange</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glUnmapBuffer</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 xml:id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"/> 2005 Addison-Wesley.
            Copyright <trademark class="copyright"/> 2010-2014 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://opencontent.org/openpub/">http://opencontent.org/openpub/</link>.
        </para>
    </refsect1>
</refentry>
