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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glBufferSubData">
    <info>
        <copyright>
            <year>2005</year>
            <holder>Sams Publishing</holder>
        </copyright>
        <copyright>
            <year>2010-2014</year>
            <holder>Khronos Group</holder>
        </copyright>
    </info>
    <refmeta>
        <refentrytitle>glBufferSubData</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glBufferSubData</refname>
        <refpurpose>updates a subset of a buffer object's data store</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glBufferSubData</function></funcdef>
                <paramdef>GLenum <parameter>target</parameter></paramdef>
                <paramdef>GLintptr <parameter>offset</parameter></paramdef>
                <paramdef>GLsizeiptr <parameter>size</parameter></paramdef>
                <paramdef>const GLvoid * <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>offset</parameter></term>
            <listitem>
                <para>
                    Specifies the offset into the buffer object's data store where data replacement will begin,
                    measured in bytes.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>size</parameter></term>
            <listitem>
                <para>
                    Specifies the size in bytes of the data store region being replaced.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>data</parameter></term>
            <listitem>
                <para>
                    Specifies a pointer to the new data that will be copied into the data store.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="description"><title>Description</title>
        <para>
            <function>glBufferSubData</function> redefines some or all of the data store for the buffer object currently
            bound to <parameter>target</parameter>. Data starting at byte offset <parameter>offset</parameter> and
            extending for <parameter>size</parameter> bytes is copied to the data store from the memory pointed to by
            <parameter>data</parameter>.  An error is thrown if <parameter>offset</parameter> and <parameter>size</parameter>
            together define a range beyond the bounds of the buffer object's data store.
        </para>
    </refsect1>
    <refsect1 xml:id="notes"><title>Notes</title>
        <para>
            When replacing the entire data store, consider using <function>glBufferSubData</function> rather
            than completely recreating the data store with <function>glBufferData</function>.  This avoids the cost of
            reallocating the data store.
        </para>
        <para>
            Consider using multiple buffer objects to avoid stalling the rendering pipeline during data store updates.
            If any rendering in the pipeline makes reference to data in the buffer object being updated by
            <function>glBufferSubData</function>, especially from the specific region being updated, that rendering must
            drain from the pipeline before the data store can be updated.
        </para>
        <para>
            Clients must align data elements consistently with the requirements of the client
            platform, with an additional base-level requirement that an offset within a buffer to
            a datum comprising <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">N</mml:mi></mml:math></inlineequation> bytes be a
            multiple of <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">N</mml:mi></mml:math></inlineequation>.
        </para>
    </refsect1>
    <refsect1 xml:id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not
            one of the accepted buffer targets.
        </para>
        <para>
            <constant>GL_INVALID_VALUE</constant> is generated if <parameter>offset</parameter> or
            <parameter>size</parameter> is negative, or if together they define a region of memory
            that extends beyond the buffer object's allocated data store.
        </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_OPERATION</constant> is generated if the buffer object being updated is mapped.
        </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>glBufferSubData</entry>
                        <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='es20']/*)"/>
                    </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>
