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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glGetBufferSubData">
<refmeta>
<refmetainfo>
<copyright>
<year>2005</year>
<holder>Sams Publishing</holder>
</copyright>
</refmetainfo>
<refentrytitle>glGetBufferSubData</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glGetBufferSubData</refname>
<refpurpose>returns a subset of a buffer object's data store</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glGetBufferSubData</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLintptr <parameter>offset</parameter></paramdef>
<paramdef>GLsizeiptr <parameter>size</parameter></paramdef>
<paramdef>GLvoid * <parameter>data</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 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_ELEMENT_ARRAY_BUFFER</constant>,
<constant>GL_PIXEL_PACK_BUFFER</constant>, or
<constant>GL_PIXEL_UNPACK_BUFFER</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>offset</parameter></term>
<listitem>
<para>
Specifies the offset into the buffer object's data store from which data will be returned,
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 returned.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>data</parameter></term>
<listitem>
<para>
Specifies a pointer to the location where buffer object data is returned.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glGetBufferSubData</function> returns some or all of the data from 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 from the data store to the memory pointed to by
<parameter>data</parameter>. An error is thrown if the buffer object is currently mapped, or 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 id="notes"><title>Notes</title>
<para>
If an error is generated,
no change is made to the contents of <parameter>data</parameter>.
</para>
<para>
<function>glGetBufferSubData</function> is available only if the GL version is 1.5 or greater.
</para>
<para>
Targets <constant>GL_PIXEL_PACK_BUFFER</constant> and <constant>GL_PIXEL_UNPACK_BUFFER</constant> are available
only if the GL version is 2.1 or greater.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> is not
<constant>GL_ARRAY_BUFFER</constant>, <constant>GL_ELEMENT_ARRAY_BUFFER</constant>,
<constant>GL_PIXEL_PACK_BUFFER</constant>, or <constant>GL_PIXEL_UNPACK_BUFFER</constant>.
</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 queried is mapped.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glGetBufferSubData</function>
is executed between the execution of
<citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> and the corresponding execution of
<citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glBufferData</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glBufferSubData</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glMapBuffer</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glUnmapBuffer</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 2005 Addison-Wesley.
This material may be distributed subject to the terms and conditions set forth in
the Open Publication License, v 1.0, 8 June 1999.
<ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
</para>
</refsect1>
</refentry>