upstream-man-pages/man4/glMapBufferRange.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="glMapBufferRange">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2012</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glMapBufferRange</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glMapBufferRange</refname>
  17         <refpurpose>map a section of a buffer object's data store</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void *<function>glMapBufferRange</function></funcdef>
  23                 <paramdef>GLenum <parameter>target</parameter></paramdef>
  24                 <paramdef>GLintptr <parameter>offset</parameter></paramdef>
  25                 <paramdef>GLsizeiptr <parameter>length</parameter></paramdef>
  26                 <paramdef>GLbitfield <parameter>access</parameter></paramdef>
  27             </funcprototype>
  28         </funcsynopsis>
  29     </refsynopsisdiv>
  30     <refsect1 id="parameters"><title>Parameters</title>
  31         <variablelist>
  32         <varlistentry>
  33             <term><parameter>target</parameter></term>
  34             <listitem>
  35                 <para>
  36                     Specifies a binding to which the target buffer is bound.
  37                 </para>
  38             </listitem>
  39         </varlistentry>
  40         <varlistentry>
  41             <term><parameter>offset</parameter></term>
  42             <listitem>
  43                 <para>
  44                     Specifies a the starting offset within the buffer of the range to be mapped.
  45                 </para>
  46             </listitem>
  47         </varlistentry>
  48         <varlistentry>
  49             <term><parameter>length</parameter></term>
  50             <listitem>
  51                 <para>
  52                     Specifies a length of the range to be mapped.
  53                 </para>
  54             </listitem>
  55         </varlistentry>
  56         <varlistentry>
  57             <term><parameter>access</parameter></term>
  58             <listitem>
  59                 <para>
  60                     Specifies a combination of access flags indicating the desired access to the range.
  61                 </para>
  62             </listitem>
  63         </varlistentry>
  64         </variablelist>
  65     </refsect1>
  66     <refsect1 id="description"><title>Description</title>
  67         <para>
  68             <function>glMapBufferRange</function> maps all or part of the data store of a buffer object into the client's address
  69             space. <parameter>target</parameter> specifies the target to which the buffer is bound and must be one of <constant>GL_ARRAY_BUFFER</constant>,
  70             <constant>GL_ATOMIC_COUNTER_BUFFER</constant>,
  71             <constant>GL_COPY_READ_BUFFER</constant>, <constant>GL_COPY_WRITE_BUFFER</constant>, <constant>GL_DRAW_INDIRECT_BUFFER</constant>,
  72             <constant>GL_DISPATCH_INDIRECT_BUFFER</constant>, <constant>GL_ELEMENT_ARRAY_BUFFER</constant>,
  73             <constant>GL_PIXEL_PACK_BUFFER</constant>, <constant>GL_PIXEL_UNPACK_BUFFER</constant>, <constant>GL_TEXTURE_BUFFER</constant>,
  74             <constant>GL_TRANSFORM_FEEDBACK_BUFFER</constant>, <constant>GL_UNIFORM_BUFFER</constant> or <constant>GL_SHADER_STORAGE_BUFFER</constant>. <parameter>offset</parameter> and
  75             <parameter>length</parameter> indicate the range of data in the buffer object htat is to be mapped, in terms of basic machine units.
  76             <parameter>access</parameter> is a bitfield containing flags which describe the requested mapping. These flags are described below.
  77         </para>
  78         <para>
  79             If no error occurs, a pointer to the beginning of the mapped range is returned once all pending operations on that buffer have
  80             completed, and may be used to modify and/or query the corresponding range of the buffer, according to the following flag bits set
  81             in <parameter>access</parameter>:
  82             <itemizedlist>
  83                 <listitem>
  84                     <para>
  85                         <constant>GL_MAP_READ_BIT</constant> indicates that the returned pointer may be used to read
  86                         buffer object data. No GL error is generated if the pointer is used to query
  87                         a mapping which excludes this flag, but the result is undefined and system
  88                         errors (possibly including program termination) may occur.
  89                     </para>
  90                 </listitem>
  91                 <listitem>
  92                     <para>
  93                         <constant>GL_MAP_WRITE_BIT</constant> indicates that the returned pointer may be used to modify
  94                         buffer object data. No GL error is generated if the pointer is used to modify
  95                         a mapping which excludes this flag, but the result is undefined and system
  96                         errors (possibly including program termination) may occur.
  97                     </para>
  98                 </listitem>
  99             </itemizedlist>
 100         </para>
 101         <para>
 102             Furthermore, the following <emphasis>optional</emphasis> flag bits in <parameter>access</parameter> may be used to modify the mapping:
 103             <itemizedlist>
 104                 <listitem>
 105                     <para>
 106                         <constant>GL_MAP_INVALIDATE_RANGE_BIT</constant> indicates that the previous contents of the
 107                         specified range may be discarded. Data within this range are undefined with
 108                         the exception of subsequently written data. No GL error is generated if sub-
 109                         sequent GL operations access unwritten data, but the result is undefined and
 110                         system errors (possibly including program termination) may occur. This flag
 111                         may not be used in combination with <constant>GL_MAP_READ_BIT</constant>.
 112                     </para>
 113                 </listitem>
 114                 <listitem>
 115                     <para>
 116                         <constant>GL_MAP_INVALIDATE_BUFFER_BIT</constant> indicates that the previous contents of the
 117                         entire buffer may be discarded. Data within the entire buffer are undefined
 118                         with the exception of subsequently written data. No GL error is generated if
 119                         subsequent GL operations access unwritten data, but the result is undefined
 120                         and system errors (possibly including program termination) may occur. This
 121                         flag may not be used in combination with <constant>GL_MAP_READ_BIT</constant>.
 122                     </para>
 123                 </listitem>
 124                 <listitem>
 125                     <para>
 126                         <constant>GL_MAP_FLUSH_EXPLICIT_BIT</constant> indicates that one or more discrete subranges
 127                         of the mapping may be modified.  When this flag is set, modifications to
 128                         each subrange must be explicitly flushed by calling <citerefentry><refentrytitle>glFlushMappedBufferRange</refentrytitle></citerefentry>.
 129                         No GL error is set if a subrange of the mapping is modified and
 130                         not flushed, but data within the corresponding subrange of the buffer are undefined.
 131                         This flag may only be used in conjunction with <constant>GL_MAP_WRITE_BIT</constant>.
 132                         When this option is selected, flushing is strictly limited to regions that are
 133                         explicitly indicated with calls to <citerefentry><refentrytitle>glFlushMappedBufferRange</refentrytitle></citerefentry>
 134                         prior to unmap; if this option is not selected <citerefentry><refentrytitle>glUnmapBuffer</refentrytitle></citerefentry>
 135                         will automatically flush the entire mapped range when called.
 136                     </para>
 137                 </listitem>
 138                 <listitem>
 139                     <para>
 140                         <constant>GL_MAP_UNSYNCHRONIZED_BIT</constant> indicates that the GL should not attempt to
 141                         synchronize pending operations on the buffer prior to returning from <function>glMapBufferRange</function>.
 142                         No GL error is generated if pending operations which source or modify the buffer overlap the mapped region,
 143                         but the result of such previous and any subsequent operations is undefined.
 144                     </para>
 145                 </listitem>
 146             </itemizedlist>
 147         </para>
 148         <para>
 149             If an error occurs, <function>glMapBufferRange</function> returns a <code>NULL</code> pointer.
 150             If no error occurs, the returned pointer will reflect an alignment of at least <constant>GL_MIN_MAP_BUFFER_ALIGNMENT</constant>
 151             basic machine units. The value of <constant>GL_MIN_MAP_BUFFER_ALIGNMENT</constant> can be retrieved by calling
 152             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with <parameter>pname</parameter> set to
 153             <constant>GL_MIN_MAP_BUFFER_ALIGNMENT</constant> and must be a power of two that is at least 64. Subtracting <parameter>offset</parameter>
 154             from this returned pointed will always produce a multiple of <constant>GL_MIN_MAP_BUFFER_ALINMENT</constant>.
 155         </para>
 156     </refsect1>
 157     <refsect1 id="notes"><title>Notes</title>
 158         <para>
 159             Alignment of the returned pointer is guaranteed only if the version
 160             of the GL version is 4.2 or greater. Also, the <constant>GL_ATOMIC_COUNTER_BUFFER</constant>
 161             target is accepted only if the GL version is 4.2 or greater.
 162         </para>
 163         <para>
 164             The <constant>GL_DISPATCH_INDIRECT_BUFFER</constant> and <constant>GL_SHADER_STORAGE_BUFFER</constant> targets are accepted only if the
 165             GL version is 4.3 or greater.
 166         </para>
 167     </refsect1>
 168     <refsect1 id="errors"><title>Errors</title>
 169         <para>
 170             <constant>GL_INVALID_VALUE</constant> is generated if either of <parameter>offset</parameter> or <parameter>length</parameter> is negative,
 171             or if <parameter>offset</parameter> + <parameter>length</parameter> is greater than the value of <constant>GL_BUFFER_SIZE</constant>.
 172         </para>
 173         <para>
 174             <constant>GL_INVALID_VALUE</constant> is generated if <parameter>access</parameter> has any bits set other than those defined above.
 175         </para>
 176         <para>
 177             <constant>GL_INVALID_OPERATION</constant> is generated for any of the following conditions:
 178             <itemizedlist>
 179                 <listitem>
 180                     <para>
 181                         The buffer is already in a mapped state.
 182                     </para>
 183                 </listitem>
 184                 <listitem>
 185                     <para>
 186                         Neither <constant>GL_MAP_READ_BIT</constant> or <constant>GL_MAP_WRITE_BIT</constant> is set.
 187                     </para>
 188                 </listitem>
 189                 <listitem>
 190                     <para>
 191                         <constant>GL_MAP_READ_BIT</constant> is set and any of <constant>GL_MAP_INVALIDATE_RANGE_BIT</constant>,
 192                         <constant>GL_MAP_INVALIDATE_BUFFER_BIT</constant>, or <constant>GL_MAP_UNSYNCHRONIZED_BIT</constant> is set.
 193                     </para>
 194                 </listitem>
 195                 <listitem>
 196                     <para>
 197                         <constant>GL_MAP_FLUSH_EXPLICIT_BIT</constant> is set and <constant>GL_MAP_WRITE_BIT</constant> is not set.
 198                     </para>
 199                 </listitem>
 200             </itemizedlist>
 201         </para>
 202         <para>
 203             <constant>GL_OUT_OF_MEMORY</constant> is generated if <function>glMapBufferRange</function> fails because memory for the
 204             mapping could not be obtained.
 205         </para>
 206     </refsect1>
 207     <refsect1 id="seealso"><title>See Also</title>
 208         <para>
 209             <citerefentry><refentrytitle>glMapBuffer</refentrytitle></citerefentry>,
 210             <citerefentry><refentrytitle>glFlushMappedBufferRange</refentrytitle></citerefentry>,
 211             <citerefentry><refentrytitle>glBindBuffer</refentrytitle></citerefentry>
 212         </para>
 213     </refsect1>
 214     <refsect1 id="Copyright"><title>Copyright</title>
 215         <para>
 216             Copyright <trademark class="copyright"></trademark> 2010-2012 Khronos Group.
 217             This material may be distributed subject to the terms and conditions set forth in
 218             the Open Publication License, v 1.0, 8 June 1999.
 219             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 220         </para>
 221     </refsect1>
 222 </refentry>