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NAME
glMapBuffer, glMapNamedBuffer - map all of a buffer object's data store into the client's
address space
C SPECIFICATION
void *glMapBuffer(GLenum target, GLenum access);
void *glMapNamedBuffer(GLuint buffer, GLenum access);
PARAMETERS
target
Specifies the target to which the buffer object is bound for glMapBuffer, which must
be one of the buffer binding targets in the following table:
┌─────────────────────────────┬────────────────────────────────┐
│Buffer Binding Target │ Purpose │
├─────────────────────────────┼────────────────────────────────┤
│GL_ARRAY_BUFFER │ Vertex attributes │
├─────────────────────────────┼────────────────────────────────┤
│GL_ATOMIC_COUNTER_BUFFER │ Atomic counter storage │
├─────────────────────────────┼────────────────────────────────┤
│GL_COPY_READ_BUFFER │ Buffer copy source │
├─────────────────────────────┼────────────────────────────────┤
│GL_COPY_WRITE_BUFFER │ Buffer copy destination │
├─────────────────────────────┼────────────────────────────────┤
│GL_DISPATCH_INDIRECT_BUFFER │ Indirect compute dispatch │
│ │ commands │
├─────────────────────────────┼────────────────────────────────┤
│GL_DRAW_INDIRECT_BUFFER │ Indirect command arguments │
├─────────────────────────────┼────────────────────────────────┤
│GL_ELEMENT_ARRAY_BUFFER │ Vertex array indices │
├─────────────────────────────┼────────────────────────────────┤
│GL_PIXEL_PACK_BUFFER │ Pixel read target │
├─────────────────────────────┼────────────────────────────────┤
│GL_PIXEL_UNPACK_BUFFER │ Texture data source │
├─────────────────────────────┼────────────────────────────────┤
│GL_QUERY_BUFFER │ Query result buffer │
├─────────────────────────────┼────────────────────────────────┤
│GL_SHADER_STORAGE_BUFFER │ Read-write storage for shaders │
├─────────────────────────────┼────────────────────────────────┤
│GL_TEXTURE_BUFFER │ Texture data buffer │
├─────────────────────────────┼────────────────────────────────┤
│GL_TRANSFORM_FEEDBACK_BUFFER │ Transform feedback buffer │
├─────────────────────────────┼────────────────────────────────┤
│GL_UNIFORM_BUFFER │ Uniform block storage │
└─────────────────────────────┴────────────────────────────────┘
buffer
Specifies the name of the buffer object for glMapNamedBuffer.
access
Specifies the access policy for glMapBuffer and glMapNamedBuffer, indicating whether
it will be possible to read from, write to, or both read from and write to the buffer
object's mapped data store. The symbolic constant must be GL_READ_ONLY, GL_WRITE_ONLY,
or GL_READ_WRITE.
DESCRIPTION
glMapBuffer and glMapNamedBuffer map the entire data store of a specified buffer object
into the client's address space. The data can then be directly read and/or written
relative to the returned pointer, depending on the specified access policy.
A pointer to the beginning of the mapped range is returned once all pending operations on
that buffer object have completed, and may be used to modify and/or query the
corresponding range of the data store according to the value of access:
• GL_READ_ONLY indicates that the returned pointer may be used to read buffer object
data.
• GL_WRITE_ONLY indicates that the returned pointer may be used to modify buffer object
data.
• GL_READ_WRITE indicates that the returned pointer may be used to read and to modify
buffer object data.
If an error is generated, a NULL pointer is returned.
If no error occurs, the returned pointer will reflect an allocation aligned to the value
of GL_MIN_MAP_BUFFER_ALIGNMENT basic machine units.
The returned pointer values may not be passed as parameter values to GL commands. For
example, they may not be used to specify array pointers, or to specify or query pixel or
texture image data; such actions produce undefined results, although implementations may
not check for such behavior for performance reasons.
No GL error is generated if the returned pointer is accessed in a way inconsistent with
access (e.g. used to read from a mapping made with access GL_WRITE_ONLY or write to a
mapping made with access GL_READ_ONLY), but the result is undefined and system errors
(possibly including program termination) may occur.
Mappings to the data stores of buffer objects may have nonstandard performance
characteristics. For example, such mappings may be marked as uncacheable regions of
memory, and in such cases reading from them may be very slow. To ensure optimal
performance, the client should use the mapping in a fashion consistent with the values of
GL_BUFFER_USAGE for the buffer object and of access. Using a mapping in a fashion
inconsistent with these values is liable to be multiple orders of magnitude slower than
using normal memory.
NOTES
Alignment of the returned pointer is guaranteed only if the version of the GL version is
4.2 or greater. Also, the GL_ATOMIC_COUNTER_BUFFER target is accepted only if the GL
version is 4.2 or greater.
The GL_DISPATCH_INDIRECT_BUFFER and GL_SHADER_STORAGE_BUFFER targets are available only if
the GL version is 4.3 or greater.
The GL_QUERY_BUFFER target is available only if the GL version is 4.4 or greater.
ERRORS
GL_INVALID_ENUM is generated by glMapBuffer if target is not one of the buffer binding
targets listed above.
GL_INVALID_OPERATION is generated by glMapBuffer if zero is bound to target.
GL_INVALID_OPERATION is generated by glMapNamedBuffer if buffer is not the name of an
existing buffer object.
GL_INVALID_ENUM is generated if access is not GL_READ_ONLY, GL_WRITE_ONLY, or
GL_READ_WRITE.
GL_OUT_OF_MEMORY is generated if the GL is unable to map the buffer object's data store.
This may occur for a variety of system-specific reasons, such as the absence of sufficient
remaining virtual memory.
GL_INVALID_OPERATION is generated if the buffer object is in a mapped state.
ASSOCIATED GETS
glGetBufferPointerv() with argument GL_BUFFER_MAP_POINTER
glGetBufferParameter() with argument GL_BUFFER_MAPPED, GL_BUFFER_ACCESS, or
GL_BUFFER_USAGE
glGet() with pname GL_MIN_MAP_BUFFER_ALIGNMENT. The value must be a power of two that is
at least 64.
VERSION SUPPORT
┌─────────────────┬───────────────────────────────────────────────────────────────────────┐
│ │ OpenGL Version │
├─────────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
│Function │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
│/ │ │ │ │ │ │ │ │ │ │ │ │ │
│Feature │ │ │ │ │ │ │ │ │ │ │ │ │
│Name │ │ │ │ │ │ │ │ │ │ │ │ │
├─────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glMapBuffer │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │
├─────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glMapNamedBuffer │ - │ - │ - │ - │ - │ - │ - │ - │ - │ - │ - │ ✔ │
└─────────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘
SEE ALSO
glBindBuffer(), glBindBufferBase(), glBindBufferRange(), glBufferData(),
glBufferSubData(), glDeleteBuffers(), glMapBufferRange(), glUnmapBuffer()
COPYRIGHT
Copyright © 2005 Addison-Wesley. 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. http://opencontent.org/openpub/.
COPYRIGHT
Copyright © 2005 Addison-Wesley Group
Copyright © 2010-2014 Khronos Group
[FIXME: source] 01/03/2018 GLMAPBUFFER(3G)