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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)