table of contents
CLENQUEUEMAPBUFFER(3clc) | OpenCL Manual | CLENQUEUEMAPBUFFER(3clc) |
NAME¶
clEnqueueMapBuffer - Enqueues a command to map a region of the buffer object given by buffer into the host address space and returns a pointer to this mapped region.¶
void * clEnqueueMapBuffer(cl_command_queue command_queue, cl_mem buffer, cl_bool blocking_map, cl_map_flags map_flags, size_t offset, size_t size, cl_uint num_events_in_wait_list, const cl_event *event_wait_list, cl_event *event, cl_int *errcode_ret);
PARAMETERS¶
command_queueblocking_map
If blocking_map is CL_TRUE, clEnqueueMapBuffer does not return until the specified region in buffer is mapped into the host address space and the application can access the contents of the mapped region using the pointer returned by clEnqueueMapBuffer.
If blocking_map is CL_FALSE i.e. map operation is non-blocking, the pointer to the mapped region returned by clEnqueueMapBuffer cannot be used until the map command has completed. The event argument returns an event object which can be used to query the execution status of the map command. When the map command is completed, the application can access the contents of the mapped region using the pointer returned by clEnqueueMapBuffer.
map_flags
cl_map_flags | Description |
CL_MAP_READ | This flag specifies that the region being mapped in the memory object is being mapped for reading. The pointer returned by clEnqueueMapBuffer or clEnqueueMapImage(3clc) is guaranteed to contain the latest bits in the region being mapped when the clEnqueueMapBuffer or clEnqueueMapImage(3clc) command has completed. |
CL_MAP_WRITE | This flag specifies that the region being mapped in the memory object is being mapped for writing. The pointer returned by clEnqueueMapBuffer or clEnqueueMapImage(3clc) is guaranteed to contain the latest bits in the region being mapped when the clEnqueueMapBuffer or clEnqueueMapImage(3clc) command has completed. |
CL_MAP_WRITE_INVALIDATE_REGION | This flag specifies that the region being mapped in the memory object is being mapped for writing. The contents of the region being mapped are to be discarded. This is typically the case when the region being mapped is overwritten by the host. This flag allows the implementation to no longer guarantee that the pointer returned by clEnqueueMapBuffer or clEnqueueMapImage(3clc) contains the latest bits in the region being mapped which can be a significant performance enhancement. CL_MAP_READ or CL_MAP_WRITE and CL_MAP_WRITE_INVALIDATE_REGION are mutually exclusive. |
buffer
offset, size
event_wait_list, num_events_in_wait_list
event
errcode_ret
NOTES¶
The returned pointer maps a region starting at offset and is at least size bytes in size. The result of a memory access outside this region is undefined.If the buffer object is created with CL_MEM_USE_HOST_PTR set in mem_flags, the following will be true:
Mapped buffer objects are unmapped using clEnqueueUnmapMemObject(3clc).
clEnqueueMapBuffer and clEnqueueMapImage(3clc) increment the mapped count of the memory object. The initial mapped count value of a memory object is zero. Multiple calls to clEnqueueMapBuffer or clEnqueueMapImage(3clc) on the same memory object will increment this mapped count by appropriate number of calls. clEnqueueUnmapMemObject(3clc) decrements the mapped count of the memory object.
clEnqueueMapBuffer and clEnqueueMapImage(3clc) act as synchronization points for a region of the buffer object being mapped.
ERRORS¶
clEnqueueMapBuffer will return a pointer to the mapped region if the function is executed successfully. The errcode_ret is set to CL_SUCCESS.A NULL pointer is returned otherwise with one of the following error values returned in errcode_ret:
SPECIFICATION¶
OpenCL Specification[1]SEE ALSO¶
clEnqueueMapImage(3clc), clEnqueueUnmapMemObject(3clc)AUTHORS¶
The Khronos GroupCOPYRIGHT¶
Copyright © 2007-2011 The Khronos Group Inc.Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.
NOTES¶
- 1.
- OpenCL Specification
06/18/2014 | The Khronos Group |