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clEnqueueMapBuffer - Enqueues a command to map a region of the buffer object given by buffer into the
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Copyright
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.
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:
• CL_INVALID_COMMAND_QUEUE if command_queue is not a valid command-queue.
• CL_INVALID_CONTEXT if the context associated with command_queue and image are not the same or if the
context associated with command_queue and events in event_wait_list are not the same.
• CL_INVALID_MEM_OBJECT if image is not a valid image object.
• CL_INVALID_VALUE if region being mapped given by (offset, size) is out of bounds or if size is 0 or
values specified in map_flags are not valid.
• CL_INVALID_EVENT_WAIT_LIST if event_wait_list is NULL and num_events_in_wait_list > 0, or
event_wait_list is not NULL and num_events_in_wait_list is 0, or if event objects in event_wait_list
are not valid events.
• CL_MISALIGNED_SUB_BUFFER_OFFSET if buffer is a sub-buffer object and offset specified when the
sub-buffer object is created is not aligned to CL_DEVICE_MEM_BASE_ADDR_ALIGN value for device
associated with queue.
• CL_MAP_FAILURE if there is a failure to map the requested region into the host address space. This
error cannot occur for image objects created with CL_MEM_USE_HOST_PTR or CL_MEM_ALLOC_HOST_PTR.
• CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LIST if the map operation is blocking and the execution
status of any of the events in event_wait_list is a negative integer value.
• CL_MEM_OBJECT_ALLOCATION_FAILURE if there is a failure to allocate memory for data store associated
with buffer.
• CL_INVALID_OPERATION if buffer has been created with CL_MEM_HOST_WRITE_ONLY or CL_MEM_HOST_NO_ACCESS
and CL_MAP_READ is set in map_flags or if buffer has been created with CL_MEM_HOST_READ_ONL or
CL_MEM_HOST_NO_ACCESS and CL_MAP_WRITE or CL_MAP_WRITE_INVALIDATE_REGION is set in map_flags.
• CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation
on the device.
• CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL
implementation on the host.
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_queuecommand_queue,cl_membuffer,cl_boolblocking_map,cl_map_flagsmap_flags,size_toffset,size_tsize,cl_uintnum_events_in_wait_list,constcl_event*event_wait_list,cl_event*event,cl_int*errcode_ret);Notes
1. OpenCL Specification
page 86, section 5.2.3 - Mapping Buffer Objects
The Khronos Group 11/18/2024 CLENQUEUEMAPBUFFER(3clc)
Parameters
command_queue
Must be a valid command-queue.
blocking_map
Indicates if the map operation is blocking or non-blocking.
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
A bit-bield with the following supported values.
┌────────────────────────────────┬───────────────────────────────────────┐
│ 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
A valid buffer object. The OpenCL context associated with command_queue and buffer must be the same.
offset,size
The offset in bytes and the size of the region in the buffer object that is being mapped.
event_wait_list,num_events_in_wait_list
Specify events that need to complete before this particular command can be executed. If
event_wait_list is NULL, then this particular command does not wait on any event to complete. If
event_wait_list is NULL, num_events_in_wait_list must be 0. If event_wait_list is not NULL, the list
of events pointed to by event_wait_list must be valid and num_events_in_wait_list must be greater
than 0. The events specified in event_wait_list act as synchronization points. The context associated
with events in event_wait_list and command_queue must be the same. The memory associated with
event_wait_list can be reused or freed after the function returns.
event
Returns an event object that identifies this particular copy command and can be used to query or
queue a wait for this particular command to complete. event can be NULL in which case it will not be
possible for the application to query the status of this command or queue a wait for this command to
complete. If the event_wait_list and the event arguments are not NULL, the event argument should not
refer to an element of the event_wait_list array.
errcode_ret
Returns an appropriate error code. If errcode_ret is NULL, no error code is returned.
See Also
clEnqueueMapImage(3clc), clEnqueueUnmapMemObject(3clc)
Specification
OpenCLSpecification[1]
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