NAME¶
clEnqueueMapImage - Enqueues a command to map a region of an image
object into the host address space and returns a pointer to this mapped
region.
void *
clEnqueueMapImage(cl_command_queue command_queue,
cl_mem image,
cl_bool blocking_map,
cl_map_flags map_flags,
const size_t * origin,
const size_t * region,
size_t *image_row_pitch,
size_t *image_slice_pitch,
cl_uint num_events_in_wait_list,
const cl_event *event_wait_list,
cl_event *event,
cl_int *errcode_ret);
PARAMETERS¶
command_queue
Must be a valid command-queue.
image
A valid image object. The OpenCL context associated with
command_queue and image must be the same.
blocking_map
Indicates if the map operation is
blocking or
non-blocking.
If blocking_map is CL_TRUE, clEnqueueMapImage
does not return until the specified region in image is mapped into
the host address space and the application can access the contents of the
mapped region using the pointer returned by clEnqueueMapImage.
If blocking_map is CL_FALSE i.e. map operation is
non-blocking, the pointer to the mapped region returned by
clEnqueueMapImage 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 clEnqueueMapImage.
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(3clc) or clEnqueueMapImage is guaranteed
to contain the latest bits in the region being mapped when the
clEnqueueMapBuffer(3clc) or clEnqueueMapImage 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(3clc) or clEnqueueMapImage is guaranteed
to contain the latest bits in the region being mapped when the
clEnqueueMapBuffer(3clc) or clEnqueueMapImage 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(3clc) or
clEnqueueMapImage 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. |
origin
Defines the (x, y, z) offset in pixels in the 1D, 2D or
3D image, the (x, y) offset and the image index in the 2D image array or the
(x) offset and the image index in the 1D image array. If image is a 2D
image object, origin[2] must be 0. If image is a 1D image or 1D
image buffer object, origin[1] and origin[2] must be 0. If
image is a 1D image array object, origin[2] must be 0. If
image is a 1D image array object, origin[1] describes the image
index in the 1D image array. If image is a 2D image array object,
origin[2] describes the image index in the 2D image array.
region
Defines the (width, height, depth) in pixels of the 1D,
2D or 3D rectangle, the (width, height) in pixels of the 2D rectangle and the
number of images of a 2D image array or the (width) in pixels of the 1D
rectangle and the number of images of a 1D image array. If image is a
2D image object, region[2] must be 1. If image is a 1D image or
1D image buffer object, region[1] and region[2] must be 1. If
image is a 1D image array object, region[2] must be 1.
image_row_pitch
Returns the scan-line pitch in bytes for the mapped
region. This must be a non-NULL value.
image_slice_pitch
Returns the size in bytes of each 2D slice of a 3D image
or the size of each 1D or 2D image in a 1D or 2D image array for the mapped
region. For a 1D and 2D image, zero is returned if this argument is not NULL.
For a 3D image, 1D, and 2D image array, image_slice_pitch must be a
non-NULL value.
event_wait_list , num_events_in_wait_list
Specify events that need to complete before
clEnqueueMapImage can be executed. If event_wait_list is NULL,
then clEnqueueMapImage 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.
NOTES¶
The pointer returned maps a 1D, 2D or 3D region starting at
origin and is at least region[0] pixels in size for a 1D
image, 1D image buffer or 1D image array, (image_row_pitch *
region[1]) pixels in size for a 2D image or 2D image array, and
(image_slice_pitch * region[2]) pixels in size for a 3D image.
The result of a memory access outside this region is undefined.
If the image object is created with CL_MEM_USE_HOST_PTR set
in mem_flags, the following will be true:
• The host_ptr specified in
clCreateImage(3clc) is guaranteed to contain the latest bits in the
region being mapped when the clEnqueueMapImage command has
completed.
• The pointer value returned by
clEnqueueMapImage will be derived from the host_ptr specified
when the image object is created.
Mapped image objects are unmapped using
clEnqueueUnmapMemObject(3clc).
clEnqueueMapBuffer(3clc) and clEnqueueMapImage
increment the mapped count of the memory object. The initial mapped count
value of a memory object is zero. Multiple calls to
clEnqueueMapBuffer(3clc) or clEnqueueMapImage on the same
memory object will increment this mapped count by appropriate number of
calls. clEnqueueUnmapMemObject decrements the mapped count of the
memory object.
clEnqueueMapBuffer(3clc) and clEnqueueMapImage act
as synchronization points for a region of the buffer object being
mapped.
ERRORS¶
clEnqueueMapImage 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
(origin, origin+region) is out of bounds or if values
specified in map_flags are not valid.
•CL_INVALID_VALUE if values in origin and
region do not follow rules described in the argument description for
origin and region.
•CL_INVALID_VALUE if image_row_pitch is
NULL.
•CL_INVALID_VALUE if image is a 3D image,
1D or 2D image array object and image_slice_pitch is NULL.
•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_INVALID_IMAGE_SIZE if image dimensions (image
width, height, specified or compute row and/or slice pitch) for image
are not supported by device associated with queue.
•CL_INVALID_IMAGE_FORMAT if image format (image
channel order and data type) for image are not supported by 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 the device associated
with command_queue does not support images (i.e.
CL_DEVICE_IMAGE_SUPPORT specified in the table of OpenCL Device Queries
for clGetDeviceInfo(3clc) is CL_FALSE.
•CL_INVALID_OPERATION if image 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 image has been
created with CL_MEM_HOST_READ_ONLY 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.
SPECIFICATION¶
OpenCL Specification[1]
SEE ALSO¶
clEnqueueMapBuffer(3clc),
clEnqueueUnmapMemObject(3clc)
AUTHORS¶
The Khronos Group
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.
NOTES¶
- 1.
- OpenCL Specification
page 112, section 5.3.5 - Mapping Image Objects
