cl_int clEnqueueReadBufferRect(cl_command_queue command_queue, cl_mem buffer, cl_bool blocking_read, const size_t * buffer_origin, const size_t * host_origin, const size_t * region, size_t buffer_row_pitch, size_t buffer_slice_pitch, size_t host_row_pitch, size_t host_slice_pitch, void *ptr, cl_uint num_events_in_wait_list, const cl_event *event_wait_list, cl_event *event);

PARAMETERS

command_queue

Refers to the command-queue in which the read command will be queued. command_queue and buffer must be created with the same OpenCL context.

buffer

Refers to a valid buffer object.

blocking_read

Indicates if the read operations are blocking or non-blocking.

If blocking_read is CL_TRUE i.e. the read command is blocking, clEnqueueReadBufferRect does not return until the buffer data has been read and copied into memory pointed to by ptr.

If blocking_read is CL_FALSE i.e. the read command is non-blocking, clEnqueueReadBufferRect queues a non-blocking read command and returns. The contents of the buffer that ptr points to cannot be used until the read command has completed. The event argument argument returns an event object which can be used to query the execution status of the read command. When the read command has completed, the contents of the buffer that ptr points to can be used by the application.

buffer_origin

The (x, y, z) offset in the memory region associated with buffer. For a 2D rectangle region, the z value given by buffer_origin[2] should be 0. The offset in bytes is computed as buffer_origin[2] * buffer_slice_pitch + buffer_origin[1] * buffer_row_pitch + buffer_origin[0].

host_origin

The (x, y, z) offset in the memory region pointed to by ptr. For a 2D rectangle region, the z value given by host_origin[2] should be 0. The offset in bytes is computed as host_origin[2] * host_slice_pitch + host_origin[1] * host_row_pitch + host_origin[0].

region

The (width, height, depth) in bytes of the 2D or 3D rectangle being read or written. For a 2D rectangle copy, the depth value given by region[2] should be 1.

buffer_row_pitch

The length of each row in bytes to be used for the memory region associated with buffer. If buffer_row_pitch is 0, buffer_row_pitch is computed as region[0].

buffer_slice_pitch

The length of each 2D slice in bytes to be used for the memory region associated with buffer. If buffer_slice_pitch is 0, buffer_slice_pitch is computed as region[1] * buffer_row_pitch.

host_row_pitch

The length of each row in bytes to be used for the memory region pointed to by ptr. If host_row_pitch is 0, host_row_pitch is computed as region[0].

host_slice_pitch

The length of each 2D slice in bytes to be used for the memory region pointed to by ptr. If host_slice_pitch is 0, host_slice_pitch is computed as region[1] * host_row_pitch.

ptr

The pointer to buffer in host memory where data is to be read into.

event_wait_list , num_events_in_wait_list

event_wait_list and 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 read 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.

NOTES

Calling clEnqueueReadBufferRect to read a region of the buffer object with the ptr argument value set to host_ptr and host_origin, buffer_origin values are the same, where host_ptr is a pointer to the memory region specified when the buffer object being read is created with CL_MEM_USE_HOST_PTR, must meet the same requirements given for clEnqueueReadBuffer(3clc).

Calling clEnqueueWriteBufferRect to update the latest bits in a region of the buffer object with the ptr argument value set to host_ptr and host_origin, buffer_origin values are the same, where host_ptr is a pointer to the memory region specified when the buffer object being written is created with CL_MEM_USE_HOST_PTR, must meet the following requirements in order to avoid undefined behavior:

•

The host memory region given by (buffer_originregion) contains the latest bits when the enqueued write command begins execution.

•

The buffer object or memory objects created from this buffer object are not mapped.

•

The buffer object or memory objects created from this buffer object are not used by any command-queue until the write command has finished execution.

SPECIFICATION

m[blue]OpenCL Specificationm[][1]

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 74, section 5.2.2 - Reading, Writing and Copying Buffer Objects