Enqueue commands to read from a buffer object to host memory.
cl_int clEnqueueReadBuffer(cl_command_queue command_queue, cl_mem buffer, cl_bool blocking_read, size_t offset, size_t size, void *ptr, cl_uint num_events_in_wait_list, const cl_event *event_wait_list, cl_event *event)
Is a valid host command-queue in which the read command will be queued.
buffermust be created with the same OpenCL context.
Refers to a valid buffer object.
Indicates if the read operations are
CL_TRUEi.e. the read command is blocking,
clEnqueueReadBufferdoes not return until the buffer data has been read and copied into memory pointed to by
CL_FALSEi.e. the read command is
non-blockingread command and returns. The contents of the buffer that
ptrpoints to cannot be used until the read command has completed. The
eventargument 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
ptrpoints to can be used by the application.
The offset in bytes in the buffer object to read from.
The size in bytes of data being read.
The pointer to buffer in host memory where data is to be read into.
num_events_in_wait_listspecify events that need to complete before this particular command can be executed. If
event_wait_listis NULL, then this particular command does not wait on any event to complete. If
num_events_in_wait_listmust be 0. If
event_wait_listis not NULL, the list of events pointed to by
event_wait_listmust be valid and
num_events_in_wait_listmust be greater than 0. The events specified in
event_wait_listact as synchronization points. The context associated with events in
command_queuemust be the same. The memory associated with
event_wait_listcan be reused or freed after the function returns.
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.
eventcan 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
eventarguments are not NULL, the
eventargument should not refer to an element of the
clEnqueueReadBuffer to read a region of the buffer object with the
ptr argument value set to
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 following requirements in order to avoid undefined behavior:
All commands that use this buffer object or a memory object (buffer or image) created from this buffer object have finished execution before the read 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 read command has finished execution.
CL_SUCCESS if the function is executed successfully.
Otherwise, it returns one of the following errors:
command_queueis not a valid host command-queue.
CL_INVALID_CONTEXTif the context associated with
bufferare not the same or if the context associated with
command_queueand events in
event_wait_listare not the same.
bufferis not a valid buffer object.
CL_INVALID_VALUEif the region being read specified by (
size) is out of bounds or if
ptris a NULL value.
event_wait_listis NULL and
num_events_in_wait_list> 0, or
event_wait_listis not NULL and
num_events_in_wait_listis 0, or if event objects in
event_wait_listare not valid events.
bufferis a sub-buffer object and
offsetspecified when the sub-buffer object is created is not aligned to
CL_DEVICE_MEM_BASE_ADDR_ALIGNvalue for device associated with
CL_EXEC_STATUS_ERROR_FOR_EVENTS_IN_WAIT_LISTif the read and write operations are blocking and the execution status of any of the events in
event_wait_listis a negative integer value.
CL_MEM_OBJECT_ALLOCATION_FAILUREif there is a failure to allocate memory for data store associated with
clEnqueueReadBufferis called on
bufferwhich has been created with
CL_OUT_OF_RESOURCESif there is a failure to allocate resources required by the OpenCL implementation on the device.
CL_OUT_OF_HOST_MEMORYif there is a failure to allocate resources required by the OpenCL implementation on the host.