Strided copy between HOST and DEVICE clEnqueueWriteBufferRect - copy

Question

I search for a means to transfer data from two HOST buffers into a single DEVICE buffer in the following strided way:
Below are the two host buffers
Host_buffer_1 = [0 5] // copy to device with a stride equals to 5
Host_buffer_2 = [1 2 3 4 6 7 8 9] // each region of 4 numbers copy with a stride
I need the resulting Device buffer to be
device buffer [0 1 2 3 4 5 6 7 8 9]
Do I have to realize it on the HOST first and then a normal transfer to the device, or do you know a means to achieve this using clEnqueueWriteBufferRect function for instance, but this function does not have any stride parameter, right?
Thanks

Answer 1

You can use cl calls to do the rectangular patch copy on the fly. However, performance wise, I am not sure if this is the right approach.
If you shape your data as a 2D:
0 1 2 3 4
5 6 7 8 9
Then the buffers map like:
Device Host1 Host2
1 2 2 2 2 1 2 2 2 2
1 2 2 2 2 1 2 2 2 2
Therefore the copy rect commands should be:
clEnqueueWriteBufferRect(queue, buffer, CL_FALSE,
{0,0,0}, //buffer_origin
{0,0,0}, //host_origin
{1,2,1}, //region
5*sizeof(type), //buffer_row_pitch
0, //buffer_slice_pitch
1*sizeof(type), //host_row_pitch
0, //host_slice_pitch
host1, 0, NULL, NULL);
clEnqueueWriteBufferRect(queue, buffer, CL_FALSE,
{1,0,0}, //buffer_origin
{0,0,0}, //host_origin
{4,2,1}, //region
5*sizeof(type), //buffer_row_pitch
0, //buffer_slice_pitch
4*sizeof(type), //host_row_pitch
0, //host_slice_pitch
host2, 0, NULL, NULL);
But be VERY careful with the row_pitch and slice_pitch, as well as the offsets and regions. Since it is quite easy to get messed up. (And please check my code if you use it)
clEnqueueWriteBufferRect