Suppose your MEX-file myFunction
has two
input arguments and one output argument. The MATLAB^{®} syntax is [X]
= myFunction(Y, Z)
. To call myFunction
from MATLAB,
type:
X = myFunction(Y, Z);
The MATLAB interpreter calls mexFunction
,
the gateway routine to myFunction
, with the following
arguments:
Your input is prhs
, a two-element array (nrhs
= 2
). The first element is a pointer to an mxArray
named Y
and
the second element is a pointer to an mxArray
named Z
.
Your output is plhs
, a one-element array
(nlhs = 1
) where the single element is a null
pointer.
The parameter plhs
points at nothing because the
output X
is not created until the subroutine executes.
The gateway routine creates the output array and sets a pointer
to it in plhs[0]
. If the routine does not assign
a value to plhs[0]
but you assign an output value
to the function when you call it, MATLAB generates an error.
Note:
It is possible to return an output value even if |
The following MEX Cycle diagram shows how inputs enter a MEX-file, what functions the gateway routine performs, and how outputs return to MATLAB.
In this example, the syntax of the MEX-file func
is [C,
D] = func(A,B)
. In the figure, a call to func
tells MATLAB to
pass variables A
and B
to your
MEX-file. C
and D
are left unassigned.
The gateway routine, func.c
, uses the mxCreate*
functions
to create the MATLAB arrays for your output arguments. It sets plhs[0]
and plhs[1]
to
the pointers to the newly created MATLAB arrays. It uses the mxGet*
functions
to extract your data from your input arguments prhs[0]
and prhs[1]
.
Finally, it calls your computational routine, passing the input and
output data pointers as function parameters.
MATLAB assigns plhs[0]
to C
and plhs[1]
to D
.
C/C++ MEX Cycle