Ho to use a dynamic array in a MEX file function

Hi I am using a C function in my MATLAB project and one of the inputs is a dynamic array, how can I modify this input since in build.m the inputs are set up and fixed. I want to be able to throw any array size in to it. Following you can find the files I am using:

bimi.c

#include "bimi.h"

extern void bimi(int* poly, int* polysz, int* output){
    int i;
    int a=*(polysz);
    for(i=0;i<a;i++){
        output[i]=2*poly[i];
    }
}

bimi.h

extern void bimi(int* poly, int* polysz, int* output);

bimifunc.m

function y = bimifunc(poly2, polysz2)  %#codegen
         y = coder.nullcopy(zeros(1,5,'int32'));
         coder.updateBuildInfo('addSourceFiles','bimi.c');
         fprintf('Running Custom C Code...\n\n');
         coder.ceval('bimi',coder.ref(poly2),coder.ref(polysz2), coder.ref(y));
end

build.m, this where the input size is setup and fixed, how can I make it dynamic?

function build(target)
    % Entry point function:
    entryPoint = 'bimifunc';%

      %Example input
      poly=zeros(1,5, 'int32');%THIS WHERE I WANT THE DYNAMIC ARRAY OR IS THERE ANOTHER WAY?
      polysz=int32(length(poly));*

      % Configuration object:
      cfg = coder.config(target);

      % Custom source files:
      cfg.CustomSource = 'bimi.c';
      cfg.CustomSourceCode = [ '#include "bimi.h"' ];

      % Generate and Launch Report:
      cfg.GenerateReport = true;
      cfg.LaunchReport = false;

      % Generate Code:
      codegen(entryPoint,'-args', {poly, polysz},'-config', cfg)

end

test.m, I want to be able to generate any random size of array and throw it to the function for calculations.

    %testing the c code embeded to matlab
    poly=ones(1,5, 'int32');
    polysz=int32(length(poly));

    chichi=bimifunc_mex(poly, polysz);

[Jan]

It matters if you create a C-Mex file by your own or use codegen for an automatic generation.

Answer 1

[Ryan Livingston]

Update your code:

function y = bimifunc(poly2, polysz2)  %#codegen
%coder.updateBuildInfo('addSourceFiles','bm.c');
y = coder.nullcopy(zeros(1,polysz2,'int32'));

and the codegen command to use a variable size input:

codegen(entryPoint,'-args', {coder.typeof(poly,[1,Inf]), polysz},'-config', cfg)

That will make the input, poly a 1-by-:Inf array and allocate the output y based on the size of polysz.

Another suggestion would be rather than taking polysz as an argument to your MATLAB function, should it just be:

function y = bimifunc(poly2)  %#codegen
%coder.updateBuildInfo('addSourceFiles','bm.c');
polysz2 = int32(length(polysz2));
y = coder.nullcopy(zeros(1,polysz2,'int32'));

and then:

codegen(entryPoint,'-args', {coder.typeof(poly,[1,Inf])},'-config', cfg)

[antlhem]

do you suggest me to join build.m with bimifunc.m? or how do I initialise poly and polysz to be used in the codegen?. Or just leave the lines of example input? So far the ERROR message I am getting is: _ Undefined function or variable 'poly'._ this error is from build.m

[Ryan Livingston]

build.m and bimifunc.m need to be separate files. I'm just suggesting that you replace the code in bimifunc with the first block I showed and replace your call to codegen in build.m with the second block. Give that a try and see if it works without changing anything else.

[antlhem]

OK. I left the example input line and added the codegen that you suggested additionally I updated y, without joining the files. Thank you!

[Ryan Livingston]

You're welcome!