Ho to use a dynamic array in a MEX file function

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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);
  1 Comment
Jan
Jan on 12 Jul 2018
It matters if you create a C-Mex file by your own or use codegen for an automatic generation.

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Accepted Answer

Ryan Livingston
Ryan Livingston on 16 Jul 2018
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)
  4 Comments
antlhem
antlhem on 17 Jul 2018
Edited: antlhem on 17 Jul 2018
OK. I left the example input line and added the codegen that you suggested additionally I updated y, without joining the files. Thank you!

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