Need suggestion on Code conversion to Matlab_extension 1 - c

Question

This is an extension of the previously asked question: link. In a short, I am trying to convert a C program into Matlab and looking for your suggestion to improve the code as the code is not giving the correct output.
C program:
void prga(unsigned char S[], unsigned char out[], int len) {
int i=0,j=0,x,t;
unsigned char key;
for (x=0; x < len; ++x) {
i = (i + 1) % 256;
j = (j + S[i]) % 256;
t = S[i];
S[i] = S[j];
S[j] = t;
out[x] = S[(S[i] + S[j]) % 256];
}
}
Matlab program:
function [out, i, j, S]=rc4out(i, j, S)
%for x = 1:length(key) % It should not work here as no key mentioned
i = mod( (i+1), 256);
j = mod( j + S(i), 256);
t = S(i);
S(i) = S(j+1);
S(j+1) = t;
out = mod(S(S(i) + S(j+1), 256));

Answer 1

EDIT:
Try this it do the same think as the c function: The lengh of S should be >= 256 or you will exceed it as mod() could return such index. I suggest you to change 256 in the function with the lenght provided to solve this issue.
Here you don't need the key variable.
function out = prga(S, len)
i=0; j=0; x=[]; t=[];
for x=0:len-1
i = mod(i+1, 256);
j = mod(j+S(i+1), 256);
t = S(i+1);
S(i+1) = S(j+1);
S(j+1) = t;
out(x+1) = S(mod(S(i+1)+S(j+1), 256)+1);
end
end
Or you can use the key variable to controle the loop
function out = prga(S, key)
i=0; j=0; x=[]; t=[];
for x=0:length(key)-1
i = mod(i+1, 256);
j = mod(j+S(i+1), 256);
t = S(i+1);
S(i+1) = S(j+1);
S(j+1) = t;
out(x+1) = S(mod(S(i+1)+S(j+1), 256)+1);
end
end