Hexadecimal Addition in C (Simple)

// function for adding two big number in big endian

static void add(const unsigned char *a, int la, const unsigned char *b, int lb, unsigned char *mul, int *lmul)

{

int ltemp = ((la>lb)?la:lb)+1;

int lmin = ((la>lb)?lb:la);

unsigned char *temp = (unsigned char*)malloc(ltemp);

int xa = la-1, xb = lb-1, y = ltemp-1, u = 0;

int k = 0, z = 0;

memset(temp, 0, ltemp);

while(xa>=0 && xb>=0)

{

temp[y] = a[xa] + b[xb] + u;

if( temp[y] < a[xa] )

u = 1;

else

u = 0;

y--;

xa--;

xb--;

}

while(temp[++k]==0);

for(z=k ; z<ltemp ; z++)

mul[z-k] = temp[z];

*lmul = z-k;

free(temp); 

}