sys/src/libmp/port/mpvecadd.c

   1 #include "os.h"
   2 #include <mp.h>
   3 #include "dat.h"
   4
   5 // prereq: alen >= blen, sum has at least blen+1 digits
   6 void
   7 mpvecadd(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *sum)
   8 {
   9         int i, carry;
  10         mpdigit x, y;
  11
  12         carry = 0;
  13         for(i = 0; i < blen; i++){
  14                 x = *a++;
  15                 y = *b++;
  16                 x += carry;
  17                 if(x < carry)
  18                         carry = 1;
  19                 else
  20                         carry = 0;
  21                 x += y;
  22                 if(x < y)
  23                         carry++;
  24                 *sum++ = x;
  25         }
  26         for(; i < alen; i++){
  27                 x = *a++ + carry;
  28                 if(x < carry)
  29                         carry = 1;
  30                 else
  31                         carry = 0;
  32                 *sum++ = x;
  33         }
  34         *sum = carry;
  35 }