ass3/mart/sws1-assignment3-s4109503-s4202015/exercise2.c

   1 #include <stdlib.h>
   2 #include <stdio.h>
   3 #include <stdbool.h>
   4
   5 typedef unsigned char uc;
   6 typedef unsigned __int128 uint128;
   7
   8 void addvector(int *r, const int *a, const int *b, size_t len)
   9 {
  10         for(int *r2 = r; r2 < r + len; r2++)
  11                 *r2 = *a++ + *b++;
  12 }
  13
  14 int memcmp(const void *s1, const void *s2, size_t n)
  15 {
  16         for(uc *s3 = (uc*)s1, *s4 = (uc*)s2; s3 < (uc*)s1 + n; s3++, s4++)
  17                 if(*s3 != *s4)
  18                         return *s3-*s4;
  19         return 0;
  20 }
  21
  22 int memcmp_backwards(const void *s1, const void *s2, size_t n)
  23 {
  24         for(uc *s3 = (uc*)s1+n, *s4 = (uc*)s2+n; s3 >= (uc*)s1; s3--, s4--)
  25                 if(*s3 != *s4)
  26                         return *s3-*s4;
  27         return 0;
  28 }
  29
  30 int memcmp_fast(const void *s1, const void *s2, size_t n)
  31 {
  32         uint128 *s3 = (uint128 *)s1;
  33         uint128 *s4 = (uint128 *)s2;
  34         unsigned int blocks = n/sizeof(uint128);
  35         for(; s3<((uint128*)s1)+blocks; s3++, s4++)
  36                 if(*s3 != *s4)
  37                         return memcmp(s3, s4, sizeof(uint128));
  38         return memcmp(s3, s4, n % sizeof(uint128));
  39 }
  40
  41 int memcmp_consttime(const void *s1, const void *s2, size_t n)
  42 {
  43         int returnvalue = 0;
  44         for(uc *s3 = (uc*)s1, *s4 = (uc*)s2; s3 < (uc*)s1 + n; s3++, s4++)
  45                 if(*s3 != *s4 && returnvalue == 0)
  46                         returnvalue = *s3 - *s4;
  47         return returnvalue;
  48 }