kc3-lang/libtommath/bn_mp_tc_xor.c

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• Hash : 434dbcab
  Author :
  Date : 2018-09-23T10:16:25
  

  refactor without bitwise operator

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• bn_mp_tc_xor.c

• #include "tommath_private.h"
  #ifdef BN_MP_TC_XOR_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis
   *
   * LibTomMath is a library that provides multiple-precision
   * integer arithmetic as well as number theoretic functionality.
   *
   * The library was designed directly after the MPI library by
   * Michael Fromberger but has been written from scratch with
   * additional optimizations in place.
   *
   * The library is free for all purposes without any express
   * guarantee it works.
   */
  
  /* two complement xor */
  int mp_tc_xor(const mp_int *a, const mp_int *b, mp_int *c)
  {
     int res = MP_OKAY, bits;
     int as = mp_isneg(a), bs = mp_isneg(b);
     mp_int *mx = NULL, _mx, acpy, bcpy;
  
     if ((as != MP_NO) || (bs != MP_NO)) {
        bits = MAX(mp_count_bits(a), mp_count_bits(b));
        res = mp_init_set_int(&_mx, 1uL);
        if (res != MP_OKAY) {
           goto end;
        }
  
        mx = &_mx;
        res = mp_mul_2d(mx, bits + 1, mx);
        if (res != MP_OKAY) {
           goto end;
        }
  
        if (as != MP_NO) {
           res = mp_init(&acpy);
           if (res != MP_OKAY) {
              goto end;
           }
  
           res = mp_add(mx, a, &acpy);
           if (res != MP_OKAY) {
              mp_clear(&acpy);
              goto end;
           }
           a = &acpy;
        }
        if (bs != MP_NO) {
           res = mp_init(&bcpy);
           if (res != MP_OKAY) {
              goto end;
           }
  
           res = mp_add(mx, b, &bcpy);
           if (res != MP_OKAY) {
              mp_clear(&bcpy);
              goto end;
           }
           b = &bcpy;
        }
     }
  
     res = mp_xor(a, b, c);
  
     if ((as != bs) && (res == MP_OKAY)) {
        res = mp_sub(c, mx, c);
     }
  
  end:
     if (a == &acpy) {
        mp_clear(&acpy);
     }
  
     if (b == &bcpy) {
        mp_clear(&bcpy);
     }
  
     if (mx == &_mx) {
        mp_clear(mx);
     }
  
     return res;
  }
  #endif
  
  /* ref:         $Format:%D$ */
  /* git commit:  $Format:%H$ */
  /* commit time: $Format:%ai$ */
  

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