kc3-lang/libtommath/bn_mp_expt_u32.c

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• Hash : ca89e9c0
  Author :
  Date : 2019-07-03T13:10:05
  

  rename mp_root/mp_expt to mp_*_u32

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• bn_mp_expt_u32.c

• #include "tommath_private.h"
  #ifdef BN_MP_EXPT_U32_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  /* calculate c = a**b  using a square-multiply algorithm */
  mp_err mp_expt_u32(const mp_int *a, uint32_t b, mp_int *c)
  {
     mp_err err;
  
     mp_int  g;
  
     if ((err = mp_init_copy(&g, a)) != MP_OKAY) {
        return err;
     }
  
     /* set initial result */
     mp_set(c, 1uL);
  
     while (b > 0u) {
        /* if the bit is set multiply */
        if ((b & 1u) != 0u) {
           if ((err = mp_mul(c, &g, c)) != MP_OKAY) {
              mp_clear(&g);
              return err;
           }
        }
  
        /* square */
        if (b > 1u) {
           if ((err = mp_sqr(&g, &g)) != MP_OKAY) {
              mp_clear(&g);
              return err;
           }
        }
  
        /* shift to next bit */
        b >>= 1;
     }
  
     mp_clear(&g);
     return MP_OKAY;
  }
  
  #endif
  

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