kc3-lang/libtommath/mp_hash.c

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• Hash : f12c2ab5
  Author :
  Date : 2021-03-26T10:47:25
  

  Add FNV-1a hash function This allows to compute non-cryptographic hash of mp_int which can be used as a key in a hash table.

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• mp_hash.c

• #include "tommath_private.h"
  #ifdef MP_HASH_C
  /* LibTomMath, multiple-precision integer library -- Tom St Denis */
  /* SPDX-License-Identifier: Unlicense */
  
  #if defined(MP_16BIT)
  #define FNV_1A_INIT ((uint32_t)0x811c9dc5)
  #define FNV_1A_PRIME ((uint32_t)0x01000193)
  #else
  #define FNV_1A_INIT ((uint64_t)0xcbf29ce484222325ULL)
  #define FNV_1A_PRIME ((uint64_t)0x100000001b3ULL)
  #endif
  
  /* computes hash of mp_int. */
  mp_err mp_hash(mp_int *a, mp_hval *hash)
  {
     int  x;
     mp_hval hval = FNV_1A_INIT;
     mp_digit r, mask, shift;
  
     /* FNV-1a algorithm */
     mask = ((mp_digit)1 << 8) - 1uL;
     shift = (mp_digit)(MP_DIGIT_BIT - 8);
     r = 0;
     for (x = a->used; x --> 0;) {
        mp_digit rr = a->dp[x] & mask;
        hval ^= (mp_hval)(a->dp[x] >> 8) | (r << shift);
        hval *= FNV_1A_PRIME;
        r = rr;
     }
     hval ^= mp_isneg(a) ? (mp_hval)1 : (mp_hval)0;
     *hash = hval * FNV_1A_PRIME;
  
     return MP_OKAY;
  }
  #endif
  

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