UV
Perl_get_hash_seed(pTHX)
{
    dVAR;
     const char *s = PerlEnv_getenv("PERL_HASH_SEED");
     UV myseed = 0;

     if (s)
        while (isSPACE(*s))
            s++;
     if (s && isDIGIT(*s))
          myseed = (UV)Atoul(s);
     else
#ifdef USE_HASH_SEED_EXPLICIT
     if (s)
#endif
     {
          /* Compute a random seed */
          (void)seedDrand01((Rand_seed_t)seed());
          myseed = (UV)(Drand01() * (NV)UV_MAX);
#if RANDBITS < (UVSIZE * 8)
          /* Since there are not enough randbits to to reach all
           * the bits of a UV, the low bits might need extra
           * help.  Sum in another random number that will
           * fill in the low bits. */
          myseed +=
               (UV)(Drand01() * (NV)((((UV)1) << ((UVSIZE * 8 - RANDBITS))) - 1)
»);
#endif /* RANDBITS < (UVSIZE * 8) */
          if (myseed == 0) { /* Superparanoia. */
              myseed = (UV)(Drand01() * (NV)UV_MAX); /* One more chance. */
              if (myseed == 0)
                  Perl_croak(aTHX_ "Your random numbers are not that random");
          }
     }
     PL_rehash_seed_set = TRUE;

     return myseed;
}