1  #
       2  # These tests require gmpy and test the limits of the 32-bit build. The
       3  # limits of the 64-bit build are so large that they cannot be tested
       4  # on accessible hardware.
       5  #
       6  
       7  import sys
       8  from decimal import *
       9  from gmpy import mpz
      10  
      11  
      12  _PyHASH_MODULUS = sys.hash_info.modulus
      13  # hash values to use for positive and negative infinities, and nans
      14  _PyHASH_INF = sys.hash_info.inf
      15  _PyHASH_NAN = sys.hash_info.nan
      16  
      17  # _PyHASH_10INV is the inverse of 10 modulo the prime _PyHASH_MODULUS
      18  _PyHASH_10INV = pow(10, _PyHASH_MODULUS - 2, _PyHASH_MODULUS)
      19  
      20  def xhash(coeff, exp):
      21      sign = 1
      22      if coeff < 0:
      23          sign = -1
      24          coeff = -coeff
      25      if exp >= 0:
      26          exp_hash = pow(10, exp, _PyHASH_MODULUS)
      27      else:
      28          exp_hash = pow(_PyHASH_10INV, -exp, _PyHASH_MODULUS)
      29      hash_ = coeff * exp_hash % _PyHASH_MODULUS
      30      ans = hash_ if sign == 1 else -hash_
      31      return -2 if ans == -1 else ans
      32  
      33  
      34  x = mpz(10) ** 425000000 - 1
      35  coeff = int(x)
      36  
      37  d = Decimal('9' * 425000000 + 'e-849999999')
      38  
      39  h1 = xhash(coeff, -849999999)
      40  h2 = hash(d)
      41  
      42  assert h2 == h1