text: #.  Copyright (C) 2005-2010   Gregory P. Smith (greg@krypto.org)
  #  Licensed to PSF under a Contributor Agreement.
  #
  
  __doc__ = """hashlib module - A common interface to many hash functions.
  
  new(name, data=b'', **kwargs) - returns a new hash object implementing the
                                  given hash function; initializing the hash
                                  using the given binary data.
  
  Named constructor functions are also available, these are faster
  than using new(name):
  
  md5(), sha1(), sha224(), sha256(), sha384(), sha512(), blake2b(), blake2s(),
  sha3_224, sha3_256, sha3_384, sha3_512, shake_128, and shake_256.
  
  More algorithms may be available on your platform but the above are guaranteed
  to exist.  See the algorithms_guaranteed and algorithms_available attributes
  to find out what algorithm names can be passed to new().
  
  NOTE: If you want the adler32 or crc32 hash functions they are available in
  the zlib module.
  
  Choose your hash function wisely.  Some have known collision weaknesses.
  sha384 and sha512 will be slow on 32 bit platforms.
  
  Hash objects have these methods:
   - update(data): Update the hash object with the bytes in data. Repeated calls
                   are equivalent to a single call with the concatenation of all
                   the arguments.
   - digest():     Return the digest of the bytes passed to the update() method
                   so far as a bytes object.
   - hexdigest():  Like digest() except the digest is returned as a string
                   of double length, containing only hexadecimal digits.
   - copy():       Return a copy (clone) of the hash object. This can be used to
                   efficiently compute the digests of datas that share a common
                   initial substring.
  
  For example, to obtain the digest of the byte string 'Nobody inspects the
  spammish repetition':
  
      >>> import hashlib
      >>> m = hashlib.md5()
      >>> m.update(b"Nobody inspects")
      >>> m.update(b" the spammish repetition")
      >>> m.digest()
      b'\\xbbd\\x9c\\x83\\xdd\\x1e\\xa5\\xc9\\xd9\\xde\\xc9\\xa1\\x8d\\xf0\\xff\\xe9'
  
  More condensed:
  
      >>> hashlib.sha224(b"Nobody inspects the spammish repetition").hexdigest()
      'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'
  
  """
  
  # This tuple and __get_builtin_constructor() must be modified if a new
  # always available algorithm is added.
  __always_supported = ('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512',
                        'blake2b', 'blake2s',
                        'sha3_224', 'sha3_256', 'sha3_384', 'sha3_512',
                        'shake_128', 'shake_256')
  
  
  algorithms_guaranteed = set(__always_supported)
  algorithms_available = set(__always_supported)
  
  __all__ = __always_supported + ('new', 'algorithms_guaranteed',
                                  'algorithms_available', 'pbkdf2_hmac')
  
  
  __builtin_constructor_cache = {}
  
  # Prefer our blake2 implementation
  # OpenSSL 1.1.0 comes with a limited implementation of blake2b/s. The OpenSSL
  # implementations neither support keyed blake2 (blake2 MAC) nor advanced
  # features like salt, personalization, or tree hashing. OpenSSL hash-only
  # variants are available as 'blake2b512' and 'blake2s256', though.
  __block_openssl_constructor = {
      'blake2b', 'blake2s',
  }
  
  def __get_builtin_constructor(name):
      cache = __builtin_constructor_cache
      constructor = cache.get(name)
      if constructor is not None:
          return constructor
      try:
          if name in {'SHA1', 'sha1'}:
              import _sha1
              cache['SHA1'] = cache['sha1'] = _sha1.sha1
          elif name in {'MD5', 'md5'}:
              import _md5
              cache['MD5'] = cache['md5'] = _md5.md5
          elif name in {'SHA256', 'sha256', 'SHA224', 'sha224'}:
              import _sha256
              cache['SHA224'] = cache['sha224'] = _sha256.sha224
              cache['SHA256'] = cache['sha256'] = _sha256.sha256
          elif name in {'SHA512', 'sha512', 'SHA384', 'sha384'}:
              import _sha512
              cache['SHA384'] = cache['sha384'] = _sha512.sha384
              cache['SHA512'] = cache['sha512'] = _sha512.sha512
          elif name in {'blake2b', 'blake2s'}:
              import _blake2
              cache['blake2b'] = _blake2.blake2b
              cache['blake2s'] = _blake2.blake2s
          elif name in {'sha3_224', 'sha3_256', 'sha3_384', 'sha3_512'}:
              import _sha3
              cache['sha3_224'] = _sha3.sha3_224
              cache['sha3_256'] = _sha3.sha3_256
              cache['sha3_384'] = _sha3.sha3_384
              cache['sha3_512'] = _sha3.sha3_512
          elif name in {'shake_128', 'shake_256'}:
              import _sha3
              cache['shake_128'] = _sha3.shake_128
              cache['shake_256'] = _sha3.shake_256
      except ImportError:
          pass  # no extension module, this hash is unsupported.
  
      constructor = cache.get(name)
      if constructor is not None:
          return constructor
  
      raise ValueError('unsupported hash type ' + name)
  
  
  def __get_openssl_constructor(name):
      if name in __block_openssl_constructor:
          # Prefer our builtin blake2 implementation.
          return __get_builtin_constructor(name)
      try:
          # MD5, SHA1, and SHA2 are in all supported OpenSSL versions
          # SHA3/shake are available in OpenSSL 1.1.1+
          f = getattr(_hashlib, 'openssl_' + name)
          # Allow the C module to raise ValueError.  The function will be
          # defined but the hash not actually available.  Don't fall back to
          # builtin if the current security policy blocks a digest, bpo#40695.
          f(usedforsecurity=False)
          # Use the C function directly (very fast)
          return f
      except (AttributeError, ValueError):
          return __get_builtin_constructor(name)
  
  
  def __py_new(name, data=b'', **kwargs):
      """new(name, data=b'', **kwargs) - Return a new hashing object using the
      named algorithm; optionally initialized with data (which must be
      a bytes-like object).
      """
      return __get_builtin_constructor(name)(data, **kwargs)
  
  
  def __hash_new(name, data=b'', **kwargs):
      """new(name, data=b'') - Return a new hashing object using the named algorithm;
      optionally initialized with data (which must be a bytes-like object).
      """
      if name in __block_openssl_constructor:
          # Prefer our builtin blake2 implementation.
          return __get_builtin_constructor(name)(data, **kwargs)
      try:
          return _hashlib.new(name, data, **kwargs)
      except ValueError:
          # If the _hashlib module (OpenSSL) doesn't support the named
          # hash, try using our builtin implementations.
          # This allows for SHA224/256 and SHA384/512 support even though
          # the OpenSSL library prior to 0.9.8 doesn't provide them.
          return __get_builtin_constructor(name)(data)
  
  
  try:
      import _hashlib
      new = __hash_new
      __get_hash = __get_openssl_constructor
      algorithms_available = algorithms_available.union(
              _hashlib.openssl_md_meth_names)
  except ImportError:
      _hashlib = None
      new = __py_new
      __get_hash = __get_builtin_constructor
  
  try:
      # OpenSSL's PKCS5_PBKDF2_HMAC requires OpenSSL 1.0+ with HMAC and SHA
      from _hashlib import pbkdf2_hmac
  except ImportError:
      from warnings import warn as _warn
      _trans_5C = bytes((x ^ 0x5C) for x in range(256))
      _trans_36 = bytes((x ^ 0x36) for x in range(256))
  
      def pbkdf2_hmac(hash_name, password, salt, iterations, dklen=None):
          """Password based key derivation function 2 (PKCS #5 v2.0)
  
          This Python implementations based on the hmac module about as fast
          as OpenSSL's PKCS5_PBKDF2_HMAC for short passwords and much faster
          for long passwords.
          """
          _warn(
              "Python implementation of pbkdf2_hmac() is deprecated.",
              category=DeprecationWarning,
              stacklevel=2
          )
          if not isinstance(hash_name, str):
              raise TypeError(hash_name)
  
          if not isinstance(password, (bytes, bytearray)):
              password = bytes(memoryview(password))
          if not isinstance(salt, (bytes, bytearray)):
              salt = bytes(memoryview(salt))
  
          # Fast inline HMAC implementation
          inner = new(hash_name)
          outer = new(hash_name)
          blocksize = getattr(inner, 'block_size', 64)
          if len(password) > blocksize:
              password = new(hash_name, password).digest()
          password = password + b'\x00' * (blocksize - len(password))
          inner.update(password.translate(_trans_36))
          outer.update(password.translate(_trans_5C))
  
          def prf(msg, inner=inner, outer=outer):
              # PBKDF2_HMAC uses the password as key. We can re-use the same
              # digest objects and just update copies to skip initialization.
              icpy = inner.copy()
              ocpy = outer.copy()
              icpy.update(msg)
              ocpy.update(icpy.digest())
              return ocpy.digest()
  
          if iterations < 1:
              raise ValueError(iterations)
          if dklen is None:
              dklen = outer.digest_size
          if dklen < 1:
              raise ValueError(dklen)
  
          dkey = b''
          loop = 1
          from_bytes = int.from_bytes
          while len(dkey) < dklen:
              prev = prf(salt + loop.to_bytes(4))
              # endianness doesn't matter here as long to / from use the same
              rkey = from_bytes(prev)
              for i in range(iterations - 1):
                  prev = prf(prev)
                  # rkey = rkey ^ prev
                  rkey ^= from_bytes(prev)
              loop += 1
              dkey += rkey.to_bytes(inner.digest_size)
  
          return dkey[:dklen]
  
  try:
      # OpenSSL's scrypt requires OpenSSL 1.1+
      from _hashlib import scrypt
  except ImportError:
      pass
  
  
  for __func_name in __always_supported:
      # try them all, some may not work due to the OpenSSL
      # version not supporting that algorithm.
      try:
          globals()[__func_name] = __get_hash(__func_name)
      except ValueError:
          import logging
          logging.exception('code for hash %s was not found.', __func_name)
  
  
  # Cleanup locals()
  del __always_supported, __func_name, __get_hash
  del __py_new, __hash_new, __get_openssl_constructor
  