# $Id: hashlib.py 66093 2008-08-31 16:34:18Z gregory.p.smith $

#

#  Copyright (C) 2005   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, string='') - returns a new hash object implementing the

                       given hash function; initializing the hash

                       using the given string data.

Named constructor functions are also available, these are much faster

than using new():

md5(), sha1(), sha224(), sha256(), sha384(), and sha512()

More algorithms may be available on your platform but the above are

guaranteed to exist.

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(arg): Update the hash object with the string arg. Repeated calls

                are equivalent to a single call with the concatenation of all

                the arguments.

 - digest():    Return the digest of the strings passed to the update() method

                so far. This may contain non-ASCII characters, including

                NUL bytes.

 - 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 strings that share a common

                initial substring.

For example, to obtain the digest of the string 'Nobody inspects the

spammish repetition':

    >>> import hashlib

    >>> m = hashlib.md5()

    >>> m.update("Nobody inspects")

    >>> m.update(" the spammish repetition")

    >>> m.digest()

    '\\xbbd\\x9c\\x83\\xdd\\x1e\\xa5\\xc9\\xd9\\xde\\xc9\\xa1\\x8d\\xf0\\xff\\xe9'

More condensed:

    >>> hashlib.sha224("Nobody inspects the spammish repetition").hexdigest()

    'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'

"""

def __get_builtin_constructor(name):

    if name in ('SHA1', 'sha1'):

        import _sha

        return _sha.new

    elif name in ('MD5', 'md5'):

        import _md5

        return _md5.new

    elif name in ('SHA256', 'sha256', 'SHA224', 'sha224'):

        import _sha256

        bs = name[3:]

        if bs == '256':

            return _sha256.sha256

        elif bs == '224':

            return _sha256.sha224

    elif name in ('SHA512', 'sha512', 'SHA384', 'sha384'):

        import _sha512

        bs = name[3:]

        if bs == '512':

            return _sha512.sha512

        elif bs == '384':

            return _sha512.sha384

    raise ValueError, "unsupported hash type"

def __py_new(name, string=''):

    """new(name, string='') - Return a new hashing object using the named algorithm;

    optionally initialized with a string.

    """

    return __get_builtin_constructor(name)(string)

def __hash_new(name, string=''):

    """new(name, string='') - Return a new hashing object using the named algorithm;

    optionally initialized with a string.

    """

    try:

        return _hashlib.new(name, string)

    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)(string)

try:

    import _hashlib

    # use the wrapper of the C implementation

    new = __hash_new

    for opensslFuncName in filter(lambda n: n.startswith('openssl_'), dir(_hashlib)):

        funcName = opensslFuncName[len('openssl_'):]

        try:

            # try them all, some may not work due to the OpenSSL

            # version not supporting that algorithm.

            f = getattr(_hashlib, opensslFuncName)

            f()

            # Use the C function directly (very fast)

            exec funcName + ' = f'

        except ValueError:

            try:

                # Use the builtin implementation directly (fast)

                exec funcName + ' = __get_builtin_constructor(funcName)'

            except ValueError:

                # this one has no builtin implementation, don't define it

                pass

    # clean up our locals

    del f

    del opensslFuncName

    del funcName

except ImportError:

    # We don't have the _hashlib OpenSSL module?

    # use the built in legacy interfaces via a wrapper function

    new = __py_new

    # lookup the C function to use directly for the named constructors

    md5 = __get_builtin_constructor('md5')

    sha1 = __get_builtin_constructor('sha1')

    sha224 = __get_builtin_constructor('sha224')

    sha256 = __get_builtin_constructor('sha256')

    sha384 = __get_builtin_constructor('sha384')

    sha512 = __get_builtin_constructor('sha512')