path: root/passlib/utils/compat.py

"""passlib.utils.compat - python 2/3 compatibility helpers"""
#=============================================================================
# figure out what we're running
#=============================================================================

#-----------------------------------------------------
# python version
#-----------------------------------------------------
import sys
PY2 = sys.version_info < (3,0)
PY3 = sys.version_info >= (3,0)
PY_MAX_25 = sys.version_info < (2,6) # py 2.5 or earlier
PY27 = sys.version_info[:2] == (2,7) # supports last 2.x release
PY_MIN_32 = sys.version_info >= (3,2) # py 3.2 or later

#-----------------------------------------------------
# python implementation
#-----------------------------------------------------
PYPY = hasattr(sys, "pypy_version_info")
JYTHON = sys.platform.startswith('java')

#-----------------------------------------------------
# capabilities
#-----------------------------------------------------

# __dir__() added in py2.6
SUPPORTS_DIR_METHOD = not PY_MAX_25 and not (PYPY and sys.pypy_version_info < (1,6))

#=============================================================================
# common imports
#=============================================================================
import logging; log = logging.getLogger(__name__)
if PY3:
    import builtins
else:
    import __builtin__ as builtins

def add_doc(obj, doc):
    """add docstring to an object"""
    obj.__doc__ = doc

#=============================================================================
# the default exported vars
#=============================================================================
__all__ = [
    # python versions
    'PY2', 'PY3', 'PY_MAX_25', 'PY27', 'PY_MIN_32',

    # io
    'BytesIO', 'StringIO', 'NativeStringIO', 'SafeConfigParser',
    'print_',

    # type detection
##    'is_mapping',
    'callable',
    'int_types',
    'num_types',
    'base_string_types',

    # unicode/bytes types & helpers
    'u', 'b',
    'unicode', 'bytes',
    'uascii_to_str', 'bascii_to_str',
    'str_to_uascii', 'str_to_bascii',
    'join_unicode', 'join_bytes',
    'join_byte_values', 'join_byte_elems',
    'byte_elem_value',
    'iter_byte_values',

    # iteration helpers
    'irange', #'lrange',
    'imap', 'lmap',
    'iteritems', 'itervalues',
    'next',

    # introspection
    'exc_err', 'get_method_function', 'add_doc',
]

# begin accumulating mapping of lazy-loaded attrs,
# 'merged' into module at bottom
_lazy_attrs = dict()

#=============================================================================
# unicode & bytes types
#=============================================================================
if PY3:
    unicode = str
    bytes = builtins.bytes

    def u(s):
        assert isinstance(s, str)
        return s

    def b(s):
        assert isinstance(s, str)
        return s.encode("latin-1")

    base_string_types = (unicode, bytes)

else:
    unicode = builtins.unicode
    bytes = str if PY_MAX_25 else builtins.bytes

    def u(s):
        assert isinstance(s, str)
        return s.decode("unicode_escape")

    def b(s):
        assert isinstance(s, str)
        return s

    base_string_types = basestring

#=============================================================================
# unicode & bytes helpers
#=============================================================================
# function to join list of unicode strings
join_unicode = u('').join

# function to join list of byte strings
join_bytes = b('').join

if PY3:
    def uascii_to_str(s):
        assert isinstance(s, unicode)
        return s

    def bascii_to_str(s):
        assert isinstance(s, bytes)
        return s.decode("ascii")

    def str_to_uascii(s):
        assert isinstance(s, str)
        return s

    def str_to_bascii(s):
        assert isinstance(s, str)
        return s.encode("ascii")

    join_byte_values = join_byte_elems = bytes

    def byte_elem_value(elem):
        assert isinstance(elem, int)
        return elem

    def iter_byte_values(s):
        assert isinstance(s, bytes)
        return s

    def iter_byte_chars(s):
        assert isinstance(s, bytes)
        # FIXME: there has to be a better way to do this
        return (bytes([c]) for c in s)

else:
    def uascii_to_str(s):
        assert isinstance(s, unicode)
        return s.encode("ascii")

    def bascii_to_str(s):
        assert isinstance(s, bytes)
        return s

    def str_to_uascii(s):
        assert isinstance(s, str)
        return s.decode("ascii")

    def str_to_bascii(s):
        assert isinstance(s, str)
        return s

    def join_byte_values(values):
        return join_bytes(chr(v) for v in values)

    join_byte_elems = join_bytes

    byte_elem_value = ord

    def iter_byte_values(s):
        assert isinstance(s, bytes)
        return (ord(c) for c in s)

    def iter_byte_chars(s):
        assert isinstance(s, bytes)
        return s

add_doc(uascii_to_str, "helper to convert ascii unicode -> native str")
add_doc(bascii_to_str, "helper to convert ascii bytes -> native str")
add_doc(str_to_uascii, "helper to convert ascii native str -> unicode")
add_doc(str_to_bascii, "helper to convert ascii native str -> bytes")

# join_byte_values -- function to convert list of ordinal integers to byte string.

# join_byte_elems --  function to convert list of byte elements to byte string;
#                 i.e. what's returned by ``b('a')[0]``...
#                 this is b('a') under PY2, but 97 under PY3.

# byte_elem_value -- function to convert byte element to integer -- a noop under PY3

add_doc(iter_byte_values, "iterate over byte string as sequence of ints 0-255")
add_doc(iter_byte_chars, "iterate over byte string as sequence of 1-byte strings")

#=============================================================================
# numeric
#=============================================================================
if PY3:
    int_types = (int,)
    num_types = (int, float)
else:
    int_types = (int, long)
    num_types = (int, long, float)

#=============================================================================
# iteration helpers
#
# irange - range iterable / view (xrange under py2, range under py3)
# lrange - range list (range under py2, list(range()) under py3)
#
# imap - map to iterator
# lmap - map to list
#=============================================================================
if PY3:
    irange = range
    ##def lrange(*a,**k):
    ##    return list(range(*a,**k))

    def lmap(*a, **k):
        return list(map(*a,**k))
    imap = map

    def iteritems(d):
        return d.items()
    def itervalues(d):
        return d.values()

    next_method_attr = "__next__"

else:
    irange = xrange
    ##lrange = range

    lmap = map
    from itertools import imap

    def iteritems(d):
        return d.iteritems()
    def itervalues(d):
        return d.itervalues()

    next_method_attr = "next"

if PY_MAX_25:
    _undef = object()
    def next(itr, default=_undef):
        "compat wrapper for next()"
        if default is _undef:
            return itr.next()
        try:
            return itr.next()
        except StopIteration:
            return default
else:
    next = builtins.next

#=============================================================================
# typing
#=============================================================================
##def is_mapping(obj):
##    # non-exhaustive check, enough to distinguish from lists, etc
##    return hasattr(obj, "items")

if (3,0) <= sys.version_info < (3,2):
    # callable isn't dead, it's just resting
    from collections import Callable
    def callable(obj):
        return isinstance(obj, Callable)
else:
    callable = builtins.callable

#=============================================================================
# introspection
#=============================================================================
def exc_err():
    "return current error object (to avoid try/except syntax change)"
    return sys.exc_info()[1]

if PY3:
    method_function_attr = "__func__"
else:
    method_function_attr = "im_func"

def get_method_function(func):
    "given (potential) method, return underlying function"
    return getattr(func, method_function_attr, func)

#=============================================================================
# input/output
#=============================================================================
if PY3:
    _lazy_attrs = dict(
        BytesIO="io.BytesIO",
        UnicodeIO="io.StringIO",
        NativeStringIO="io.StringIO",
        SafeConfigParser="configparser.SafeConfigParser",
    )
    if sys.version_info >= (3,2):
        # py32 renamed this, removing old ConfigParser
        _lazy_attrs["SafeConfigParser"] = "configparser.ConfigParser"

    print_ = getattr(builtins, "print")

else:
    _lazy_attrs = dict(
        BytesIO="cStringIO.StringIO",
        UnicodeIO="StringIO.StringIO",
        NativeStringIO="cStringIO.StringIO",
        SafeConfigParser="ConfigParser.SafeConfigParser",
    )

    def print_(*args, **kwds):
        """The new-style print function."""
        # extract kwd args
        fp = kwds.pop("file", sys.stdout)
        sep = kwds.pop("sep", None)
        end = kwds.pop("end", None)
        if kwds:
            raise TypeError("invalid keyword arguments")

        # short-circuit if no target
        if fp is None:
            return

        # use unicode or bytes ?
        want_unicode = isinstance(sep, unicode) or isinstance(end, unicode) or \
                       any(isinstance(arg, unicode) for arg in args)

        # pick default end sequence
        if end is None:
            end = u("\n") if want_unicode else "\n"
        elif not isinstance(end, base_string_types):
            raise TypeError("end must be None or a string")

        # pick default separator
        if sep is None:
            sep = u(" ") if want_unicode else " "
        elif not isinstance(sep, base_string_types):
            raise TypeError("sep must be None or a string")

        # write to buffer
        first = True
        write = fp.write
        for arg in args:
            if first:
                first = False
            else:
                write(sep)
            if not isinstance(arg, basestring):
                arg = str(arg)
            write(arg)
        write(end)

#=============================================================================
# lazy overlay module
#=============================================================================
from types import ModuleType

def _import_object(source):
    "helper to import object from module; accept format `path.to.object`"
    modname, modattr = source.rsplit(".",1)
    mod = __import__(modname, fromlist=[modattr], level=0)
    return getattr(mod, modattr)

class _LazyOverlayModule(ModuleType):
    """proxy module which overlays original module,
    and lazily imports specified attributes.

    this is mainly used to prevent importing of resources
    that are only needed by certain password hashes,
    yet allow them to be imported from a single location.

    used by :mod:`passlib.utils`, :mod:`passlib.utils.crypto`,
    and :mod:`passlib.utils.compat`.
    """

    @classmethod
    def replace_module(cls, name, attrmap):
        orig = sys.modules[name]
        self = cls(name, attrmap, orig)
        sys.modules[name] = self
        return self

    def __init__(self, name, attrmap, proxy=None):
        ModuleType.__init__(self, name)
        self.__attrmap = attrmap
        self.__proxy = proxy
        self.__log = logging.getLogger(name)

    def __getattr__(self, attr):
        proxy = self.__proxy
        if proxy and hasattr(proxy, attr):
            return getattr(proxy, attr)
        attrmap = self.__attrmap
        if attr in attrmap:
            source = attrmap[attr]
            if callable(source):
                value = source()
            else:
                value = _import_object(source)
            setattr(self, attr, value)
            self.__log.debug("loaded lazy attr %r: %r", attr, value)
            return value
        raise AttributeError("'module' object has no attribute '%s'" % (attr,))

    def __repr__(self):
        proxy = self.__proxy
        if proxy:
            return repr(proxy)
        else:
            return ModuleType.__repr__(self)

    def __dir__(self):
        attrs = set(dir(self.__class__))
        attrs.update(self.__dict__)
        attrs.update(self.__attrmap)
        proxy = self.__proxy
        if proxy is not None:
            attrs.update(dir(proxy))
        return list(attrs)

# replace this module with overlay that will lazily import attributes.
_LazyOverlayModule.replace_module(__name__, _lazy_attrs)

#=============================================================================
# eof
#=============================================================================