dulwich/dulwich/_compat.py

# _compat.py -- For dealing with python2.4 oddness
# Copyright (C) 2008 Canonical Ltd.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; version 2
# of the License or (at your option) a later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
# MA  02110-1301, USA.

"""Misc utilities to work with python <2.6.

These utilities can all be deleted when dulwich decides it wants to stop
support for python <2.6.
"""
try:
    import hashlib
except ImportError:
    import sha

try:
    from urlparse import parse_qs
except ImportError:
    from cgi import parse_qs

try:
    from os import SEEK_CUR, SEEK_END
except ImportError:
    SEEK_CUR = 1
    SEEK_END = 2

import struct


def make_sha(source=''):
    """A python2.4 workaround for the sha/hashlib module fiasco."""
    try:
        return hashlib.sha1(source)
    except NameError:
        sha1 = sha.sha(source)
        return sha1


def unpack_from(fmt, buf, offset=0):
    """A python2.4 workaround for struct missing unpack_from."""
    try:
        return struct.unpack_from(fmt, buf, offset)
    except AttributeError:
        b = buf[offset:offset+struct.calcsize(fmt)]
        return struct.unpack(fmt, b)


try:
    all = all
except NameError:
    # Implementation of all from Python 2.6 documentation:
    # http://docs.python.org/2.6/library/functions.html#all
    # Copyright (c) 2001-2010 Python Software Foundation; All Rights Reserved
    # Licensed under the Python Software Foundation License.
    def all(iterable):
        for element in iterable:
            if not element:
                return False
        return True


try:
    from collections import namedtuple
except ImportError:
    # Recipe for namedtuple from http://code.activestate.com/recipes/500261/
    # Copyright (c) 2007 Python Software Foundation; All Rights Reserved
    # Licensed under the Python Software Foundation License.
    from operator import itemgetter as _itemgetter
    from keyword import iskeyword as _iskeyword
    import sys as _sys

    def namedtuple(typename, field_names, verbose=False, rename=False):
        """Returns a new subclass of tuple with named fields.

        >>> Point = namedtuple('Point', 'x y')
        >>> Point.__doc__                   # docstring for the new class
        'Point(x, y)'
        >>> p = Point(11, y=22)             # instantiate with positional args or keywords
        >>> p[0] + p[1]                     # indexable like a plain tuple
        33
        >>> x, y = p                        # unpack like a regular tuple
        >>> x, y
        (11, 22)
        >>> p.x + p.y                       # fields also accessable by name
        33
        >>> d = p._asdict()                 # convert to a dictionary
        >>> d['x']
        11
        >>> Point(**d)                      # convert from a dictionary
        Point(x=11, y=22)
        >>> p._replace(x=100)               # _replace() is like str.replace() but targets named fields
        Point(x=100, y=22)

        """

        # Parse and validate the field names.  Validation serves two purposes,
        # generating informative error messages and preventing template injection attacks.
        if isinstance(field_names, basestring):
            field_names = field_names.replace(',', ' ').split() # names separated by whitespace and/or commas
        field_names = tuple(map(str, field_names))
        if rename:
            names = list(field_names)
            seen = set()
            for i, name in enumerate(names):
                if (not min(c.isalnum() or c=='_' for c in name) or _iskeyword(name)
                    or not name or name[0].isdigit() or name.startswith('_')
                    or name in seen):
                        names[i] = '_%d' % i
                seen.add(name)
            field_names = tuple(names)
        for name in (typename,) + field_names:
            if not min(c.isalnum() or c=='_' for c in name):
                raise ValueError('Type names and field names can only contain alphanumeric characters and underscores: %r' % name)
            if _iskeyword(name):
                raise ValueError('Type names and field names cannot be a keyword: %r' % name)
            if name[0].isdigit():
                raise ValueError('Type names and field names cannot start with a number: %r' % name)
        seen_names = set()
        for name in field_names:
            if name.startswith('_') and not rename:
                raise ValueError('Field names cannot start with an underscore: %r' % name)
            if name in seen_names:
                raise ValueError('Encountered duplicate field name: %r' % name)
            seen_names.add(name)

        # Create and fill-in the class template
        numfields = len(field_names)
        argtxt = repr(field_names).replace("'", "")[1:-1]   # tuple repr without parens or quotes
        reprtxt = ', '.join('%s=%%r' % name for name in field_names)
        template = '''class %(typename)s(tuple):
        '%(typename)s(%(argtxt)s)' \n
        __slots__ = () \n
        _fields = %(field_names)r \n
        def __new__(_cls, %(argtxt)s):
            return _tuple.__new__(_cls, (%(argtxt)s)) \n
        @classmethod
        def _make(cls, iterable, new=tuple.__new__, len=len):
            'Make a new %(typename)s object from a sequence or iterable'
            result = new(cls, iterable)
            if len(result) != %(numfields)d:
                raise TypeError('Expected %(numfields)d arguments, got %%d' %% len(result))
            return result \n
        def __repr__(self):
            return '%(typename)s(%(reprtxt)s)' %% self \n
        def _asdict(self):
            'Return a new dict which maps field names to their values'
            return dict(zip(self._fields, self)) \n
        def _replace(_self, **kwds):
            'Return a new %(typename)s object replacing specified fields with new values'
            result = _self._make(map(kwds.pop, %(field_names)r, _self))
            if kwds:
                raise ValueError('Got unexpected field names: %%r' %% kwds.keys())
            return result \n
        def __getnewargs__(self):
            return tuple(self) \n\n''' % locals()
        for i, name in enumerate(field_names):
            template += '        %s = _property(_itemgetter(%d))\n' % (name, i)
        if verbose:
            print template

        # Execute the template string in a temporary namespace
        namespace = dict(_itemgetter=_itemgetter, __name__='namedtuple_%s' % typename,
                         _property=property, _tuple=tuple)
        try:
            exec template in namespace
        except SyntaxError, e:
            raise SyntaxError(e.message + ':\n' + template)
        result = namespace[typename]

        # For pickling to work, the __module__ variable needs to be set to the frame
        # where the named tuple is created.  Bypass this step in enviroments where
        # sys._getframe is not defined (Jython for example) or sys._getframe is not
        # defined for arguments greater than 0 (IronPython).
        try:
            result.__module__ = _sys._getframe(1).f_globals.get('__name__', '__main__')
        except (AttributeError, ValueError):
            pass

        return result


# Backport of OrderedDict() class that runs on Python 2.4, 2.5, 2.6, 2.7 and pypy.
# Passes Python2.7's test suite and incorporates all the latest updates.
# Copyright (C) Raymond Hettinger, MIT license

try:
    from thread import get_ident as _get_ident
except ImportError:
    from dummy_thread import get_ident as _get_ident

try:
    from _abcoll import KeysView, ValuesView, ItemsView
except ImportError:
    pass

class OrderedDict(dict):
    'Dictionary that remembers insertion order'
    # An inherited dict maps keys to values.
    # The inherited dict provides __getitem__, __len__, __contains__, and get.
    # The remaining methods are order-aware.
    # Big-O running times for all methods are the same as for regular dictionaries.

    # The internal self.__map dictionary maps keys to links in a doubly linked list.
    # The circular doubly linked list starts and ends with a sentinel element.
    # The sentinel element never gets deleted (this simplifies the algorithm).
    # Each link is stored as a list of length three:  [PREV, NEXT, KEY].

    def __init__(self, *args, **kwds):
        '''Initialize an ordered dictionary.  Signature is the same as for
        regular dictionaries, but keyword arguments are not recommended
        because their insertion order is arbitrary.

        '''
        if len(args) > 1:
            raise TypeError('expected at most 1 arguments, got %d' % len(args))
        try:
            self.__root
        except AttributeError:
            self.__root = root = []                     # sentinel node
            root[:] = [root, root, None]
            self.__map = {}
        self.__update(*args, **kwds)

    def __setitem__(self, key, value, dict_setitem=dict.__setitem__):
        'od.__setitem__(i, y) <==> od[i]=y'
        # Setting a new item creates a new link which goes at the end of the linked
        # list, and the inherited dictionary is updated with the new key/value pair.
        if key not in self:
            root = self.__root
            last = root[0]
            last[1] = root[0] = self.__map[key] = [last, root, key]
        dict_setitem(self, key, value)

    def __delitem__(self, key, dict_delitem=dict.__delitem__):
        'od.__delitem__(y) <==> del od[y]'
        # Deleting an existing item uses self.__map to find the link which is
        # then removed by updating the links in the predecessor and successor nodes.
        dict_delitem(self, key)
        link_prev, link_next, key = self.__map.pop(key)
        link_prev[1] = link_next
        link_next[0] = link_prev

    def __iter__(self):
        'od.__iter__() <==> iter(od)'
        root = self.__root
        curr = root[1]
        while curr is not root:
            yield curr[2]
            curr = curr[1]

    def __reversed__(self):
        'od.__reversed__() <==> reversed(od)'
        root = self.__root
        curr = root[0]
        while curr is not root:
            yield curr[2]
            curr = curr[0]

    def clear(self):
        'od.clear() -> None.  Remove all items from od.'
        try:
            for node in self.__map.itervalues():
                del node[:]
            root = self.__root
            root[:] = [root, root, None]
            self.__map.clear()
        except AttributeError:
            pass
        dict.clear(self)

    def popitem(self, last=True):
        """od.popitem() -> (k, v), return and remove a (key, value) pair.
        Pairs are returned in LIFO order if last is true or FIFO order if false.

        """
        if not self:
            raise KeyError('dictionary is empty')
        root = self.__root
        if last:
            link = root[0]
            link_prev = link[0]
            link_prev[1] = root
            root[0] = link_prev
        else:
            link = root[1]
            link_next = link[1]
            root[1] = link_next
            link_next[0] = root
        key = link[2]
        del self.__map[key]
        value = dict.pop(self, key)
        return key, value

    # -- the following methods do not depend on the internal structure --

    def keys(self):
        """'od.keys() -> list of keys in od"""
        return list(self)

    def values(self):
        """od.values() -> list of values in od"""
        return [self[key] for key in self]

    def items(self):
        """od.items() -> list of (key, value) pairs in od"""
        return [(key, self[key]) for key in self]

    def iterkeys(self):
        """od.iterkeys() -> an iterator over the keys in od"""
        return iter(self)

    def itervalues(self):
        """od.itervalues -> an iterator over the values in od"""
        for k in self:
            yield self[k]

    def iteritems(self):
        """od.iteritems -> an iterator over the (key, value) items in od"""
        for k in self:
            yield (k, self[k])

    def update(*args, **kwds):
        """od.update(E, F) -> None.  Update od from dict/iterable E and F.

        If E is a dict instance, does:           for k in E: od[k] = E[k]
        If E has a .keys() method, does:         for k in E.keys(): od[k] = E[k]
        Or if E is an iterable of items, does:   for k, v in E: od[k] = v
        In either case, this is followed by:     for k, v in F.items(): od[k] = v
        """
        if len(args) > 2:
            raise TypeError('update() takes at most 2 positional '
                            'arguments (%d given)' % (len(args),))
        elif not args:
            raise TypeError('update() takes at least 1 argument (0 given)')
        self = args[0]
        # Make progressively weaker assumptions about "other"
        other = ()
        if len(args) == 2:
            other = args[1]
        if isinstance(other, dict):
            for key in other:
                self[key] = other[key]
        elif hasattr(other, 'keys'):
            for key in other.keys():
                self[key] = other[key]
        else:
            for key, value in other:
                self[key] = value
        for key, value in kwds.items():
            self[key] = value

    __update = update  # let subclasses override update without breaking __init__

    __marker = object()

    def pop(self, key, default=__marker):
        """od.pop(k[,d]) -> v, remove specified key and return the corresponding value.
        If key is not found, d is returned if given, otherwise KeyError is raised.

        """
        if key in self:
            result = self[key]
            del self[key]
            return result
        if default is self.__marker:
            raise KeyError(key)
        return default

    def setdefault(self, key, default=None):
        'od.setdefault(k[,d]) -> od.get(k,d), also set od[k]=d if k not in od'
        if key in self:
            return self[key]
        self[key] = default
        return default

    def __repr__(self, _repr_running={}):
        'od.__repr__() <==> repr(od)'
        call_key = id(self), _get_ident()
        if call_key in _repr_running:
            return '...'
        _repr_running[call_key] = 1
        try:
            if not self:
                return '%s()' % (self.__class__.__name__,)
            return '%s(%r)' % (self.__class__.__name__, self.items())
        finally:
            del _repr_running[call_key]

    def __reduce__(self):
        'Return state information for pickling'
        items = [[k, self[k]] for k in self]
        inst_dict = vars(self).copy()
        for k in vars(OrderedDict()):
            inst_dict.pop(k, None)
        if inst_dict:
            return (self.__class__, (items,), inst_dict)
        return self.__class__, (items,)

    def copy(self):
        'od.copy() -> a shallow copy of od'
        return self.__class__(self)

    @classmethod
    def fromkeys(cls, iterable, value=None):
        '''OD.fromkeys(S[, v]) -> New ordered dictionary with keys from S
        and values equal to v (which defaults to None).

        '''
        d = cls()
        for key in iterable:
            d[key] = value
        return d

    def __eq__(self, other):
        '''od.__eq__(y) <==> od==y.  Comparison to another OD is order-sensitive
        while comparison to a regular mapping is order-insensitive.

        '''
        if isinstance(other, OrderedDict):
            return len(self)==len(other) and self.items() == other.items()
        return dict.__eq__(self, other)

    def __ne__(self, other):
        return not self == other

    # -- the following methods are only used in Python 2.7 --

    def viewkeys(self):
        "od.viewkeys() -> a set-like object providing a view on od's keys"
        return KeysView(self)

    def viewvalues(self):
        "od.viewvalues() -> an object providing a view on od's values"
        return ValuesView(self)

    def viewitems(self):
        "od.viewitems() -> a set-like object providing a view on od's items"
        return ItemsView(self)