path: root/lib/sqlalchemy/util.py

# util.py
# Copyright (C) 2005 Michael Bayer mike_mp@zzzcomputing.com
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any 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 Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

__all__ = ['OrderedProperties', 'OrderedDict']
import thread, weakref, UserList,string, inspect

def to_list(x):
    if x is None:
        return None
    if not isinstance(x, list) and not isinstance(x, tuple):
        return [x]
    else:
        return x
        
class OrderedProperties(object):
    """an object that maintains the order in which attributes are set upon it.
    also provides an iterator and a very basic dictionary interface to those attributes.
    """
    def __init__(self):
        self.__dict__['_list'] = []
    def keys(self):
        return self._list
    def get(self, key, default):
        return getattr(self, key, default)
    def has_key(self, key):
        return hasattr(self, key)
    def __iter__(self):
        return iter([self[x] for x in self._list])
    def __setitem__(self, key, object):
        setattr(self, key, object)
    def __getitem__(self, key):
        try:
          return getattr(self, key)
        except AttributeError:
          raise KeyError(key)
    def __delitem__(self, key):
        delattr(self, key)
        del self._list[self._list.index(key)]
    def __setattr__(self, key, object):
        if not hasattr(self, key):
            self._list.append(key)
    
        self.__dict__[key] = object
    

class OrderedDict(dict):
    """A Dictionary that keeps its own internal ordering"""
    def __init__(self, values = None):
        self.list = []
        if values is not None:
            for val in values:
                self.update(val)

    def keys(self):
        return self.list

    def clear(self):
        self.list = []
        dict.clear(self)
    
    def update(self, dict):
        for key in dict.keys():
            self.__setitem__(key, dict[key])

    def setdefault(self, key, value):
        if not self.has_key(key):
            self.__setitem__(key, value)
            return value
        else:
            return self.__getitem__(key)

    def values(self):
        return map(lambda key: self[key], self.list)
        
    def __iter__(self):
        return iter(self.list)

    def itervalues(self):
        return iter([self[key] for key in self.list])
        
    def iterkeys(self):return self.__iter__()
    
    def iteritems(self):
        return iter([(key, self[key]) for key in self.keys()])
    
    def __delitem__(self, key):
        try:
            del self.list[self.list.index(key)]
        except ValueError:
            raise KeyError(key)
        dict.__delitem__(self, key)
        
    def __setitem__(self, key, object):
        if not self.has_key(key):
            self.list.append(key)
        dict.__setitem__(self, key, object)
        
    def __getitem__(self, key):
        return dict.__getitem__(self, key)

class ThreadLocal(object):
    """an object in which attribute access occurs only within the context of the current thread"""
    def __init__(self, raiseerror = True):
        self.__dict__['_tdict'] = {}
        self.__dict__['_raiseerror'] = raiseerror
    def __getattr__(self, key):
        try:
            return self._tdict["%d_%s" % (thread.get_ident(), key)]
        except KeyError:
            if self._raiseerror:
                raise AttributeError(key)
            else:
                return None
    def __setattr__(self, key, value):
        self._tdict["%d_%s" % (thread.get_ident(), key)] = value

class HashSet(object):
    """implements a Set."""
    def __init__(self, iter = None, ordered = False):
        if ordered:
            self.map = OrderedDict()
        else:
            self.map  = {}
        if iter is not None:
            for i in iter:
                self.append(i)
    def __iter__(self):
        return iter(self.map.values())
    def contains(self, item):
        return self.map.has_key(item)
    def clear(self):
        self.map.clear()
    def append(self, item):
        self.map[item] = item
    def __add__(self, other):
        return HashSet(self.map.values() + [i for i in other])
    def __len__(self):
        return len(self.map)
    def __delitem__(self, key):
        del self.map[key]
    def __getitem__(self, key):
        return self.map[key]
        
class HistoryArraySet(UserList.UserList):
    """extends a UserList to provide unique-set functionality as well as history-aware 
    functionality, including information about what list elements were modified 
    and commit/rollback capability.  When a HistoryArraySet is created with or
    without initial data, it is in a "committed" state.  as soon as changes are made
    to the list via the normal list-based access, it tracks "added" and "deleted" items,
    which remain until the history is committed or rolled back."""
    def __init__(self, data = None, readonly=False):
        # stores the array's items as keys, and a value of True, False or None indicating
        # added, deleted, or unchanged for that item
        self.records = OrderedDict()
        if data is not None:
            self.data = data
            for item in data:
                # add items without triggering any change events
                # *ASSUME* the list is unique already.  might want to change this.
                self.records[item] = None
        else:
            self.data = []
        self.readonly=readonly
    def __getattr__(self, attr):
        """proxies unknown HistoryArraySet methods and attributes to the underlying
        data array.  this allows custom list classes to be used."""
        return getattr(self.data, attr)
    def set_data(self, data):
        """sets the data for this HistoryArraySet to be that of the given data.
        duplicates in the incoming list will be removed."""
        # first mark everything current as "deleted"
        for i in self.data:
            self.records[i] = False
            
        # switch array
        self.data = data

        # TODO: fix this up, remove items from array while iterating
        for i in range(0, len(self.data)):
            if not self._setrecord(self.data[i]):
               del self.data[i]
               i -= 1
    def history_contains(self, obj):
        """returns true if the given object exists within the history
        for this HistoryArrayList."""
        return self.records.has_key(obj)
    def __hash__(self):
        return id(self)
    def _setrecord(self, item):
        if self.readonly:
            raise "This list is read only"
        try:
            val = self.records[item]
            if val is True or val is None:
                return False
            else:
                self.records[item] = None
                return True
        except KeyError:
            self.records[item] = True
            return True
    def _delrecord(self, item):
        if self.readonly:
            raise "This list is read only"
        try:
            val = self.records[item]
            if val is None:
                self.records[item] = False
                return True
            elif val is True:
                del self.records[item]
                return True
            return False
        except KeyError:
            return False
    def commit(self):
        """commits the added values in this list to be the new "unchanged" values.
        values that have been marked as deleted are removed from the history."""
        for key in self.records.keys():
            value = self.records[key]
            if value is False:
                del self.records[key]
            else:
                self.records[key] = None
    def rollback(self):
        """rolls back changes to this list to the last "committed" state."""
        # TODO: speed this up
        list = []
        for key, status in self.records.iteritems():
            if status is False or status is None:
                list.append(key)
        self.data[:] = []
        self.records = {}
        for l in list:
            self.append_nohistory(l)
    def added_items(self):
        """returns a list of items that have been added since the last "committed" state."""
        return [key for key in self.data if self.records[key] is True]
    def deleted_items(self):
        """returns a list of items that have been deleted since the last "committed" state."""
        return [key for key, value in self.records.iteritems() if value is False]
    def unchanged_items(self):
        """returns a list of items that have not been changed since the last "committed" state."""
        return [key for key in self.data if self.records[key] is None]
    def append_nohistory(self, item):
        """appends an item to the list without affecting the "history"."""
        if not self.records.has_key(item):
            self.records[item] = None
            self.data.append(item)
    def remove_nohistory(self, item):
        """removes an item from the list without affecting the "history"."""
        if self.records.has_key(item):
            del self.records[item]
            self.data.remove(item)
    def has_item(self, item):
        return self.records.has_key(item)
    def __setitem__(self, i, item): 
        if self._setrecord(a):
            self.data[i] = item
    def __delitem__(self, i):
        self._delrecord(self.data[i])
        del self.data[i]
    def __setslice__(self, i, j, other):
        i = max(i, 0); j = max(j, 0)
        if isinstance(other, UserList.UserList):
            l = other.data
        elif isinstance(other, type(self.data)):
            l = other
        else:
            l = list(other)
        g = [a for a in l if self._setrecord(a)]
        self.data[i:] = g
    def __delslice__(self, i, j):
        i = max(i, 0); j = max(j, 0)
        for a in self.data[i:j]:
            self._delrecord(a)
        del self.data[i:j]
    def append(self, item): 
        if self._setrecord(item):
            self.data.append(item)
    def insert(self, i, item): 
        if self._setrecord(item):
            self.data.insert(i, item)
    def pop(self, i=-1):
        item = self.data[i]
        if self._delrecord(item):
            return self.data.pop(i)
    def remove(self, item): 
        if self._delrecord(item):
            self.data.remove(item)
    def __add__(self, other):
        raise NotImplementedError()
    def __radd__(self, other):
        raise NotImplementedError()
    def __iadd__(self, other):
        raise NotImplementedError()

        
class ScopedRegistry(object):
    """a Registry that can store one or multiple instances of a single class 
    on a per-application or per-thread scoped basis"""
    def __init__(self, createfunc, defaultscope):
        self.createfunc = createfunc
        self.defaultscope = defaultscope
        self.application = createfunc()
        self.threadlocal = {}
        self.scopes = {
            'application' : {'call' : self._call_application, 'clear' : self._clear_application, 'set':self._set_application}, 
            'thread' : {'call' : self._call_thread, 'clear':self._clear_thread, 'set':self._set_thread}
            }

    def __call__(self, scope = None):
        if scope is None:
            scope = self.defaultscope
        return self.scopes[scope]['call']()

    def set(self, obj, scope = None):
        if scope is None:
            scope = self.defaultscope
        return self.scopes[scope]['set'](obj)
        
    def clear(self, scope = None):
        if scope is None:
            scope = self.defaultscope
        return self.scopes[scope]['clear']()

    def _set_thread(self, obj):
        self.threadlocal[thread.get_ident()] = obj
    
    def _call_thread(self):
        try:
            return self.threadlocal[thread.get_ident()]
        except KeyError:
            return self.threadlocal.setdefault(thread.get_ident(), self.createfunc())

    def _clear_thread(self):
        try:
            del self.threadlocal[thread.get_ident()]
        except KeyError:
            pass

    def _set_application(self, obj):
        self.application = obj
        
    def _call_application(self):
        return self.application

    def _clear_application(self):
        self.application = createfunc()
                


def constructor_args(instance, **kwargs):
    classobj = instance.__class__
        
    argspec = inspect.getargspec(classobj.__init__.im_func)

    argnames = argspec[0] or []
    defaultvalues = argspec[3] or []

    (requiredargs, namedargs) = (
            argnames[0:len(argnames) - len(defaultvalues)], 
            argnames[len(argnames) - len(defaultvalues):]
            )

    newparams = {}

    for arg in requiredargs:
        if arg == 'self': 
            continue
        elif kwargs.has_key(arg):
            newparams[arg] = kwargs[arg]
        else:
            newparams[arg] = getattr(instance, arg)

    for arg in namedargs:
        if kwargs.has_key(arg):
            newparams[arg] = kwargs[arg]
        else:
            if hasattr(instance, arg):
                newparams[arg] = getattr(instance, arg)
            else:
                raise "instance has no attribute '%s'" % arg

    return newparams