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# Authors:
# Pavel Zuna <pzuna@redhat.com>
#
# Copyright (C) 2009 Red Hat
# see file 'COPYING' for use and warranty information
#
# 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 only
#
# 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
"""
This module provides the Encoder base class, that adds encoding/decoding
capabilities to classes extending it. It also defines a set of decorators
designed to automagically encode method arguments and decode their return
values.
"""
class Encoder(object):
"""
Base class implementing encoding python scalar types to strings
and vise-versa.
"""
encode_to = 'utf-8'
encode_none = False
encode_dict_keys = False
encode_dict_keys_postprocess = True
encode_dict_vals = True
encode_dict_vals_postprocess = True
encode_postprocessor = staticmethod(lambda x: x)
decode_from = 'utf-8'
decode_none = False
decode_dict_keys = False
decode_dict_keys_postprocess = True
decode_dict_vals = True
decode_dict_vals_postprocess = True
decode_dict_vals_table = dict()
decode_dict_vals_table_keygen = staticmethod(lambda x: x)
decode_postprocessor = staticmethod(lambda x: x)
def _decode_dict_val(self, key, val):
f = self.decode_dict_vals_table.get(
self.decode_dict_vals_table_keygen(key), self.decode
)
return f(val)
def encode(self, var):
"""
Encode any python built-in python type variable into `self.encode_to`.
Compound types have their individual members encoded.
Returns an encoded copy of 'var'.
"""
if isinstance(var, basestring):
return self.encode_postprocessor(var.encode(self.encode_to))
elif isinstance(var, (bool, float, int, long)):
return self.encode_postprocessor(str(var).encode(self.encode_to))
elif isinstance(var, list):
return [self.encode(m) for m in var]
elif isinstance(var, tuple):
return tuple(self.encode(m) for m in var)
elif isinstance(var, dict):
if self.encode_dict_keys:
dct = dict()
if not self.encode_dict_keys_postprocess:
tmp = self.encode_postprocessor
self.encode_postprocessor = lambda x: x
for (k, v) in var.iteritems():
dct[self.encode(k)] = v
if not self.encode_dict_keys_postprocess:
self.encode_postprocessor = tmp
else:
dct = dict(var)
if self.encode_dict_vals:
if not self.encode_dict_vals_postprocess:
tmp = self.encode_postprocessor
self.encode_postprocessor = lambda x: x
for (k, v) in dct.iteritems():
dct[k] = self.encode(v)
if not self.encode_dict_vals_postprocess:
self.encode_postprocessor = tmp
return dct
elif var is None:
if self.encode_none:
return self.encode_postprocessor(
str(var).encode(self.encode_to)
)
return None
raise TypeError('python built-in type expected, got \'%s\'', type(var))
def decode(self, var):
"""
Decode strings in `self.decode_from` into python strings.
Compound types have their individual members decoded.
Dictionaries can have their values decoded into other types
by looking up keys in `self.decode_dict_vals_table`.
Returns a decoded copy of 'var'.
"""
if isinstance(var, basestring):
return self.decode_postprocessor(var.decode(self.decode_from))
elif isinstance(var, (bool, float, int, long)):
return self.decode_postprocessor(unicode(var))
elif isinstance(var, list):
return [self.decode(m) for m in var]
elif isinstance(var, tuple):
return tuple(self.decode(m) for m in var)
elif isinstance(var, dict):
if self.decode_dict_keys:
dct = dict()
if not self.decode_dict_keys_postprocess:
tmp = self.decode_postprocessor
self.decode_postprocessor = lambda x: x
for (k, v) in var.iteritems():
dct[self.decode(k)] = v
if not self.decode_dict_keys_postprocess:
self.decode_postprocessor = tmp
else:
dct = dict(var)
if self.decode_dict_vals:
if not self.decode_dict_vals_postprocess:
tmp = self.decode_postprocessor
self.decode_postprocessor = lambda x: x
for (k, v) in dct.iteritems():
dct[k] = self._decode_dict_val(k, v)
if not self.decode_dict_vals_postprocess:
self.decode_postprocessor = tmp
return dct
elif var is None:
if self.decode_none:
return self.decode_postprocessor(
str(var).decode(self.decode_from)
)
return None
raise TypeError('python built-in type expected, got \'%s\'', type(var))
## ENCODER METHOD DECORATORS
def encode_args(*outer_args):
"""
Encode arguments of the decorated method specified by their sequence
number or name for keyword arguments.
Example:
class some_class_that_needs_encoding_capabilities(Encoder):
...
@encode_args(1, 3, 'name'):
def some_method(
self, encode_this, dont_encode_this, encode_this_too, **kwargs
):
# if there's going to be a 'name' kwargs it will be encoded
...
This is an Encoder method decorator.
"""
def decorate(f):
def new_f(*args, **kwargs):
assert isinstance(args[0], Encoder), \
'first argument not Encoder instance'
new_args = list(args)
for a in outer_args:
if isinstance(a, int):
new_args[a] = args[0].encode(args[a])
elif isinstance(a, basestring) and a in kwargs:
kwargs[a] = args[0].encode(kwargs[a])
else:
raise TypeError(
'encode_args takes a list of ints and basestrings'
)
return f(*new_args, **kwargs)
new_f.func_name = f.func_name
return new_f
return decorate
def decode_retval():
"""
Decode the return value of the decorated method.
Example:
class some_class_that_needs_encoding_capabilities(Encoder):
...
@decode_retval():
def some_method(self):
...
return this_will_be_decoded
...
This is an Encoder method decorator AND IT HAS TO BE CALLED (use "()")!
"""
def decorate(f):
def new_f(*args, **kwargs):
assert isinstance(args[0], Encoder), \
'first argument not Encoder instance'
return args[0].decode(f(*args, **kwargs))
new_f.func_name = f.func_name
return new_f
return decorate
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