100 lines
2.8 KiB
Python
100 lines
2.8 KiB
Python
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"""OpenEmbedded variable typing support
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Types are defined in the metadata by name, using the 'type' flag on a
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variable. Other flags may be utilized in the construction of the types. See
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the arguments of the type's factory for details.
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"""
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import inspect
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import types
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available_types = {}
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class MissingFlag(TypeError):
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"""A particular flag is required to construct the type, but has not been
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provided."""
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def __init__(self, flag, type):
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self.flag = flag
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self.type = type
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TypeError.__init__(self)
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def __str__(self):
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return "Type '%s' requires flag '%s'" % (self.type, self.flag)
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def factory(var_type):
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"""Return the factory for a specified type."""
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if var_type is None:
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raise TypeError("No type specified. Valid types: %s" %
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', '.join(available_types))
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try:
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return available_types[var_type]
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except KeyError:
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raise TypeError("Invalid type '%s':\n Valid types: %s" %
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(var_type, ', '.join(available_types)))
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def create(value, var_type, **flags):
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"""Create an object of the specified type, given the specified flags and
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string value."""
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obj = factory(var_type)
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objflags = {}
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for flag in obj.flags:
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if flag not in flags:
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if flag not in obj.optflags:
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raise MissingFlag(flag, var_type)
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else:
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objflags[flag] = flags[flag]
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return obj(value, **objflags)
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def get_callable_args(obj):
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"""Grab all but the first argument of the specified callable, returning
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the list, as well as a list of which of the arguments have default
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values."""
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if type(obj) is type:
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obj = obj.__init__
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args, varargs, keywords, defaults = inspect.getargspec(obj)
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flaglist = []
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if args:
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if len(args) > 1 and args[0] == 'self':
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args = args[1:]
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flaglist.extend(args)
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optional = set()
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if defaults:
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optional |= set(flaglist[-len(defaults):])
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return flaglist, optional
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def factory_setup(name, obj):
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"""Prepare a factory for use."""
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args, optional = get_callable_args(obj)
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extra_args = args[1:]
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if extra_args:
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obj.flags, optional = extra_args, optional
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obj.optflags = set(optional)
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else:
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obj.flags = obj.optflags = ()
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if not hasattr(obj, 'name'):
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obj.name = name
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def register(name, factory):
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"""Register a type, given its name and a factory callable.
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Determines the required and optional flags from the factory's
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arguments."""
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factory_setup(name, factory)
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available_types[factory.name] = factory
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# Register all our included types
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for name in dir(types):
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if name.startswith('_'):
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continue
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obj = getattr(types, name)
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if not callable(obj):
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continue
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register(name, obj)
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