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1"""OpenEmbedded variable typing support
2
3Types are defined in the metadata by name, using the 'type' flag on a
4variable. Other flags may be utilized in the construction of the types. See
5the arguments of the type's factory for details.
6"""
7
8import inspect
9import types
10
11available_types = {}
12
13class MissingFlag(TypeError):
14 """A particular flag is required to construct the type, but has not been
15 provided."""
16 def __init__(self, flag, type):
17 self.flag = flag
18 self.type = type
19 TypeError.__init__(self)
20
21 def __str__(self):
22 return "Type '%s' requires flag '%s'" % (self.type, self.flag)
23
24def factory(var_type):
25 """Return the factory for a specified type."""
26 if var_type is None:
27 raise TypeError("No type specified. Valid types: %s" %
28 ', '.join(available_types))
29 try:
30 return available_types[var_type]
31 except KeyError:
32 raise TypeError("Invalid type '%s':\n Valid types: %s" %
33 (var_type, ', '.join(available_types)))
34
35def create(value, var_type, **flags):
36 """Create an object of the specified type, given the specified flags and
37 string value."""
38 obj = factory(var_type)
39 objflags = {}
40 for flag in obj.flags:
41 if flag not in flags:
42 if flag not in obj.optflags:
43 raise MissingFlag(flag, var_type)
44 else:
45 objflags[flag] = flags[flag]
46
47 return obj(value, **objflags)
48
49def get_callable_args(obj):
50 """Grab all but the first argument of the specified callable, returning
51 the list, as well as a list of which of the arguments have default
52 values."""
53 if type(obj) is type:
54 obj = obj.__init__
55
56 args, varargs, keywords, defaults = inspect.getargspec(obj)
57 flaglist = []
58 if args:
59 if len(args) > 1 and args[0] == 'self':
60 args = args[1:]
61 flaglist.extend(args)
62
63 optional = set()
64 if defaults:
65 optional |= set(flaglist[-len(defaults):])
66 return flaglist, optional
67
68def factory_setup(name, obj):
69 """Prepare a factory for use."""
70 args, optional = get_callable_args(obj)
71 extra_args = args[1:]
72 if extra_args:
73 obj.flags, optional = extra_args, optional
74 obj.optflags = set(optional)
75 else:
76 obj.flags = obj.optflags = ()
77
78 if not hasattr(obj, 'name'):
79 obj.name = name
80
81def register(name, factory):
82 """Register a type, given its name and a factory callable.
83
84 Determines the required and optional flags from the factory's
85 arguments."""
86 factory_setup(name, factory)
87 available_types[factory.name] = factory
88
89
90# Register all our included types
91for name in dir(types):
92 if name.startswith('_'):
93 continue
94
95 obj = getattr(types, name)
96 if not callable(obj):
97 continue
98
99 register(name, obj)