89 lines
2.9 KiB
Python
89 lines
2.9 KiB
Python
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'''
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This module contains helper classes for structure fields and length expressions.
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'''
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class Field(object):
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'''
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Represents a field of a structure.
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type is the datatype object for the field.
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field_type is the name of the type (string tuple)
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field_name is the name of the structure field.
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visible is true iff the field should be in the request API.
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wire is true iff the field should be in the request structure.
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auto is true iff the field is on the wire but not in the request API (e.g. opcode)
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'''
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def __init__(self, type, field_type, field_name, visible, wire, auto):
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self.type = type
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self.field_type = field_type
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self.field_name = field_name
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self.visible = visible
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self.wire = wire
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self.auto = auto
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class Expression(object):
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'''
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Represents a mathematical expression for a list length or exprfield.
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Public fields:
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op is the operation (text +,*,/,<<) or None.
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lhs and rhs are the sub-Expressions if op is set.
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lenfield_name is the name of the length field, or None for request lists.
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lenfield is the Field object for the length field, or None.
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bitfield is True if the length field is a bitmask instead of a number.
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nmemb is the fixed size (value)of the expression, or None
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'''
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def __init__(self, elt, parent):
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self.parent = parent
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self.nmemb = None
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self.lenfield_name = None
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self.lenfield_type = None
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self.lenfield = None
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self.lenwire = False
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self.bitfield = False
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self.op = None
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self.lhs = None
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self.rhs = None
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if elt.tag == 'list':
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# List going into a request, which has no length field (inferred by server)
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self.lenfield_name = elt.get('name') + '_len'
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self.lenfield_type = 'CARD32'
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elif elt.tag == 'fieldref':
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# Standard list with a fieldref
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self.lenfield_name = elt.text
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elif elt.tag == 'valueparam':
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# Value-mask. The length bitmask is described by attributes.
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self.lenfield_name = elt.get('value-mask-name')
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self.lenfield_type = elt.get('value-mask-type')
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self.lenwire = True
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self.bitfield = True
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elif elt.tag == 'op':
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# Op field. Need to recurse.
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self.op = elt.get('op')
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self.lhs = Expression(list(elt)[0], parent)
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self.rhs = Expression(list(elt)[1], parent)
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# Hopefully we don't have two separate length fields...
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self.lenfield_name = self.lhs.lenfield_name
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if self.lenfield_name == None:
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self.lenfield_name = self.rhs.lenfield_name
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elif elt.tag == 'value':
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# Constant expression
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self.nmemb = int(elt.text)
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else:
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# Notreached
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raise Exception('XXX')
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def fixed_size(self):
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return self.nmemb != None
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