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