def variant_accessor_functions(field: Field, variant_id: str,
variant: Variant) -> List[Subprogram]:
first_byte, last_byte, offset = field_location(field.name, variant_id,
variant)
name = f'Get_{field.name}_{variant_id}'
precondition = Precondition(
And(COMMON_PRECONDITION,
LogCall(f'Valid_{field.name}_{variant_id} (Buffer)')))
functions: List[Subprogram] = []
if isinstance(field.type, Array):
functions.append(
ExpressionFunction(f'{name}_First', 'Types.Index_Type',
[('Buffer', 'Types.Bytes')], first_byte,
[precondition]))
functions.append(
ExpressionFunction(f'{name}_Last', 'Types.Index_Type',
[('Buffer', 'Types.Bytes')], last_byte,
[precondition]))
else:
functions.append(
ExpressionFunction(
name, field.type.name, [('Buffer', 'Types.Bytes')],
Convert(
field.type.name if field.type.constraints == TRUE else
field.type.base_name, 'Buffer', first_byte, last_byte,
offset), [precondition]))
return functions
def enumeration_functions(enum: Enumeration) -> List[Subprogram]:
common_precondition = And(
Less(Value('Offset'), Number(8)),
Equal(
Length('Buffer'),
Add(
Div(Add(Size(enum.base_name), Value('Offset'), Number(-1)),
Number(8)), Number(1))))
control_expression = LogCall(
f'Convert_To_{enum.base_name} (Buffer, Offset)')
validation_expression: Expr
if enum.always_valid:
validation_expression = Value('True')
else:
validation_cases: List[Tuple[Expr, Expr]] = []
validation_cases.extend(
(value, Value('True')) for value in enum.literals.values())
validation_cases.append((Value('others'), Value('False')))
validation_expression = CaseExpression(control_expression,
validation_cases)
validation_function = ExpressionFunction(
f'Valid_{enum.name}', 'Boolean', [('Buffer', 'Types.Bytes'),
('Offset', 'Natural')],
validation_expression, [Precondition(common_precondition)])
function_name = f'Convert_To_{enum.name}'
parameters = [('Buffer', 'Types.Bytes'), ('Offset', 'Natural')]
precondition = Precondition(
And(common_precondition,
LogCall(f'Valid_{enum.name} (Buffer, Offset)')))
conversion_cases: List[Tuple[Expr, Expr]] = []
conversion_function: Subprogram
if enum.always_valid:
conversion_cases.extend((value, Aggregate(Value('True'), Value(key)))
for key, value in enum.literals.items())
conversion_cases.append(
(Value('others'), Aggregate(Value('False'), Value('Raw'))))
conversion_function = Function(
function_name, enum.name, parameters,
[Declaration('Raw', enum.base_name, control_expression)],
[ReturnStatement(CaseExpression(Value('Raw'), conversion_cases))],
[precondition])
else:
conversion_cases.extend(
(value, Value(key)) for key, value in enum.literals.items())
conversion_cases.append(
(Value('others'), LogCall(f'Unreachable_{enum.name}')))
conversion_function = ExpressionFunction(
function_name, enum.name, parameters,
CaseExpression(control_expression, conversion_cases),
[precondition])
return [validation_function, conversion_function]
def field_accessor_functions(field: Field,
package_name: str) -> List[Subprogram]:
precondition = Precondition(
And(COMMON_PRECONDITION, LogCall(f'Valid_{field.name} (Buffer)')))
functions: List[Subprogram] = []
if isinstance(field.type, Array):
for attribute in ['First', 'Last']:
functions.append(
ExpressionFunction(
f'Get_{field.name}_{attribute}', 'Types.Index_Type',
[('Buffer', 'Types.Bytes')],
IfExpression([(
LogCall(f'Valid_{field.name}_{variant_id} (Buffer)'),
LogCall(
f'Get_{field.name}_{variant_id}_{attribute} (Buffer)'
)) for variant_id in field.variants],
'Unreachable_Types_Index_Type'),
[precondition]))
body: List[Statement] = [
Assignment('First', MathCall(f'Get_{field.name}_First (Buffer)')),
Assignment('Last', MathCall(f'Get_{field.name}_Last (Buffer)'))
]
postcondition = Postcondition(
And(
Equal(Value('First'),
MathCall(f'Get_{field.name}_First (Buffer)')),
Equal(Value('Last'),
MathCall(f'Get_{field.name}_Last (Buffer)'))))
if 'Payload' not in field.type.name:
predicate = f'{package_name}.{field.type.name}.Is_Contained (Buffer (First .. Last))'
body.append(PragmaStatement('Assume', [predicate]))
postcondition.expr = And(postcondition.expr, LogCall(predicate))
functions.append(
Procedure(f'Get_{field.name}', [('Buffer', 'Types.Bytes'),
('First', 'out Types.Index_Type'),
('Last', 'out Types.Index_Type')],
[], body, [precondition, postcondition]))
else:
functions.append(
ExpressionFunction(
f'Get_{field.name}', field.type.name,
[('Buffer', 'Types.Bytes')],
IfExpression(
[(LogCall(f'Valid_{field.name}_{variant_id} (Buffer)'),
MathCall(f'Get_{field.name}_{variant_id} (Buffer)'))
for variant_id in field.variants],
f'Unreachable_{field.type.name}'), [precondition]))
return functions
def contain_functions() -> List[Subprogram]:
return [
ExpressionFunction('Is_Contained',
'Boolean', [('Buffer', 'Types.Bytes')],
aspects=[Ghost(), Import()]),
Procedure('Label', [('Buffer', 'Types.Bytes')], [],
[PragmaStatement('Assume', ['Is_Contained (Buffer)'])],
aspects=[Postcondition(LogCall('Is_Contained (Buffer)'))])
]
def message_validation_function(variants: List[Variant]) -> Subprogram:
expr: LogExpr = FALSE
for variant in variants:
condition = variant_condition(variant)
expr = condition if expr == FALSE else Or(expr, condition)
return ExpressionFunction('Is_Valid', 'Boolean',
[('Buffer', 'Types.Bytes')], expr,
[Precondition(COMMON_PRECONDITION)])
def field_validation_function(field: Field) -> Subprogram:
variants: List[LogExpr] = list(valid_variants(field))
expr = variants.pop()
for e in variants:
if e is not TRUE:
expr = Or(expr, e)
return ExpressionFunction(f'Valid_{field.name}', 'Boolean',
[('Buffer', 'Types.Bytes')], expr,
[Precondition(COMMON_PRECONDITION)])
def message_length_function(variants: List[Variant]) -> Subprogram:
condition_expressions: List[Tuple[LogExpr, Expr]] = []
for variant in variants:
condition = variant_condition(variant)
length = Add(
Last(variant.previous[-1][0]), -First(variant.previous[0][0]),
Number(1)).simplified(variant.facts).simplified(
value_to_call_facts(variant.previous)).to_bytes().simplified()
condition_expressions.append((condition, length))
return ExpressionFunction(
'Message_Length', 'Types.Length_Type', [('Buffer', 'Types.Bytes')],
IfExpression(condition_expressions, 'Unreachable_Types_Length_Type'),
[Precondition(And(COMMON_PRECONDITION, LogCall('Is_Valid (Buffer)')))])
def variant_validation_function(field: Field, variant_id: str,
variant: Variant) -> Subprogram:
type_constraints: LogExpr = TRUE
if field.type.constraints != TRUE or isinstance(field.type, Enumeration):
first_byte, last_byte, offset = field_location(field.name, variant_id,
variant)
if field.type.constraints != TRUE:
convert = Convert(field.type.base_name, 'Buffer', first_byte,
last_byte, offset)
type_constraints = field.type.constraints.simplified(
{Value(field.type.name): convert})
if isinstance(field.type, Enumeration):
type_constraints = And(
type_constraints,
LogCall((f'Valid_{field.type.name} (Buffer ({first_byte}'
f' .. {last_byte}), {offset})')))
value_to_call = value_to_call_facts([(field.name, variant_id)] +
variant.previous)
return ExpressionFunction(
f'Valid_{field.name}_{variant_id}', 'Boolean',
[('Buffer', 'Types.Bytes')],
And(
LogCall(
f'Valid_{variant.previous[-1][0]}_{variant.previous[-1][1]} (Buffer)'
) if variant.previous else TRUE,
And(
And(
buffer_constraints(variant.facts[Last(
field.name)].to_bytes()).simplified(value_to_call),
variant.condition.simplified(
variant.facts).simplified(value_to_call)),
type_constraints)).simplified(),
[Precondition(COMMON_PRECONDITION)])
def unreachable_function(type_name: str, base_name: str = None) -> Subprogram:
return ExpressionFunction(
f'Unreachable_{type_name}'.replace('.', '_'), type_name, [],
First(type_name) if not base_name else Aggregate(
Value('False'), First(base_name)), [Precondition(FALSE)])