def test_nested():
s = Struct(
'a' / Byte, 'b' / DeferredValue(Byte), 'c' / Byte, 'struct' /
Struct('new_value' / Tell,
WriteDeferredValue(this.new_value + 7, this._.b), 'x' / Byte))
# parsing
assert s.parse(b'\x01\x02\x03\x04') == {
'a': 1,
'b': 2,
'c': 3,
'struct': {
'new_value': 3,
'x': 4
}
}
# building
assert s.build({
'a': 0xff,
'c': 0xfe,
'struct': {
'x': 0x42
}
}) == b'\xff\x0a\xfe\x42'
def test_single():
s = Struct('a' / Byte, 'b' / DeferredValue(Byte), 'c' / Byte,
'new_value' / Tell, WriteDeferredValue(this.new_value, this.b))
# parsing
assert s.parse(b'\x01\x02\x03') == {'a': 1, 'b': 2, 'c': 3, 'new_value': 3}
# building
assert s.build({'a': 0xff, 'c': 0xfe}) == b'\xff\x03\xfe'
def test_unexpected_placeholder():
def _change_placeholder(context):
stream = context._io
placeholder = context.a.placeholder_data[0]
stream.seek(-1, os.SEEK_CUR)
stream.write(bytes([(placeholder + 1) & 0xff]))
s = Struct(
'a' / DeferredValue(Byte),
Computed(
_change_placeholder
), # overwrites placeholder with different value, should fail sanity check later
WriteDeferredValue(0x42, this.a))
with pytest.raises(DeferredError):
s.build({})
def test_complex_prefixed():
s = Struct(
'v' / Byte,
'a1' / Prefixed(Byte, Array(2, Struct('value' / DeferredValue(Byte)))),
'a2' / Array(
2,
Struct(
'@offset' / Tell,
WriteDeferredValue(this['@offset'],
lambda this: this._.a1[this._index].value),
'value' / Byte)))
# parsing
assert s.parse(b'\xff\x02\x41\x42\xe0\xe1') == {
'v': 0xff,
'a1': [{
'value': 0x41
}, {
'value': 0x42
}],
'a2': [{
'@offset': 4,
'value': 0xe0
}, {
'@offset': 5,
'value': 0xe1
}]
}
# building
assert s.build({
'v': 0xff,
'a1': [{}, {}],
'a2': [{
'value': 0xe0
}, {
'value': 0xe1
}]
}) == b'\xff\x02\x04\x05\xe0\xe1'
def test_constant_size():
with pytest.raises(DeferredError) as e:
DeferredValue(GreedyBytes)
assert isinstance(e.value.__context__, SizeofError)
def test_placeholder():
assert len(DeferredValue(Byte).build(None)) == 1
def test_check_deferred():
s = Struct('a' / DeferredValue(Byte), CheckDeferredValues)
with pytest.raises(DeferredError):
s.build({})
def test_write_twice():
s = Struct('a' / DeferredValue(Byte), WriteDeferredValue(0x41, this.a),
WriteDeferredValue(0x42, this.a))
with pytest.raises(DeferredError):
s.build({})
def test_build_no_value():
s = Struct('a' / DeferredValue(Byte), WriteDeferredValue(0x42, this.a))
with pytest.raises(DeferredError):
s.build({'a': 0xab})