Compact data type ID per https://forum.uavcan.org/t/alternative-trans…

…port-protocols/324
OpenCyphal · May 21, 2019 · ead3f68 · ead3f68
1 parent 28e0fe8
commit ead3f68
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Showing 2 changed files with 98 additions and 3 deletions.
diff --git a/pydsdl/__init__.py b/pydsdl/__init__.py
@@ -32,7 +32,7 @@
           file=_sys.stderr)
     _sys.exit(1)
 
-__version__ = 0, 9, 1
+__version__ = 0, 9, 2
 __license__ = 'MIT'
 
 # Our unorthodox approach to dependency management requires us to apply certain workarounds.

diff --git a/pydsdl/_serializable/_composite.py b/pydsdl/_serializable/_composite.py
@@ -193,6 +193,34 @@ def source_file_path(self) -> str:
         """Empty if this is a synthesized type, e.g. a service request or response section."""
         return self._source_file_path
 
+    @property
+    def compact_data_type_id(self) -> int:
+        """
+        WARNING: THIS API ENTITY IS UNSTABLE AND IS NOT PART OF THE UAVCAN SPECIFICATION v1.0.
+        See the context here: https://forum.uavcan.org/t/alternative-transport-protocols/324
+        """
+        salt = 'cvo0'
+
+        def get_hash(data: str) -> int:
+            c = CRC32C()
+            c.add((data + salt).encode())
+            return c.value
+
+        full_name_except_root_ns = self.NAME_COMPONENT_SEPARATOR.join(self.name_components[1:])
+        assert self.root_namespace + self.NAME_COMPONENT_SEPARATOR + full_name_except_root_ns == self.full_name
+
+        # Field assignment:
+        #   - Upper 32 bits contain the CRC32C of the root namespace salted with "cvo0"
+        #   - The bits [8, 31] (i.e., the next 24 bits) contain the 24 most significant bits of the CRC32C of the
+        #     full name excepting the root namespace and its separator. For example, that would be "node.Heartbeat"
+        #     of "uavcan.node.Heartbeat".
+        #   - The 8 least significant bits contain the major version number.
+        out = (get_hash(self.root_namespace) << 32) \
+            | (get_hash(full_name_except_root_ns) & 0xFFFFFF00) \
+            | self.version.major
+        assert 0 <= out < 2 ** 64
+        return out
+
     @property
     def parent_service(self) -> typing.Optional['ServiceType']:
         """
@@ -477,8 +505,8 @@ def try_name(name: str) -> CompositeType:
                   fixed_port_id=None,
                   source_file_path='')
 
-    u = UnionType(name='a.A',
-                  version=Version(0, 1),
+    u = UnionType(name='uavcan.node.Heartbeat',
+                  version=Version(42, 123),
                   attributes=[
                       Field(UnsignedIntegerType(16, PrimitiveType.CastMode.TRUNCATED), 'a'),
                       Field(SignedIntegerType(16, PrimitiveType.CastMode.SATURATED), 'b'),
@@ -487,6 +515,7 @@ def try_name(name: str) -> CompositeType:
                   deprecated=False,
                   fixed_port_id=None,
                   source_file_path='')
+    assert u.compact_data_type_id == 0x666666667bc4992a     # Computed by hand
     assert u['a'].name == 'a'
     assert u['b'].name == 'b'
     assert u['A'].name == 'A'
@@ -743,3 +772,69 @@ def validate_iterator(t: CompositeType,
                     deprecated=False,
                     fixed_port_id=None,
                     source_file_path='').iterate_fields_with_offsets()
+
+
+class CRC32C:
+    """
+    Implementation of the CRC-32C (Castagnoli) algorithm.
+    """
+
+    _CRC32C_TABLE = [
+        0x00000000, 0xF26B8303, 0xE13B70F7, 0x1350F3F4, 0xC79A971F, 0x35F1141C, 0x26A1E7E8, 0xD4CA64EB, 0x8AD958CF,
+        0x78B2DBCC, 0x6BE22838, 0x9989AB3B, 0x4D43CFD0, 0xBF284CD3, 0xAC78BF27, 0x5E133C24, 0x105EC76F, 0xE235446C,
+        0xF165B798, 0x030E349B, 0xD7C45070, 0x25AFD373, 0x36FF2087, 0xC494A384, 0x9A879FA0, 0x68EC1CA3, 0x7BBCEF57,
+        0x89D76C54, 0x5D1D08BF, 0xAF768BBC, 0xBC267848, 0x4E4DFB4B, 0x20BD8EDE, 0xD2D60DDD, 0xC186FE29, 0x33ED7D2A,
+        0xE72719C1, 0x154C9AC2, 0x061C6936, 0xF477EA35, 0xAA64D611, 0x580F5512, 0x4B5FA6E6, 0xB93425E5, 0x6DFE410E,
+        0x9F95C20D, 0x8CC531F9, 0x7EAEB2FA, 0x30E349B1, 0xC288CAB2, 0xD1D83946, 0x23B3BA45, 0xF779DEAE, 0x05125DAD,
+        0x1642AE59, 0xE4292D5A, 0xBA3A117E, 0x4851927D, 0x5B016189, 0xA96AE28A, 0x7DA08661, 0x8FCB0562, 0x9C9BF696,
+        0x6EF07595, 0x417B1DBC, 0xB3109EBF, 0xA0406D4B, 0x522BEE48, 0x86E18AA3, 0x748A09A0, 0x67DAFA54, 0x95B17957,
+        0xCBA24573, 0x39C9C670, 0x2A993584, 0xD8F2B687, 0x0C38D26C, 0xFE53516F, 0xED03A29B, 0x1F682198, 0x5125DAD3,
+        0xA34E59D0, 0xB01EAA24, 0x42752927, 0x96BF4DCC, 0x64D4CECF, 0x77843D3B, 0x85EFBE38, 0xDBFC821C, 0x2997011F,
+        0x3AC7F2EB, 0xC8AC71E8, 0x1C661503, 0xEE0D9600, 0xFD5D65F4, 0x0F36E6F7, 0x61C69362, 0x93AD1061, 0x80FDE395,
+        0x72966096, 0xA65C047D, 0x5437877E, 0x4767748A, 0xB50CF789, 0xEB1FCBAD, 0x197448AE, 0x0A24BB5A, 0xF84F3859,
+        0x2C855CB2, 0xDEEEDFB1, 0xCDBE2C45, 0x3FD5AF46, 0x7198540D, 0x83F3D70E, 0x90A324FA, 0x62C8A7F9, 0xB602C312,
+        0x44694011, 0x5739B3E5, 0xA55230E6, 0xFB410CC2, 0x092A8FC1, 0x1A7A7C35, 0xE811FF36, 0x3CDB9BDD, 0xCEB018DE,
+        0xDDE0EB2A, 0x2F8B6829, 0x82F63B78, 0x709DB87B, 0x63CD4B8F, 0x91A6C88C, 0x456CAC67, 0xB7072F64, 0xA457DC90,
+        0x563C5F93, 0x082F63B7, 0xFA44E0B4, 0xE9141340, 0x1B7F9043, 0xCFB5F4A8, 0x3DDE77AB, 0x2E8E845F, 0xDCE5075C,
+        0x92A8FC17, 0x60C37F14, 0x73938CE0, 0x81F80FE3, 0x55326B08, 0xA759E80B, 0xB4091BFF, 0x466298FC, 0x1871A4D8,
+        0xEA1A27DB, 0xF94AD42F, 0x0B21572C, 0xDFEB33C7, 0x2D80B0C4, 0x3ED04330, 0xCCBBC033, 0xA24BB5A6, 0x502036A5,
+        0x4370C551, 0xB11B4652, 0x65D122B9, 0x97BAA1BA, 0x84EA524E, 0x7681D14D, 0x2892ED69, 0xDAF96E6A, 0xC9A99D9E,
+        0x3BC21E9D, 0xEF087A76, 0x1D63F975, 0x0E330A81, 0xFC588982, 0xB21572C9, 0x407EF1CA, 0x532E023E, 0xA145813D,
+        0x758FE5D6, 0x87E466D5, 0x94B49521, 0x66DF1622, 0x38CC2A06, 0xCAA7A905, 0xD9F75AF1, 0x2B9CD9F2, 0xFF56BD19,
+        0x0D3D3E1A, 0x1E6DCDEE, 0xEC064EED, 0xC38D26C4, 0x31E6A5C7, 0x22B65633, 0xD0DDD530, 0x0417B1DB, 0xF67C32D8,
+        0xE52CC12C, 0x1747422F, 0x49547E0B, 0xBB3FFD08, 0xA86F0EFC, 0x5A048DFF, 0x8ECEE914, 0x7CA56A17, 0x6FF599E3,
+        0x9D9E1AE0, 0xD3D3E1AB, 0x21B862A8, 0x32E8915C, 0xC083125F, 0x144976B4, 0xE622F5B7, 0xF5720643, 0x07198540,
+        0x590AB964, 0xAB613A67, 0xB831C993, 0x4A5A4A90, 0x9E902E7B, 0x6CFBAD78, 0x7FAB5E8C, 0x8DC0DD8F, 0xE330A81A,
+        0x115B2B19, 0x020BD8ED, 0xF0605BEE, 0x24AA3F05, 0xD6C1BC06, 0xC5914FF2, 0x37FACCF1, 0x69E9F0D5, 0x9B8273D6,
+        0x88D28022, 0x7AB90321, 0xAE7367CA, 0x5C18E4C9, 0x4F48173D, 0xBD23943E, 0xF36E6F75, 0x0105EC76, 0x12551F82,
+        0xE03E9C81, 0x34F4F86A, 0xC69F7B69, 0xD5CF889D, 0x27A40B9E, 0x79B737BA, 0x8BDCB4B9, 0x988C474D, 0x6AE7C44E,
+        0xBE2DA0A5, 0x4C4623A6, 0x5F16D052, 0xAD7D5351,
+    ]
+
+    def __init__(self) -> None:
+        assert len(self._CRC32C_TABLE) == 256
+        self._value = 0xFFFFFFFF
+
+    def add(self, data: typing.Union[bytes, bytearray]) -> None:
+        for b in data:
+            self._value = self._CRC32C_TABLE[b ^ (self._value & 0xFF)] ^ (self._value >> 8)
+
+    @property
+    def value(self) -> int:
+        assert 0 <= self._value <= 0xFFFFFFFF
+        return self._value ^ 0xFFFFFFFF
+
+
+def _unittest_crc32c() -> None:
+    c = CRC32C()
+    assert c.value == 0
+    c.add(b'')
+    assert c.value == 0
+    c.add(b'123456789')
+    assert c.value == 0xE3069283
+    c.add(b'')
+    assert c.value == 0xE3069283
+
+    c = CRC32C()
+    c.add(b'uavcan' + b'cvo0')
+    assert c.value == 0x66666666