pw_log_tokenized: Update Python Metadata fields - Update the field order in pw_log_tokenized.Metadata to match the order in C++ (level, line, flags, module). - Update the pw_log_tokenized.Metadata class and add tests. Change-Id: I6c7ecdad94bc7d55bde11731958cef76ff2e648c Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/48361 Reviewed-by: Keir Mierle <keir@google.com> Commit-Queue: Wyatt Hepler <hepler@google.com>

diff --git a/pw_log_tokenized/py/BUILD.gn b/pw_log_tokenized/py/BUILD.gn
index 6c66e61..54ad83b 100644
--- a/pw_log_tokenized/py/BUILD.gn
+++ b/pw_log_tokenized/py/BUILD.gn

@@ -19,6 +19,9 @@
 pw_python_package("py") {
   setup = [ "setup.py" ]
   sources = [ "pw_log_tokenized/__init__.py" ]
-  tests = [ "format_string_test.py" ]
+  tests = [
+    "format_string_test.py",
+    "metadata_test.py",
+  ]
   pylintrc = "$dir_pigweed/.pylintrc"
 }

diff --git a/pw_log_tokenized/py/format_string_test.py b/pw_log_tokenized/py/format_string_test.py
index b20c6a0..af49bf2 100644
--- a/pw_log_tokenized/py/format_string_test.py
+++ b/pw_log_tokenized/py/format_string_test.py

@@ -19,8 +19,8 @@
 from pw_log_tokenized import FormatStringWithMetadata
 
 
-class TestDecodeTokenized(unittest.TestCase):
-    """Tests decoding tokenized strings with various arguments."""
+class TestFormatStringWithMetadata(unittest.TestCase):
+    """Tests extracting metadata from a pw_log_tokenized-style format string."""
     def test_all_fields(self):
         log = FormatStringWithMetadata(
             '■msg♦hello %d■file♦__FILE__■module♦log module name!')

diff --git a/pw_log_tokenized/py/metadata_test.py b/pw_log_tokenized/py/metadata_test.py
new file mode 100644
index 0000000..1073a92
--- /dev/null
+++ b/pw_log_tokenized/py/metadata_test.py

@@ -0,0 +1,54 @@
+# Copyright 2021 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+"""Tests for the pw_log_tokenized packed metadata class."""
+
+import unittest
+
+from pw_log_tokenized import Metadata
+
+
+class TestMetadata(unittest.TestCase):
+    """Tests extracting fields from a pw_log_tokenized packed metadata value."""
+    def test_zero(self):
+        metadata = Metadata(0)
+        self.assertEqual(metadata.log_level, 0)
+        self.assertEqual(metadata.line, 0)
+        self.assertEqual(metadata.flags, 0)
+        self.assertEqual(metadata.module_token, 0)
+
+    def test_various(self):
+        metadata = Metadata(0xABCD << 16 | 1 << 14 | 1234 << 3 | 5,
+                            log_bits=3,
+                            line_bits=11,
+                            flag_bits=2,
+                            module_bits=16)
+        self.assertEqual(metadata.log_level, 5)
+        self.assertEqual(metadata.line, 1234)
+        self.assertEqual(metadata.flags, 1)
+        self.assertEqual(metadata.module_token, 0xABCD)
+
+    def test_max(self):
+        metadata = Metadata(0xFFFFFFFF,
+                            log_bits=3,
+                            line_bits=11,
+                            flag_bits=2,
+                            module_bits=16)
+        self.assertEqual(metadata.log_level, 7)
+        self.assertEqual(metadata.line, 2047)
+        self.assertEqual(metadata.flags, 3)
+        self.assertEqual(metadata.module_token, 0xFFFF)
+
+
+if __name__ == '__main__':
+    unittest.main()

diff --git a/pw_log_tokenized/py/pw_log_tokenized/__init__.py b/pw_log_tokenized/py/pw_log_tokenized/__init__.py
index 3e1768b..d0cc1d1 100644
--- a/pw_log_tokenized/py/pw_log_tokenized/__init__.py
+++ b/pw_log_tokenized/py/pw_log_tokenized/__init__.py

@@ -23,30 +23,29 @@
     return (value & (mask << start)) >> start
 
 
-@dataclass(frozen=True)
 class Metadata:
     """Parses the metadata payload used by pw_log_tokenized."""
-    _value: int
+    def __init__(self,
+                 value: int,
+                 *,
+                 log_bits: int = 3,
+                 line_bits: int = 11,
+                 flag_bits: int = 2,
+                 module_bits: int = 16) -> None:
+        self.value = value
 
-    log_bits: int = 3
-    module_bits: int = 16
-    flag_bits: int = 2
-    line_bits: int = 11
+        self.log_level = _mask(value, 0, log_bits)
+        self.line = _mask(value, log_bits, line_bits)
+        self.flags = _mask(value, log_bits + line_bits, flag_bits)
+        self.module_token = _mask(value, log_bits + line_bits + flag_bits,
+                                  module_bits)
 
-    def log_level(self) -> int:
-        return _mask(self._value, 0, self.log_bits)
-
-    def module_token(self) -> int:
-        return _mask(self._value, self.log_bits, self.module_bits)
-
-    def flags(self) -> int:
-        return _mask(self._value, self.log_bits + self.module_bits,
-                     self.flag_bits)
-
-    def line(self) -> int:
-        return _mask(self._value,
-                     self.log_bits + self.module_bits + self.flag_bits,
-                     self.line_bits)
+    def __repr__(self) -> str:
+        return (f'{type(self).__name__}('
+                f'log_level={self.log_level}, '
+                f'line={self.line}, '
+                f'flags={self.flags}, '
+                f'module_token={self.module_token})')
 
 
 class FormatStringWithMetadata: