utils/revent: Added revent recording parser

revent binary recordings can now be parsed and used within WA.

wlauto/utils/revent.py

@@ -0,0 +1,78 @@
+#    Copyright 2016 ARM Limited
+#
+# 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
+#
+#     http://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.
+#
+
+import struct
+import datetime
+import os
+
+
+class ReventParser(object):
+    """
+    Parses revent binary recording files so they can be easily read within python.
+    """
+
+    int32_struct = struct.Struct("<i")
+    header_struct = struct.Struct("<6sH")
+    event_struct = struct.Struct("<i4xqqHHi")
+
+    def __init__(self):
+        self.path = None
+        self.device_paths = []
+
+    def parse(self, path):
+        ReventParser.check_revent_file(path)
+
+        with open(path, "rb") as f:
+            _read_struct(f, ReventParser.header_struct)
+            path_count, = _read_struct(f, self.int32_struct)
+            for _ in xrange(path_count):
+                path_length, = _read_struct(f, self.int32_struct)
+                if path_length >= 30:
+                    raise ValueError("path length too long. corrupt file")
+                self.device_paths.append(f.read(path_length))
+
+            while f.tell() < os.path.getsize(path):
+                device_id, sec, usec, typ, code, value = _read_struct(f, self.event_struct)
+                yield (device_id, datetime.datetime.fromtimestamp(sec + float(usec) / 1000000),
+                       typ, code, value)
+
+    @staticmethod
+    def check_revent_file(path):
+        """
+        Checks whether a file starts with "REVENT"
+        """
+        with open(path, "rb") as f:
+            magic, file_version = _read_struct(f, ReventParser.header_struct)
+
+            if magic != "REVENT":
+                msg = "'{}' isn't an revent file, are you using an old recording?"
+                raise ValueError(msg.format(path))
+            return file_version
+
+    @staticmethod
+    def get_revent_duration(path):
+        """
+        Takes an ReventParser and returns the duration of the revent recording in seconds.
+        """
+        revent_parser = ReventParser().parse(path)
+        first = last = next(revent_parser)
+        for last in revent_parser:
+            pass
+        return (last[1] - first[1]).total_seconds()
+
+
+def _read_struct(f, struct_spec):
+    data = f.read(struct_spec.size)
+    return struct_spec.unpack(data)