Fix the compressed BLFWriter

can/io/blf.py

@@ -11,7 +11,8 @@
 of uncompressed data each. This data contains the actual CAN messages and other
 objects types.
 """
-
+import gzip
+import os
 import struct
 import zlib
 import datetime
@@ -432,7 +433,8 @@ def __init__(
             self.start_timestamp = None
             self.stop_timestamp = None
             # Write a default header which will be updated when stopped
-            self._write_header(FILE_HEADER_SIZE)
+            # Temporarily removed for the sake of GzipFiles
+            # self._write_header(FILE_HEADER_SIZE)
 
     def _write_header(self, filesize):
         header = [b"LOGG", FILE_HEADER_SIZE, self.application_id, 0, 0, 0, 2, 6, 8, 1]
@@ -540,8 +542,9 @@ def _add_object(self, obj_type, data, timestamp=None):
 
         self._buffer_size += obj_size + padding_size
         self.object_count += 1
-        if self._buffer_size >= self.max_container_size:
-            self._flush()
+        # Don't accidentally write to blf file prior to writing header
+        # if self._buffer_size >= self.max_container_size:
+        #     self._flush()
 
     def _flush(self):
         """Compresses and writes data in the buffer to file."""
@@ -582,12 +585,13 @@ def file_size(self) -> int:
 
     def stop(self):
         """Stops logging and closes the file."""
-        self._flush()
         if self.file.seekable():
+            # For a GzipFile, the file currently must be empty prior to writing
+            # this final header, else an OSError will occur
             filesize = self.file.tell()
-            # Write header in the beginning of the file
             self.file.seek(0)
             self._write_header(filesize)
         else:
             LOG.error("Could not write BLF header since file is not seekable")
+        self._flush()
         super().stop()

can/io/logger.py

@@ -88,7 +88,7 @@ def __new__(  # type: ignore
 
         file_or_filename: AcceptedIOType = filename
         if suffix == ".gz":
-            suffix, file_or_filename = Logger.compress(filename)
+            suffix, file_or_filename = Logger.compress(filename, *args, **kwargs)
 
         try:
             return Logger.message_writers[suffix](file_or_filename, *args, **kwargs)
@@ -98,13 +98,18 @@ def __new__(  # type: ignore
             ) from None
 
     @staticmethod
-    def compress(filename: StringPathLike) -> Tuple[str, FileLike]:
+    def compress(
+        filename: StringPathLike, *args: Any, **kwargs: Any
+    ) -> Tuple[str, FileLike]:
         """
         Return the suffix and io object of the decompressed file.
         File will automatically recompress upon close.
         """
         real_suffix = pathlib.Path(filename).suffixes[-2].lower()
-        mode = "ab" if real_suffix == ".blf" else "at"
+        if kwargs.get("append", False):
+            mode = "ab" if real_suffix == ".blf" else "at"
+        else:
+            mode = "wb" if real_suffix == ".blf" else "wt"
 
         return real_suffix, gzip.open(filename, mode)
 
@@ -344,12 +349,14 @@ def do_rollover(self) -> None:
     def _default_name(self) -> StringPathLike:
         """Generate the default rotation filename."""
         path = pathlib.Path(self.base_filename)
+        stem = path.parts[-1].split(".")[0]
+        suffix = "".join(pathlib.Path(self.base_filename).suffixes[-2:])
         new_name = (
-            path.stem
+            stem
             + "_"
             + datetime.now().strftime("%Y-%m-%dT%H%M%S")
             + "_"
             + f"#{self.rollover_count:03}"
-            + path.suffix
+            + suffix
         )
         return str(path.parent / new_name)