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Add APP_TEXT object type to BLFReader #1942

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Add APP_TEXT object type to BLFReader #1942

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be8103d
Add metadata object type
jonmon6691 May 27, 2025
38ffc7c
Change metadata to app_text
jonmon6691 May 28, 2025
84f55bf
Fix type annotation
jonmon6691 May 28, 2025
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29 changes: 28 additions & 1 deletion can/io/blf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -77,9 +77,13 @@ class BLFParseError(Exception):
# group name length, marker name length, description length
GLOBAL_MARKER_STRUCT = struct.Struct("<LLL3xBLLL12x")

# APP_TEXT object type, 4 reserved bytes, text length, 4 more
# reserved bytes
APP_TEXT_HEADER_STRUCT = struct.Struct("<I4sI4s")

CAN_MESSAGE = 1
LOG_CONTAINER = 10
APP_TEXT = 65
CAN_ERROR_EXT = 73
CAN_MESSAGE2 = 86
GLOBAL_MARKER = 96
Expand Down Expand Up @@ -142,7 +146,12 @@ class BLFReader(BinaryIOMessageReader):
Iterator of CAN messages from a Binary Logging File.

Only CAN messages and error frames are supported. Other object types are
silently ignored.
silently ignored. APP_TEXT objects are parsed into `self.app_text` when
they are encountered while iterating.

self.app_text is a list of tuples containing the parsed app_text objects. The
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Take a look at the sphinx documention on how to properly document instance attributes.

interpretation of this data is context-specific and out of scope of the
BLFReader class.
"""

file: BinaryIO
Expand Down Expand Up @@ -173,6 +182,11 @@ def __init__(
)
# Read rest of header
self.file.read(header[1] - FILE_HEADER_STRUCT.size)

# APP_TEXT objects are appended when type 65 is encountered
# while iterating
self.app_text: List[Tuple] = []
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Instead of a tuple, i'd prefer an AppText or BlfAppText dataclass with timestamp, source and text attributes.


self._tail = b""
self._pos = 0

Expand Down Expand Up @@ -230,6 +244,8 @@ def _parse_data(self, data):
unpack_can_fd_64_msg = CAN_FD_MSG_64_STRUCT.unpack_from
can_fd_64_msg_size = CAN_FD_MSG_64_STRUCT.size
unpack_can_error_ext = CAN_ERROR_EXT_STRUCT.unpack_from
app_text_header = APP_TEXT_HEADER_STRUCT.unpack_from
app_text_header_size = APP_TEXT_HEADER_STRUCT.size

start_timestamp = self.start_timestamp
max_pos = len(data)
Expand Down Expand Up @@ -370,6 +386,17 @@ def _parse_data(self, data):
data=msg_data,
channel=channel - 1,
)
elif obj_type == APP_TEXT:
# When we encounter an app_text object, parse it and save it in
# self.app_text and continue looping for a message to return
source, reserved1, text_size, reserved2 = app_text_header(data, pos)
# Read until the end of the block rather than using the
# untrusted size bytes
text = data[pos + app_text_header_size : next_pos]
# Append the app_text block, including the size bytes read
# from the header. Caller may determine what to do if there's
# a mismatch in the actual text length
self.app_text.append((source, reserved1, text_size, reserved2, text))

pos = next_pos

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