diff --git a/mapillary_tools/geotag/geotag_images_from_nmea_file.py b/mapillary_tools/geotag/geotag_images_from_nmea_file.py index e6b210dc..6c11adcc 100644 --- a/mapillary_tools/geotag/geotag_images_from_nmea_file.py +++ b/mapillary_tools/geotag/geotag_images_from_nmea_file.py @@ -40,10 +40,17 @@ # The byte order mark, which some editors write at the start of a UTF-8 file _BOM = "\ufeff" -# How much of a file tells whether it is text at all, before it is read whole: -# a video given as an NMEA file is gigabytes +# How much of a file tells whether it is an NMEA log at all, before it is read +# whole: a video given as an NMEA file is gigabytes _SNIFF_BYTES = 64 * 1024 +# An RMC or a GGA sentence, as in _SENTENCE_RE, in the bytes of a file +_SENTENCE_BYTES_RE = re.compile(rb"\$[A-Z]{2}(RMC|GGA),") + +# A NUL byte, which a logger leaves in a log after a power cut, such as on an +# SD card: it ends a line, as no sentence holds one +_NUL = "\x00" + # The checksum that ends a sentence: *HH. It is optional _CHECKSUM_RE = re.compile(r"\*[0-9A-Fa-f]{2}\s*$") @@ -157,15 +164,16 @@ def get_lat_lon_time_from_nmea(nmea_file: Path) -> list[geo.Point]: own fields show it. A file of which no fix can be read raises ValueError, which says why, if it has malformed sentences or bytes that are not text. - A file that is not text at all, which its first bytes show, raises - ValueError without being read further. + A file that is no NMEA log at all, such as a video, which its first bytes + show (see _looks_binary()), raises ValueError without being read further. + NUL bytes, which a logger leaves in a log after a power cut, end a line. A file is read once in a process, however many times it is asked for. """ with nmea_file.open("rb") as f: head = f.read(_SNIFF_BYTES) - if not _looks_like_text(head): - raise ValueError("it is not text") + if _looks_binary(head): + raise ValueError(_describe_binary(head)) data = head + f.read() key = (str(nmea_file.resolve()), hashlib.sha256(data).hexdigest()) read = _READ.get(key) @@ -182,25 +190,49 @@ def get_lat_lon_time_from_nmea(nmea_file: Path) -> list[geo.Point]: return [dataclasses.replace(p) for p in read] -def _looks_like_text(head: bytes) -> bool: +def _looks_binary(head: bytes) -> bool: r""" - Whether the first bytes **head** of a file can be those of a text file: - without NUL bytes, and mostly bytes that decode as UTF-8, where a log may - have a few bytes damaged + Whether the first bytes **head** of a file show it to be no NMEA log at + all, such as a video: they hold no RMC or GGA sentence, and NUL bytes or + mostly bytes that do not decode as UTF-8. A log padded with NUL bytes, as a + logger leaves it after a power cut, holds sentences, and so does one with + a few bytes damaged - >>> _looks_like_text(b"$GPRMC,024636.00,A,3735.30670,N\r\n") - True - >>> _looks_like_text(b"$GPRMC,024636.00,\xe9,3735.30670,N\r\n") - True - >>> _looks_like_text(b"\x00\x00\x00\x18ftypmp42") + >>> _looks_binary(b"$GPRMC,024636.00,A,3735.30670,N\r\n" + b"\x00" * 100) False - >>> _looks_like_text(b"\xca\xfe\xba\xbe" * 100) + >>> _looks_binary(b"\x00" * 100 + b"$GPGGA,024636.00,3735.30670,N\r\n") False + >>> _looks_binary(b"$GPRMC,024636.00,\xe9,3735.30670,N\r\n") + False + >>> _looks_binary(b"$GPGSV,3,1,11,03,03,111,00\r\n") + False + >>> _looks_binary(b"\x00\x00\x00\x18ftypmp42") + True + >>> _looks_binary(b"\xca\xfe\xba\xbe" * 100) + True """ - if b"\x00" in head: + if _SENTENCE_BYTES_RE.search(head): return False + if b"\x00" in head: + return True text = head.decode("utf-8", errors="replace") - return text.count(_NOT_TEXT) * 2 <= len(text) + return len(text) < text.count(_NOT_TEXT) * 2 + + +def _describe_binary(head: bytes) -> str: + r""" + Why a file whose first bytes **head** show it to be no NMEA log is not + read: it is UTF-16 text, which some Windows tools write, or no text at all + + >>> _describe_binary("$GPRMC,024636.00,A".encode("utf-16")) + 'it is UTF-16 text, which is not read: save it as UTF-8 or ASCII' + >>> _describe_binary(b"\x00\x00\x00\x18ftypmp42") + 'it is not text' + """ + for encoding in ("utf-16", "utf-16-le", "utf-16-be"): + if _SENTENCE_RE.search(head.decode(encoding, errors="ignore")): + return "it is UTF-16 text, which is not read: save it as UTF-8 or ASCII" + return "it is not text" def _read_nmea_data(nmea_file: Path, data: bytes) -> list[geo.Point]: @@ -217,14 +249,15 @@ def _read_nmea_data(nmea_file: Path, data: bytes) -> list[geo.Point]: io.BytesIO(data), encoding="utf-8-sig", errors="replace" ) as f: lines = f.readlines() - lines = [line.rstrip("\n\r").lstrip(_BOM) for line in lines] not_text = any(_NOT_TEXT in line for line in lines) - # (line number, line) of each RMC and GGA sentence + # (line number, line) of each RMC and GGA sentence, of the lines that NUL + # bytes end too (see _NUL) sentences = [ - (number, line) + (number, piece.lstrip(_BOM)) for number, line in enumerate(lines, start=1) - if _SENTENCE_RE.search(line) + for piece in line.rstrip("\n\r").split(_NUL) + if _SENTENCE_RE.search(piece) ] messages = [] diff --git a/tests/unit/test_nmea_parser.py b/tests/unit/test_nmea_parser.py index 1df9f548..b4d91439 100644 --- a/tests/unit/test_nmea_parser.py +++ b/tests/unit/test_nmea_parser.py @@ -503,6 +503,54 @@ def test_a_file_that_is_not_text_fails_without_being_read_whole(tmp_path, head): _read_bytes(tmp_path, head + padding + sentences) +def test_a_log_padded_with_nul_bytes_is_read(tmp_path, caplog): + """ + A logger leaves NUL bytes in a log after a power cut, such as on an SD card: + one NUL byte failed the whole log as not text + """ + lines = [_rmc("024636.00"), _gga("024636.00"), _rmc("024637.00"), _gga("024637.00")] + + with caplog.at_level(logging.WARNING): + times = _read_bytes(tmp_path, _crlf(lines) + b"\x00" * 4096) + + assert len(times) == 2 + assert not caplog.text + + +def test_nul_bytes_before_the_first_sentence_are_skipped(tmp_path, caplog): + lines = [_rmc("024636.00"), _gga("024636.00")] + + with caplog.at_level(logging.WARNING): + times = _read_bytes(tmp_path, b"\x00" * 512 + _crlf(lines)) + + assert len(times) == 1 + assert not caplog.text + + +def test_nul_bytes_end_a_sentence_as_a_line_end_does(tmp_path, caplog): + """A logger that resumed after a power cut wrote on after the NUL bytes""" + first = (_rmc("024636.00") + "\r\n" + _gga("024636.00")).encode("ascii") + second = _crlf([_rmc("024637.00"), _gga("024637.00")]) + + with caplog.at_level(logging.WARNING): + times = _read_bytes(tmp_path, first + b"\x00" * 64 + second) + + assert len(times) == 2 + assert not caplog.text + + +def test_a_sentence_with_nul_bytes_inside_is_skipped(tmp_path, caplog): + damaged = _gga("024637.00").replace(",N,", ",N\0\0", 1) + lines = [_rmc("024636.00"), _gga("024636.00"), _rmc("024637.00"), damaged] + content = "".join(f"{line}\r\n" for line in lines).encode("ascii") + + with caplog.at_level(logging.WARNING): + times = _read_bytes(tmp_path, content) + + assert len(times) == 1 + assert "Skipping 1 of the 4 RMC and GGA sentences" in caplog.text + + def test_a_log_longer_than_what_tells_text_is_read_whole(tmp_path): lines = [] for minute in range(60): @@ -543,13 +591,14 @@ def test_logs_with_byte_order_marks_appended_are_read(tmp_path, caplog): assert not caplog.text -def test_a_utf16_log_is_not_read(tmp_path): - """As one that is not text: NMEA is ASCII""" +@pytest.mark.parametrize("encoding", ["utf-16", "utf-16-le", "utf-16-be"]) +def test_a_utf16_log_is_not_read(tmp_path, encoding): + """NMEA is ASCII: UTF-16 is not read, and the error says it is UTF-16""" content = "".join( f"{line}\r\n" for line in [_rmc("024636.00"), _gga("024636.00")] - ).encode("utf-16") + ).encode(encoding) - with pytest.raises(ValueError, match="^it is not text$"): + with pytest.raises(ValueError, match="^it is UTF-16 text, which is not read"): _read_bytes(tmp_path, content)