def test_simple_strings(self):
strings = [
b"123456789",
b"0123456789",
b"01234567890",
b"012345678901",
b"0123456789012",
b"01234567890123",
b"012345678901234",
b"0123456789012345",
b"01234567890123456"
]
crcs = [
0xbb3d,
0x443d,
0xc585,
0x77c5,
0x8636,
0x0346,
0x2583,
0xb6a4,
0xad37
]
self.assertEqual(len(strings), len(crcs))
for i in range(len(strings)):
s = strings[i]
crc = compute_crc(io.BytesIO(s), len(s))
self.assertEqual(crc, crcs[i])
def foo():
import io
import os
filename = "C:\\Users\\jflam\\OneDrive\\Garmin\\2010-03-22-07-25-44.fit"
#filename = "C:\\Users\\jflam\\OneDrive\\Garmin\\2010-03-21-20-31-06.fit"
stream = io.open(filename, "rb")
crc = compute_crc(stream, os.path.getsize(filename))
print(crc)
def parse_fit_file(path, validate_crc = False):
"""Parse a fit file.
Parameters
----------
path: string
Path to the .fit file
validate_crc: bool
Compute the CRC16 of the file and compare with embedded CRC16. Default is False.
Yields
------
Message
Individual Message objects from the .fit file.
Examples
--------
>>> for message in parse_fit_file('fit_file.fit'):
pass
"""
stream = io.open(path, "rb")
file_header = FileHeader(stream)
if validate_crc:
pos = stream.seek(0)
crc = compute_crc(stream, file_header.size + file_header.data_size)
file_crc = read_uint16(stream)
# TODO: debug why CRC is failing with real files
# print(pos, format(self.crc, "0x"), format(self.file_crc, "0x"))
# Seek to the start of the data (past the file header)
pos = stream.seek(file_header.size)
bytes_to_read = file_header.data_size
bytes_read = 0
# Message definitions are parsed internally by the parser and not exposed to
# the caller. We store all of them in this dict:
local_message_definitions = {}
while bytes_read < bytes_to_read:
header = read_uint8(stream)
# Normal header (vs. timestamp offset header is indicated by bit 7)
# Message type is indicated by bit 6
# 1 == definition
# 0 == record
local_message_number = header & 0xf
if (header & 0x80) == 0 and (header & 0x40) == 0x40:
# Parse the message definition and store the definition in our array
message_definition = MessageDefinition(header, stream)
local_message_definitions[local_message_number] = message_definition
bytes_read += message_definition.MessageDefinitionSize() + 1
elif (header & 0x80) == 0 and (header & 0x40) == 0:
current_message_definition = local_message_definitions[local_message_number]
assert current_message_definition is not None
# This design reads the current message into an in-memory byte array.
# An alternate design would involve passing in the current binary reader
# and allowing the caller of Message to read fields using the binary
# reader directly instead of creating a MemoryStream over the byte array
# and using a different BinaryReader in the Message. I have done
# exactly this and measured the performance, and it is actually SLOWER
# than this approach. I haven't root caused why, but would assume that
# Seek-ing arbitrarily using the BinaryReader over the FileStream is
# slow vs. Seek-ing over a BinaryReader over a MemoryStream.
message = Message(header, current_message_definition, stream)
yield message
bytes_read += current_message_definition.size + 1
