I am attempting to parse binary data. The data is marked with sentinels ‘0x232349’ and ‘0x232353’. However, the following code:

data = read_file()
data = BitArray(data)
sweep_sent = BitArray('0x232349')
imu_sent = BitArray('0x232353')
list(data.findall(sweep_sent)) 
list(data.findall(imu_sent))

Returns nothing. I know that the sentinels are there – both because I can just see them in the binary file in a hex editor, and because the following function:

def find_sentinel(bitarr, bytestr):
    # Convert the 3-byte string to an integer
    target = int.from_bytes(bytestr.encode(), 'big')
    n = len(bitarr)
    indices = []

    # We need to make sure we have at least 24 bits (3 bytes) to compare
    if n < 24:
        return indices

    # Iterate through the bitarray in chunks of 24 bits (3 bytes)
    for i in range(0, n - 23, 8):  # 8-bit steps, 24 bits is 3 bytes
        # Extract the 24-bit segment
        segment = bitarr[i:i+24]
        # Convert the segment to an integer
        segment_int = segment.uint
        # Compare to the target
        if segment_int == target:
            indices.append(i//8)  # Return the starting byte index of the match

    return indices  # Return -1 if no match is found

Works correctly. However, I would like to use bitstring’s findall(), for a variety of reasons, but especially since performance is important here.