Split blf-files in Python into smaller files

Question

I'm wondering if it is possible to split BLF-files in Python? I know that there is a library (can) that supports BLF-files, but find no documentation on how to split/save. I can read a BLF-file with:

 import can
 log = can.BLFReader("logfile.blf")

Would appreciate any help if anybody has knowledge in how I would split this file, and save it into smaller blf-files.

Answer 1

You can read your logfile and write all messages to new files, changing file every N messages (in my example N=100, which is very low). I find it very useful to look at the doc, otherwise I wouldn't know how to resume iteration over log_in (in this case as a generator) or how to easily get object_count:

import can

OUTPUT_MAX_SIZE = 100

with open("blf_file.blf", 'rb') as f_in:
    log_in = can.io.BLFReader(f_in)
    log_in_iter = log_in.__iter__()
    object_count = log_in.object_count
    i = 0
    while i*OUTPUT_MAX_SIZE < object_count:
        i += 1
        with open(f"smaller_file{i}.blf", 'wb') as f_out:
            log_out = can.io.BLFWriter(f_out)
            j = 0
            while j < OUTPUT_MAX_SIZE:
                log_out.on_message_received(log_in_iter.__next__())
                j += 1
            log_out.stop()