lds-splice

#!/usr/bin/python3
# Join together sections of several RF samples, in any of the formats ld-decode
# understands. Output to stdout in .lds format.
# XXX This is rather slow (45MiB/s) - it'd be better to use ld-lds-converter/ld-ldf-reader to read

import os
import subprocess
import sys

sys.path.append(os.path.join(sys.path[0], "../ld-decode"))
import lddecode.utils

def usage():
    print("""Usage: lds-splice [FILE START-SAMPLE END-SAMPLE] ...

START-SAMPLE and END-SAMPLE are a half-open range.
If END-SAMPLE is 0, samples are copied until the end of the file.""", file=sys.stderr)
    sys.exit(1)

args = sys.argv[1:]
if (len(args) % 3) != 0:
    usage()

converter = subprocess.Popen(['ld-lds-converter', '-p'], stdin=subprocess.PIPE)

for i in range(0, len(args), 3):
    try:
        filename = args[i]
        start_sample = int(args[i + 1])
        end_sample = int(args[i + 2])
    except ValueError:
        usage()

    # XXX Need a better way of doing this...
    if end_sample == 0:
        end_sample = int(1e15)

    print("Opening", filename, file=sys.stderr)
    with open(filename, "rb") as f:
        loader = lddecode.utils.make_loader(filename)

        CHUNK_SIZE = 1 * 1024 * 1024
        pos = start_sample
        while pos < end_sample:
            print("Reading", filename, "at", pos,
                  "- %d%%" % (int(100 * (pos - start_sample) / (end_sample - start_sample))),
                  file=sys.stderr)

            size = min(end_sample - pos, CHUNK_SIZE)

            # This is a bit ugly: load_packed_data_4_40 is happy with arbitrary
            # starting points, but it can only read a multiple of 4 samples
            padded_size = ((size + 3) // 4) * 4
            assert (padded_size % 4) == 0
            assert padded_size >= size

            # And this is even more ugly: the loaders have no good way of indicating EOF
            try:
                data = loader(f, pos, padded_size)
            except:
                # EOF, presumably
                data = None
            if data is None:
                print("End of file", filename, file=sys.stderr)
                break

            assert len(data) == padded_size
            converter.stdin.write(data[:size])
            pos += size

converter.stdin.close()
converter.wait()