"""Count draw_scene (action 9) records in a fifodump = true board fps.
  py fifofps.py <fifodump>          -> total count
  py fifofps.py <fifodump> <secs>   -> count now, wait, count again, report fps
"""
import sys, time, struct

def count_frames(path):
    n = 0
    with open(path, 'rb') as f:
        data = f.read()
    off = 0
    while off + 8 <= len(data):
        if data[off:off+4] != b'VPXM':
            off += 1
            continue
        ln = struct.unpack_from('<I', data, off+4)[0] & 0x00ffffff
        body = data[off+8:off+8+ln]
        off += 8 + ln
        if len(body) >= 4 and struct.unpack_from('<I', body, 0)[0] == 9:
            n += 1
    return n

path = sys.argv[1]
if len(sys.argv) > 2:
    secs = float(sys.argv[2])
    a = count_frames(path)
    time.sleep(secs)
    b = count_frames(path)
    print(f"{a} -> {b} draw_scene in {secs:.0f}s = {(b-a)/secs:.1f} fps")
else:
    print(count_frames(path), "draw_scene records")