import struct, sys

# parse usbpcap file, extract bulk transfer payloads on EP 0x81,
# find 0x1bb1b11b markers and dump tail words
path = r"C:\Project\MAG160C\analysis\captures\official_hand.pcap"
data = open(path, "rb").read()
magic = data[:4]
print("pcap magic:", magic.hex())
# USBPcap: linktype 249? global header 24 bytes: magic, vMaj, vMin, tz, sigfigs, snaplen, linktype
lt = struct.unpack_from("<I", data, 20)[0]
print("linktype:", lt)

# find all occurrences of the frame marker
idx = 0
count = 0
frames = []
while True:
    i = data.find(b"\x1b\xb1\xb1\x1b", idx)
    if i < 0: break
    idx = i + 4
    count += 1
    if count <= 3 or count % 50 == 0:
        if i + 0x9640 < len(data):
            # header
            hdr = struct.unpack_from("<8I", data, i)
            # tail words
            tail = struct.unpack_from("<8I", data, i + 0x1c + hdr[2])
            frames.append((i, hdr, tail))
            print(f"frame@{i:#x} hdr={[hex(x) for x in hdr[:5]]} tail[0:8]={[hex(x) for x in tail]}")
    if count > 120: break
print("total markers scanned:", count)