#!/usr/bin/env python3
# Fetch a byte range from a guest file via the QEMU guest agent.
# Usage: qga_snip.py <guest_path> <offset> <length> <host_out>
import base64
import json
import socket
import sys

GUEST, OFF, LEN, HOST = sys.argv[1], int(sys.argv[2]), int(sys.argv[3]), sys.argv[4]
import os
SOCK = os.environ.get("QGA_SOCK", "/tmp/qemu-guest-agent.sock")


def recv_line(s):
    buf = b""
    while b"\n" not in buf:
        c = s.recv(65536)
        if not c:
            break
        buf += c
    return buf.split(b"\n", 1)[0]


def cmd(s, obj):
    s.sendall((json.dumps(obj) + "\r\n").encode())
    return json.loads(recv_line(s))


s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
s.settimeout(30.0)
s.connect(SOCK)
h = cmd(s, {"execute": "guest-file-open",
            "arguments": {"path": GUEST, "mode": "r"}})["return"]
cmd(s, {"execute": "guest-file-seek",
        "arguments": {"handle": h, "offset": OFF, "whence": 0}})
r = cmd(s, {"execute": "guest-file-read",
            "arguments": {"handle": h, "count": LEN}})
data = base64.b64decode(r["return"].get("buf-b64", ""))
open(HOST, "wb").write(data)
cmd(s, {"execute": "guest-file-close", "arguments": {"handle": h}})
print(f"GOT {len(data)} bytes @ {OFF} -> {HOST}")