#!/usr/bin/env bash
# 从 Android boot image 解出 Image / ramdisk.img / gaokun3.dtb
# 逻辑抄自 scripts/install-gaokun3.sh，用 header offset 1648 的 dtb_size
set -euo pipefail

IMG="${1:?usage: $0 <boot.img> <outdir>}"
OUT="${2:?usage: $0 <boot.img> <outdir>}"
[ -f "$IMG" ] || { echo "no such file: $IMG" >&2; exit 1; }
mkdir -p "$OUT"

python3 - "$IMG" "$OUT" <<'PYEOF'
import struct, sys, os
img, out = sys.argv[1], sys.argv[2]
with open(img, "rb") as f:
    hdr = f.read(1664)
    if hdr[:8] != b"ANDROID!":
        sys.exit("not an Android boot image (bad magic)")
    u32 = lambda off: struct.unpack_from("<I", hdr, off)[0]
    kernel_size, ramdisk_size, second_size = u32(8), u32(16), u32(24)
    page, ver = u32(36), u32(40)
    if ver != 2:
        sys.exit("expected boot header v2, got %d" % ver)
    recovery_dtbo_size, dtb_size = u32(1632), u32(1648)
    print("  kernel_size      %d" % kernel_size)
    print("  ramdisk_size     %d" % ramdisk_size)
    print("  second_size      %d" % second_size)
    print("  recovery_dtbo    %d" % recovery_dtbo_size)
    print("  dtb_size         %d" % dtb_size)
    print("  page_size        %d" % page)
    align = lambda x: (x + page - 1) // page * page
    off = page
    parts = []
    for size, name in ((kernel_size, "Image"), (ramdisk_size, "ramdisk.img")):
        parts.append((off, size, name))
        off += align(size)
    off += align(second_size) + align(recovery_dtbo_size)
    parts.append((off, dtb_size, "gaokun3.dtb"))
    for start, size, name in parts:
        if size == 0:
            sys.exit("%s is empty in the boot image" % name)
        f.seek(start)
        data = f.read(size)
        if len(data) != size:
            sys.exit("short read for %s" % name)
        with open(os.path.join(out, name), "wb") as o:
            o.write(data)
        print("  wrote %-12s %10d bytes" % (name, size))

PYEOF
echo
echo "=== 验证 ==="
for f in Image ramdisk.img gaokun3.dtb; do
    [ -s "$OUT/$f" ] || { echo "FAIL: $OUT/$f 为空" >&2; exit 1; }
    printf "  %-14s %10d bytes  " "$f" "$(stat -c%s "$OUT/$f")"
    file -b "$OUT/$f"
done
echo
echo "OK"