#!/usr/bin/env python3
"""Embed a binary file into the kernel image as a C byte array.

Used by the build to carry the statically linked /sbin/init ELF inside the
kernel, so the ELF loader has something to run before any filesystem is
mounted.

    usage: mkblob.py <input-binary> <output.c> <symbol-name>
"""

import os
import sys


def main():
    if len(sys.argv) != 4:
        sys.stderr.write(f"usage: {os.path.basename(sys.argv[0])} "
                         "<input-binary> <output.c> <symbol-name>\n")
        return 2

    src, dst, symbol = sys.argv[1], sys.argv[2], sys.argv[3]

    try:
        with open(src, "rb") as handle:
            payload = handle.read()
    except OSError as exc:
        sys.stderr.write(f"mkblob: cannot read {src}: {exc}\n")
        return 1

    if not payload:
        sys.stderr.write(f"mkblob: {src} is empty\n")
        return 1

    out = [
        "/* Automatically generated by scripts/mkblob.py. Do not edit. */",
        f'/* source: {os.path.basename(src)} ({len(payload)} bytes) */',
        "",
        "#include <stddef.h>",
        "",
        f"const unsigned char {symbol}[] = {{",
    ]

    for offset in range(0, len(payload), 12):
        chunk = payload[offset:offset + 12]
        out.append("    " + " ".join(f"0x{b:02x}," for b in chunk))

    out += [
        "};",
        "",
        f"const size_t {symbol}_len = sizeof({symbol});",
        "",
    ]

    os.makedirs(os.path.dirname(os.path.abspath(dst)), exist_ok=True)
    try:
        with open(dst, "w") as handle:
            handle.write("\n".join(out))
    except OSError as exc:
        sys.stderr.write(f"mkblob: cannot write {dst}: {exc}\n")
        return 1

    return 0


if __name__ == "__main__":
    sys.exit(main())