src/firmware/lib/fastboot/rust/cbindgen.py

# Copyright 2023 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# This script intentionally does not have a shebang; it uses tools that are not
# available in the Fuchsia repo and must be installed to the local host, so we
# cannot use the hermetic Fuchsia Python. Since this script is rarely used, it's
# also not worth the effort to import the tools and all the maintenance costs
# that would come along with it (b/295039695).
#
# In order to avoid confusion, we remove the shebang to force the user to call
# the script explicitly through a host Python installation; see README.md for
# usage.

import logging
import os
import pathlib
import subprocess

MY_NAME = pathlib.Path(__file__).name
MY_DIR = pathlib.Path(__file__).parent
BINDINGS_PATH = MY_DIR / "ffi_c" / "bindings.h"


def generate_ffi():
    # Generate a Cargo.toml file in the out/ directory.
    logging.info("Building Cargo.toml")
    subprocess.run(["fx", "build", "build/rust:cargo_toml_gen"], check=True)

    # Copy the generated file into this directory as required by cbindgen.
    subprocess.run(
        [
            "fx",
            "gen-cargo",
            "//src/firmware/lib/fastboot/rust:_fastboot_c_rustc_static",
        ],
        check=True,
    )

    # Generate and format the bindings.
    logging.info("Generating C bindings at %s", BINDINGS_PATH)
    subprocess.run(["cbindgen", MY_DIR, "-o", BINDINGS_PATH], check=True)

    # cbindgen doesn't currently add header guards and fx format-code won't add
    # them if they don't exist, so put something there and let fx format-code
    # fix it up. We also need a license header and some lint checks.
    BINDINGS_PATH.write_text(
        f"""\
        // Copyright 2023 The Fuchsia Authors. All rights reserved.
        // Use of this source code is governed by a BSD-style license that can be
        // found in the LICENSE file.

        // This file is auto-generated by {MY_NAME}. See README for details.

        #ifndef FOO_H_
        #define FOO_H_

        // LINT.IfChange

        {BINDINGS_PATH.read_text()}

        // LINT.ThenChange(../src/lib.rs)

        #endif  // FOO_H_
        """
    )
    subprocess.run(
        ["fx", "format-code", f"--files={BINDINGS_PATH}"], check=True
    )

    # Remove the generated Cargo files.
    logging.info("Removing Cargo files")
    os.remove(MY_DIR / "Cargo.toml")
    os.remove(MY_DIR / "Cargo.lock")


def main():
    logging.basicConfig(level=logging.INFO)

    generate_ffi()


if __name__ == "__main__":
    main()