rs_bindings_from_cc/src_code_gen.cc

// Part of the Crubit project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#include "rs_bindings_from_cc/src_code_gen.h"

#include <string>

#include "common/ffi_types.h"
#include "common/status_macros.h"
#include "rs_bindings_from_cc/ir.h"
#include "clang/Format/Format.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/JSON.h"

namespace crubit {

// FFI equivalent of `Bindings`.
struct FfiBindings {
  FfiU8SliceBox rs_api;
  FfiU8SliceBox rs_api_impl;
};

// This function is implemented in Rust.
extern "C" FfiBindings GenerateBindingsImpl(FfiU8Slice json,
                                            FfiU8Slice crubit_support_path,
                                            FfiU8Slice rustfmt_exe_path,
                                            FfiU8Slice rustfmt_config_path);

// Creates `Bindings` instance from copied data from `ffi_bindings`.
static absl::StatusOr<Bindings> MakeBindingsFromFfiBindings(
    const FfiBindings& ffi_bindings) {
  Bindings bindings;

  const FfiU8SliceBox& rs_api = ffi_bindings.rs_api;
  const FfiU8SliceBox& rs_api_impl = ffi_bindings.rs_api_impl;

  bindings.rs_api = std::string(rs_api.ptr, rs_api.size);

  std::string impl{rs_api_impl.ptr, rs_api_impl.size};
  llvm::Expected<std::string> maybe_formatted =
      clang::tooling::applyAllReplacements(
          impl,
          clang::format::reformat(
              clang::format::getGoogleStyle(clang::format::FormatStyle::LK_Cpp),
              impl, clang::tooling::Range(0, impl.size()), "<stdin>"));
  if (llvm::Error error = maybe_formatted.takeError()) {
    return absl::InternalError(absl::StrCat("Failed to format rs_api_impl: ",
                                            toString(std::move(error))));
  }
  bindings.rs_api_impl = *maybe_formatted;

  return bindings;
}

// Deallocates given `ffi_bindings` instance that was created in Rust.
static void FreeFfiBindings(FfiBindings ffi_bindings) {
  FreeFfiU8SliceBox(ffi_bindings.rs_api);
  FreeFfiU8SliceBox(ffi_bindings.rs_api_impl);
}

absl::StatusOr<Bindings> GenerateBindings(
    const IR& ir, absl::string_view crubit_support_path,
    absl::string_view rustfmt_exe_path, absl::string_view rustfmt_config_path) {
  std::string json = llvm::formatv("{0}", ir.ToJson());

  FfiBindings ffi_bindings = GenerateBindingsImpl(
      MakeFfiU8Slice(json), MakeFfiU8Slice(crubit_support_path),
      MakeFfiU8Slice(rustfmt_exe_path), MakeFfiU8Slice(rustfmt_config_path));
  CRUBIT_ASSIGN_OR_RETURN(Bindings bindings,
                          MakeBindingsFromFfiBindings(ffi_bindings));
  FreeFfiBindings(ffi_bindings);
  return bindings;
}

}  // namespace crubit