[code_assets] Change gethostname example to use FFIgen (#2532)

Author: dcharkes

pkgs/code_assets/example/build/host_name/lib/src/host_name.dart

@@ -7,40 +7,18 @@ import 'dart:io';
 
 import 'package:ffi/ffi.dart';
 
-/// Get the host name on Unix systems.
-///
-/// C signature: `int gethostname(char *name, size_t size);`
-@Native<Int Function(Pointer<Uint8>, Size)>(
-  symbol: 'gethostname',
-  assetId: 'package:host_name/src/host_name.dart',
-)
-external int _gethostnameUnix(Pointer<Uint8> name, int len);
-
-/// Get the host name on Windows systems.
-///
-/// C signature:
-///
-/// ```
-/// int gethostname(
-///   [out] char *name,
-///   [in]  int  namelen
-/// );
-/// ```
-@Native<Int Function(Pointer<Uint8>, Int)>(
-  symbol: 'gethostname',
-  assetId: 'package:host_name/src/host_name.dart',
-)
-external int _gethostnameWindows(Pointer<Uint8> name, int len);
+import 'third_party/unix.dart' as unix;
+import 'third_party/windows.dart' as windows;
 
 /// The machine's hostname.
 ///
 /// Returns `null` if looking up the machines host name fails.
 String? get hostName => using((arena) {
   const maxHostNameLength = 256;
-  final buffer = arena<Uint8>(maxHostNameLength);
+  final buffer = arena<Char>(maxHostNameLength);
   final result = Platform.isWindows
-      ? _gethostnameWindows(buffer, maxHostNameLength)
-      : _gethostnameUnix(buffer, maxHostNameLength);
+      ? windows.gethostname(buffer, maxHostNameLength)
+      : unix.gethostname(buffer, maxHostNameLength);
 
   if (result != 0) {
     // The `errno` or `WSAGetLastError` are not preserved currently.

pkgs/code_assets/example/build/host_name/lib/src/third_party/unix.dart

@@ -0,0 +1,28 @@
+// Copyright (C) 1991-2022 Free Software Foundation, Inc.
+// This file is part of the GNU C Library.
+//
+// The GNU C Library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// The GNU C Library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with the GNU C Library; if not, see
+// <https://www.gnu.org/licenses/>.
+
+// AUTO GENERATED FILE, DO NOT EDIT.
+//
+// Generated by `package:ffigen`.
+// ignore_for_file: type=lint
+@ffi.DefaultAsset('package:host_name/src/host_name.dart')
+library;
+
+import 'dart:ffi' as ffi;
+
+@ffi.Native<ffi.Int Function(ffi.Pointer<ffi.Char>, ffi.Size)>()
+external int gethostname(ffi.Pointer<ffi.Char> arg0, int arg1);

pkgs/code_assets/example/build/host_name/lib/src/third_party/windows.dart

@@ -0,0 +1,13 @@
+// TODO
+
+// AUTO GENERATED FILE, DO NOT EDIT.
+//
+// Generated by `package:ffigen`.
+// ignore_for_file: type=lint
+@ffi.DefaultAsset('package:host_name/src/host_name.dart')
+library;
+
+import 'dart:ffi' as ffi;
+
+@ffi.Native<ffi.Int Function(ffi.Pointer<ffi.Char>, ffi.Int)>()
+external int gethostname(ffi.Pointer<ffi.Char> name, int namelen);

pkgs/code_assets/example/build/host_name/pubspec.yaml

@@ -16,5 +16,6 @@ dependencies:
   hooks: any
 
 dev_dependencies:
+  ffigen: ^19.1.0
   lints: ^6.0.0
   test: ^1.25.15

pkgs/code_assets/example/build/host_name/src/unix.h

@@ -0,0 +1,5 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include <unistd.h>

pkgs/code_assets/example/build/host_name/src/windows.h

@@ -0,0 +1,5 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include <Winsock2.h>

pkgs/code_assets/example/build/host_name/tool/ffigen.dart

@@ -0,0 +1,61 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:ffigen/ffigen.dart';
+
+void main() {
+  final packageRoot = Platform.script.resolve('../');
+  const ffiNativeConfig = FfiNativeConfig(
+    enabled: true,
+    assetId: 'package:host_name/src/host_name.dart',
+  );
+  final functionDeclarationFilter = DeclarationFilters(
+    shouldInclude: (declaration) => declaration.originalName == 'gethostname',
+  );
+  if (Platform.isWindows) {
+    FfiGen().run(
+      Config(
+        output: packageRoot.resolve('lib/src/third_party/windows.dart'),
+        entryPoints: [packageRoot.resolve('src/windows.h')],
+        preamble: '''
+// This file includes parts which are Copyright (c) 1982-1986 Regents
+// of the University of California.  All rights reserved.  The
+// Berkeley Software License Agreement specifies the terms and
+// conditions for redistribution.
+''',
+        functionDecl: functionDeclarationFilter,
+        ffiNativeConfig: ffiNativeConfig,
+      ),
+    );
+  } else {
+    FfiGen().run(
+      Config(
+        output: packageRoot.resolve('lib/src/third_party/unix.dart'),
+        entryPoints: [packageRoot.resolve('src/unix.h')],
+        preamble: '''
+// Copyright (C) 1991-2022 Free Software Foundation, Inc.
+// This file is part of the GNU C Library.
+//
+// The GNU C Library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// The GNU C Library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with the GNU C Library; if not, see
+// <https://www.gnu.org/licenses/>.
+''',
+        functionDecl: functionDeclarationFilter,
+        ffiNativeConfig: ffiNativeConfig,
+      ),
+    );
+  }
+}