Extract the io_file POSIX API into a separate package

.github/workflows/io_file.yml

@@ -33,23 +33,6 @@ jobs:
       - run: dart analyze --fatal-infos
       - run: dart format --output=none --set-exit-if-changed .
 
-  check-generation:
-    # Verify that the generated code is up-to-date. Every platform/arch should
-    # generate the same API bindings.
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [ubuntu-latest, ubuntu-24.04-arm, macos-latest]
-    runs-on: ${{ matrix.os }}
-    steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
-      - uses: dart-lang/setup-dart@e51d8e571e22473a2ddebf0ef8a2123f0ab2c02c
-        with:
-          sdk: dev
-      - run: dart pub get
-      - run: dart --enable-experiment=native-assets run tool/generate.dart
-      - run: git diff --exit-code
-
   desktop-vm-test:
     strategy:
       fail-fast: false

.github/workflows/unix_api.yml

@@ -0,0 +1,65 @@
+name: package:unix_api
+
+permissions: read-all
+
+on:
+  # Run CI on pushes to the main branch, and on PRs against main.
+  push:
+    branches: [ main ]
+    paths:
+      - '.github/workflows/unix_api.yml'
+      - 'pkgs/unix_api/**'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '.github/workflows/unix_api.yml'
+      - 'pkgs/unix_api/**'
+  schedule:
+    - cron: '0 0 * * 0' # weekly
+
+defaults:
+  run:
+    working-directory: pkgs/unix_api
+
+jobs:
+  analyze_and_format:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      - uses: dart-lang/setup-dart@e51d8e571e22473a2ddebf0ef8a2123f0ab2c02c
+        with:
+          sdk: dev
+      - run: dart pub get
+      - run: dart analyze --fatal-infos
+      - run: dart format --output=none --set-exit-if-changed .
+
+  check-generation:
+    # Verify that the generated code is up-to-date. Every platform/arch should
+    # generate the same API bindings.
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-latest, ubuntu-latest, ubuntu-24.04-arm]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      - uses: dart-lang/setup-dart@e51d8e571e22473a2ddebf0ef8a2123f0ab2c02c
+        with:
+          sdk: dev
+      - run: dart pub get
+      - run: dart --enable-experiment=native-assets run tool/generate.dart
+      - run: git diff --exit-code
+
+  desktop-vm-test:
+    strategy:
+      fail-fast: false
+      matrix:
+        sdk: [dev]
+        os: [macos-latest, ubuntu-latest, ubuntu-24.04-arm]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      - uses: dart-lang/setup-dart@e51d8e571e22473a2ddebf0ef8a2123f0ab2c02c
+        with:
+          sdk: ${{ matrix.sdk }}
+      - run: dart --enable-experiment=native-assets test --reporter=failures-only --test-randomize-ordering-seed=random --platform vm

pkgs/io_file/lib/src/vm_posix_file_system.dart

@@ -10,11 +10,11 @@ import 'dart:typed_data';
 
 import 'package:ffi/ffi.dart' as ffi;
 import 'package:path/path.dart' as p;
+import 'package:unix_api/unix_api.dart' as libc;
 
 import 'exceptions.dart';
 import 'file_system.dart';
 import 'internal_constants.dart';
-import 'libc.dart' as libc;
 
 /// The default `mode` to use with `open` calls that may create a file.
 const _defaultMode = 438; // => 0666 => rw-rw-rw-

pkgs/io_file/mobile_test/pubspec.yaml

@@ -37,3 +37,4 @@ dev_dependencies:
       url: https://github.com/canonical/stdlibc.dart.git
   test: ^1.24.0
   uuid: ^4.5.1
+

pkgs/io_file/pubspec.yaml

@@ -11,10 +11,12 @@ dependencies:
   code_assets: ^0.19.0
   ffi: ^2.1.4
   hooks: ^0.19.0
-  logging: ^1.3.0
   meta: ^1.16.0
   native_toolchain_c: ^0.16.0
   path: ^1.9.1
+  unix_api:
+    # Change this to a released version when this package is published.
+    path: ../unix_api
   win32: ^5.14.0
 
 dev_dependencies:

pkgs/io_file/test/copy_file_test.dart

@@ -12,10 +12,10 @@ import 'package:ffi/ffi.dart';
 import 'package:io_file/io_file.dart';
 import 'package:io_file/posix_file_system.dart';
 import 'package:io_file/src/internal_constants.dart' show blockSize;
-import 'package:io_file/src/libc.dart' as libc;
 import 'package:io_file/src/vm_windows_file_system.dart';
 import 'package:path/path.dart' as p;
 import 'package:test/test.dart';
+import 'package:unix_api/unix_api.dart' as libc;
 import 'package:win32/win32.dart' as win32;
 
 import 'errors.dart' as errors;

pkgs/io_file/test/remove_directory_tree_test.dart

@@ -9,10 +9,11 @@ import 'dart:io' as io;
 
 import 'package:ffi/ffi.dart';
 import 'package:io_file/io_file.dart';
-import 'package:io_file/src/libc.dart' as libc;
 import 'package:path/path.dart' as p;
 import 'package:test/test.dart';
+import 'package:unix_api/unix_api.dart' as libc;
 import 'package:win32/win32.dart' as win32;
+
 import 'errors.dart' as errors;
 import 'test_utils.dart';
 

pkgs/unix_api/.gitignore

@@ -0,0 +1,7 @@
+# https://dart.dev/guides/libraries/private-files
+# Created by `dart pub`
+.dart_tool/
+
+# Avoid committing pubspec.lock for library packages; see
+# https://dart.dev/guides/libraries/private-files#pubspeclock.
+pubspec.lock

pkgs/unix_api/CHANGELOG.md

@@ -0,0 +1,3 @@
+## 0.1.0-wip
+
+- Initial version.

pkgs/unix_api/README.md

@@ -0,0 +1,77 @@
+This package provides **experimental** bindings to POSIX APIs e.g. `open`,
+`close`.
+
+## Why have another POSIX API implementation for Dart?
+
+Thare are two existing packages that provide POSIX API bindings for Dart:
+1. [`package:posix`](https://pub.dev/packages/posix)
+2. [`package:stdlibc`](https://pub.dev/packages/stdlibc)
+
+`package:unix_api` requires a native tool chain and has a small amount of
+native code that cannot be tree shaken away. In exchange, it works on all
+POSIX platforms that Dart supports.
+
+| Package      | Required Tools   | Supported Platforms                     | Fixed Disk Usage |
+| :---         | :--------------  | :------------------------------------   | :--------------  |
+|  `posix`     | Dart             | iOS (arm64), Linux (x64), macOS (arm64) | 0 KiB            |
+|  `stdlibc`   | Dart             | iOS (arm64), Linux (x64), macOS (arm64) | 0 KiB            |
+|  `unix_api`  | Dart, C compiler | Android (x64, arm32, arm64), iOS (arm64), Linux (x64, arm64), macOS (x64, arm64) | ~60 KiB |
+
+## Design
+
+The POSIX API is a defined in terms of source, not object compatibility.
+
+For example, glibc defines `stat` as:
+
+`#define stat(fname, buf) __xstat (_STAT_VER, fname, buf)`
+
+So running `ffigen` on `sys/stat.h` will not produce an entry for `stat`.
+
+libc may also reorder `struct` fields across architectures, add extra
+fields, etc. For example, the glibc definition of `struct stat` starts
+with:
+
+```c
+struct stat
+{
+    __dev_t st_dev;		/* Device.  */
+#ifndef __x86_64__
+    unsigned short int __pad1;
+#endif
+#if defined __x86_64__ || !defined __USE_FILE_OFFSET64
+    __ino_t st_ino;		/* File serial number.	*/
+#else
+```
+
+
+`package:unix_api` works around this problem by defining a native (C) function
+for every POSIX function. The native function just calls the corresponding
+POSIX function. For example:
+
+```c
+int libc_shim_rename(const char *old, const char *newy) {
+  return rename(old, newy);
+}
+```
+
+This allows the platforms C compiler to deal with macro expansions,
+platform-specific struct layout, etc.
+
+Then `package:unix_api` uses `package:ffigen` to provide Dart bindings to
+these functions.
+
+
+## Status: Experimental
+
+**NOTE**: This package is currently experimental and published under the
+[labs.dart.dev](https://dart.dev/dart-team-packages) pub publisher in order to
+solicit feedback. 
+
+For packages in the labs.dart.dev publisher we generally plan to either graduate
+the package into a supported publisher (dart.dev, tools.dart.dev) after a period
+of feedback and iteration, or discontinue the package. These packages have a
+much higher expected rate of API and breaking changes.
+
+Your feedback is valuable and will help us evolve this package. For general
+feedback, suggestions, and comments, please file an issue in the 
+[bug tracker](https://github.com/dart-lang/labs/issues).

pkgs/io_file/constants-ffigen.yaml → pkgs/unix_api/constants-ffigen.yaml

@@ -15,7 +15,7 @@ comments:
   style: any
   length: full
 ffi-native:
-  asset-id: package:io_file/libc_shim
+  asset-id: package:unix_api/libc_shim
 structs:
   rename:
     'libc_shim_(.*)': '$1'

pkgs/unix_api/example/unix_api_example.dart

@@ -0,0 +1,9 @@
+// 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 'package:unix_api/unix_api.dart';
+
+void main() {
+  print('I am ${getpid()} and my parent is ${getppid()}');
+}

pkgs/io_file/ffigen.yaml → pkgs/unix_api/ffigen.yaml

@@ -17,7 +17,7 @@ comments:
   style: any
   length: full
 ffi-native:
-  asset-id: package:io_file/libc_shim
+  asset-id: package:unix_api/libc_shim
 structs:
   rename:
     'libc_shim_(.*)': '$1'

pkgs/io_file/hook/build.dart → pkgs/unix_api/hook/build.dart

@@ -19,10 +19,9 @@ void main(List<String> args) async {
     ).run(
       input: input,
       output: output,
-      logger:
-          Logger('')
-            ..level = Level.ALL
-            ..onRecord.listen((record) => print(record.message)),
+      logger: Logger('')
+        ..level = Level.ALL
+        ..onRecord.listen((record) => print(record.message)),
     );
   });
 }