Implement same on win32. (#213)

Author: brianquinlan

pkgs/io_file/README.md

@@ -23,7 +23,7 @@ See
 |  enum dir contents    |         |       |       |       |         |            |              |
 |  exists               |         |       |       |       |         |            |              |
 |  get metadata (stat)  |         |       |       |       |         |            |              |
-|  identity (same file) |         |   ✓   |   ✓   |   ✓   |         |            |              |
+|  identity (same file) |         |   ✓   |   ✓   |   ✓   |    ✓    |            |              |
 |  open                 |         |       |       |       |         |            |              |
 |  read file (bytes)    |         |   ✓   |   ✓   |   ✓   |    ✓    |            |              |
 |  read file (lines)    |         |       |       |       |         |            |              |

pkgs/io_file/lib/src/vm_windows_file_system.dart

@@ -75,6 +75,51 @@ Exception _getError(int errorCode, String message, String path) {
 
 /// A [FileSystem] implementation for Windows systems.
 base class WindowsFileSystem extends FileSystem {
+  @override
+  bool same(String path1, String path2) => using((arena) {
+    // Calling `GetLastError` for the first time causes the `GetLastError`
+    // symbol to be loaded, which resets `GetLastError`. So make a harmless
+    // call before the value is needed.
+    win32.GetLastError();
+
+    final info1 = _byHandleFileInformation(path1, arena);
+    final info2 = _byHandleFileInformation(path2, arena);
+
+    return info1.dwVolumeSerialNumber == info2.dwVolumeSerialNumber &&
+        info1.nFileIndexHigh == info2.nFileIndexHigh &&
+        info1.nFileIndexLow == info2.nFileIndexLow;
+  });
+
+  // NOTE: the return value is allocated in the given arena!
+  static win32.BY_HANDLE_FILE_INFORMATION _byHandleFileInformation(
+    String path,
+    ffi.Arena arena,
+  ) {
+    final h = win32.CreateFile(
+      path.toNativeUtf16(allocator: arena),
+      0,
+      win32.FILE_SHARE_READ | win32.FILE_SHARE_WRITE | win32.FILE_SHARE_DELETE,
+      nullptr,
+      win32.OPEN_EXISTING,
+      win32.FILE_FLAG_BACKUP_SEMANTICS,
+      win32.NULL,
+    );
+    if (h == win32.INVALID_HANDLE_VALUE) {
+      final errorCode = win32.GetLastError();
+      throw _getError(errorCode, 'CreateFile failed', path);
+    }
+    try {
+      final info = arena<win32.BY_HANDLE_FILE_INFORMATION>();
+      if (win32.GetFileInformationByHandle(h, info) == win32.FALSE) {
+        final errorCode = win32.GetLastError();
+        throw _getError(errorCode, 'GetFileInformationByHandle failed', path);
+      }
+      return info.ref;
+    } finally {
+      win32.CloseHandle(h);
+    }
+  }
+
   @override
   void createDirectory(String path) => using((arena) {
     _primeGetLastError();
@@ -237,7 +282,7 @@ base class WindowsFileSystem extends FileSystem {
     };
 
     final f = win32.CreateFile(
-      path.toNativeUtf16(),
+      path.toNativeUtf16(allocator: arena),
       mode == WriteMode.appendExisting
           ? win32.FILE_APPEND_DATA
           : win32.FILE_GENERIC_WRITE,

pkgs/io_file/test/same_test.dart

@@ -2,14 +2,15 @@
 // 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.
 
-@TestOn('posix')
+@TestOn('vm')
 library;
 
 import 'dart:io';
 
 import 'package:io_file/io_file.dart';
 import 'package:stdlibc/stdlibc.dart' as stdlibc;
 import 'package:test/test.dart';
+import 'package:win32/win32.dart' as win32;
 
 import 'test_utils.dart';
 
@@ -39,9 +40,14 @@ void main() {
         () => fileSystem.same(path1, path2),
         throwsA(
           isA<PathNotFoundException>()
-              .having((e) => e.message, 'message', 'stat failed')
               .having((e) => e.path, 'path', path1)
-              .having((e) => e.osError?.errorCode, 'errorCode', stdlibc.ENOENT),
+              .having(
+                (e) => e.osError?.errorCode,
+                'errorCode',
+                Platform.isWindows
+                    ? win32.ERROR_FILE_NOT_FOUND
+                    : stdlibc.ENOENT,
+              ),
         ),
       );
     });
@@ -55,9 +61,14 @@ void main() {
         () => fileSystem.same(path1, path2),
         throwsA(
           isA<PathNotFoundException>()
-              .having((e) => e.message, 'message', 'stat failed')
               .having((e) => e.path, 'path', path2)
-              .having((e) => e.osError?.errorCode, 'errorCode', stdlibc.ENOENT),
+              .having(
+                (e) => e.osError?.errorCode,
+                'errorCode',
+                Platform.isWindows
+                    ? win32.ERROR_FILE_NOT_FOUND
+                    : stdlibc.ENOENT,
+              ),
         ),
       );
     });
@@ -70,9 +81,14 @@ void main() {
         () => fileSystem.same(path1, path2),
         throwsA(
           isA<PathNotFoundException>()
-              .having((e) => e.message, 'message', 'stat failed')
               .having((e) => e.path, 'path', path1)
-              .having((e) => e.osError?.errorCode, 'errorCode', stdlibc.ENOENT),
+              .having(
+                (e) => e.osError?.errorCode,
+                'errorCode',
+                Platform.isWindows
+                    ? win32.ERROR_FILE_NOT_FOUND
+                    : stdlibc.ENOENT,
+              ),
         ),
       );
     });
@@ -87,9 +103,14 @@ void main() {
         () => fileSystem.same(path1, path2),
         throwsA(
           isA<PathNotFoundException>()
-              .having((e) => e.message, 'message', 'stat failed')
               .having((e) => e.path, 'path', path1)
-              .having((e) => e.osError?.errorCode, 'errorCode', stdlibc.ENOENT),
+              .having(
+                (e) => e.osError?.errorCode,
+                'errorCode',
+                Platform.isWindows
+                    ? win32.ERROR_FILE_NOT_FOUND
+                    : stdlibc.ENOENT,
+              ),
         ),
       );
     });
@@ -104,9 +125,14 @@ void main() {
         () => fileSystem.same(path1, path2),
         throwsA(
           isA<PathNotFoundException>()
-              .having((e) => e.message, 'message', 'stat failed')
               .having((e) => e.path, 'path', path2)
-              .having((e) => e.osError?.errorCode, 'errorCode', stdlibc.ENOENT),
+              .having(
+                (e) => e.osError?.errorCode,
+                'errorCode',
+                Platform.isWindows
+                    ? win32.ERROR_FILE_NOT_FOUND
+                    : stdlibc.ENOENT,
+              ),
         ),
       );
     });
@@ -120,9 +146,14 @@ void main() {
         () => fileSystem.same(path1, path2),
         throwsA(
           isA<PathNotFoundException>()
-              .having((e) => e.message, 'message', 'stat failed')
               .having((e) => e.path, 'path', path1)
-              .having((e) => e.osError?.errorCode, 'errorCode', stdlibc.ENOENT),
+              .having(
+                (e) => e.osError?.errorCode,
+                'errorCode',
+                Platform.isWindows
+                    ? win32.ERROR_FILE_NOT_FOUND
+                    : stdlibc.ENOENT,
+              ),
         ),
       );
     });
@@ -174,13 +205,17 @@ void main() {
       expect(fileSystem.same(path1, path2), isTrue);
     });
 
-    test('hard links to same file', () {
-      final path1 = '$tmp/file1';
-      final path2 = '$tmp/file2';
-      File(path1).writeAsStringSync('Hello World');
-      stdlibc.link(path1, path2);
-      expect(fileSystem.same(path1, path2), isTrue);
-    });
+    test(
+      'hard links to same file',
+      () {
+        final path1 = '$tmp/file1';
+        final path2 = '$tmp/file2';
+        File(path1).writeAsStringSync('Hello World');
+        stdlibc.link(path1, path2);
+        expect(fileSystem.same(path1, path2), isTrue);
+      },
+      skip: Platform.isWindows ? 'hard links not supported' : false,
+    );
 
     test('different directories, same content', () {
       final path1 = '$tmp/dir1';