[verified] Publish ReelBox source under GPLv3

lib/state/cache_service.dart

@@ -0,0 +1,75 @@
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/painting.dart';
+import 'package:path_provider/path_provider.dart';
+
+class CacheSnapshot {
+  const CacheSnapshot({required this.memoryBytes, required this.diskBytes});
+  final int memoryBytes, diskBytes;
+  int get totalBytes => memoryBytes + diskBytes;
+}
+
+/// Disposable cache only. Never sweep the temporary/app-support directories:
+/// downloads, pending packages and private library data may also live there.
+class CacheService {
+  CacheService({Future<Directory> Function()? directory})
+    : _directory = directory ?? _defaultDirectory;
+  final Future<Directory> Function() _directory;
+
+  static Future<Directory> _defaultDirectory() async =>
+      Directory('${(await getTemporaryDirectory()).path}/reelbox-cache');
+
+  Future<CacheSnapshot> measure() async {
+    var diskBytes = 0;
+    if (!kIsWeb) {
+      final directory = await _directory();
+      // Ignore links even when the cache root itself is one.
+      if (await FileSystemEntity.type(directory.path, followLinks: false) ==
+          FileSystemEntityType.directory) {
+        await for (final entry in directory.list(
+          recursive: true,
+          followLinks: false,
+        )) {
+          if (await FileSystemEntity.type(entry.path, followLinks: false) ==
+              FileSystemEntityType.file) {
+            try {
+              diskBytes += await File(entry.path).length();
+            } on FileSystemException {
+              // An evicted file may disappear during measurement.
+            }
+          }
+        }
+      }
+    }
+    return CacheSnapshot(
+      memoryBytes: PaintingBinding.instance.imageCache.currentSizeBytes,
+      diskBytes: diskBytes,
+    );
+  }
+
+  Future<void> clear() async {
+    PaintingBinding.instance.imageCache.clear();
+    PaintingBinding.instance.imageCache.clearLiveImages();
+    if (kIsWeb) return;
+    final directory = await _directory();
+    if (await FileSystemEntity.type(directory.path, followLinks: false) !=
+        FileSystemEntityType.directory) {
+      return;
+    }
+    // Only regular files. Do not follow or delete links to other storage.
+    await for (final entry in directory.list(
+      recursive: true,
+      followLinks: false,
+    )) {
+      if (await FileSystemEntity.type(entry.path, followLinks: false) ==
+          FileSystemEntityType.file) {
+        try {
+          await File(entry.path).delete();
+        } on FileSystemException {
+          if (await File(entry.path).exists()) rethrow;
+        }
+      }
+    }
+  }
+}