adding packages

2026-01-15 14:38:46 -08:00
parent ef86e3ab6a
commit 6869cf47e5
5253 changed files with 726695 additions and 34 deletions
@@ -0,0 +1,63 @@
+// Copyright 2017, the Chromium 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:math';
+
+/// Utility class for generating Firebase child node keys.
+///
+/// Since the Flutter plugin API is asynchronous, there's no way for us
+/// to use the native SDK to generate the node key synchronously and we
+/// have to do it ourselves if we want to be able to reference the
+/// newly-created node synchronously.
+///
+/// This code is based on a Firebase blog post and ported to Dart.
+/// https://firebase.googleblog.com/2015/02/the-2120-ways-to-ensure-unique_68.html
+class PushIdGenerator {
+  static const String PUSH_CHARS =
+      '-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';
+
+  static final Random _random = Random();
+
+  static int? _lastPushTime;
+
+  static final List<int?> _lastRandChars = List<int?>.filled(12, null, growable: false);
+
+  static String generatePushChildName() {
+    int now = DateTime.now().millisecondsSinceEpoch;
+    final bool duplicateTime = (now == _lastPushTime);
+    _lastPushTime = now;
+
+    final List<String?> timeStampChars = List<String?>.filled(8, null, growable: false);
+    for (int i = 7; i >= 0; i--) {
+      timeStampChars[i] = PUSH_CHARS[now % 64];
+      now = (now / 64).floor();
+    }
+    assert(now == 0);
+
+    final StringBuffer result = StringBuffer(timeStampChars.join());
+
+    if (!duplicateTime) {
+      for (int i = 0; i < 12; i++) {
+        _lastRandChars[i] = _random.nextInt(64);
+      }
+    } else {
+      _incrementArray();
+    }
+    for (int i = 0; i < 12; i++) {
+      result.write(PUSH_CHARS[_lastRandChars[i]!]);
+    }
+    assert(result.length == 20);
+    return result.toString();
+  }
+
+  static void _incrementArray() {
+    for (int i = 11; i >= 0; i--) {
+      if (_lastRandChars[i] != 63) {
+        _lastRandChars[i] = _lastRandChars[i]! + 1;
+        return;
+      }
+      _lastRandChars[i] = 0;
+    }
+  }
+}