Roll Observatory packages and add a roll script

quiver/lib/src/core/hash.dart

-// Copyright 2013 Google Inc. All Rights Reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-part of quiver.core;
-
-/**
- * Generates a hash code for multiple [objects].
- */
-int hashObjects(Iterable objects) =>
-    _finish(objects.fold(0, (h, i) => _combine(h, i.hashCode)));
-
-/**
- * Generates a hash code for two objects.
- */
-int hash2(a, b) => _finish(_combine(_combine(0, a.hashCode), b.hashCode));
-
-/**
- * Generates a hash code for three objects.
- */
-int hash3(a, b, c) => _finish(
-    _combine(_combine(_combine(0, a.hashCode), b.hashCode), c.hashCode));
-
-/**
- * Generates a hash code for four objects.
- */
-int hash4(a, b, c, d) => _finish(_combine(
-    _combine(_combine(_combine(0, a.hashCode), b.hashCode), c.hashCode),
-    d.hashCode));
-
-// Jenkins hash functions
-
-int _combine(int hash, int value) {
-  hash = 0x1fffffff & (hash + value);
-  hash = 0x1fffffff & (hash + ((0x0007ffff & hash) << 10));
-  return hash ^ (hash >> 6);
-}
-
-int _finish(int hash) {
-  hash = 0x1fffffff & (hash + ((0x03ffffff & hash) << 3));
-  hash = hash ^ (hash >> 11);
-  return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
-}