| /* |
| * Copyright (C) 2010 The Android Open Source Project |
| * |
| * 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. |
| */ |
| |
| package libcore.internal; |
| |
| /** |
| * A pool of string instances. Unlike the {@link String#intern() VM's |
| * interned strings}, this pool provides no guarantee of reference equality. |
| * It is intended only to save allocations. This class is not thread safe. |
| */ |
| public final class StringPool { |
| |
| private final String[] pool = new String[512]; |
| |
| private static boolean contentEquals(String s, char[] chars, int start, int length) { |
| if (s.length() != length) { |
| return false; |
| } |
| for (int i = 0; i < length; i++) { |
| if (chars[start + i] != s.charAt(i)) { |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /** |
| * Returns a string equal to {@code new String(array, start, length)}. |
| */ |
| public String get(char[] array, int start, int length) { |
| // Compute an arbitrary hash of the content |
| int hashCode = 0; |
| for (int i = start; i < start + length; i++) { |
| hashCode = (hashCode * 31) + array[i]; |
| } |
| |
| // Pick a bucket using Doug Lea's supplemental secondaryHash function (from HashMap) |
| hashCode ^= (hashCode >>> 20) ^ (hashCode >>> 12); |
| hashCode ^= (hashCode >>> 7) ^ (hashCode >>> 4); |
| int index = hashCode & (pool.length - 1); |
| |
| String pooled = pool[index]; |
| if (pooled != null && contentEquals(pooled, array, start, length)) { |
| return pooled; |
| } |
| |
| String result = new String(array, start, length); |
| pool[index] = result; |
| return result; |
| } |
| } |