/*
* 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;
}
}