79 lines
2.5 KiB
Java
79 lines
2.5 KiB
Java
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/*
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* Copyright (C) 2010 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.internal.util;
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/**
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* A pool of string instances. Unlike the {@link String#intern() VM's
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* interned strings}, this pool provides no guarantee of reference equality.
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* It is intended only to save allocations. This class is not thread safe.
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*
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* @hide
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*/
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@android.ravenwood.annotation.RavenwoodKeepWholeClass
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public final class StringPool {
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private final String[] mPool = new String[512];
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/**
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* Constructs string pool.
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*/
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public StringPool() {
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}
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private static boolean contentEquals(String s, char[] chars, int start, int length) {
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if (s.length() != length) {
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return false;
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}
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for (int i = 0; i < length; i++) {
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if (chars[start + i] != s.charAt(i)) {
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return false;
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}
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}
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return true;
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}
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/**
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* Returns a string equal to {@code new String(array, start, length)}.
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*
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* @param array buffer containing string chars
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* @param start offset in {@code array} where string starts
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* @param length length of string
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* @return string equal to {@code new String(array, start, length)}
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*/
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public String get(char[] array, int start, int length) {
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// Compute an arbitrary hash of the content
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int hashCode = 0;
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for (int i = start; i < start + length; i++) {
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hashCode = (hashCode * 31) + array[i];
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}
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// Pick a bucket using Doug Lea's supplemental secondaryHash function (from HashMap)
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hashCode ^= (hashCode >>> 20) ^ (hashCode >>> 12);
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hashCode ^= (hashCode >>> 7) ^ (hashCode >>> 4);
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int index = hashCode & (mPool.length - 1);
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String pooled = mPool[index];
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if (pooled != null && contentEquals(pooled, array, start, length)) {
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return pooled;
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}
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String result = new String(array, start, length);
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mPool[index] = result;
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return result;
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}
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}
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