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// Copyright 2014 The Bazel Authors. 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.
package com.google.devtools.build.lib.util;
import com.google.common.base.Preconditions;
/**
* A trie that operates on path segments of an input string instead of individual characters.
*
* <p>Only accepts strings that contain only low-ASCII characters (0-127)
*
* @param <T> the type of the values
*/
public class StringTrie<T> {
private static final int RANGE = 128;
@SuppressWarnings("unchecked")
private static class Node<T> {
private Node() {
children = new Node[RANGE];
}
private T value;
private Node<T> children[];
}
private final Node<T> root;
public StringTrie() {
root = new Node<T>();
}
/**
* Puts a value in the trie.
*/
public void put(CharSequence key, T value) {
Node<T> current = root;
for (int i = 0; i < key.length(); i++) {
char ch = key.charAt(i);
Preconditions.checkState(ch < RANGE);
Node<T> next = current.children[ch];
if (next == null) {
next = new Node<T>();
current.children[ch] = next;
}
current = next;
}
current.value = value;
}
/**
* Gets a value from the trie. If there is an entry with the same key, that will be returned,
* otherwise, the value corresponding to the key that matches the longest prefix of the input.
*/
public T get(String key) {
Node<T> current = root;
T lastValue = current.value;
for (int i = 0; i < key.length(); i++) {
char ch = key.charAt(i);
Preconditions.checkState(ch < RANGE);
current = current.children[ch];
if (current == null) {
break;
}
if (current.value != null) {
lastValue = current.value;
}
}
return lastValue;
}
}
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