| // 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; |
| |
| /** |
| * 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; |
| } |
| } |