Java example source code file (TrieParser.java)

This example Java source code file (TrieParser.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

charsequence, gwtcompatible, immutablemap, list, prefix_joiner, publicsuffixtype, string, trieparser, util

The TrieParser.java Java example source code

/*
 * Copyright (C) 2008 The Guava Authors
 *
 * 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.thirdparty.publicsuffix;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Lists;

import java.util.List;

/**
 * Parser for a map of reversed domain names stored as a serialized radix tree.
 */
@GwtCompatible
final class TrieParser {

  private static final Joiner PREFIX_JOINER = Joiner.on("");

  /**
   * Parses a serialized trie representation of a map of reversed public suffixes into an immutable
   * map of public suffixes.
   */
  static ImmutableMap<String, PublicSuffixType> parseTrie(CharSequence encoded) {
    ImmutableMap.Builder<String, PublicSuffixType> builder = ImmutableMap.builder();
    int encodedLen = encoded.length();
    int idx = 0;
    while (idx < encodedLen) {
      idx +=
          doParseTrieToBuilder(
              Lists.<CharSequence>newLinkedList(), encoded.subSequence(idx, encodedLen), builder);
    }
    return builder.build();
  }

  /**
   * Parses a trie node and returns the number of characters consumed.
   *
   * @param stack The prefixes that preceed the characters represented by this node. Each entry of
   *     the stack is in reverse order.
   * @param encoded The serialized trie.
   * @param builder A map builder to which all entries will be added.
   * @return The number of characters consumed from {@code encoded}.
   */
  private static int doParseTrieToBuilder(
      List<CharSequence> stack,
      CharSequence encoded,
      ImmutableMap.Builder<String, PublicSuffixType> builder) {

    int encodedLen = encoded.length();
    int idx = 0;
    char c = '\0';

    // Read all of the characters for this node.
    for (; idx < encodedLen; idx++) {
      c = encoded.charAt(idx);
      if (c == '&' || c == '?' || c == '!' || c == ':' || c == ',') {
        break;
      }
    }

    stack.add(0, reverse(encoded.subSequence(0, idx)));

    if (c == '!' || c == '?' || c == ':' || c == ',') {
      // '!' represents an interior node that represents an ICANN entry in the map.
      // '?' represents a leaf node, which represents an ICANN entry in map.
      // ':' represents an interior node that represents a private entry in the map
      // ',' represents a leaf node, which represents a private entry in the map.
      String domain = PREFIX_JOINER.join(stack);
      if (domain.length() > 0) {
        builder.put(domain, PublicSuffixType.fromCode(c));
      }
    }
    idx++;

    if (c != '?' && c != ',') {
      while (idx < encodedLen) {
        // Read all the children
        idx += doParseTrieToBuilder(stack, encoded.subSequence(idx, encodedLen), builder);
        if (encoded.charAt(idx) == '?' || encoded.charAt(idx) == ',') {
          // An extra '?' or ',' after a child node indicates the end of all children of this node.
          idx++;
          break;
        }
      }
    }
    stack.remove(0);
    return idx;
  }

  private static CharSequence reverse(CharSequence s) {
    return new StringBuilder(s).reverse();
  }
}