src/composer/internal/trie.h

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// Trie tree library

#ifndef MOZC_COMPOSER_INTERNAL_TRIE_H_
#define MOZC_COMPOSER_INTERNAL_TRIE_H_

#include <map>
#include <string>
#include <vector>
#include "base/util.h"

namespace mozc {
namespace composer {
template<typename T> class Trie {
 public:
  Trie()
    : has_data_(false) {}

  virtual ~Trie() {
    typename SubTrie::iterator it;
    for (it = trie_.begin(); it != trie_.end(); ++it) {
      delete it->second;
    }
  }

  void AddEntry(const string &key, T data) {
    if (key.empty()) {
      data_ = data;
      has_data_ = true;
      return;
    }

    Trie *sub_trie;
    if (HasSubTrie(GetKeyHead(key))) {
      sub_trie = trie_[GetKeyHead(key)];
    } else {
      sub_trie = new Trie();
      trie_[GetKeyHead(key)] = sub_trie;
    }

    const string key_tail = GetKeyTail(key);
    sub_trie->AddEntry(key_tail, data);
  }

  bool DeleteEntry(const string &key) {
    if (key.empty()) {
      if (trie_.empty()) {
        return true;
      } else {
        has_data_ = false;
        return false;
      }
    }

    if (!HasSubTrie(GetKeyHead(key))) {
      return false;
    }

    Trie *sub_trie = GetSubTrie(key);
    const string sub_key = GetKeyTail(key);
    const bool should_delete_subtrie = sub_trie->DeleteEntry(sub_key);
    if (should_delete_subtrie) {
      delete sub_trie;
      trie_.erase(GetKeyHead(key));
      // If the size of trie_ is 0, This trie should be deleted.
      return trie_.size() == 0;
    } else {
      return false;
    }
  }

  bool LookUp(const string &key, T *data) const {
    if (key.empty()) {
      if (!has_data_) {
        return false;
      }
      *data = data_;
      return true;
    }

    if (!HasSubTrie(GetKeyHead(key))) {
      return false;
    }

    Trie *sub_trie = GetSubTrie(key);
    const string sub_key = GetKeyTail(key);
    return sub_trie->LookUp(sub_key, data);
  }

  bool LookUpPrefix(const string &key,
                    T *data,
                    size_t *key_length,
                    bool *fixed) const {
    if (key.empty() || !HasSubTrie(GetKeyHead(key))) {
      *key_length = 0;
      if (has_data_) {
        *data = data_;
        *fixed = trie_.empty();
        return true;
      } else {
        *fixed = true;
        return false;
      }
    }

    Trie *sub_trie = GetSubTrie(key);
    const string sub_key = GetKeyTail(key);
    if (sub_trie->LookUpPrefix(sub_key, data, key_length, fixed)) {
      *key_length += GetKeyHeadLength(key);
      return true;

    } else if (HasSubTrie(GetKeyHead(key))) {
      *key_length += GetKeyHeadLength(key);
      return false;
    } else if (has_data_) {
      *data = data_;
      *key_length = 0;
      return true;
    } else {
      *key_length += GetKeyHeadLength(key);
      return false;
    }
  }

  bool HasSubTrie(const string &key) const {
    const string head = GetKeyHead(key);

    const typename SubTrie::const_iterator it = trie_.find(head);
    if (it == trie_.end()) {
      return false;
    }

    if (key.size() == head.size()) {
      return true;
    }

    return it->second->HasSubTrie(GetKeyTail(key));
  }

 private:
  string GetKeyHead(const string &key) const {
    return mozc::Util::SubString(key, 0, 1);
  }

  size_t GetKeyHeadLength(const string &key) const {
    return mozc::Util::OneCharLen(key.c_str());
  }

  string GetKeyTail(const string &key) const {
    return key.substr(mozc::Util::OneCharLen(key.c_str()));
  }

  Trie<T> *GetSubTrie(const string &key) const {
    return trie_.find(GetKeyHead(key))->second;
  }

  typedef map<const string, Trie<T> *> SubTrie;
  SubTrie trie_;
  bool has_data_;
  T data_;
};
}  // namespace composer
}  // namespace mozc

#endif  // MOZC_COMPOSER_INTERNAL_TRIE_H_