Aho_Corasick.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
# ifndef AHO_CORASICK_H
# define AHO_CORASICK_H
 
# include <string>
# include <string_view>
# include <utility>
# include <array>
 
# include <ah-errors.H>
# include <tpl_array.H>
 
namespace Aleph
{
  class Aho_Corasick
  {
  public:
    struct Match
    {
      size_t position = 0;   
      size_t pattern_id = 0; 
      bool operator==(const Match & other) const noexcept
      {
        return position == other.position and pattern_id == other.pattern_id;
      }
    };
 
  private:
    struct Node
    {
      std::array<int, 256> next;
      int fail = 0;
      int out_link = -1;
      Array<size_t> output;
 
      Node()
      {
        next.fill(-1);
      }
    };
 
    Array<Node> nodes_;
    Array<std::string> patterns_;
    bool built_ = false;
 
    size_t create_node()
    {
      nodes_.append(Node{});
      return nodes_.size() - 1;
    }
 
  public:
    Aho_Corasick()
    {
      nodes_.append(Node{});
    }
 
    void clear()
    {
      nodes_.empty();
      patterns_.empty();
      nodes_.append(Node{});
      built_ = false;
    }
 
    size_t add_pattern(std::string pattern)
    {
      ah_invalid_argument_if(pattern.empty())
        << "Aho_Corasick::add_pattern(): pattern cannot be empty";
 
      size_t state = 0;
      for (const unsigned char c: pattern)
        {
          int next_state = nodes_[state].next[c];
          if (next_state == -1)
            {
              const size_t new_state = create_node();
              nodes_[state].next[c] = static_cast<int>(new_state);
              next_state = static_cast<int>(new_state);
            }
 
          state = static_cast<size_t>(next_state);
        }
 
      const size_t id = patterns_.size();
      patterns_.append(std::move(pattern));
      nodes_[state].output.append(id);
 
      built_ = false;
      return id;
    }
 
    void build()
    {
      Array<size_t> queue;
      size_t head = 0;
 
      nodes_[0].fail = 0;
      nodes_[0].out_link = -1;
 
      for (size_t c = 0; c < 256; ++c)
        if (const int next_state = nodes_[0].next[c]; next_state != -1)
          {
            const auto child = static_cast<size_t>(next_state);
            nodes_[child].fail = 0;
            nodes_[child].out_link = -1;
            queue.append(child);
          }
 
      while (head < queue.size())
        {
          const size_t state = queue[head++];
 
          for (size_t c = 0; c < 256; ++c)
            {
              const int next_state = nodes_[state].next[c];
              if (next_state == -1)
                continue;
 
              const auto child = static_cast<size_t>(next_state);
              auto fail_to = static_cast<size_t>(nodes_[state].fail);
 
              while (fail_to != 0 and nodes_[fail_to].next[c] == -1)
                fail_to = static_cast<size_t>(nodes_[fail_to].fail);
 
              if (const int candidate = nodes_[fail_to].next[c]; candidate != -1)
                fail_to = static_cast<size_t>(candidate);
 
              nodes_[child].fail = static_cast<int>(fail_to);
              nodes_[child].out_link =
                  nodes_[fail_to].output.is_empty() ?
                  nodes_[fail_to].out_link : static_cast<int>(fail_to);
 
              queue.append(child);
            }
        }
 
      built_ = true;
    }
 
    [[nodiscard]] Array<Match> search(const std::string_view text) const
    {
      ah_runtime_error_unless(built_)
        << "Aho_Corasick::search(): call build() before search()";
 
      Array<Match> matches;
      size_t state = 0;
 
      for (size_t i = 0; i < text.size(); ++i)
        {
          const unsigned char c = static_cast<unsigned char>(text[i]);
 
          while (state != 0 and nodes_[state].next[c] == -1)
            state = static_cast<size_t>(nodes_[state].fail);
 
          if (const int next_state = nodes_[state].next[c]; next_state != -1)
            state = static_cast<size_t>(next_state);
          else
            state = 0;
 
          size_t out_state = state;
          while (true)
            {
              const Array<size_t> & output = nodes_[out_state].output;
              for (size_t k = 0; k < output.size(); ++k)
                {
                  const size_t id = output[k];
                  matches.append(Match{i + 1 - patterns_[id].size(), id});
                }
 
              const int next_out = nodes_[out_state].out_link;
              if (next_out == -1)
                break;
              out_state = static_cast<size_t>(next_out);
            }
        }
 
      return matches;
    }
 
    [[nodiscard]] bool contains_any(const std::string_view text) const
    {
      ah_runtime_error_unless(built_)
        << "Aho_Corasick::contains_any(): call build() before search()";
 
      size_t state = 0;
      for (size_t i = 0; i < text.size(); ++i)
        {
          const unsigned char c = static_cast<unsigned char>(text[i]);
 
          while (state != 0 and nodes_[state].next[c] == -1)
            state = static_cast<size_t>(nodes_[state].fail);
 
          if (const int next_state = nodes_[state].next[c]; next_state != -1)
            state = static_cast<size_t>(next_state);
          else
            state = 0;
 
          if (not nodes_[state].output.is_empty())
            return true;
 
          if (nodes_[state].out_link != -1)
            return true;
        }
 
      return false;
    }
 
    [[nodiscard]] size_t pattern_count() const noexcept
    {
      return patterns_.size();
    }
 
    [[nodiscard]] bool is_built() const noexcept
    {
      return built_;
    }
 
    [[nodiscard]] const std::string &pattern(const size_t id) const
    {
      ah_out_of_range_error_if(id >= patterns_.size())
        << "Aho_Corasick::pattern(): id out of range";
      return patterns_[id];
    }
  };
} // namespace Aleph
 
# endif // AHO_CORASICK_H