regex-pattern-list-matcher.cpp

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013-2021 Regents of the University of California.
 *
 * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
 *
 * ndn-cxx library is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later version.
 *
 * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
 *
 * You should have received copies of the GNU General Public License and GNU Lesser
 * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
 *
 * @author Yingdi Yu <http://irl.cs.ucla.edu/~yingdi/>
 */

#include "ndn-cxx/util/regex/regex-pattern-list-matcher.hpp"
#include "ndn-cxx/util/regex/regex-backref-matcher.hpp"
#include "ndn-cxx/util/regex/regex-repeat-matcher.hpp"

namespace ndn {

RegexPatternListMatcher::RegexPatternListMatcher(const std::string& expr,
                                                 shared_ptr<RegexBackrefManager> backrefManager)
  : RegexMatcher(expr, EXPR_PATTERN_LIST, std::move(backrefManager))
{
  compile();
}

void
RegexPatternListMatcher::compile()
{
  size_t len = m_expr.size();
  size_t index = 0;
  size_t subHead = index;

  while (index < len) {
    subHead = index;

    if (!extractPattern(subHead, &index))
      NDN_THROW(Error("Compile error"));
  }
}

bool
RegexPatternListMatcher::extractPattern(size_t index, size_t* next)
{
  size_t start = index;
  size_t end = index;
  size_t indicator = index;

  switch (m_expr[index]) {
  case '(':
    index++;
    index = extractSubPattern('(', ')', index);
    indicator = index;
    end = extractRepetition(index);
    if (indicator == end) {
      auto matcher = make_shared<RegexBackrefMatcher>(m_expr.substr(start, end - start),
                                                      m_backrefManager);
      m_backrefManager->pushRef(matcher);
      matcher->compile();
      m_matchers.push_back(std::move(matcher));
    }
    else {
      m_matchers.push_back(make_shared<RegexRepeatMatcher>(m_expr.substr(start, end - start),
                                                           m_backrefManager, indicator - start));
    }
    break;

  case '<':
    index++;
    index = extractSubPattern('<', '>', index);
    indicator = index;
    end = extractRepetition(index);
    m_matchers.push_back(make_shared<RegexRepeatMatcher>(m_expr.substr(start, end - start),
                                                         m_backrefManager, indicator - start));
    break;

  case '[':
    index++;
    index = extractSubPattern('[', ']', index);
    indicator = index;
    end = extractRepetition(index);
    m_matchers.push_back(make_shared<RegexRepeatMatcher>(m_expr.substr(start, end - start),
                                                         m_backrefManager, indicator - start));
    break;

  default:
    NDN_THROW(Error("Unexpected character "s + m_expr[index]));
  }

  *next = end;
  return true;
}

size_t
RegexPatternListMatcher::extractSubPattern(const char left, const char right, size_t index)
{
  size_t lcount = 1;
  size_t rcount = 0;

  while (lcount > rcount) {
    if (index >= m_expr.size())
      NDN_THROW(Error("Parenthesis mismatch"));

    if (left == m_expr[index])
      lcount++;

    if (right == m_expr[index])
      rcount++;

    index++;
  }

  return index;
}

size_t
RegexPatternListMatcher::extractRepetition(size_t index)
{
  size_t exprSize = m_expr.size();

  if (index == exprSize)
    return index;

  if (('+' == m_expr[index] || '?' == m_expr[index] || '*' == m_expr[index])) {
    return ++index;
  }

  if ('{' == m_expr[index]) {
    while ('}' != m_expr[index]) {
      index++;
      if (index == exprSize)
        break;
    }
    if (index == exprSize)
      NDN_THROW(Error("Missing closing brace"));
    else
      return ++index;
  }
  else {
    return index;
  }
}

} // namespace ndn