regex_compiler.tcc

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// class template regex -*- C++ -*-
 
// Copyright (C) 2013-2025 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
 
// This 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 General Public License for more details.
 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
 
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.
 
/**
 *  @file bits/regex_compiler.tcc
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{regex}
 */
 
// FIXME make comments doxygen format.
 
/*
// This compiler refers to "Regular Expression Matching Can Be Simple And Fast"
// (http://swtch.com/~rsc/regexp/regexp1.html),
// but doesn't strictly follow it.
//
// When compiling, states are *chained* instead of tree- or graph-constructed.
// It's more like structured programs: there's if statement and loop statement.
//
// For alternative structure (say "a|b"), aka "if statement", two branches
// should be constructed. However, these two shall merge to an "end_tag" at
// the end of this operator:
//
//                branch1
//              /        \
// => begin_tag            end_tag =>
//              \        /
//                branch2
//
// This is the difference between this implementation and that in Russ's
// article.
//
// That's why we introduced dummy node here ------ "end_tag" is a dummy node.
// All dummy nodes will be eliminated at the end of compilation.
*/
 
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++20-extensions" // variadic macro with 0 args
 
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
 
namespace __detail
{
  template<typename _TraitsT>
    _Compiler<_TraitsT>::
    _Compiler(const _CharT* __b, const _CharT* __e,
              const typename _TraitsT::locale_type& __loc, _FlagT __flags)
    : _M_flags(_S_validate(__flags)),
      _M_scanner(__b, __e, _M_flags, __loc),
      _M_nfa(make_shared<_RegexT>(__loc, _M_flags)),
      _M_traits(_M_nfa->_M_traits),
      _M_ctype(std::use_facet<_CtypeT>(__loc))
    {
      _StateSeqT __r(*_M_nfa, _M_nfa->_M_start());
      __r._M_append(_M_nfa->_M_insert_subexpr_begin());
      this->_M_disjunction();
      if (!_M_match_token(_ScannerT::_S_token_eof))
        __throw_regex_error(regex_constants::error_paren);
      __r._M_append(_M_pop());
      __glibcxx_assert(_M_stack.empty());
      __r._M_append(_M_nfa->_M_insert_subexpr_end());
      __r._M_append(_M_nfa->_M_insert_accept());
      _M_nfa->_M_eliminate_dummy();
    }
 
  template<typename _TraitsT>
    void
    _Compiler<_TraitsT>::
    _M_disjunction()
    {
      this->_M_alternative();
      while (_M_match_token(_ScannerT::_S_token_or))
        {
          _StateSeqT __alt1 = _M_pop();
          this->_M_alternative();
          _StateSeqT __alt2 = _M_pop();
          auto __end = _M_nfa->_M_insert_dummy();
          __alt1._M_append(__end);
          __alt2._M_append(__end);
          // __alt2 is state._M_next, __alt1 is state._M_alt. The executor
          // executes _M_alt before _M_next, as well as executing left
          // alternative before right one.
          _M_stack.push(_StateSeqT(*_M_nfa,
                                   _M_nfa->_M_insert_alt(
                                     __alt2._M_start, __alt1._M_start, false),
                                   __end));
        }
    }
 
  template<typename _TraitsT>
    void
    _Compiler<_TraitsT>::
    _M_alternative()
    {
      if (this->_M_term())
        {
          _StateSeqT __re = _M_pop();
          this->_M_alternative();
          __re._M_append(_M_pop());
          _M_stack.push(__re);
        }
      else
        _M_stack.push(_StateSeqT(*_M_nfa, _M_nfa->_M_insert_dummy()));
    }
 
  template<typename _TraitsT>
    bool
    _Compiler<_TraitsT>::
    _M_term()
    {
      if (this->_M_assertion())
        return true;
      if (this->_M_atom())
        {
          while (this->_M_quantifier())
            ;
          return true;
        }
      return false;
    }
 
  template<typename _TraitsT>
    bool
    _Compiler<_TraitsT>::
    _M_assertion()
    {
      if (_M_match_token(_ScannerT::_S_token_line_begin))
        _M_stack.push(_StateSeqT(*_M_nfa, _M_nfa->_M_insert_line_begin()));
      else if (_M_match_token(_ScannerT::_S_token_line_end))
        _M_stack.push(_StateSeqT(*_M_nfa, _M_nfa->_M_insert_line_end()));
      else if (_M_match_token(_ScannerT::_S_token_word_bound))
        // _M_value[0] == 'n' means it's negative, say "not word boundary".
        _M_stack.push(_StateSeqT(*_M_nfa, _M_nfa->
              _M_insert_word_bound(_M_value[0] == 'n')));
      else if (_M_match_token(_ScannerT::_S_token_subexpr_lookahead_begin))
        {
          auto __neg = _M_value[0] == 'n';
          this->_M_disjunction();
          if (!_M_match_token(_ScannerT::_S_token_subexpr_end))
            __throw_regex_error(regex_constants::error_paren);
          auto __tmp = _M_pop();
          __tmp._M_append(_M_nfa->_M_insert_accept());
          _M_stack.push(
              _StateSeqT(
                *_M_nfa,
                _M_nfa->_M_insert_lookahead(__tmp._M_start, __neg)));
        }
      else
        return false;
      return true;
    }
 
  template<typename _TraitsT>
    bool
    _Compiler<_TraitsT>::
    _M_quantifier()
    {
      bool __neg = (_M_flags & regex_constants::ECMAScript);
      auto __init = [this, &__neg]()
        {
          if (_M_stack.empty())
            __throw_regex_error(regex_constants::error_badrepeat);
          __neg = __neg && _M_match_token(_ScannerT::_S_token_opt);
        };
      if (_M_match_token(_ScannerT::_S_token_closure0))
        {
          __init();
          auto __e = _M_pop();
          _StateSeqT __r(*_M_nfa,
                         _M_nfa->_M_insert_repeat(_S_invalid_state_id,
                                                  __e._M_start, __neg));
          __e._M_append(__r);
          _M_stack.push(__r);
        }
      else if (_M_match_token(_ScannerT::_S_token_closure1))
        {
          __init();
          auto __e = _M_pop();
          __e._M_append(_M_nfa->_M_insert_repeat(_S_invalid_state_id,
                                                 __e._M_start, __neg));
          _M_stack.push(__e);
        }
      else if (_M_match_token(_ScannerT::_S_token_opt))
        {
          __init();
          auto __e = _M_pop();
          auto __end = _M_nfa->_M_insert_dummy();
          _StateSeqT __r(*_M_nfa,
                         _M_nfa->_M_insert_repeat(_S_invalid_state_id,
                                                  __e._M_start, __neg));
          __e._M_append(__end);
          __r._M_append(__end);
          _M_stack.push(__r);
        }
      else if (_M_match_token(_ScannerT::_S_token_interval_begin))
        {
          if (_M_stack.empty())
            __throw_regex_error(regex_constants::error_badrepeat);
          if (!_M_match_token(_ScannerT::_S_token_dup_count))
            __throw_regex_error(regex_constants::error_badbrace);
          _StateSeqT __r(_M_pop());
          _StateSeqT __e(*_M_nfa, _M_nfa->_M_insert_dummy());
          long __min_rep = _M_cur_int_value(10);
          bool __infi = false;
          long __n = 0;
 
          // {3
          if (_M_match_token(_ScannerT::_S_token_comma))
            {
              if (_M_match_token(_ScannerT::_S_token_dup_count)) // {3,7}
                __n = _M_cur_int_value(10) - __min_rep;
              else
                __infi = true;
            }
          if (!_M_match_token(_ScannerT::_S_token_interval_end))
            __throw_regex_error(regex_constants::error_brace);
 
          __neg = __neg && _M_match_token(_ScannerT::_S_token_opt);
 
          for (long __i = 0; __i < __min_rep; ++__i)
            __e._M_append(__r._M_clone());
 
          if (__infi)
            {
              auto __tmp = __r._M_clone();
              _StateSeqT __s(*_M_nfa,
                             _M_nfa->_M_insert_repeat(_S_invalid_state_id,
                                                      __tmp._M_start, __neg));
              __tmp._M_append(__s);
              __e._M_append(__s);
            }
          else
            {
              if (__n < 0)
                __throw_regex_error(regex_constants::error_badbrace);
              auto __end = _M_nfa->_M_insert_dummy();
              // _M_alt is the "match more" branch, and _M_next is the
              // "match less" one. Switch _M_alt and _M_next of all created
              // nodes. This is a hack but IMO works well.
              std::stack<_StateIdT> __stack;
              for (long __i = 0; __i < __n; ++__i)
                {
                  auto __tmp = __r._M_clone();
                  auto __alt = _M_nfa->_M_insert_repeat(__tmp._M_start,
                                                        __end, __neg);
                  __stack.push(__alt);
                  __e._M_append(_StateSeqT(*_M_nfa, __alt, __tmp._M_end));
                }
              __e._M_append(__end);
              while (!__stack.empty())
                {
                  auto& __tmp = (*_M_nfa)[__stack.top()];
                  __stack.pop();
                  std::swap(__tmp._M_next, __tmp._M_alt);
                }
            }
          _M_stack.push(__e);
        }
      else
        return false;
      return true;
    }
 
#define __INSERT_REGEX_MATCHER(__func, ...)\
        do {\
          if (!(_M_flags & regex_constants::icase))\
            if (!(_M_flags & regex_constants::collate))\
              __func<false, false>(__VA_ARGS__);\
            else\
              __func<false, true>(__VA_ARGS__);\
          else\
            if (!(_M_flags & regex_constants::collate))\
              __func<true, false>(__VA_ARGS__);\
            else\
              __func<true, true>(__VA_ARGS__);\
        } while (false)
 
  template<typename _TraitsT>
    bool
    _Compiler<_TraitsT>::
    _M_atom()
    {
      if (_M_match_token(_ScannerT::_S_token_anychar))
        {
          if (!(_M_flags & regex_constants::ECMAScript))
            __INSERT_REGEX_MATCHER(_M_insert_any_matcher_posix);
          else
            __INSERT_REGEX_MATCHER(_M_insert_any_matcher_ecma);
        }
      else if (_M_try_char())
        __INSERT_REGEX_MATCHER(_M_insert_char_matcher);
      else if (_M_match_token(_ScannerT::_S_token_backref))
        _M_stack.push(_StateSeqT(*_M_nfa, _M_nfa->
                                 _M_insert_backref(_M_cur_int_value(10))));
      else if (_M_match_token(_ScannerT::_S_token_quoted_class))
        __INSERT_REGEX_MATCHER(_M_insert_character_class_matcher);
      else if (_M_match_token(_ScannerT::_S_token_subexpr_no_group_begin))
        {
          _StateSeqT __r(*_M_nfa, _M_nfa->_M_insert_dummy());
          this->_M_disjunction();
          if (!_M_match_token(_ScannerT::_S_token_subexpr_end))
            __throw_regex_error(regex_constants::error_paren);
          __r._M_append(_M_pop());
          _M_stack.push(__r);
        }
      else if (_M_match_token(_ScannerT::_S_token_subexpr_begin))
        {
          _StateSeqT __r(*_M_nfa, _M_nfa->_M_insert_subexpr_begin());
          this->_M_disjunction();
          if (!_M_match_token(_ScannerT::_S_token_subexpr_end))
            __throw_regex_error(regex_constants::error_paren);
          __r._M_append(_M_pop());
          __r._M_append(_M_nfa->_M_insert_subexpr_end());
          _M_stack.push(__r);
        }
      else if (!_M_bracket_expression())
        return false;
      return true;
    }
 
  template<typename _TraitsT>
    bool
    _Compiler<_TraitsT>::
    _M_bracket_expression()
    {
      bool __neg =
        _M_match_token(_ScannerT::_S_token_bracket_neg_begin);
      if (!(__neg || _M_match_token(_ScannerT::_S_token_bracket_begin)))
        return false;
      __INSERT_REGEX_MATCHER(_M_insert_bracket_matcher, __neg);
      return true;
    }
#undef __INSERT_REGEX_MATCHER
 
  template<typename _TraitsT>
  template<bool __icase, bool __collate>
    void
    _Compiler<_TraitsT>::
    _M_insert_any_matcher_ecma()
    {
      _M_stack.push(_StateSeqT(*_M_nfa,
        _M_nfa->_M_insert_matcher
          (_AnyMatcher<_TraitsT, true, __icase, __collate>
            (_M_traits))));
    }
 
  template<typename _TraitsT>
  template<bool __icase, bool __collate>
    void
    _Compiler<_TraitsT>::
    _M_insert_any_matcher_posix()
    {
      _M_stack.push(_StateSeqT(*_M_nfa,
        _M_nfa->_M_insert_matcher
          (_AnyMatcher<_TraitsT, false, __icase, __collate>
            (_M_traits))));
    }
 
  template<typename _TraitsT>
  template<bool __icase, bool __collate>
    void
    _Compiler<_TraitsT>::
    _M_insert_char_matcher()
    {
      _M_stack.push(_StateSeqT(*_M_nfa,
        _M_nfa->_M_insert_matcher
          (_CharMatcher<_TraitsT, __icase, __collate>
            (_M_value[0], _M_traits))));
    }
 
  template<typename _TraitsT>
  template<bool __icase, bool __collate>
    void
    _Compiler<_TraitsT>::
    _M_insert_character_class_matcher()
    {
      __glibcxx_assert(_M_value.size() == 1);
      _BracketMatcher<__icase, __collate> __matcher
        (_M_ctype.is(_CtypeT::upper, _M_value[0]), _M_traits);
      __matcher._M_add_character_class(_M_value, false);
      __matcher._M_ready();
      _M_stack.push(_StateSeqT(*_M_nfa,
        _M_nfa->_M_insert_matcher(std::move(__matcher))));
    }
 
  template<typename _TraitsT>
  template<bool __icase, bool __collate>
    void
    _Compiler<_TraitsT>::
    _M_insert_bracket_matcher(bool __neg)
    {
      _BracketMatcher<__icase, __collate> __matcher(__neg, _M_traits);
      _BracketState __last_char;
      if (_M_try_char())
        __last_char.set(_M_value[0]);
      else if (_M_match_token(_ScannerT::_S_token_bracket_dash))
        // Dash as first character is a normal character.
        __last_char.set('-');
      while (_M_expression_term(__last_char, __matcher))
        ;
      if (__last_char._M_is_char())
        __matcher._M_add_char(__last_char.get());
      __matcher._M_ready();
      _M_stack.push(_StateSeqT(
                      *_M_nfa,
                      _M_nfa->_M_insert_matcher(std::move(__matcher))));
    }
 
  template<typename _TraitsT>
  template<bool __icase, bool __collate>
    bool
    _Compiler<_TraitsT>::
    _M_expression_term(_BracketState& __last_char,
                       _BracketMatcher<__icase, __collate>& __matcher)
    {
      if (_M_match_token(_ScannerT::_S_token_bracket_end))
        return false;
 
      // Add any previously cached char into the matcher and update cache.
      const auto __push_char = [&](_CharT __ch)
      {
        if (__last_char._M_is_char())
          __matcher._M_add_char(__last_char.get());
        __last_char.set(__ch);
      };
      // Add any previously cached char into the matcher and update cache.
      const auto __push_class = [&]
      {
        if (__last_char._M_is_char())
          __matcher._M_add_char(__last_char.get());
        // We don't cache anything here, just record that the last thing
        // processed was a character class (or similar).
        __last_char.reset(_BracketState::_Type::_Class);
      };
 
      if (_M_match_token(_ScannerT::_S_token_collsymbol))
        {
          auto __symbol = __matcher._M_add_collate_element(_M_value);
          if (__symbol.size() == 1)
            __push_char(__symbol[0]);
          else
            __push_class();
        }
      else if (_M_match_token(_ScannerT::_S_token_equiv_class_name))
        {
          __push_class();
          __matcher._M_add_equivalence_class(_M_value);
        }
      else if (_M_match_token(_ScannerT::_S_token_char_class_name))
        {
          __push_class();
          __matcher._M_add_character_class(_M_value, false);
        }
      else if (_M_try_char())
        __push_char(_M_value[0]);
      // POSIX doesn't allow '-' as a start-range char (say [a-z--0]),
      // except when the '-' is the first or last character in the bracket
      // expression ([--0]). ECMAScript treats all '-' after a range as a
      // normal character. Also see above, where _M_expression_term gets called.
      //
      // As a result, POSIX rejects [-----], but ECMAScript doesn't.
      // Boost (1.57.0) always uses POSIX style even in its ECMAScript syntax.
      // Clang (3.5) always uses ECMAScript style even in its POSIX syntax.
      //
      // It turns out that no one reads BNFs ;)
      else if (_M_match_token(_ScannerT::_S_token_bracket_dash))
        {
          if (_M_match_token(_ScannerT::_S_token_bracket_end))
            {
              // For "-]" the dash is a literal character.
              __push_char('-');
              return false;
            }
          else if (__last_char._M_is_class())
            {
              // "\\w-" is invalid, start of range must be a single char.
              __throw_regex_error(regex_constants::error_range,
                                  "Invalid start of '[x-x]' range in "
                                  "regular expression");
            }
          else if (__last_char._M_is_char())
            {
              if (_M_try_char())
                {
                  // "x-y"
                  __matcher._M_make_range(__last_char.get(), _M_value[0]);
                  __last_char.reset();
                }
              else if (_M_match_token(_ScannerT::_S_token_bracket_dash))
                {
                  // "x--"
                  __matcher._M_make_range(__last_char.get(), '-');
                  __last_char.reset();
                }
              else
                __throw_regex_error(regex_constants::error_range,
                                    "Invalid end of '[x-x]' range in "
                                    "regular expression");
            }
          else if (_M_flags & regex_constants::ECMAScript)
            {
              // A dash that is not part of an existing range. Might be the
              // start of a new range, or might just be a literal '-' char.
              // Only ECMAScript allows that in the middle of a bracket expr.
              __push_char('-');
            }
          else
            __throw_regex_error(regex_constants::error_range,
                                "Invalid location of '-' within '[...]' in "
                                "POSIX regular expression");
        }
      else if (_M_match_token(_ScannerT::_S_token_quoted_class))
        {
          __push_class();
          __matcher._M_add_character_class(_M_value,
                                           _M_ctype.is(_CtypeT::upper,
                                                       _M_value[0]));
        }
      else
        __throw_regex_error(regex_constants::error_brack,
                            "Unexpected character within '[...]' in "
                            "regular expression");
      return true;
    }
 
  template<typename _TraitsT>
    bool
    _Compiler<_TraitsT>::
    _M_try_char()
    {
      bool __is_char = false;
      if (_M_match_token(_ScannerT::_S_token_oct_num))
        {
          __is_char = true;
          _M_value.assign(1, _M_cur_int_value(8));
        }
      else if (_M_match_token(_ScannerT::_S_token_hex_num))
        {
          __is_char = true;
          _M_value.assign(1, _M_cur_int_value(16));
        }
      else if (_M_match_token(_ScannerT::_S_token_ord_char))
        __is_char = true;
      return __is_char;
    }
 
  template<typename _TraitsT>
    bool
    _Compiler<_TraitsT>::
    _M_match_token(_TokenT __token)
    {
      if (__token == _M_scanner._M_get_token())
        {
          _M_value = _M_scanner._M_get_value();
          _M_scanner._M_advance();
          return true;
        }
      return false;
    }
 
  template<typename _TraitsT>
    int
    _Compiler<_TraitsT>::
    _M_cur_int_value(int __radix)
    {
      int __v = 0;
      for (_CharT __c : _M_value)
        if (__builtin_mul_overflow(__v, __radix, &__v)
            || __builtin_add_overflow(__v, _M_traits.value(__c, __radix), &__v))
            std::__throw_regex_error(regex_constants::error_backref,
                                     "invalid back reference");
      return __v;
    }
 
  template<typename _TraitsT, bool __icase, bool __collate>
    bool
    _BracketMatcher<_TraitsT, __icase, __collate>::
    _M_apply(_CharT __ch) const
    {
      return [this, __ch]
      {
        if (std::binary_search(_M_char_set.begin(), _M_char_set.end(),
                               _M_translator._M_translate(__ch)))
          return true;
        auto __s = _M_translator._M_transform(__ch);
        for (auto& __it : _M_range_set)
          if (_M_translator._M_match_range(__it.first, __it.second, __s))
            return true;
        if (_M_traits.isctype(__ch, _M_class_set))
          return true;
        if (!_M_equiv_set.empty())
          {
            auto __x = _M_traits.transform_primary(&__ch, &__ch+1);
            auto __p = std::find(_M_equiv_set.begin(), _M_equiv_set.end(), __x);
            if (__p != _M_equiv_set.end())
              return true;
          }
        for (auto& __it : _M_neg_class_set)
          if (!_M_traits.isctype(__ch, __it))
            return true;
        return false;
      }() ^ _M_is_non_matching;
    }
} // namespace __detail
 
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
 
#pragma GCC diagnostic pop