regex_compiler.h

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// class template regex -*- C++ -*-
 
// Copyright (C) 2010-2026 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.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{regex}
 */
 
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_BEGIN_NAMESPACE_CXX11
 
  template<typename>
    class regex_traits;
 
_GLIBCXX_END_NAMESPACE_CXX11
 
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
namespace __detail
{
  /**
   * @addtogroup regex-detail
   * @{
   */
 
  template<typename, bool, bool>
    struct _BracketMatcher;
 
  /**
   * @brief Builds an NFA from an input iterator range.
   *
   * The %_TraitsT type should fulfill the requirements in C++11 28.3 [re.req].
   */
  template<typename _TraitsT>
    class _Compiler
    {
    public:
      typedef typename _TraitsT::char_type        _CharT;
      typedef _NFA<_TraitsT>                      _RegexT;
      typedef regex_constants::syntax_option_type _FlagT;
 
      _Compiler(const _CharT* __b, const _CharT* __e,
                const typename _TraitsT::locale_type& __traits, _FlagT __flags);
 
      shared_ptr<const _RegexT>
      _M_get_nfa() noexcept
      { return std::move(_M_nfa); }
 
    private:
      typedef _Scanner<_CharT>               _ScannerT;
      typedef typename _TraitsT::string_type _StringT;
      typedef typename _ScannerT::_TokenT    _TokenT;
      typedef _StateSeq<_TraitsT>            _StateSeqT;
      typedef std::stack<_StateSeqT>         _StackT;
      typedef std::ctype<_CharT>             _CtypeT;
 
      // accepts a specific token or returns false.
      bool
      _M_match_token(_TokenT __token);
 
      void
      _M_disjunction();
 
      void
      _M_alternative();
 
      bool
      _M_term();
 
      bool
      _M_assertion();
 
      bool
      _M_quantifier();
 
      bool
      _M_atom();
 
      bool
      _M_bracket_expression();
 
      template<bool __icase, bool __collate>
        void
        _M_insert_any_matcher_ecma();
 
      template<bool __icase, bool __collate>
        void
        _M_insert_any_matcher_posix();
 
      template<bool __icase, bool __collate>
        void
        _M_insert_char_matcher();
 
      template<bool __icase, bool __collate>
        void
        _M_insert_character_class_matcher();
 
      template<bool __icase, bool __collate>
        void
        _M_insert_bracket_matcher(bool __neg);
 
      // Cache of the last atom seen in a bracketed range expression.
      struct _BracketState
      {
        enum class _Type : char { _None, _Char, _Class } _M_type = _Type::_None;
        _CharT _M_char = _CharT();
 
        void
        set(_CharT __c) noexcept { _M_type = _Type::_Char; _M_char = __c; }
 
        _GLIBCXX_NODISCARD _CharT
        get() const noexcept { return _M_char; }
 
        void
        reset(_Type __t = _Type::_None) noexcept { _M_type = __t; }
 
        explicit operator bool() const noexcept
        { return _M_type != _Type::_None; }
 
        // Previous token was a single character.
        _GLIBCXX_NODISCARD bool
        _M_is_char() const noexcept { return _M_type == _Type::_Char; }
 
        // Previous token was a character class, equivalent class,
        // collating symbol etc.
        _GLIBCXX_NODISCARD bool
        _M_is_class() const noexcept { return _M_type == _Type::_Class; }
      };
 
      template<bool __icase, bool __collate>
        using _BracketMatcher
          = std::__detail::_BracketMatcher<_TraitsT, __icase, __collate>;
 
      // Returns true if successfully parsed one term and should continue
      // compiling a bracket expression.
      // Returns false if the compiler should move on.
      template<bool __icase, bool __collate>
        bool
        _M_expression_term(_BracketState& __last_char,
                           _BracketMatcher<__icase, __collate>& __matcher);
 
      int
      _M_cur_int_value(int __radix);
 
      bool
      _M_try_char();
 
      _StateSeqT
      _M_pop()
      {
        auto ret = _M_stack.top();
        _M_stack.pop();
        return ret;
      }
 
      static _FlagT
      _S_validate(_FlagT __f)
      {
        using namespace regex_constants;
        switch (__f & (ECMAScript|basic|extended|awk|grep|egrep))
          {
          case ECMAScript:
          case basic:
          case extended:
          case awk:
          case grep:
          case egrep:
            return __f;
          case _FlagT(0):
            return __f | ECMAScript;
          default:
            std::__throw_regex_error(_S_grammar, "conflicting grammar options");
          }
      }
 
      _FlagT              _M_flags;
      _ScannerT           _M_scanner;
      shared_ptr<_RegexT> _M_nfa;
      _StringT            _M_value;
      _StackT             _M_stack;
      const _TraitsT&     _M_traits;
      const _CtypeT&      _M_ctype;
    };
 
  // C++11 28.13 [re.grammar] p14
  template<typename _TraitsT, bool __icase, bool __collate>
    class _RegexTranslatorBase
    {
    public:
      typedef typename _TraitsT::char_type            _CharT;
      typedef typename _TraitsT::string_type          _StringT;
      typedef _StringT _StrTransT;
 
      explicit
      _RegexTranslatorBase(const _TraitsT& __traits)
      : _M_traits(__traits)
      { }
 
      _CharT
      _M_translate(_CharT __ch) const
      {
        if constexpr (__icase)
          return _M_traits.translate_nocase(__ch);
        else if constexpr (__collate)
          return _M_traits.translate(__ch);
        else
          return __ch;
      }
 
      _StrTransT
      _M_transform(_CharT __ch) const
      {
        _StrTransT __str(1, __ch);
        return _M_traits.transform(__str.begin(), __str.end());
      }
 
      // See LWG 523. It's not efficiently implementable when _TraitsT is not
      // std::regex_traits<>, and __collate is true. See specializations for
      // implementations of other cases.
      bool
      _M_match_range(const _StrTransT& __first, const _StrTransT& __last,
                     const _StrTransT& __s) const
      { return __first <= __s && __s <= __last; }
 
    protected:
      bool _M_in_range_icase(_CharT __first, _CharT __last, _CharT __ch) const
      {
        typedef std::ctype<_CharT> __ctype_type;
        const auto& __fctyp = use_facet<__ctype_type>(this->_M_traits.getloc());
        auto __lower = __fctyp.tolower(__ch);
        auto __upper = __fctyp.toupper(__ch);
        return (__first <= __lower && __lower <= __last)
          || (__first <= __upper && __upper <= __last);
      }
 
      const _TraitsT& _M_traits;
    };
 
  template<typename _TraitsT, bool __icase, bool __collate>
    class _RegexTranslator
    : public _RegexTranslatorBase<_TraitsT, __icase, __collate>
    {
    public:
      typedef _RegexTranslatorBase<_TraitsT, __icase, __collate> _Base;
      using _Base::_Base;
    };
 
  template<typename _TraitsT, bool __icase>
    class _RegexTranslator<_TraitsT, __icase, false>
    : public _RegexTranslatorBase<_TraitsT, __icase, false>
    {
    public:
      typedef _RegexTranslatorBase<_TraitsT, __icase, false> _Base;
      typedef typename _Base::_CharT _CharT;
      typedef _CharT _StrTransT;
 
      using _Base::_Base;
 
      _StrTransT
      _M_transform(_CharT __ch) const
      { return __ch; }
 
      bool
      _M_match_range(_CharT __first, _CharT __last, _CharT __ch) const
      {
        if constexpr (!__icase)
          return __first <= __ch && __ch <= __last;
        else
          return this->_M_in_range_icase(__first, __last, __ch);
      }
    };
 
  template<typename _CharType>
    class _RegexTranslator<std::regex_traits<_CharType>, true, true>
    : public _RegexTranslatorBase<std::regex_traits<_CharType>, true, true>
    {
    public:
      typedef _RegexTranslatorBase<std::regex_traits<_CharType>, true, true>
        _Base;
      typedef typename _Base::_CharT _CharT;
      typedef typename _Base::_StrTransT _StrTransT;
 
      using _Base::_Base;
 
      bool
      _M_match_range(const _StrTransT& __first, const _StrTransT& __last,
                     const _StrTransT& __str) const
      {
        __glibcxx_assert(__first.size() == 1);
        __glibcxx_assert(__last.size() == 1);
        __glibcxx_assert(__str.size() == 1);
        return this->_M_in_range_icase(__first[0], __last[0], __str[0]);
      }
    };
 
  template<typename _TraitsT>
    class _RegexTranslator<_TraitsT, false, false>
    {
    public:
      typedef typename _TraitsT::char_type _CharT;
      typedef _CharT                       _StrTransT;
 
      explicit
      _RegexTranslator(const _TraitsT&)
      { }
 
      _CharT
      _M_translate(_CharT __ch) const
      { return __ch; }
 
      _StrTransT
      _M_transform(_CharT __ch) const
      { return __ch; }
 
      bool
      _M_match_range(_CharT __first, _CharT __last, _CharT __ch) const
      { return __first <= __ch && __ch <= __last; }
    };
 
  template<typename _TraitsT, bool __is_ecma, bool __icase, bool __collate>
    struct _AnyMatcher;
 
  template<typename _TraitsT, bool __icase, bool __collate>
    struct _AnyMatcher<_TraitsT, false, __icase, __collate>
    {
      typedef _RegexTranslator<_TraitsT, __icase, __collate> _TransT;
      typedef typename _TransT::_CharT                       _CharT;
 
      explicit
      _AnyMatcher(const _TraitsT& __traits)
      : _M_translator(__traits)
      { }
 
      bool
      operator()(_CharT __ch) const
      {
        static auto __nul = _M_translator._M_translate('\0');
        return _M_translator._M_translate(__ch) != __nul;
      }
 
      _TransT _M_translator;
    };
 
  template<typename _TraitsT, bool __icase, bool __collate>
    struct _AnyMatcher<_TraitsT, true, __icase, __collate>
    {
      typedef _RegexTranslator<_TraitsT, __icase, __collate> _TransT;
      typedef typename _TransT::_CharT                       _CharT;
 
      explicit
      _AnyMatcher(const _TraitsT& __traits)
      : _M_translator(__traits)
      { }
 
      bool
      operator()(_CharT __ch) const
      {
        const auto __c = _M_translator._M_translate(__ch);
        if (__c == _M_translator._M_translate('\n'))
          return false;
        if (__c == _M_translator._M_translate('\r'))
          return false;
        if constexpr (!is_same<_CharT, char>::value)
          {
            if (__c == _M_translator._M_translate(u'\u2028')) // line sep
              return false;
            if (__c == _M_translator._M_translate(u'\u2029')) // para sep
              return false;
          }
        return true;
      }
 
      _TransT _M_translator;
    };
 
  template<typename _TraitsT, bool __icase, bool __collate>
    struct _CharMatcher
    {
      typedef _RegexTranslator<_TraitsT, __icase, __collate> _TransT;
      typedef typename _TransT::_CharT                       _CharT;
 
      _CharMatcher(_CharT __ch, const _TraitsT& __traits)
      : _M_translator(__traits), _M_ch(_M_translator._M_translate(__ch))
      { }
 
      bool
      operator()(_CharT __ch) const
      { return _M_ch == _M_translator._M_translate(__ch); }
 
      _TransT _M_translator;
      _CharT  _M_ch;
    };
 
  /// Matches a character range (bracket expression)
  template<typename _TraitsT, bool __icase, bool __collate>
    struct _BracketMatcher
    {
    public:
      typedef _RegexTranslator<_TraitsT, __icase, __collate> _TransT;
      typedef typename _TransT::_CharT                       _CharT;
      typedef typename _TransT::_StrTransT                   _StrTransT;
      typedef typename _TraitsT::string_type                 _StringT;
      typedef typename _TraitsT::char_class_type             _CharClassT;
 
    public:
      _BracketMatcher(bool __is_non_matching,
                      const _TraitsT& __traits)
      : _M_class_set(0), _M_translator(__traits), _M_traits(__traits),
      _M_is_non_matching(__is_non_matching)
      { }
 
      bool
      operator()(_CharT __ch) const
      {
        _GLIBCXX_DEBUG_ASSERT(_M_is_ready);
        if constexpr (_UseCache::value)
          if (!(__ch & 0x80)) [[__likely__]]
            return _M_cache[static_cast<_UnsignedCharT>(__ch)];
        return _M_apply(__ch);
      }
 
      void
      _M_add_char(_CharT __c)
      {
        _M_char_set.push_back(_M_translator._M_translate(__c));
        _GLIBCXX_DEBUG_ONLY(_M_is_ready = false);
      }
 
      _StringT
      _M_add_collate_element(const _StringT& __s)
      {
        auto __st = _M_traits.lookup_collatename(__s.data(),
                                                 __s.data() + __s.size());
        if (__st.empty())
          __throw_regex_error(regex_constants::error_collate,
                              "Invalid collate element.");
        _M_char_set.push_back(_M_translator._M_translate(__st[0]));
        _GLIBCXX_DEBUG_ONLY(_M_is_ready = false);
        return __st;
      }
 
      void
      _M_add_equivalence_class(const _StringT& __s)
      {
        auto __st = _M_traits.lookup_collatename(__s.data(),
                                                 __s.data() + __s.size());
        if (__st.empty())
          __throw_regex_error(regex_constants::error_collate,
                              "Invalid equivalence class.");
        __st = _M_traits.transform_primary(__st.data(),
                                           __st.data() + __st.size());
        _M_equiv_set.push_back(__st);
        _GLIBCXX_DEBUG_ONLY(_M_is_ready = false);
      }
 
      // __neg should be true for \D, \S and \W only.
      void
      _M_add_character_class(const _StringT& __s, bool __neg)
      {
        auto __mask = _M_traits.lookup_classname(__s.data(),
                                                 __s.data() + __s.size(),
                                                 __icase);
        if (__mask == 0)
          __throw_regex_error(regex_constants::error_collate,
                              "Invalid character class.");
        if (!__neg)
          _M_class_set |= __mask;
        else
          _M_neg_class_set.push_back(__mask);
        _GLIBCXX_DEBUG_ONLY(_M_is_ready = false);
      }
 
      void
      _M_make_range(_CharT __l, _CharT __r)
      {
        if (__l > __r)
          __throw_regex_error(regex_constants::error_range,
                              "Invalid range in bracket expression.");
        _M_range_set.push_back(make_pair(_M_translator._M_transform(__l),
                                         _M_translator._M_transform(__r)));
        _GLIBCXX_DEBUG_ONLY(_M_is_ready = false);
      }
 
      void
      _M_ready()
      {
        std::sort(_M_char_set.begin(), _M_char_set.end());
        auto __end = std::unique(_M_char_set.begin(), _M_char_set.end());
        _M_char_set.erase(__end, _M_char_set.end());
        if constexpr (_UseCache::value)
          for (unsigned __i = 0; __i < 128; __i++) // Only cache 7-bit chars
            _M_cache[__i] = _M_apply(static_cast<_CharT>(__i));
        _GLIBCXX_DEBUG_ONLY(_M_is_ready = true);
      }
 
    private:
      // Currently we only use the cache for char
      using _UseCache = typename std::is_same<_CharT, char>::type;
 
      static constexpr size_t
      _S_cache_size =
        1ul << (sizeof(_CharT) * __CHAR_BIT__ * int(_UseCache::value));
 
      struct _Dummy { };
      using _CacheT = std::__conditional_t<_UseCache::value,
                                           std::bitset<_S_cache_size>,
                                           _Dummy>;
      using _UnsignedCharT = typename std::make_unsigned<_CharT>::type;
 
      bool
      _M_apply(_CharT __ch) const;
 
    private:
      _GLIBCXX_STD_C::vector<_CharT>            _M_char_set;
      _GLIBCXX_STD_C::vector<_StringT>          _M_equiv_set;
      _GLIBCXX_STD_C::vector<pair<_StrTransT, _StrTransT>> _M_range_set;
      _GLIBCXX_STD_C::vector<_CharClassT>       _M_neg_class_set;
      _CharClassT                               _M_class_set;
      _TransT                                   _M_translator;
      const _TraitsT&                           _M_traits;
      bool                                      _M_is_non_matching;
      _CacheT                                   _M_cache;
#ifdef _GLIBCXX_DEBUG
      bool                                      _M_is_ready = false;
#endif
    };
 
 ///@} regex-detail
} // namespace __detail
#pragma GCC diagnostic pop
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
 
#include <bits/regex_compiler.tcc>