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[EDIT] FILE: string_view

// Components for manipulating non-owning sequences of characters -*- C++ -*-

// Copyright (C) 2013-2018 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 experimental/string_view
 *  This is a TS C++ Library header.
 */

//
// N3762 basic_string_view library
//

#ifndef _GLIBCXX_EXPERIMENTAL_STRING_VIEW
#define _GLIBCXX_EXPERIMENTAL_STRING_VIEW 1

#pragma GCC system_header

#if __cplusplus >= 201402L

#include <string>
#include <limits>
#include <experimental/bits/lfts_config.h>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace experimental
{
inline namespace fundamentals_v1
{
#define __cpp_lib_experimental_string_view 201411

/**
   *  @class basic_string_view <experimental/string_view>
   *  @brief  A non-owning reference to a string.
   *
   *  @ingroup strings
   *  @ingroup sequences
   *  @ingroup experimental
   *
   *  @tparam _CharT  Type of character
   *  @tparam _Traits  Traits for character type, defaults to
   *                   char_traits<_CharT>.
   *
   *  A basic_string_view looks like this:
   *
   *  @code
   *    _CharT*    _M_str
   *    size_t     _M_len
   *  @endcode
   */
  template<typename _CharT, typename _Traits = std::char_traits<_CharT>>
    class basic_string_view
    {
    public:

// types
      using traits_type = _Traits;
      using value_type = _CharT;
      using pointer = const _CharT*;
      using const_pointer = const _CharT*;
      using reference = const _CharT&;
      using const_reference = const _CharT&;
      using const_iterator = const _CharT*;
      using iterator = const_iterator;
      using const_reverse_iterator = std::reverse_iterator<const_iterator>;
      using reverse_iterator = const_reverse_iterator;
      using size_type = size_t;
      using difference_type = ptrdiff_t;
      static constexpr size_type npos = size_type(-1);

// [string.view.cons], construct/copy

constexpr
      basic_string_view() noexcept
      : _M_len{0}, _M_str{nullptr}
      { }

constexpr basic_string_view(const basic_string_view&) noexcept = default;

template<typename _Allocator>
        basic_string_view(const basic_string<_CharT, _Traits,
			  _Allocator>& __str) noexcept
        : _M_len{__str.length()}, _M_str{__str.data()}
        { }

constexpr basic_string_view(const _CharT* __str)
      : _M_len{__str == nullptr ? 0 : traits_type::length(__str)},
	_M_str{__str}
      { }

constexpr basic_string_view(const _CharT* __str, size_type __len)
      : _M_len{__len},
        _M_str{__str}
      { }

basic_string_view&
      operator=(const basic_string_view&) noexcept = default;

// [string.view.iterators], iterators

constexpr const_iterator
      begin() const noexcept
      { return this->_M_str; }

constexpr const_iterator
      end() const noexcept
      { return this->_M_str + this->_M_len; }

constexpr const_iterator
      cbegin() const noexcept
      { return this->_M_str; }

constexpr const_iterator
      cend() const noexcept
      { return this->_M_str + this->_M_len; }

const_reverse_iterator
      rbegin() const noexcept
      { return const_reverse_iterator(this->end()); }

const_reverse_iterator
      rend() const noexcept
      { return const_reverse_iterator(this->begin()); }

const_reverse_iterator
      crbegin() const noexcept
      { return const_reverse_iterator(this->end()); }

const_reverse_iterator
      crend() const noexcept
      { return const_reverse_iterator(this->begin()); }

// [string.view.capacity], capacity

constexpr size_type
      size() const noexcept
      { return this->_M_len; }

constexpr size_type
      length() const noexcept
      { return _M_len; }

constexpr size_type
      max_size() const noexcept
      {
	return (npos - sizeof(size_type) - sizeof(void*))
		/ sizeof(value_type) / 4;
      }

constexpr bool
      empty() const noexcept
      { return this->_M_len == 0; }

// [string.view.access], element access

constexpr const _CharT&
      operator[](size_type __pos) const
      {
	__glibcxx_assert(__pos < this->_M_len);
	return *(this->_M_str + __pos);
      }

constexpr const _CharT&
      at(size_type __pos) const
      {
	return __pos < this->_M_len
	     ? *(this->_M_str + __pos)
	     : (__throw_out_of_range_fmt(__N("basic_string_view::at: __pos "
					     "(which is %zu) >= this->size() "
					     "(which is %zu)"),
					 __pos, this->size()),
		*this->_M_str);
      }

constexpr const _CharT&
      front() const
      {
	__glibcxx_assert(this->_M_len > 0);
	return *this->_M_str;
      }

constexpr const _CharT&
      back() const
      {
	__glibcxx_assert(this->_M_len > 0);
	return *(this->_M_str + this->_M_len - 1);
      }

constexpr const _CharT*
      data() const noexcept
      { return this->_M_str; }

// [string.view.modifiers], modifiers:

constexpr void
      remove_prefix(size_type __n)
      {
	__glibcxx_assert(this->_M_len >= __n);
	this->_M_str += __n;
	this->_M_len -= __n;
      }

constexpr void
      remove_suffix(size_type __n)
      { this->_M_len -= __n; }

constexpr void
      swap(basic_string_view& __sv) noexcept
      {
	auto __tmp = *this;
	*this = __sv;
	__sv = __tmp;
      }

// [string.view.ops], string operations:

template<typename _Allocator>
        explicit operator basic_string<_CharT, _Traits, _Allocator>() const
        {
	  return { this->_M_str, this->_M_len };
	}

template<typename _Allocator = std::allocator<_CharT>>
	basic_string<_CharT, _Traits, _Allocator>
	to_string(const _Allocator& __alloc = _Allocator()) const
	{
	  return { this->_M_str, this->_M_len, __alloc };
	}

size_type
      copy(_CharT* __str, size_type __n, size_type __pos = 0) const
      {
	__glibcxx_requires_string_len(__str, __n);
	if (__pos > this->_M_len)
	  __throw_out_of_range_fmt(__N("basic_string_view::copy: __pos "
				       "(which is %zu) > this->size() "
				       "(which is %zu)"),
				   __pos, this->size());
	size_type __rlen{std::min(__n, size_type{this->_M_len  - __pos})};
	for (auto __begin = this->_M_str + __pos,
	     __end = __begin + __rlen; __begin != __end;)
	  *__str++ = *__begin++;
	return __rlen;
      }

// [string.view.ops], string operations:

constexpr basic_string_view
      substr(size_type __pos = 0, size_type __n = npos) const
      {
	return __pos <= this->_M_len
	     ? basic_string_view{this->_M_str + __pos,
				std::min(__n, size_type{this->_M_len  - __pos})}
	     : (__throw_out_of_range_fmt(__N("basic_string_view::substr: __pos "
					     "(which is %zu) > this->size() "
					     "(which is %zu)"),
				     __pos, this->size()), basic_string_view{});
      }

constexpr int
      compare(basic_string_view __str) const noexcept
      {
	int __ret = traits_type::compare(this->_M_str, __str._M_str,
					 std::min(this->_M_len, __str._M_len));
	if (__ret == 0)
	  __ret = _S_compare(this->_M_len, __str._M_len);
	return __ret;
      }

constexpr int
      compare(size_type __pos1, size_type __n1, basic_string_view __str) const
      { return this->substr(__pos1, __n1).compare(__str); }

constexpr int
      compare(size_type __pos1, size_type __n1,
	      basic_string_view __str, size_type __pos2, size_type __n2) const
      { return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2)); }

constexpr int
      compare(const _CharT* __str) const noexcept
      { return this->compare(basic_string_view{__str}); }

constexpr int
      compare(size_type __pos1, size_type __n1, const _CharT* __str) const
      { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }

constexpr int
      compare(size_type __pos1, size_type __n1,
	      const _CharT* __str, size_type __n2) const
      {
	return this->substr(__pos1, __n1)
		   .compare(basic_string_view(__str, __n2));
      }

constexpr size_type
      find(basic_string_view __str, size_type __pos = 0) const noexcept
      { return this->find(__str._M_str, __pos, __str._M_len); }

constexpr size_type
      find(_CharT __c, size_type __pos=0) const noexcept;

constexpr size_type
      find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;

constexpr size_type
      find(const _CharT* __str, size_type __pos=0) const noexcept
      { return this->find(__str, __pos, traits_type::length(__str)); }

constexpr size_type
      rfind(basic_string_view __str, size_type __pos = npos) const noexcept
      { return this->rfind(__str._M_str, __pos, __str._M_len); }

constexpr size_type
      rfind(_CharT __c, size_type __pos = npos) const noexcept;

constexpr size_type
      rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;

constexpr size_type
      rfind(const _CharT* __str, size_type __pos = npos) const noexcept
      { return this->rfind(__str, __pos, traits_type::length(__str)); }

constexpr size_type
      find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
      { return this->find_first_of(__str._M_str, __pos, __str._M_len); }

constexpr size_type
      find_first_of(_CharT __c, size_type __pos = 0) const noexcept
      { return this->find(__c, __pos); }

constexpr size_type
      find_first_of(const _CharT* __str, size_type __pos, size_type __n) const;

constexpr size_type
      find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
      { return this->find_first_of(__str, __pos, traits_type::length(__str)); }

constexpr size_type
      find_last_of(basic_string_view __str,
		   size_type __pos = npos) const noexcept
      { return this->find_last_of(__str._M_str, __pos, __str._M_len); }

constexpr size_type
      find_last_of(_CharT __c, size_type __pos=npos) const noexcept
      { return this->rfind(__c, __pos); }

constexpr size_type
      find_last_of(const _CharT* __str, size_type __pos, size_type __n) const;

constexpr size_type
      find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
      { return this->find_last_of(__str, __pos, traits_type::length(__str)); }

constexpr size_type
      find_first_not_of(basic_string_view __str,
			size_type __pos = 0) const noexcept
      { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }

constexpr size_type
      find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;

constexpr size_type
      find_first_not_of(const _CharT* __str,
			size_type __pos, size_type __n) const;

constexpr size_type
      find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
      {
	return this->find_first_not_of(__str, __pos,
				       traits_type::length(__str));
      }

constexpr size_type
      find_last_not_of(basic_string_view __str,
		       size_type __pos = npos) const noexcept
      { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }

constexpr size_type
      find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;

constexpr size_type
      find_last_not_of(const _CharT* __str,
		       size_type __pos, size_type __n) const;

constexpr size_type
      find_last_not_of(const _CharT* __str,
		       size_type __pos = npos) const noexcept
      {
	return this->find_last_not_of(__str, __pos,
				      traits_type::length(__str));
      }

private:

static constexpr int
      _S_compare(size_type __n1, size_type __n2) noexcept
      {
	return difference_type(__n1 - __n2) > std::numeric_limits<int>::max()
	     ? std::numeric_limits<int>::max()
	     : difference_type(__n1 - __n2) < std::numeric_limits<int>::min()
	     ? std::numeric_limits<int>::min()
	     : static_cast<int>(difference_type(__n1 - __n2));
      }

size_t	    _M_len;
      const _CharT* _M_str;
    };

// [string.view.comparison], non-member basic_string_view comparison functions

namespace __detail
  {
    // Identity transform to create a non-deduced context, so that only one
    // argument participates in template argument deduction and the other
    // argument gets implicitly converted to the deduced type. See n3766.html.
    template<typename _Tp>
      using __idt = common_type_t<_Tp>;
  }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator==(basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.size() == __y.size() && __x.compare(__y) == 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator==(basic_string_view<_CharT, _Traits> __x,
               __detail::__idt<basic_string_view<_CharT, _Traits>> __y) noexcept
    { return __x.size() == __y.size() && __x.compare(__y) == 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator==(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.size() == __y.size() && __x.compare(__y) == 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator!=(basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return !(__x == __y); }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator!=(basic_string_view<_CharT, _Traits> __x,
               __detail::__idt<basic_string_view<_CharT, _Traits>> __y) noexcept
    { return !(__x == __y); }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator!=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return !(__x == __y); }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator< (basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) < 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator< (basic_string_view<_CharT, _Traits> __x,
               __detail::__idt<basic_string_view<_CharT, _Traits>> __y) noexcept
    { return __x.compare(__y) < 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator< (__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) < 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator> (basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) > 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator> (basic_string_view<_CharT, _Traits> __x,
               __detail::__idt<basic_string_view<_CharT, _Traits>> __y) noexcept
    { return __x.compare(__y) > 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator> (__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) > 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator<=(basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) <= 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator<=(basic_string_view<_CharT, _Traits> __x,
               __detail::__idt<basic_string_view<_CharT, _Traits>> __y) noexcept
    { return __x.compare(__y) <= 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator<=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) <= 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator>=(basic_string_view<_CharT, _Traits> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) >= 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator>=(basic_string_view<_CharT, _Traits> __x,
               __detail::__idt<basic_string_view<_CharT, _Traits>> __y) noexcept
    { return __x.compare(__y) >= 0; }

template<typename _CharT, typename _Traits>
    constexpr bool
    operator>=(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
               basic_string_view<_CharT, _Traits> __y) noexcept
    { return __x.compare(__y) >= 0; }

// [string.view.io], Inserters and extractors
  template<typename _CharT, typename _Traits>
    inline basic_ostream<_CharT, _Traits>&
    operator<<(basic_ostream<_CharT, _Traits>& __os,
	       basic_string_view<_CharT,_Traits> __str)
    { return __ostream_insert(__os, __str.data(), __str.size()); }

// basic_string_view typedef names

using string_view = basic_string_view<char>;
#ifdef _GLIBCXX_USE_WCHAR_T
  using wstring_view = basic_string_view<wchar_t>;
#endif
#ifdef _GLIBCXX_USE_C99_STDINT_TR1
  using u16string_view = basic_string_view<char16_t>;
  using u32string_view = basic_string_view<char32_t>;
#endif
} // namespace fundamentals_v1
} // namespace experimental

// [string.view.hash], hash support:
  template<typename _Tp>
    struct hash;

template<>
    struct hash<experimental::string_view>
    : public __hash_base<size_t, experimental::string_view>
    {
      size_t
      operator()(const experimental::string_view& __str) const noexcept
      { return std::_Hash_impl::hash(__str.data(), __str.length()); }
    };

template<>
    struct __is_fast_hash<hash<experimental::string_view>> : std::false_type
    { };

#ifdef _GLIBCXX_USE_WCHAR_T
  template<>
    struct hash<experimental::wstring_view>
    : public __hash_base<size_t, wstring>
    {
      size_t
      operator()(const experimental::wstring_view& __s) const noexcept
      { return std::_Hash_impl::hash(__s.data(),
                                     __s.length() * sizeof(wchar_t)); }
    };

template<>
    struct __is_fast_hash<hash<experimental::wstring_view>> : std::false_type
    { };
#endif

#ifdef _GLIBCXX_USE_C99_STDINT_TR1
  template<>
    struct hash<experimental::u16string_view>
    : public __hash_base<size_t, experimental::u16string_view>
    {
      size_t
      operator()(const experimental::u16string_view& __s) const noexcept
      { return std::_Hash_impl::hash(__s.data(),
                                     __s.length() * sizeof(char16_t)); }
    };

template<>
    struct __is_fast_hash<hash<experimental::u16string_view>> : std::false_type
    { };

template<>
    struct hash<experimental::u32string_view>
    : public __hash_base<size_t, experimental::u32string_view>
    {
      size_t
      operator()(const experimental::u32string_view& __s) const noexcept
      { return std::_Hash_impl::hash(__s.data(),
                                     __s.length() * sizeof(char32_t)); }
    };

template<>
    struct __is_fast_hash<hash<experimental::u32string_view>> : std::false_type
    { };
#endif

namespace experimental
{
  // I added these EMSR.
  inline namespace literals
  {
  inline namespace string_view_literals
  {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wliteral-suffix"
    inline constexpr basic_string_view<char>
    operator""sv(const char* __str, size_t __len) noexcept
    { return basic_string_view<char>{__str, __len}; }

#ifdef _GLIBCXX_USE_WCHAR_T
    inline constexpr basic_string_view<wchar_t>
    operator""sv(const wchar_t* __str, size_t __len) noexcept
    { return basic_string_view<wchar_t>{__str, __len}; }
#endif

#ifdef _GLIBCXX_USE_C99_STDINT_TR1
    inline constexpr basic_string_view<char16_t>
    operator""sv(const char16_t* __str, size_t __len) noexcept
    { return basic_string_view<char16_t>{__str, __len}; }

inline constexpr basic_string_view<char32_t>
    operator""sv(const char32_t* __str, size_t __len) noexcept
    { return basic_string_view<char32_t>{__str, __len}; }
#endif
#pragma GCC diagnostic pop
  } // namespace string_literals
  } // namespace literals
} // namespace experimental

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#include <experimental/bits/string_view.tcc>

#endif // __cplusplus <= 201103L

#endif // _GLIBCXX_EXPERIMENTAL_STRING_VIEW

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