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gcc/libstdc++-v3/include/bits/char_traits.h
Jonathan Wakely 8c3b5c719f Implement P0426R1 "Constexpr for std::char_traits" for C++17 (partial) 
* include/bits/char_traits.h (__gnu_cxx::char_traits): Add
	_GLIBCXX14_CONSTEXPR on assign, compare, find, and length.
	(std::char_traits<char>, std::char_traits<wchar_t>): Add
	_GLIBCXX17_CONSTEXPR on assign.
	(std::char_traits<char16_t>, std::char_traits<char32_t>): Add
	_GLIBCXX17_CONSTEXPR on assign, compare, find, and length.
	* testsuite/21_strings/char_traits/requirements/
	constexpr_functions_c++17.cc: New test.

From-SVN: r246655
2017-04-03 18:15:53 +01:00

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// Character Traits for use by standard string and iostream -*- C++ -*-
// Copyright (C) 1997-2017 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/char_traits.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{string}
*/
//
// ISO C++ 14882: 21 Strings library
//
#ifndef _CHAR_TRAITS_H
#define _CHAR_TRAITS_H 1
#pragma GCC system_header
#include <bits/stl_algobase.h> // std::copy, std::fill_n
#include <bits/postypes.h> // For streampos
#include <cwchar> // For WEOF, wmemmove, wmemset, etc.
namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @brief Mapping from character type to associated types.
*
* @note This is an implementation class for the generic version
* of char_traits. It defines int_type, off_type, pos_type, and
* state_type. By default these are unsigned long, streamoff,
* streampos, and mbstate_t. Users who need a different set of
* types, but who don't need to change the definitions of any function
* defined in char_traits, can specialize __gnu_cxx::_Char_types
* while leaving __gnu_cxx::char_traits alone. */
template<typename _CharT>
struct _Char_types
{
typedef unsigned long int_type;
typedef std::streampos pos_type;
typedef std::streamoff off_type;
typedef std::mbstate_t state_type;
};
/**
* @brief Base class used to implement std::char_traits.
*
* @note For any given actual character type, this definition is
* probably wrong. (Most of the member functions are likely to be
* right, but the int_type and state_type typedefs, and the eof()
* member function, are likely to be wrong.) The reason this class
* exists is so users can specialize it. Classes in namespace std
* may not be specialized for fundamental types, but classes in
* namespace __gnu_cxx may be.
*
* See https://gcc.gnu.org/onlinedocs/libstdc++/manual/strings.html#strings.string.character_types
* for advice on how to make use of this class for @a unusual character
* types. Also, check out include/ext/pod_char_traits.h.
*/
template<typename _CharT>
struct char_traits
{
typedef _CharT char_type;
typedef typename _Char_types<_CharT>::int_type int_type;
typedef typename _Char_types<_CharT>::pos_type pos_type;
typedef typename _Char_types<_CharT>::off_type off_type;
typedef typename _Char_types<_CharT>::state_type state_type;
static _GLIBCXX14_CONSTEXPR void
assign(char_type& __c1, const char_type& __c2)
{ __c1 = __c2; }
static _GLIBCXX_CONSTEXPR bool
eq(const char_type& __c1, const char_type& __c2)
{ return __c1 == __c2; }
static _GLIBCXX_CONSTEXPR bool
lt(const char_type& __c1, const char_type& __c2)
{ return __c1 < __c2; }
static _GLIBCXX14_CONSTEXPR int
compare(const char_type* __s1, const char_type* __s2, std::size_t __n);
static _GLIBCXX14_CONSTEXPR std::size_t
length(const char_type* __s);
static _GLIBCXX14_CONSTEXPR const char_type*
find(const char_type* __s, std::size_t __n, const char_type& __a);
static char_type*
move(char_type* __s1, const char_type* __s2, std::size_t __n);
static char_type*
copy(char_type* __s1, const char_type* __s2, std::size_t __n);
static char_type*
assign(char_type* __s, std::size_t __n, char_type __a);
static _GLIBCXX_CONSTEXPR char_type
to_char_type(const int_type& __c)
{ return static_cast<char_type>(__c); }
static _GLIBCXX_CONSTEXPR int_type
to_int_type(const char_type& __c)
{ return static_cast<int_type>(__c); }
static _GLIBCXX_CONSTEXPR bool
eq_int_type(const int_type& __c1, const int_type& __c2)
{ return __c1 == __c2; }
static _GLIBCXX_CONSTEXPR int_type
eof()
{ return static_cast<int_type>(_GLIBCXX_STDIO_EOF); }
static _GLIBCXX_CONSTEXPR int_type
not_eof(const int_type& __c)
{ return !eq_int_type(__c, eof()) ? __c : to_int_type(char_type()); }
};
// #define __cpp_lib_constexpr_char_traits 201611
template<typename _CharT>
_GLIBCXX14_CONSTEXPR int
char_traits<_CharT>::
compare(const char_type* __s1, const char_type* __s2, std::size_t __n)
{
for (std::size_t __i = 0; __i < __n; ++__i)
if (lt(__s1[__i], __s2[__i]))
return -1;
else if (lt(__s2[__i], __s1[__i]))
return 1;
return 0;
}
template<typename _CharT>
_GLIBCXX14_CONSTEXPR std::size_t
char_traits<_CharT>::
length(const char_type* __p)
{
std::size_t __i = 0;
while (!eq(__p[__i], char_type()))
++__i;
return __i;
}
template<typename _CharT>
_GLIBCXX14_CONSTEXPR const typename char_traits<_CharT>::char_type*
char_traits<_CharT>::
find(const char_type* __s, std::size_t __n, const char_type& __a)
{
for (std::size_t __i = 0; __i < __n; ++__i)
if (eq(__s[__i], __a))
return __s + __i;
return 0;
}
template<typename _CharT>
typename char_traits<_CharT>::char_type*
char_traits<_CharT>::
move(char_type* __s1, const char_type* __s2, std::size_t __n)
{
return static_cast<_CharT*>(__builtin_memmove(__s1, __s2,
__n * sizeof(char_type)));
}
template<typename _CharT>
typename char_traits<_CharT>::char_type*
char_traits<_CharT>::
copy(char_type* __s1, const char_type* __s2, std::size_t __n)
{
// NB: Inline std::copy so no recursive dependencies.
std::copy(__s2, __s2 + __n, __s1);
return __s1;
}
template<typename _CharT>
typename char_traits<_CharT>::char_type*
char_traits<_CharT>::
assign(char_type* __s, std::size_t __n, char_type __a)
{
// NB: Inline std::fill_n so no recursive dependencies.
std::fill_n(__s, __n, __a);
return __s;
}
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
// 21.1
/**
* @brief Basis for explicit traits specializations.
*
* @note For any given actual character type, this definition is
* probably wrong. Since this is just a thin wrapper around
* __gnu_cxx::char_traits, it is possible to achieve a more
* appropriate definition by specializing __gnu_cxx::char_traits.
*
* See https://gcc.gnu.org/onlinedocs/libstdc++/manual/strings.html#strings.string.character_types
* for advice on how to make use of this class for @a unusual character
* types. Also, check out include/ext/pod_char_traits.h.
*/
template<class _CharT>
struct char_traits : public __gnu_cxx::char_traits<_CharT>
{ };
/// 21.1.3.1 char_traits specializations
template<>
struct char_traits<char>
{
typedef char char_type;
typedef int int_type;
typedef streampos pos_type;
typedef streamoff off_type;
typedef mbstate_t state_type;
static _GLIBCXX17_CONSTEXPR void
assign(char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
{ __c1 = __c2; }
static _GLIBCXX_CONSTEXPR bool
eq(const char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
{ return __c1 == __c2; }
static _GLIBCXX_CONSTEXPR bool
lt(const char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
{
// LWG 467.
return (static_cast<unsigned char>(__c1)
< static_cast<unsigned char>(__c2));
}
static /* _GLIBCXX17_CONSTEXPR */ int
compare(const char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return 0;
return __builtin_memcmp(__s1, __s2, __n);
}
static /* _GLIBCXX17_CONSTEXPR */ size_t
length(const char_type* __s)
{ return __builtin_strlen(__s); }
static /* _GLIBCXX17_CONSTEXPR */ const char_type*
find(const char_type* __s, size_t __n, const char_type& __a)
{
if (__n == 0)
return 0;
return static_cast<const char_type*>(__builtin_memchr(__s, __a, __n));
}
static char_type*
move(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
return static_cast<char_type*>(__builtin_memmove(__s1, __s2, __n));
}
static char_type*
copy(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n));
}
static char_type*
assign(char_type* __s, size_t __n, char_type __a)
{
if (__n == 0)
return __s;
return static_cast<char_type*>(__builtin_memset(__s, __a, __n));
}
static _GLIBCXX_CONSTEXPR char_type
to_char_type(const int_type& __c) _GLIBCXX_NOEXCEPT
{ return static_cast<char_type>(__c); }
// To keep both the byte 0xff and the eof symbol 0xffffffff
// from ending up as 0xffffffff.
static _GLIBCXX_CONSTEXPR int_type
to_int_type(const char_type& __c) _GLIBCXX_NOEXCEPT
{ return static_cast<int_type>(static_cast<unsigned char>(__c)); }
static _GLIBCXX_CONSTEXPR bool
eq_int_type(const int_type& __c1, const int_type& __c2) _GLIBCXX_NOEXCEPT
{ return __c1 == __c2; }
static _GLIBCXX_CONSTEXPR int_type
eof() _GLIBCXX_NOEXCEPT
{ return static_cast<int_type>(_GLIBCXX_STDIO_EOF); }
static _GLIBCXX_CONSTEXPR int_type
not_eof(const int_type& __c) _GLIBCXX_NOEXCEPT
{ return (__c == eof()) ? 0 : __c; }
};
#ifdef _GLIBCXX_USE_WCHAR_T
/// 21.1.3.2 char_traits specializations
template<>
struct char_traits<wchar_t>
{
typedef wchar_t char_type;
typedef wint_t int_type;
typedef streamoff off_type;
typedef wstreampos pos_type;
typedef mbstate_t state_type;
static _GLIBCXX17_CONSTEXPR void
assign(char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
{ __c1 = __c2; }
static _GLIBCXX_CONSTEXPR bool
eq(const char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
{ return __c1 == __c2; }
static _GLIBCXX_CONSTEXPR bool
lt(const char_type& __c1, const char_type& __c2) _GLIBCXX_NOEXCEPT
{ return __c1 < __c2; }
static /* _GLIBCXX17_CONSTEXPR */ int
compare(const char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return 0;
return wmemcmp(__s1, __s2, __n);
}
static /* _GLIBCXX17_CONSTEXPR */ size_t
length(const char_type* __s)
{ return wcslen(__s); }
static /* _GLIBCXX17_CONSTEXPR */ const char_type*
find(const char_type* __s, size_t __n, const char_type& __a)
{
if (__n == 0)
return 0;
return wmemchr(__s, __a, __n);
}
static char_type*
move(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
return wmemmove(__s1, __s2, __n);
}
static char_type*
copy(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
return wmemcpy(__s1, __s2, __n);
}
static char_type*
assign(char_type* __s, size_t __n, char_type __a)
{
if (__n == 0)
return __s;
return wmemset(__s, __a, __n);
}
static _GLIBCXX_CONSTEXPR char_type
to_char_type(const int_type& __c) _GLIBCXX_NOEXCEPT
{ return char_type(__c); }
static _GLIBCXX_CONSTEXPR int_type
to_int_type(const char_type& __c) _GLIBCXX_NOEXCEPT
{ return int_type(__c); }
static _GLIBCXX_CONSTEXPR bool
eq_int_type(const int_type& __c1, const int_type& __c2) _GLIBCXX_NOEXCEPT
{ return __c1 == __c2; }
static _GLIBCXX_CONSTEXPR int_type
eof() _GLIBCXX_NOEXCEPT
{ return static_cast<int_type>(WEOF); }
static _GLIBCXX_CONSTEXPR int_type
not_eof(const int_type& __c) _GLIBCXX_NOEXCEPT
{ return eq_int_type(__c, eof()) ? 0 : __c; }
};
#endif //_GLIBCXX_USE_WCHAR_T
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#if ((__cplusplus >= 201103L) \
&& defined(_GLIBCXX_USE_C99_STDINT_TR1))
#include <cstdint>
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
template<>
struct char_traits<char16_t>
{
typedef char16_t char_type;
typedef uint_least16_t int_type;
typedef streamoff off_type;
typedef u16streampos pos_type;
typedef mbstate_t state_type;
static _GLIBCXX17_CONSTEXPR void
assign(char_type& __c1, const char_type& __c2) noexcept
{ __c1 = __c2; }
static constexpr bool
eq(const char_type& __c1, const char_type& __c2) noexcept
{ return __c1 == __c2; }
static constexpr bool
lt(const char_type& __c1, const char_type& __c2) noexcept
{ return __c1 < __c2; }
static _GLIBCXX17_CONSTEXPR int
compare(const char_type* __s1, const char_type* __s2, size_t __n)
{
for (size_t __i = 0; __i < __n; ++__i)
if (lt(__s1[__i], __s2[__i]))
return -1;
else if (lt(__s2[__i], __s1[__i]))
return 1;
return 0;
}
static _GLIBCXX17_CONSTEXPR size_t
length(const char_type* __s)
{
size_t __i = 0;
while (!eq(__s[__i], char_type()))
++__i;
return __i;
}
static _GLIBCXX17_CONSTEXPR const char_type*
find(const char_type* __s, size_t __n, const char_type& __a)
{
for (size_t __i = 0; __i < __n; ++__i)
if (eq(__s[__i], __a))
return __s + __i;
return 0;
}
static char_type*
move(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
return (static_cast<char_type*>
(__builtin_memmove(__s1, __s2, __n * sizeof(char_type))));
}
static char_type*
copy(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
return (static_cast<char_type*>
(__builtin_memcpy(__s1, __s2, __n * sizeof(char_type))));
}
static char_type*
assign(char_type* __s, size_t __n, char_type __a)
{
for (size_t __i = 0; __i < __n; ++__i)
assign(__s[__i], __a);
return __s;
}
static constexpr char_type
to_char_type(const int_type& __c) noexcept
{ return char_type(__c); }
static constexpr int_type
to_int_type(const char_type& __c) noexcept
{ return int_type(__c); }
static constexpr bool
eq_int_type(const int_type& __c1, const int_type& __c2) noexcept
{ return __c1 == __c2; }
static constexpr int_type
eof() noexcept
{ return static_cast<int_type>(-1); }
static constexpr int_type
not_eof(const int_type& __c) noexcept
{ return eq_int_type(__c, eof()) ? 0 : __c; }
};
template<>
struct char_traits<char32_t>
{
typedef char32_t char_type;
typedef uint_least32_t int_type;
typedef streamoff off_type;
typedef u32streampos pos_type;
typedef mbstate_t state_type;
static _GLIBCXX17_CONSTEXPR void
assign(char_type& __c1, const char_type& __c2) noexcept
{ __c1 = __c2; }
static constexpr bool
eq(const char_type& __c1, const char_type& __c2) noexcept
{ return __c1 == __c2; }
static constexpr bool
lt(const char_type& __c1, const char_type& __c2) noexcept
{ return __c1 < __c2; }
static _GLIBCXX17_CONSTEXPR int
compare(const char_type* __s1, const char_type* __s2, size_t __n)
{
for (size_t __i = 0; __i < __n; ++__i)
if (lt(__s1[__i], __s2[__i]))
return -1;
else if (lt(__s2[__i], __s1[__i]))
return 1;
return 0;
}
static _GLIBCXX17_CONSTEXPR size_t
length(const char_type* __s)
{
size_t __i = 0;
while (!eq(__s[__i], char_type()))
++__i;
return __i;
}
static _GLIBCXX17_CONSTEXPR const char_type*
find(const char_type* __s, size_t __n, const char_type& __a)
{
for (size_t __i = 0; __i < __n; ++__i)
if (eq(__s[__i], __a))
return __s + __i;
return 0;
}
static char_type*
move(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
return (static_cast<char_type*>
(__builtin_memmove(__s1, __s2, __n * sizeof(char_type))));
}
static char_type*
copy(char_type* __s1, const char_type* __s2, size_t __n)
{
if (__n == 0)
return __s1;
return (static_cast<char_type*>
(__builtin_memcpy(__s1, __s2, __n * sizeof(char_type))));
}
static char_type*
assign(char_type* __s, size_t __n, char_type __a)
{
for (size_t __i = 0; __i < __n; ++__i)
assign(__s[__i], __a);
return __s;
}
static constexpr char_type
to_char_type(const int_type& __c) noexcept
{ return char_type(__c); }
static constexpr int_type
to_int_type(const char_type& __c) noexcept
{ return int_type(__c); }
static constexpr bool
eq_int_type(const int_type& __c1, const int_type& __c2) noexcept
{ return __c1 == __c2; }
static constexpr int_type
eof() noexcept
{ return static_cast<int_type>(-1); }
static constexpr int_type
not_eof(const int_type& __c) noexcept
{ return eq_int_type(__c, eof()) ? 0 : __c; }
};
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif
#endif // _CHAR_TRAITS_H
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