string_view.hpp

// Copyright 2017-2020 by Martin Moene
//
// string-view lite, a C++17-like string_view for C++98 and later.
// For more information see https://github.com/martinmoene/string-view-lite
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#ifndef NONSTD_SV_LITE_H_INCLUDED
#define NONSTD_SV_LITE_H_INCLUDED
 
#define string_view_lite_MAJOR 1
#define string_view_lite_MINOR 8
#define string_view_lite_PATCH 0
 
#define string_view_lite_VERSION                                                                                                           \
    nssv_STRINGIFY(string_view_lite_MAJOR) "." nssv_STRINGIFY(string_view_lite_MINOR) "." nssv_STRINGIFY(string_view_lite_PATCH)
 
#define nssv_STRINGIFY(x) nssv_STRINGIFY_(x)
#define nssv_STRINGIFY_(x) #x
 
// string-view lite configuration:
 
#define nssv_STRING_VIEW_DEFAULT 0
#define nssv_STRING_VIEW_NONSTD 1
#define nssv_STRING_VIEW_STD 2
 
// tweak header support:
 
#ifdef __has_include
#if __has_include(<nonstd/string_view.tweak.hpp>)
#include <nonstd/string_view.tweak.hpp>
#endif
#define nssv_HAVE_TWEAK_HEADER 1
#else
#define nssv_HAVE_TWEAK_HEADER 0
//# pragma message("string_view.hpp: Note: Tweak header not supported.")
#endif
 
// string_view selection and configuration:
 
#if !defined(nssv_CONFIG_SELECT_STRING_VIEW)
#define nssv_CONFIG_SELECT_STRING_VIEW (nssv_HAVE_STD_STRING_VIEW ? nssv_STRING_VIEW_STD : nssv_STRING_VIEW_NONSTD)
#endif
 
#ifndef nssv_CONFIG_STD_SV_OPERATOR
#define nssv_CONFIG_STD_SV_OPERATOR 0
#endif
 
#ifndef nssv_CONFIG_USR_SV_OPERATOR
#define nssv_CONFIG_USR_SV_OPERATOR 1
#endif
 
#ifdef nssv_CONFIG_CONVERSION_STD_STRING
#define nssv_CONFIG_CONVERSION_STD_STRING_CLASS_METHODS nssv_CONFIG_CONVERSION_STD_STRING
#define nssv_CONFIG_CONVERSION_STD_STRING_FREE_FUNCTIONS nssv_CONFIG_CONVERSION_STD_STRING
#endif
 
#ifndef nssv_CONFIG_CONVERSION_STD_STRING_CLASS_METHODS
#define nssv_CONFIG_CONVERSION_STD_STRING_CLASS_METHODS 1
#endif
 
#ifndef nssv_CONFIG_CONVERSION_STD_STRING_FREE_FUNCTIONS
#define nssv_CONFIG_CONVERSION_STD_STRING_FREE_FUNCTIONS 1
#endif
 
#ifndef nssv_CONFIG_NO_STREAM_INSERTION
#define nssv_CONFIG_NO_STREAM_INSERTION 0
#endif
 
#ifndef nssv_CONFIG_CONSTEXPR11_STD_SEARCH
#define nssv_CONFIG_CONSTEXPR11_STD_SEARCH 1
#endif
 
// Control presence of exception handling (try and auto discover):
 
#ifndef nssv_CONFIG_NO_EXCEPTIONS
#if defined(_MSC_VER)
#include <cstddef> // for _HAS_EXCEPTIONS
#endif
#if defined(__cpp_exceptions) || defined(__EXCEPTIONS) || (_HAS_EXCEPTIONS)
#define nssv_CONFIG_NO_EXCEPTIONS 0
#else
#define nssv_CONFIG_NO_EXCEPTIONS 1
#endif
#endif
 
// C++ language version detection (C++23 is speculative):
// Note: VC14.0/1900 (VS2015) lacks too much from C++14.
 
#ifndef nssv_CPLUSPLUS
#if defined(_MSVC_LANG) && !defined(__clang__)
#define nssv_CPLUSPLUS (_MSC_VER == 1900 ? 201103L : _MSVC_LANG)
#else
#define nssv_CPLUSPLUS __cplusplus
#endif
#endif
 
#define nssv_CPP98_OR_GREATER (nssv_CPLUSPLUS >= 199711L)
#define nssv_CPP11_OR_GREATER (nssv_CPLUSPLUS >= 201103L)
#define nssv_CPP11_OR_GREATER_ (nssv_CPLUSPLUS >= 201103L)
#define nssv_CPP14_OR_GREATER (nssv_CPLUSPLUS >= 201402L)
#define nssv_CPP17_OR_GREATER (nssv_CPLUSPLUS >= 201703L)
#define nssv_CPP20_OR_GREATER (nssv_CPLUSPLUS >= 202002L)
#define nssv_CPP23_OR_GREATER (nssv_CPLUSPLUS >= 202300L)
 
// use C++17 std::string_view if available and requested:
 
#if nssv_CPP17_OR_GREATER && defined(__has_include)
#if __has_include(<string_view> )
#define nssv_HAVE_STD_STRING_VIEW 1
#else
#define nssv_HAVE_STD_STRING_VIEW 0
#endif
#else
#define nssv_HAVE_STD_STRING_VIEW 0
#endif
 
#define nssv_USES_STD_STRING_VIEW                                                                                                          \
    ((nssv_CONFIG_SELECT_STRING_VIEW == nssv_STRING_VIEW_STD) ||                                                                           \
     ((nssv_CONFIG_SELECT_STRING_VIEW == nssv_STRING_VIEW_DEFAULT) && nssv_HAVE_STD_STRING_VIEW))
 
#define nssv_HAVE_STARTS_WITH (nssv_CPP20_OR_GREATER || !nssv_USES_STD_STRING_VIEW)
#define nssv_HAVE_ENDS_WITH nssv_HAVE_STARTS_WITH
 
//
// Use C++17 std::string_view:
//
 
#if nssv_USES_STD_STRING_VIEW
 
#include <string_view>
 
// Extensions for std::string:
 
#if nssv_CONFIG_CONVERSION_STD_STRING_FREE_FUNCTIONS
 
#include <string>
 
namespace nonstd {
 
template <class CharT, class Traits, class Allocator = std::allocator<CharT>>
std::basic_string<CharT, Traits, Allocator> to_string(std::basic_string_view<CharT, Traits> v, Allocator const& a = Allocator()) {
    return std::basic_string<CharT, Traits, Allocator>(v.begin(), v.end(), a);
}
 
template <class CharT, class Traits, class Allocator>
std::basic_string_view<CharT, Traits> to_string_view(std::basic_string<CharT, Traits, Allocator> const& s) {
    return std::basic_string_view<CharT, Traits>(s.data(), s.size());
}
 
// Literal operators sv and _sv:
 
#if nssv_CONFIG_STD_SV_OPERATOR
 
using namespace std::literals::string_view_literals;
 
#endif
 
#if nssv_CONFIG_USR_SV_OPERATOR
 
inline namespace literals {
inline namespace string_view_literals {
 
constexpr std::string_view operator""_sv(const char* str, size_t len) noexcept // (1)
{
    return std::string_view{str, len};
}
 
constexpr std::u16string_view operator""_sv(const char16_t* str, size_t len) noexcept // (2)
{
    return std::u16string_view{str, len};
}
 
constexpr std::u32string_view operator""_sv(const char32_t* str, size_t len) noexcept // (3)
{
    return std::u32string_view{str, len};
}
 
constexpr std::wstring_view operator""_sv(const wchar_t* str, size_t len) noexcept // (4)
{
    return std::wstring_view{str, len};
}
 
} // namespace string_view_literals
} // namespace literals
 
#endif // nssv_CONFIG_USR_SV_OPERATOR
 
} // namespace nonstd
 
#endif // nssv_CONFIG_CONVERSION_STD_STRING_FREE_FUNCTIONS
 
namespace nonstd {
 
using std::basic_string_view;
using std::string_view;
using std::u16string_view;
using std::u32string_view;
using std::wstring_view;
 
// literal "sv" and "_sv", see above
 
using std::operator==;
using std::operator!=;
using std::operator<;
using std::operator<=;
using std::operator>;
using std::operator>=;
 
using std::operator<<;
 
} // namespace nonstd
 
#else // nssv_HAVE_STD_STRING_VIEW
 
//
// Before C++17: use string_view lite:
//
 
// Compiler versions:
//
// MSVC++  6.0  _MSC_VER == 1200  nssv_COMPILER_MSVC_VERSION ==  60  (Visual Studio 6.0)
// MSVC++  7.0  _MSC_VER == 1300  nssv_COMPILER_MSVC_VERSION ==  70  (Visual Studio .NET 2002)
// MSVC++  7.1  _MSC_VER == 1310  nssv_COMPILER_MSVC_VERSION ==  71  (Visual Studio .NET 2003)
// MSVC++  8.0  _MSC_VER == 1400  nssv_COMPILER_MSVC_VERSION ==  80  (Visual Studio 2005)
// MSVC++  9.0  _MSC_VER == 1500  nssv_COMPILER_MSVC_VERSION ==  90  (Visual Studio 2008)
// MSVC++ 10.0  _MSC_VER == 1600  nssv_COMPILER_MSVC_VERSION == 100  (Visual Studio 2010)
// MSVC++ 11.0  _MSC_VER == 1700  nssv_COMPILER_MSVC_VERSION == 110  (Visual Studio 2012)
// MSVC++ 12.0  _MSC_VER == 1800  nssv_COMPILER_MSVC_VERSION == 120  (Visual Studio 2013)
// MSVC++ 14.0  _MSC_VER == 1900  nssv_COMPILER_MSVC_VERSION == 140  (Visual Studio 2015)
// MSVC++ 14.1  _MSC_VER >= 1910  nssv_COMPILER_MSVC_VERSION == 141  (Visual Studio 2017)
// MSVC++ 14.2  _MSC_VER >= 1920  nssv_COMPILER_MSVC_VERSION == 142  (Visual Studio 2019)
 
#if defined(_MSC_VER) && !defined(__clang__)
#define nssv_COMPILER_MSVC_VER (_MSC_VER)
#define nssv_COMPILER_MSVC_VERSION (_MSC_VER / 10 - 10 * (5 + (_MSC_VER < 1900)))
#else
#define nssv_COMPILER_MSVC_VER 0
#define nssv_COMPILER_MSVC_VERSION 0
#endif
 
#define nssv_COMPILER_VERSION(major, minor, patch) (10 * (10 * (major) + (minor)) + (patch))
 
#if defined(__apple_build_version__)
#define nssv_COMPILER_APPLECLANG_VERSION nssv_COMPILER_VERSION(__clang_major__, __clang_minor__, __clang_patchlevel__)
#define nssv_COMPILER_CLANG_VERSION 0
#elif defined(__clang__)
#define nssv_COMPILER_APPLECLANG_VERSION 0
#define nssv_COMPILER_CLANG_VERSION nssv_COMPILER_VERSION(__clang_major__, __clang_minor__, __clang_patchlevel__)
#else
#define nssv_COMPILER_APPLECLANG_VERSION 0
#define nssv_COMPILER_CLANG_VERSION 0
#endif
 
#if defined(__GNUC__) && !defined(__clang__)
#define nssv_COMPILER_GNUC_VERSION nssv_COMPILER_VERSION(__GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__)
#else
#define nssv_COMPILER_GNUC_VERSION 0
#endif
 
// half-open range [lo..hi):
#define nssv_BETWEEN(v, lo, hi) ((lo) <= (v) && (v) < (hi))
 
// Presence of language and library features:
 
#ifdef _HAS_CPP0X
#define nssv_HAS_CPP0X _HAS_CPP0X
#else
#define nssv_HAS_CPP0X 0
#endif
 
// Unless defined otherwise below, consider VC14 as C++11 for string-view-lite:
 
#if nssv_COMPILER_MSVC_VER >= 1900
#undef nssv_CPP11_OR_GREATER
#define nssv_CPP11_OR_GREATER 1
#endif
 
#define nssv_CPP11_90 (nssv_CPP11_OR_GREATER_ || nssv_COMPILER_MSVC_VER >= 1500)
#define nssv_CPP11_100 (nssv_CPP11_OR_GREATER_ || nssv_COMPILER_MSVC_VER >= 1600)
#define nssv_CPP11_110 (nssv_CPP11_OR_GREATER_ || nssv_COMPILER_MSVC_VER >= 1700)
#define nssv_CPP11_120 (nssv_CPP11_OR_GREATER_ || nssv_COMPILER_MSVC_VER >= 1800)
#define nssv_CPP11_140 (nssv_CPP11_OR_GREATER_ || nssv_COMPILER_MSVC_VER >= 1900)
#define nssv_CPP11_141 (nssv_CPP11_OR_GREATER_ || nssv_COMPILER_MSVC_VER >= 1910)
 
#define nssv_CPP14_000 (nssv_CPP14_OR_GREATER)
#define nssv_CPP17_000 (nssv_CPP17_OR_GREATER)
 
// Presence of C++11 language features:
 
#define nssv_HAVE_CONSTEXPR_11 nssv_CPP11_140
#define nssv_HAVE_EXPLICIT_CONVERSION nssv_CPP11_140
#define nssv_HAVE_INLINE_NAMESPACE nssv_CPP11_140
#define nssv_HAVE_IS_DEFAULT nssv_CPP11_140
#define nssv_HAVE_IS_DELETE nssv_CPP11_140
#define nssv_HAVE_NOEXCEPT nssv_CPP11_140
#define nssv_HAVE_NULLPTR nssv_CPP11_100
#define nssv_HAVE_REF_QUALIFIER nssv_CPP11_140
#define nssv_HAVE_UNICODE_LITERALS nssv_CPP11_140
#define nssv_HAVE_USER_DEFINED_LITERALS nssv_CPP11_140
#define nssv_HAVE_WCHAR16_T nssv_CPP11_100
#define nssv_HAVE_WCHAR32_T nssv_CPP11_100
 
#if !((nssv_CPP11_OR_GREATER && nssv_COMPILER_CLANG_VERSION) || nssv_BETWEEN(nssv_COMPILER_CLANG_VERSION, 300, 400))
#define nssv_HAVE_STD_DEFINED_LITERALS nssv_CPP11_140
#else
#define nssv_HAVE_STD_DEFINED_LITERALS 0
#endif
 
// Presence of C++14 language features:
 
#define nssv_HAVE_CONSTEXPR_14 nssv_CPP14_000
 
// Presence of C++17 language features:
 
#define nssv_HAVE_NODISCARD nssv_CPP17_000
 
// Presence of C++ library features:
 
#define nssv_HAVE_STD_HASH nssv_CPP11_120
 
// Presence of compiler intrinsics:
 
// Providing char-type specializations for compare() and length() that
// use compiler intrinsics can improve compile- and run-time performance.
//
// The challenge is in using the right combinations of builtin availability
// and its constexpr-ness.
//
// | compiler | __builtin_memcmp (constexpr) | memcmp  (constexpr) |
// |----------|------------------------------|---------------------|
// | clang    | 4.0              (>= 4.0   ) | any     (?        ) |
// | clang-a  | 9.0              (>= 9.0   ) | any     (?        ) |
// | gcc      | any              (constexpr) | any     (?        ) |
// | msvc     | >= 14.2 C++17    (>= 14.2  ) | any     (?        ) |
 
#define nssv_HAVE_BUILTIN_VER                                                                                                              \
    ((nssv_CPP17_000 && nssv_COMPILER_MSVC_VERSION >= 142) || nssv_COMPILER_GNUC_VERSION > 0 || nssv_COMPILER_CLANG_VERSION >= 400 ||      \
     nssv_COMPILER_APPLECLANG_VERSION >= 900)
#define nssv_HAVE_BUILTIN_CE (nssv_HAVE_BUILTIN_VER)
 
#define nssv_HAVE_BUILTIN_MEMCMP ((nssv_HAVE_CONSTEXPR_14 && nssv_HAVE_BUILTIN_CE) || !nssv_HAVE_CONSTEXPR_14)
#define nssv_HAVE_BUILTIN_STRLEN ((nssv_HAVE_CONSTEXPR_11 && nssv_HAVE_BUILTIN_CE) || !nssv_HAVE_CONSTEXPR_11)
 
#ifdef __has_builtin
#define nssv_HAVE_BUILTIN(x) __has_builtin(x)
#else
#define nssv_HAVE_BUILTIN(x) 0
#endif
 
#if nssv_HAVE_BUILTIN(__builtin_memcmp) || nssv_HAVE_BUILTIN_VER
#define nssv_BUILTIN_MEMCMP __builtin_memcmp
#else
#define nssv_BUILTIN_MEMCMP memcmp
#endif
 
#if nssv_HAVE_BUILTIN(__builtin_strlen) || nssv_HAVE_BUILTIN_VER
#define nssv_BUILTIN_STRLEN __builtin_strlen
#else
#define nssv_BUILTIN_STRLEN strlen
#endif
 
// C++ feature usage:
 
#if nssv_HAVE_CONSTEXPR_11
#define nssv_constexpr constexpr
#else
#define nssv_constexpr /*constexpr*/
#endif
 
#if nssv_HAVE_CONSTEXPR_14
#define nssv_constexpr14 constexpr
#else
#define nssv_constexpr14 /*constexpr*/
#endif
 
#if nssv_HAVE_EXPLICIT_CONVERSION
#define nssv_explicit explicit
#else
#define nssv_explicit /*explicit*/
#endif
 
#if nssv_HAVE_INLINE_NAMESPACE
#define nssv_inline_ns inline
#else
#define nssv_inline_ns /*inline*/
#endif
 
#if nssv_HAVE_NOEXCEPT
#define nssv_noexcept noexcept
#else
#define nssv_noexcept /*noexcept*/
#endif
 
//#if nssv_HAVE_REF_QUALIFIER
//# define nssv_ref_qual  &
//# define nssv_refref_qual  &&
//#else
//# define nssv_ref_qual  /*&*/
//# define nssv_refref_qual  /*&&*/
//#endif
 
#if nssv_HAVE_NULLPTR
#define nssv_nullptr nullptr
#else
#define nssv_nullptr NULL
#endif
 
#if nssv_HAVE_NODISCARD
#define nssv_nodiscard [[nodiscard]]
#else
#define nssv_nodiscard /*[[nodiscard]]*/
#endif
 
// Additional includes:
 
#include <algorithm>
#include <cassert>
#include <iterator>
#include <limits>
#include <string> // std::char_traits<>
 
#if !nssv_CONFIG_NO_STREAM_INSERTION
#include <ostream>
#endif
 
#if !nssv_CONFIG_NO_EXCEPTIONS
#include <stdexcept>
#endif
 
#if nssv_CPP11_OR_GREATER
#include <type_traits>
#endif
 
// Clang, GNUC, MSVC warning suppression macros:
 
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wreserved-user-defined-literal"
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wuser-defined-literals"
#elif nssv_COMPILER_GNUC_VERSION >= 480
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wliteral-suffix"
#endif // __clang__
 
#if nssv_COMPILER_MSVC_VERSION >= 140
#define nssv_SUPPRESS_MSGSL_WARNING(expr) [[gsl::suppress(expr)]]
#define nssv_SUPPRESS_MSVC_WARNING(code, descr) __pragma(warning(suppress : code))
#define nssv_DISABLE_MSVC_WARNINGS(codes) __pragma(warning(push)) __pragma(warning(disable : codes))
#else
#define nssv_SUPPRESS_MSGSL_WARNING(expr)
#define nssv_SUPPRESS_MSVC_WARNING(code, descr)
#define nssv_DISABLE_MSVC_WARNINGS(codes)
#endif
 
#if defined(__clang__)
#define nssv_RESTORE_WARNINGS() _Pragma("clang diagnostic pop")
#elif nssv_COMPILER_GNUC_VERSION >= 480
#define nssv_RESTORE_WARNINGS() _Pragma("GCC diagnostic pop")
#elif nssv_COMPILER_MSVC_VERSION >= 140
#define nssv_RESTORE_WARNINGS() __pragma(warning(pop))
#else
#define nssv_RESTORE_WARNINGS()
#endif
 
// Suppress the following MSVC (GSL) warnings:
// - C4455, non-gsl   : 'operator ""sv': literal suffix identifiers that do not
//                      start with an underscore are reserved
// - C26472, gsl::t.1 : don't use a static_cast for arithmetic conversions;
//                      use brace initialization, gsl::narrow_cast or gsl::narow
// - C26481: gsl::b.1 : don't use pointer arithmetic. Use span instead
 
nssv_DISABLE_MSVC_WARNINGS(4455 26481 26472)
    // nssv_DISABLE_CLANG_WARNINGS( "-Wuser-defined-literals" )
    // nssv_DISABLE_GNUC_WARNINGS( -Wliteral-suffix )
 
    namespace nonstd {
    namespace sv_lite {
 
    //
    // basic_string_view declaration:
    //
 
    template <class CharT, class Traits = std::char_traits<CharT>> class basic_string_view;
 
    namespace detail {
 
    // support constexpr comparison in C++14;
    // for C++17 and later, use provided traits:
 
    template <typename CharT> inline nssv_constexpr14 int compare(CharT const* s1, CharT const* s2, std::size_t count) {
        while(count-- != 0) {
            if(*s1 < *s2)
                return -1;
            if(*s1 > *s2)
                return +1;
            ++s1;
            ++s2;
        }
        return 0;
    }
 
#if nssv_HAVE_BUILTIN_MEMCMP
 
    // specialization of compare() for char, see also generic compare() above:
 
    inline nssv_constexpr14 int compare(char const* s1, char const* s2, std::size_t count) { return nssv_BUILTIN_MEMCMP(s1, s2, count); }
 
#endif
 
#if nssv_HAVE_BUILTIN_STRLEN
 
    // specialization of length() for char, see also generic length() further below:
 
    inline nssv_constexpr std::size_t length(char const* s) { return nssv_BUILTIN_STRLEN(s); }
 
#endif
 
#if defined(__OPTIMIZE__)
 
    // gcc, clang provide __OPTIMIZE__
    // Expect tail call optimization to make length() non-recursive:
 
    template <typename CharT> inline nssv_constexpr std::size_t length(CharT* s, std::size_t result = 0) {
        return *s == '\0' ? result : length(s + 1, result + 1);
    }
 
#else // OPTIMIZE
 
    // non-recursive:
 
    template <typename CharT> inline nssv_constexpr14 std::size_t length(CharT* s) {
        std::size_t result = 0;
        while(*s++ != '\0') {
            ++result;
        }
        return result;
    }
 
#endif // OPTIMIZE
 
#if nssv_CPP11_OR_GREATER && !nssv_CPP17_OR_GREATER
#if defined(__OPTIMIZE__)
 
    // gcc, clang provide __OPTIMIZE__
    // Expect tail call optimization to make search() non-recursive:
 
    template <class CharT, class Traits = std::char_traits<CharT>>
    constexpr const CharT* search(basic_string_view<CharT, Traits> haystack, basic_string_view<CharT, Traits> needle) {
        return haystack.starts_with(needle) ? haystack.begin() : haystack.empty() ? haystack.end() : search(haystack.substr(1), needle);
    }
 
#else // OPTIMIZE
 
    // non-recursive:
 
#if nssv_CONFIG_CONSTEXPR11_STD_SEARCH
 
    template <class CharT, class Traits = std::char_traits<CharT>>
    constexpr const CharT* search(basic_string_view<CharT, Traits> haystack, basic_string_view<CharT, Traits> needle) {
        return std::search(haystack.begin(), haystack.end(), needle.begin(), needle.end());
    }
 
#else  // nssv_CONFIG_CONSTEXPR11_STD_SEARCH
 
    template <class CharT, class Traits = std::char_traits<CharT>>
    nssv_constexpr14 const CharT* search(basic_string_view<CharT, Traits> haystack, basic_string_view<CharT, Traits> needle) {
        while(needle.size() <= haystack.size()) {
            if(haystack.starts_with(needle)) {
                return haystack.cbegin();
            }
            haystack = basic_string_view<CharT, Traits>{haystack.begin() + 1, haystack.size() - 1U};
        }
        return haystack.cend();
    }
#endif // nssv_CONFIG_CONSTEXPR11_STD_SEARCH
 
#endif // OPTIMIZE
#endif // nssv_CPP11_OR_GREATER && ! nssv_CPP17_OR_GREATER
 
    } // namespace detail
 
    //
    // basic_string_view:
    //
 
    template <class CharT, class Traits /* = std::char_traits<CharT> */
              >
    class basic_string_view {
    public:
        // Member types:
 
        typedef Traits traits_type;
        typedef CharT value_type;
 
        typedef CharT* pointer;
        typedef CharT const* const_pointer;
        typedef CharT& reference;
        typedef CharT const& const_reference;
 
        typedef const_pointer iterator;
        typedef const_pointer const_iterator;
        typedef std::reverse_iterator<const_iterator> reverse_iterator;
        typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
 
        typedef std::size_t size_type;
        typedef std::ptrdiff_t difference_type;
 
        // 24.4.2.1 Construction and assignment:
 
        nssv_constexpr basic_string_view() nssv_noexcept : data_(nssv_nullptr), size_(0) {}
 
#if nssv_CPP11_OR_GREATER
        nssv_constexpr basic_string_view(basic_string_view const& other) nssv_noexcept = default;
#else
        nssv_constexpr basic_string_view(basic_string_view const& other) nssv_noexcept : data_(other.data_), size_(other.size_) {}
#endif
 
        nssv_constexpr basic_string_view(CharT const* s, size_type count) nssv_noexcept // non-standard noexcept
        : data_(s),
          size_(count) {}
 
        nssv_constexpr basic_string_view(CharT const* s) nssv_noexcept // non-standard noexcept
        : data_(s)
#if nssv_CPP17_OR_GREATER
        ,
          size_(Traits::length(s))
#elif nssv_CPP11_OR_GREATER
        ,
          size_(detail::length(s))
#else
        ,
          size_(Traits::length(s))
#endif
        {
        }
 
#if nssv_HAVE_NULLPTR
#if nssv_HAVE_IS_DELETE
        nssv_constexpr basic_string_view(std::nullptr_t) nssv_noexcept = delete;
#else
    private:
        nssv_constexpr basic_string_view(std::nullptr_t) nssv_noexcept;
 
    public:
#endif
#endif
 
        // Assignment:
 
#if nssv_CPP11_OR_GREATER
        nssv_constexpr14 basic_string_view& operator=(basic_string_view const& other) nssv_noexcept = default;
#else
        nssv_constexpr14 basic_string_view& operator=(basic_string_view const& other) nssv_noexcept {
            data_ = other.data_;
            size_ = other.size_;
            return *this;
        }
#endif
 
        // 24.4.2.2 Iterator support:
 
        nssv_constexpr const_iterator begin() const nssv_noexcept { return data_; }
        nssv_constexpr const_iterator end() const nssv_noexcept { return data_ + size_; }
 
        nssv_constexpr const_iterator cbegin() const nssv_noexcept { return begin(); }
        nssv_constexpr const_iterator cend() const nssv_noexcept { return end(); }
 
        nssv_constexpr const_reverse_iterator rbegin() const nssv_noexcept { return const_reverse_iterator(end()); }
        nssv_constexpr const_reverse_iterator rend() const nssv_noexcept { return const_reverse_iterator(begin()); }
 
        nssv_constexpr const_reverse_iterator crbegin() const nssv_noexcept { return rbegin(); }
        nssv_constexpr const_reverse_iterator crend() const nssv_noexcept { return rend(); }
 
        // 24.4.2.3 Capacity:
 
        nssv_constexpr size_type size() const nssv_noexcept { return size_; }
        nssv_constexpr size_type length() const nssv_noexcept { return size_; }
        nssv_constexpr size_type max_size() const nssv_noexcept { return (std::numeric_limits<size_type>::max)(); }
 
        // since C++20
        nssv_nodiscard nssv_constexpr bool empty() const nssv_noexcept { return 0 == size_; }
 
        // 24.4.2.4 Element access:
 
        nssv_constexpr const_reference operator[](size_type pos) const { return data_at(pos); }
 
        nssv_constexpr14 const_reference at(size_type pos) const {
#if nssv_CONFIG_NO_EXCEPTIONS
            assert(pos < size());
#else
            if(pos >= size()) {
                throw std::out_of_range("nonstd::string_view::at()");
            }
#endif
            return data_at(pos);
        }
 
        nssv_constexpr const_reference front() const { return data_at(0); }
        nssv_constexpr const_reference back() const { return data_at(size() - 1); }
 
        nssv_constexpr const_pointer data() const nssv_noexcept { return data_; }
 
        // 24.4.2.5 Modifiers:
 
        nssv_constexpr14 void remove_prefix(size_type n) {
            assert(n <= size());
            data_ += n;
            size_ -= n;
        }
 
        nssv_constexpr14 void remove_suffix(size_type n) {
            assert(n <= size());
            size_ -= n;
        }
 
        nssv_constexpr14 void swap(basic_string_view& other) nssv_noexcept {
            const basic_string_view tmp(other);
            other = *this;
            *this = tmp;
        }
 
        // 24.4.2.6 String operations:
 
        size_type copy(CharT* dest, size_type n, size_type pos = 0) const {
#if nssv_CONFIG_NO_EXCEPTIONS
            assert(pos <= size());
#else
            if(pos > size()) {
                throw std::out_of_range("nonstd::string_view::copy()");
            }
#endif
            const size_type rlen = (std::min)(n, size() - pos);
 
            (void)Traits::copy(dest, data() + pos, rlen);
 
            return rlen;
        }
 
        nssv_constexpr14 basic_string_view substr(size_type pos = 0, size_type n = npos) const {
#if nssv_CONFIG_NO_EXCEPTIONS
            assert(pos <= size());
#else
            if(pos > size()) {
                throw std::out_of_range("nonstd::string_view::substr()");
            }
#endif
            return basic_string_view(data() + pos, (std::min)(n, size() - pos));
        }
 
        // compare(), 6x:
 
        nssv_constexpr14 int compare(basic_string_view other) const nssv_noexcept // (1)
        {
#if nssv_CPP17_OR_GREATER
            if(const int result = Traits::compare(data(), other.data(), (std::min)(size(), other.size())))
#else
            if(const int result = detail::compare(data(), other.data(), (std::min)(size(), other.size())))
#endif
            {
                return result;
            }
 
            return size() == other.size() ? 0 : size() < other.size() ? -1 : 1;
        }
 
        nssv_constexpr int compare(size_type pos1, size_type n1, basic_string_view other) const // (2)
        {
            return substr(pos1, n1).compare(other);
        }
 
        nssv_constexpr int compare(size_type pos1, size_type n1, basic_string_view other, size_type pos2, size_type n2) const // (3)
        {
            return substr(pos1, n1).compare(other.substr(pos2, n2));
        }
 
        nssv_constexpr int compare(CharT const* s) const // (4)
        {
            return compare(basic_string_view(s));
        }
 
        nssv_constexpr int compare(size_type pos1, size_type n1, CharT const* s) const // (5)
        {
            return substr(pos1, n1).compare(basic_string_view(s));
        }
 
        nssv_constexpr int compare(size_type pos1, size_type n1, CharT const* s, size_type n2) const // (6)
        {
            return substr(pos1, n1).compare(basic_string_view(s, n2));
        }
 
        // 24.4.2.7 Searching:
 
        // starts_with(), 3x, since C++20:
 
        nssv_constexpr bool starts_with(basic_string_view v) const nssv_noexcept // (1)
        {
            return size() >= v.size() && compare(0, v.size(), v) == 0;
        }
 
        nssv_constexpr bool starts_with(CharT c) const nssv_noexcept // (2)
        {
            return starts_with(basic_string_view(&c, 1));
        }
 
        nssv_constexpr bool starts_with(CharT const* s) const // (3)
        {
            return starts_with(basic_string_view(s));
        }
 
        // ends_with(), 3x, since C++20:
 
        nssv_constexpr bool ends_with(basic_string_view v) const nssv_noexcept // (1)
        {
            return size() >= v.size() && compare(size() - v.size(), npos, v) == 0;
        }
 
        nssv_constexpr bool ends_with(CharT c) const nssv_noexcept // (2)
        {
            return ends_with(basic_string_view(&c, 1));
        }
 
        nssv_constexpr bool ends_with(CharT const* s) const // (3)
        {
            return ends_with(basic_string_view(s));
        }
 
        // find(), 4x:
 
        nssv_constexpr14 size_type find(basic_string_view v, size_type pos = 0) const nssv_noexcept // (1)
        {
            return assert(v.size() == 0 || v.data() != nssv_nullptr), pos >= size() ? npos
                                                                                    : to_pos(
#if nssv_CPP11_OR_GREATER && !nssv_CPP17_OR_GREATER
                                                                                          detail::search(substr(pos), v)
#else
                                                                                          std::search(cbegin() + pos, cend(), v.cbegin(),
                                                                                                      v.cend(), Traits::eq)
#endif
                                                                                      );
        }
 
        nssv_constexpr size_type find(CharT c, size_type pos = 0) const nssv_noexcept // (2)
        {
            return find(basic_string_view(&c, 1), pos);
        }
 
        nssv_constexpr size_type find(CharT const* s, size_type pos, size_type n) const // (3)
        {
            return find(basic_string_view(s, n), pos);
        }
 
        nssv_constexpr size_type find(CharT const* s, size_type pos = 0) const // (4)
        {
            return find(basic_string_view(s), pos);
        }
 
        // rfind(), 4x:
 
        nssv_constexpr14 size_type rfind(basic_string_view v, size_type pos = npos) const nssv_noexcept // (1)
        {
            if(size() < v.size()) {
                return npos;
            }
 
            if(v.empty()) {
                return (std::min)(size(), pos);
            }
 
            const_iterator last = cbegin() + (std::min)(size() - v.size(), pos) + v.size();
            const_iterator result = std::find_end(cbegin(), last, v.cbegin(), v.cend(), Traits::eq);
 
            return result != last ? size_type(result - cbegin()) : npos;
        }
 
        nssv_constexpr14 size_type rfind(CharT c, size_type pos = npos) const nssv_noexcept // (2)
        {
            return rfind(basic_string_view(&c, 1), pos);
        }
 
        nssv_constexpr14 size_type rfind(CharT const* s, size_type pos, size_type n) const // (3)
        {
            return rfind(basic_string_view(s, n), pos);
        }
 
        nssv_constexpr14 size_type rfind(CharT const* s, size_type pos = npos) const // (4)
        {
            return rfind(basic_string_view(s), pos);
        }
 
        // find_first_of(), 4x:
 
        nssv_constexpr size_type find_first_of(basic_string_view v, size_type pos = 0) const nssv_noexcept // (1)
        {
            return pos >= size() ? npos : to_pos(std::find_first_of(cbegin() + pos, cend(), v.cbegin(), v.cend(), Traits::eq));
        }
 
        nssv_constexpr size_type find_first_of(CharT c, size_type pos = 0) const nssv_noexcept // (2)
        {
            return find_first_of(basic_string_view(&c, 1), pos);
        }
 
        nssv_constexpr size_type find_first_of(CharT const* s, size_type pos, size_type n) const // (3)
        {
            return find_first_of(basic_string_view(s, n), pos);
        }
 
        nssv_constexpr size_type find_first_of(CharT const* s, size_type pos = 0) const // (4)
        {
            return find_first_of(basic_string_view(s), pos);
        }
 
        // find_last_of(), 4x:
 
        nssv_constexpr size_type find_last_of(basic_string_view v, size_type pos = npos) const nssv_noexcept // (1)
        {
            return empty() ? npos
                   : pos >= size()
                       ? find_last_of(v, size() - 1)
                       : to_pos(std::find_first_of(const_reverse_iterator(cbegin() + pos + 1), crend(), v.cbegin(), v.cend(), Traits::eq));
        }
 
        nssv_constexpr size_type find_last_of(CharT c, size_type pos = npos) const nssv_noexcept // (2)
        {
            return find_last_of(basic_string_view(&c, 1), pos);
        }
 
        nssv_constexpr size_type find_last_of(CharT const* s, size_type pos, size_type count) const // (3)
        {
            return find_last_of(basic_string_view(s, count), pos);
        }
 
        nssv_constexpr size_type find_last_of(CharT const* s, size_type pos = npos) const // (4)
        {
            return find_last_of(basic_string_view(s), pos);
        }
 
        // find_first_not_of(), 4x:
 
        nssv_constexpr size_type find_first_not_of(basic_string_view v, size_type pos = 0) const nssv_noexcept // (1)
        {
            return pos >= size() ? npos : to_pos(std::find_if(cbegin() + pos, cend(), not_in_view(v)));
        }
 
        nssv_constexpr size_type find_first_not_of(CharT c, size_type pos = 0) const nssv_noexcept // (2)
        {
            return find_first_not_of(basic_string_view(&c, 1), pos);
        }
 
        nssv_constexpr size_type find_first_not_of(CharT const* s, size_type pos, size_type count) const // (3)
        {
            return find_first_not_of(basic_string_view(s, count), pos);
        }
 
        nssv_constexpr size_type find_first_not_of(CharT const* s, size_type pos = 0) const // (4)
        {
            return find_first_not_of(basic_string_view(s), pos);
        }
 
        // find_last_not_of(), 4x:
 
        nssv_constexpr size_type find_last_not_of(basic_string_view v, size_type pos = npos) const nssv_noexcept // (1)
        {
            return empty()         ? npos
                   : pos >= size() ? find_last_not_of(v, size() - 1)
                                   : to_pos(std::find_if(const_reverse_iterator(cbegin() + pos + 1), crend(), not_in_view(v)));
        }
 
        nssv_constexpr size_type find_last_not_of(CharT c, size_type pos = npos) const nssv_noexcept // (2)
        {
            return find_last_not_of(basic_string_view(&c, 1), pos);
        }
 
        nssv_constexpr size_type find_last_not_of(CharT const* s, size_type pos, size_type count) const // (3)
        {
            return find_last_not_of(basic_string_view(s, count), pos);
        }
 
        nssv_constexpr size_type find_last_not_of(CharT const* s, size_type pos = npos) const // (4)
        {
            return find_last_not_of(basic_string_view(s), pos);
        }
 
        // Constants:
 
#if nssv_CPP17_OR_GREATER
        static nssv_constexpr size_type npos = size_type(-1);
#elif nssv_CPP11_OR_GREATER
        enum : size_type { npos = size_type(-1) };
#else
        enum { npos = size_type(-1) };
#endif
 
    private:
        struct not_in_view {
            const basic_string_view v;
 
            nssv_constexpr explicit not_in_view(basic_string_view v_)
            : v(v_) {}
 
            nssv_constexpr bool operator()(CharT c) const { return npos == v.find_first_of(c); }
        };
 
        nssv_constexpr size_type to_pos(const_iterator it) const { return it == cend() ? npos : size_type(it - cbegin()); }
 
        nssv_constexpr size_type to_pos(const_reverse_iterator it) const { return it == crend() ? npos : size_type(crend() - it - 1); }
 
        nssv_constexpr const_reference data_at(size_type pos) const {
#if nssv_BETWEEN(nssv_COMPILER_GNUC_VERSION, 1, 500)
            return data_[pos];
#else
            return assert(pos < size()), data_[pos];
#endif
        }
 
    private:
        const_pointer data_;
        size_type size_;
 
    public:
#if nssv_CONFIG_CONVERSION_STD_STRING_CLASS_METHODS
 
        template <class Allocator>
        basic_string_view(std::basic_string<CharT, Traits, Allocator> const& s) nssv_noexcept : data_(s.data()), size_(s.size()) {}
 
#if nssv_HAVE_EXPLICIT_CONVERSION
 
        template <class Allocator> explicit operator std::basic_string<CharT, Traits, Allocator>() const { return to_string(Allocator()); }
 
#endif // nssv_HAVE_EXPLICIT_CONVERSION
 
#if nssv_CPP11_OR_GREATER
 
        template <class Allocator = std::allocator<CharT>>
        std::basic_string<CharT, Traits, Allocator> to_string(Allocator const& a = Allocator()) const {
            return std::basic_string<CharT, Traits, Allocator>(begin(), end(), a);
        }
 
#else
 
        std::basic_string<CharT, Traits> to_string() const { return std::basic_string<CharT, Traits>(begin(), end()); }
 
        template <class Allocator> std::basic_string<CharT, Traits, Allocator> to_string(Allocator const& a) const {
            return std::basic_string<CharT, Traits, Allocator>(begin(), end(), a);
        }
 
#endif // nssv_CPP11_OR_GREATER
 
#endif // nssv_CONFIG_CONVERSION_STD_STRING_CLASS_METHODS
    };
 
    //
    // Non-member functions:
    //
 
    // 24.4.3 Non-member comparison functions:
    // lexicographically compare two string views (function template):
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator==(basic_string_view<CharT, Traits> lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.size() == rhs.size() && lhs.compare(rhs) == 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator!=(basic_string_view<CharT, Traits> lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return !(lhs == rhs);
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<(basic_string_view<CharT, Traits> lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) < 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<=(basic_string_view<CharT, Traits> lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) <= 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>(basic_string_view<CharT, Traits> lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) > 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>=(basic_string_view<CharT, Traits> lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) >= 0;
    }
 
    // Let S be basic_string_view<CharT, Traits>, and sv be an instance of S.
    // Implementations shall provide sufficient additional overloads marked
    // constexpr and noexcept so that an object t with an implicit conversion
    // to S can be compared according to Table 67.
 
#if !nssv_CPP11_OR_GREATER || nssv_BETWEEN(nssv_COMPILER_MSVC_VERSION, 100, 141)
 
    // accommodate for older compilers:
 
    // ==
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator==(basic_string_view<CharT, Traits> lhs, CharT const* rhs) nssv_noexcept {
        return lhs.size() == detail::length(rhs) && lhs.compare(rhs) == 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator==(CharT const* lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return detail::length(lhs) == rhs.size() && rhs.compare(lhs) == 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator==(basic_string_view<CharT, Traits> lhs, std::basic_string<CharT, Traits> rhs) nssv_noexcept {
        return lhs.size() == rhs.size() && lhs.compare(rhs) == 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator==(std::basic_string<CharT, Traits> rhs, basic_string_view<CharT, Traits> lhs) nssv_noexcept {
        return lhs.size() == rhs.size() && lhs.compare(rhs) == 0;
    }
 
    // !=
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator!=(basic_string_view<CharT, Traits> lhs, CharT const* rhs) nssv_noexcept {
        return !(lhs == rhs);
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator!=(CharT const* lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return !(lhs == rhs);
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator!=(basic_string_view<CharT, Traits> lhs, std::basic_string<CharT, Traits> rhs) nssv_noexcept {
        return !(lhs == rhs);
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator!=(std::basic_string<CharT, Traits> rhs, basic_string_view<CharT, Traits> lhs) nssv_noexcept {
        return !(lhs == rhs);
    }
 
    // <
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<(basic_string_view<CharT, Traits> lhs, CharT const* rhs) nssv_noexcept {
        return lhs.compare(rhs) < 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<(CharT const* lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return rhs.compare(lhs) > 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<(basic_string_view<CharT, Traits> lhs, std::basic_string<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) < 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<(std::basic_string<CharT, Traits> rhs, basic_string_view<CharT, Traits> lhs) nssv_noexcept {
        return rhs.compare(lhs) > 0;
    }
 
    // <=
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<=(basic_string_view<CharT, Traits> lhs, CharT const* rhs) nssv_noexcept {
        return lhs.compare(rhs) <= 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<=(CharT const* lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return rhs.compare(lhs) >= 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<=(basic_string_view<CharT, Traits> lhs, std::basic_string<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) <= 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator<=(std::basic_string<CharT, Traits> rhs, basic_string_view<CharT, Traits> lhs) nssv_noexcept {
        return rhs.compare(lhs) >= 0;
    }
 
    // >
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>(basic_string_view<CharT, Traits> lhs, CharT const* rhs) nssv_noexcept {
        return lhs.compare(rhs) > 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>(CharT const* lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return rhs.compare(lhs) < 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>(basic_string_view<CharT, Traits> lhs, std::basic_string<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) > 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>(std::basic_string<CharT, Traits> rhs, basic_string_view<CharT, Traits> lhs) nssv_noexcept {
        return rhs.compare(lhs) < 0;
    }
 
    // >=
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>=(basic_string_view<CharT, Traits> lhs, CharT const* rhs) nssv_noexcept {
        return lhs.compare(rhs) >= 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>=(CharT const* lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return rhs.compare(lhs) <= 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>=(basic_string_view<CharT, Traits> lhs, std::basic_string<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) >= 0;
    }
 
    template <class CharT, class Traits>
    nssv_constexpr bool operator>=(std::basic_string<CharT, Traits> rhs, basic_string_view<CharT, Traits> lhs) nssv_noexcept {
        return rhs.compare(lhs) <= 0;
    }
 
#else // newer compilers:
 
#define nssv_BASIC_STRING_VIEW_I(T, U) typename std::decay<basic_string_view<T, U>>::type
 
#if defined(_MSC_VER) // issue 40
#define nssv_MSVC_ORDER(x) , int = x
#else
#define nssv_MSVC_ORDER(x) /*, int=x*/
#endif
 
    // ==
 
    template <class CharT, class Traits nssv_MSVC_ORDER(1)>
    nssv_constexpr bool operator==(basic_string_view<CharT, Traits> lhs, nssv_BASIC_STRING_VIEW_I(CharT, Traits) rhs) nssv_noexcept {
        return lhs.size() == rhs.size() && lhs.compare(rhs) == 0;
    }
 
    template <class CharT, class Traits nssv_MSVC_ORDER(2)>
    nssv_constexpr bool operator==(nssv_BASIC_STRING_VIEW_I(CharT, Traits) lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.size() == rhs.size() && lhs.compare(rhs) == 0;
    }
 
    // !=
 
    template <class CharT, class Traits nssv_MSVC_ORDER(1)>
    nssv_constexpr bool operator!=(basic_string_view<CharT, Traits> lhs, nssv_BASIC_STRING_VIEW_I(CharT, Traits) rhs) nssv_noexcept {
        return !(lhs == rhs);
    }
 
    template <class CharT, class Traits nssv_MSVC_ORDER(2)>
    nssv_constexpr bool operator!=(nssv_BASIC_STRING_VIEW_I(CharT, Traits) lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return !(lhs == rhs);
    }
 
    // <
 
    template <class CharT, class Traits nssv_MSVC_ORDER(1)>
    nssv_constexpr bool operator<(basic_string_view<CharT, Traits> lhs, nssv_BASIC_STRING_VIEW_I(CharT, Traits) rhs) nssv_noexcept {
        return lhs.compare(rhs) < 0;
    }
 
    template <class CharT, class Traits nssv_MSVC_ORDER(2)>
    nssv_constexpr bool operator<(nssv_BASIC_STRING_VIEW_I(CharT, Traits) lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) < 0;
    }
 
    // <=
 
    template <class CharT, class Traits nssv_MSVC_ORDER(1)>
    nssv_constexpr bool operator<=(basic_string_view<CharT, Traits> lhs, nssv_BASIC_STRING_VIEW_I(CharT, Traits) rhs) nssv_noexcept {
        return lhs.compare(rhs) <= 0;
    }
 
    template <class CharT, class Traits nssv_MSVC_ORDER(2)>
    nssv_constexpr bool operator<=(nssv_BASIC_STRING_VIEW_I(CharT, Traits) lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) <= 0;
    }
 
    // >
 
    template <class CharT, class Traits nssv_MSVC_ORDER(1)>
    nssv_constexpr bool operator>(basic_string_view<CharT, Traits> lhs, nssv_BASIC_STRING_VIEW_I(CharT, Traits) rhs) nssv_noexcept {
        return lhs.compare(rhs) > 0;
    }
 
    template <class CharT, class Traits nssv_MSVC_ORDER(2)>
    nssv_constexpr bool operator>(nssv_BASIC_STRING_VIEW_I(CharT, Traits) lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) > 0;
    }
 
    // >=
 
    template <class CharT, class Traits nssv_MSVC_ORDER(1)>
    nssv_constexpr bool operator>=(basic_string_view<CharT, Traits> lhs, nssv_BASIC_STRING_VIEW_I(CharT, Traits) rhs) nssv_noexcept {
        return lhs.compare(rhs) >= 0;
    }
 
    template <class CharT, class Traits nssv_MSVC_ORDER(2)>
    nssv_constexpr bool operator>=(nssv_BASIC_STRING_VIEW_I(CharT, Traits) lhs, basic_string_view<CharT, Traits> rhs) nssv_noexcept {
        return lhs.compare(rhs) >= 0;
    }
 
#undef nssv_MSVC_ORDER
#undef nssv_BASIC_STRING_VIEW_I
 
#endif // compiler-dependent approach to comparisons
 
    // 24.4.4 Inserters and extractors:
 
#if !nssv_CONFIG_NO_STREAM_INSERTION
 
    namespace detail {
 
    template <class Stream> void write_padding(Stream& os, std::streamsize n) {
        for(std::streamsize i = 0; i < n; ++i)
            os.rdbuf()->sputc(os.fill());
    }
 
    template <class Stream, class View> Stream& write_to_stream(Stream& os, View const& sv) {
        typename Stream::sentry sentry(os);
 
        if(!sentry)
            return os;
 
        const std::streamsize length = static_cast<std::streamsize>(sv.length());
 
        // Whether, and how, to pad:
        const bool pad = (length < os.width());
        const bool left_pad = pad && (os.flags() & std::ios_base::adjustfield) == std::ios_base::right;
 
        if(left_pad)
            write_padding(os, os.width() - length);
 
        // Write span characters:
        os.rdbuf()->sputn(sv.begin(), length);
 
        if(pad && !left_pad)
            write_padding(os, os.width() - length);
 
        // Reset output stream width:
        os.width(0);
 
        return os;
    }
 
    } // namespace detail
 
    template <class CharT, class Traits>
    std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, basic_string_view<CharT, Traits> sv) {
        return detail::write_to_stream(os, sv);
    }
 
#endif // nssv_CONFIG_NO_STREAM_INSERTION
 
    // Several typedefs for common character types are provided:
 
    typedef basic_string_view<char> string_view;
    typedef basic_string_view<wchar_t> wstring_view;
#if nssv_HAVE_WCHAR16_T
    typedef basic_string_view<char16_t> u16string_view;
    typedef basic_string_view<char32_t> u32string_view;
#endif
 
    } // namespace sv_lite
} // namespace nonstd::sv_lite
 
//
// 24.4.6 Suffix for basic_string_view literals:
//
 
#if nssv_HAVE_USER_DEFINED_LITERALS
 
namespace nonstd {
nssv_inline_ns namespace literals {
    nssv_inline_ns namespace string_view_literals {
 
#if nssv_CONFIG_STD_SV_OPERATOR && nssv_HAVE_STD_DEFINED_LITERALS
 
        nssv_constexpr nonstd::sv_lite::string_view operator""sv(const char* str, size_t len)nssv_noexcept // (1)
        {
            return nonstd::sv_lite::string_view{str, len};
        }
 
        nssv_constexpr nonstd::sv_lite::u16string_view operator""sv(const char16_t* str, size_t len)nssv_noexcept // (2)
        {
            return nonstd::sv_lite::u16string_view{str, len};
        }
 
        nssv_constexpr nonstd::sv_lite::u32string_view operator""sv(const char32_t* str, size_t len)nssv_noexcept // (3)
        {
            return nonstd::sv_lite::u32string_view{str, len};
        }
 
        nssv_constexpr nonstd::sv_lite::wstring_view operator""sv(const wchar_t* str, size_t len)nssv_noexcept // (4)
        {
            return nonstd::sv_lite::wstring_view{str, len};
        }
 
#endif // nssv_CONFIG_STD_SV_OPERATOR && nssv_HAVE_STD_DEFINED_LITERALS
 
#if nssv_CONFIG_USR_SV_OPERATOR
 
        nssv_constexpr nonstd::sv_lite::string_view operator""_sv(const char* str, size_t len)nssv_noexcept // (1)
        {
            return nonstd::sv_lite::string_view{str, len};
        }
 
        nssv_constexpr nonstd::sv_lite::u16string_view operator""_sv(const char16_t* str, size_t len)nssv_noexcept // (2)
        {
            return nonstd::sv_lite::u16string_view{str, len};
        }
 
        nssv_constexpr nonstd::sv_lite::u32string_view operator""_sv(const char32_t* str, size_t len)nssv_noexcept // (3)
        {
            return nonstd::sv_lite::u32string_view{str, len};
        }
 
        nssv_constexpr nonstd::sv_lite::wstring_view operator""_sv(const wchar_t* str, size_t len)nssv_noexcept // (4)
        {
            return nonstd::sv_lite::wstring_view{str, len};
        }
 
#endif // nssv_CONFIG_USR_SV_OPERATOR
    }
}
} // namespace nonstd
 
#endif
 
//
// Extensions for std::string:
//
 
#if nssv_CONFIG_CONVERSION_STD_STRING_FREE_FUNCTIONS
 
namespace nonstd {
namespace sv_lite {
 
// Exclude MSVC 14 (19.00): it yields ambiguous to_string():
 
#if nssv_CPP11_OR_GREATER && nssv_COMPILER_MSVC_VERSION != 140
 
template <class CharT, class Traits, class Allocator = std::allocator<CharT>>
std::basic_string<CharT, Traits, Allocator> to_string(basic_string_view<CharT, Traits> v, Allocator const& a = Allocator()) {
    return std::basic_string<CharT, Traits, Allocator>(v.begin(), v.end(), a);
}
 
#else
 
template <class CharT, class Traits> std::basic_string<CharT, Traits> to_string(basic_string_view<CharT, Traits> v) {
    return std::basic_string<CharT, Traits>(v.begin(), v.end());
}
 
template <class CharT, class Traits, class Allocator>
std::basic_string<CharT, Traits, Allocator> to_string(basic_string_view<CharT, Traits> v, Allocator const& a) {
    return std::basic_string<CharT, Traits, Allocator>(v.begin(), v.end(), a);
}
 
#endif // nssv_CPP11_OR_GREATER
 
template <class CharT, class Traits, class Allocator>
basic_string_view<CharT, Traits> to_string_view(std::basic_string<CharT, Traits, Allocator> const& s) {
    return basic_string_view<CharT, Traits>(s.data(), s.size());
}
 
} // namespace sv_lite
} // namespace nonstd
 
#endif // nssv_CONFIG_CONVERSION_STD_STRING_FREE_FUNCTIONS
 
//
// make types and algorithms available in namespace nonstd:
//
 
namespace nonstd {
 
using sv_lite::basic_string_view;
using sv_lite::string_view;
using sv_lite::wstring_view;
 
#if nssv_HAVE_WCHAR16_T
using sv_lite::u16string_view;
#endif
#if nssv_HAVE_WCHAR32_T
using sv_lite::u32string_view;
#endif
 
// literal "sv"
 
using sv_lite::operator==;
using sv_lite::operator!=;
using sv_lite::operator<;
using sv_lite::operator<=;
using sv_lite::operator>;
using sv_lite::operator>=;
 
#if !nssv_CONFIG_NO_STREAM_INSERTION
using sv_lite::operator<<;
#endif
 
#if nssv_CONFIG_CONVERSION_STD_STRING_FREE_FUNCTIONS
using sv_lite::to_string;
using sv_lite::to_string_view;
#endif
 
} // namespace nonstd
 
// 24.4.5 Hash support (C++11):
 
// Note: The hash value of a string view object is equal to the hash value of
// the corresponding string object.
 
#if nssv_HAVE_STD_HASH
 
#include <functional>
 
namespace std {
 
template <> struct hash<nonstd::string_view> {
public:
    std::size_t operator()(nonstd::string_view v) const nssv_noexcept { return std::hash<std::string>()(std::string(v.data(), v.size())); }
};
 
template <> struct hash<nonstd::wstring_view> {
public:
    std::size_t operator()(nonstd::wstring_view v) const nssv_noexcept {
        return std::hash<std::wstring>()(std::wstring(v.data(), v.size()));
    }
};
 
template <> struct hash<nonstd::u16string_view> {
public:
    std::size_t operator()(nonstd::u16string_view v) const nssv_noexcept {
        return std::hash<std::u16string>()(std::u16string(v.data(), v.size()));
    }
};
 
template <> struct hash<nonstd::u32string_view> {
public:
    std::size_t operator()(nonstd::u32string_view v) const nssv_noexcept {
        return std::hash<std::u32string>()(std::u32string(v.data(), v.size()));
    }
};
 
} // namespace std
 
#endif // nssv_HAVE_STD_HASH
 
nssv_RESTORE_WARNINGS()
 
#endif // nssv_HAVE_STD_STRING_VIEW
#endif // NONSTD_SV_LITE_H_INCLUDED