// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_SSTREAM
#define _LIBCPP_SSTREAM

/*
    sstream synopsis [sstream.syn]

// Class template basic_stringbuf [stringbuf]
template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
class basic_stringbuf
    : public basic_streambuf<charT, traits>
{
public:
    typedef charT                          char_type;
    typedef traits                         traits_type;
    typedef typename traits_type::int_type int_type;
    typedef typename traits_type::pos_type pos_type;
    typedef typename traits_type::off_type off_type;
    typedef Allocator                      allocator_type;

    // [stringbuf.cons] constructors:
    explicit basic_stringbuf(ios_base::openmode which = ios_base::in | ios_base::out); // before C++20
    basic_stringbuf() : basic_stringbuf(ios_base::in | ios_base::out) {}               // C++20
    explicit basic_stringbuf(ios_base::openmode which);                                // C++20
    explicit basic_stringbuf(const basic_string<char_type, traits_type, allocator_type>& str,
                             ios_base::openmode which = ios_base::in | ios_base::out);
    basic_stringbuf(basic_stringbuf&& rhs);

    // [stringbuf.assign] Assign and swap:
    basic_stringbuf& operator=(basic_stringbuf&& rhs);
    void swap(basic_stringbuf& rhs) noexcept(see below);                               // conditionally noexcept since C++20

    // [stringbuf.members] Member functions:
    basic_string<char_type, traits_type, allocator_type> str() const;
    void str(const basic_string<char_type, traits_type, allocator_type>& s);
    basic_string_view<char_type, traits_type> view() const noexcept; // C++20

protected:
    // [stringbuf.virtuals] Overridden virtual functions:
    virtual int_type underflow();
    virtual int_type pbackfail(int_type c = traits_type::eof());
    virtual int_type overflow (int_type c = traits_type::eof());
    virtual basic_streambuf<char_type, traits_type>* setbuf(char_type*, streamsize);
    virtual pos_type seekoff(off_type off, ios_base::seekdir way,
                             ios_base::openmode which = ios_base::in | ios_base::out);
    virtual pos_type seekpos(pos_type sp,
                             ios_base::openmode which = ios_base::in | ios_base::out);
};

// [stringbuf.assign] non member swap
template <class charT, class traits, class Allocator>
void swap(basic_stringbuf<charT, traits, Allocator>& x,
          basic_stringbuf<charT, traits, Allocator>& y); // conditionally noexcept since C++20

typedef basic_stringbuf<char>    stringbuf;
typedef basic_stringbuf<wchar_t> wstringbuf;

// Class template basic_istringstream [istringstream]
template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
class basic_istringstream
    : public basic_istream<charT, traits>
{
public:
    typedef charT                          char_type;
    typedef traits                         traits_type;
    typedef typename traits_type::int_type int_type;
    typedef typename traits_type::pos_type pos_type;
    typedef typename traits_type::off_type off_type;
    typedef Allocator                      allocator_type;

    // [istringstream.cons] Constructors:
    explicit basic_istringstream(ios_base::openmode which = ios_base::in); // before C++20
    basic_istringstream() : basic_istringstream(ios_base::in) {}           // C++20
    explicit basic_istringstream(ios_base::openmode which);                // C++20

    explicit basic_istringstream(const basic_string<char_type, traits_type,allocator_type>& str,
                                 ios_base::openmode which = ios_base::in);
    basic_istringstream(basic_istringstream&& rhs);

    // [istringstream.assign] Assign and swap:
    basic_istringstream& operator=(basic_istringstream&& rhs);
    void swap(basic_istringstream& rhs);

    // [istringstream.members] Member functions:
    basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
    basic_string<char_type, traits_type, allocator_type> str() const;
    void str(const basic_string<char_type, traits_type, allocator_type>& s);
    basic_string_view<char_type, traits_type> view() const noexcept; // C++20
};

template <class charT, class traits, class Allocator>
void swap(basic_istringstream<charT, traits, Allocator>& x,
          basic_istringstream<charT, traits, Allocator>& y);

typedef basic_istringstream<char>    istringstream;
typedef basic_istringstream<wchar_t> wistringstream;

// Class template basic_ostringstream [ostringstream]
template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
class basic_ostringstream
    : public basic_ostream<charT, traits>
{
public:
    // types:
    typedef charT                          char_type;
    typedef traits                         traits_type;
    typedef typename traits_type::int_type int_type;
    typedef typename traits_type::pos_type pos_type;
    typedef typename traits_type::off_type off_type;
    typedef Allocator                      allocator_type;

    // [ostringstream.cons] Constructors:
    explicit basic_ostringstream(ios_base::openmode which = ios_base::out); // before C++20
    basic_ostringstream() : basic_ostringstream(ios_base::out) {}           // C++20
    explicit basic_ostringstream(ios_base::openmode which);                 // C++20

    explicit basic_ostringstream(const basic_string<char_type, traits_type, allocator_type>& str,
                                 ios_base::openmode which = ios_base::out);
    basic_ostringstream(basic_ostringstream&& rhs);

    // [ostringstream.assign] Assign and swap:
    basic_ostringstream& operator=(basic_ostringstream&& rhs);
    void swap(basic_ostringstream& rhs);

    // [ostringstream.members] Member functions:
    basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
    basic_string<char_type, traits_type, allocator_type> str() const;
    void str(const basic_string<char_type, traits_type, allocator_type>& s);
    basic_string_view<char_type, traits_type> view() const noexcept; // C++20
};

template <class charT, class traits, class Allocator>
void swap(basic_ostringstream<charT, traits, Allocator>& x,
          basic_ostringstream<charT, traits, Allocator>& y);

typedef basic_ostringstream<char>    ostringstream;
typedef basic_ostringstream<wchar_t> wostringstream;

// Class template basic_stringstream [stringstream]
template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
class basic_stringstream
    : public basic_iostream<charT, traits>
{
public:
    // types:
    typedef charT                          char_type;
    typedef traits                         traits_type;
    typedef typename traits_type::int_type int_type;
    typedef typename traits_type::pos_type pos_type;
    typedef typename traits_type::off_type off_type;
    typedef Allocator                      allocator_type;

    // [stringstream.cons] constructors
    explicit basic_stringstream(ios_base::openmode which = ios_base::out | ios_base::in); // before C++20
    basic_stringstream() : basic_stringstream(ios_base::out | ios_base::in) {}            // C++20
    explicit basic_stringstream(ios_base::openmode which);                                // C++20

    explicit basic_stringstream(const basic_string<char_type, traits_type, allocator_type>& str,
                                ios_base::openmode which = ios_base::out|ios_base::in);
    basic_stringstream(basic_stringstream&& rhs);

    // [stringstream.assign] Assign and swap:
    basic_stringstream& operator=(basic_stringstream&& rhs);
    void swap(basic_stringstream& rhs);

    // [stringstream.members] Member functions:
    basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
    basic_string<char_type, traits_type, allocator_type> str() const;
    void str(const basic_string<char_type, traits_type, allocator_type>& str);
    basic_string_view<char_type, traits_type> view() const noexcept; // C++20
};

template <class charT, class traits, class Allocator>
void swap(basic_stringstream<charT, traits, Allocator>& x,
          basic_stringstream<charT, traits, Allocator>& y);

typedef basic_stringstream<char>    stringstream;
typedef basic_stringstream<wchar_t> wstringstream;

}  // std

*/

#include <__assert> // all public C++ headers provide the assertion handler
#include <__config>
#include <__fwd/sstream.h>
#include <__utility/swap.h>
#include <istream>
#include <ostream>
#include <string>
#include <version>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>


_LIBCPP_BEGIN_NAMESPACE_STD

// Class template basic_stringbuf [stringbuf]

template <class _CharT, class _Traits, class _Allocator>
class _LIBCPP_TEMPLATE_VIS basic_stringbuf
    : public basic_streambuf<_CharT, _Traits>
{
public:
    typedef _CharT                         char_type;
    typedef _Traits                        traits_type;
    typedef typename traits_type::int_type int_type;
    typedef typename traits_type::pos_type pos_type;
    typedef typename traits_type::off_type off_type;
    typedef _Allocator                     allocator_type;

    typedef basic_string<char_type, traits_type, allocator_type> string_type;

private:

    string_type __str_;
    mutable char_type* __hm_;
    ios_base::openmode __mode_;

public:
    // [stringbuf.cons] constructors:
    _LIBCPP_INLINE_VISIBILITY
    basic_stringbuf()
        : __hm_(nullptr), __mode_(ios_base::in | ios_base::out) {}

    _LIBCPP_INLINE_VISIBILITY
    explicit basic_stringbuf(ios_base::openmode __wch)
        : __hm_(nullptr), __mode_(__wch) {}

    _LIBCPP_INLINE_VISIBILITY
    explicit basic_stringbuf(const string_type& __s,
                             ios_base::openmode __wch = ios_base::in | ios_base::out)
        : __str_(__s.get_allocator()), __hm_(nullptr), __mode_(__wch)
    {
        str(__s);
    }

    basic_stringbuf(basic_stringbuf&& __rhs);

    // [stringbuf.assign] Assign and swap:
    basic_stringbuf& operator=(basic_stringbuf&& __rhs);
    void swap(basic_stringbuf& __rhs)
#if _LIBCPP_STD_VER >= 20
        noexcept(allocator_traits<allocator_type>::propagate_on_container_swap::value ||
                 allocator_traits<allocator_type>::is_always_equal::value)
#endif
        ;

    // [stringbuf.members] Member functions:
    string_type str() const;
    void str(const string_type& __s);
#if _LIBCPP_STD_VER >= 20
    _LIBCPP_HIDE_FROM_ABI
    basic_string_view<char_type, traits_type> view() const noexcept;
#endif

protected:
    // [stringbuf.virtuals] Overridden virtual functions:
    int_type underflow() override;
    int_type pbackfail(int_type __c = traits_type::eof()) override;
    int_type overflow (int_type __c = traits_type::eof()) override;
    pos_type seekoff(off_type __off, ios_base::seekdir __way,
                     ios_base::openmode __wch = ios_base::in | ios_base::out) override;
    _LIBCPP_HIDE_FROM_ABI_VIRTUAL
    pos_type seekpos(pos_type __sp,
                     ios_base::openmode __wch = ios_base::in | ios_base::out) override {
        return seekoff(__sp, ios_base::beg, __wch);
    }
};

template <class _CharT, class _Traits, class _Allocator>
basic_stringbuf<_CharT, _Traits, _Allocator>::basic_stringbuf(basic_stringbuf&& __rhs)
    : __mode_(__rhs.__mode_)
{
    char_type* __p = const_cast<char_type*>(__rhs.__str_.data());
    ptrdiff_t __binp = -1;
    ptrdiff_t __ninp = -1;
    ptrdiff_t __einp = -1;
    if (__rhs.eback() != nullptr)
    {
        __binp = __rhs.eback() - __p;
        __ninp = __rhs.gptr() - __p;
        __einp = __rhs.egptr() - __p;
    }
    ptrdiff_t __bout = -1;
    ptrdiff_t __nout = -1;
    ptrdiff_t __eout = -1;
    if (__rhs.pbase() != nullptr)
    {
        __bout = __rhs.pbase() - __p;
        __nout = __rhs.pptr() - __p;
        __eout = __rhs.epptr() - __p;
    }
    ptrdiff_t __hm = __rhs.__hm_ == nullptr ? -1 : __rhs.__hm_ - __p;
    __str_ = _VSTD::move(__rhs.__str_);
    __p = const_cast<char_type*>(__str_.data());
    if (__binp != -1)
        this->setg(__p + __binp, __p + __ninp, __p + __einp);
    if (__bout != -1)
    {
        this->setp(__p + __bout, __p + __eout);
        this->__pbump(__nout);
    }
    __hm_ = __hm == -1 ? nullptr : __p + __hm;
    __p = const_cast<char_type*>(__rhs.__str_.data());
    __rhs.setg(__p, __p, __p);
    __rhs.setp(__p, __p);
    __rhs.__hm_ = __p;
    this->pubimbue(__rhs.getloc());
}

template <class _CharT, class _Traits, class _Allocator>
basic_stringbuf<_CharT, _Traits, _Allocator>&
basic_stringbuf<_CharT, _Traits, _Allocator>::operator=(basic_stringbuf&& __rhs)
{
    char_type* __p = const_cast<char_type*>(__rhs.__str_.data());
    ptrdiff_t __binp = -1;
    ptrdiff_t __ninp = -1;
    ptrdiff_t __einp = -1;
    if (__rhs.eback() != nullptr)
    {
        __binp = __rhs.eback() - __p;
        __ninp = __rhs.gptr() - __p;
        __einp = __rhs.egptr() - __p;
    }
    ptrdiff_t __bout = -1;
    ptrdiff_t __nout = -1;
    ptrdiff_t __eout = -1;
    if (__rhs.pbase() != nullptr)
    {
        __bout = __rhs.pbase() - __p;
        __nout = __rhs.pptr() - __p;
        __eout = __rhs.epptr() - __p;
    }
    ptrdiff_t __hm = __rhs.__hm_ == nullptr ? -1 : __rhs.__hm_ - __p;
    __str_ = _VSTD::move(__rhs.__str_);
    __p = const_cast<char_type*>(__str_.data());
    if (__binp != -1)
        this->setg(__p + __binp, __p + __ninp, __p + __einp);
    else
        this->setg(nullptr, nullptr, nullptr);
    if (__bout != -1)
    {
        this->setp(__p + __bout, __p + __eout);
        this->__pbump(__nout);
    }
    else
        this->setp(nullptr, nullptr);

    __hm_ = __hm == -1 ? nullptr : __p + __hm;
    __mode_ = __rhs.__mode_;
    __p = const_cast<char_type*>(__rhs.__str_.data());
    __rhs.setg(__p, __p, __p);
    __rhs.setp(__p, __p);
    __rhs.__hm_ = __p;
    this->pubimbue(__rhs.getloc());
    return *this;
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_stringbuf<_CharT, _Traits, _Allocator>::swap(basic_stringbuf& __rhs)
#if _LIBCPP_STD_VER >= 20
    noexcept(allocator_traits<_Allocator>::propagate_on_container_swap::value ||
             allocator_traits<_Allocator>::is_always_equal::value)
#endif
{
    char_type* __p = const_cast<char_type*>(__rhs.__str_.data());
    ptrdiff_t __rbinp = -1;
    ptrdiff_t __rninp = -1;
    ptrdiff_t __reinp = -1;
    if (__rhs.eback() != nullptr)
    {
        __rbinp = __rhs.eback() - __p;
        __rninp = __rhs.gptr() - __p;
        __reinp = __rhs.egptr() - __p;
    }
    ptrdiff_t __rbout = -1;
    ptrdiff_t __rnout = -1;
    ptrdiff_t __reout = -1;
    if (__rhs.pbase() != nullptr)
    {
        __rbout = __rhs.pbase() - __p;
        __rnout = __rhs.pptr() - __p;
        __reout = __rhs.epptr() - __p;
    }
    ptrdiff_t __rhm = __rhs.__hm_ == nullptr ? -1 : __rhs.__hm_ - __p;
    __p = const_cast<char_type*>(__str_.data());
    ptrdiff_t __lbinp = -1;
    ptrdiff_t __lninp = -1;
    ptrdiff_t __leinp = -1;
    if (this->eback() != nullptr)
    {
        __lbinp = this->eback() - __p;
        __lninp = this->gptr() - __p;
        __leinp = this->egptr() - __p;
    }
    ptrdiff_t __lbout = -1;
    ptrdiff_t __lnout = -1;
    ptrdiff_t __leout = -1;
    if (this->pbase() != nullptr)
    {
        __lbout = this->pbase() - __p;
        __lnout = this->pptr() - __p;
        __leout = this->epptr() - __p;
    }
    ptrdiff_t __lhm = __hm_ == nullptr ? -1 : __hm_ - __p;
    _VSTD::swap(__mode_, __rhs.__mode_);
    __str_.swap(__rhs.__str_);
    __p = const_cast<char_type*>(__str_.data());
    if (__rbinp != -1)
        this->setg(__p + __rbinp, __p + __rninp, __p + __reinp);
    else
        this->setg(nullptr, nullptr, nullptr);
    if (__rbout != -1)
    {
        this->setp(__p + __rbout, __p + __reout);
        this->__pbump(__rnout);
    }
    else
        this->setp(nullptr, nullptr);
    __hm_ = __rhm == -1 ? nullptr : __p + __rhm;
    __p = const_cast<char_type*>(__rhs.__str_.data());
    if (__lbinp != -1)
        __rhs.setg(__p + __lbinp, __p + __lninp, __p + __leinp);
    else
        __rhs.setg(nullptr, nullptr, nullptr);
    if (__lbout != -1)
    {
        __rhs.setp(__p + __lbout, __p + __leout);
        __rhs.__pbump(__lnout);
    }
    else
        __rhs.setp(nullptr, nullptr);
    __rhs.__hm_ = __lhm == -1 ? nullptr : __p + __lhm;
    locale __tl = __rhs.getloc();
    __rhs.pubimbue(this->getloc());
    this->pubimbue(__tl);
}

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(basic_stringbuf<_CharT, _Traits, _Allocator>& __x,
     basic_stringbuf<_CharT, _Traits, _Allocator>& __y)
#if _LIBCPP_STD_VER >= 20
    noexcept(noexcept(__x.swap(__y)))
#endif
{
    __x.swap(__y);
}

template <class _CharT, class _Traits, class _Allocator>
basic_string<_CharT, _Traits, _Allocator>
basic_stringbuf<_CharT, _Traits, _Allocator>::str() const
{
#if _LIBCPP_STD_VER >= 20
    return string_type(view(), __str_.get_allocator());
#else // _LIBCPP_STD_VER >= 20
    if (__mode_ & ios_base::out)
    {
        if (__hm_ < this->pptr())
            __hm_ = this->pptr();
        return string_type(this->pbase(), __hm_, __str_.get_allocator());
    }
    else if (__mode_ & ios_base::in)
        return string_type(this->eback(), this->egptr(), __str_.get_allocator());
    return string_type(__str_.get_allocator());
#endif // _LIBCPP_STD_VER >= 20
}

template <class _CharT, class _Traits, class _Allocator>
void
basic_stringbuf<_CharT, _Traits, _Allocator>::str(const string_type& __s)
{
    __str_ = __s;
    __hm_ = nullptr;
    if (__mode_ & ios_base::in)
    {
        __hm_ = const_cast<char_type*>(__str_.data()) + __str_.size();
        this->setg(const_cast<char_type*>(__str_.data()),
                   const_cast<char_type*>(__str_.data()),
                   __hm_);
    }
    if (__mode_ & ios_base::out)
    {
        typename string_type::size_type __sz = __str_.size();
        __hm_ = const_cast<char_type*>(__str_.data()) + __sz;
        __str_.resize(__str_.capacity());
        this->setp(const_cast<char_type*>(__str_.data()),
                   const_cast<char_type*>(__str_.data()) + __str_.size());
        if (__mode_ & (ios_base::app | ios_base::ate))
        {
            while (__sz > INT_MAX)
            {
                this->pbump(INT_MAX);
                __sz -= INT_MAX;
            }
            if (__sz > 0)
                this->pbump(__sz);
        }
    }
}

#if _LIBCPP_STD_VER >= 20
template <class _CharT, class _Traits, class _Allocator>
_LIBCPP_HIDE_FROM_ABI basic_string_view<_CharT, _Traits>
basic_stringbuf<_CharT, _Traits, _Allocator>::view() const noexcept {
    if (__mode_ & ios_base::out) {
        if (__hm_ < this->pptr())
            __hm_ = this->pptr();
        return basic_string_view<_CharT, _Traits>(this->pbase(), __hm_);
    } else if (__mode_ & ios_base::in)
        return basic_string_view<_CharT, _Traits>(this->eback(), this->egptr());
    return basic_string_view<_CharT, _Traits>();
}
#endif // _LIBCPP_STD_VER >= 20

template <class _CharT, class _Traits, class _Allocator>
typename basic_stringbuf<_CharT, _Traits, _Allocator>::int_type
basic_stringbuf<_CharT, _Traits, _Allocator>::underflow()
{
    if (__hm_ < this->pptr())
        __hm_ = this->pptr();
    if (__mode_ & ios_base::in)
    {
        if (this->egptr() < __hm_)
            this->setg(this->eback(), this->gptr(), __hm_);
        if (this->gptr() < this->egptr())
            return traits_type::to_int_type(*this->gptr());
    }
    return traits_type::eof();
}

template <class _CharT, class _Traits, class _Allocator>
typename basic_stringbuf<_CharT, _Traits, _Allocator>::int_type
basic_stringbuf<_CharT, _Traits, _Allocator>::pbackfail(int_type __c)
{
    if (__hm_ < this->pptr())
        __hm_ = this->pptr();
    if (this->eback() < this->gptr())
    {
        if (traits_type::eq_int_type(__c, traits_type::eof()))
        {
            this->setg(this->eback(), this->gptr()-1, __hm_);
            return traits_type::not_eof(__c);
        }
        if ((__mode_ & ios_base::out) ||
            traits_type::eq(traits_type::to_char_type(__c), this->gptr()[-1]))
        {
            this->setg(this->eback(), this->gptr()-1, __hm_);
            *this->gptr() = traits_type::to_char_type(__c);
            return __c;
        }
    }
    return traits_type::eof();
}

template <class _CharT, class _Traits, class _Allocator>
typename basic_stringbuf<_CharT, _Traits, _Allocator>::int_type
basic_stringbuf<_CharT, _Traits, _Allocator>::overflow(int_type __c)
{
    if (!traits_type::eq_int_type(__c, traits_type::eof()))
    {
        ptrdiff_t __ninp = this->gptr()  - this->eback();
        if (this->pptr() == this->epptr())
        {
            if (!(__mode_ & ios_base::out))
                return traits_type::eof();
#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
            try
            {
#endif // _LIBCPP_HAS_NO_EXCEPTIONS
                ptrdiff_t __nout = this->pptr()  - this->pbase();
                ptrdiff_t __hm = __hm_ - this->pbase();
                __str_.push_back(char_type());
                __str_.resize(__str_.capacity());
                char_type* __p = const_cast<char_type*>(__str_.data());
                this->setp(__p, __p + __str_.size());
                this->__pbump(__nout);
                __hm_ = this->pbase() + __hm;
#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
            }
            catch (...)
            {
                return traits_type::eof();
            }
#endif // _LIBCPP_HAS_NO_EXCEPTIONS
        }
        __hm_ = _VSTD::max(this->pptr() + 1, __hm_);
        if (__mode_ & ios_base::in)
        {
            char_type* __p = const_cast<char_type*>(__str_.data());
            this->setg(__p, __p + __ninp, __hm_);
        }
        return this->sputc(traits_type::to_char_type(__c));
    }
    return traits_type::not_eof(__c);
}

template <class _CharT, class _Traits, class _Allocator>
typename basic_stringbuf<_CharT, _Traits, _Allocator>::pos_type
basic_stringbuf<_CharT, _Traits, _Allocator>::seekoff(off_type __off,
                                                      ios_base::seekdir __way,
                                                      ios_base::openmode __wch)
{
    if (__hm_ < this->pptr())
        __hm_ = this->pptr();
    if ((__wch & (ios_base::in | ios_base::out)) == 0)
        return pos_type(-1);
    if ((__wch & (ios_base::in | ios_base::out)) == (ios_base::in | ios_base::out)
        && __way == ios_base::cur)
        return pos_type(-1);
    const ptrdiff_t __hm = __hm_ == nullptr ? 0 : __hm_ - __str_.data();
    off_type __noff;
    switch (__way)
    {
    case ios_base::beg:
        __noff = 0;
        break;
    case ios_base::cur:
        if (__wch & ios_base::in)
            __noff = this->gptr() - this->eback();
        else
            __noff = this->pptr() - this->pbase();
        break;
    case ios_base::end:
        __noff = __hm;
        break;
    default:
        return pos_type(-1);
    }
    __noff += __off;
    if (__noff < 0 || __hm < __noff)
        return pos_type(-1);
    if (__noff != 0)
    {
        if ((__wch & ios_base::in) && this->gptr() == nullptr)
            return pos_type(-1);
        if ((__wch & ios_base::out) && this->pptr() == nullptr)
            return pos_type(-1);
    }
    if (__wch & ios_base::in)
        this->setg(this->eback(), this->eback() + __noff, __hm_);
    if (__wch & ios_base::out)
    {
        this->setp(this->pbase(), this->epptr());
        this->__pbump(__noff);
    }
    return pos_type(__noff);
}

// Class template basic_istringstream [istringstream]

template <class _CharT, class _Traits, class _Allocator>
class _LIBCPP_TEMPLATE_VIS basic_istringstream
    : public basic_istream<_CharT, _Traits>
{
public:
    typedef _CharT                         char_type;
    typedef _Traits                        traits_type;
    typedef typename traits_type::int_type int_type;
    typedef typename traits_type::pos_type pos_type;
    typedef typename traits_type::off_type off_type;
    typedef _Allocator                     allocator_type;

    typedef basic_string<char_type, traits_type, allocator_type> string_type;

private:
    basic_stringbuf<char_type, traits_type, allocator_type> __sb_;

public:
    // [istringstream.cons] Constructors:
    _LIBCPP_INLINE_VISIBILITY
    basic_istringstream()
        : basic_istream<_CharT, _Traits>(&__sb_), __sb_(ios_base::in) {}

    _LIBCPP_INLINE_VISIBILITY
    explicit basic_istringstream(ios_base::openmode __wch)
        : basic_istream<_CharT, _Traits>(&__sb_), __sb_(__wch | ios_base::in) {}

    _LIBCPP_INLINE_VISIBILITY
    explicit basic_istringstream(const string_type& __s,
                                 ios_base::openmode __wch = ios_base::in)
        : basic_istream<_CharT, _Traits>(&__sb_)
        , __sb_(__s, __wch | ios_base::in)
    { }

    _LIBCPP_INLINE_VISIBILITY
    basic_istringstream(basic_istringstream&& __rhs)
        : basic_istream<_CharT, _Traits>(_VSTD::move(__rhs))
        , __sb_(_VSTD::move(__rhs.__sb_))
    {
        basic_istream<_CharT, _Traits>::set_rdbuf(&__sb_);
    }

    // [istringstream.assign] Assign and swap:
    basic_istringstream& operator=(basic_istringstream&& __rhs) {
        basic_istream<char_type, traits_type>::operator=(_VSTD::move(__rhs));
        __sb_ = _VSTD::move(__rhs.__sb_);
        return *this;
    }
    _LIBCPP_INLINE_VISIBILITY
    void swap(basic_istringstream& __rhs) {
        basic_istream<char_type, traits_type>::swap(__rhs);
        __sb_.swap(__rhs.__sb_);
    }

    // [istringstream.members] Member functions:
    _LIBCPP_INLINE_VISIBILITY
    basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const {
        return const_cast<basic_stringbuf<char_type, traits_type, allocator_type>*>(&__sb_);
    }
    _LIBCPP_INLINE_VISIBILITY
    string_type str() const {
        return __sb_.str();
    }
    _LIBCPP_INLINE_VISIBILITY
    void str(const string_type& __s) {
        __sb_.str(__s);
    }
#if _LIBCPP_STD_VER >= 20
    _LIBCPP_HIDE_FROM_ABI
    basic_string_view<char_type, traits_type> view() const noexcept {
        return __sb_.view();
    }
#endif
};

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(basic_istringstream<_CharT, _Traits, _Allocator>& __x,
     basic_istringstream<_CharT, _Traits, _Allocator>& __y)
{
    __x.swap(__y);
}

// Class template basic_ostringstream [ostringstream]

template <class _CharT, class _Traits, class _Allocator>
class _LIBCPP_TEMPLATE_VIS basic_ostringstream
    : public basic_ostream<_CharT, _Traits>
{
public:
    typedef _CharT                         char_type;
    typedef _Traits                        traits_type;
    typedef typename traits_type::int_type int_type;
    typedef typename traits_type::pos_type pos_type;
    typedef typename traits_type::off_type off_type;
    typedef _Allocator                     allocator_type;

    typedef basic_string<char_type, traits_type, allocator_type> string_type;

private:
    basic_stringbuf<char_type, traits_type, allocator_type> __sb_;

public:
    // [ostringstream.cons] Constructors:
    _LIBCPP_INLINE_VISIBILITY
    basic_ostringstream()
        : basic_ostream<_CharT, _Traits>(&__sb_), __sb_(ios_base::out) {}

    _LIBCPP_INLINE_VISIBILITY
    explicit basic_ostringstream(ios_base::openmode __wch)
        : basic_ostream<_CharT, _Traits>(&__sb_), __sb_(__wch | ios_base::out) {}

    _LIBCPP_INLINE_VISIBILITY
    explicit basic_ostringstream(const string_type& __s,
                                 ios_base::openmode __wch = ios_base::out)
        : basic_ostream<_CharT, _Traits>(&__sb_)
        , __sb_(__s, __wch | ios_base::out)
    { }

    _LIBCPP_INLINE_VISIBILITY
    basic_ostringstream(basic_ostringstream&& __rhs)
        : basic_ostream<_CharT, _Traits>(_VSTD::move(__rhs))
        , __sb_(_VSTD::move(__rhs.__sb_))
    {
        basic_ostream<_CharT, _Traits>::set_rdbuf(&__sb_);
    }

    // [ostringstream.assign] Assign and swap:
    basic_ostringstream& operator=(basic_ostringstream&& __rhs) {
        basic_ostream<char_type, traits_type>::operator=(_VSTD::move(__rhs));
        __sb_ = _VSTD::move(__rhs.__sb_);
        return *this;
    }

    _LIBCPP_INLINE_VISIBILITY
    void swap(basic_ostringstream& __rhs) {
        basic_ostream<char_type, traits_type>::swap(__rhs);
        __sb_.swap(__rhs.__sb_);
    }

    // [ostringstream.members] Member functions:
    _LIBCPP_INLINE_VISIBILITY
    basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const {
        return const_cast<basic_stringbuf<char_type, traits_type, allocator_type>*>(&__sb_);
    }
    _LIBCPP_INLINE_VISIBILITY
    string_type str() const {
        return __sb_.str();
    }
    _LIBCPP_INLINE_VISIBILITY
    void str(const string_type& __s) {
        __sb_.str(__s);
    }
#if _LIBCPP_STD_VER >= 20
    _LIBCPP_HIDE_FROM_ABI
    basic_string_view<char_type, traits_type> view() const noexcept {
        return __sb_.view();
    }
#endif
};

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(basic_ostringstream<_CharT, _Traits, _Allocator>& __x,
     basic_ostringstream<_CharT, _Traits, _Allocator>& __y)
{
    __x.swap(__y);
}

// Class template basic_stringstream [stringstream]

template <class _CharT, class _Traits, class _Allocator>
class _LIBCPP_TEMPLATE_VIS basic_stringstream
    : public basic_iostream<_CharT, _Traits>
{
public:
    typedef _CharT                         char_type;
    typedef _Traits                        traits_type;
    typedef typename traits_type::int_type int_type;
    typedef typename traits_type::pos_type pos_type;
    typedef typename traits_type::off_type off_type;
    typedef _Allocator                     allocator_type;

    typedef basic_string<char_type, traits_type, allocator_type> string_type;

private:
    basic_stringbuf<char_type, traits_type, allocator_type> __sb_;

public:
    // [stringstream.cons] constructors
    _LIBCPP_INLINE_VISIBILITY
    basic_stringstream()
        : basic_iostream<_CharT, _Traits>(&__sb_), __sb_(ios_base::in | ios_base::out) {}

    _LIBCPP_INLINE_VISIBILITY
    explicit basic_stringstream(ios_base::openmode __wch)
        : basic_iostream<_CharT, _Traits>(&__sb_), __sb_(__wch) {}

    _LIBCPP_INLINE_VISIBILITY
    explicit basic_stringstream(const string_type& __s,
                                ios_base::openmode __wch = ios_base::in | ios_base::out)
        : basic_iostream<_CharT, _Traits>(&__sb_)
        , __sb_(__s, __wch)
    { }

    _LIBCPP_INLINE_VISIBILITY
    basic_stringstream(basic_stringstream&& __rhs)
        : basic_iostream<_CharT, _Traits>(_VSTD::move(__rhs))
        , __sb_(_VSTD::move(__rhs.__sb_))
    {
        basic_istream<_CharT, _Traits>::set_rdbuf(&__sb_);
    }

    // [stringstream.assign] Assign and swap:
    basic_stringstream& operator=(basic_stringstream&& __rhs) {
        basic_iostream<char_type, traits_type>::operator=(_VSTD::move(__rhs));
        __sb_ = _VSTD::move(__rhs.__sb_);
        return *this;
    }
    _LIBCPP_INLINE_VISIBILITY
    void swap(basic_stringstream& __rhs) {
        basic_iostream<char_type, traits_type>::swap(__rhs);
        __sb_.swap(__rhs.__sb_);
    }

    // [stringstream.members] Member functions:
    _LIBCPP_INLINE_VISIBILITY
    basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const {
        return const_cast<basic_stringbuf<char_type, traits_type, allocator_type>*>(&__sb_);
    }
    _LIBCPP_INLINE_VISIBILITY
    string_type str() const {
        return __sb_.str();
    }
    _LIBCPP_INLINE_VISIBILITY
    void str(const string_type& __s) {
        __sb_.str(__s);
    }
#if _LIBCPP_STD_VER >= 20
    _LIBCPP_HIDE_FROM_ABI
    basic_string_view<char_type, traits_type> view() const noexcept {
        return __sb_.view();
    }
#endif
};

template <class _CharT, class _Traits, class _Allocator>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(basic_stringstream<_CharT, _Traits, _Allocator>& __x,
     basic_stringstream<_CharT, _Traits, _Allocator>& __y)
{
    __x.swap(__y);
}

#if defined(_LIBCPP_ABI_ENABLE_ADDITIONAL_IOSTREAM_EXPLICIT_INSTANTIATIONS_1)
extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_stringbuf<char>;
extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_stringstream<char>;
extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostringstream<char>;
extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_istringstream<char>;
#endif

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#if _LIBCPP_STD_VER <= 20 && !defined(_LIPCPP_REMOVE_TRANSITIVE_INCLUDES)
#  include <type_traits>
#endif

#endif // _LIBCPP_SSTREAM
