path: root/libstdc++-v3/include/std/syncstream

// <syncstream> -*- C++ -*-

// Copyright (C) 2020 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 include/syncstream
 *  This is a Standard C++ Library header.
 */

#ifndef _GLIBCXX_SYNCSTREAM
#define _GLIBCXX_SYNCSTREAM 1

#if __cplusplus > 201703L

#include <bits/c++config.h>
#if _GLIBCXX_USE_CXX11_ABI

#define __cpp_lib_syncbuf 201803L

#pragma GCC system_header

#include <sstream>

#include <bits/alloc_traits.h>
#include <bits/allocator.h>
#include <bits/functexcept.h>
#include <bits/functional_hash.h>

#if _GLIBCXX_HAS_GTHREADS
# include <bits/std_mutex.h>
#endif

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  template<typename _CharT, typename _Traits = char_traits<_CharT>,
	    typename _Alloc = allocator<_CharT>>
    class basic_syncbuf : public basic_streambuf<_CharT, _Traits>
    {
    public:
      using char_type = _CharT;
      using int_type = typename _Traits::int_type;
      using pos_type = typename _Traits::pos_type;
      using off_type = typename _Traits::off_type;
      using traits_type = _Traits;
      using allocator_type = _Alloc;
      using streambuf_type = basic_streambuf<_CharT, _Traits>;

      basic_syncbuf()
      : basic_syncbuf(nullptr, allocator_type{})
      { }

      explicit
      basic_syncbuf(streambuf_type* __obuf)
	: basic_syncbuf(__obuf, allocator_type{})
      { }

      basic_syncbuf(streambuf_type* __obuf, const allocator_type& __alloc)
	: _M_wrapped(__obuf)
	, _M_impl(__alloc)
	, _M_mtx(__obuf)
      { }

      basic_syncbuf(basic_syncbuf&& __other)
	: _M_wrapped(__other._M_wrapped)
	, _M_impl(std::move(__other._M_impl))
	, _M_mtx(std::move(__other._M_mtx))
	, _M_emit_on_sync(__other._M_emit_on_sync)
	, _M_needs_sync(__other._M_needs_sync)
      {
	__other._M_wrapped = nullptr;
      }

      ~basic_syncbuf()
      {
	__try
	  {
	    emit();
	  }
	__catch (...)
	  { }
      }

      basic_syncbuf& operator=(basic_syncbuf&& __other)
      {
	if (std::__addressof(__other) != this)
	  {
	    emit();

	    _M_impl = std::move(__other._M_impl);
	    _M_wrapped = __other._M_wrapped; __other._M_wrapped = nullptr;
	    _M_mtx = std::move(__other._M_mtx);
	    _M_emit_on_sync = __other._M_emit_on_sync;
	    _M_needs_sync = __other._M_needs_sync;
	  }
	return *this;
      }

      void
      swap(basic_syncbuf& __other)
      {
	if (std::__addressof(__other) != this)
	  {
	    std::swap(_M_impl, __other._M_impl);
	    std::swap(_M_wrapped, __other._M_wrapped);
	    std::swap(_M_mtx, __other._M_mtx);
	    std::swap(_M_emit_on_sync, __other._M_emit_on_sync);
	    std::swap(_M_needs_sync, __other._M_needs_sync);
	  }
      }

      bool
      emit()
      {
	if (!_M_wrapped)
	  return false;

	auto __s = _M_impl.view();
	if (__s.empty())
	  return true;

	const lock_guard<__mutex> __l(_M_mtx);
	if (_M_wrapped->sputn(__s.data(), __s.size()) != __s.size())
	  return false;

	if (_M_needs_sync)
	  {
	    _M_needs_sync = false;
	    if (_M_wrapped->pubsync() != 0)
	      return false;
	  }

	_M_impl.str("");
	return true;
      }

      streambuf_type*
      get_wrapped() const noexcept
      { return _M_wrapped; }

      allocator_type get_allocator() const noexcept
      { return _M_impl.get_allocator(); }

      void
      set_emit_on_sync(bool __b) noexcept
      { _M_emit_on_sync = __b; }

    protected:
      int
      sync() override
      {
	auto __res = _M_impl.pubsync();
	if (__res == 0)
	  {
	    _M_needs_sync = true;
	    if (_M_emit_on_sync)
	      return emit() ? 0 : -1;
	  }
	return __res;
      }

      streamsize
      xsputn(const char_type* __s, streamsize __n) override
      { return _M_impl.sputn(__s, __n); }

    private:
      streambuf_type* _M_wrapped;

      using __impl_type = basic_stringbuf<char_type, traits_type,
					  allocator_type>;
      __impl_type _M_impl;

      struct __mutex
      {
#if _GLIBCXX_HAS_GTHREADS
	mutex* _M_mtx;

	__mutex(void* __t)
	  : _M_mtx(__t ? &_S_get_mutex(__t) : nullptr)
	{ }

	void
	swap(__mutex& __other) noexcept
	{ std::swap(_M_mtx, __other._M_mtx); }

	void
	lock()
	{
	  if (_M_mtx)
	    _M_mtx->lock();
	}

	void
	unlock()
	{
	  if (_M_mtx)
	    _M_mtx->unlock();
	}

	// FIXME: This should be put in the .so
	static mutex&
	_S_get_mutex(void* __t)
	{
	  const unsigned char __mask = 0xf;
	  static mutex __m[__mask + 1];

	  auto __key = _Hash_impl::hash(__t) & __mask;
	  return __m[__key];
	}
#else
	__mutex(void*)
	{ }

	void
	swap(__mutex&&) noexcept
	{ }

	void
	lock()
	{ }

	void
	unlock()
	{ }
#endif
	__mutex(const __mutex&) = delete;
	__mutex& operator=(const __mutex&) = delete;

	__mutex(__mutex&&) = default;
	__mutex& operator=(__mutex&&) = default;
      };
      __mutex _M_mtx;

      bool _M_emit_on_sync = false;
      bool _M_needs_sync = false;
    };

  template <typename _CharT, typename _Traits = char_traits<_CharT>,
	    typename _Alloc = allocator<_CharT>>
    class basic_osyncstream : public basic_ostream<_CharT, _Traits>
    {
      using __ostream_type = basic_ostream<_CharT, _Traits>;

    public:
      // Types:
      using char_type = _CharT;
      using traits_type = _Traits;
      using allocator_type = _Alloc;
      using int_type = typename traits_type::int_type;
      using pos_type = typename traits_type::pos_type;
      using off_type = typename traits_type::off_type;
      using syncbuf_type = basic_syncbuf<_CharT, _Traits, _Alloc>;
      using streambuf_type = typename syncbuf_type::streambuf_type;

    private:
      syncbuf_type _M_syncbuf;

    public:
      basic_osyncstream(streambuf_type* __buf, const allocator_type& __a)
	: _M_syncbuf(__buf, __a)
      { this->init(std::__addressof(_M_syncbuf)); }

      explicit basic_osyncstream(streambuf_type* __buf)
	: _M_syncbuf(__buf)
      { this->init(std::__addressof(_M_syncbuf)); }

      basic_osyncstream(basic_ostream<char_type, traits_type>& __os,
		        const allocator_type& __a)
	: basic_osyncstream(__os.rdbuf(), __a)
      { this->init(std::__addressof(_M_syncbuf)); }

      explicit basic_osyncstream(basic_ostream<char_type, traits_type>& __os)
	: basic_osyncstream(__os.rdbuf())
      { this->init(std::__addressof(_M_syncbuf)); }

      basic_osyncstream(basic_osyncstream&& __rhs) noexcept
	: __ostream_type(std::move(__rhs)),
	_M_syncbuf(std::move(__rhs._M_syncbuf))
      { __ostream_type::set_rdbuf(std::__addressof(_M_syncbuf)); }

      ~basic_osyncstream() = default;

      basic_osyncstream& operator=(basic_osyncstream&&) noexcept = default;

      syncbuf_type* rdbuf() const noexcept
      { return const_cast<syncbuf_type*>(&_M_syncbuf); }

      streambuf_type* get_wrapped() const noexcept
      { return _M_syncbuf.get_wrapped(); }

      void emit()
      {
	if (!_M_syncbuf.emit())
	  this->setstate(ios_base::failbit);
      }
    };

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

  using syncbuf = basic_syncbuf<char>;
  using wsyncbuf = basic_syncbuf<wchar_t>;

  using osyncstream = basic_osyncstream<char>;
  using wosyncstream = basic_osyncstream<wchar_t>;
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // _GLIBCXX_USE_CXX11_ABI
#endif // C++2a
#endif	/* _GLIBCXX_SYNCSTREAM */