ostream
Go to the documentation of this file.
// Output streams -*- C++ -*-
// Copyright (C) 1997-2018 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file include/ostream
* This is a Standard C++ Library header.
*/
//
// ISO C++ 14882: 27.6.2 Output streams
//
#ifndef _GLIBCXX_OSTREAM
#define _GLIBCXX_OSTREAM 1
#pragma GCC system_header
#include <ios>
#include <bits/ostream_insert.h>
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
* @brief Template class basic_ostream.
* @ingroup io
*
* @tparam _CharT Type of character stream.
* @tparam _Traits Traits for character type, defaults to
* char_traits<_CharT>.
*
* This is the base class for all output streams. It provides text
* formatting of all builtin types, and communicates with any class
* derived from basic_streambuf to do the actual output.
*/
template<typename _CharT, typename _Traits>
class basic_ostream : virtual public basic_ios<_CharT, _Traits>
{
public:
// Types (inherited from basic_ios):
typedef _CharT char_type;
typedef typename _Traits::int_type int_type;
typedef typename _Traits::pos_type pos_type;
typedef typename _Traits::off_type off_type;
typedef _Traits traits_type;
// Non-standard Types:
typedef basic_streambuf<_CharT, _Traits> __streambuf_type;
typedef basic_ios<_CharT, _Traits> __ios_type;
typedef basic_ostream<_CharT, _Traits> __ostream_type;
typedef num_put<_CharT, ostreambuf_iterator<_CharT, _Traits> >
__num_put_type;
typedef ctype<_CharT> __ctype_type;
/**
* @brief Base constructor.
*
* This ctor is almost never called by the user directly, rather from
* derived classes' initialization lists, which pass a pointer to
* their own stream buffer.
*/
explicit
basic_ostream(__streambuf_type* __sb)
{ this->init(__sb); }
/**
* @brief Base destructor.
*
* This does very little apart from providing a virtual base dtor.
*/
virtual
~basic_ostream() { }
/// Safe prefix/suffix operations.
class sentry;
friend class sentry;
//@{
/**
* @brief Interface for manipulators.
*
* Manipulators such as @c std::endl and @c std::hex use these
* functions in constructs like "std::cout << std::endl". For more
* information, see the iomanip header.
*/
__ostream_type&
operator<<(__ostream_type& (*__pf)(__ostream_type&))
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 60. What is a formatted input function?
// The inserters for manipulators are *not* formatted output functions.
return __pf(*this);
}
__ostream_type&
operator<<(__ios_type& (*__pf)(__ios_type&))
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 60. What is a formatted input function?
// The inserters for manipulators are *not* formatted output functions.
__pf(*this);
return *this;
}
__ostream_type&
operator<<(ios_base& (*__pf) (ios_base&))
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// DR 60. What is a formatted input function?
// The inserters for manipulators are *not* formatted output functions.
__pf(*this);
return *this;
}
//@}
//@{
/**
* @name Inserters
*
* All the @c operator<< functions (aka <em>formatted output
* functions</em>) have some common behavior. Each starts by
* constructing a temporary object of type std::basic_ostream::sentry.
* This can have several effects, concluding with the setting of a
* status flag; see the sentry documentation for more.
*
* If the sentry status is good, the function tries to generate
* whatever data is appropriate for the type of the argument.
*
* If an exception is thrown during insertion, ios_base::badbit
* will be turned on in the stream's error state without causing an
* ios_base::failure to be thrown. The original exception will then
* be rethrown.
*/
//@{
/**
* @brief Integer arithmetic inserters
* @param __n A variable of builtin integral type.
* @return @c *this if successful
*
* These functions use the stream's current locale (specifically, the
* @c num_get facet) to perform numeric formatting.
*/
__ostream_type&
operator<<(long __n)
{ return _M_insert(__n); }
__ostream_type&
operator<<(unsigned long __n)
{ return _M_insert(__n); }
__ostream_type&
operator<<(bool __n)
{ return _M_insert(__n); }
__ostream_type&
operator<<(short __n);
__ostream_type&
operator<<(unsigned short __n)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 117. basic_ostream uses nonexistent num_put member functions.
return _M_insert(static_cast<unsigned long>(__n));
}
__ostream_type&
operator<<(int __n);
__ostream_type&
operator<<(unsigned int __n)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 117. basic_ostream uses nonexistent num_put member functions.
return _M_insert(static_cast<unsigned long>(__n));
}
#ifdef _GLIBCXX_USE_LONG_LONG
__ostream_type&
operator<<(long long __n)
{ return _M_insert(__n); }
__ostream_type&
operator<<(unsigned long long __n)
{ return _M_insert(__n); }
#endif
//@}
//@{
/**
* @brief Floating point arithmetic inserters
* @param __f A variable of builtin floating point type.
* @return @c *this if successful
*
* These functions use the stream's current locale (specifically, the
* @c num_get facet) to perform numeric formatting.
*/
__ostream_type&
operator<<(double __f)
{ return _M_insert(__f); }
__ostream_type&
operator<<(float __f)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 117. basic_ostream uses nonexistent num_put member functions.
return _M_insert(static_cast<double>(__f));
}
__ostream_type&
operator<<(long double __f)
{ return _M_insert(__f); }
//@}
/**
* @brief Pointer arithmetic inserters
* @param __p A variable of pointer type.
* @return @c *this if successful
*
* These functions use the stream's current locale (specifically, the
* @c num_get facet) to perform numeric formatting.
*/
__ostream_type&
operator<<(const void* __p)
{ return _M_insert(__p); }
/**
* @brief Extracting from another streambuf.
* @param __sb A pointer to a streambuf
*
* This function behaves like one of the basic arithmetic extractors,
* in that it also constructs a sentry object and has the same error
* handling behavior.
*
* If @p __sb is NULL, the stream will set failbit in its error state.
*
* Characters are extracted from @p __sb and inserted into @c *this
* until one of the following occurs:
*
* - the input stream reaches end-of-file,
* - insertion into the output sequence fails (in this case, the
* character that would have been inserted is not extracted), or
* - an exception occurs while getting a character from @p __sb, which
* sets failbit in the error state
*
* If the function inserts no characters, failbit is set.
*/
__ostream_type&
operator<<(__streambuf_type* __sb);
//@}
//@{
/**
* @name Unformatted Output Functions
*
* All the unformatted output functions have some common behavior.
* Each starts by constructing a temporary object of type
* std::basic_ostream::sentry. This has several effects, concluding
* with the setting of a status flag; see the sentry documentation
* for more.
*
* If the sentry status is good, the function tries to generate
* whatever data is appropriate for the type of the argument.
*
* If an exception is thrown during insertion, ios_base::badbit
* will be turned on in the stream's error state. If badbit is on in
* the stream's exceptions mask, the exception will be rethrown
* without completing its actions.
*/
/**
* @brief Simple insertion.
* @param __c The character to insert.
* @return *this
*
* Tries to insert @p __c.
*
* @note This function is not overloaded on signed char and
* unsigned char.
*/
__ostream_type&
put(char_type __c);
/**
* @brief Core write functionality, without sentry.
* @param __s The array to insert.
* @param __n Maximum number of characters to insert.
*/
void
_M_write(const char_type* __s, streamsize __n)
{
const streamsize __put = this->rdbuf()->sputn(__s, __n);
if (__put != __n)
this->setstate(ios_base::badbit);
}
/**
* @brief Character string insertion.
* @param __s The array to insert.
* @param __n Maximum number of characters to insert.
* @return *this
*
* Characters are copied from @p __s and inserted into the stream until
* one of the following happens:
*
* - @p __n characters are inserted
* - inserting into the output sequence fails (in this case, badbit
* will be set in the stream's error state)
*
* @note This function is not overloaded on signed char and
* unsigned char.
*/
__ostream_type&
write(const char_type* __s, streamsize __n);
//@}
/**
* @brief Synchronizing the stream buffer.
* @return *this
*
* If @c rdbuf() is a null pointer, changes nothing.
*
* Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
* sets badbit.
*/
__ostream_type&
flush();
/**
* @brief Getting the current write position.
* @return A file position object.
*
* If @c fail() is not false, returns @c pos_type(-1) to indicate
* failure. Otherwise returns @c rdbuf()->pubseekoff(0,cur,out).
*/
pos_type
tellp();
/**
* @brief Changing the current write position.
* @param __pos A file position object.
* @return *this
*
* If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos). If
* that function fails, sets failbit.
*/
__ostream_type&
seekp(pos_type);
/**
* @brief Changing the current write position.
* @param __off A file offset object.
* @param __dir The direction in which to seek.
* @return *this
*
* If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
* If that function fails, sets failbit.
*/
__ostream_type&
seekp(off_type, ios_base::seekdir);
protected:
basic_ostream()
{ this->init(0); }
#if __cplusplus >= 201103L
// Non-standard constructor that does not call init()
basic_ostream(basic_iostream<_CharT, _Traits>&) { }
basic_ostream(const basic_ostream&) = delete;
basic_ostream(basic_ostream&& __rhs)
: __ios_type()
{ __ios_type::move(__rhs); }
// 27.7.3.3 Assign/swap
basic_ostream& operator=(const basic_ostream&) = delete;
basic_ostream&
operator=(basic_ostream&& __rhs)
{
swap(__rhs);
return *this;
}
void
swap(basic_ostream& __rhs)
{ __ios_type::swap(__rhs); }
#endif
template<typename _ValueT>
__ostream_type&
_M_insert(_ValueT __v);
};
/**
* @brief Performs setup work for output streams.
*
* Objects of this class are created before all of the standard
* inserters are run. It is responsible for <em>exception-safe prefix and
* suffix operations</em>.
*/
template <typename _CharT, typename _Traits>
class basic_ostream<_CharT, _Traits>::sentry
{
// Data Members.
bool _M_ok;
basic_ostream<_CharT, _Traits>& _M_os;
public:
/**
* @brief The constructor performs preparatory work.
* @param __os The output stream to guard.
*
* If the stream state is good (@a __os.good() is true), then if the
* stream is tied to another output stream, @c is.tie()->flush()
* is called to synchronize the output sequences.
*
* If the stream state is still good, then the sentry state becomes
* true (@a okay).
*/
explicit
sentry(basic_ostream<_CharT, _Traits>& __os);
/**
* @brief Possibly flushes the stream.
*
* If @c ios_base::unitbuf is set in @c os.flags(), and
* @c std::uncaught_exception() is true, the sentry destructor calls
* @c flush() on the output stream.
*/
~sentry()
{
// XXX MT
if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
{
// Can't call flush directly or else will get into recursive lock.
if (_M_os.rdbuf() && _M_os.rdbuf()->pubsync() == -1)
_M_os.setstate(ios_base::badbit);
}
}
/**
* @brief Quick status checking.
* @return The sentry state.
*
* For ease of use, sentries may be converted to booleans. The
* return value is that of the sentry state (true == okay).
*/
#if __cplusplus >= 201103L
explicit
#endif
operator bool() const
{ return _M_ok; }
};
//@{
/**
* @brief Character inserters
* @param __out An output stream.
* @param __c A character.
* @return out
*
* Behaves like one of the formatted arithmetic inserters described in
* std::basic_ostream. After constructing a sentry object with good
* status, this function inserts a single character and any required
* padding (as determined by [22.2.2.2.2]). @c __out.width(0) is then
* called.
*
* If @p __c is of type @c char and the character type of the stream is not
* @c char, the character is widened before insertion.
*/
template<typename _CharT, typename _Traits>
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
{ return __ostream_insert(__out, &__c, 1); }
template<typename _CharT, typename _Traits>
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
{ return (__out << __out.widen(__c)); }
// Specialization
template <class _Traits>
inline basic_ostream<char, _Traits>&
operator<<(basic_ostream<char, _Traits>& __out, char __c)
{ return __ostream_insert(__out, &__c, 1); }
// Signed and unsigned
template<class _Traits>
inline basic_ostream<char, _Traits>&
operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
{ return (__out << static_cast<char>(__c)); }
template<class _Traits>
inline basic_ostream<char, _Traits>&
operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
{ return (__out << static_cast<char>(__c)); }
//@}
//@{
/**
* @brief String inserters
* @param __out An output stream.
* @param __s A character string.
* @return out
* @pre @p __s must be a non-NULL pointer
*
* Behaves like one of the formatted arithmetic inserters described in
* std::basic_ostream. After constructing a sentry object with good
* status, this function inserts @c traits::length(__s) characters starting
* at @p __s, widened if necessary, followed by any required padding (as
* determined by [22.2.2.2.2]). @c __out.width(0) is then called.
*/
template<typename _CharT, typename _Traits>
inline basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
{
if (!__s)
__out.setstate(ios_base::badbit);
else
__ostream_insert(__out, __s,
static_cast<streamsize>(_Traits::length(__s)));
return __out;
}
template<typename _CharT, typename _Traits>
basic_ostream<_CharT, _Traits> &
operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s);
// Partial specializations
template<class _Traits>
inline basic_ostream<char, _Traits>&
operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
{
if (!__s)
__out.setstate(ios_base::badbit);
else
__ostream_insert(__out, __s,
static_cast<streamsize>(_Traits::length(__s)));
return __out;
}
// Signed and unsigned
template<class _Traits>
inline basic_ostream<char, _Traits>&
operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
{ return (__out << reinterpret_cast<const char*>(__s)); }
template<class _Traits>
inline basic_ostream<char, _Traits> &
operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
{ return (__out << reinterpret_cast<const char*>(__s)); }
//@}
// Standard basic_ostream manipulators
/**
* @brief Write a newline and flush the stream.
*
* This manipulator is often mistakenly used when a simple newline is
* desired, leading to poor buffering performance. See
* https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
* for more on this subject.
*/
template<typename _CharT, typename _Traits>
inline basic_ostream<_CharT, _Traits>&
endl(basic_ostream<_CharT, _Traits>& __os)
{ return flush(__os.put(__os.widen('\n'))); }
/**
* @brief Write a null character into the output sequence.
*
* <em>Null character</em> is @c CharT() by definition. For CharT
* of @c char, this correctly writes the ASCII @c NUL character
* string terminator.
*/
template<typename _CharT, typename _Traits>
inline basic_ostream<_CharT, _Traits>&
ends(basic_ostream<_CharT, _Traits>& __os)
{ return __os.put(_CharT()); }
/**
* @brief Flushes the output stream.
*
* This manipulator simply calls the stream's @c flush() member function.
*/
template<typename _CharT, typename _Traits>
inline basic_ostream<_CharT, _Traits>&
flush(basic_ostream<_CharT, _Traits>& __os)
{ return __os.flush(); }
#if __cplusplus >= 201103L
template<typename _Ch, typename _Up>
basic_ostream<_Ch, _Up>&
__is_convertible_to_basic_ostream_test(basic_ostream<_Ch, _Up>*);
template<typename _Tp, typename = void>
struct __is_convertible_to_basic_ostream_impl
{
using __ostream_type = void;
};
template<typename _Tp>
using __do_is_convertible_to_basic_ostream_impl =
decltype(__is_convertible_to_basic_ostream_test
(declval<typename remove_reference<_Tp>::type*>()));
template<typename _Tp>
struct __is_convertible_to_basic_ostream_impl
<_Tp,
__void_t<__do_is_convertible_to_basic_ostream_impl<_Tp>>>
{
using __ostream_type =
__do_is_convertible_to_basic_ostream_impl<_Tp>;
};
template<typename _Tp>
struct __is_convertible_to_basic_ostream
: __is_convertible_to_basic_ostream_impl<_Tp>
{
public:
using type = __not_<is_void<
typename __is_convertible_to_basic_ostream_impl<_Tp>::__ostream_type>>;
constexpr static bool value = type::value;
};
template<typename _Ostream, typename _Tp, typename = void>
struct __is_insertable : false_type {};
template<typename _Ostream, typename _Tp>
struct __is_insertable<_Ostream, _Tp,
__void_t<decltype(declval<_Ostream&>()
<< declval<const _Tp&>())>>
: true_type {};
template<typename _Ostream>
using __rvalue_ostream_type =
typename __is_convertible_to_basic_ostream<
_Ostream>::__ostream_type;
/**
* @brief Generic inserter for rvalue stream
* @param __os An input stream.
* @param __x A reference to the object being inserted.
* @return os
*
* This is just a forwarding function to allow insertion to
* rvalue streams since they won't bind to the inserter functions
* that take an lvalue reference.
*/
template<typename _Ostream, typename _Tp>
inline
typename enable_if<__and_<__not_<is_lvalue_reference<_Ostream>>,
__is_convertible_to_basic_ostream<_Ostream>,
__is_insertable<
__rvalue_ostream_type<_Ostream>,
const _Tp&>>::value,
__rvalue_ostream_type<_Ostream>>::type
operator<<(_Ostream&& __os, const _Tp& __x)
{
__rvalue_ostream_type<_Ostream> __ret_os = __os;
__ret_os << __x;
return __ret_os;
}
#endif // C++11
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#include <bits/ostream.tcc>
#endif /* _GLIBCXX_OSTREAM */
std::ios_base::badbit
static const iostate badbit
Indicates a loss of integrity in an input or output sequence (such as an irrecoverable read error fro...
Definition: ios_base.h:402
std::endl
basic_ostream< _CharT, _Traits > & endl(basic_ostream< _CharT, _Traits > &__os)
Write a newline and flush the stream.
Definition: ostream:590
std::basic_ostream::flush
__ostream_type & flush()
Synchronizing the stream buffer.
Definition: ostream.tcc:211
std::enable_if
Define a member typedef type only if a boolean constant is true.
Definition: type_traits:1987
std::basic_ios::setstate
void setstate(iostate __state)
Sets additional flags in the error state.
Definition: basic_ios.h:157
std::ios_base::unitbuf
static const fmtflags unitbuf
Flushes output after each output operation.
Definition: ios_base.h:371
std::basic_iostream
Template class basic_iostream.
Definition: iosfwd:89
std::basic_ostream::_M_write
void _M_write(const char_type *__s, streamsize __n)
Core write functionality, without sentry.
Definition: ostream:311
std::basic_ostream::seekp
__ostream_type & seekp(pos_type)
Changing the current write position.
Definition: ostream.tcc:258
std::uncaught_exception
_GLIBCXX17_DEPRECATED bool uncaught_exception() noexcept __attribute__((__pure__))
std::ends
basic_ostream< _CharT, _Traits > & ends(basic_ostream< _CharT, _Traits > &__os)
Write a null character into the output sequence.
Definition: ostream:602
ostream_insert.h
std::basic_ostream::tellp
pos_type tellp()
Getting the current write position.
Definition: ostream.tcc:237
std
ISO C++ entities toplevel namespace is std.
std::is_void
is_void
Definition: type_traits:214
std::basic_ios::rdbuf
basic_streambuf< _CharT, _Traits > * rdbuf() const
Accessing the underlying buffer.
Definition: basic_ios.h:321
std::basic_ostream::basic_ostream
basic_ostream(__streambuf_type *__sb)
Base constructor.
Definition: ostream:84
std::ios_base
The base of the I/O class hierarchy.This class defines everything that can be defined about I/O that ...
Definition: ios_base.h:228
std::integral_constant
integral_constant
Definition: type_traits:69
ostream.tcc
std::basic_ostream::put
__ostream_type & put(char_type __c)
Simple insertion.
Definition: ostream.tcc:149
std::basic_ostream::operator<<
__ostream_type & operator<<(__ostream_type &(*__pf)(__ostream_type &))
Interface for manipulators.
Definition: ostream:108
std::basic_ostream::sentry
Performs setup work for output streams.
Definition: ostream:426
std::basic_ostream::write
__ostream_type & write(const char_type *__s, streamsize __n)
Character string insertion.
Definition: ostream.tcc:183
ios
std::basic_ios::init
void init(basic_streambuf< _CharT, _Traits > *__sb)
All setup is performed here.
Definition: basic_ios.tcc:126
std::basic_ostream
Template class basic_ostream.
Definition: iosfwd:86
std::basic_ostream::sentry::~sentry
~sentry()
Possibly flushes the stream.
Definition: ostream:454
std::streamsize
ptrdiff_t streamsize
Integral type for I/O operation counts and buffer sizes.
Definition: postypes.h:98
std::basic_ostream::~basic_ostream
virtual ~basic_ostream()
Base destructor.
Definition: ostream:93