libstdc++
ostream
Go to the documentation of this file.
00001 // Output streams -*- C++ -*-
00002 
00003 // Copyright (C) 1997-2015 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file include/ostream
00026  *  This is a Standard C++ Library header.
00027  */
00028 
00029 //
00030 // ISO C++ 14882: 27.6.2  Output streams
00031 //
00032 
00033 #ifndef _GLIBCXX_OSTREAM
00034 #define _GLIBCXX_OSTREAM 1
00035 
00036 #pragma GCC system_header
00037 
00038 #include <ios>
00039 #include <bits/ostream_insert.h>
00040 
00041 namespace std _GLIBCXX_VISIBILITY(default)
00042 {
00043 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00044 
00045   /**
00046    *  @brief  Template class basic_ostream.
00047    *  @ingroup io
00048    *
00049    *  @tparam _CharT  Type of character stream.
00050    *  @tparam _Traits  Traits for character type, defaults to
00051    *                   char_traits<_CharT>.
00052    *
00053    *  This is the base class for all output streams.  It provides text
00054    *  formatting of all builtin types, and communicates with any class
00055    *  derived from basic_streambuf to do the actual output.
00056   */
00057   template<typename _CharT, typename _Traits>
00058     class basic_ostream : virtual public basic_ios<_CharT, _Traits>
00059     {
00060     public:
00061       // Types (inherited from basic_ios):
00062       typedef _CharT                                    char_type;
00063       typedef typename _Traits::int_type                int_type;
00064       typedef typename _Traits::pos_type                pos_type;
00065       typedef typename _Traits::off_type                off_type;
00066       typedef _Traits                                   traits_type;
00067 
00068       // Non-standard Types:
00069       typedef basic_streambuf<_CharT, _Traits>          __streambuf_type;
00070       typedef basic_ios<_CharT, _Traits>                __ios_type;
00071       typedef basic_ostream<_CharT, _Traits>            __ostream_type;
00072       typedef num_put<_CharT, ostreambuf_iterator<_CharT, _Traits> >
00073                                                         __num_put_type;
00074       typedef ctype<_CharT>                             __ctype_type;
00075 
00076       /**
00077        *  @brief  Base constructor.
00078        *
00079        *  This ctor is almost never called by the user directly, rather from
00080        *  derived classes' initialization lists, which pass a pointer to
00081        *  their own stream buffer.
00082       */
00083       explicit
00084       basic_ostream(__streambuf_type* __sb)
00085       { this->init(__sb); }
00086 
00087       /**
00088        *  @brief  Base destructor.
00089        *
00090        *  This does very little apart from providing a virtual base dtor.
00091       */
00092       virtual
00093       ~basic_ostream() { }
00094 
00095       /// Safe prefix/suffix operations.
00096       class sentry;
00097       friend class sentry;
00098 
00099       //@{
00100       /**
00101        *  @brief  Interface for manipulators.
00102        *
00103        *  Manipulators such as @c std::endl and @c std::hex use these
00104        *  functions in constructs like "std::cout << std::endl".  For more
00105        *  information, see the iomanip header.
00106       */
00107       __ostream_type&
00108       operator<<(__ostream_type& (*__pf)(__ostream_type&))
00109       {
00110         // _GLIBCXX_RESOLVE_LIB_DEFECTS
00111         // DR 60. What is a formatted input function?
00112         // The inserters for manipulators are *not* formatted output functions.
00113         return __pf(*this);
00114       }
00115 
00116       __ostream_type&
00117       operator<<(__ios_type& (*__pf)(__ios_type&))
00118       {
00119         // _GLIBCXX_RESOLVE_LIB_DEFECTS
00120         // DR 60. What is a formatted input function?
00121         // The inserters for manipulators are *not* formatted output functions.
00122         __pf(*this);
00123         return *this;
00124       }
00125 
00126       __ostream_type&
00127       operator<<(ios_base& (*__pf) (ios_base&))
00128       {
00129         // _GLIBCXX_RESOLVE_LIB_DEFECTS
00130         // DR 60. What is a formatted input function?
00131         // The inserters for manipulators are *not* formatted output functions.
00132         __pf(*this);
00133         return *this;
00134       }
00135       //@}
00136 
00137       //@{
00138       /**
00139        *  @name Inserters
00140        *
00141        *  All the @c operator<< functions (aka <em>formatted output
00142        *  functions</em>) have some common behavior.  Each starts by
00143        *  constructing a temporary object of type std::basic_ostream::sentry.
00144        *  This can have several effects, concluding with the setting of a
00145        *  status flag; see the sentry documentation for more.
00146        *
00147        *  If the sentry status is good, the function tries to generate
00148        *  whatever data is appropriate for the type of the argument.
00149        *
00150        *  If an exception is thrown during insertion, ios_base::badbit
00151        *  will be turned on in the stream's error state without causing an
00152        *  ios_base::failure to be thrown.  The original exception will then
00153        *  be rethrown.
00154       */
00155 
00156       //@{
00157       /**
00158        *  @brief Integer arithmetic inserters
00159        *  @param  __n A variable of builtin integral type.
00160        *  @return  @c *this if successful
00161        *
00162        *  These functions use the stream's current locale (specifically, the
00163        *  @c num_get facet) to perform numeric formatting.
00164       */
00165       __ostream_type&
00166       operator<<(long __n)
00167       { return _M_insert(__n); }
00168 
00169       __ostream_type&
00170       operator<<(unsigned long __n)
00171       { return _M_insert(__n); }
00172 
00173       __ostream_type&
00174       operator<<(bool __n)
00175       { return _M_insert(__n); }
00176 
00177       __ostream_type&
00178       operator<<(short __n);
00179 
00180       __ostream_type&
00181       operator<<(unsigned short __n)
00182       {
00183         // _GLIBCXX_RESOLVE_LIB_DEFECTS
00184         // 117. basic_ostream uses nonexistent num_put member functions.
00185         return _M_insert(static_cast<unsigned long>(__n));
00186       }
00187 
00188       __ostream_type&
00189       operator<<(int __n);
00190 
00191       __ostream_type&
00192       operator<<(unsigned int __n)
00193       {
00194         // _GLIBCXX_RESOLVE_LIB_DEFECTS
00195         // 117. basic_ostream uses nonexistent num_put member functions.
00196         return _M_insert(static_cast<unsigned long>(__n));
00197       }
00198 
00199 #ifdef _GLIBCXX_USE_LONG_LONG
00200       __ostream_type&
00201       operator<<(long long __n)
00202       { return _M_insert(__n); }
00203 
00204       __ostream_type&
00205       operator<<(unsigned long long __n)
00206       { return _M_insert(__n); }
00207 #endif
00208       //@}
00209 
00210       //@{
00211       /**
00212        *  @brief  Floating point arithmetic inserters
00213        *  @param  __f A variable of builtin floating point type.
00214        *  @return  @c *this if successful
00215        *
00216        *  These functions use the stream's current locale (specifically, the
00217        *  @c num_get facet) to perform numeric formatting.
00218       */
00219       __ostream_type&
00220       operator<<(double __f)
00221       { return _M_insert(__f); }
00222 
00223       __ostream_type&
00224       operator<<(float __f)
00225       {
00226         // _GLIBCXX_RESOLVE_LIB_DEFECTS
00227         // 117. basic_ostream uses nonexistent num_put member functions.
00228         return _M_insert(static_cast<double>(__f));
00229       }
00230 
00231       __ostream_type&
00232       operator<<(long double __f)
00233       { return _M_insert(__f); }
00234       //@}
00235 
00236       /**
00237        *  @brief  Pointer arithmetic inserters
00238        *  @param  __p A variable of pointer type.
00239        *  @return  @c *this if successful
00240        *
00241        *  These functions use the stream's current locale (specifically, the
00242        *  @c num_get facet) to perform numeric formatting.
00243       */
00244       __ostream_type&
00245       operator<<(const void* __p)
00246       { return _M_insert(__p); }
00247 
00248       /**
00249        *  @brief  Extracting from another streambuf.
00250        *  @param  __sb  A pointer to a streambuf
00251        *
00252        *  This function behaves like one of the basic arithmetic extractors,
00253        *  in that it also constructs a sentry object and has the same error
00254        *  handling behavior.
00255        *
00256        *  If @p __sb is NULL, the stream will set failbit in its error state.
00257        *
00258        *  Characters are extracted from @p __sb and inserted into @c *this
00259        *  until one of the following occurs:
00260        *
00261        *  - the input stream reaches end-of-file,
00262        *  - insertion into the output sequence fails (in this case, the
00263        *    character that would have been inserted is not extracted), or
00264        *  - an exception occurs while getting a character from @p __sb, which
00265        *    sets failbit in the error state
00266        *
00267        *  If the function inserts no characters, failbit is set.
00268       */
00269       __ostream_type&
00270       operator<<(__streambuf_type* __sb);
00271       //@}
00272 
00273       //@{
00274       /**
00275        *  @name Unformatted Output Functions
00276        *
00277        *  All the unformatted output functions have some common behavior.
00278        *  Each starts by constructing a temporary object of type
00279        *  std::basic_ostream::sentry.  This has several effects, concluding
00280        *  with the setting of a status flag; see the sentry documentation
00281        *  for more.
00282        *
00283        *  If the sentry status is good, the function tries to generate
00284        *  whatever data is appropriate for the type of the argument.
00285        *
00286        *  If an exception is thrown during insertion, ios_base::badbit
00287        *  will be turned on in the stream's error state.  If badbit is on in
00288        *  the stream's exceptions mask, the exception will be rethrown
00289        *  without completing its actions.
00290       */
00291 
00292       /**
00293        *  @brief  Simple insertion.
00294        *  @param  __c  The character to insert.
00295        *  @return  *this
00296        *
00297        *  Tries to insert @p __c.
00298        *
00299        *  @note  This function is not overloaded on signed char and
00300        *         unsigned char.
00301       */
00302       __ostream_type&
00303       put(char_type __c);
00304 
00305       /**
00306        *  @brief  Core write functionality, without sentry.
00307        *  @param  __s  The array to insert.
00308        *  @param  __n  Maximum number of characters to insert.
00309       */
00310       void
00311       _M_write(const char_type* __s, streamsize __n)
00312       {
00313         const streamsize __put = this->rdbuf()->sputn(__s, __n);
00314         if (__put != __n)
00315           this->setstate(ios_base::badbit);
00316       }
00317 
00318       /**
00319        *  @brief  Character string insertion.
00320        *  @param  __s  The array to insert.
00321        *  @param  __n  Maximum number of characters to insert.
00322        *  @return  *this
00323        *
00324        *  Characters are copied from @p __s and inserted into the stream until
00325        *  one of the following happens:
00326        *
00327        *  - @p __n characters are inserted
00328        *  - inserting into the output sequence fails (in this case, badbit
00329        *    will be set in the stream's error state)
00330        *
00331        *  @note  This function is not overloaded on signed char and
00332        *         unsigned char.
00333       */
00334       __ostream_type&
00335       write(const char_type* __s, streamsize __n);
00336       //@}
00337 
00338       /**
00339        *  @brief  Synchronizing the stream buffer.
00340        *  @return  *this
00341        *
00342        *  If @c rdbuf() is a null pointer, changes nothing.
00343        *
00344        *  Otherwise, calls @c rdbuf()->pubsync(), and if that returns -1,
00345        *  sets badbit.
00346       */
00347       __ostream_type&
00348       flush();
00349 
00350       /**
00351        *  @brief  Getting the current write position.
00352        *  @return  A file position object.
00353        *
00354        *  If @c fail() is not false, returns @c pos_type(-1) to indicate
00355        *  failure.  Otherwise returns @c rdbuf()->pubseekoff(0,cur,out).
00356       */
00357       pos_type
00358       tellp();
00359 
00360       /**
00361        *  @brief  Changing the current write position.
00362        *  @param  __pos  A file position object.
00363        *  @return  *this
00364        *
00365        *  If @c fail() is not true, calls @c rdbuf()->pubseekpos(pos).  If
00366        *  that function fails, sets failbit.
00367       */
00368       __ostream_type&
00369       seekp(pos_type);
00370 
00371       /**
00372        *  @brief  Changing the current write position.
00373        *  @param  __off  A file offset object.
00374        *  @param  __dir  The direction in which to seek.
00375        *  @return  *this
00376        *
00377        *  If @c fail() is not true, calls @c rdbuf()->pubseekoff(off,dir).
00378        *  If that function fails, sets failbit.
00379       */
00380        __ostream_type&
00381       seekp(off_type, ios_base::seekdir);
00382 
00383     protected:
00384       basic_ostream()
00385       { this->init(0); }
00386 
00387 #if __cplusplus >= 201103L
00388       // Non-standard constructor that does not call init()
00389       basic_ostream(basic_iostream<_CharT, _Traits>&) { }
00390 
00391       basic_ostream(const basic_ostream&) = delete;
00392 
00393       basic_ostream(basic_ostream&& __rhs)
00394       : __ios_type()
00395       { __ios_type::move(__rhs); }
00396 
00397       // 27.7.3.3 Assign/swap
00398 
00399       basic_ostream& operator=(const basic_ostream&) = delete;
00400 
00401       basic_ostream&
00402       operator=(basic_ostream&& __rhs)
00403       {
00404         swap(__rhs);
00405         return *this;
00406       }
00407 
00408       void
00409       swap(basic_ostream& __rhs)
00410       { __ios_type::swap(__rhs); }
00411 #endif
00412 
00413       template<typename _ValueT>
00414         __ostream_type&
00415         _M_insert(_ValueT __v);
00416     };
00417 
00418   /**
00419    *  @brief  Performs setup work for output streams.
00420    *
00421    *  Objects of this class are created before all of the standard
00422    *  inserters are run.  It is responsible for <em>exception-safe prefix and
00423    *  suffix operations</em>.
00424   */
00425   template <typename _CharT, typename _Traits>
00426     class basic_ostream<_CharT, _Traits>::sentry
00427     {
00428       // Data Members.
00429       bool                              _M_ok;
00430       basic_ostream<_CharT, _Traits>&   _M_os;
00431 
00432     public:
00433       /**
00434        *  @brief  The constructor performs preparatory work.
00435        *  @param  __os  The output stream to guard.
00436        *
00437        *  If the stream state is good (@a __os.good() is true), then if the
00438        *  stream is tied to another output stream, @c is.tie()->flush()
00439        *  is called to synchronize the output sequences.
00440        *
00441        *  If the stream state is still good, then the sentry state becomes
00442        *  true (@a okay).
00443       */
00444       explicit
00445       sentry(basic_ostream<_CharT, _Traits>& __os);
00446 
00447       /**
00448        *  @brief  Possibly flushes the stream.
00449        *
00450        *  If @c ios_base::unitbuf is set in @c os.flags(), and
00451        *  @c std::uncaught_exception() is true, the sentry destructor calls
00452        *  @c flush() on the output stream.
00453       */
00454       ~sentry()
00455       {
00456         // XXX MT
00457         if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
00458           {
00459             // Can't call flush directly or else will get into recursive lock.
00460             if (_M_os.rdbuf() && _M_os.rdbuf()->pubsync() == -1)
00461               _M_os.setstate(ios_base::badbit);
00462           }
00463       }
00464 
00465       /**
00466        *  @brief  Quick status checking.
00467        *  @return  The sentry state.
00468        *
00469        *  For ease of use, sentries may be converted to booleans.  The
00470        *  return value is that of the sentry state (true == okay).
00471       */
00472 #if __cplusplus >= 201103L
00473       explicit
00474 #endif
00475       operator bool() const
00476       { return _M_ok; }
00477     };
00478 
00479   //@{
00480   /**
00481    *  @brief  Character inserters
00482    *  @param  __out  An output stream.
00483    *  @param  __c  A character.
00484    *  @return  out
00485    *
00486    *  Behaves like one of the formatted arithmetic inserters described in
00487    *  std::basic_ostream.  After constructing a sentry object with good
00488    *  status, this function inserts a single character and any required
00489    *  padding (as determined by [22.2.2.2.2]).  @c __out.width(0) is then
00490    *  called.
00491    *
00492    *  If @p __c is of type @c char and the character type of the stream is not
00493    *  @c char, the character is widened before insertion.
00494   */
00495   template<typename _CharT, typename _Traits>
00496     inline basic_ostream<_CharT, _Traits>&
00497     operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c)
00498     { return __ostream_insert(__out, &__c, 1); }
00499 
00500   template<typename _CharT, typename _Traits>
00501     inline basic_ostream<_CharT, _Traits>&
00502     operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
00503     { return (__out << __out.widen(__c)); }
00504 
00505   // Specialization
00506   template <class _Traits>
00507     inline basic_ostream<char, _Traits>&
00508     operator<<(basic_ostream<char, _Traits>& __out, char __c)
00509     { return __ostream_insert(__out, &__c, 1); }
00510 
00511   // Signed and unsigned
00512   template<class _Traits>
00513     inline basic_ostream<char, _Traits>&
00514     operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
00515     { return (__out << static_cast<char>(__c)); }
00516 
00517   template<class _Traits>
00518     inline basic_ostream<char, _Traits>&
00519     operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
00520     { return (__out << static_cast<char>(__c)); }
00521   //@}
00522 
00523   //@{
00524   /**
00525    *  @brief  String inserters
00526    *  @param  __out  An output stream.
00527    *  @param  __s  A character string.
00528    *  @return  out
00529    *  @pre  @p __s must be a non-NULL pointer
00530    *
00531    *  Behaves like one of the formatted arithmetic inserters described in
00532    *  std::basic_ostream.  After constructing a sentry object with good
00533    *  status, this function inserts @c traits::length(__s) characters starting
00534    *  at @p __s, widened if necessary, followed by any required padding (as
00535    *  determined by [22.2.2.2.2]).  @c __out.width(0) is then called.
00536   */
00537   template<typename _CharT, typename _Traits>
00538     inline basic_ostream<_CharT, _Traits>&
00539     operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s)
00540     {
00541       if (!__s)
00542         __out.setstate(ios_base::badbit);
00543       else
00544         __ostream_insert(__out, __s,
00545                          static_cast<streamsize>(_Traits::length(__s)));
00546       return __out;
00547     }
00548 
00549   template<typename _CharT, typename _Traits>
00550     basic_ostream<_CharT, _Traits> &
00551     operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s);
00552 
00553   // Partial specializations
00554   template<class _Traits>
00555     inline basic_ostream<char, _Traits>&
00556     operator<<(basic_ostream<char, _Traits>& __out, const char* __s)
00557     {
00558       if (!__s)
00559         __out.setstate(ios_base::badbit);
00560       else
00561         __ostream_insert(__out, __s,
00562                          static_cast<streamsize>(_Traits::length(__s)));
00563       return __out;
00564     }
00565 
00566   // Signed and unsigned
00567   template<class _Traits>
00568     inline basic_ostream<char, _Traits>&
00569     operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s)
00570     { return (__out << reinterpret_cast<const char*>(__s)); }
00571 
00572   template<class _Traits>
00573     inline basic_ostream<char, _Traits> &
00574     operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s)
00575     { return (__out << reinterpret_cast<const char*>(__s)); }
00576   //@}
00577 
00578   // Standard basic_ostream manipulators
00579 
00580   /**
00581    *  @brief  Write a newline and flush the stream.
00582    *
00583    *  This manipulator is often mistakenly used when a simple newline is
00584    *  desired, leading to poor buffering performance.  See
00585    *  https://gcc.gnu.org/onlinedocs/libstdc++/manual/streambufs.html#io.streambuf.buffering
00586    *  for more on this subject.
00587   */
00588   template<typename _CharT, typename _Traits>
00589     inline basic_ostream<_CharT, _Traits>&
00590     endl(basic_ostream<_CharT, _Traits>& __os)
00591     { return flush(__os.put(__os.widen('\n'))); }
00592 
00593   /**
00594    *  @brief  Write a null character into the output sequence.
00595    *
00596    *  <em>Null character</em> is @c CharT() by definition.  For CharT
00597    *  of @c char, this correctly writes the ASCII @c NUL character
00598    *  string terminator.
00599   */
00600   template<typename _CharT, typename _Traits>
00601     inline basic_ostream<_CharT, _Traits>&
00602     ends(basic_ostream<_CharT, _Traits>& __os)
00603     { return __os.put(_CharT()); }
00604 
00605   /**
00606    *  @brief  Flushes the output stream.
00607    *
00608    *  This manipulator simply calls the stream's @c flush() member function.
00609   */
00610   template<typename _CharT, typename _Traits>
00611     inline basic_ostream<_CharT, _Traits>&
00612     flush(basic_ostream<_CharT, _Traits>& __os)
00613     { return __os.flush(); }
00614 
00615 #if __cplusplus >= 201103L
00616   /**
00617    *  @brief  Generic inserter for rvalue stream
00618    *  @param  __os  An input stream.
00619    *  @param  __x  A reference to the object being inserted.
00620    *  @return  os
00621    *
00622    *  This is just a forwarding function to allow insertion to
00623    *  rvalue streams since they won't bind to the inserter functions
00624    *  that take an lvalue reference.
00625   */
00626   template<typename _CharT, typename _Traits, typename _Tp>
00627     inline basic_ostream<_CharT, _Traits>&
00628     operator<<(basic_ostream<_CharT, _Traits>&& __os, const _Tp& __x)
00629     {
00630       __os << __x;
00631       return __os;
00632     }
00633 #endif // C++11
00634 
00635 _GLIBCXX_END_NAMESPACE_VERSION
00636 } // namespace std
00637 
00638 #include <bits/ostream.tcc>
00639 
00640 #endif  /* _GLIBCXX_OSTREAM */