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      std::basic_stringbuf<CharT,Traits,Allocator>::basic_stringbuf

      From cppreference.com
      <cpp‎ |io‎ |basic stringbuf
       
       
       
       
      (1)
      explicit basic_stringbuf(std::ios_base::openmode which=
                                   std::ios_base::in|std::ios_base::out);
      		(until C++11)
      explicit basic_stringbuf(std::ios_base::openmode which);
      		(since C++11)
      basic_stringbuf()
         : basic_stringbuf(std::ios_base::in|std::ios_base::out){}
      		 (2)(since C++11)
      explicit

          basic_stringbuf(conststd::basic_string<CharT, Traits, Allocator>& s,
                           std::ios_base::openmode which=

                               std::ios_base::in|std::ios_base::out);
      		 (3)
      explicit basic_stringbuf(std::basic_string<CharT, Traits, Allocator>&& s,

                               std::ios_base::openmode which=

                                   std::ios_base::in|std::ios_base::out);
      		 (4)(since C++20)
      basic_stringbuf(std::ios_base::openmode which,const Allocator& a);
      		 (5)(since C++20)
      explicit basic_stringbuf(const Allocator& a)
         : basic_stringbuf(std::ios_base::in|std::ios_base::out, a){}
      		 (6)(since C++20)
      template<class SAlloc>

      explicit basic_stringbuf(conststd::basic_string<CharT, Traits, SAlloc>& s,
                               std::ios_base::openmode which=

                                   std::ios_base::in|std::ios_base::out);
      		 (7)(since C++20)
      template<class SAlloc>

      basic_stringbuf(conststd::basic_string<CharT, Traits, SAlloc>& s,

                       std::ios_base::openmode which,const Allocator& a);
      		 (8)(since C++20)
      template<class SAlloc>

      basic_stringbuf(conststd::basic_string<CharT, Traits, SAlloc>& s,
                       const Allocator& a)

         : basic_stringbuf( s,std::ios_base::in|std::ios_base::out, a){}
      		 (9)(since C++20)
      template<class StringViewLike>

      explicit basic_stringbuf(const StringViewLike& t,
                               std::ios_base::openmode which=

                                   std::ios_base::in|std::ios_base::out);
      		 (10)(since C++26)
      template<class StringViewLike>

      basic_stringbuf(const StringViewLike& t,

                       std::ios_base::openmode which,const Allocator& a);
      		 (11)(since C++26)
      template<class StringViewLike>
      basic_stringbuf(const StringViewLike& t,const Allocator& a);
      		 (12)(since C++26)
      basic_stringbuf( basic_stringbuf&& rhs);
      		 (13)(since C++11)
      basic_stringbuf( basic_stringbuf&& rhs,const Allocator& a);
      		 (14)(since C++20)
      basic_stringbuf(const basic_stringbuf& rhs)= delete;
      		 (15)(since C++11)

      Thestd::basic_streambuf base and theexposition-only data membersbuf andmode are initialized as follows.

      After initializing these subobjects, overloads(3-12) initialize the input and output sequences as if by callinginit_buf_ptrs().

       Overload  std::basic_streambuf base bufmode
      (1)default-initializedimplementation-defined
      (see below)      		which
      (2) std::ios_base::in|
         std::ios_base::out       
      (3)swhich
      (4)std::move(s)
      (5)a
      (6) std::ios_base::in|
         std::ios_base::out
      (7)swhich
      (8){s, a}
      (9) std::ios_base::in|
         std::ios_base::out
      (10){sv, Allocator()}which
      (11){sv, a}
      (12) std::ios_base::in|
         std::ios_base::out
      (13)rhs
      (copy constructed)      		std::move(rhs).str()rhs.mode
      (14) {std::move(rhs).str(), a} 
      1,2) Overload(1)(until C++11)(2)(since C++11) is the default constructor. It is implementation-defined whether the sequence pointers (eback(),gptr(),egptr(),pbase(),pptr(),epptr()) are initialized to null pointers.
      5,6) When the construction is complete,str.empty() istrue.
      7) This overload participates in overload resolution only ifstd::is_same_v<SAlloc, Allocator> isfalse.
      10-12) Implicitly convertst to a string viewsv as if bystd::basic_string_view<CharT, Traits> sv= t;, then it is used as above in the table.
      These overloads participate in overload resolution only ifstd::is_convertible_v<const StringViewLike&,
                           std::basic_string_view<CharT, Traits>>       istrue.
      13,14) Overload(13) is the move constructor. It is implementation-defined whether the six sequence pointers in*this obtain the values whichrhs had.
      When the construction is complete,rhs is empty but usable, and
      • Letrhs_p refer to the state ofrhs just prior to this construction, the following expressions will evaluate totrue:
      • str()== rhs_p.str()
      • getloc()== rhs_p.getloc()
      • gptr()- eback()== rhs_p.gptr()- rhs_p.eback()
      • egptr()- eback()== rhs_p.egptr()- rhs_p.eback()
      • pptr()- pbase()== rhs_p.pptr()- rhs_p.pbase()
      • epptr()- pbase()== rhs_p.epptr()- rhs_p.pbase()
      • Letrhs_a refer to the state ofrhs just after this construction, the following expressions will evaluate totrue:
      • !eback()|| eback()!= rhs_a.eback()
      • !gptr()|| gptr()!= rhs_a.gptr()
      • !egptr()|| egptr()!= rhs_a.egptr()
      • !pbase()|| pbase()!= rhs_a.pbase()
      • !pptr()|| pptr()!= rhs_a.pptr()
      • !epptr()|| epptr()!= rhs_a.epptr()
      15) The copy constructor is deleted;std::basic_stringbuf is notCopyConstructible.

      Contents

      [edit]Parameters

      s - astd::basic_string used to initialize the buffer
      t - an object (convertible tostd::basic_string_view) used to initialize the buffer
      a - another allocator used to construct the internalstd::basic_string
      rhs - anotherbasic_stringbuf
      which - specifies stream open mode. It is bitmask type, the following constants are defined:
      Constant Explanation
      app seek to the end of stream before each write
      binary open inbinary mode
      in open for reading
      out open for writing
      trunc discard the contents of the stream when opening
      ate seek to the end of stream immediately after open
      noreplace(C++23) open in exclusive mode

      [edit]Notes

      Typically called by the constructor ofstd::basic_stringstream.

      The level of support for the open modes other thanstd::ios_base::in andstd::ios_base::out varies among implementations. C++11 explicitly specifies the support forstd::ios_base::ate instr() and in this constructor, butstd::ios_base::app,std::ios_base::trunc, andstd::ios_base::binary have different effects on different implementations.

      Feature-test macroValueStdFeature
      __cpp_lib_sstream_from_string_view202306L(C++26)Interfacing string streams withstd::string_view

      [edit]Example

      Demonstrates calling the constructor ofstd::basic_stringbuf directly:

      Run this code
      #include <iostream>#include <sstream> int main(){// default constructor (mode = in | out)std::stringbuf buf1;    buf1.sputc('1');std::cout<<&buf1<<'\n'; // string constructor in at-end mode (C++11)std::stringbuf buf2("test",std::ios_base::in|std::ios_base::out|std::ios_base::ate);    buf2.sputc('1');std::cout<<&buf2<<'\n'; // append mode test (results differ among compilers)std::stringbuf buf3("test",std::ios_base::in|std::ios_base::out|std::ios_base::app);    buf3.sputc('1');    buf3.pubseekpos(1);    buf3.sputc('2');std::cout<<&buf3<<'\n';}

      Output:

      1test1est12 (Sun Studio) 2st1 (GCC)

      [edit]Defect reports

      The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

      DRApplied toBehavior as publishedCorrect behavior
      LWG 432C++981. overload(1) allocated no array object
      2. overload(3) did not specify how the input
          and output sequences are initialized      		1. removed the limitation
      2. specified
      LWG 562C++98overload(3) setepptr() to point one past the last underlying
      character ifbool(which&std::ios_base::out)==true      		epptr() can be set
      beyond that position
      P0935R0C++11the default constructor was explicitmade implicit

      [edit]See also

      constructs the string stream
      (public member function ofstd::basic_stringstream<CharT,Traits,Allocator>)[edit]
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/io/basic_stringbuf/basic_stringbuf&oldid=158136"
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