std::basic_ostringstream<CharT,Traits,Allocator>::basic_ostringstream (3) - Linux Manuals

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

NAME

std::basic_ostringstream<CharT,Traits,Allocator>::basic_ostringstream - std::basic_ostringstream<CharT,Traits,Allocator>::basic_ostringstream

Synopsis

basic_ostringstream() : basic_ostringstream(ios_base::out) { } (1) (since C++11)
explicit basic_ostringstream( ios_base::openmode mode = ios_base::out ); (until C++11)
explicit basic_ostringstream( ios_base::openmode mode ); (since C++11)
explicit basic_ostringstream( const std::basic_string<CharT,Traits,Allocator>& str, (2) (3)
ios_base::openmode mode = ios_base::out );
basic_ostringstream( basic_ostringstream&& other ); (4) (since C++11)

Constructs new string stream.
1) Default constructor. Constructs new underlying string device with the default open mode
2) Constructs new underlying string device. The underlying basic_stringbuf object is constructed as basic_stringbuf<Char,Traits,Allocator>(mode | ios_base::out).
3) Uses a copy of str as initial contents of the underlying string device. The underlying basic_stringbuf object is constructed as basic_stringbuf<Char,Traits,Allocator>(str, mode | ios_base::out).
4) Move constructor. Constructs the string stream with the state of other using move semantics.

Parameters

str - string to use as initial contents of the string stream
        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
mode - binary open in binary_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

other - another string stream to use as source

Notes

Construction of one-off basic_ostringstream objects in a tight loop, such as when used for string conversion, may be significantly more costly than calling str to reuse the same object.

Defect reports

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

DR Applied to Behavior as published Correct behavior
P0935R0 C++11 default constructor was explicit made implicit

Example

// Run this code

  #include <iostream>
  #include <sstream>
  int main()
  {
      // default constructor (input/output stream)
      std::stringstream buf1;
      buf1 << 7;
      int n = 0;
      buf1 >> n;
      std::cout << "buf1 = " << buf1.str() << " n = " << n << '\n';

      // input stream
      std::istringstream inbuf("-10");
      inbuf >> n;
      std::cout << "n = " << n << '\n';

      // output stream in append mode (C++11)
      std::ostringstream buf2("test", std::ios_base::ate);
      buf2 << '1';
      std::cout << buf2.str() << '\n';
  }

Output:

  buf1 = 7 n = 7
  n = -10
  test1