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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Input/output library

I/O manipulators

Print functions (C++23)

C-style I/O

Buffers

basic_streambuf

basic_filebuf

basic_stringbuf

basic_spanbuf (C++23)

strstreambuf (C++98/26*)

basic_syncbuf (C++20)

Streams

Abstractions

ios_base

basic_ios

basic_istream

basic_ostream

basic_iostream

File I/O

basic_ifstream

basic_ofstream

basic_fstream

String I/O

basic_istringstream

basic_ostringstream

basic_stringstream

Array I/O

basic_ispanstream (C++23)

basic_ospanstream (C++23)

basic_spanstream (C++23)

istrstream (C++98/26*)

ostrstream (C++98/26*)

strstream (C++98/26*)

Synchronized Output

basic_osyncstream (C++20)

Types

streamoff

streamsize

fpos

Error category interface

iostream_category (C++11)

io_errc (C++11)

 

std::basic_osyncstream

Public member functions

basic_osyncstream::basic_osyncstream (C++20)

basic_osyncstream::operator= (C++20)

basic_osyncstream::~basic_osyncstream (C++20)

basic_osyncstream::rdbuf (C++20)

basic_osyncstream::get_wrapped (C++20)

basic_osyncstream::emit (C++20)

 

basic_osyncstream( streambuf_type* buf, const Allocator& a );	(1)
explicit basic_osyncstream( streambuf_type* buf );	(2)
basic_osyncstream( std::basic_ostream<CharT, Traits>& os, const Allocator& a );	(3)
explicit basic_osyncstream( std::basic_ostream<CharT, Traits>& os );	(4)
basic_osyncstream( std::basic_osyncstream&& other ) noexcept;	(5)

Constructs new synchronized output stream.

1-4) Constructs the private member std::basic_syncbuf using the buffer and the allocator provided, and initializes the base class with a pointer to the member std::basic_streambuf.

5) Move constructor. Move-constructs the std::basic_ostream base and the std::basic_syncbuf member from the corresponding subobjects of other, then calls set_rdbuf with the pointer to the newly-constructed underlying std::basic_syncbuf to complete the initialization of the base. After this move constructor, other.get_wrapped() returns nullptr and destruction of other produces no output.

Parameters

buf	-	pointer to the std::basic_streambuf that will be wrapped
os	-	reference to a std::basic_ostream, whose rdbuf() will be wrapped
a	-	the allocator to pass to the constructor of the member std::basic_syncbuf
other	-	another osyncstream to move from

Example

Run this code

#include <iostream>
#include <string_view>
#include <syncstream>
#include <thread>
 
void worker(const int id, std::ostream &os)
{
    std::string_view block;
    switch (id)
    {
        default: [[fallthrough]];
        case 0: block = "██";
                break;
        case 1: block = "▓▓";
                break;
        case 2: block = "▒▒";
                break;
        case 3: block = "░░";
                break;
    }
    for (int i = 1; i <= 50; ++i)
        os << block << std::flush;
    os << std::endl;
}
 
int main()
{
    std::cout << "Synchronized output should not cause any interference:" << std::endl;
    {
        auto scout1 = std::osyncstream{std::cout};
        auto scout2 = std::osyncstream{std::cout};
        auto scout3 = std::osyncstream{std::cout};
        auto scout4 = std::osyncstream{std::cout};
        auto w1 = std::jthread{worker, 0, std::ref(scout1)};
        auto w2 = std::jthread{worker, 1, std::ref(scout2)};
        auto w3 = std::jthread{worker, 2, std::ref(scout3)};
        auto w4 = std::jthread{worker, 3, std::ref(scout4)};
    }
 
    std::cout << "\nLack of synchronization may cause some interference on output:"
              << std::endl;
    {
        auto w1 = std::jthread{worker, 0, std::ref(std::cout)};
        auto w2 = std::jthread{worker, 1, std::ref(std::cout)};
        auto w3 = std::jthread{worker, 2, std::ref(std::cout)};
        auto w4 = std::jthread{worker, 3, std::ref(std::cout)};
    }
}

Possible output:

Synchronized output should not cause any interference:
░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
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████████████████████████████████████████████████████████████████████████████████████████████████████
 
Lack of synchronization may cause some interference on output:
████▓▓██▒▒▒▒▓▓██░░▒▒██░░▒▒░░░░▒▒░░▓▓▒▒██░░████████████▓▓██████▓▓▒▒▓▓██░░████▓▓▓▓██▒▒░░░░░░░░▓▓░░▓▓██▒▒▒▒▒▒▒▒▓▓██▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒░░▒▒▒▒░░▒▒▒▒▒▒▒▒▒▒▓▓▒▒▒▒▒▒▒▒▒▒▒▒██░░░░░░░░▓▓▓▓▓▓▓▓▓▓▓▓▓▓░░▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓████████▓▓▓▓▓▓▓▓▓▓▓▓░░▓▓▓▓
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See also

(constructor)

constructs a basic_syncbuf object (public member function of std::basic_syncbuf<CharT,Traits,Allocator>)