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

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< cpp‎ | io‎ | basic osyncstream

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 <string_view>
    #include <syncstream>
    #include <iostream>
    #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:
    ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
    ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒
    ▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓
    ████████████████████████████████████████████████████████████████████████████████████████████████████

    Lack of synchronization may cause some interference on output:
    ████▓▓██▒▒▒▒▓▓██░░▒▒██░░▒▒░░░░▒▒░░▓▓▒▒██░░████████████▓▓██████▓▓▒▒▓▓██░░████▓▓▓▓██▒▒░░░░░░░░▓▓░░▓▓██▒▒▒▒▒▒▒▒▓▓██▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒░░▒▒▒▒░░▒▒▒▒▒▒▒▒▒▒▓▓▒▒▒▒▒▒▒▒▒▒▒▒██░░░░░░░░▓▓▓▓▓▓▓▓▓▓▓▓▓▓░░▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓████████▓▓▓▓▓▓▓▓▓▓▓▓░░▓▓▓▓
    ▒▒▒▒██░░██████████████████████████░░░░░░░░░░░░░░██░░▒▒░░░░░░██████████████████
    ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒░░▒▒░░░░░░░░░░░░░░░░░░░░░░░░░░░░▒▒▒▒▒▒
    ░░░░░░

### See also

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

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