NAME

std::basic_osyncstream::basic_osyncstream - std::basic_osyncstream::basic_osyncstream

Synopsis

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:
████▓▓██▒▒▒▒▓▓██░░▒▒██░░▒▒░░░░▒▒░░▓▓▒▒██░░████████████▓▓██████▓▓▒▒▓▓██░░████▓▓▓▓██▒▒░░░░░░░░▓▓░░▓▓██▒▒▒▒▒▒▒▒▓▓██▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒░░▒▒▒▒░░▒▒▒▒▒▒▒▒▒▒▓▓▒▒▒▒▒▒▒▒▒▒▒▒██░░░░░░░░▓▓▓▓▓▓▓▓▓▓▓▓▓▓░░▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓████████▓▓▓▓▓▓▓▓▓▓▓▓░░▓▓▓▓
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See also

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