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

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< cpp‎ | io‎ | basic syncbuf

basic_syncbuf() : basic_syncbuf( nullptr ) | (1) |
explicit basic_syncbuf( streambuf_type* obuf ) : basic_syncbuf( obuf, Allocator() ) {} | (2) |
basic_syncbuf( streambuf_type* obuf, const Allocator& a ); | (3) |
basic_syncbuf( basic_syncbuf&& rhs ); | (4) |

1) Default constructor: creates an instance of `std::basic_syncbuf` with emit-on-sync policy set to false, wrapped streambuffer set to nullptr, and using default-constructed `Allocator` as the allocator for temporary storage.
2,3) Creates an instance of `std::basic_syncbuf` with emit-on-sync policy set to false, wrapped streambuffer set to obuf, and using a as the allocator for temporary storage.
4) Move constructor: move-constructs a `std::basic_syncbuf` object by moving all contents from another `std::basic_syncbuf` object rhs, including the temporary storage, the wrapped stream pointer, policy, and all other state (such as the mutex pointer). After move, rhs is not associated with a stream, and rhs.get_wrapped() == nullptr. The put area member pointers of the base class std::basic_streambuf of rhs are guaranteed to be null. Destroying a moved-from rhs will not produce any output.

### Parameters

obuf | - | pointer to the std::basic_streambuf to wrap
a | - | the allocator to use for temporary storage
rhs | - | another `std::basic_syncbuf` to move from

### Exceptions

2,3) May throw std::bad_alloc from the constructor of the internal temporary storage or std::system_error from the mutex construction.

### Notes

Typically called by the appropriate constructors of std::basic_osyncstream.

### Example

| This section is incomplete Reason: no example

### See also

sync [virtual] | synchronizes the buffers with the associated character sequence (virtual protected member function of `std::basic_streambuf<CharT,Traits>`)
emit | atomically transmits the entire internal buffer to the wrapped streambuf (public member function)

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