cpp/io/basic ios/tie

Manages the tied stream. A tied stream is an output stream which is synchronized with the sequence controlled by the stream buffer (rdbuf), that is, is called on the tied stream before any input/output operation on.

@1@ Returns the current tied stream. If there is no tied stream, a null pointer is returned.

@2@ Sets the current tied stream to. Returns the tied stream before the operation. If there is no tied stream, a null pointer is returned. If is not null and  is reachable by traversing the linked list of tied stream objects starting from, the behavior is undefined.

Return value
The tied stream, or a null pointer if there was no tied stream.