Object handle service requirements

An object handle service must meet the requirements for a handle service, as well as the additional requirements listed below.

In the table below, X denotes an object handle service class, a denotes a value of type X, b denotes a value of type X::implementation_type, ec denotes a value of type error_code, and wh denotes a value meeting WaitHandler requirements.

Table 21. ObjectHandleService requirements

expression	return type	assertion/note pre/post-condition
`a.wait(b, ec);`	`error_code`	pre: `a.is_open(b)`. Synchronously waits for the object represented by handle `b` to become signalled.
`a.async_wait(b, wh);`	`void`	pre: `a.is_open(b)`. Initiates an asynchronous operation to wait for the object represented by handle `b` to become signalled. The operation is performed via the `io_service` object `a.get_io_service()` and behaves according to asynchronous operation requirements.