Gettable socket option requirements

In the table below, X denotes a socket option class, a denotes a value of X, p denotes a value that meets the protocol requirements, and u denotes an identifier.

Table 12. GettableSocketOption requirements

expression	type	assertion/note pre/post-conditions
`a.level(p);`	`int`	Returns a value suitable for passing as the level argument to POSIX `getsockopt()` (or equivalent).
`a.name(p);`	`int`	Returns a value suitable for passing as the option_name argument to POSIX `getsockopt()` (or equivalent).
`a.data(p);`	a pointer, convertible to `void*`	Returns a pointer suitable for passing as the option_value argument to POSIX `getsockopt()` (or equivalent).
`a.size(p);`	`size_t`	Returns a value suitable for passing as the option_len argument to POSIX `getsockopt()` (or equivalent), after appropriate integer conversion has been performed.
`a.resize(p, s);`		post: `a.size(p) == s`. Passed the value contained in the option_len argument to POSIX `getsockopt()` (or equivalent) after successful completion of the function. Permitted to throw an exception if the socket option object `a` does not support the specified size.