Settable 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 29. SettableSocketOption requirements

expression	type	assertion/note pre/post-conditions
`a.level(p);`	`int`	Returns a value suitable for passing as the level argument to POSIX `setsockopt()` (or equivalent).
`a.name(p);`	`int`	Returns a value suitable for passing as the option_name argument to POSIX `setsockopt()` (or equivalent).
`const X& u = a; u.data(p);`	a pointer, convertible to `const void*`	Returns a pointer suitable for passing as the option_value argument to POSIX `setsockopt()` (or equivalent).
`a.size(p);`	`size_t`	Returns a value suitable for passing as the option_len argument to POSIX `setsockopt()` (or equivalent), after appropriate integer conversion has been performed.