Endpoint requirements

A type X meets the Endpoint requirements if it satisfies the requirements of Destructible (C++Std [destructible]), DefaultConstructible (C++Std [defaultconstructible]), CopyConstructible (C++Std [copyconstructible]), and CopyAssignable (C++Std [copyassignable]), as well as the additional requirements listed below.

The default constructor and move operations of the type X shall not exit via an exception.

In the table below, a denotes a (possibly const) value of type X, and u denotes an identifier.

Table 12. Endpoint requirements

expression	type	assertion/note pre/post-conditions
`X::protocol_type`	type meeting `Protocol` requirements
`a.protocol()`	`protocol_type`

In the table below, a denotes a (possibly const) value of type X, b denotes a value of type X, and s denotes a (possibly const) value of a type that is convertible to size_t and denotes a size in bytes.

Table 13. Endpoint requirements for extensible implementations

expression	type	assertion/note pre/post-conditions
`a.data()`	`const void*`	Returns a pointer suitable for passing as the address argument to functions such as POSIX `connect()`, or as the dest_addr argument to functions such as POSIX `sendto()`. The implementation shall perform a `static_cast` on the pointer to convert it to `const sockaddr*`.
`b.data()`	`void*`	Returns a pointer suitable for passing as the address argument to functions such as POSIX `accept()`, `getpeername()`, `getsockname()` and `recvfrom()`. The implementation shall perform a `static_cast` on the pointer to convert it to `sockaddr*`.
`a.size()`	`size_t`	Returns a value suitable for passing as the address_len argument to functions such as POSIX `connect()`, or as the dest_len argument to functions such as POSIX `sendto()`, after appropriate integer conversion has been performed.
`b.resize(s)`		pre: `s >= 0` post: `a.size() == s` Passed the value contained in the address_len argument to functions such as POSIX `accept()`, `getpeername()`, `getsockname()` and `recvfrom()`, after successful completion of the function. Permitted to throw an exception if the protocol associated with the endpoint object `a` does not support the specified size.
`a.capacity()`	`size_t`	Returns a value suitable for passing as the address_len argument to functions such as POSIX `accept()`, `getpeername()`, `getsockname()` and `recvfrom()`, after appropriate integer conversion has been performed.