Tcp socket from std stream

[AtulJatia]

convert std TcpStream into TcpSocket

This converts the TcpStream into the platform specific raw_fd(unix) / raw_socket(windows)
and then converts them into the TcpSocket as TcpSocket implements the
FromRawFd(unix) and FromRawSocket(windows) traits.

Fixes: #3734

[Darksonn]

Thanks for doing this!

[Darksonn]

I have some improvements to the documentation:

• We typically wrap the text such that it goes all the way out to 80 characters wide. If you want to make a newline that shows up in the documentation, you need an empty line, as it otherwise just concatenates the lines.
• I would like TcpStream to be a link, and TcpSocket should be surrounded by backticks to display it as code.
• You do not have to explain how it does the conversion.
• The documentation should make it clear that this is intended for usage together with socket2, and that the socket must not be in a connected state.

[AtulJatia]

Thanks for your quick reply. I'll go over all the changes suggested and raise another request.

[Darksonn]

You should not create a new PR. Just push more commits to your tcp-socket-from-std-stream branch.

[Darksonn]

I would like to use socket2 in this example. Your example is currently converting a socket that is in a connected state, which you aren't supposed to do.

[Darksonn]

The conversion always succeeds, so no need for a Result.

Suggested change

	pub fn from_std_stream(std_stream: std::net::TcpStream) -> io::Result<TcpSocket> {
	pub fn from_std_stream(std_stream: std::net::TcpStream) -> TcpSocket {

[Darksonn]

I prefer simplifying it a bit to this.

Suggested change

	/// let stream = TcpStream::from(socket2_socket);
	///
	/// let socket = TcpSocket::from_std_stream(stream)?;
	/// let socket = TcpSocket::from_std_stream(socket2_socket.into())?;

[Darksonn]

This doesn't do anything.

Suggested change

/// # drop(socket);

[Darksonn]

Suggested change

	/// Converts a `socket2::Socket` into a `TcpSocket`. The socket2 socket
	/// needs to be in a disconnected state when passed as an argument.
	/// Converts a [`std::net::TcpStream`] into a `TcpSocket`. The provided
	/// socket must not have been connected prior to calling this function. This
	/// function is typically used together with crates such as [`socket2`] to
	/// configure socket options that are not available on `TcpSocket`.
	///
	/// [`std::net::TcpStream`]: struct@std::net::TcpStream
	/// [`socket2`]: https://docs.rs/socket2/

[Darksonn]

Your example doesn't compile.

Suggested change

	/// async fn main() -> io::Result<()> {
	/// async fn main() -> std::io::Result<()> {

[Darksonn]

Thanks for doing this!