Add UdpSocket::peek method

[al8n]

The mio::net::UdpSocket supports peek already, but tokio::net::UdpSocket is missing this method.

[Darksonn]

Thanks for the PR!

Currently, this method is based on the mio method; I see the docs are taken from there. However, we generally try to follow the methods in std instead. I notice that std has both peek and peek_from, so we should also have both. Furthermore, to support async usage, we should have both an async fn and a poll_* method.

Based on the above, I think we should have the following methods:

• peek taking &mut [u8]
• peek_from taking &mut [u8]
• poll_peek taking &mut ReadBuf<'_>
• poll_peek_from taking &mut ReadBuf<'_>

For inspiration, please see the TcpStream::peek and TcpStream::poll_peek methods. The documentation should be similar to them.

[al8n]

Thanks for the PR!

Currently, this method is based on the mio method; I see the docs are taken from there. However, we generally try to follow the methods in std instead. I notice that std has both peek and peek_from, so we should also have both. Furthermore, to support async usage, we should have both an async fn and a poll_* method.

Based on the above, I think we should have the following methods:

• peek taking &mut [u8]
• peek_from taking &mut [u8]
• poll_peek taking &mut ReadBuf<'_>
• poll_peek_from taking &mut ReadBuf<'_>

For inspiration, please see the TcpStream::peek and TcpStream::poll_peek methods. The documentation should be similar to them.

peek_from and poll_peek_from are already there, I will add poll_peek.

The document is copied from the peek_from method. Should I also change the document for peek_from and poll_peek_from?

[Darksonn]

Sorry, my first response was inaccurate. What you have now looks very reasonable. Can you add try_peek too?

[al8n]

Sorry, my first response was inaccurate. What you have now looks very reasonable. Can you add try_peek too?

Yes, add it.

[Darksonn]

Thanks!