CircBuf

Documentation

An implementation of a growable circular buffer of bytes. The CircBuf struct manages a buffer of bytes allocated on the heap. The buffer can be grown when needed and can return slices into its internal buffer that can be used for both normal IO (read and write) as well as vector IO (readv and writev).

Example

Below is a simple example of a server which makes use of a CircBuf to read messages from a client. It uses the vecio crate to call readv and writev on the socket. Messages are seperated by a vertical bar | and the server returns to the client the number of bytes in each message it receives.

```rust extern crate vecio; extern crate circbuf;

use std::thread; use std::net::{TcpListener, TcpStream}; use std::io::Write; use vecio::Rawv; use circbuf::CircBuf;

fn handleclient(mut stream: TcpStream) { let mut buf = CircBuf::new(); let mut nummessages = 0; // number of messages from the client let mut num_bytes = 0; // number of bytes read since last '|'

loop {
    // grow the buffer if it is less than half full
    if buf.len() > buf.avail() {
        buf.grow().unwrap();
    }

    let n;
    {
        n = match stream.readv(&buf.get_avail()) {
            Ok(n) => {
                if n == 0 {
                    // EOF
                    println!("client closed connection");
                    break;
                }
                n
            }
            Err(e) => panic!("got an error reading from a connection: {}", e),
        };
    }

    println!("read {} bytes from the client", n);

    // update write cursor
    buf.advance_write(n);

    // parse request from client for messages seperated by '|'
    loop {
        match buf.find_from_index(b'|', num_bytes) {
            Some(i) => {
                // update read cursor past '|' and reset num_bytes since last '|'
                buf.advance_read(i + 1);
                num_bytes = 0;
                num_messages += 1;

                let response = format!("Message {} contained {} bytes\n", num_messages, i - 1); // don't inclue '|' in num_bytes
                match stream.write(&response.as_bytes()) {
                    Ok(n) => {
                        println!("wrote {} bytes to the client", n);
                    }
                    Err(e) => panic!("got an error writing to connection: {}", e),
                }
            }
            None => break,
        }
    }
}

}

fn main() { let listener = TcpListener::bind("127.0.0.1:8888").unwrap(); for stream in listener.incoming() { match stream { Ok(stream) => { thread::spawn(move || handle_client(stream)); } Err(e) => panic!("got an error accepting connection: {}", e), } } } ```