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
).
bytes
supportIf the bytes
feature flag is enabled, then the bytes
crate will be added as a dependency and the Buf
and BufMut
traits implemented for
CircBuf
. The optional vectored read/write functions are implemented, allowing you to use
the CircBuf
for efficient vectored IO operations with libraries such as tokio
. See
for example the read_buf
and write_buf
methods, which can accept a CircBuf
when the bytes
feature flag is enabled.
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
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.
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 handle_client(mut stream: TcpStream) {
let mut buf = CircBuf::new();
let mut num_messages = 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) => {
let response = format!("Message {} contained {} bytes\n", num_messages, num_bytes + i - 1); // don't include '|' in number of bytes
match stream.write(&response.as_bytes()) {
Ok(n) => {
println!("wrote {} bytes to the client", n);
// update read cursor past '|' and reset num_bytes since last '|'
buf.advance_read(i + 1);
num_bytes = 0;
num_messages += 1;
}
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),
}
}
}