Expand description
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
(e.g. read
and write
) as well as vector IO (readv
and writev
).
Feature flags
bytes
: Adds a dependency on thebytes
crate and implements theBuf
andBufMut
traits from that crate.
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.
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) => {
// 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),
}
}
}
Structs
- Circular Buffer
Enums
- Circular Buffer Error
Constants
- Default size of the circular buffer is 1 page
- Double the size of the buffer by default when growing it