canlink-tscan 0.3.3

use serde::{de::DeserializeOwned, Serialize};
use std::io::{self, Read, Write};

pub const MAX_FRAME_SIZE: usize = 1024 * 1024;

pub fn write_frame<W: Write, T: Serialize>(writer: &mut W, value: &T) -> io::Result<()> {
    let payload = serde_json::to_vec(value)
        .map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err.to_string()))?;
    if payload.len() > MAX_FRAME_SIZE {
        return Err(io::Error::new(
            io::ErrorKind::InvalidData,
            "frame too large",
        ));
    }
    let len = payload.len() as u32;
    writer.write_all(&len.to_le_bytes())?;
    writer.write_all(&payload)?;
    writer.flush()?;
    Ok(())
}

pub fn read_frame<R: Read, T: DeserializeOwned>(reader: &mut R) -> io::Result<T> {
    let mut len_buf = [0u8; 4];
    reader.read_exact(&mut len_buf)?;
    let len = u32::from_le_bytes(len_buf) as usize;
    if len > MAX_FRAME_SIZE {
        return Err(io::Error::new(
            io::ErrorKind::InvalidData,
            "frame too large",
        ));
    }
    let mut payload = vec![0u8; len];
    reader.read_exact(&mut payload)?;
    serde_json::from_slice(&payload)
        .map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err.to_string()))
}