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//! Write packets to a stream.
use crate::{packets::ProtocolPacket, read::MAXIMUM_UNCOMPRESSED_LENGTH};
use async_compression::tokio::bufread::ZlibEncoder;
use azalea_buf::McBufVarWritable;
use azalea_crypto::Aes128CfbEnc;
use log::trace;
use std::fmt::Debug;
use thiserror::Error;
use tokio::io::{AsyncReadExt, AsyncWrite, AsyncWriteExt};
/// Prepend the length of the packet to it.
fn frame_prepender(mut data: Vec<u8>) -> Result<Vec<u8>, std::io::Error> {
let mut buf = Vec::new();
(data.len() as u32).var_write_into(&mut buf)?;
buf.append(&mut data);
Ok(buf)
}
#[derive(Error, Debug)]
pub enum PacketEncodeError {
#[error("{0}")]
Io(#[from] std::io::Error),
#[error("Packet too big (is {actual} bytes, should be less than {maximum}): {packet_string}")]
TooBig {
actual: usize,
maximum: usize,
packet_string: String,
},
}
fn packet_encoder<P: ProtocolPacket + std::fmt::Debug>(
packet: &P,
) -> Result<Vec<u8>, PacketEncodeError> {
let mut buf = Vec::new();
packet.id().var_write_into(&mut buf)?;
packet.write(&mut buf)?;
if buf.len() > MAXIMUM_UNCOMPRESSED_LENGTH as usize {
return Err(PacketEncodeError::TooBig {
actual: buf.len(),
maximum: MAXIMUM_UNCOMPRESSED_LENGTH as usize,
packet_string: format!("{packet:?}"),
});
}
Ok(buf)
}
#[derive(Error, Debug)]
pub enum PacketCompressError {
#[error("{0}")]
Io(#[from] std::io::Error),
}
async fn compression_encoder(
data: &[u8],
compression_threshold: u32,
) -> Result<Vec<u8>, PacketCompressError> {
let n = data.len();
// if it's less than the compression threshold, don't compress
if n < compression_threshold as usize {
let mut buf = Vec::new();
0.var_write_into(&mut buf)?;
buf.write_all(data).await?;
Ok(buf)
} else {
// otherwise, compress
let mut deflater = ZlibEncoder::new(data);
// write deflated data to buf
let mut buf = Vec::new();
deflater.read_to_end(&mut buf).await?;
Ok(buf)
}
}
pub async fn write_packet<P, W>(
packet: &P,
stream: &mut W,
compression_threshold: Option<u32>,
cipher: &mut Option<Aes128CfbEnc>,
) -> std::io::Result<()>
where
P: ProtocolPacket + Debug,
W: AsyncWrite + Unpin + Send,
{
trace!("Sending packet: {:?}", packet);
let mut buf = packet_encoder(packet).unwrap();
if let Some(threshold) = compression_threshold {
buf = compression_encoder(&buf, threshold).await.unwrap();
}
buf = frame_prepender(buf).unwrap();
// if we were given a cipher, encrypt the packet
if let Some(cipher) = cipher {
azalea_crypto::encrypt_packet(cipher, &mut buf);
}
stream.write_all(&buf).await
}
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