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//! Utilities for reading and writing for the Minecraft protocol
use std::{future::Future, io::Write};
use async_trait::async_trait;
use byteorder::{BigEndian, WriteBytesExt};
use tokio::io::{AsyncRead, AsyncReadExt};
// const DEFAULT_NBT_QUOTA: u32 = 2097152;
const MAX_STRING_LENGTH: u16 = 32767;
// const MAX_COMPONENT_STRING_LENGTH: u32 = 262144;
#[async_trait]
pub trait Writable {
fn write_collection<F, T>(
&mut self,
collection: Vec<T>,
writer: F,
) -> Result<(), std::io::Error>
where
F: FnOnce(&mut Self, T) -> Result<(), std::io::Error> + Copy,
Self: Sized;
fn write_byte(&mut self, n: u8) -> Result<(), std::io::Error>;
fn write_bytes(&mut self, bytes: &[u8]) -> Result<(), std::io::Error>;
fn write_varint(&mut self, value: i32) -> Result<(), std::io::Error>;
fn write_utf_with_len(&mut self, string: &str, len: usize) -> Result<(), std::io::Error>;
fn write_utf(&mut self, string: &str) -> Result<(), std::io::Error>;
fn write_short(&mut self, n: u16) -> Result<(), std::io::Error>;
fn write_byte_array(&mut self, bytes: &[u8]) -> Result<(), std::io::Error>;
}
#[async_trait]
impl Writable for Vec<u8> {
fn write_collection<F, T>(
&mut self,
collection: Vec<T>,
writer: F,
) -> Result<(), std::io::Error>
where
F: FnOnce(&mut Self, T) -> Result<(), std::io::Error> + Copy,
Self: Sized,
{
self.write_varint(collection.len() as i32)?;
for item in collection {
writer(self, item)?;
}
Ok(())
}
fn write_byte(&mut self, n: u8) -> Result<(), std::io::Error> {
WriteBytesExt::write_u8(self, n)
}
fn write_bytes(&mut self, bytes: &[u8]) -> Result<(), std::io::Error> {
Ok(self.extend_from_slice(bytes))
}
fn write_varint(&mut self, mut value: i32) -> Result<(), std::io::Error> {
let mut buffer = [0];
if value == 0 {
self.write_all(&buffer).unwrap();
}
while value != 0 {
buffer[0] = (value & 0b0111_1111) as u8;
value = (value >> 7) & (i32::max_value() >> 6);
if value != 0 {
buffer[0] |= 0b1000_0000;
}
self.write_all(&buffer)?;
}
Ok(())
}
fn write_utf_with_len(&mut self, string: &str, len: usize) -> Result<(), std::io::Error> {
if string.len() > len {
panic!(
"String too big (was {} bytes encoded, max {})",
string.len(),
len
);
}
self.write_varint(string.len() as i32);
self.write_bytes(string.as_bytes())
}
fn write_utf(&mut self, string: &str) -> Result<(), std::io::Error> {
self.write_utf_with_len(string, MAX_STRING_LENGTH.into())
}
fn write_short(&mut self, n: u16) -> Result<(), std::io::Error> {
WriteBytesExt::write_u16::<BigEndian>(self, n)
}
fn write_byte_array(&mut self, bytes: &[u8]) -> Result<(), std::io::Error> {
self.write_varint(bytes.len() as i32);
self.write_bytes(bytes)
}
}
#[async_trait]
pub trait Readable {
async fn read_varint(&mut self) -> Result<(i32, u8), String>;
async fn read_byte_array(&mut self) -> Result<Vec<u8>, String>;
async fn read_bytes(&mut self, n: usize) -> Result<Vec<u8>, String>;
async fn read_utf(&mut self) -> Result<String, String>;
async fn read_utf_with_len(&mut self, max_length: u32) -> Result<String, String>;
async fn read_byte(&mut self) -> Result<u8, String>;
}
// unfortunately we can't put this in Readable since rust gets mad
pub async fn read_collection<R, T, F, Fut>(buf: &mut R, reader: F) -> Result<Vec<T>, String>
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
T: Send,
F: FnOnce(&mut R) -> Fut + Send + Copy,
Fut: Future<Output = Result<T, String>> + Send,
{
let mut v: Vec<T> = Vec::new();
let length = buf.read_varint().await?.0;
for _ in 0..length {
v.push(reader(buf).await?);
}
Ok(v)
}
#[async_trait]
impl<R> Readable for R
where
R: AsyncRead + std::marker::Unpin + std::marker::Send,
{
// fast varints stolen from https://github.com/luojia65/mc-varint/blob/master/src/lib.rs#L67
/// Read a single varint from the reader and return the value, along with the number of bytes read
async fn read_varint(&mut self) -> Result<(i32, u8), String> {
let mut buffer = [0];
let mut ans = 0;
for i in 0..4 {
self.read_exact(&mut buffer)
.await
.map_err(|_| "Invalid VarInt".to_string())?;
ans |= ((buffer[0] & 0b0111_1111) as i32) << (7 * i);
if buffer[0] & 0b1000_0000 == 0 {
return Ok((ans, i + 1));
}
}
Ok((ans, 5))
}
async fn read_byte_array(&mut self) -> Result<Vec<u8>, String> {
let length = self.read_varint().await?.0 as usize;
Ok(self.read_bytes(length).await?)
}
async fn read_bytes(&mut self, n: usize) -> Result<Vec<u8>, String> {
let mut bytes = vec![0; n];
match AsyncReadExt::read_exact(self, &mut bytes).await {
Ok(_) => Ok(bytes),
Err(_) => Err("Error reading bytes".to_string()),
}
}
async fn read_utf(&mut self) -> Result<String, String> {
self.read_utf_with_len(MAX_STRING_LENGTH.into()).await
}
async fn read_utf_with_len(&mut self, max_length: u32) -> Result<String, String> {
let (length, _length_varint_length) = self.read_varint().await?;
// i don't know why it's multiplied by 4 but it's like that in mojang's code so
if length < 0 {
return Err(
"The received encoded string buffer length is less than zero! Weird string!"
.to_string(),
);
}
if length as u32 > max_length * 4 {
return Err(format!(
"The received encoded string buffer length is longer than maximum allowed ({} > {})",
length,
max_length * 4
));
}
// this is probably quite inefficient, idk how to do it better
let mut string = String::new();
let mut buffer = vec![0; length as usize];
self.read_exact(&mut buffer)
.await
.map_err(|_| "Invalid UTF-8".to_string())?;
string.push_str(std::str::from_utf8(&buffer).unwrap());
if string.len() > length as usize {
return Err(format!(
"The received string length is longer than maximum allowed ({} > {})",
length, max_length
));
}
Ok(string)
}
/// Read a single byte from the reader
async fn read_byte(&mut self) -> Result<u8, String> {
match AsyncReadExt::read_u8(self).await {
Ok(r) => Ok(r),
Err(_) => Err("Error reading byte".to_string()),
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::io::Cursor;
use tokio::io::BufReader;
#[test]
fn test_write_varint() {
let mut buf = Vec::new();
buf.write_varint(123456).unwrap();
assert_eq!(buf, vec![192, 196, 7]);
let mut buf = Vec::new();
buf.write_varint(0).unwrap();
assert_eq!(buf, vec![0]);
}
#[tokio::test]
async fn test_read_varint() {
let mut buf = BufReader::new(Cursor::new(vec![192, 196, 7]));
assert_eq!(buf.read_varint().await.unwrap(), (123456, 3));
let mut buf = BufReader::new(Cursor::new(vec![0]));
assert_eq!(buf.read_varint().await.unwrap(), (0, 1));
let mut buf = BufReader::new(Cursor::new(vec![1]));
assert_eq!(buf.read_varint().await.unwrap(), (1, 1));
}
#[tokio::test]
async fn test_read_varint_longer() {
let mut buf = BufReader::new(Cursor::new(vec![138, 56, 0, 135, 56, 123]));
assert_eq!(buf.read_varint().await.unwrap(), (7178, 2));
}
async fn readutf(r: &mut BufReader<Cursor<Vec<u8>>>) -> Result<String, String> {
r.read_utf().await
}
#[tokio::test]
async fn test_collection() {
let mut buf = Vec::new();
buf.write_collection(vec!["a", "bc", "def"], Vec::write_utf)
.unwrap();
let mut buf = BufReader::new(Cursor::new(buf));
let result = read_collection(&mut buf, readutf).await.unwrap();
assert_eq!(result, vec!["a", "bc", "def"]);
}
}
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