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//! Utilities for reading and writing for the Minecraft protocol
use std::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;
pub fn write_byte(buf: &mut Vec<u8>, n: u8) {
WriteBytesExt::write_u8(buf, n).unwrap();
}
pub fn write_bytes(buf: &mut Vec<u8>, bytes: &[u8]) {
buf.extend_from_slice(bytes);
}
pub fn write_varint(buf: &mut Vec<u8>, mut value: i32) {
let mut buffer = [0];
if value == 0 {
buf.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;
}
buf.write_all(&buffer).unwrap();
}
}
pub fn write_utf_with_len(buf: &mut Vec<u8>, string: &str, len: usize) {
if string.len() > len {
panic!(
"String too big (was {} bytes encoded, max {})",
string.len(),
len
);
}
write_varint(buf, string.len() as i32);
write_bytes(buf, string.as_bytes());
}
pub fn write_utf(buf: &mut Vec<u8>, string: &str) {
write_utf_with_len(buf, string, MAX_STRING_LENGTH.into());
}
pub fn write_short(buf: &mut Vec<u8>, n: u16) {
WriteBytesExt::write_u16::<BigEndian>(buf, n).unwrap();
}
pub fn write_byte_array(buf: &mut Vec<u8>, bytes: &[u8]) {
write_varint(buf, bytes.len() as i32);
write_bytes(buf, 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>;
}
#[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();
write_varint(&mut buf, 123456);
assert_eq!(buf, vec![192, 196, 7]);
let mut buf = Vec::new();
write_varint(&mut buf, 0);
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));
}
}
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