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//! Utilities for reading and writing for the Minecraft protocol
use std::io::{Cursor, Write};
use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
use tokio::io::{AsyncRead, AsyncReadExt, BufReader};
// const MAX_VARINT_SIZE: u32 = 5;
// const MAX_VARLONG_SIZE: u32 = 10;
// const DEFAULT_NBT_QUOTA: u32 = 2097152;
const MAX_STRING_LENGTH: u16 = 32767;
// const MAX_COMPONENT_STRING_LENGTH: u32 = 262144;
pub async fn read_byte<T: AsyncRead + std::marker::Unpin>(
buf: &mut BufReader<T>,
) -> Result<u8, String> {
match AsyncReadExt::read_u8(buf).await {
Ok(r) => Ok(r),
Err(_) => Err("Error reading byte".to_string()),
}
}
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);
}
// fast varints stolen from https://github.com/luojia65/mc-varint/blob/master/src/lib.rs#L67
pub async fn read_varint<T: AsyncRead + std::marker::Unpin>(
buf: &mut BufReader<T>,
) -> Result<u32, String> {
let mut buffer = [0];
let mut ans = 0;
for i in 0..4 {
buf.read_exact(&mut buffer)
.await
.or_else(|_| Err("Invalid VarInt".to_string()))?;
ans |= ((buffer[0] & 0b0111_1111) as u32) << 7 * i;
if buffer[0] & 0b1000_0000 == 0 {
break;
}
}
Ok(ans)
}
pub fn write_varint(buf: &mut Vec<u8>, mut value: u32) {
let mut buffer = [0];
while value != 0 {
buffer[0] = (value & 0b0111_1111) as u8;
value = (value >> 7) & (u32::max_value() >> 6);
if value != 0 {
buffer[0] |= 0b1000_0000;
}
buf.write(&buffer).unwrap();
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_write_varint() {
let mut buf = Vec::new();
write_varint(&mut buf, 123456);
assert_eq!(buf, vec![192, 196, 7]);
}
#[tokio::test]
async fn test_read_varint() {
let mut buf = BufReader::new(Cursor::new(vec![192, 196, 7]));
assert_eq!(read_varint(&mut buf).await.unwrap(), 123456);
}
#[tokio::test]
async fn test_read_varint_longer() {
let mut buf = BufReader::new(Cursor::new(vec![138, 56, 0, 135, 56, 123]));
assert_eq!(read_varint(&mut buf).await.unwrap(), 7178);
}
}
pub fn write_utf_with_len(buf: &mut Vec<u8>, string: &String, len: usize) {
if string.len() > len {
panic!(
"String too big (was {} bytes encoded, max {})",
string.len(),
len
);
}
write_varint(buf, string.len() as u32);
write_bytes(buf, string.as_bytes());
}
pub fn write_utf(buf: &mut Vec<u8>, string: &String) {
write_utf_with_len(buf, string, MAX_STRING_LENGTH as usize);
}
pub fn write_short(buf: &mut Vec<u8>, n: u16) {
WriteBytesExt::write_u16::<BigEndian>(buf, n).unwrap();
}
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