Pumpkin-MC/Pumpkin · error

expected u8

Error message

expected u8

What it means

Thrown by `PacketReadSlice for u8` when the buffer is empty so no byte remains to read. It is an UnexpectedEof error indicating the slice buffer ran out before this field. Usually points to a truncated packet or a layout mismatch.

Solutions

1. Verify the buffer length before decoding (buf.len() >= expected fields)
2. Confirm the packet's total length from the header matches the payload
3. Check field order against the protocol spec
4. Reject the truncated packet gracefully

Example fix

// before
let id = u8::read_slice(&mut buf)?;
// after
if buf.is_empty() { return Err(PacketError::Truncated); }
let id = u8::read_slice(&mut buf)?;

if buf.is_empty() { return Err(PacketError::Truncated); }

let id = u8::read_slice(&mut buf)
    .map_err(|_| PacketError::Truncated)?;

When it happens

Trigger: u8::read_slice called on a zero-length buffer; the remaining packet payload is shorter than the fields being decoded.

Common situations: Truncated network packet; wrong field order relative to the protocol; reusing a buffer that was fully consumed by earlier fields.

Related errors

• expected bool byte
• expected i16
• expected i32
• durability correction must fit in an i16
• Failed to serialize packet

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/adaa9a4869c4753d. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin-protocol/src/serial/deserializer.rs:280

        Ok(Self::Owned(String::read(reader)?))
    }
}

impl<'a> PacketReadSlice<'a> for bool {
    fn read_slice(buf: &mut &'a [u8]) -> Result<Self, Error> {
        if buf.is_empty() {
            return Err(Error::new(ErrorKind::UnexpectedEof, "expected bool byte"));
        }
        let b = buf[0];
        *buf = &buf[1..];
        Ok(b != 0)
    }
}

impl<'a> PacketReadSlice<'a> for u8 {
    fn read_slice(buf: &mut &'a [u8]) -> Result<Self, Error> {
        if buf.is_empty() {
            return Err(Error::new(ErrorKind::UnexpectedEof, "expected u8"));
        }
        let b = buf[0];
        *buf = &buf[1..];
        Ok(b)
    }
}

impl<'a> PacketReadSlice<'a> for i8 {
    fn read_slice(buf: &mut &'a [u8]) -> Result<Self, Error> {
        u8::read_slice(buf).map(|b| b as Self)
    }
}

impl<'a> PacketReadSlice<'a> for i16 {
    fn read_slice(buf: &mut &'a [u8]) -> Result<Self, Error> {
        if buf.len() < 2 {
            return Err(Error::new(ErrorKind::UnexpectedEof, "expected i16"));
        }

View on GitHub (pinned to 8d4639e25a)