Pumpkin-MC/Pumpkin · error · std::io::Error

durability correction must fit in an i16

Error message

durability correction must fit in an i16

What it means

Raised by ItemStackResponseSlotInfo::write when durability_correction (a VarInt) falls outside the signed 16-bit range (-32768..=32767). The Bedrock protocol encodes this field as an i16, so larger values would corrupt the packet. The write fails fast with InvalidInput instead of emitting a malformed packet.

Solutions

1. Clamp durability_correction to -32768..=32767 before building the packet.
2. Check the computation that produces the value for i32/i64 leakage into an i16 field.
3. Return or log a domain error instead of silently wrapping when the value doesn't fit.

Example fix

// before
let correction = VarInt(damage_delta as i32);
// after
let correction = VarInt(damage_delta.clamp(-32768, 32767) as i32);

fn valid_correction(v: i32) -> bool { (-32768..=32767).contains(&v) }
// assert before building the packet:
debug_assert!(valid_correction(durability_correction.0));

fn fits_i16(v: i64) -> Option<i16> { i16::try_from(v).ok() }

packet.write(&mut writer).map_err(|e| {
    log::error!("item stack response encode failed: {e}");
    e
})?;

When it happens

Trigger: Constructing an ItemStackResponseSlotInfo with durability_correction.0 outside -32768..=32767 and serializing the packet with PacketWrite::write.

Common situations: Computing durability correction from an i32/u32 item damage value without clamping; arithmetic overflow when aggregating durability deltas.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

• item stack response count exceeds 4096
• item string too long
• user_data_len exceeds 1MB limit
• extra_data_len exceeds 1MB limit
• Invalid ContainerName ID

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/06a47549a3bb5f26. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin-protocol/src/bedrock/client/item_stack_response.rs:24

    serial::PacketWrite,
};
use pumpkin_macros::packet;

#[derive(Debug, Clone)]
pub struct ItemStackResponseSlotInfo {
    pub requested_slot: u8,
    pub slot: u8,
    pub amount: u8,
    pub item_stack_net_id: VarInt,
    pub custom_name: String,
    pub filtered_custom_name: String,
    pub durability_correction: VarInt,
}

impl PacketWrite for ItemStackResponseSlotInfo {
    fn write<W: Write>(&self, writer: &mut W) -> Result<(), Error> {
        if !(-32768..=32767).contains(&self.durability_correction.0) {
            return Err(Error::new(
                std::io::ErrorKind::InvalidInput,
                "durability correction must fit in an i16",
            ));
        }
        self.requested_slot.write(writer)?;
        self.slot.write(writer)?;
        self.amount.write(writer)?;
        true.write(writer)?;
        (self.item_stack_net_id.0 > 0).write(writer)?;
        if self.item_stack_net_id.0 > 0 {
            self.item_stack_net_id.write(writer)?;
        }
        self.custom_name.write(writer)?;
        self.filtered_custom_name.write(writer)?;
        self.durability_correction.write(writer)
    }
}

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