Pumpkin-MC/Pumpkin · error · Error

Length too large

Error message

Length too large: {0}

What it means

This is Error::LargeLength from pumpkin-nbt's Error enum. It is thrown when a string, list, or array declared in the NBT payload exceeds the supported length, preventing huge allocations from hostile or corrupt data.

Solutions

1. Validate the length field against your expected payload size before deserializing
2. Verify you are using the correct NBT variant (Java vs Bedrock) for the data source
3. Truncate/reject the input and log the offending connection or file

Example fix

// before
let nbt = Nbt::from_reader(&mut cursor).unwrap();
// after
match Nbt::from_reader(&mut cursor) {
    Ok(nbt) => nbt,
    Err(Error::LargeLength(len)) => { log::warn!("NBT length too large: {}", len); return; }
    Err(e) => return Err(e.into()),
}

fn length_ok(len: i32, max: usize) -> bool { len >= 0 && (len as usize) <= max }

match result { Err(Error::LargeLength(n)) => reject_input(n), Err(e) => propagate(e), Ok(v) => use(v) }

When it happens

Trigger: Deserializing an NBT payload whose length prefix (string length, list len, or array size) exceeds the library's maximum supported size.

Common situations: Malformed packets from untrusted clients, corrupted world/level.dat data, or reading Bedrock NBT buffers with a mismatched byte-offset.

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

• Serde error
• Failed to decode varint - value too large
• Failed to decode varlong - value too large
• Invalid element tag type for list
• unexpected EOF

AI-assisted analysis of Pumpkin-MC/Pumpkin@8d4639e25a (2026-09-09). Data as JSON: /api/errors/a36e89e62c989314. Report an issue: GitHub.

Appendix: source

Thrown at crates/pumpkin-nbt/src/lib.rs:98

    #[error("Failed to Cesu 8 Decode")]
    Cesu8DecodingError,
    /// A string could not be decoded as UTF-8.
    #[error("Failed to UTF-8 Decode")]
    Utf8DecodingError,
    /// Serde reported an invalid value or serializer state.
    #[error("Serde error: {0}")]
    SerdeError(String),
    /// The requested Rust type has no NBT representation.
    #[error("NBT doesn't support this type: {0}")]
    UnsupportedType(String),
    /// The underlying reader or writer returned an I/O error.
    #[error("NBT reading was cut short: {0}")]
    Incomplete(io::Error),
    /// A list or array declared a negative element count.
    #[error("Negative list length: {0}")]
    NegativeLength(i32),
    /// A string, list, or array exceeded the supported length.
    #[error("Length too large: {0}")]
    LargeLength(usize),
    /// A Bedrock variable-length integer exceeded its maximum encoded size.
    #[error("Failed to decode varint - value too large")]
    VarIntTooLarge,
    /// A Bedrock variable-length long exceeded its maximum encoded size.
    #[error("Failed to decode varlong - value too large")]
    VarLongTooLarge,
    /// NBT nesting depth exceeded the maximum allowed limit.
    #[error("NBT depth exceeded maximum allowed limit")]
    MaxDepthExceeded,
    /// A list tag specified an invalid element tag type.
    #[error("Invalid element tag type for list: {0}")]
    InvalidListTag(u8),
}

/// A complete NBT document containing a named root compound.
#[derive(Clone, Debug, Default, PartialEq)]
pub struct Nbt {

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