GitoxideLabs/gitoxide · error

in-bound distance of deltas

Error message

in-bound distance of deltas

What it means

`Entry::base_pack_offset(distance)` computes the delta base's pack offset by subtracting `distance` from the entry offset. The method is documented to panic if the distance causes an underflow or is invalid; the error means the caller supplied a delta base distance that reaches before the start of the pack, indicating corrupt delta data.

Solutions

1. Validate `distance <= entry.pack_offset()` before calling, or use `checked_base_pack_offset(distance)` which returns Option
2. Re-verify / re-download the pack if corruption is suspected (`git fsck`)
3. Switch to `checked_base_pack_offset` and handle None explicitly

Example fix

// before
let base = entry.base_pack_offset(distance); // panics on bad distance
// after
let base = entry.checked_base_pack_offset(distance)
    .ok_or_else(|| anyhow::anyhow!("invalid delta base distance {distance}"))?;

if distance > entry.pack_offset() { return Err(anyhow!("delta base distance {} exceeds entry offset", distance)); }

// prefer the checked API over the panicking one
let base = entry.checked_base_pack_offset(distance)
    .ok_or_else(|| anyhow!("invalid delta base distance"))?;

When it happens

Trigger: Calling `base_pack_offset(distance)` on an OFS_DELTA/REF_DELTA entry with a distance larger than the entry's own pack offset, e.g. from a corrupted pack or a wrongly parsed header.

Common situations: Traversing corrupted packs, manually constructed delta entries, or code that mis-computes base distances when reimplementing pack parsing.

Related errors

• BUG: pack now is smaller than all previously seen entries
• if you see this the object database is correct as a delta…
• Cannot use iter_v1() on index of type
• Cannot use iter_v2() on index of type
• must have been resolved

AI-assisted analysis of GitoxideLabs/gitoxide@e73179060b (2026-09-08). Data as JSON: /api/errors/5d825afee486afb4. Report an issue: GitHub.

Appendix: source

Thrown at gix-pack/src/data/entry/mod.rs:46

    }
}

/// Access
impl Entry {
    /// Compute the pack offset to the base entry of the object represented by this entry, or
    /// return `None` if the distance would underflow or is invalid.
    pub fn checked_base_pack_offset(&self, distance: u64) -> Option<data::Offset> {
        Header::verified_base_pack_offset(self.pack_offset(), distance)
    }

    /// Compute the pack offset to the base entry of the object represented by this entry.
    ///
    /// # Panics
    ///
    /// Panics if the `distance` will cause an underflow or is invalid.
    pub fn base_pack_offset(&self, distance: u64) -> data::Offset {
        self.checked_base_pack_offset(distance)
            .expect("in-bound distance of deltas")
    }
    /// The pack offset at which this entry starts
    pub fn pack_offset(&self) -> data::Offset {
        self.data_offset - self.header_size() as u64
    }
    /// The amount of bytes used to describe this entry in the pack.
    ///
    /// For entries decoded from pack data this returns the actual encoded header length, including
    /// non-canonical overlong size encodings accepted by Git. This is the length to use for offset
    /// reconstruction because the header starts at [`Self::pack_offset()`] and the compressed data
    /// starts at [`Entry::data_offset`].
    ///
    /// If [`Entry::encoded_header_size`] is `0`, the actual encoded length is unknown and this falls
    /// back to [`Header::size()`], which computes the canonical serialized length from the decoded
    /// header and decompressed size.
    pub fn header_size(&self) -> usize {
        if self.encoded_header_size == 0 {
            self.header.size(self.decompressed_size)

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