Method read_tile

nodedb-array/src/segment/reader.rs:250–291

Decode tile #`idx`. CRC is checked by the framing layer.

(&self, idx: usize)

    /// Decode tile #`idx`. CRC is checked by the framing layer.
    pub fn read_tile(&self, idx: usize) -> ArrayResult<TilePayload> {
        let entry = self
            .footer
            .tiles
            .get(idx)
            .ok_or_else(|| ArrayError::SegmentCorruption {
                detail: format!(
                    "tile index {idx} out of range (have {})",
                    self.footer.tiles.len()
                ),
            })?;
        let off = entry.offset as usize;
        let len = entry.length as usize;
        let end = off
            .checked_add(len)
            .ok_or_else(|| ArrayError::SegmentCorruption {
                detail: "tile entry offset+length overflows".into(),
            })?;
        if end > self.bytes.len() {
            return Err(ArrayError::SegmentCorruption {
                detail: format!(
                    "tile {idx} block out of bounds: off={off} len={len} \
                     file_size={}",
                    self.bytes.len()
                ),
            });
        }
        let (payload, _) = BlockFraming::decode(&self.bytes[off..end])?;
        match entry.kind {
            TileKind::Sparse => {
                let t = read_sparse_tile(payload)?;
                Ok(TilePayload::Sparse(t))
            }
            TileKind::Dense => {
                let t: DenseTile =
                    zerompk::from_msgpack(payload).map_err(|e| ArrayError::SegmentCorruption {
                        detail: format!("dense tile decode failed: {e}"),
                    })?;
                Ok(TilePayload::Dense(t))
            }
        }
    }
}

/// An owned segment reader that holds decrypted segment bytes.