Function forest_filecoin::db::car::plain::read_block_data_location_and_skip

fn read_block_data_location_and_skip(
    reader: impl Read + Seek,
) -> Result<Option<(Cid, UncompressedBlockDataLocation)>>

Returns (Cid, the block data offset and block data length)

start ►│              reader end ►│
       ├───────────┬───┬──────────┤
       │body length│cid│block data│
       └───────────┴───┼──────────┤
                       │◄────────►│
                       │  =block data length
           block data  │
               offset ►│

Importantly, we seek block data length, rather than read any in. This allows us to keep indexing fast.

[Ok(None)] on EOF