zarr::shard Namespace Reference

Classes
struct	Extent
struct	Placement

Functions
Placement	place (const ArrayMeta &meta, const std::string &path, const std::vector< std::uint64_t > &inner_index, std::size_t level=0)
Extent	extent (const ArrayMeta &meta, const Bytes &index_bytes, std::uint64_t slot, std::size_t level=0)
Bytes	pack (const ArrayMeta &meta, const std::vector< std::optional< Bytes > > &entries, std::size_t level=0)

Detailed Description

Pure shard-index resolution for consumers that own their own I/O (e.g. a browser fetching HTTP ranges). No Store, no fetch loop: the caller drives a two-phase handshake — resolve the shard and where its index sits, fetch that index, then resolve the chunk's extent — so the drift-prone index math stays in libzarr while the fetches stay in the consumer. A complete pure-sync read is place() -> fetch index bytes -> extent() -> fetch chunk bytes -> CodecPipeline::resolve(meta).decode(bytes).

Function Documentation

extent()

Extent zarr::shard::extent ( const ArrayMeta &  meta, const Bytes &  index_bytes, std::uint64_t  slot, std::size_t  level = 0  )

inline

Decodes index_bytes (the Placement::index_size bytes the caller fetched at the index location) and returns slot slot's extent. level must match the place() call. Pure: no I/O. Throws on a malformed or wrong-size index.

pack()

Bytes zarr::shard::pack ( const ArrayMeta &  meta, const std::vector< std::optional< Bytes > > &  entries, std::size_t  level = 0  )

inline

Assembles the shard object for shard level (0 = outermost) from its slot-ordered inner chunks. entries[i] is the ENCODED bytes of the chunk at C-order slot i, or std::nullopt for a fill slot (whose index entry becomes the sentinel). Returns the shard bytes — concatenated chunk bodies plus the checksummed [offset, nbytes] index, laid out per the level's index_location — or an empty buffer if every slot is absent (an all-fill shard is not written; the caller simply skips or erases that key). Pure: no I/O. The inverse of extent(): pack() then extent() round-trips each slot's extent. Throws if level is not a shard level or entries.size() != the shard's slot count.

place()

Placement zarr::shard::place ( const ArrayMeta &  meta, const std::string &  path, const std::vector< std::uint64_t > &  inner_index, std::size_t  level = 0  )

inline

Resolves which shard holds inner chunk inner_index (an inner-chunk grid coordinate) for the array at path ("" = store root). level selects the shard level (0 = outermost) for nested sharding. Pure: reads only meta. Throws if level is not a shard level or inner_index is out of range.