Enum DataLayoutMessage 

pub enum DataLayoutMessage {
    Contiguous {
        address: u64,
        size: u64,
    },
    Compact {
        data: Vec<u8>,
    },
    ChunkedV3 {
        chunk_dims: Vec<u64>,
        b_tree_address: u64,
    },
    ChunkedV4 {
        version: u8,
        flags: u8,
        chunk_dims: Vec<u64>,
        index_type: ChunkIndexType,
        earray_params: Option<EarrayParams>,
        farray_params: Option<FixedArrayParams>,
        bt2_params: Option<Bt2Params>,
        single_chunk_filter: Option<SingleChunkFilter>,
        index_address: u64,
    },
    Virtual {
        version: u8,
        heap_address: u64,
        heap_index: u32,
    },
}

Data layout message payload.

Variants

Contiguous

Contiguous storage — raw data in a single block.

Fields

address: u64

Address of raw data. UNDEF_ADDR if not yet allocated.

size: u64

Size of raw data in bytes.

Compact

Compact storage — raw data stored within the object header.

Fields

data: Vec<u8>

The raw data bytes.

ChunkedV3

Version 3 chunked storage, indexed by a version-1 B-tree.

This is what libhdf5 / h5py writes for a chunked dataset created with the default libver bounds.

Fields

chunk_dims: Vec<u64>

Chunk dimension sizes, including the trailing element-size dimension (so the chunk rank is chunk_dims.len() - 1).

b_tree_address: u64

Address of the version-1 B-tree that indexes the chunks.

ChunkedV4

Version 4 chunked storage. Version 5 shares this exact wire format — only the version byte differs — so both decode into this variant.

Fields

version: u8

Message version byte: 4 or 5. Version 5 (libhdf5 2.0, H5O_LAYOUT_VERSION_5) declares that the chunk index encodes filtered-chunk sizes in a fixed sizeof_size-byte field instead of the width derived from the chunk byte count, so a filter may expand a chunk without overflowing the field. Readers older than libhdf5 2.0 reject version 5.

flags: u8

chunk_dims: Vec<u64>

Chunk dimension sizes.

index_type: ChunkIndexType

Type of chunk index structure.

earray_params: Option<EarrayParams>

Extensible array parameters (present when index_type == ExtensibleArray).

farray_params: Option<FixedArrayParams>

Fixed array parameters (present when index_type == FixedArray).

bt2_params: Option<Bt2Params>

v2 B-tree parameters (present when index_type == BTreeV2).

single_chunk_filter: Option<SingleChunkFilter>

Filtered single-chunk parameters (present when index_type == SingleChunk and the layout’s filtered flag 0x02 is set).

index_address: u64

Address of the chunk index structure.

Virtual

Virtual dataset storage (H5D_VIRTUAL): the layout carries no data address of its own. heap_address/heap_index name the global heap object holding the mapping list — decode it with crate::format::messages::virtual_mapping::VirtualMappingList.

Fields

version: u8

Message version byte: 4 or 5 (virtual layout did not exist before version 4; version 5 is identical here).

heap_address: u64

Address of the global heap collection holding the mapping list.

heap_index: u32

1-based index of the mapping-list object within that collection. 0 means no mapping list has been written yet (a virtual dataset created but never given any mappings).

Implementations

impl DataLayoutMessage

pub fn check_against_dataset( &self, dataspace: &DataspaceMessage, datatype: &DatatypeMessage, ctx: &FormatContext, ) -> FormatResult<()>

The checks libhdf5 makes between a layout and the dataset’s sibling dataspace and datatype messages as the dataset opens, gathered in the one place the three decode side by side:

• A chunked layout’s stored dimensionality is the chunk rank plus one trailing element-size dimension, so it must be exactly one more than the dataspace rank (H5O__layout_decode, H5Olayout.c; HDFGroup/hdf5#6508, CVE-2026-19025). Left to chunk I/O, disagreeing ranks decode the index keys at the wrong rank and the chunk grid cannot be indexed.
• A compact layout’s stored bytes must be exactly the extent’s element count times the stored element size (H5D__compact_init, H5Dcompact.c:255-269). Left to I/O, a short payload is read past its end by any selection that reaches the missing elements.

Contiguous and virtual layouts have neither and always pass.

pub fn describe(&self) -> &'static str

The storage class and message version, for a message that has to name which layout it is talking about.

pub fn contiguous_unallocated(size: u64) -> Self

Contiguous layout with no data allocated yet.

pub fn contiguous(address: u64, size: u64) -> Self

Contiguous layout pointing to allocated data.

pub fn compact(data: Vec<u8>) -> Self

Compact layout with inline data.

pub fn chunked_v3_btree_v1(chunk_dims: Vec<u64>, b_tree_address: u64) -> Self

Version 3 chunked layout indexed by a version-1 B-tree.

chunk_dims must include the trailing element-size dimension.

pub fn chunked_v4_earray( version: u8, chunk_dims: Vec<u64>, earray_params: EarrayParams, index_address: u64, ) -> Self

Version 4 chunked layout with extensible array index.

chunk_dims should include the trailing element-size dimension. For example, for a 2D dataset with chunk=(1,4) and element_size=8, pass chunk_dims = [1, 4, 8].

pub fn chunked_v4_farray( version: u8, chunk_dims: Vec<u64>, farray_params: FixedArrayParams, index_address: u64, ) -> Self

Version 4 chunked layout with fixed array index.

chunk_dims should include the trailing element-size dimension.

pub fn chunked_v4_btree_v2( version: u8, chunk_dims: Vec<u64>, bt2_params: Bt2Params, index_address: u64, ) -> Self

Version 4 chunked layout with B-tree v2 index.

chunk_dims should include the trailing element-size dimension.

pub fn chunked_v4_implicit( version: u8, chunk_dims: Vec<u64>, index_address: u64, ) -> Self

Version 4 chunked layout with the implicit index — no index structure at all: index_address is the start of one contiguous run holding every chunk of the maximum-extent grid in row-major order, so a chunk’s address is arithmetic (H5D__none_idx_get_addr, H5Dnone.c).

chunk_dims should include the trailing element-size dimension.

pub fn virtual_layout(version: u8, heap_address: u64, heap_index: u32) -> Self

Virtual dataset layout pointing at a global-heap mapping list.

pub fn chunked_v4_single(chunk_dims: Vec<u64>, index_address: u64) -> Self

Version 4 chunked layout with single-chunk index.

chunk_dims should include the trailing element-size dimension.

pub fn chunked_v4_single_filtered( chunk_dims: Vec<u64>, index_address: u64, nbytes: u64, filter_mask: u32, ) -> Self

Version 4 chunked layout with a filtered single-chunk index: the “single index with filter” flag (0x02) is set and the chunk’s on-disk size and filter mask are carried inline (H5O_LAYOUT_CHUNK_SINGLE_INDEX_WITH_FILTER, H5Dsingle.c).

chunk_dims should include the trailing element-size dimension.

pub fn encode(&self, ctx: &FormatContext) -> Vec<u8>

pub fn decode(buf: &[u8], ctx: &FormatContext) -> FormatResult<(Self, usize)>

Trait Implementations

impl Clone for DataLayoutMessage

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DataLayoutMessage

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for DataLayoutMessage

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for DataLayoutMessage