Module shared_message 

HDF5 Shared Object Header Message resolution.

When a header message has its “shared” flag (bit 1 of msg_flags) set, the message data is not the actual message content but a reference to a shared copy stored elsewhere.

Shared message reference types:

• Type 0: shared in the same object header (not typically used)
• Type 1: shared in another object header (version 1-2)
• Type 2: shared in the SOHM table (via fractal heap, version 3)
• Type 3: shared in another object header (version 3)

SOHM table structures:

• SharedMessageTable message (0x000F) in superblock extension: version + table_addr + nindexes
• SMTB structure at table_addr: per-index metadata (type flags, addresses, etc.)
• SMLI list structure: simple list of shared message entries
• B-tree v2 type 7: indexed shared message entries

Structs

SharedMessageRef

A resolved shared message reference.

SohmEntry

A single entry in a SOHM list or B-tree.

SohmIndex

A single SOHM index entry from the SMTB table.

SohmTable

Parsed SOHM table (SMTB structure).

SohmTableMessage

Parsed Shared Message Table message (type 0x000F from superblock extension).

Functions

is_shared

Check whether a header message has its shared flag set.

parse_shared_ref

Parse a shared message reference from the message data.

parse_sohm_btree_entries

Parse SOHM entries from a B-tree v2 type 7 index.

parse_sohm_list

Parse a SOHM list (signature “SMLI”) and return all entries.

parse_sohm_table

Parse the SOHM table structure (signature “SMTB”) from the file.

parse_sohm_table_message

Parse a Shared Message Table message (type 0x000F) from the superblock extension.

resolve_shared_message

Resolve a shared message to its actual message data.

resolve_shared_message_with_sohm

Resolve a shared message, optionally using a SOHM table for type 2 refs.

resolve_sohm_message

Resolve a type 2 (SOHM) shared message reference.