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2.2.6 Extensible BLOB

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Extensible binary large objects (BLOBs) are optional BLOBs that SHOULD be included in MSG_SEGLIST responses and can be included in MSG_GETSEGLIST requests.

Extensible BLOBs carry more information about the specific segments associated to the MSG_GETSEGLIST/MSG_SEGLIST exchange.

Extensible BLOBs are versioned, and for each version there is a well-known definition. Currently the only defined extensible BLOB version is extensible BLOB version 1. Future protocol versions can define new extensible BLOB versions.

The version of the extensible BLOB is encoded as a network-byte-order unsigned short integer in the first two bytes of the extensible BLOB itself.

Any extensible BLOB smaller than 2 bytes is invalid and MUST be discarded.

Implementations that do not support the specific extensible BLOB version encoded in the first two bytes of the BLOB itself MUST discard the BLOB.

Implementations that do support the specific extensible BLOB version encoded in the first two bytes of the BLOB itself MUST make sure that the size of the BLOB reported through SizeOfExtensibleBlob is compatible with the size restrictions for that specific BLOB version; if not, the BLOB MUST be discarded.