Module metadata 

Per-object metadata types and HTTP header serialization.

This module defines Metadata, the per-object metadata structure that travels through the entire system: clients set it via HTTP headers, the server parses and validates it, the service passes it to backends, and backends persist it alongside the stored object.

The module also defines further types used in metadata.

Serialization

Metadata has two serialization formats:

• HTTP headers — used by the public API. Metadata::from_headers and Metadata::to_headers handle this conversion for public fields only.
• JSON — used internally by backends for storage. JSON serialization includes additional internal fields that are skipped in the header representation.

HTTP header prefixes

Headers use three prefix conventions:

• Standard HTTP headers where applicable (Content-Type, Content-Encoding)
• x-sn-* for objectstore-specific fields (e.g. x-sn-expiration)
• x-snme- for custom user metadata (e.g. x-snme-build_id)

Backends that store metadata as object metadata (like GCS) layer their own prefix on top, so x-sn-expiration becomes x-goog-meta-x-sn-expiration. The Metadata::from_headers and Metadata::to_headers methods accept a prefix parameter for this purpose.

Structs

Metadata

Per-object metadata.

Enums

Compression

The compression algorithm applied to an object’s payload.

Error

Errors that can happen dealing with metadata

ExpirationPolicy

The per-object expiration policy.

Constants

DEFAULT_CONTENT_TYPE

The default content type for objects without a known content type.

HEADER_EXPIRATION

The custom HTTP header that contains the serialized ExpirationPolicy.

HEADER_FILENAME

The custom HTTP header that contains the filename of the object.

HEADER_META_PREFIX

The prefix for custom HTTP headers containing custom per-object metadata.

HEADER_ORIGIN

The custom HTTP header that contains the origin of the object.

HEADER_TIME_CREATED

The custom HTTP header that contains the object creation time.

HEADER_TIME_EXPIRES

The custom HTTP header that contains the object expiration time.