Module metadata 

Per-object metadata types and HTTP header serialization.

This module defines Metadata, the per-object metadata structure that accompanies every stored object, along with ExpirationPolicy and Compression.

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. Internal fields like Metadata::is_redirect_tombstone are handled by backends directly.
• JSON — used internally by backends for storage. JSON serialization includes additional internal fields (e.g. is_redirect_tombstone) 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_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_REDIRECT_TOMBSTONE

The custom HTTP header that contains the serialized redirect tombstone.

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.