mime

mime is a small Rust crate that models MIME (HTTP Media Type) values as strong types rather than raw strings, catching malformed content-type values at compile time or parse time instead of deep in a request handler. It is a foundational dependency across the Rust HTTP ecosystem, used by libraries like hyper and actix-web to represent Content-Type and Accept headers without repeated ad-hoc string splitting.

The crate exposes constants for common types (mime::TEXT_PLAIN, mime::APPLICATION_JSON) plus a parser for arbitrary media type strings, letting consumers pattern-match on type/subtype pairs and query parameters (like charset) safely.

What You Get

• A Mime struct with strongly typed top-level type and subtype accessors
• Predefined constants for common media types (TEXT_PLAIN, APPLICATION_JSON, IMAGE_PNG, and more)
• A conformant parser for arbitrary MIME strings per RFC 7231
• Support for MIME parameters such as charset via get_param
• Optional serde support for serializing/deserializing Mime values

Common Use Cases

• Parsing and validating a Content-Type header in an HTTP server or client
• Building Accept headers or content negotiation logic that matches on type/subtype
• Storing and comparing file/attachment media types without manual string handling
• Underpinning higher-level HTTP crates (hyper, actix-web) that need a canonical MIME representation

Under The Hood

Architecture - The crate splits parsing logic into a mime-parse sub-crate consumed by the top-level mime crate, which layers ergonomic constants and accessor methods (type_(), subtype(), get_param()) over the parsed representation, keeping the public surface small (src/lib.rs, src/type_.rs, src/value.rs) while isolating RFC 7231 grammar handling. Tech Stack - Pure Rust with zero required runtime dependencies beyond quoted-string for parameter parsing; an optional serde1 feature adds serde Serialize/Deserialize support and an optional macro feature (via mime-macro and proc-macro-hack) enables compile-time-checked MIME literals; Cargo workspace groups the root crate with mime-macro and mime-parse. Code Quality - Unit tests live alongside implementation in constants.rs, value.rs, type_.rs, macros.rs, and range.rs, exercising parsing edge cases and equality/ordering behavior; the codebase is small (~1,200 lines across core files) and has been stable for years with infrequent but low-risk maintenance commits. API Design - The API favors compile-time constants (mime::TEXT_PLAIN) for the common path and a parse() fallback for arbitrary strings, minimizing boilerplate for typical HTTP header handling; documentation lives on docs.rs with a concise README usage example.