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//! This crate implements [HPACK], a compression format for efficiently //! representing HTTP header fields in [HTTP/2]. It exposes a simple API for //! performing the encoding and decoding of HTTP headers. //! //! [](https://docs.rs/httlib-hpack) //! [](https://github.com/xpepermint/httlib-rs/tree/main/hpack) //! //! ## About //! //! [HPACK] is a compression format that eliminates redundant header fields in //! requests and responses. This is one of the features based on which the //! [HTTP/2] protocol significantly reduces the amount of transferred data from //! one entity to another. //! //! A significant shift in thinking is required from the implementer of the //! [HTTP/2] protocol. A connection in [HTTP/2] does not represent a single //! request/response session. We can start multiple simultaneous streams in one //! connection, representing multiple request/response sessions, which was not //! possible in the previous versions of the HTTP protocol. The [HPACK] //! compressor uses this characteristic of [HTTP/2] by indexing headers //! considering the whole connection and not per stream. //! //! The implementation of [HPACK] contains three main parts of the process: //! //! * `Indexing table` is a list, to which the HPACK saves the commonly used //! headers. Each entity indexes headers per connection, separately for incoming //! (decoding) and for outgoing (encoding) data. //! //! * `Encoder` performs the task of data compression. It converts the data from //! its original readable form into an optimized byte sequence by applying the //! rules defined in the HPACK specification. //! //! * `Decoder` takes over the task of the decompressor. It executes the //! commands inversely to the encoder. It converts the data back into its //! readable form. //! //! ## Usage //! //! **Encoding example:** //! //! ```rust //! use httlib_hpack::Encoder; //! //! let mut encoder = Encoder::default(); //! //! let name = b":method".to_vec(); //! let value = b"PATCH".to_vec(); //! let flags = Encoder::HUFFMAN_VALUE | Encoder::WITH_INDEXING | Encoder::BEST_FORMAT; //! //! let mut dst = Vec::new(); //! encoder.encode((name, value, flags), &mut dst).unwrap(); //! ``` //! //! **Decoding example:** //! //! ```rust //! use httlib_hpack::Decoder; //! //! let mut decoder = Decoder::default(); //! let mut buf = vec![0x80 | 2]; //! //! let mut dst = Vec::new(); //! decoder.decode(&mut buf, &mut dst).unwrap(); //! //! for (name, value, flags) in dst { //! if flags & Decoder::NEVER_INDEXED == Decoder::NEVER_INDEXED { //! // sensitive header //! } else { //! // common header //! } //! } //! ``` //! //! ## Articles //! //! * [HPACK: The secret ingredient of HTTP/2](https://dev.to/xpepermint/hpack-the-secret-ingredient-of-http-2-4np6) //! //! [HPACK]: https://tools.ietf.org/html/rfc7541 //! [HTTP/2]: https://tools.ietf.org/html/rfc7540 pub mod decoder; pub mod encoder; pub mod table; pub use decoder::*; pub use encoder::*; use table::*;