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//! This crate implements [canonical Huffman] functionality for handling [HPACK] //! format in [HTTP/2]. It exposes a simple API for performing the encoding and //! decoding of [HTTP/2] header string literals according to the [HPACK] spec. //! //! [](https://docs.rs/httlib-huffman) //! [](https://github.com/xpepermint/httlib-rs/tree/main/huffman) //! //! Header Compression format for [HTTP/2], known as [HPACK], foresees the use //! of the Huffman algorithm for encoding header literal values. This //! contributes to the additional decrease in the quantity of data, transferred //! with each web request and response. //! //! A [Huffman code] is a particular type of optimal prefix code that is //! commonly used for lossless data compression. The process of finding or using //! such a code proceeds by means of Huffman coding, an algorithm developed by //! David A. Huffman. The output from Huffman's algorithm can be viewed as a //! variable-length code table for encoding a source symbol (such as a character //! in a file). The algorithm derives this table from the estimated probability //! or frequency of occurrence (weight) for each possible value of the source //! symbol. As in other entropy encoding methods, more common symbols are //! generally represented using fewer bits than less common symbols. Huffman's //! method can be efficiently implemented, finding a code in time linear to the //! number of input weights if these weights are sorted. //! //! [HPACK] compression entails a pre-created [canonical Huffman] code table //! for encoding [ASCII] characters to the Huffman sequence. A //! [canonical Huffman] code is a particular type of [Huffman code] with unique //! properties that allow it to be described in a very compact manner. In the //! aforementioned table are the Huffman codes for each [ASCII] character with a //! length up to 32 bits (4x by 8 fields with value 0 or 1), in the form of //! base-2 integer, aligned on the most significant bit (MSB is the bit farthest //! to the left). //! //! Each module covers this topic in more details so check the rest of the code //! to learn more. //! //! ## Usage //! //! Encoding: //! //! ```rs //! use httlib_huffman::encode; //! //! let mut dst = Vec::new(); //! let text = "Hello world!".as_bytes(); //! encode(&text, &mut dst)?; //! ``` //! //! Decoding: //! //! ```rs //! use httlib_huffman::decode; //! //! let speed = 3; //! let mut dst = Vec::new(); //! let src = vec![168, 209, ...]; //! decode(&src, &mut dst, speed)?; //! ``` //! //! ## Articles //! //! * [HPACK: Huffman encoder](https://kristijansedlak.medium.com/hpack-huffman-encoder-explained-61102edd6ecc) //! * [HPACK: Huffman translation matrix](https://kristijansedlak.medium.com/hpack-huffman-translation-matrix-f3cae44bfe8c) //! * [HPACK: Huffman decoder](https://medium.com/@kristijansedlak/hpack-huffman-decoder-72d215788130) //! //! [ASCII]: https://en.wikipedia.org/wiki/ASCII //! [HPACK]: https://tools.ietf.org/html/rfc7541 //! [HTTP/2]: https://tools.ietf.org/html/rfc7540 //! [Huffman code]: https://en.wikipedia.org/wiki/Huffman_coding //! [canonical Huffman]: https://en.wikipedia.org/wiki/Canonical_Huffman_code pub mod decode; pub mod encode; pub mod flatten; pub mod parse; pub use decode::*; pub use encode::*; pub use flatten::*; pub use parse::*;