[−][src]Crate httlib_hpack
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.
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:
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:
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
Re-exports
pub use decoder::*; |
pub use encoder::*; |
Modules
decoder | Provides an implementation of the HPACK decoder. |
encoder | Provides an implementation of the HPACK encoder. |
table | Provides an implementation of the HPACK indexing tables. |