Crate weezl

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Expand description

§LZW decoder and encoder

This crates provides an Encoder and a Decoder in their respective modules. The code words are written from and to bit byte slices (or streams) where it is possible to write either the most or least significant bits first. The maximum possible code size is 12 bits, the smallest available code size is 2 bits.

§Example

These two code blocks show the compression and corresponding decompression. Note that you must use the same arguments to Encoder and Decoder, otherwise the decoding might fail or produce bad results.

use weezl::{BitOrder, encode::Encoder};

let data = b"Hello, world";
let compressed = Encoder::new(BitOrder::Msb, 9)
    .encode(data)
    .unwrap();
use weezl::{BitOrder, decode::Decoder};

let decompressed = Decoder::new(BitOrder::Msb, 9)
    .decode(&compressed)
    .unwrap();
assert_eq!(decompressed, data);

§LZW Details

The de- and encoder expect the LZW stream to start with a clear code and end with an end code which are defined as follows:

  • CLEAR_CODE == 1 << min_code_size
  • END_CODE == CLEAR_CODE + 1

For optimal performance, all buffers and input and output slices should be as large as possible and at least 2048 bytes long. This extends to input streams which should have similarly sized buffers. This library uses Rust’s standard allocation interfaces (Box and Vec to be precise). Since there are no ways to handle allocation errors it is not recommended to operate it on 16-bit targets.

§Allocations and standard library

The main algorithm can be used in no_std as well, although it requires an allocator. This restriction might be lifted at a later stage. For this you should deactivate the std feature. The main interfaces stay intact but the into_stream combinator is no available.

Modules§

  • decode
    A module for all decoding needs.
  • encode
    A module for all encoding needs.
  • error 🔒

Structs§

  • BufferResult
    The result of a coding operation on a pair of buffer.
  • StreamResult
    The result of coding into an output stream.

Enums§

  • BitOrder
    The order of bits in bytes.
  • LzwError
    The error kind after unsuccessful coding of an LZW stream.
  • LzwStatus
    The status after successful coding of an LZW stream.
  • StreamBuf 🔒
    An owned or borrowed buffer for stream operations.

Constants§

Functions§

Type Aliases§

  • Code 🔒
    Alias for a LZW code point