ruzstd/encoding/
mod.rs

1//! Structures and utilities used for compressing/encoding data into the Zstd format.
2
3pub(crate) mod block_header;
4pub(crate) mod blocks;
5pub(crate) mod frame_header;
6pub(crate) mod match_generator;
7pub(crate) mod util;
8
9mod frame_compressor;
10mod levels;
11pub use frame_compressor::FrameCompressor;
12
13use crate::io::{Read, Write};
14use alloc::vec::Vec;
15
16/// Convenience function to compress some source into a target without reusing any resources of the compressor
17/// ```rust
18/// use ruzstd::encoding::{compress, CompressionLevel};
19/// let data: &[u8] = &[0,0,0,0,0,0,0,0,0,0,0,0];
20/// let mut target = Vec::new();
21/// compress(data, &mut target, CompressionLevel::Fastest);
22/// ```
23pub fn compress<R: Read, W: Write>(source: R, target: W, level: CompressionLevel) {
24    let mut frame_enc = FrameCompressor::new(level);
25    frame_enc.set_source(source);
26    frame_enc.set_drain(target);
27    frame_enc.compress();
28}
29
30/// Convenience function to compress some source into a Vec without reusing any resources of the compressor
31/// ```rust
32/// use ruzstd::encoding::{compress_to_vec, CompressionLevel};
33/// let data: &[u8] = &[0,0,0,0,0,0,0,0,0,0,0,0];
34/// let compressed = compress_to_vec(data, CompressionLevel::Fastest);
35/// ```
36pub fn compress_to_vec<R: Read>(source: R, level: CompressionLevel) -> Vec<u8> {
37    let mut vec = Vec::new();
38    compress(source, &mut vec, level);
39    vec
40}
41
42/// The compression mode used impacts the speed of compression,
43/// and resulting compression ratios. Faster compression will result
44/// in worse compression ratios, and vice versa.
45#[derive(Copy, Clone)]
46pub enum CompressionLevel {
47    /// This level does not compress the data at all, and simply wraps
48    /// it in a Zstandard frame.
49    Uncompressed,
50    /// This level is roughly equivalent to Zstd compression level 1
51    Fastest,
52    /// This level is roughly equivalent to Zstd level 3,
53    /// or the one used by the official compressor when no level
54    /// is specified.
55    ///
56    /// UNIMPLEMENTED
57    Default,
58    /// This level is roughly equivalent to Zstd level 7.
59    ///
60    /// UNIMPLEMENTED
61    Better,
62    /// This level is roughly equivalent to Zstd level 11.
63    ///
64    /// UNIMPLEMENTED
65    Best,
66}
67
68/// Trait used by the encoder that users can use to extend the matching facilities with their own algorithm
69/// making their own tradeoffs between runtime, memory usage and compression ratio
70///
71/// This trait operates on buffers that represent the chunks of data the matching algorithm wants to work on.
72/// Each one of these buffers is referred to as a *space*. One or more of these buffers represent the window
73/// the decoder will need to decode the data again.
74///
75/// This library asks the Matcher for a new buffer using `get_next_space` to allow reusing of allocated buffers when they are no longer part of the
76/// window of data that is being used for matching.
77///
78/// The library fills the buffer with data that is to be compressed and commits them back to the matcher using `commit_space`.
79///
80/// Then it will either call `start_matching` or, if the space is deemed not worth compressing, `skip_matching` is called.
81///
82/// This is repeated until no more data is left to be compressed.
83pub trait Matcher {
84    /// Get a space where we can put data to be matched on. Will be encoded as one block. The maximum allowed size is 128 kB.
85    fn get_next_space(&mut self) -> alloc::vec::Vec<u8>;
86    /// Get a reference to the last commited space
87    fn get_last_space(&mut self) -> &[u8];
88    /// Commit a space to the matcher so it can be matched against
89    fn commit_space(&mut self, space: alloc::vec::Vec<u8>);
90    /// Just process the data in the last commited space for future matching
91    fn skip_matching(&mut self);
92    /// Process the data in the last commited space for future matching AND generate matches for the data
93    fn start_matching(&mut self, handle_sequence: impl for<'a> FnMut(Sequence<'a>));
94    /// Reset this matcher so it can be used for the next new frame
95    fn reset(&mut self, level: CompressionLevel);
96    /// The size of the window the decoder will need to execute all sequences produced by this matcher
97    ///
98    /// May change after a call to reset with a different compression level
99    fn window_size(&self) -> u64;
100}
101
102#[derive(PartialEq, Eq, Debug)]
103/// Sequences that a [`Matcher`] can produce
104pub enum Sequence<'data> {
105    /// Is encoded as a sequence for the decoder sequence execution.
106    ///
107    /// First the literals will be copied to the decoded data,
108    /// then `match_len` bytes are copied from `offset` bytes back in the buffer
109    Triple {
110        literals: &'data [u8],
111        offset: usize,
112        match_len: usize,
113    },
114    /// This is returned as the last sequence in a block
115    ///
116    /// These literals will just be copied at the end of the sequence execution by the decoder
117    Literals { literals: &'data [u8] },
118}
ruzstd/encoding/mod.rs

ruzstd/encoding/
mod.rs
