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;
12pub use match_generator::MatchGeneratorDriver;
13
14use crate::io::{Read, Write};
15use alloc::vec::Vec;
16
17/// Convenience function to compress some source into a target without reusing any resources of the compressor
18/// ```rust
19/// use ruzstd::encoding::{compress, CompressionLevel};
20/// let data: &[u8] = &[0,0,0,0,0,0,0,0,0,0,0,0];
21/// let mut target = Vec::new();
22/// compress(data, &mut target, CompressionLevel::Fastest);
23/// ```
24pub fn compress<R: Read, W: Write>(source: R, target: W, level: CompressionLevel) {
25    let mut frame_enc = FrameCompressor::new(level);
26    frame_enc.set_source(source);
27    frame_enc.set_drain(target);
28    frame_enc.compress();
29}
30
31/// Convenience function to compress some source into a Vec without reusing any resources of the compressor
32/// ```rust
33/// use ruzstd::encoding::{compress_to_vec, CompressionLevel};
34/// let data: &[u8] = &[0,0,0,0,0,0,0,0,0,0,0,0];
35/// let compressed = compress_to_vec(data, CompressionLevel::Fastest);
36/// ```
37pub fn compress_to_vec<R: Read>(source: R, level: CompressionLevel) -> Vec<u8> {
38    let mut vec = Vec::new();
39    compress(source, &mut vec, level);
40    vec
41}
42
43/// The compression mode used impacts the speed of compression,
44/// and resulting compression ratios. Faster compression will result
45/// in worse compression ratios, and vice versa.
46#[derive(Copy, Clone)]
47pub enum CompressionLevel {
48    /// This level does not compress the data at all, and simply wraps
49    /// it in a Zstandard frame.
50    Uncompressed,
51    /// This level is roughly equivalent to Zstd compression level 1
52    Fastest,
53    /// This level is roughly equivalent to Zstd level 3,
54    /// or the one used by the official compressor when no level
55    /// is specified.
56    ///
57    /// UNIMPLEMENTED
58    Default,
59    /// This level is roughly equivalent to Zstd level 7.
60    ///
61    /// UNIMPLEMENTED
62    Better,
63    /// This level is roughly equivalent to Zstd level 11.
64    ///
65    /// UNIMPLEMENTED
66    Best,
67}
68
69/// Trait used by the encoder that users can use to extend the matching facilities with their own algorithm
70/// making their own tradeoffs between runtime, memory usage and compression ratio
71///
72/// This trait operates on buffers that represent the chunks of data the matching algorithm wants to work on.
73/// Each one of these buffers is referred to as a *space*. One or more of these buffers represent the window
74/// the decoder will need to decode the data again.
75///
76/// 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
77/// window of data that is being used for matching.
78///
79/// The library fills the buffer with data that is to be compressed and commits them back to the matcher using `commit_space`.
80///
81/// Then it will either call `start_matching` or, if the space is deemed not worth compressing, `skip_matching` is called.
82///
83/// This is repeated until no more data is left to be compressed.
84pub trait Matcher {
85    /// 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.
86    fn get_next_space(&mut self) -> alloc::vec::Vec<u8>;
87    /// Get a reference to the last commited space
88    fn get_last_space(&mut self) -> &[u8];
89    /// Commit a space to the matcher so it can be matched against
90    fn commit_space(&mut self, space: alloc::vec::Vec<u8>);
91    /// Just process the data in the last commited space for future matching
92    fn skip_matching(&mut self);
93    /// Process the data in the last commited space for future matching AND generate matches for the data
94    fn start_matching(&mut self, handle_sequence: impl for<'a> FnMut(Sequence<'a>));
95    /// Reset this matcher so it can be used for the next new frame
96    fn reset(&mut self, level: CompressionLevel);
97    /// The size of the window the decoder will need to execute all sequences produced by this matcher
98    ///
99    /// May change after a call to reset with a different compression level
100    fn window_size(&self) -> u64;
101}
102
103#[derive(PartialEq, Eq, Debug)]
104/// Sequences that a [`Matcher`] can produce
105pub enum Sequence<'data> {
106    /// Is encoded as a sequence for the decoder sequence execution.
107    ///
108    /// First the literals will be copied to the decoded data,
109    /// then `match_len` bytes are copied from `offset` bytes back in the decoded data
110    Triple {
111        literals: &'data [u8],
112        offset: usize,
113        match_len: usize,
114    },
115    /// This is returned as the last sequence in a block
116    ///
117    /// These literals will just be copied at the end of the sequence execution by the decoder
118    Literals { literals: &'data [u8] },
119}
ruzstd/encoding/mod.rs

ruzstd/encoding/
mod.rs
