Enum CompressionLevel 

pub enum CompressionLevel {
    Uncompressed,
    Fastest,
    Default,
    Better,
    Best,
}

The compression mode used impacts the speed of compression, and resulting compression ratios. Faster compression will result in worse compression ratios, and vice versa.

Variants

Uncompressed

This level does not compress the data at all, and simply wraps it in a Zstandard frame.

Fastest

This level is roughly equivalent to Zstd compression level 1

Default

This level uses the crate’s dedicated dfast-style matcher to target a better speed/ratio tradeoff than CompressionLevel::Fastest.

It represents this crate’s “default” compression setting and may evolve in future versions as the implementation moves closer to reference zstd level 3 behavior.

Better

This level is roughly equivalent to Zstd level 7.

Uses the hash-chain matcher with a lazy2 matching strategy: the encoder evaluates up to two positions ahead before committing to a match, trading speed for a better compression ratio than CompressionLevel::Default.

Limitation: hash-chain tables use 32-bit positions. For single-frame inputs exceeding ~4 GiB, matches can still be found for roughly one window past that point; once all in-window positions exceed u32::MAX (≈4 GiB + window size), matching becomes effectively repcode-only. Prefer CompressionLevel::Default for very large single-frame streams until table rebasing is implemented.

Best

This level is roughly equivalent to Zstd level 11.

Uses the hash-chain matcher with a deep lazy2 matching strategy and a 16 MiB window. Compared to CompressionLevel::Better, this level uses larger hash and chain tables (2 M / 1 M entries vs 1 M / 512 K), a deeper search (32 candidates vs 16), and a higher target match length (128 vs 48), trading speed for the best compression ratio available in this crate.

Limitation: hash-chain tables use 32-bit positions. For single-frame inputs exceeding ~4 GiB, matches can still be found for roughly one window past that point; once all in-window positions exceed u32::MAX (≈4 GiB + window size), matching becomes effectively repcode-only. Prefer CompressionLevel::Default for very large single-frame streams until table rebasing is implemented.

Trait Implementations

impl Clone for CompressionLevel

fn clone(&self) -> CompressionLevel

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for CompressionLevel