Struct GearChunker 

pub struct GearChunker {
    pub min: usize,
    pub avg: usize,
    pub max: usize,
    pub normalization_level: u8,
}

Gear hash rolling chunker configuration.

Fields

min: usize

avg: usize

max: usize

normalization_level: u8

Normalization level for chunk size distribution.

• 0: Legacy single-mask (geometric distribution, backward compatible)
• 1: FastCDC normalized (dual-mask, tighter distribution around avg)
• 2: Aggressive normalization (very tight, may reduce dedup ratio)

CAS Compatibility Warning

Changing this field produces different chunk boundaries and therefore different BLAKE3 chunk hashes. Existing CAS data will not deduplicate against chunks produced at a different normalization level.

Implementations

impl GearChunker

pub fn new(min: usize, avg: usize, max: usize) -> Result<Self>

Create a new gear hash chunker with the given size bounds.

pub fn with_normalization(self, level: u8) -> Result<Self>

Set the normalization level for chunk size distribution.

Returns an error if level > 2 – higher levels shift masks beyond useful ranges. Also rejects configurations where logarithm2(avg) <= level, which would produce a zero mask_l (MASKS[0]) causing degenerate 1-byte chunks.

pub fn chunk_reader<R: Read>(&self, reader: R) -> Result<Vec<Chunk>>

👎Deprecated:

Use StreamingChunker for files > 16 MB

Chunk an entire reader, returning all chunks with their BLAKE3 hashes.

Limits

Rejects inputs larger than 16 MB to prevent OOM. Use StreamingChunker for arbitrarily large files.

pub fn find_boundaries(&self, data: &[u8]) -> Vec<usize>

Find chunk boundaries in a byte slice using gear hash.

When normalization_level == 0, uses a single mask (avg - 1) – backward-compatible with all existing data. When > 0, uses FastCDC dual-mask: a stricter mask_s below avg and a relaxed mask_l above avg, tightening the chunk-size distribution.

pub fn chunk_slice(&self, data: &[u8]) -> Vec<Chunk>

Chunk from a byte slice directly (avoids double-copy for in-memory data).

Trait Implementations

impl Debug for GearChunker

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for GearChunker

fn default() -> Self

Returns the “default value” for a type.