Struct BuzHash 

pub struct BuzHash<H: BuzHashHash> { /* private fields */ }

Describes an instance of BuzHash (aka cyclic polynomial hash).

Provides parameterization over the window size (k), hash function (h), chunk edge mask, and max chunk size.

Uses fixed 32-bit width for the hash.

The trait BuzHashHash provides the internal hash function, see the implimentations of it for built-in hash options (which include both Borg and silvasur/buzhash’s internal hash tables).

Note that it’s helpful for k to be prime to prevent repeating strings form resulting in total cancelation of the internal hash, which can cause overly long chunks.

Adjusting mask changes the average chunk size.

Performance

BuzHash requires storing bytes equal to it’s window size (k). Because of this, BuzHashIncr may have poor performance compared to BuzHash::find_chunk_edge().

Implementations

impl<H: BuzHashHash> BuzHash<H>

pub fn new(capacity: usize, mask: u32, hash: H, max_chunk_size: u64) -> Self

Create an instance with the given capacity (k) and chunk termination mask, and a internal hash function.

capacity is the number of bytes that are taken into account for a given hash. mask affects how chunk edges are determined. hash is applied to each byte of input prior to mixing into the rolling hash.

impl<'a> BuzHash<BuzHashTableByteSaltHash<'a>>

pub fn new_nom(salt: u8) -> Self

Create a buzhash instance using defaults from attic-labs/nom version 7.17

• k: 67
• hash is the silvasur/buzhash table
• mask: 1<<12 -1
• max_chunk_size: 1 << 24

Trait Implementations

impl<H: BuzHashHash + Clone> Chunk for BuzHash<H>

type SearchState = BuzHashSearchState

SearchState allows searching for the chunk edge to resume without duplicating work already done.

fn to_search_state(&self) -> Self::SearchState

Provide an initial [SearchState] for use with [find_chunk_edge()]. Generally, for each input one should generate a new [SearchState].

fn find_chunk_edge( &self, state: &mut Self::SearchState, data: &[u8], ) -> (Option<usize>, usize)

Find the next “chunk” in data to emit

impl<H: Clone + BuzHashHash> Clone for BuzHash<H>

fn clone(&self) -> BuzHash<H>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<H: Debug + BuzHashHash> Debug for BuzHash<H>

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

Formats the value using the given formatter.

impl<H: BuzHashHash + Clone> From<&BuzHash<H>> for BuzHashIncr<H>

fn from(src: &BuzHash<H>) -> Self

Converts to this type from the input type.

impl<H: BuzHashHash> From<BuzHash<H>> for BuzHashIncr<H>

fn from(params: BuzHash<H>) -> Self

Converts to this type from the input type.

impl<H: PartialEq + BuzHashHash> PartialEq for BuzHash<H>

fn eq(&self, other: &BuzHash<H>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<H: BuzHashHash + Clone> ToChunkIncr for BuzHash<H>

type Incr = BuzHashIncr<H>

Incr provides the incrimental interface to this chunking instance

fn to_chunk_incr(&self) -> Self::Incr

to_chunk_incr() returns a ChunkIncr which can be incrimentally fed data and emits chunks.

impl<H: Eq + BuzHashHash> Eq for BuzHash<H>

impl<H: BuzHashHash> StructuralPartialEq for BuzHash<H>