Enum BlockSizeRelation

pub enum BlockSizeRelation {
    NearLt,
    NearEq,
    NearGt,
    Far,
}

A type to represent relation between two block sizes.

Because the core comparison function can only compare two block hashes with the same effective block size, we cannot compare two fuzzy hashes if their block sizes are not near enough.

There are three cases where we can perform actual block hash comparison:

1. Equals (NearEq)
   bs_a == bs_b
2. Less than (NearLt)
   bs_a < bs_b && bs_a * 2 == bs_b
3. Greater than (NearGt)
   bs_a > bs_b && bs_a == bs_b * 2

See also: “Relations with Block Size” section of FuzzyHashData

This type represents those near cases (three variants) and the case which two fuzzy hashes cannot perform a block hash comparison, the far case (the Far variant).

A value of this type can be retrieved by using block_size::compare_sizes() or FuzzyHashData::compare_block_sizes().

Compatibility Note

Since the version 0.3, the representation of this enum is no longer specified as specific representation of this enum is not important.

Variants

NearLt

Near and less than (i.e. x < x * 2).

Two block sizes are near and the block hash 2 (one with a larger block size) of the left side (of comparison) can be compared with the block hash 1 (one with a smaller block size) of the right side.

NearEq

Near and equals (i.e. x == x).

Two block sizes are not just near but the same. We compare both block hashes with the other and take the maximum value for the output.

NearGt

Near and greater than (i.e. x * 2 > x).

Two block sizes are near and the block hash 1 (one with a smaller block size) of the left side (of comparison) can be compared with the block hash 2 (one with a larger block size) of the right side.

Far

Far (e.g. x and x * 4).

Two block sizes are far and a block hash comparison cannot be performed.

Implementations

impl BlockSizeRelation

pub fn is_near(&self) -> bool

Checks whether a given value denotes one of the three near cases.

Trait Implementations

impl Clone for BlockSizeRelation

fn clone(&self) -> BlockSizeRelation

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for BlockSizeRelation

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

Formats the value using the given formatter.

impl PartialEq for BlockSizeRelation

fn eq(&self, other: &BlockSizeRelation) -> 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 Copy for BlockSizeRelation

impl Eq for BlockSizeRelation

impl StructuralPartialEq for BlockSizeRelation