Crate umash[−][src]
Expand description
UMASH is an almost-universal family of hash functions. Each
Params struct defines a specific hash function; when the
parameters are generated pseudorandomly, the probability that two
different inputs of up to s bytes collide (for an independently
generated set of parameters) is at most ceil(s / 4096) 2^-55 for
the 64-bit hash. The 128-bit fingerprint reduces that probability
to less than 2^-70 for inputs of 1 GB or less.
See the reference repo for more details and proofs.
Structs
A 128-bit Fingerprint is constructed by UMASH as if we had
computed the UmashComponent::Hash and
UmashComponent::Secondary functions, and stored them in the
Fingerprint::hash array in order.
A Fingerprinter implements the 128-bit fingerprinting function
defined by a specific Params struct, further tweaked by a seed.
Construct Fingerprinters with Params::fingerprinter.
A Hasher implements one of the two hash 64-bit functions
defined by a specific Params struct, further tweaked by a
seed. Construct Hashers with Params::hasher,
Params::secondary_hasher, or Params::component_hasher.
Enums
A given Params struct defines a pair of 64-bit hash functions.
The UmashComponent::Hash is the primary hash value; we find a
128-bit fingerprint by combining that primary value with the
UmashComponent::Secondary hash (in practice, it’s more
efficient to compute both hash values concurrently, when one knows
they want a fingerprint).