MurmurHash3_x64_128 (64-bit output).
This module implements the full MurmurHash3_x64_128 algorithm and returns the high 64 bits of the 128-bit output. This matches the convention used by Apache DataSketches when a 64-bit hash is needed.
Murmur3 is not the default for ExDataSketch (XXHash3 is faster and the default), but it is provided for interoperability with the Apache DataSketches ecosystem and as a portable BEAM-side reference implementation.
Properties
| Property | Value |
|---|---|
| Output bits | 64 (high half of x64_128) |
| Seedable | Yes (u32) |
| Cross-platform | Yes |
| Cross-OTP stable | Yes — pure Elixir, no :erlang.phash2 |
| Rust acceleration | Yes (internal NIF, see hash/2) |
When the Rust NIF is available, hash/2 dispatches to it. When it is not,
the pure Elixir implementation is used. Both implementations are
byte-identical on every input (verified by parity tests).
Examples
iex> ExDataSketch.Hash.Murmur3.hash("hello") == ExDataSketch.Hash.Murmur3.hash("hello")
true
iex> ExDataSketch.Hash.Murmur3.hash("hello", 0) != ExDataSketch.Hash.Murmur3.hash("hello", 1)
true
iex> ExDataSketch.Hash.Murmur3.hash("", 0) >= 0
trueReference
- Austin Appleby's reference implementation: https://github.com/aappleby/smhasher
- Apache DataSketches Java:
org.apache.datasketches.hash.MurmurHash3
Summary
Functions
Returns whether this algorithm is available in the current runtime.
Returns the full 128-bit MurmurHash3_x64_128 as a {h1, h2} pair.
Computes the high 64 bits of MurmurHash3_x64_128 over the given binary.
Returns the algorithm identifier :murmur3.
Pure Elixir implementation of MurmurHash3_x64_128 returning the high 64 bits.
Functions
@spec available?() :: true
Returns whether this algorithm is available in the current runtime.
Murmur3 is always available because a pure-Elixir implementation is bundled.
Examples
iex> ExDataSketch.Hash.Murmur3.available?()
true@spec hash128(binary(), non_neg_integer()) :: {non_neg_integer(), non_neg_integer()}
Returns the full 128-bit MurmurHash3_x64_128 as a {h1, h2} pair.
Provided for interop scenarios where the full 128-bit hash is required (e.g., computing Apache DataSketches seed_hash, or other Murmur3-based fingerprints).
Examples
iex> {h1, h2} = ExDataSketch.Hash.Murmur3.hash128("hello", 0)
iex> is_integer(h1) and is_integer(h2)
true@spec hash(binary(), non_neg_integer()) :: ExDataSketch.Hash.hash64()
Computes the high 64 bits of MurmurHash3_x64_128 over the given binary.
The seed is the standard Murmur3 u32 seed; values above 2^32 - 1
are masked to 32 bits.
Examples
iex> h = ExDataSketch.Hash.Murmur3.hash("hello", 0)
iex> is_integer(h) and h >= 0 and h <= 0xFFFFFFFFFFFFFFFF
true@spec id() :: :murmur3
Returns the algorithm identifier :murmur3.
Examples
iex> ExDataSketch.Hash.Murmur3.id()
:murmur3@spec pure_hash(binary(), non_neg_integer()) :: ExDataSketch.Hash.hash64()
Pure Elixir implementation of MurmurHash3_x64_128 returning the high 64 bits.
This function never calls the NIF. It is used by the parity tests and as
the fallback when the NIF is unavailable. Keep this function deterministic
across all OTP versions — it must not depend on :erlang.phash2/1,2.
Examples
iex> ExDataSketch.Hash.Murmur3.pure_hash("hello", 0) == ExDataSketch.Hash.Murmur3.hash("hello", 0)
true