Class: Murmur3

Inherits:
Object
  • Object
show all
Defined in:
lib/prefab/murmer3.rb

Constant Summary collapse

MASK32 =

MurmurHash3 was written by Austin Appleby, and is placed in the public domain. The author hereby disclaims copyright to this source code.

0xffffffff

Class Method Summary collapse

Class Method Details

.murmur3_32(str, seed = 0) ⇒ Object 



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# File 'lib/prefab/murmer3.rb', line 28

def self.murmur3_32(str, seed=0)
  h1 = seed
  numbers = str.unpack('V*C*')
  tailn = str.length % 4
  tail = numbers.slice!(numbers.size - tailn, tailn)
  for k1 in numbers
    h1 ^= murmur3_32__mmix(k1)
    h1 = murmur3_32_rotl(h1, 13)
    h1 = (h1*5 + 0xe6546b64) & MASK32
  end

  unless tail.empty?
    k1 = 0
    tail.reverse_each do |c1|
      k1 = (k1 << 8) | c1
    end
    h1 ^= murmur3_32__mmix(k1)
  end

  h1 ^= str.length
  murmur3_32_fmix(h1)
end

.murmur3_32__mmix(k1) ⇒ Object 



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# File 'lib/prefab/murmer3.rb', line 22

def self.murmur3_32__mmix(k1)
  k1 = (k1 * 0xcc9e2d51) & MASK32
  k1 = murmur3_32_rotl(k1, 15)
  (k1 * 0x1b873593) & MASK32
end

.murmur3_32_fmix(h) ⇒ Object 



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# File 'lib/prefab/murmer3.rb', line 13

def self.murmur3_32_fmix(h)
  h &= MASK32
  h ^= h >> 16
  h = (h * 0x85ebca6b) & MASK32
  h ^= h >> 13
  h = (h * 0xc2b2ae35) & MASK32
  h ^ (h >> 16)
end

.murmur3_32_rotl(x, r) ⇒ Object 



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# File 'lib/prefab/murmer3.rb', line 8

def self.murmur3_32_rotl(x, r)
  ((x << r) | (x >> (32 - r))) & MASK32
end