Class: Fairy::HValueGenerator::MurMur

Inherits:
Object
  • Object
show all
Defined in:
lib/fairy/share/hash-murmur.rb

Overview

mhash is modiftied from MurmerHash(murmurhash.googlepages.com/).

Constant Summary collapse

FIX_MASK = 
0x3fff_ffff
MASK24 = 
0xffff_ffff_ffff
MAGIC = 
0x7fd652ad & FIX_MASK
R = 
18

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(h) ⇒ MurMur

Returns a new instance of MurMur.



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# File 'lib/fairy/share/hash-murmur.rb', line 17

def initialize(h)
  @seed = h + 0xdeadbeef & FIX_MASK
# @postfix = [@seed].pack("N")[1..3]
  @postfix = "000"
end

Class Method Details

.create_seed ⇒ Object 



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# File 'lib/fairy/share/hash-murmur.rb', line 54

def MurMur.create_seed
  rand(FIX_MASK)
end

Instance Method Details

#str_hash(data) ⇒ Object 



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# File 'lib/fairy/share/hash-murmur.rb', line 32

def str_hash(data)
  h = @seed

  for k in (data+@postfix).unpack("N*")
    k *= MAGIC
    k ^= k >> R
    k &= FIX_MASK
    k *= MAGIC
    k &= FIX_MASK

    h = @seed * MAGIC
    k &= FIX_MASK
    h ^= k
  end

  h ^= h >> 13
  h *= MAGIC
  h &= FIX_MASK
  h ^= h >> 15
  h
end

#value(data) ⇒ Object 



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# File 'lib/fairy/share/hash-murmur.rb', line 23

def value(data)
  case data
  when String
    str_hash(data)
  else
    ERR::Raise ERR::NoImpliment, "non-string key(#{data.inspect})"
  end
end