Class: XXhash

Inherits:
Object
  • Object
show all
Defined in:
lib/xxhash.rb,
lib/xxhash/version.rb

Constant Summary collapse

VERSION = 
"0.0.2"
@@mem_total_size = 
16
@@prime32_1 = 
2654435761
@@prime32_2 = 
2246822519
@@prime32_3 = 
3266489917
@@prime32_4 = 
668265263
@@prime32_5 = 
374761393
@@thirtytwo1s = 
(2**32-1)

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(seed) ⇒ XXhash

Returns a new instance of XXhash.



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# File 'lib/xxhash.rb', line 29

def initialize seed
  @seed = seed
  @v1 = seed + @@prime32_1 + @@prime32_2
  @v2 = seed + @@prime32_2
  @v3 = seed + 0
  @v4 = seed - @@prime32_1
  @total_len = 0
  @memory = Array.new(@@mem_total_size)
  @memsize = 0
end

Class Method Details

.xxh32(input, seed = 0) ⇒ Object 



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# File 'lib/xxhash.rb', line 13

def XXhash.xxh32(input, seed = 0)
  xxh = XXhash.new(seed)
  xxh.feed(input)
  xxh.sum32
end

.xxh32_stream(io, seed = 0, chunk = 1024) ⇒ Object 



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# File 'lib/xxhash.rb', line 19

def XXhash.xxh32_stream(io, seed = 0, chunk = 1024)
  xxh = XXhash.new(seed)

  while(data = io.read(chunk))
    xxh.feed(data)
  end

  xxh.sum32
end

Instance Method Details

#feed(bytes) ⇒ Object 



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# File 'lib/xxhash.rb', line 41

def feed bytes
    if String === bytes
      bytes = bytes.unpack("C*")
    end

    @total_len += bytes.length

    p = 0

    while (remaining = (bytes.length - p)) > 0

      mem_avail = @@mem_total_size - @memsize

      if(remaining < mem_avail)
       @memory[@memsize, remaining] = bytes[p, remaining]
       @memsize += remaining
       break
     end

     @memory[@memsize, mem_avail] = bytes[p, mem_avail]

     i = 0
     [:v1, :v2, :v3, :v4].each do |m|
      p32 = uint32(
        @memory[i] |
        (@memory[i+1] << 8) |
        (@memory[i+2] << 16) |
        (@memory[i+3] << 24))

      v = uint32(self.send(m) + p32 * @@prime32_2)
      v = uint32(uint32((v << 13) | (v >> (32 - 13))) * @@prime32_1)
      self.send((m.to_s + "=").to_sym, v)
      i += 4
    end

    p += mem_avail
    @memsize = 0
  end

  return true
end

#sum32 ⇒ Object 



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# File 'lib/xxhash.rb', line 83

def sum32
  if @total_len >= 16
    h32 = ((@v1 << 1) | (@v1 >> (32 - 1))) +
    ((@v2 << 7) | (@v2 >> (32 - 7))) +
    ((@v3 << 12) | (@v3 >> (32 - 12))) +
    ((@v4 << 18) | (@v4 >> (32 - 18)))
  else
    h32 = @seed + @@prime32_5
  end

  h32 = uint32(h32 + @total_len)

  p = 0
  while p <= (@memsize - 4)
    p32 = uint32(@memory[p] |
      (@memory[p+1] << 8) |
      (@memory[p+2] << 16) |
      (@memory[p+3] << 24))
    h32 = uint32(h32 + p32 * @@prime32_3)
    h32 = uint32(uint32((h32 << 17) | (h32 >> (32 - 17))) * @@prime32_4)
    p += 4
  end

  while p < @memsize
    h32 = uint32(h32 + @memory[p] * @@prime32_5)
    h32 = uint32(uint32((h32 << 11) | (h32 >> (32 - 11))) * @@prime32_1)
    p += 1
  end

  h32 ^= h32 >> 15
  h32 = uint32(h32 * @@prime32_2)
  h32 ^= h32 >> 13
  h32 = uint32(h32 * @@prime32_3)
  h32 ^= h32 >> 16

  h32
end