CoffeeScript Simple MD5

gistfile1.coffee

# Array sum helper function.
sum = (array) ->
  array.reduce (x, y) -> x + y

md5 = do -> 
  # Per-round shift amounts.
  s = [738695, 669989, 770404, 703814]
  s = (s[i >> 4] >> i % 4 * 5 & 31 for i in [0..63])
  
  # Constants cache generated by sine.
  K = (Math.floor 2**32 * Math.abs Math.sin i for i in [1..64])
  
  # Bitwise left rotate helper function.
  lrot = (x, y) ->
    x << y | x >>> 32 - y;
  
  (input) ->
    # Initialize values.
    d0 = 0x10325476;
    a0 = 0x67452301;
    b0 = ~d0
    c0 = ~a0;
    
    # Convert the message to 32-bit words, little-endian.
    M = 
      for i in [0...input.length] by 4
        sum (input.charCodeAt(i + j) << j*8 for j in [0..3])
    
    # Pre-processing: append a 1 bit, then message length % 2^64.
    len = input.length * 8
    M[len >> 5] |= 128 << len % 32
    M[(len + 64 >>> 9 << 4) + 14] = len
    
    # Process the message in chunks of 16 32-bit words.
    for x in [0...M.length] by 16
      [A, B, C, D] = [a0, b0, c0, d0]
      
      # Main loop.
      for i in [0..63]
        if i < 16
          F = B & C | ~B & D
          g = i
        else if i < 32
          F = B & D | C & ~D
          g = i * 5 + 1
        else if i < 48
          F = B ^ C ^ D
          g = i * 3 + 5
        else
          F = C ^ (B | ~D)
          g = i * 7
        
        [A, B, C, D] =
          [D, B + lrot(A + F + K[i] + (M[x + g % 16] ? 0), s[i]), B, C]
      
      a0 += A
      b0 += B
      c0 += C
      d0 += D
    
    # Convert the four words back to a string.
    return (
      for x in [a0, b0, c0, d0]
        (String.fromCharCode x >>> 8 * y & 255 for y in [0..3]).join ''
    ).join ''

To get the hex encoded value, check out my hex codec functions for CoffeeScript.

And be sure to encode strings into byte strings first! Use my UTF-8 codec functions for CoffeeScript.