non-obfuscated adler32

adler32.js

function adler32(string) {
  var length  = string.length
    , modulus = 65521
    , index   = 0
    , a       = 1
    , b       = 0

  while (index < length) {
    a += string.charCodeAt(index++)
    a %= modulus
    b += a
    b %= modulus
  }

  return b << 16 | a
}