module Bundler::Digest

def sha1(string)
  unless string.is_a?(String)
    raise TypeError, "can't convert #{string.class.inspect} into String"
  end
  buffer = string.b
  words = SHA1_WORDS.dup
  generate_split_buffer(buffer) do |chunk|
    w = []
    chunk.each_slice(4) do |a, b, c, d|
      w << (((a << 8 | b) << 8 | c) << 8 | d)
    end
    a, b, c, d, e = *words
    (16..79).each do |i|
      w[i] = SHA1_MASK & rotate((w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16]), 1)
    end
    0.upto(79) do |i|
      case i
      when  0..19
        f = ((b & c) | (~b & d))
        k = 0x5A827999
      when 20..39
        f = (b ^ c ^ d)
        k = 0x6ED9EBA1
      when 40..59
        f = ((b & c) | (b & d) | (c & d))
        k = 0x8F1BBCDC
      when 60..79
        f = (b ^ c ^ d)
        k = 0xCA62C1D6
      end
      t = SHA1_MASK & rotate(a, 5) + f + e + k + w[i]
      a, b, c, d, e = t, a, SHA1_MASK & rotate(b, 30), c, d # rubocop:disable Style/ParallelAssignment
    end
    mutated = [a, b, c, d, e]
    words.map!.with_index {|word, index| SHA1_MASK & (word + mutated[index]) }
  end
  words.pack("N*").unpack("H*").first
end