class Digest::SHA2

def initialize(bitlen = 256)

Valid bit lengths are 256, 384 and 512.

Create a new SHA2 hash object with a given bit length.

Digest::SHA2.new(bitlen = 256) -> digest_obj
call-seq: 
def initialize(bitlen = 256)
  case bitlen
  when 256
    @sha2 = Digest::SHA256.new
  when 384
    @sha2 = Digest::SHA384.new
  when 512
    @sha2 = Digest::SHA512.new
  else
    raise ArgumentError, "unsupported bit length: %s" % bitlen.inspect
  end
  @bitlen = bitlen
end