module Sprockets::DigestUtils

def integrity_uri(digest)

Returns a String or nil if hash algorithm is incompatible.

digest - The String byte digest of the asset content.

as per the subresource integrity specification.
Public: Generate hash for use in the `integrity` attribute of an asset tag 
def integrity_uri(digest)
  case digest
  when Digest::Base
    digest_class = digest.class
    digest = digest.digest
  when String
    digest_class = DIGEST_SIZES[digest.bytesize]
  else
    raise TypeError, "unknown digest: #{digest.inspect}"
  end
  if hash_name = HASH_ALGORITHMS[digest_class]
    "#{hash_name}-#{pack_base64digest(digest)}"
  end
end