Module: Sprockets::DigestUtils

### Home Classes Methods

### In Files

- lib/sprockets/digest_utils.rb

### Methods

- #detect_digest_class
- #digest
- #digest_class
- #hexdigest_integrity_uri
- #integrity_uri
- #pack_base64digest
- #pack_hexdigest
- #pack_urlsafe_base64digest
- #unpack_hexdigest

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# Sprockets::DigestUtils

Internal: Hash functions and digest related utilities. Mixed into Environment.

### Constants

DIGEST_SIZES

  Internal: Maps digest bytesize to the digest class.

HASH_ALGORITHMS

  Internal: Maps digest class to the CSP hash algorithm name.

### Public Instance Methods

detect_digest_class(bytes) click to toggle source

Internal: Detect digest class hash algorithm for digest bytes.

While not elegant, all the supported digests have a unique bytesize.

Returns Digest::Base or nil.

    # File lib/sprockets/digest_utils.rb, line 33
    def detect_digest_class(bytes)
      DIGEST_SIZES[bytes.bytesize]
    end

digest(obj) click to toggle source

Internal: Generate a hexdigest for a nested JSON serializable object.

This is used for generating cache keys, so its pretty important its wicked fast. Microbenchmarks away!

obj - A JSON serializable object.

Returns a String digest of the object.

    # File lib/sprockets/digest_utils.rb, line 45
    def digest(obj)
      digest = digest_class.new
      queue  = [obj]

      while queue.length > 0
        obj = queue.shift
        klass = obj.class

        if klass == String
          digest << obj
        elsif klass == Symbol
          digest << 'Symbol'
          digest << obj.to_s
        elsif klass == Fixnum
          digest << 'Fixnum'
          digest << obj.to_s
        elsif klass == Bignum
          digest << 'Bignum'
          digest << obj.to_s
        elsif klass == TrueClass
          digest << 'TrueClass'
        elsif klass == FalseClass
          digest << 'FalseClass'
        elsif klass == NilClass
          digest << 'NilClass'.freeze
        elsif klass == Array
          digest << 'Array'
          queue.concat(obj)
        elsif klass == Hash
          digest << 'Hash'
          queue.concat(obj.sort)
        elsif klass == Set
          digest << 'Set'
          queue.concat(obj.to_a)
        elsif klass == Encoding
          digest << 'Encoding'
          digest << obj.name
        else
          raise TypeError, "couldn't digest #{klass}"
        end
      end

      digest.digest
    end

digest_class() click to toggle source

Internal: Default digest class.

Returns a Digest::Base subclass.

    # File lib/sprockets/digest_utils.rb, line 15
    def digest_class
      Digest::SHA256
    end

hexdigest_integrity_uri(hexdigest) click to toggle source

Public: Generate hash for use in the `integrity` attribute of an asset tag as per the subresource integrity specification.

digest - The String hexbyte digest of the asset content.

Returns a String or nil if hash algorithm is incompatible.

    # File lib/sprockets/digest_utils.rb, line 164
    def hexdigest_integrity_uri(hexdigest)
      integrity_uri(unpack_hexdigest(hexdigest))
    end

integrity_uri(digest) click to toggle source

Public: Generate hash for use in the `integrity` attribute of an asset tag as per the subresource integrity specification.

digest - The String byte digest of the asset content.

Returns a String or nil if hash algorithm is incompatible.

    # File lib/sprockets/digest_utils.rb, line 142
    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

pack_base64digest(bin) click to toggle source

Internal: Pack a binary digest to a base64 encoded string.

bin - String bytes

Returns base64 String.

    # File lib/sprockets/digest_utils.rb, line 113
    def pack_base64digest(bin)
      [bin].pack('m0')
    end

pack_hexdigest(bin) click to toggle source

Internal: Pack a binary digest to a hex encoded string.

bin - String bytes

Returns hex String.

    # File lib/sprockets/digest_utils.rb, line 95
    def pack_hexdigest(bin)
      bin.unpack('H*').first
    end

pack_urlsafe_base64digest(bin) click to toggle source

Internal: Pack a binary digest to a urlsafe base64 encoded string.

bin - String bytes

Returns urlsafe base64 String.

    # File lib/sprockets/digest_utils.rb, line 122
    def pack_urlsafe_base64digest(bin)
      str = pack_base64digest(bin)
      str.tr!('+/'.freeze, '-_'.freeze)
      str.tr!('='.freeze, ''.freeze)
      str
    end

unpack_hexdigest(hex) click to toggle source

Internal: Unpack a hex encoded digest string into binary bytes.

hex - String hex

Returns binary String.

    # File lib/sprockets/digest_utils.rb, line 104
    def unpack_hexdigest(hex)
      [hex].pack('H*')
    end

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