5 files changed, 132 insertions, 28 deletions
diff --git a/ext/digest/lib/digest.rb b/ext/digest/lib/digest.rb
new file mode 100644
index 0000000000..e995adb450
--- /dev/null
+++ b/ext/digest/lib/digest.rb
@@ -0,0 +1,123 @@
+# frozen_string_literal: false
+
+if defined?(Digest) &&
+    /\A(?:2\.|3\.0\.[0-2]\z)/.match?(RUBY_VERSION) &&
+    caller_locations.any? { |l|
+      %r{/(rubygems/gem_runner|bundler/cli)\.rb}.match?(l.path)
+    }
+  # Before Ruby 3.0.3/3.1.0, the gem and bundle commands used to load
+  # the digest library before loading additionally installed gems, so
+  # you will get constant redefinition warnings and unexpected
+  # implementation overwriting if we proceed here.  Avoid that.
+  return
+end
+
+require 'digest/version'
+require 'digest/loader'
+
+module Digest
+  # A mutex for Digest().
+  REQUIRE_MUTEX = Thread::Mutex.new
+
+  def self.const_missing(name) # :nodoc:
+    case name
+    when :SHA256, :SHA384, :SHA512
+      lib = 'digest/sha2'
+    else
+      lib = File.join('digest', name.to_s.downcase)
+    end
+
+    begin
+      require lib
+    rescue LoadError
+      raise LoadError, "library not found for class Digest::#{name} -- #{lib}", caller(1)
+    end
+    unless Digest.const_defined?(name)
+      raise NameError, "uninitialized constant Digest::#{name}", caller(1)
+    end
+    Digest.const_get(name)
+  end
+
+  class ::Digest::Class
+    # Creates a digest object and reads a given file, _name_.
+    # Optional arguments are passed to the constructor of the digest
+    # class.
+    #
+    #   p Digest::SHA256.file("X11R6.8.2-src.tar.bz2").hexdigest
+    #   # => "f02e3c85572dc9ad7cb77c2a638e3be24cc1b5bea9fdbb0b0299c9668475c534"
+    def self.file(name, *args)
+      new(*args).file(name)
+    end
+
+    # Returns the base64 encoded hash value of a given _string_.  The
+    # return value is properly padded with '=' and contains no line
+    # feeds.
+    def self.base64digest(str, *args)
+      [digest(str, *args)].pack('m0')
+    end
+  end
+
+  module Instance
+    # Updates the digest with the contents of a given file _name_ and
+    # returns self.
+    def file(name)
+      File.open(name, "rb") {|f|
+        buf = ""
+        while f.read(16384, buf)
+          update buf
+        end
+      }
+      self
+    end
+
+    # If none is given, returns the resulting hash value of the digest
+    # in a base64 encoded form, keeping the digest's state.
+    #
+    # If a +string+ is given, returns the hash value for the given
+    # +string+ in a base64 encoded form, resetting the digest to the
+    # initial state before and after the process.
+    #
+    # In either case, the return value is properly padded with '=' and
+    # contains no line feeds.
+    def base64digest(str = nil)
+      [str ? digest(str) : digest].pack('m0')
+    end
+
+    # Returns the resulting hash value and resets the digest to the
+    # initial state.
+    def base64digest!
+      [digest!].pack('m0')
+    end
+  end
+end
+
+# call-seq:
+#   Digest(name) -> digest_subclass
+#
+# Returns a Digest subclass by +name+ in a thread-safe manner even
+# when on-demand loading is involved.
+#
+#   require 'digest'
+#
+#   Digest("MD5")
+#   # => Digest::MD5
+#
+#   Digest(:SHA256)
+#   # => Digest::SHA256
+#
+#   Digest(:Foo)
+#   # => LoadError: library not found for class Digest::Foo -- digest/foo
+def Digest(name)
+  const = name.to_sym
+  Digest::REQUIRE_MUTEX.synchronize {
+    # Ignore autoload's because it is void when we have #const_missing
+    Digest.const_missing(const)
+  }
+rescue LoadError
+  # Constants do not necessarily rely on digest/*.
+  if Digest.const_defined?(const)
+    Digest.const_get(const)
+  else
+    raise
+  end
+end
diff --git a/ext/digest/lib/digest/loader.rb b/ext/digest/lib/digest/loader.rb
new file mode 100644
index 0000000000..6b989e07be
--- /dev/null
+++ b/ext/digest/lib/digest/loader.rb
@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+require 'digest.so'
diff --git a/ext/digest/lib/digest/version.rb b/ext/digest/lib/digest/version.rb
new file mode 100644
index 0000000000..a56e80c54e
--- /dev/null
+++ b/ext/digest/lib/digest/version.rb
@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+module Digest
+  # The version string
+  VERSION = "3.2.1"
+end
diff --git a/ext/digest/lib/md5.rb b/ext/digest/lib/md5.rb
deleted file mode 100644
index 1d05d7d04e..0000000000
--- a/ext/digest/lib/md5.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-# just for compatibility; requiring "md5" is obsoleted
-#
-# $RoughId: md5.rb,v 1.4 2001/07/13 15:38:27 knu Exp $
-# $Id$
-
-require 'digest/md5'
-
-MD5 = Digest::MD5
-
-class MD5
-  def self.md5(*args)
-    new(*args)
-  end
-end
diff --git a/ext/digest/lib/sha1.rb b/ext/digest/lib/sha1.rb
deleted file mode 100644
index c4ac6f66ea..0000000000
--- a/ext/digest/lib/sha1.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-# just for compatibility; requiring "sha1" is obsoleted
-#
-# $RoughId: sha1.rb,v 1.4 2001/07/13 15:38:27 knu Exp $
-# $Id$
-
-require 'digest/sha1'
-
-SHA1 = Digest::SHA1
-
-class SHA1
-  def self.sha1(*args)
-    new(*args)
-  end
-end