5 files changed, 94 insertions, 58 deletions
diff --git a/ext/digest/lib/digest.rb b/ext/digest/lib/digest.rb
index 0c4ee3c2cc..e995adb450 100644
--- a/ext/digest/lib/digest.rb
+++ b/ext/digest/lib/digest.rb
@@ -1,17 +1,35 @@
-require 'digest.so'
+# 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
-  def self.const_missing(name)
+  # A mutex for Digest().
+  REQUIRE_MUTEX = Thread::Mutex.new
+
+  def self.const_missing(name) # :nodoc:
     case name
     when :SHA256, :SHA384, :SHA512
-      lib = 'digest/sha2.so'
+      lib = 'digest/sha2'
     else
       lib = File.join('digest', name.to_s.downcase)
     end
 
     begin
       require lib
-    rescue LoadError => e
+    rescue LoadError
       raise LoadError, "library not found for class Digest::#{name} -- #{lib}", caller(1)
     end
     unless Digest.const_defined?(name)
@@ -21,17 +39,26 @@ module Digest
   end
 
   class ::Digest::Class
-    # creates a digest object and reads a given file, _name_.
-    # 
-    #  p Digest::SHA256.file("X11R6.8.2-src.tar.bz2").hexdigest
-    #  # => "f02e3c85572dc9ad7cb77c2a638e3be24cc1b5bea9fdbb0b0299c9668475c534"
-    def self.file(name)
-      new.file(name)
+    # 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
+    # Updates the digest with the contents of a given file _name_ and
     # returns self.
     def file(name)
       File.open(name, "rb") {|f|
@@ -42,9 +69,55 @@ module Digest
       }
       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)
-  Digest.const_get(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 c399f2de1d..0000000000
--- a/ext/digest/lib/md5.rb
+++ /dev/null
@@ -1,23 +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'
-
-class MD5 < Digest::MD5
-  class << self
-    alias orig_new new
-    def new(str = nil)
-      if str
-        orig_new.update(str)
-      else
-        orig_new
-      end
-    end
-
-    def md5(*args)
-      new(*args)
-    end
-  end
-end
diff --git a/ext/digest/lib/sha1.rb b/ext/digest/lib/sha1.rb
deleted file mode 100644
index 4446e12e8d..0000000000
--- a/ext/digest/lib/sha1.rb
+++ /dev/null
@@ -1,23 +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'
-
-class SHA1 < Digest::SHA1
-  class << self
-    alias orig_new new
-    def new(str = nil)
-      if str
-        orig_new.update(str)
-      else
-        orig_new
-      end
-    end
-
-    def sha1(*args)
-      new(*args)
-    end
-  end
-end