* ext/digest: Prefix C constants with RUBY_ and C type names with

rb_ to avoid name clash in writing extensions.

* ext/digest: Introduce Digest::Class and Digest::Instance for
  ease of implementing subclasses and add-ons, inspried by
  gotoyuzo.

* ext/digest: The Digest::Instance module now requires and assumes
  that any instance be resettable and clonable, and add some
  convenient instance methods such as "new()", for creating a new
  copy, parameter taking "digest()" and "hexdigest()", for instant
  calculation.  These methods make digest instances work just like
  digest classes.

* ext/digest/sha2/lib/digest/sha2.rb:
  Add the Digest::SHA2 class to wrap up SHA2 variants: SHA256,
  SHA384 and SHA512, hoping this module would make a decent
  example of a digest subclass written in Ruby.

* ext/digest/lib/digest.rb: Adjust autoload entries for SHA2
  classes.

* ext/digest/lib/digest/hmac.rb: Follow the framework updates.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@11197 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/digest/sha2/lib/digest/sha2.rb

@@ -0,0 +1,73 @@
+#--
+# sha2.rb - defines Digest::SHA2 class which wraps up the SHA256,
+#           SHA384, and SHA512 classes.
+#++
+# Copyright (c) 2006 Akinori MUSHA <knu@iDaemons.org>
+#
+# All rights reserved.  You can redistribute and/or modify it under the same
+# terms as Ruby.
+#
+#   $Id$
+
+require 'digest'
+
+module Digest
+  #
+  # A meta digest provider class for SHA256, SHA384 and SHA512.
+  #
+  class SHA2 < Digest::Class
+    # call-seq:
+    #     Digest::SHA2.new(bitlen = 256) -> digest_obj
+    #
+    # Creates a new SHA2 hash object with a given bit length.
+    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
+
+    # :nodoc:
+    def reset
+      @sha2.reset
+      self
+    end
+
+    # :nodoc:
+    def update(str)
+      @sha2.update(str)
+      self
+    end
+    alias << update
+
+    def finish
+      @sha2.digest!
+    end
+    private :finish
+
+    def block_length
+      @sha2.block_length
+    end
+
+    def digest_length
+      @sha2.digest_length
+    end
+
+    # :nodoc:
+    def initialize_copy(other)
+      @sha2 = @sha2.clone
+    end
+
+    # :nodoc:
+    def inspect
+      "#<%s:%d %s>" % [self.class.name, @bitlen, hexdigest]
+    end
+  end
+end