* lib/rexml/encoding.rb: use Ruby native encoding mechnism. [ruby-dev:42464]

* lib/rexml/encodings/: remove.

* lib/rexml/document.rb, lib/rexml/formatters/default.rb,
  lib/rexml/output.rb, lib/rexml/parseexception.rb,
  lib/rexml/parsers/baseparser.rb, lib/rexml/source.rb,
  lib/rexml/xmldecl.rb: use Ruby's native Encoding object.

* test/rexml/, test/rss/: follow the above encoding chagnes.

* NEWS: add REXML's incompatible change about encoding.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29646 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

19 files changed, 78 insertions, 466 deletions

diff --git a/lib/rexml/document.rb b/lib/rexml/document.rb
index 0337553a2e..68a744d9e5 100644
--- a/lib/rexml/document.rb
+++ b/lib/rexml/document.rb
@@ -131,7 +131,8 @@ module REXML
       xml_decl().version
     end
 
-    # @return the XMLDecl encoding of this document as a String.
+    # @return the XMLDecl encoding of this document as an
+    # Encoding object.
     # If no XMLDecl has been set, returns the default encoding.
     def encoding
       xml_decl().encoding
@@ -183,7 +184,7 @@ module REXML
     #   that IE's limited abilities can handle.  This hack inserts a space
     #   before the /> on empty tags.  Defaults to false
     def write( output=$stdout, indent=-1, transitive=false, ie_hack=false )
-      if xml_decl.encoding != "UTF-8" && !output.kind_of?(Output)
+      if xml_decl.encoding != ::Encoding::UTF_8 && !output.kind_of?(Output)
         output = Output.new( output, xml_decl.encoding )
       end
       formatter = if indent > -1
diff --git a/lib/rexml/encoding.rb b/lib/rexml/encoding.rb
index 3feffb80f4..0c4a88fbeb 100644
--- a/lib/rexml/encoding.rb
+++ b/lib/rexml/encoding.rb
@@ -1,71 +1,67 @@
 # -*- mode: ruby; ruby-indent-level: 2; indent-tabs-mode: t; tab-width: 2 -*- vim: sw=2 ts=2
 module REXML
   module Encoding
-    @encoding_methods = {}
-    def self.register(enc, &block)
-      @encoding_methods[enc] = block
-    end
-    def self.apply(obj, enc)
-      @encoding_methods[enc][obj]
-    end
-    def self.encoding_method(enc)
-      @encoding_methods[enc]
-    end
-
-    # Native, default format is UTF-8, so it is declared here rather than in
-    # an encodings/ definition.
-    UTF_8 = 'UTF-8'
-    UTF_16 = 'UTF-16'
-    UNILE = 'UNILE'
-
-    # ID ---> Encoding name
-    attr_reader :encoding
-    def encoding=( enc )
-      old_verbosity = $VERBOSE
-      begin
-        $VERBOSE = false
-        enc = enc.nil? ? nil : enc.upcase
-        return false if defined? @encoding and enc == @encoding
-        if enc and enc != UTF_8
-          @encoding = enc
-          raise ArgumentError, "Bad encoding name #@encoding" unless @encoding =~ /^[\w-]+$/
-          @encoding.untaint
-          begin
-            require 'rexml/encodings/ICONV.rb'
-            Encoding.apply(self, "ICONV")
-          rescue LoadError, Exception
-            begin
-              enc_file = File.join( "rexml", "encodings", "#@encoding.rb" )
-              require enc_file
-              Encoding.apply(self, @encoding)
-            rescue LoadError => err
-              puts err.message
-              raise ArgumentError, "No decoder found for encoding #@encoding.  Please install iconv."
-            end
-          end
-        else
-          @encoding = UTF_8
-          require 'rexml/encodings/UTF-8.rb'
-          Encoding.apply(self, @encoding)
-        end
-      ensure
-        $VERBOSE = old_verbosity
+    # ID ---> Encoding object
+		attr_reader :encoding
+    def encoding=(encoding)
+			if encoding.is_a?(String)
+				original_encoding = encoding
+				encoding = find_encoding(encoding)
+				unless encoding
+					raise ArgumentError, "Bad encoding name #{original_encoding}"
+				end
+			end
+			return false if defined?(@encoding) and encoding == @encoding
+			if encoding and encoding != ::Encoding::UTF_8
+				@encoding = encoding
+			else
+				@encoding = ::Encoding::UTF_8
       end
       true
     end
 
-    def check_encoding str
+    def check_encoding(xml)
       # We have to recognize UTF-16, LSB UTF-16, and UTF-8
-      if str[0,2] == "\xfe\xff"
-        str[0,2] = ""
-        return UTF_16
-      elsif str[0,2] == "\xff\xfe"
-        str[0,2] = ""
-        return UNILE
-      end
-      str =~ /^\s*<\?xml\s+version\s*=\s*(['"]).*?\1\s+encoding\s*=\s*(["'])(.*?)\2/m
-      return $3.upcase if $3
-      return UTF_8
+      if xml[0, 2] == "\xfe\xff"
+        xml[0, 2] = ""
+				::Encoding::UTF_16BE
+      elsif xml[0, 2] == "\xff\xfe"
+        xml[0, 2] = ""
+				::Encoding::UTF_16LE
+			else
+				if /\A\s*<\?xml\s+version\s*=\s*(['"]).*?\1
+            \s+encoding\s*=\s*(["'])(.*?)\2/mx =~ xml
+					encoding_name = $3
+					if /\Autf-16\z/i =~ encoding_name
+						::Encoding::UTF_16BE
+					else
+						find_encoding(encoding_name)
+					end
+				else
+					::Encoding::UTF_8
+				end
+			end
     end
+
+		def encode(string)
+			string.encode(@encoding)
+		end
+
+		def decode(string)
+			string.encode(::Encoding::UTF_8, @encoding)
+		end
+
+		private
+		def find_encoding(name)
+			case name
+			when "UTF-16"
+				name = "UTF-16BE"
+			when /\Ashift-jis\z/i
+				name = "Shift_JIS"
+			when /\ACP-(\d+)\z/
+				name = "CP#{$1}"
+			end
+			::Encoding.find(name)
+		end
   end
 end
diff --git a/lib/rexml/encodings/CP-1252.rb b/lib/rexml/encodings/CP-1252.rb
deleted file mode 100644
index 587c5bdd68..0000000000
--- a/lib/rexml/encodings/CP-1252.rb
+++ /dev/null
@@ -1,103 +0,0 @@
-#
-# This class was contributed by Mikko Tiihonen mikko DOT tiihonen AT hut DOT fi
-#
-module REXML
-  module Encoding
-    register( "CP-1252" ) do |o|
-      class << o
-        alias encode encode_cp1252
-      alias decode decode_cp1252
-      end
-    end
-
-    # Convert from UTF-8
-    def encode_cp1252(content)
-      array_utf8 = content.unpack('U*')
-      array_enc = []
-      array_utf8.each do |num|
-        case num
-          # shortcut first bunch basic characters
-        when 0..0xFF; array_enc << num
-          # characters added compared to iso-8859-1
-        when 0x20AC; array_enc << 0x80 # 0xe2 0x82 0xac
-        when 0x201A; array_enc << 0x82 # 0xe2 0x82 0x9a
-        when 0x0192; array_enc << 0x83 # 0xc6 0x92
-        when 0x201E; array_enc << 0x84 # 0xe2 0x82 0x9e
-        when 0x2026; array_enc << 0x85 # 0xe2 0x80 0xa6
-        when 0x2020; array_enc << 0x86 # 0xe2 0x80 0xa0
-        when 0x2021; array_enc << 0x87 # 0xe2 0x80 0xa1
-        when 0x02C6; array_enc << 0x88 # 0xcb 0x86
-        when 0x2030; array_enc << 0x89 # 0xe2 0x80 0xb0
-        when 0x0160; array_enc << 0x8A # 0xc5 0xa0
-        when 0x2039; array_enc << 0x8B # 0xe2 0x80 0xb9
-        when 0x0152; array_enc << 0x8C # 0xc5 0x92
-        when 0x017D; array_enc << 0x8E # 0xc5 0xbd
-        when 0x2018; array_enc << 0x91 # 0xe2 0x80 0x98
-        when 0x2019; array_enc << 0x92 # 0xe2 0x80 0x99
-        when 0x201C; array_enc << 0x93 # 0xe2 0x80 0x9c
-        when 0x201D; array_enc << 0x94 # 0xe2 0x80 0x9d
-        when 0x2022; array_enc << 0x95 # 0xe2 0x80 0xa2
-        when 0x2013; array_enc << 0x96 # 0xe2 0x80 0x93
-        when 0x2014; array_enc << 0x97 # 0xe2 0x80 0x94
-        when 0x02DC; array_enc << 0x98 # 0xcb 0x9c
-        when 0x2122; array_enc << 0x99 # 0xe2 0x84 0xa2
-        when 0x0161; array_enc << 0x9A # 0xc5 0xa1
-        when 0x203A; array_enc << 0x9B # 0xe2 0x80 0xba
-        when 0x0152; array_enc << 0x9C # 0xc5 0x93
-        when 0x017E; array_enc << 0x9E # 0xc5 0xbe
-        when 0x0178; array_enc << 0x9F # 0xc5 0xb8
-        else
-          # all remaining basic characters can be used directly
-          if num <= 0xFF
-            array_enc << num
-          else
-            # Numeric entity (&#nnnn;); shard by  Stefan Scholl
-            array_enc.concat "&\##{num};".unpack('C*')
-          end
-        end
-      end
-      array_enc.pack('C*')
-    end
-
-    # Convert to UTF-8
-    def decode_cp1252(str)
-      array_latin9 = str.unpack('C*')
-      array_enc = []
-      array_latin9.each do |num|
-        case num
-          # characters that added compared to iso-8859-1
-        when 0x80; array_enc << 0x20AC # 0xe2 0x82 0xac
-        when 0x82; array_enc << 0x201A # 0xe2 0x82 0x9a
-        when 0x83; array_enc << 0x0192 # 0xc6 0x92
-        when 0x84; array_enc << 0x201E # 0xe2 0x82 0x9e
-        when 0x85; array_enc << 0x2026 # 0xe2 0x80 0xa6
-        when 0x86; array_enc << 0x2020 # 0xe2 0x80 0xa0
-        when 0x87; array_enc << 0x2021 # 0xe2 0x80 0xa1
-        when 0x88; array_enc << 0x02C6 # 0xcb 0x86
-        when 0x89; array_enc << 0x2030 # 0xe2 0x80 0xb0
-        when 0x8A; array_enc << 0x0160 # 0xc5 0xa0
-        when 0x8B; array_enc << 0x2039 # 0xe2 0x80 0xb9
-        when 0x8C; array_enc << 0x0152 # 0xc5 0x92
-        when 0x8E; array_enc << 0x017D # 0xc5 0xbd
-        when 0x91; array_enc << 0x2018 # 0xe2 0x80 0x98
-        when 0x92; array_enc << 0x2019 # 0xe2 0x80 0x99
-        when 0x93; array_enc << 0x201C # 0xe2 0x80 0x9c
-        when 0x94; array_enc << 0x201D # 0xe2 0x80 0x9d
-        when 0x95; array_enc << 0x2022 # 0xe2 0x80 0xa2
-        when 0x96; array_enc << 0x2013 # 0xe2 0x80 0x93
-        when 0x97; array_enc << 0x2014 # 0xe2 0x80 0x94
-        when 0x98; array_enc << 0x02DC # 0xcb 0x9c
-        when 0x99; array_enc << 0x2122 # 0xe2 0x84 0xa2
-        when 0x9A; array_enc << 0x0161 # 0xc5 0xa1
-        when 0x9B; array_enc << 0x203A # 0xe2 0x80 0xba
-        when 0x9C; array_enc << 0x0152 # 0xc5 0x93
-        when 0x9E; array_enc << 0x017E # 0xc5 0xbe
-        when 0x9F; array_enc << 0x0178 # 0xc5 0xb8
-        else
-          array_enc << num
-        end
-      end
-      array_enc.pack('U*')
-    end
-  end
-end
diff --git a/lib/rexml/encodings/EUC-JP.rb b/lib/rexml/encodings/EUC-JP.rb
deleted file mode 100644
index db37b6bf0d..0000000000
--- a/lib/rexml/encodings/EUC-JP.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-module REXML
-  module Encoding
-    begin
-      require 'uconv'
-
-      def decode_eucjp(str)
-        Uconv::euctou8(str)
-      end
-
-      def encode_eucjp content
-        Uconv::u8toeuc(content)
-      end
-    rescue LoadError
-      require 'nkf'
-
-      EUCTOU8 = '-Ewm0'
-      U8TOEUC = '-Wem0'
-
-      def decode_eucjp(str)
-        NKF.nkf(EUCTOU8, str)
-      end
-
-      def encode_eucjp content
-        NKF.nkf(U8TOEUC, content)
-      end
-    end
-
-    register("EUC-JP") do |obj|
-      class << obj
-        alias decode decode_eucjp
-        alias encode encode_eucjp
-      end
-    end
-  end
-end
diff --git a/lib/rexml/encodings/ICONV.rb b/lib/rexml/encodings/ICONV.rb
deleted file mode 100644
index 172fba7cd1..0000000000
--- a/lib/rexml/encodings/ICONV.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-require "iconv"
-raise LoadError unless defined? Iconv
-
-module REXML
-  module Encoding
-    def decode_iconv(str)
-      Iconv.conv(UTF_8, @encoding, str)
-    end
-
-    def encode_iconv(content)
-      Iconv.conv(@encoding, UTF_8, content)
-    end
-
-    register("ICONV") do |obj|
-      Iconv.conv(UTF_8, obj.encoding, nil)
-      class << obj
-        alias decode decode_iconv
-        alias encode encode_iconv
-      end
-    end
-  end
-end
diff --git a/lib/rexml/encodings/ISO-8859-1.rb b/lib/rexml/encodings/ISO-8859-1.rb
deleted file mode 100644
index 2873d13bf0..0000000000
--- a/lib/rexml/encodings/ISO-8859-1.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require 'rexml/encodings/US-ASCII'
-
-module REXML
-  module Encoding
-    register("ISO-8859-1", &encoding_method("US-ASCII"))
-  end
-end
diff --git a/lib/rexml/encodings/ISO-8859-15.rb b/lib/rexml/encodings/ISO-8859-15.rb
deleted file mode 100644
index 08a19cb755..0000000000
--- a/lib/rexml/encodings/ISO-8859-15.rb
+++ /dev/null
@@ -1,72 +0,0 @@
-#
-# This class was contributed by Mikko Tiihonen mikko DOT tiihonen AT hut DOT fi
-#
-module REXML
-  module Encoding
-    register("ISO-8859-15") do |o|
-      alias encode to_iso_8859_15
-      alias decode from_iso_8859_15
-    end
-
-    # Convert from UTF-8
-    def to_iso_8859_15(content)
-      array_utf8 = content.unpack('U*')
-      array_enc = []
-      array_utf8.each do |num|
-        case num
-          # shortcut first bunch basic characters
-        when 0..0xA3; array_enc << num
-          # characters removed compared to iso-8859-1
-        when 0xA4; array_enc << '&#164;'
-        when 0xA6; array_enc << '&#166;'
-        when 0xA8; array_enc << '&#168;'
-        when 0xB4; array_enc << '&#180;'
-        when 0xB8; array_enc << '&#184;'
-        when 0xBC; array_enc << '&#188;'
-        when 0xBD; array_enc << '&#189;'
-        when 0xBE; array_enc << '&#190;'
-          # characters added compared to iso-8859-1
-        when 0x20AC; array_enc << 0xA4 # 0xe2 0x82 0xac
-        when 0x0160; array_enc << 0xA6 # 0xc5 0xa0
-        when 0x0161; array_enc << 0xA8 # 0xc5 0xa1
-        when 0x017D; array_enc << 0xB4 # 0xc5 0xbd
-        when 0x017E; array_enc << 0xB8 # 0xc5 0xbe
-        when 0x0152; array_enc << 0xBC # 0xc5 0x92
-        when 0x0153; array_enc << 0xBD # 0xc5 0x93
-        when 0x0178; array_enc << 0xBE # 0xc5 0xb8
-        else
-          # all remaining basic characters can be used directly
-          if num <= 0xFF
-            array_enc << num
-          else
-            # Numeric entity (&#nnnn;); shard by  Stefan Scholl
-            array_enc.concat "&\##{num};".unpack('C*')
-          end
-        end
-      end
-      array_enc.pack('C*')
-    end
-
-    # Convert to UTF-8
-    def from_iso_8859_15(str)
-      array_latin9 = str.unpack('C*')
-      array_enc = []
-      array_latin9.each do |num|
-        case num
-          # characters that differ compared to iso-8859-1
-        when 0xA4; array_enc << 0x20AC
-        when 0xA6; array_enc << 0x0160
-        when 0xA8; array_enc << 0x0161
-        when 0xB4; array_enc << 0x017D
-        when 0xB8; array_enc << 0x017E
-        when 0xBC; array_enc << 0x0152
-        when 0xBD; array_enc << 0x0153
-        when 0xBE; array_enc << 0x0178
-        else
-          array_enc << num
-        end
-      end
-      array_enc.pack('U*')
-    end
-  end
-end
diff --git a/lib/rexml/encodings/SHIFT-JIS.rb b/lib/rexml/encodings/SHIFT-JIS.rb
deleted file mode 100644
index 9e0f4af20e..0000000000
--- a/lib/rexml/encodings/SHIFT-JIS.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-module REXML
-  module Encoding
-    begin
-      require 'uconv'
-
-      def decode_sjis content
-        Uconv::sjistou8(content)
-      end
-
-      def encode_sjis(str)
-        Uconv::u8tosjis(str)
-      end
-    rescue LoadError
-      require 'nkf'
-
-      SJISTOU8 = '-Swm0x'
-      U8TOSJIS = '-Wsm0x'
-
-      def decode_sjis(str)
-        NKF.nkf(SJISTOU8, str)
-      end
-
-      def encode_sjis content
-        NKF.nkf(U8TOSJIS, content)
-      end
-    end
-
-    b = proc do |obj|
-      class << obj
-        alias decode decode_sjis
-        alias encode encode_sjis
-      end
-    end
-    register("SHIFT-JIS", &b)
-    register("SHIFT_JIS", &b)
-  end
-end
diff --git a/lib/rexml/encodings/SHIFT_JIS.rb b/lib/rexml/encodings/SHIFT_JIS.rb
deleted file mode 100644
index e355704a7c..0000000000
--- a/lib/rexml/encodings/SHIFT_JIS.rb
+++ /dev/null
@@ -1 +0,0 @@
-require 'rexml/encodings/SHIFT-JIS'
diff --git a/lib/rexml/encodings/UNILE.rb b/lib/rexml/encodings/UNILE.rb
deleted file mode 100644
index 1a18f0c932..0000000000
--- a/lib/rexml/encodings/UNILE.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-module REXML
-  module Encoding
-    def encode_unile content
-      array_utf8 = content.unpack("U*")
-      array_enc = []
-      array_utf8.each do |num|
-        if ((num>>16) > 0)
-          array_enc << ??
-          array_enc << 0
-        else
-          array_enc << (num & 0xFF)
-          array_enc << (num >> 8)
-        end
-      end
-      array_enc.pack('C*')
-    end
-
-    def decode_unile(str)
-      array_enc=str.unpack('C*')
-      array_utf8 = []
-      0.step(array_enc.size-1, 2){|i|
-        array_utf8 << (array_enc.at(i) + array_enc.at(i+1)*0x100)
-      }
-      array_utf8.pack('U*')
-    end
-
-    register(UNILE) do |obj|
-      class << obj
-        alias decode decode_unile
-        alias encode encode_unile
-      end
-    end
-  end
-end
diff --git a/lib/rexml/encodings/US-ASCII.rb b/lib/rexml/encodings/US-ASCII.rb
deleted file mode 100644
index fb4c217074..0000000000
--- a/lib/rexml/encodings/US-ASCII.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-module REXML
-  module Encoding
-    # Convert from UTF-8
-    def encode_ascii content
-      array_utf8 = content.unpack('U*')
-      array_enc = []
-      array_utf8.each do |num|
-        if num <= 0x7F
-          array_enc << num
-        else
-          # Numeric entity (&#nnnn;); shard by  Stefan Scholl
-          array_enc.concat "&\##{num};".unpack('C*')
-        end
-      end
-      array_enc.pack('C*')
-    end
-
-    # Convert to UTF-8
-    def decode_ascii(str)
-      str.unpack('C*').pack('U*')
-    end
-
-    register("US-ASCII") do |obj|
-      class << obj
-        alias decode decode_ascii
-        alias encode encode_ascii
-      end
-    end
-  end
-end
diff --git a/lib/rexml/encodings/UTF-16.rb b/lib/rexml/encodings/UTF-16.rb
deleted file mode 100644
index 2ec058eed5..0000000000
--- a/lib/rexml/encodings/UTF-16.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-module REXML
-  module Encoding
-    def encode_utf16 content
-      array_utf8 = content.unpack("U*")
-      array_enc = []
-      array_utf8.each do |num|
-        if ((num>>16) > 0)
-          array_enc << 0
-          array_enc << ??
-        else
-          array_enc << (num >> 8)
-          array_enc << (num & 0xFF)
-        end
-      end
-      array_enc.pack('C*')
-    end
-
-    def decode_utf16(str)
-      str = str[2..-1] if /^\376\377/n =~ str
-      array_enc=str.unpack('C*')
-      array_utf8 = []
-      0.step(array_enc.size-1, 2){|i|
-        array_utf8 << (array_enc.at(i+1) + array_enc.at(i)*0x100)
-      }
-      array_utf8.pack('U*')
-    end
-
-    register(UTF_16) do |obj|
-      class << obj
-        alias decode decode_utf16
-        alias encode encode_utf16
-      end
-    end
-  end
-end
diff --git a/lib/rexml/encodings/UTF-8.rb b/lib/rexml/encodings/UTF-8.rb
deleted file mode 100644
index bb08f44100..0000000000
--- a/lib/rexml/encodings/UTF-8.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-module REXML
-  module Encoding
-    def encode_utf8 content
-      content
-    end
-
-    def decode_utf8(str)
-      str
-    end
-
-    register(UTF_8) do |obj|
-      class << obj
-        alias decode decode_utf8
-        alias encode encode_utf8
-      end
-    end
-  end
-end
diff --git a/lib/rexml/formatters/default.rb b/lib/rexml/formatters/default.rb
index db44453e1e..ec4149047d 100644
--- a/lib/rexml/formatters/default.rb
+++ b/lib/rexml/formatters/default.rb
@@ -22,7 +22,7 @@ module REXML
         case node
 
         when Document
-          if node.xml_decl.encoding != "UTF-8" && !output.kind_of?(Output)
+          if node.xml_decl.encoding != ::Encoding::UTF_8 && !output.kind_of?(Output)
             output = Output.new( output, node.xml_decl.encoding )
           end
           write_document( node, output )
diff --git a/lib/rexml/output.rb b/lib/rexml/output.rb
index b7f17b9dff..752f6e1d40 100644
--- a/lib/rexml/output.rb
+++ b/lib/rexml/output.rb
@@ -10,7 +10,7 @@ module REXML
       @output = real_IO
       self.encoding = encd
 
-      @to_utf = encd == UTF_8 ? false : true
+      @to_utf = (@encoding != ::Encoding::UTF_8)
     end
 
     def <<( content )
diff --git a/lib/rexml/parseexception.rb b/lib/rexml/parseexception.rb
index 0481f72818..0c4d55abda 100644
--- a/lib/rexml/parseexception.rb
+++ b/lib/rexml/parseexception.rb
@@ -28,7 +28,7 @@ module REXML
         err << "\nLine: #{line}\n"
         err << "Position: #{position}\n"
         err << "Last 80 unconsumed characters:\n"
-        err << @source.buffer[0..80].gsub(/\n/, ' ')
+        err << @source.buffer[0..80].force_encoding("ASCII-8BIT").gsub(/\n/, ' ')
       end
 
       err
diff --git a/lib/rexml/parsers/baseparser.rb b/lib/rexml/parsers/baseparser.rb
index ade35d7921..ee8b160ce5 100644
--- a/lib/rexml/parsers/baseparser.rb
+++ b/lib/rexml/parsers/baseparser.rb
@@ -248,10 +248,8 @@ module REXML
             @document_status = :after_doctype
             @source.read if @source.buffer.size<2
             md = @source.match(/\s*/um, true)
-            if @source.encoding == "UTF-8"
-              if @source.buffer.respond_to? :force_encoding
-                @source.buffer.force_encoding(Encoding::UTF_8)
-              end
+            if @source.encoding == ::Encoding::UTF_8
+              @source.buffer.force_encoding(::Encoding::UTF_8)
             end
           end
         end
diff --git a/lib/rexml/source.rb b/lib/rexml/source.rb
index 1206150b16..227b0c56c4 100644
--- a/lib/rexml/source.rb
+++ b/lib/rexml/source.rb
@@ -54,13 +54,13 @@ module REXML
     def encoding=(enc)
       return unless super
       @line_break = encode( '>' )
-      if enc != UTF_8
+      if @encoding != ::Encoding::UTF_8
         @buffer = decode(@buffer)
         @to_utf = true
       else
         @to_utf = false
         if @buffer.respond_to? :force_encoding
-          @buffer.force_encoding Encoding::UTF_8
+          @buffer.force_encoding ::Encoding::UTF_8
         end
       end
     end
diff --git a/lib/rexml/xmldecl.rb b/lib/rexml/xmldecl.rb
index 361e4b7106..81d3057732 100644
--- a/lib/rexml/xmldecl.rb
+++ b/lib/rexml/xmldecl.rb
@@ -109,9 +109,20 @@ module REXML
     end
 
     private
+    def normalized_encoding_name(_encoding)
+      if _encoding == ::Encoding::UTF_16BE
+        "UTF-16"
+      else
+        return _encoding.name
+      end
+    end
+
     def content(enc)
       rv = "version='#@version'"
-      rv << " encoding='#{enc}'" if @writeencoding || enc !~ /utf-8/i
+      if @writeencoding || enc.to_s !~ /\Autf-8\z/i
+        encoding_name = normalized_encoding_name(enc)
+        rv << " encoding='#{encoding_name}'"
+      end
       rv << " standalone='#@standalone'" if @standalone
       rv
     end