diff --git a/lib/rexml/parsers/baseparser.rb b/lib/rexml/parsers/baseparser.rb
index 595669c..68684f1 100644
--- a/lib/rexml/parsers/baseparser.rb
+++ b/lib/rexml/parsers/baseparser.rb
@@ -48,29 +48,15 @@ class BaseParser
       REFERENCE = "&(?:#{NAME};|#\\d+;|#x[0-9a-fA-F]+;)"
       REFERENCE_RE = /#{REFERENCE}/
 
-      DOCTYPE_START = /\A\s*<!DOCTYPE\s/um
-      DOCTYPE_END = /\A\s*\]\s*>/um
       ATTRIBUTE_PATTERN = /\s*(#{QNAME_STR})\s*=\s*(["'])(.*?)\4/um
-      COMMENT_START = /\A<!--/u
-      COMMENT_PATTERN = /<!--(.*?)-->/um
-      CDATA_START = /\A<!\[CDATA\[/u
-      CDATA_END = /\A\s*\]\s*>/um
-      CDATA_PATTERN = /<!\[CDATA\[(.*?)\]\]>/um
-      XMLDECL_START = /\A<\?xml\s/u;
-      XMLDECL_PATTERN = /<\?xml\s+(.*?)\?>/um
-      INSTRUCTION_START = /\A<\?/u
-      INSTRUCTION_PATTERN = /<\?#{NAME}(\s+.*?)?\?>/um
-      TAG_MATCH = /\A<((?>#{QNAME_STR}))/um
-      CLOSE_MATCH = /\A\s*<\/(#{QNAME_STR})\s*>/um
+      INSTRUCTION_PATTERN = /#{NAME}(\s+.*?)?\?>/um
+      TAG_MATCH = /((?>#{QNAME_STR}))/um
+      CLOSE_MATCH = /(#{QNAME_STR})\s*>/um
 
       VERSION = /\bversion\s*=\s*["'](.*?)['"]/um
       ENCODING = /\bencoding\s*=\s*["'](.*?)['"]/um
       STANDALONE = /\bstandalone\s*=\s*["'](.*?)['"]/um
 
-      ENTITY_START = /\A\s*<!ENTITY/
-      ELEMENTDECL_START = /\A\s*<!ELEMENT/um
-      ELEMENTDECL_PATTERN = /\A\s*(<!ELEMENT.*?)>/um
-      SYSTEMENTITY = /\A\s*(%.*?;)\s*$/um
       ENUMERATION = "\\(\\s*#{NMTOKEN}(?:\\s*\\|\\s*#{NMTOKEN})*\\s*\\)"
       NOTATIONTYPE = "NOTATION\\s+\\(\\s*#{NAME}(?:\\s*\\|\\s*#{NAME})*\\s*\\)"
       ENUMERATEDTYPE = "(?:(?:#{NOTATIONTYPE})|(?:#{ENUMERATION}))"
@@ -79,10 +65,7 @@ class BaseParser
       DEFAULTDECL = "(#REQUIRED|#IMPLIED|(?:(#FIXED\\s+)?#{ATTVALUE}))"
       ATTDEF = "\\s+#{NAME}\\s+#{ATTTYPE}\\s+#{DEFAULTDECL}"
       ATTDEF_RE = /#{ATTDEF}/
-      ATTLISTDECL_START = /\A\s*<!ATTLIST/um
-      ATTLISTDECL_PATTERN = /\A\s*<!ATTLIST\s+#{NAME}(?:#{ATTDEF})*\s*>/um
-
-      TEXT_PATTERN = /\A([^<]*)/um
+      ATTLISTDECL_PATTERN = /\s+#{NAME}(?:#{ATTDEF})*\s*>/um
 
       # Entity constants
       PUBIDCHAR = "\x20\x0D\x0Aa-zA-Z0-9\\-()+,./:=?;!*@$_%#"
@@ -94,11 +77,10 @@ class BaseParser
       ENTITYVALUE = %Q{((?:"(?:[^%&"]|#{PEREFERENCE}|#{REFERENCE})*")|(?:'([^%&']|#{PEREFERENCE}|#{REFERENCE})*'))}
       PEDEF = "(?:#{ENTITYVALUE}|#{EXTERNALID})"
       ENTITYDEF = "(?:#{ENTITYVALUE}|(?:#{EXTERNALID}(#{NDATADECL})?))"
-      PEDECL = "<!ENTITY\\s+(%)\\s+#{NAME}\\s+#{PEDEF}\\s*>"
-      GEDECL = "<!ENTITY\\s+#{NAME}\\s+#{ENTITYDEF}\\s*>"
-      ENTITYDECL = /\s*(?:#{GEDECL})|\s*(?:#{PEDECL})/um
+      PEDECL = "\\s+(%)\\s+#{NAME}\\s+#{PEDEF}\\s*>"
+      GEDECL = "\\s+#{NAME}\\s+#{ENTITYDEF}\\s*>"
+      ENTITYDECL = /(?:#{GEDECL})|(?:#{PEDECL})/um
 
-      NOTATIONDECL_START = /\A\s*<!NOTATION/um
       EXTERNAL_ID_PUBLIC = /\A\s*PUBLIC\s+#{PUBIDLITERAL}\s+#{SYSTEMLITERAL}\s*/um
       EXTERNAL_ID_SYSTEM = /\A\s*SYSTEM\s+#{SYSTEMLITERAL}\s*/um
       PUBLIC_ID = /\A\s*PUBLIC\s+#{PUBIDLITERAL}\s*/um
@@ -112,6 +94,15 @@ class BaseParser
         "apos" => [/&apos;/, "&apos;", "'", /'/]
       }
 
+      QUESTION_MARK_TAG_START = "<?"
+      EXCLAMATION_MARK_TAG_START = "<!"
+      TAG_START = "<"
+      TAG_END = ">"
+      SLASH = "/"
+      EXCLAMATION_MARK = "!"
+      QUESTION_MARK = "?"
+      DOUBLE_DASH = "--"
+
       def initialize( source )
         self.stream = source
         @listeners = []
@@ -198,65 +189,67 @@ def pull_event
         #STDERR.puts @source.encoding
         #STDERR.puts "BUFFER = #{@source.buffer.inspect}"
         if @document_status == nil
-          word = @source.match( /\A((?:\s+)|(?:<[^>]*>))/um )
-          word = word[1] unless word.nil?
-          #STDERR.puts "WORD = #{word.inspect}"
-          case word
-          when COMMENT_START
-            return [ :comment, @source.match( COMMENT_PATTERN, true )[1] ]
-          when XMLDECL_START
-            #STDERR.puts "XMLDECL"
-            results = @source.match( XMLDECL_PATTERN, true )[1]
-            version = VERSION.match( results )
-            version = version[1] unless version.nil?
-            encoding = ENCODING.match(results)
-            encoding = encoding[1] unless encoding.nil?
-            if need_source_encoding_update?(encoding)
-              @source.encoding = encoding
-            end
-            if encoding.nil? and /\AUTF-16(?:BE|LE)\z/i =~ @source.encoding
-              encoding = "UTF-16"
-            end
-            standalone = STANDALONE.match(results)
-            standalone = standalone[1] unless standalone.nil?
-            return [ :xmldecl, version, encoding, standalone ]
-          when INSTRUCTION_START
-            return process_instruction
-          when DOCTYPE_START
-            base_error_message = "Malformed DOCTYPE"
-            @source.match(DOCTYPE_START, true)
-            @nsstack.unshift(curr_ns=Set.new)
-            name = parse_name(base_error_message)
-            if @source.match(/\A\s*\[/um, true)
-              id = [nil, nil, nil]
-              @document_status = :in_doctype
-            elsif @source.match(/\A\s*>/um, true)
-              id = [nil, nil, nil]
-              @document_status = :after_doctype
-            else
-              id = parse_id(base_error_message,
-                            accept_external_id: true,
-                            accept_public_id: false)
-              if id[0] == "SYSTEM"
-                # For backward compatibility
-                id[1], id[2] = id[2], nil
+          @source.read
+          if @source.match(QUESTION_MARK_TAG_START, true, false)
+            if results = @source.match(/xml\s+(.*?)\?>/um, true, false)
+              results = results[1]
+              version = VERSION.match( results )
+              version = version[1] unless version.nil?
+              encoding = ENCODING.match(results)
+              encoding = encoding[1] unless encoding.nil?
+              if need_source_encoding_update?(encoding)
+                @source.encoding = encoding
+              end
+              if encoding.nil? and /\AUTF-16(?:BE|LE)\z/i =~ @source.encoding
+                encoding = "UTF-16"
               end
-              if @source.match(/\A\s*\[/um, true)
+              standalone = STANDALONE.match(results)
+              standalone = standalone[1] unless standalone.nil?
+              return [ :xmldecl, version, encoding, standalone ]
+            else # instruction
+              return process_instruction
+            end
+          elsif @source.match(EXCLAMATION_MARK_TAG_START, true, false)
+            if @source.match(DOUBLE_DASH, true, false)
+              return [ :comment, @source.match( /(.*?)-->/um, true )[1] ]
+            elsif @source.match(/DOCTYPE\s/um, true, false)
+              base_error_message = "Malformed DOCTYPE"
+              @nsstack.unshift(curr_ns=Set.new)
+              name = parse_name(base_error_message)
+              if @source.match(/\s*\[/um, true)
+                id = [nil, nil, nil]
                 @document_status = :in_doctype
-              elsif @source.match(/\A\s*>/um, true)
+              elsif @source.match(/\s*>/um, true)
+                id = [nil, nil, nil]
                 @document_status = :after_doctype
               else
-                message = "#{base_error_message}: garbage after external ID"
-                raise REXML::ParseException.new(message, @source)
+                id = parse_id(base_error_message,
+                              accept_external_id: true,
+                              accept_public_id: false)
+                if id[0] == "SYSTEM"
+                  # For backward compatibility
+                  id[1], id[2] = id[2], nil
+                end
+                if @source.match(/\s*\[/um, true)
+                  @document_status = :in_doctype
+                elsif @source.match(/\s*>/um, true)
+                  @document_status = :after_doctype
+                else
+                  message = "#{base_error_message}: garbage after external ID"
+                  raise REXML::ParseException.new(message, @source)
+                end
               end
+              args = [:start_doctype, name, *id]
+              if @document_status == :after_doctype
+                @source.match(/\s*/um, true)
+                @stack << [ :end_doctype ]
+              end
+              return args
+            else
+              message = "Invalid XML"
+              raise REXML::ParseException.new(message, @source)
             end
-            args = [:start_doctype, name, *id]
-            if @document_status == :after_doctype
-              @source.match(/\A\s*/um, true)
-              @stack << [ :end_doctype ]
-            end
-            return args
-          when /\A\s+/
+          elsif @source.match( /\s+/, false, false )
           else
             @document_status = :after_doctype
             if @source.encoding == "UTF-8"
@@ -265,16 +258,13 @@ def pull_event
           end
         end
         if @document_status == :in_doctype
-          md = @source.match(/\A\s*(.*?>)/um)
-          case md[1]
-          when SYSTEMENTITY
-            match = @source.match( SYSTEMENTITY, true )[1]
-            return [ :externalentity, match ]
-
-          when ELEMENTDECL_START
-            return [ :elementdecl, @source.match( ELEMENTDECL_PATTERN, true )[1] ]
-
-          when ENTITY_START
+          @source.read
+          @source.match(/\s*/um, true, false) # skip spaces
+          if match = @source.match( /(%.*?;)\s*$/um, true, false)
+            return [ :externalentity, match[1] ]
+          elsif match = @source.match(/(<!ELEMENT.*?)>/um, true, false)
+            return [ :elementdecl, match[1] ]
+          elsif @source.match( /<!ENTITY/, true, false)
             match = [:entitydecl, *@source.match( ENTITYDECL, true ).captures.compact]
             ref = false
             if match[1] == '%'
@@ -300,7 +290,7 @@ def pull_event
             end
             match << '%' if ref
             return match
-          when ATTLISTDECL_START
+          elsif @source.match( /<!ATTLIST/um, true, false)
             md = @source.match( ATTLISTDECL_PATTERN, true )
             raise REXML::ParseException.new( "Bad ATTLIST declaration!", @source ) if md.nil?
             element = md[1]
@@ -320,42 +310,41 @@ def pull_event
               end
             end
             return [ :attlistdecl, element, pairs, contents ]
-          when NOTATIONDECL_START
+          elsif @source.match( /<!NOTATION/um, true, false)
             base_error_message = "Malformed notation declaration"
-            unless @source.match(/\A\s*<!NOTATION\s+/um, true)
-              if @source.match(/\A\s*<!NOTATION\s*>/um)
+            unless @source.match(/\s+/um, true)
+              if @source.match(/\s*>/um)
                 message = "#{base_error_message}: name is missing"
               else
                 message = "#{base_error_message}: invalid declaration name"
               end
+              @source.string = " <!NOTATION" + @source.buffer
               raise REXML::ParseException.new(message, @source)
             end
             name = parse_name(base_error_message)
             id = parse_id(base_error_message,
                           accept_external_id: true,
                           accept_public_id: true)
-            unless @source.match(/\A\s*>/um, true)
+            unless @source.match(/\s*>/um, true)
               message = "#{base_error_message}: garbage before end >"
               raise REXML::ParseException.new(message, @source)
             end
             return [:notationdecl, name, *id]
-          when DOCTYPE_END
+          elsif @source.match( /\]\s*>/um, true, false)
             @document_status = :after_doctype
-            @source.match( DOCTYPE_END, true )
             return [ :end_doctype ]
           end
         end
         if @document_status == :after_doctype
-          @source.match(/\A\s*/um, true)
+          @source.match(/\s*/um, true)
         end
         begin
           next_data = @source.buffer
           if next_data.size < 2
             @source.read
-            next_data = @source.buffer
           end
-          if next_data[0] == ?<
-            if next_data[1] == ?/
+          if @source.match(TAG_START, true, false)
+            if @source.match(SLASH, true, false)
               @nsstack.shift
               last_tag = @tags.pop
               md = @source.match( CLOSE_MATCH, true )
@@ -366,15 +355,16 @@ def pull_event
               if md.nil? or last_tag != md[1]
                 message = "Missing end tag for '#{last_tag}'"
                 message << " (got '#{md[1]}')" if md
+                @source.string = "</" + @source.buffer if md.nil?
                 raise REXML::ParseException.new(message, @source)
               end
               return [ :end_element, last_tag ]
-            elsif next_data[1] == ?!
-              md = @source.match(/\A(\s*[^>]*>)/um)
+            elsif @source.match(EXCLAMATION_MARK, true, false)
+              md = @source.match(/([^>]*>)/um)
               #STDERR.puts "SOURCE BUFFER = #{source.buffer}, #{source.buffer.size}"
               raise REXML::ParseException.new("Malformed node", @source) unless md
-              if md[0][2] == ?-
-                md = @source.match( COMMENT_PATTERN, true )
+              if md[0][0] == ?-
+                md = @source.match( /--(.*?)-->/um, true )
 
                 case md[1]
                 when /--/, /-\z/
@@ -383,17 +373,18 @@ def pull_event
 
                 return [ :comment, md[1] ] if md
               else
-                md = @source.match( CDATA_PATTERN, true )
+                md = @source.match( /\[CDATA\[(.*?)\]\]>/um, true )
                 return [ :cdata, md[1] ] if md
               end
               raise REXML::ParseException.new( "Declarations can only occur "+
                 "in the doctype declaration.", @source)
-            elsif next_data[1] == ??
+            elsif @source.match(QUESTION_MARK, true, false)
               return process_instruction
             else
               # Get the next tag
               md = @source.match(TAG_MATCH, true)
               unless md
+                @source.string = TAG_START + @source.buffer
                 raise REXML::ParseException.new("malformed XML: missing tag start", @source)
               end
               tag = md[1]
@@ -418,7 +409,7 @@ def pull_event
               return [ :start_element, tag, attributes ]
             end
           else
-            md = @source.match( TEXT_PATTERN, true )
+            md = @source.match( /([^<]*)/um, true )
             text = md[1]
             return [ :text, text ]
           end
@@ -580,6 +571,7 @@ def process_instruction
         match_data = @source.match(INSTRUCTION_PATTERN, true)
         unless match_data
           message = "Invalid processing instruction node"
+          @source.string = QUESTION_MARK_TAG_START + @source.buffer
           raise REXML::ParseException.new(message, @source)
         end
         [:processing_instruction, match_data[1], match_data[2]]
diff --git a/lib/rexml/source.rb b/lib/rexml/source.rb
index db78a12..034acf1 100644
--- a/lib/rexml/source.rb
+++ b/lib/rexml/source.rb
@@ -68,7 +68,7 @@ def encoding=(enc)
     def read
     end
 
-    def match(pattern, cons=false)
+    def match(pattern, cons=false, read_source=false)
       if cons
         @scanner.scan(pattern).nil? ? nil : @scanner
       else
@@ -76,6 +76,10 @@ def match(pattern, cons=false)
       end
     end
 
+    def string=(string)
+      @scanner.string = string
+    end
+
     # @return true if the Source is exhausted
     def empty?
       @scanner.eos?
@@ -155,13 +159,13 @@ def read
       end
     end
 
-    def match( pattern, cons=false )
+    def match( pattern, cons=false, read_source=true )
       if cons
         md = @scanner.scan(pattern)
       else
         md = @scanner.check(pattern)
       end
-      while md.nil? and @source
+      while read_source && md.nil? && @source
         begin
           @scanner << readline
           if cons