From 4c56eb8ec773780a9e46860207e2b7a00eed372f Mon Sep 17 00:00:00 2001
From: NAITOH Jun <naitoh@gmail.com>
Date: Sun, 7 Jan 2024 15:28:19 +0900
Subject: [PATCH] Remove @buffer and process only use @scanner.

---
 lib/rexml/parsers/baseparser.rb |  2 +-
 lib/rexml/source.rb             | 46 ++++++++++++++-------------------
 2 files changed, 20 insertions(+), 28 deletions(-)

diff --git a/lib/rexml/parsers/baseparser.rb b/lib/rexml/parsers/baseparser.rb
index aa4cb9b5..7faeb9ba 100644
--- a/lib/rexml/parsers/baseparser.rb
+++ b/lib/rexml/parsers/baseparser.rb
@@ -258,7 +258,7 @@ def pull_event
           else
             @document_status = :after_doctype
             if @source.encoding == "UTF-8"
-              @source.buffer.force_encoding(::Encoding::UTF_8)
+              @source.scanner.string = @source.scanner.rest.force_encoding(::Encoding::UTF_8)
             end
           end
         end
diff --git a/lib/rexml/source.rb b/lib/rexml/source.rb
index 9ad62b6a..b9cbc668 100644
--- a/lib/rexml/source.rb
+++ b/lib/rexml/source.rb
@@ -30,8 +30,7 @@ def SourceFactory::create_from(arg)
   # objects and provides consumption of text
   class Source
     include Encoding
-    # The current buffer (what we're going to read next)
-    attr_reader :buffer
+    # The current scanner (what we're going to read next)
     attr_reader :scanner
     # The line number of the last consumed text
     attr_reader :line
@@ -42,8 +41,8 @@ class Source
     # @param encoding if non-null, sets the encoding of the source to this
     # value, overriding all encoding detection
     def initialize(arg, encoding=nil)
-      @orig = @buffer = arg
-      @scanner = StringScanner.new(@buffer)
+      @orig = arg
+      @scanner = StringScanner.new(@orig)
       if encoding
         self.encoding = encoding
       else
@@ -64,10 +63,8 @@ def read
     end
 
     def match(pattern, cons=false)
-      @scanner.string = @buffer
       if cons
         @scanner.scan(pattern)
-        @buffer = @scanner.rest if @scanner.matched?
       else
         @scanner.check(pattern)
       end
@@ -88,34 +85,35 @@ def current_line
     end
 
     private
+
     def detect_encoding
-      buffer_encoding = @buffer.encoding
+      scanner_encoding = @scanner.rest.encoding
       detected_encoding = "UTF-8"
       begin
-        @buffer.force_encoding("ASCII-8BIT")
-        if @buffer[0, 2] == "\xfe\xff"
-          @buffer[0, 2] = ""
+        @scanner.string = @scanner.rest.force_encoding("ASCII-8BIT")
+        if @scanner.rest[0, 2] == "\xfe\xff"
+          @scanner.string = @scanner.rest.delete_prefix("\xfe\xff")
           detected_encoding = "UTF-16BE"
-        elsif @buffer[0, 2] == "\xff\xfe"
-          @buffer[0, 2] = ""
+        elsif @scanner.rest[0, 2] == "\xff\xfe"
+          @scanner.string = @scanner.rest.delete_prefix("\xff\xfe")
           detected_encoding = "UTF-16LE"
-        elsif @buffer[0, 3] == "\xef\xbb\xbf"
-          @buffer[0, 3] = ""
+        elsif @scanner.rest[0, 3] == "\xef\xbb\xbf"
+          @scanner.string = @scanner.rest.delete_prefix("\xef\xbb\xbf")
           detected_encoding = "UTF-8"
         end
       ensure
-        @buffer.force_encoding(buffer_encoding)
+        @scanner.string = @scanner.rest.force_encoding(scanner_encoding)
       end
       self.encoding = detected_encoding
     end
 
     def encoding_updated
       if @encoding != 'UTF-8'
-        @buffer = decode(@buffer)
+        @scanner.string = decode(@scanner.rest)
         @to_utf = true
       else
         @to_utf = false
-        @buffer.force_encoding ::Encoding::UTF_8
+        @scanner.string = @scanner.rest.force_encoding(::Encoding::UTF_8)
       end
     end
   end
@@ -138,7 +136,7 @@ def initialize(arg, block_size=500, encoding=nil)
       end
 
       if !@to_utf and
-          @buffer.respond_to?(:force_encoding) and
+          @orig.respond_to?(:force_encoding) and
           @source.respond_to?(:external_encoding) and
           @source.external_encoding != ::Encoding::UTF_8
         @force_utf8 = true
@@ -149,32 +147,26 @@ def initialize(arg, block_size=500, encoding=nil)
 
     def read
       begin
-        @buffer << readline
-        @scanner.string = @buffer
+        @scanner.string = @scanner.rest + readline
       rescue Exception, NameError
         @source = nil
       end
     end
 
     def match( pattern, cons=false )
-      @scanner.string = @buffer
       if cons
         @scanner.scan(pattern)
-        @buffer = @scanner.rest if @scanner.matched?
       else
         @scanner.check(pattern)
       end
       while !@scanner.matched? and @source
         begin
-          @buffer << readline
-          @scanner.string = @buffer
+          @scanner << readline
           if cons
             @scanner.scan(pattern)
-            @buffer = @scanner.rest if @scanner.matched?
           else
             @scanner.check(pattern)
           end
-          @buffer = @scanner.rest if cons and @scanner.matched?
         rescue
           @source = nil
         end
@@ -237,7 +229,7 @@ def encoding_updated
         @source.set_encoding(@encoding, @encoding)
       end
       @line_break = encode(">")
-      @pending_buffer, @buffer = @buffer, ""
+      @pending_buffer, @scanner.string = @scanner.rest, ""
       @pending_buffer.force_encoding(@encoding)
       super
     end