* ext/pty/lib/expect.rb: preserve buffer read, instead of discard.

based on a patch from Luiz Angelo Daros de Luca in
  [ruby-core:23464].

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@27277 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Sat Apr 10 00:01:51 2010  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* ext/pty/lib/expect.rb: preserve buffer read, instead of discard.
+	  based on a patch from Luiz Angelo Daros de Luca in
+	  [ruby-core:23464].
+
 Fri Apr  9 23:58:58 2010  Yusuke Endoh  <mame@tsg.ne.jp>
 
 	* ext/pty/lib/expect.rb: raise an error when argument is unexpected

ext/pty/lib/expect.rb

@@ -17,12 +17,17 @@ class IO
     else
       raise TypeError, "unsupported pattern class: #{pattern.class}"
     end
+    @unusedBuf ||= ''
     while true
-      if !IO.select([self],nil,nil,timeout) or eof? then
+      if not @unusedBuf.empty?
+        c = @unusedBuf.slice!(0).chr
+      elsif !IO.select([self],nil,nil,timeout) or eof? then
         result = nil
+        @unusedBuf = buf
         break
+      else
+        c = getc.chr
       end
-      c = getc.chr
       buf << c
       if $expect_verbose
         STDOUT.print c