♻️ Save ResponseReader ivars: @buff & @literal_size

This avoids the need to pass these to every method that uses them.
That's not a big deal now, but it simplifies the next few changes.

Also added a missing test for empty literals: "{0}\r\n"

Author: nevans

lib/net/imap/response_reader.rb

@@ -11,26 +11,34 @@ def initialize(client, sock)
       end
 
       def read_response_buffer
-        buff = String.new
+        @buff = String.new
         catch :eof do
           while true
-            read_line(buff)
-            break unless /\{(\d+)\}\r\n\z/n =~ buff
-            read_literal(buff, $1.to_i)
+            read_line
+            break unless (@literal_size = get_literal_size)
+            read_literal
           end
         end
         buff
+      ensure
+        @buff = nil
       end
 
       private
 
-      def read_line(buff)
+      attr_reader :buff, :literal_size
+
+      def get_literal_size    = /\{(\d+)\}\r\n\z/n =~ buff && $1.to_i
+
+      def read_line
         buff << (@sock.gets(CRLF) or throw :eof)
       end
 
-      def read_literal(buff, literal_size)
+      def read_literal
         literal = String.new(capacity: literal_size)
         buff << (@sock.read(literal_size, literal) or throw :eof)
+      ensure
+        @literal_size = nil
       end
 
     end

test/net/imap/test_response_reader.rb

@@ -19,13 +19,15 @@ def literal(str) "{#{str.bytesize}}\r\n#{str}" end
     long_line    = "tag ok #{aaaaaaaaa} #{aaaaaaaaa}\r\n"
     literal_aaaa = "* fake #{literal aaaaaaaaa}\r\n"
     literal_crlf = "tag ok #{literal many_crlfs} #{literal many_crlfs}\r\n"
+    zero_literal = "tag ok #{literal ""} #{literal ""}\r\n"
     illegal_crs  = "tag ok #{many_crs} #{many_crs}\r\n"
     illegal_lfs  = "tag ok #{literal "\r"}\n#{literal "\r"}\n\r\n"
     io = StringIO.new([
       simple,
       long_line,
       literal_aaaa,
       literal_crlf,
+      zero_literal,
       illegal_crs,
       illegal_lfs,
       simple,
@@ -35,6 +37,7 @@ def literal(str) "{#{str.bytesize}}\r\n#{str}" end
     assert_equal long_line,    rcvr.read_response_buffer.to_str
     assert_equal literal_aaaa, rcvr.read_response_buffer.to_str
     assert_equal literal_crlf, rcvr.read_response_buffer.to_str
+    assert_equal zero_literal, rcvr.read_response_buffer.to_str
     assert_equal illegal_crs,  rcvr.read_response_buffer.to_str
     assert_equal illegal_lfs,  rcvr.read_response_buffer.to_str
     assert_equal simple,       rcvr.read_response_buffer.to_str