🔀 Merge pull request #439 from ruby/backport/v0.3-response_reader

♻️ Backport `ResponseReader`to v0.3

Author: nevans

lib/net/imap.rb

@@ -737,6 +737,8 @@ module Net
   class IMAP < Protocol
     VERSION = "0.3.8"
 
+    autoload :ResponseReader, File.expand_path("imap/response_reader", __dir__)
+
     include MonitorMixin
     if defined?(OpenSSL::SSL)
       include OpenSSL
@@ -2074,6 +2076,7 @@ def initialize(host, port_or_options = {},
       @idle_response_timeout = options[:idle_response_timeout] || 5
       @parser = ResponseParser.new
       @sock = tcp_socket(@host, @port)
+      @reader = ResponseReader.new(self, @sock)
       begin
         if options[:ssl]
           start_tls_session(options[:ssl])
@@ -2225,25 +2228,14 @@ def get_tagged_response(tag, cmd, timeout = nil)
     end
 
     def get_response
-      buff = String.new
-      while true
-        s = @sock.gets(CRLF)
-        break unless s
-        buff.concat(s)
-        if /\{(\d+)\}\r\n/n =~ s
-          s = @sock.read($1.to_i)
-          buff.concat(s)
-        else
-          break
-        end
-      end
+      buff = @reader.read_response_buffer
       return nil if buff.length == 0
-      if @@debug
-        $stderr.print(buff.gsub(/^/n, "S: "))
-      end
-      return @parser.parse(buff)
+      $stderr.print(buff.gsub(/^/n, "S: ")) if @@debug
+      @parser.parse(buff)
     end
 
+    #############################
+
     def record_response(name, data)
       unless @responses.has_key?(name)
         @responses[name] = []
@@ -2421,6 +2413,7 @@ def start_tls_session(params = {})
         context.verify_callback = VerifyCallbackProc
       end
       @sock = SSLSocket.new(@sock, context)
+      @reader = ResponseReader.new(self, @sock)
       @sock.sync_close = true
       @sock.hostname = @host if @sock.respond_to? :hostname=
       ssl_socket_connect(@sock, @open_timeout)

lib/net/imap/response_reader.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Net
+  class IMAP
+    # See https://www.rfc-editor.org/rfc/rfc9051#section-2.2.2
+    class ResponseReader # :nodoc:
+      attr_reader :client
+
+      def initialize(client, sock)
+        @client, @sock = client, sock
+      end
+
+      def read_response_buffer
+        @buff = String.new
+        catch :eof do
+          while true
+            read_line
+            break unless (@literal_size = get_literal_size)
+            read_literal
+          end
+        end
+        buff
+      ensure
+        @buff = nil
+      end
+
+      private
+
+      attr_reader :buff, :literal_size
+
+      def get_literal_size; /\{(\d+)\}\r\n\z/n =~ buff && $1.to_i end
+
+      def read_line
+        buff << (@sock.gets(CRLF) or throw :eof)
+      end
+
+      def read_literal
+        literal = String.new(capacity: literal_size)
+        buff << (@sock.read(literal_size, literal) or throw :eof)
+      ensure
+        @literal_size = nil
+      end
+
+    end
+  end
+end

test/net/imap/test_response_reader.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require "net/imap"
+require "stringio"
+require "test/unit"
+
+class ResponseReaderTest < Test::Unit::TestCase
+  class FakeClient
+  end
+
+  def literal(str) "{#{str.bytesize}}\r\n#{str}" end
+
+  test "#read_response_buffer" do
+    client = FakeClient.new
+    aaaaaaaaa    = "a" * (20 << 10)
+    many_crs     = "\r" * 1000
+    many_crlfs   = "\r\n" * 500
+    simple       = "* OK greeting\r\n"
+    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,
+    ].join)
+    rcvr = Net::IMAP::ResponseReader.new(client, io)
+    assert_equal simple,       rcvr.read_response_buffer.to_str
+    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
+    assert_equal "",           rcvr.read_response_buffer.to_str
+  end
+
+end