Fix subtractive timeout and add specs.

Author: jemc

lib/rabbitmq/client/connection.rb

@@ -103,15 +103,19 @@ def login!
         @server_properties = FFI::Table.new(FFI.amqp_get_server_properties(@ptr)).to_h
       end
 
+      # Calculate the amount of the timeout remaining from the given start time
+      def remaining_timeout(timeout=0, start=Time.now)
+        return nil unless timeout
+        timeout = timeout - (Time.now - start)
+        timeout < 0 ? 0 : timeout
+      end
+      
       # Block until there is readable data on the internal ruby socket,
       # returning true if there is readable data, or false if time expired.
       def select(timeout=0, start=Time.now)
-        if timeout
-          timeout = timeout - (start-Time.now)
-          timeout = 0 if timeout < 0
-        end
-        
-        IO.select([@ruby_socket], [], [], timeout) ? true : false
+        IO.select([@ruby_socket], [], [],
+          remaining_timeout(timeout, start)
+        ) ? true : false
       end
 
       # Return the next available frame, or nil if time expired.

spec/client/connection_spec.rb

@@ -79,4 +79,22 @@
     subject.options[:ssl]     .should eq false
   end
 
+  describe "remaining_timeout" do
+    it "returns nil when given a timeout of nil" do
+      subject.remaining_timeout(nil).should eq nil
+    end
+    
+    it "returns 0 when time has already run out" do
+      time_now = Time.now
+      subject.remaining_timeout(0,   time_now)      .should eq 0
+      subject.remaining_timeout(5.0, time_now - 5)  .should eq 0
+      subject.remaining_timeout(5.0, time_now - 10) .should eq 0
+      subject.remaining_timeout(5.0, time_now - 100).should eq 0
+    end
+    
+    it "returns the remaining time when there is time remaining" do
+      subject.remaining_timeout(10.0, Time.now-5).should be_within(1.0).of(5.0)
+    end
+  end
+  
 end