Fix disconnected C result handling (#590)

Author: zhanglistar

include/pulsar/c/result.h

@@ -92,6 +92,7 @@ typedef enum
 
     pulsar_result_MemoryBufferIsFull,  /// Client-wide memory limit has been reached
     pulsar_result_Interrupted,         /// Interrupted while waiting to dequeue
+    pulsar_result_Disconnected,        /// Client connection has been disconnected
 } pulsar_result;
 
 // Return string representation of result code

tests/c/c_MessageTest.cc

@@ -18,7 +18,9 @@
  */
 #include <gtest/gtest.h>
 #include <lib/c/c_structs.h>
+#include <pulsar/Result.h>
 #include <pulsar/c/message.h>
+#include <pulsar/c/result.h>
 
 #include "../PulsarFriend.h"
 
@@ -48,3 +50,8 @@ TEST(c_MessageTest, ReplicationMetadataAccessors) {
 
     pulsar_message_free(message);
 }
+
+TEST(c_ResultTest, DisconnectedResultMatchesCppResult) {
+    ASSERT_EQ(static_cast<int>(pulsar::ResultDisconnected), static_cast<int>(pulsar_result_Disconnected));
+    ASSERT_STREQ("ResultDisconnected", pulsar_result_str(pulsar_result_Disconnected));
+}