chunks: code cleanups

  * Introduce getSegmentFromPacket() helper function
  * Use signed arithmetic for some quantities to avoid conversion issues
  * Move start time handling to PipelineInterests base class

Change-Id: I275acac1ad93e4a72374d03fad0a1d7348d70976
diff --git a/tools/chunks/catchunks/pipeline-interests-aimd.hpp b/tools/chunks/catchunks/pipeline-interests-aimd.hpp
index c67d5bc..1670fda 100644
--- a/tools/chunks/catchunks/pipeline-interests-aimd.hpp
+++ b/tools/chunks/catchunks/pipeline-interests-aimd.hpp
@@ -1,3 +1,4 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
  * Copyright (c) 2016-2017, Regents of the University of California,
  *                          Colorado State University,
@@ -196,12 +197,10 @@
   uint64_t m_recPoint; ///< the value of m_highInterest when a packet loss event occurred,
                        ///< it remains fixed until the next packet loss event happens
 
-  uint64_t m_nInFlight; ///< # of segments in flight
-  uint64_t m_nReceived; ///< # of segments received
-  uint64_t m_nLossEvents; ///< # of loss events occurred
-  uint64_t m_nRetransmitted; ///< # of segments retransmitted
-
-  time::steady_clock::TimePoint m_startTime; ///< start time of pipelining
+  int64_t m_nInFlight; ///< # of segments in flight
+  int64_t m_nReceived; ///< # of segments received
+  int64_t m_nLossEvents; ///< # of loss events occurred
+  int64_t m_nRetransmitted; ///< # of segments retransmitted
 
   double m_cwnd; ///< current congestion window size (in segments)
   double m_ssthresh; ///< current slow start threshold