Convert to span and avoid deprecated ndn-cxx functions

Change-Id: I45c50527fe53498b53a3d951458bdff8e7d7778c
diff --git a/daemon/face/pcap-helper.cpp b/daemon/face/pcap-helper.cpp
index b7873fe..d481ac5 100644
--- a/daemon/face/pcap-helper.cpp
+++ b/daemon/face/pcap-helper.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2021,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -79,7 +79,7 @@
 }
 
 void
-PcapHelper::close()
+PcapHelper::close() noexcept
 {
   if (m_pcap) {
     pcap_close(m_pcap);
@@ -100,7 +100,7 @@
 }
 
 std::string
-PcapHelper::getLastError() const
+PcapHelper::getLastError() const noexcept
 {
   return pcap_geterr(m_pcap);
 }
@@ -128,19 +128,19 @@
     NDN_THROW(Error("pcap_setfilter: " + getLastError()));
 }
 
-std::tuple<const uint8_t*, size_t, std::string>
-PcapHelper::readNextPacket() const
+std::tuple<span<const uint8_t>, std::string>
+PcapHelper::readNextPacket() const noexcept
 {
   pcap_pkthdr* header;
   const uint8_t* packet;
 
   int ret = pcap_next_ex(m_pcap, &header, &packet);
   if (ret < 0)
-    return std::make_tuple(nullptr, 0, getLastError());
+    return {span<uint8_t>{}, getLastError()};
   else if (ret == 0)
-    return std::make_tuple(nullptr, 0, "timed out");
+    return {span<uint8_t>{}, "timed out"};
   else
-    return std::make_tuple(packet, header->caplen, "");
+    return {{packet, header->caplen}, ""};
 }
 
 } // namespace face