[feat] add rtcp packet module

src/common/sequence_number_compare.h

@@ -0,0 +1,44 @@
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+
+template <typename U>
+inline bool IsNewer(U value, U prev_value) {
+  static_assert(!std::numeric_limits<U>::is_signed, "U must be unsigned");
+  // kBreakpoint is the half-way mark for the type U. For instance, for a
+  // uint16_t it will be 0x8000, and for a uint32_t, it will be 0x8000000.
+  constexpr U kBreakpoint = (std::numeric_limits<U>::max() >> 1) + 1;
+  // Distinguish between elements that are exactly kBreakpoint apart.
+  // If t1>t2 and |t1-t2| = kBreakpoint: IsNewer(t1,t2)=true,
+  // IsNewer(t2,t1)=false
+  // rather than having IsNewer(t1,t2) = IsNewer(t2,t1) = false.
+  if (value - prev_value == kBreakpoint) {
+    return value > prev_value;
+  }
+  return value != prev_value &&
+         static_cast<U>(value - prev_value) < kBreakpoint;
+}
+
+// NB: Doesn't fulfill strict weak ordering requirements.
+//     Mustn't be used as std::map Compare function.
+inline bool IsNewerSequenceNumber(uint16_t sequence_number,
+                                  uint16_t prev_sequence_number) {
+  return IsNewer(sequence_number, prev_sequence_number);
+}
+
+// NB: Doesn't fulfill strict weak ordering requirements.
+//     Mustn't be used as std::map Compare function.
+inline bool IsNewerTimestamp(uint32_t timestamp, uint32_t prev_timestamp) {
+  return IsNewer(timestamp, prev_timestamp);
+}
+
+inline uint16_t LatestSequenceNumber(uint16_t sequence_number1,
+                                     uint16_t sequence_number2) {
+  return IsNewerSequenceNumber(sequence_number1, sequence_number2)
+             ? sequence_number1
+             : sequence_number2;
+}
+
+inline uint32_t LatestTimestamp(uint32_t timestamp1, uint32_t timestamp2) {
+  return IsNewerTimestamp(timestamp1, timestamp2) ? timestamp1 : timestamp2;
+}