[core] Add CRcvBufferNew::dropUnitInPos(..) (#2226)

to simplify dropUpTo(..) and dropMessage(..)

srtcore/buffer_rcv.cpp

@@ -605,6 +605,24 @@ void CRcvBufferNew::releaseUnitInPos(int pos)
         m_pUnitQueue->makeUnitFree(tmp);
 }
 
+bool CRcvBufferNew::dropUnitInPos(int pos)
+{
+    if (!m_entries[pos].pUnit)
+        return false;
+    if (m_tsbpd.isEnabled())
+    {
+        updateTsbPdTimeBase(m_entries[pos].pUnit->m_Packet.getMsgTimeStamp());
+    }
+    else if (m_bMessageAPI && !m_entries[pos].pUnit->m_Packet.getMsgOrderFlag())
+    {
+        --m_numOutOfOrderPackets;
+        if (pos == m_iFirstReadableOutOfOrder)
+            m_iFirstReadableOutOfOrder = -1;
+    }
+    releaseUnitInPos(pos);
+    return true;
+}
+
 void CRcvBufferNew::releaseNextFillerEntries()
 {
     int pos = m_iStartPos;

srtcore/buffer_rcv.h

@@ -221,6 +221,11 @@ class CRcvBufferNew
     void updateNonreadPos();
     void releaseUnitInPos(int pos);
 
+    /// @brief Drop a unit from the buffer.
+    /// @param pos position in the m_entries of the unit to drop.
+    /// @return false if nothing to drop, true if the unit was dropped successfully.
+    bool dropUnitInPos(int pos);
+
     /// Release entries following the current buffer position if they were already
     /// read out of order (EntryState_Read) or dropped (EntryState_Drop).
     void releaseNextFillerEntries();