Skip over corsaro tags when returning initial packet string for rsdos

Also added a getRsdosPacketSize() method that accounts for any
tag header that may be present.

src/pyavro_stardust/rsdos.pxd

@@ -65,6 +65,7 @@ cdef class AvroRsdos(AvroRecord):
     cpdef void setSchemaVersion(self, const unsigned int schemaversion)
     cpdef void resetRecord(self)
     cpdef bytes getRsdosPacketString(self)
+    cpdef unsigned int getRsdosPacketSize(self)
     cpdef int setRsdosPacketString(self, const unsigned char[:] buf,
             const unsigned int maxlen)
 

src/pyavro_stardust/rsdos.pyx

@@ -63,12 +63,12 @@ cdef class AvroRsdos(AvroRecord):
                  self.attributes_l[<int>ATTR_RSDOS_PACKET_CNT],
                  self.attributes_l[<int>ATTR_RSDOS_BYTE_CNT],
                  self.attributes_l[<int>ATTR_RSDOS_MAX_PPM_INTERVAL],
-                 self.pktcontentlen)
+                 self.getRsdosPacketSize())
 
     cpdef dict asDict(self):
         cdef dict result
 
-        if self.pktcontentlen == 0:
+        if self.getRsdosPacketSize() == 0:
             initpkt = None
         else:
             initpkt = self.getRsdosPacketString()
@@ -106,13 +106,41 @@ cdef class AvroRsdos(AvroRecord):
         super(AvroRsdos, self).resetRecord()
 
     cpdef bytes getRsdosPacketString(self):
-        return <bytes>self.packetcontent[:self.pktcontentlen]
+        cdef unsigned int tagheadersize
+
+        tagheadersize = 0
+
+        # Ideally, we would be able to pull the size out of libtrace or
+        # libcorsaro, but for now we'll just have to hard-code the size here
+        if self.schemaversion == 1:
+            tagheadersize = 35 + (4 * 8)
+
+        if self.pktcontentlen <= tagheadersize:
+            return None
+
+        return <bytes>self.packetcontent[tagheadersize:self.pktcontentlen]
+
+    cpdef unsigned int getRsdosPacketSize(self):
+        cdef unsigned int tagheadersize
+
+        tagheadersize = 0
+
+        # Ideally, we would be able to pull the size out of libtrace or
+        # libcorsaro, but for now we'll just have to hard-code the size here
+        if self.schemaversion == 1:
+            tagheadersize = 35 + (4 * 8)
+
+        if self.pktcontentlen <= tagheadersize:
+            return 0
+
+        return self.pktcontentlen - tagheadersize
 
     cpdef int setRsdosPacketString(self, const unsigned char[:] buf,
             const unsigned int maxlen):
 
         cdef parsedString astr
 
+
         astr = read_string(buf, maxlen, addNullTerm=False)
         if astr.toskip == 0:
             return 0