[1331] Add SOA::getSerial method

src/lib/dns/rdata/generic/soa_6.cc

@@ -106,6 +106,12 @@ SOA::toWire(AbstractMessageRenderer& renderer) const {
     renderer.writeData(numdata_, sizeof(numdata_));
 }
 
+uint32_t
+SOA::getSerial() const {
+    InputBuffer b(numdata_, sizeof(numdata_));
+    return (b.readUint32());
+}
+
 string
 SOA::toText() const {
     InputBuffer b(numdata_, sizeof(numdata_));

src/lib/dns/rdata/generic/soa_6.h

@@ -34,6 +34,8 @@ public:
     SOA(const Name& mname, const Name& rname, uint32_t serial,
         uint32_t refresh, uint32_t retry, uint32_t expire,
         uint32_t minimum);
+    /// \brief Returns the serial stored in the SOA.
+    uint32_t getSerial() const;
 private:
     /// Note: this is a prototype version; we may reconsider
     /// this representation later.

src/lib/dns/tests/rdata_soa_unittest.cc

@@ -74,4 +74,9 @@ TEST_F(Rdata_SOA_Test, toText) {
     EXPECT_EQ("ns.example.com. root.example.com. "
               "2010012601 3600 300 3600000 1200", rdata_soa.toText());
 }
+
+TEST_F(Rdata_SOA_Test, getSerial) {
+    EXPECT_EQ(2010012601, rdata_soa.getSerial());
+}
+
 }