Create class hierarchy for SproutNotePlaintext.

BaseNotePlaintext contains member variable for common attribute, value.

src/zcash/Note.cpp

@@ -42,14 +42,14 @@ SproutNotePlaintext::SproutNotePlaintext(
     const SproutNote& note,
     boost::array<unsigned char, ZC_MEMO_SIZE> memo) : memo(memo)
 {
-    value = note.value();
+    value_ = note.value();
     rho = note.rho;
     r = note.r;
 }
 
 SproutNote SproutNotePlaintext::note(const PaymentAddress& addr) const
 {
-    return SproutNote(addr.a_pk, value, rho, r);
+    return SproutNote(addr.a_pk, value_, rho, r);
 }
 
 SproutNotePlaintext SproutNotePlaintext::decrypt(const ZCNoteDecryption& decryptor,

src/zcash/Note.hpp

@@ -38,9 +38,18 @@ public:
     uint256 nullifier(const SpendingKey& a_sk) const;
 };
 
-class SproutNotePlaintext {
+class BaseNotePlaintext {
+protected:
+    uint64_t value_ = 0;
+public:
+    BaseNotePlaintext() {}
+    virtual ~BaseNotePlaintext() {}
+
+    inline uint64_t value() const { return value_; }
+};
+
+class SproutNotePlaintext : public BaseNotePlaintext {
 public:
-    uint64_t value = 0;
     uint256 rho;
     uint256 r;
     boost::array<unsigned char, ZC_MEMO_SIZE> memo;
@@ -51,6 +60,8 @@ public:
 
     SproutNote note(const PaymentAddress& addr) const;
 
+    virtual ~SproutNotePlaintext() {}
+
     ADD_SERIALIZE_METHODS;
 
     template <typename Stream, typename Operation>
@@ -62,7 +73,7 @@ public:
             throw std::ios_base::failure("lead byte of SproutNotePlaintext is not recognized");
         }
 
-        READWRITE(value);
+        READWRITE(value_);
         READWRITE(rho);
         READWRITE(r);
         READWRITE(memo);