[Consensus] set placeholder for nPublicZCSpendsV4

sets temporarily the activation height for zerocoin public spends v4. Also defines an helper function Zerocoin_PublicSpendVersion which returns the version active at a given block height

src/chainparams.cpp

@@ -129,6 +129,13 @@ bool CChainParams::HasStakeMinAgeOrDepth(const int contextHeight, const uint32_t
     return (contextHeight - utxoFromBlockHeight >= nStakeMinDepth);
 }
 
+int CChainParams::Zerocoin_PublicSpendVersion(const int nHeight) const
+{
+    if (nHeight < nPublicZCSpendsV4)
+        return 3;
+    return 4;
+}
+
 class CMainParams : public CChainParams
 {
 public:
@@ -182,6 +189,7 @@ class CMainParams : public CChainParams
         nBlockStakeModifierlV2 = 1967000;
         // Public coin spend enforcement
         nPublicZCSpends = 1880000;
+        nPublicZCSpendsV4 = 2880000;
 
         // New P2P messages signatures
         nBlockEnforceNewMessageSignatures = 2967000;
@@ -320,6 +328,7 @@ class CTestNetParams : public CMainParams
         nBlockStakeModifierlV2 = 1214000;
         // Public coin spend enforcement
         nPublicZCSpends = 1106100;
+        nPublicZCSpendsV4 = 2106100;
 
         // New P2P messages signatures
         nBlockEnforceNewMessageSignatures = 2214000;
@@ -416,6 +425,7 @@ class CRegTestParams : public CTestNetParams
         nBlockStakeModifierlV2 = std::numeric_limits<int>::max(); // max integer value (never switch on regtest)
         // Public coin spend enforcement
         nPublicZCSpends = 350;
+        nPublicZCSpendsV4 = 450;
 
         // New P2P messages signatures
         nBlockEnforceNewMessageSignatures = 1;

src/chainparams.h

@@ -141,6 +141,7 @@ class CChainParams
     int Zerocoin_Block_V2_Start() const { return nBlockZerocoinV2; }
     bool IsStakeModifierV2(const int nHeight) const { return nHeight >= nBlockStakeModifierlV2; }
     int NewSigsActive(const int nHeight) const { return nHeight >= nBlockEnforceNewMessageSignatures; }
+    int Zerocoin_PublicSpendVersion(const int nHeight) const;
 
     // fake serial attack
     int Zerocoin_Block_EndFakeSerial() const { return nFakeSerialBlockheightEnd; }
@@ -223,6 +224,7 @@ class CChainParams
     int nBlockZerocoinV2;
     int nBlockDoubleAccumulated;
     int nPublicZCSpends;
+    int nPublicZCSpendsV4;
     int nBlockStakeModifierlV2;
     int nBlockEnforceNewMessageSignatures;