From f94360305b9008a3509a5d600762b45b04e95fb3 Mon Sep 17 00:00:00 2001
From: furszy <5377650+furszy@users.noreply.github.com>
Date: Wed, 27 Mar 2019 13:22:57 +0100
Subject: [PATCH] zpiv already precomputed validation + witness height refactor

---
 src/wallet.cpp            | 13 ++++++++-----
 src/zpiv/accumulators.cpp | 39 ++++++++++++++++++---------------------
 src/zpiv/accumulators.h   |  7 +++++++
 3 files changed, 33 insertions(+), 26 deletions(-)

diff --git a/src/wallet.cpp b/src/wallet.cpp
index 5bbadb4f4c461..0e5578a5983e0 100644
--- a/src/wallet.cpp
+++ b/src/wallet.cpp
@@ -4742,11 +4742,14 @@ bool CWallet::MintsToInputVector(std::map<CBigNum, CZerocoinMint>& mapMintsSelec
                 coinWitness->SetHeightMintAdded(mint.GetHeight());
             }
 
-            // Generate the witness for each mint being spent
-            if (!GenerateAccumulatorWitness(coinWitness, mapAccumulators, pindexCheckpoint)) {
-                receipt.SetStatus(_("Try to spend with a higher security level to include more coins"),
-                                  ZPIV_FAILED_ACCUMULATOR_INITIALIZATION);
-                return error("%s : %s", __func__, receipt.GetStatusMessage());
+            // Check if it's already precomputed
+            if (CalWitUpToChainHeight(pindexCheckpoint) > coinWitness->nHeightAccEnd){
+                // Generate the witness for each mint being spent
+                if (!GenerateAccumulatorWitness(coinWitness, mapAccumulators, pindexCheckpoint)) {
+                    receipt.SetStatus(_("Try to spend with a higher security level to include more coins"),
+                                      ZPIV_FAILED_ACCUMULATOR_INITIALIZATION);
+                    return error("%s : %s", __func__, receipt.GetStatusMessage());
+                }
             }
 
             // Construct the CoinSpend object. This acts like a signature on the transaction.
diff --git a/src/zpiv/accumulators.cpp b/src/zpiv/accumulators.cpp
index fa4b98614d162..30d25b51b6b9b 100644
--- a/src/zpiv/accumulators.cpp
+++ b/src/zpiv/accumulators.cpp
@@ -555,21 +555,8 @@ bool GenerateAccumulatorWitness(CoinWitnessData* coinWitness, AccumulatorMap& ma
             coinWitness->pAccumulator->setValue(witnessAccumulator.getValue());
         }
 
-        //add the pubcoins from the blockchain up to the next checksum starting from the block
-        int nChainHeight = chainActive.Height();
-        int nHeightMax = nChainHeight % 10;
-        nHeightMax = nChainHeight - nHeightMax - 20; // at least two checkpoints deep
-
         // Determine the height to stop at
-        int nHeightStop;
-        if (pindexCheckpoint) {
-            nHeightStop = pindexCheckpoint->nHeight - 10;
-            nHeightStop -= nHeightStop % 10;
-            LogPrint("zero", "%s: using checkpoint height %d\n", __func__, pindexCheckpoint->nHeight);
-        } else {
-            nHeightStop = nHeightMax;
-        }
-
+        int nHeightStop = CalWitUpToChainHeight(pindexCheckpoint);
         if (nHeightStop <= coinWitness->nHeightAccEnd)
             return error("%s: trying to accumulate bad block range, start=%d end=%d", __func__, coinWitness->nHeightAccEnd, nHeightStop);
 
@@ -832,13 +819,7 @@ bool GenerateAccumulatorWitness(
 
         //add the pubcoins from the blockchain up to the next checksum starting from the block
         CBlockIndex *pindex = chainActive[nHeightCheckpoint - 10];
-        int nChainHeight = chainActive.Height();
-        int nHeightStop = nChainHeight % 10;
-        nHeightStop = nChainHeight - nHeightStop - 20; // at least two checkpoints deep
-
-        //If looking for a specific checkpoint
-        if (pindexCheckpoint)
-            nHeightStop = pindexCheckpoint->nHeight - 10;
+        int nHeightStop = CalWitUpToChainHeight(pindexCheckpoint);
 
         //Iterate through the chain and calculate the witness
         int nCheckpointsAdded = 0;
@@ -930,3 +911,19 @@ map<CoinDenomination, int> GetMintMaturityHeight()
 
     return mapRet;
 }
+
+/**
+ * If pindex is null then it will return the chain head mature checkpoint height
+ * @param pindex
+ * @return
+ */
+int CalWitUpToChainHeight(CBlockIndex* pindex){
+    if (pindex){
+        int nHeightStop = pindex->nHeight - 10;
+        nHeightStop -= nHeightStop % 10;
+        return nHeightStop;
+    }else{
+        int nChainHeight = chainActive.Height();
+        return nChainHeight - (nChainHeight % 10) - 20; // at least two checkpoints deep
+    }
+}
\ No newline at end of file
diff --git a/src/zpiv/accumulators.h b/src/zpiv/accumulators.h
index 7089961b76cc7..5b349372adbb5 100644
--- a/src/zpiv/accumulators.h
+++ b/src/zpiv/accumulators.h
@@ -63,6 +63,13 @@ int GetChecksumHeight(uint32_t nChecksum, libzerocoin::CoinDenomination denomina
 bool InvalidCheckpointRange(int nHeight);
 bool ValidateAccumulatorCheckpoint(const CBlock& block, CBlockIndex* pindex, AccumulatorMap& mapAccumulators);
 
+/**
+ * If pindex is null then it will return the last mature checkpoint height
+ * @param pindex
+ * @return
+ */
+int CalWitUpToChainHeight(CBlockIndex* pindex = nullptr);
+
 
 // Exceptions