Use std::unique_ptr for mnList in CSimplifiedMNList (#3014)

This allows much faster sorting as it avoids copying/swapping
expensive objects.

Author: codablock

src/evo/simplifiedmns.cpp

@@ -54,23 +54,27 @@ void CSimplifiedMNListEntry::ToJson(UniValue& obj) const
 
 CSimplifiedMNList::CSimplifiedMNList(const std::vector<CSimplifiedMNListEntry>& smlEntries)
 {
-    mnList = smlEntries;
+    mnList.resize(smlEntries.size());
+    for (size_t i = 0; i < smlEntries.size(); i++) {
+        mnList[i] = std::make_unique<CSimplifiedMNListEntry>(smlEntries[i]);
+    }
 
-    std::sort(mnList.begin(), mnList.end(), [&](const CSimplifiedMNListEntry& a, const CSimplifiedMNListEntry& b) {
-        return a.proRegTxHash.Compare(b.proRegTxHash) < 0;
+    std::sort(mnList.begin(), mnList.end(), [&](const std::unique_ptr<CSimplifiedMNListEntry>& a, const std::unique_ptr<CSimplifiedMNListEntry>& b) {
+        return a->proRegTxHash.Compare(b->proRegTxHash) < 0;
     });
 }
 
 CSimplifiedMNList::CSimplifiedMNList(const CDeterministicMNList& dmnList)
 {
-    mnList.reserve(dmnList.GetAllMNsCount());
+    mnList.resize(dmnList.GetAllMNsCount());
 
-    dmnList.ForEachMN(false, [this](const CDeterministicMNCPtr& dmn) {
-        mnList.emplace_back(*dmn);
+    size_t i = 0;
+    dmnList.ForEachMN(false, [this, &i](const CDeterministicMNCPtr& dmn) {
+        mnList[i++] = std::make_unique<CSimplifiedMNListEntry>(*dmn);
     });
 
-    std::sort(mnList.begin(), mnList.end(), [&](const CSimplifiedMNListEntry& a, const CSimplifiedMNListEntry& b) {
-        return a.proRegTxHash.Compare(b.proRegTxHash) < 0;
+    std::sort(mnList.begin(), mnList.end(), [&](const std::unique_ptr<CSimplifiedMNListEntry>& a, const std::unique_ptr<CSimplifiedMNListEntry>& b) {
+        return a->proRegTxHash.Compare(b->proRegTxHash) < 0;
     });
 }
 
@@ -79,7 +83,7 @@ uint256 CSimplifiedMNList::CalcMerkleRoot(bool* pmutated) const
     std::vector<uint256> leaves;
     leaves.reserve(mnList.size());
     for (const auto& e : mnList) {
-        leaves.emplace_back(e.CalcHash());
+        leaves.emplace_back(e->CalcHash());
     }
     return ComputeMerkleRoot(leaves, pmutated);
 }

src/evo/simplifiedmns.h

@@ -74,7 +74,7 @@ class CSimplifiedMNListEntry
 class CSimplifiedMNList
 {
 public:
-    std::vector<CSimplifiedMNListEntry> mnList;
+    std::vector<std::unique_ptr<CSimplifiedMNListEntry>> mnList;
 
 public:
     CSimplifiedMNList() {}