Add deterministic mode to CCoinsViewCache

Author: sipa

src/coins.cpp

@@ -32,7 +32,10 @@ bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock,
 std::unique_ptr<CCoinsViewCursor> CCoinsViewBacked::Cursor() const { return base->Cursor(); }
 size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }
 
-CCoinsViewCache::CCoinsViewCache(CCoinsView* baseIn) : CCoinsViewBacked(baseIn) {}
+CCoinsViewCache::CCoinsViewCache(CCoinsView* baseIn, bool deterministic) :
+    CCoinsViewBacked(baseIn), m_deterministic(deterministic),
+    cacheCoins(0, SaltedOutpointHasher(/*deterministic=*/deterministic))
+{}
 
 size_t CCoinsViewCache::DynamicMemoryUsage() const {
     return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
@@ -311,7 +314,7 @@ void CCoinsViewCache::ReallocateCache()
     // Cache should be empty when we're calling this.
     assert(cacheCoins.size() == 0);
     cacheCoins.~CCoinsMap();
-    ::new (&cacheCoins) CCoinsMap();
+    ::new (&cacheCoins) CCoinsMap(0, SaltedOutpointHasher(/*deterministic=*/m_deterministic));
 }
 
 void CCoinsViewCache::SanityCheck() const

src/coins.h

@@ -211,6 +211,9 @@ class CCoinsViewBacked : public CCoinsView
 /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
 class CCoinsViewCache : public CCoinsViewBacked
 {
+private:
+    const bool m_deterministic;
+
 protected:
     /**
      * Make mutable so that we can "fill the cache" even from Get-methods
@@ -223,7 +226,7 @@ class CCoinsViewCache : public CCoinsViewBacked
     mutable size_t cachedCoinsUsage{0};
 
 public:
-    CCoinsViewCache(CCoinsView *baseIn);
+    CCoinsViewCache(CCoinsView *baseIn, bool deterministic = false);
 
     /**
      * By deleting the copy constructor, we prevent accidentally using it when one intends to create a cache on top of a base cache.

src/test/fuzz/coins_view.cpp

@@ -46,7 +46,7 @@ FUZZ_TARGET_INIT(coins_view, initialize_coins_view)
 {
     FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
     CCoinsView backend_coins_view;
-    CCoinsViewCache coins_view_cache{&backend_coins_view};
+    CCoinsViewCache coins_view_cache{&backend_coins_view, /*deterministic=*/true};
     COutPoint random_out_point;
     Coin random_coin;
     CMutableTransaction random_mutable_transaction;

src/test/fuzz/coinscache_sim.cpp

@@ -245,7 +245,7 @@ FUZZ_TARGET(coinscache_sim)
         ++current_height;
         // Make sure there is always at least one CCoinsViewCache.
         if (caches.empty()) {
-            caches.emplace_back(new CCoinsViewCache(&bottom));
+            caches.emplace_back(new CCoinsViewCache(&bottom, /*deterministic=*/true));
             sim_caches[caches.size()].Wipe();
         }
 
@@ -374,7 +374,7 @@ FUZZ_TARGET(coinscache_sim)
             [&]() { // Add a cache level (if not already at the max).
                 if (caches.size() != MAX_CACHES) {
                     // Apply to real caches.
-                    caches.emplace_back(new CCoinsViewCache(&*caches.back()));
+                    caches.emplace_back(new CCoinsViewCache(&*caches.back(), /*deterministic=*/true));
                     // Apply to simulation data.
                     sim_caches[caches.size()].Wipe();
                 }

src/util/hasher.cpp

@@ -9,7 +9,10 @@
 
 SaltedTxidHasher::SaltedTxidHasher() : k0(GetRand<uint64_t>()), k1(GetRand<uint64_t>()) {}
 
-SaltedOutpointHasher::SaltedOutpointHasher() : k0(GetRand<uint64_t>()), k1(GetRand<uint64_t>()) {}
+SaltedOutpointHasher::SaltedOutpointHasher(bool deterministic) :
+    k0(deterministic ? 0x8e819f2607a18de6 : GetRand<uint64_t>()),
+    k1(deterministic ? 0xf4020d2e3983b0eb : GetRand<uint64_t>())
+{}
 
 SaltedSipHasher::SaltedSipHasher() : m_k0(GetRand<uint64_t>()), m_k1(GetRand<uint64_t>()) {}
 

src/util/hasher.h

@@ -36,7 +36,7 @@ class SaltedOutpointHasher
     const uint64_t k0, k1;
 
 public:
-    SaltedOutpointHasher();
+    SaltedOutpointHasher(bool deterministic = false);
 
     /**
      * Having the hash noexcept allows libstdc++'s unordered_map to recalculate