1 files changed, 20 insertions, 28 deletions

diff --git a/src/coins.h b/src/coins.h
index fadb1058cd..5a6f73652b 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -8,11 +8,11 @@
 
 #include <compressor.h>
 #include <core_memusage.h>
-#include <crypto/siphash.h>
 #include <memusage.h>
 #include <primitives/transaction.h>
 #include <serialize.h>
 #include <uint256.h>
+#include <util/hasher.h>
 
 #include <assert.h>
 #include <stdint.h>
@@ -20,6 +20,8 @@
 #include <functional>
 #include <unordered_map>
 
+class ChainstateManager;
+
 /**
  * A UTXO entry.
  *
@@ -85,33 +87,6 @@ public:
     }
 };
 
-class SaltedOutpointHasher
-{
-private:
-    /** Salt */
-    const uint64_t k0, k1;
-
-public:
-    SaltedOutpointHasher();
-
-    /**
-     * This *must* return size_t. With Boost 1.46 on 32-bit systems the
-     * unordered_map will behave unpredictably if the custom hasher returns a
-     * uint64_t, resulting in failures when syncing the chain (#4634).
-     *
-     * Having the hash noexcept allows libstdc++'s unordered_map to recalculate
-     * the hash during rehash, so it does not have to cache the value. This
-     * reduces node's memory by sizeof(size_t). The required recalculation has
-     * a slight performance penalty (around 1.6%), but this is compensated by
-     * memory savings of about 9% which allow for a larger dbcache setting.
-     *
-     * @see https://gcc.gnu.org/onlinedocs/gcc-9.2.0/libstdc++/manual/manual/unordered_associative.html
-     */
-    size_t operator()(const COutPoint& id) const noexcept {
-        return SipHashUint256Extra(k0, k1, id.hash, id.n);
-    }
-};
-
 /**
  * A Coin in one level of the coins database caching hierarchy.
  *
@@ -155,6 +130,7 @@ struct CCoinsCacheEntry
 
     CCoinsCacheEntry() : flags(0) {}
     explicit CCoinsCacheEntry(Coin&& coin_) : coin(std::move(coin_)), flags(0) {}
+    CCoinsCacheEntry(Coin&& coin_, unsigned char flag) : coin(std::move(coin_)), flags(flag) {}
 };
 
 typedef std::unordered_map<COutPoint, CCoinsCacheEntry, SaltedOutpointHasher> CCoinsMap;
@@ -293,6 +269,15 @@ public:
     void AddCoin(const COutPoint& outpoint, Coin&& coin, bool possible_overwrite);
 
     /**
+     * Emplace a coin into cacheCoins without performing any checks, marking
+     * the emplaced coin as dirty.
+     *
+     * NOT FOR GENERAL USE. Used only when loading coins from a UTXO snapshot.
+     * @sa ChainstateManager::PopulateAndValidateSnapshot()
+     */
+    void EmplaceCoinInternalDANGER(COutPoint&& outpoint, Coin&& coin);
+
+    /**
      * Spend a coin. Pass moveto in order to get the deleted data.
      * If no unspent output exists for the passed outpoint, this call
      * has no effect.
@@ -321,6 +306,13 @@ public:
     //! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
     bool HaveInputs(const CTransaction& tx) const;
 
+    //! Force a reallocation of the cache map. This is required when downsizing
+    //! the cache because the map's allocator may be hanging onto a lot of
+    //! memory despite having called .clear().
+    //!
+    //! See: https://stackoverflow.com/questions/42114044/how-to-release-unordered-map-memory
+    void ReallocateCache();
+
 private:
     /**
      * @note this is marked const, but may actually append to `cacheCoins`, increasing