Remove ModifyCoins/ModifyNewCoins

Author: sipa

src/coins.cpp

@@ -60,12 +60,7 @@ size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }
 
 SaltedTxidHasher::SaltedTxidHasher() : k0(GetRand(std::numeric_limits<uint64_t>::max())), k1(GetRand(std::numeric_limits<uint64_t>::max())) {}
 
-CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), hasModifier(false), cachedCoinsUsage(0) { }
-
-CCoinsViewCache::~CCoinsViewCache()
-{
-    assert(!hasModifier);
-}
+CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), cachedCoinsUsage(0) { }
 
 size_t CCoinsViewCache::DynamicMemoryUsage() const {
     return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
@@ -98,62 +93,6 @@ bool CCoinsViewCache::GetCoins(const uint256 &txid, CCoins &coins) const {
     return false;
 }
 
-CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
-    assert(!hasModifier);
-    std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
-    size_t cachedCoinUsage = 0;
-    if (ret.second) {
-        if (!base->GetCoins(txid, ret.first->second.coins)) {
-            // The parent view does not have this entry; mark it as fresh.
-            ret.first->second.coins.Clear();
-            ret.first->second.flags = CCoinsCacheEntry::FRESH;
-        } else if (ret.first->second.coins.IsPruned()) {
-            // The parent view only has a pruned entry for this; mark it as fresh.
-            ret.first->second.flags = CCoinsCacheEntry::FRESH;
-        }
-    } else {
-        cachedCoinUsage = ret.first->second.coins.DynamicMemoryUsage();
-    }
-    // Assume that whenever ModifyCoins is called, the entry will be modified.
-    ret.first->second.flags |= CCoinsCacheEntry::DIRTY;
-    return CCoinsModifier(*this, ret.first, cachedCoinUsage);
-}
-
-/* ModifyNewCoins allows for faster coin modification when creating the new
- * outputs from a transaction.  It assumes that BIP 30 (no duplicate txids)
- * applies and has already been tested for (or the test is not required due to
- * BIP 34, height in coinbase).  If we can assume BIP 30 then we know that any
- * non-coinbase transaction we are adding to the UTXO must not already exist in
- * the utxo unless it is fully spent.  Thus we can check only if it exists DIRTY
- * at the current level of the cache, in which case it is not safe to mark it
- * FRESH (b/c then its spentness still needs to flushed).  If it's not dirty and
- * doesn't exist or is pruned in the current cache, we know it either doesn't
- * exist or is pruned in parent caches, which is the definition of FRESH.  The
- * exception to this is the two historical violations of BIP 30 in the chain,
- * both of which were coinbases.  We do not mark these fresh so we we can ensure
- * that they will still be properly overwritten when spent.
- */
-CCoinsModifier CCoinsViewCache::ModifyNewCoins(const uint256 &txid, bool coinbase) {
-    assert(!hasModifier);
-    std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
-    if (!coinbase) {
-        // New coins must not already exist.
-        if (!ret.first->second.coins.IsPruned())
-            throw std::logic_error("ModifyNewCoins should not find pre-existing coins on a non-coinbase unless they are pruned!");
-
-        if (!(ret.first->second.flags & CCoinsCacheEntry::DIRTY)) {
-            // If the coin is known to be pruned (have no unspent outputs) in
-            // the current view and the cache entry is not dirty, we know the
-            // coin also must be pruned in the parent view as well, so it is safe
-            // to mark this fresh.
-            ret.first->second.flags |= CCoinsCacheEntry::FRESH;
-        }
-    }
-    ret.first->second.coins.Clear();
-    ret.first->second.flags |= CCoinsCacheEntry::DIRTY;
-    return CCoinsModifier(*this, ret.first, 0);
-}
-
 void CCoinsViewCache::AddCoin(const COutPoint &outpoint, Coin&& coin, bool possible_overwrite) {
     assert(!coin.IsPruned());
     if (coin.out.scriptPubKey.IsUnspendable()) return;
@@ -257,7 +196,6 @@ void CCoinsViewCache::SetBestBlock(const uint256 &hashBlockIn) {
 }
 
 bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn) {
-    assert(!hasModifier);
     for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
         if (it->second.flags & CCoinsCacheEntry::DIRTY) { // Ignore non-dirty entries (optimization).
             CCoinsMap::iterator itUs = cacheCoins.find(it->first);
@@ -366,25 +304,6 @@ bool CCoinsViewCache::HaveInputs(const CTransaction& tx) const
     return true;
 }
 
-CCoinsModifier::CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage) : cache(cache_), it(it_), cachedCoinUsage(usage) {
-    assert(!cache.hasModifier);
-    cache.hasModifier = true;
-}
-
-CCoinsModifier::~CCoinsModifier()
-{
-    assert(cache.hasModifier);
-    cache.hasModifier = false;
-    it->second.coins.Cleanup();
-    cache.cachedCoinsUsage -= cachedCoinUsage; // Subtract the old usage
-    if ((it->second.flags & CCoinsCacheEntry::FRESH) && it->second.coins.IsPruned()) {
-        cache.cacheCoins.erase(it);
-    } else {
-        // If the coin still exists after the modification, add the new usage
-        cache.cachedCoinsUsage += it->second.coins.DynamicMemoryUsage();
-    }
-}
-
 CCoinsViewCursor::~CCoinsViewCursor()
 {
 }

src/coins.h

@@ -405,36 +405,10 @@ class CCoinsViewBacked : public CCoinsView
 };
 
 
-class CCoinsViewCache;
-
-/** 
- * A reference to a mutable cache entry. Encapsulating it allows us to run
- *  cleanup code after the modification is finished, and keeping track of
- *  concurrent modifications. 
- */
-class CCoinsModifier
-{
-private:
-    CCoinsViewCache& cache;
-    CCoinsMap::iterator it;
-    size_t cachedCoinUsage; // Cached memory usage of the CCoins object before modification
-    CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage);
-
-public:
-    CCoins* operator->() { return &it->second.coins; }
-    CCoins& operator*() { return it->second.coins; }
-    ~CCoinsModifier();
-    friend class CCoinsViewCache;
-};
-
 /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
 class CCoinsViewCache : public CCoinsViewBacked
 {
 protected:
-    /* Whether this cache has an active modifier. */
-    bool hasModifier;
-
-
     /**
      * Make mutable so that we can "fill the cache" even from Get-methods
      * declared as "const".  
@@ -447,7 +421,6 @@ class CCoinsViewCache : public CCoinsViewBacked
 
 public:
     CCoinsViewCache(CCoinsView *baseIn);
-    ~CCoinsViewCache();
 
     // Standard CCoinsView methods
     bool GetCoins(const uint256 &txid, CCoins &coins) const;
@@ -479,24 +452,6 @@ class CCoinsViewCache : public CCoinsViewBacked
      */
     const Coin AccessCoin(const COutPoint &output) const;
 
-    /**
-     * Return a modifiable reference to a CCoins. If no entry with the given
-     * txid exists, a new one is created. Simultaneous modifications are not
-     * allowed.
-     */
-    CCoinsModifier ModifyCoins(const uint256 &txid);
-
-    /**
-     * Return a modifiable reference to a CCoins. Assumes that no entry with the given
-     * txid exists and creates a new one. This saves a database access in the case where
-     * the coins were to be wiped out by FromTx anyway.  This should not be called with
-     * the 2 historical coinbase duplicate pairs because the new coins are marked fresh, and
-     * in the event the duplicate coinbase was spent before a flush, the now pruned coins
-     * would not properly overwrite the first coinbase of the pair. Simultaneous modifications
-     * are not allowed.
-     */
-    CCoinsModifier ModifyNewCoins(const uint256 &txid, bool coinbase);
-
     /**
      * Add a coin. Set potential_overwrite to true if a non-pruned version may
      * already exist.
@@ -544,8 +499,6 @@ class CCoinsViewCache : public CCoinsViewBacked
 
     const CTxOut &GetOutputFor(const CTxIn& input) const;
 
-    friend class CCoinsModifier;
-
 private:
     CCoinsMap::iterator FetchCoins(const uint256 &txid) const;