src/coins.cpp

   1 // Copyright (c) 2012-2014 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include "coins.h"
   6
   7 #include "memusage.h"
   8 #include "random.h"
   9
  10 #include <assert.h>
  11
  12 /**
  13  * calculate number of bytes for the bitmask, and its number of non-zero bytes
  14  * each bit in the bitmask represents the availability of one output, but the
  15  * availabilities of the first two outputs are encoded separately
  16  */
  17 void CCoins::CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const {
  18     unsigned int nLastUsedByte = 0;
  19     for (unsigned int b = 0; 2+b*8 < vout.size(); b++) {
  20         bool fZero = true;
  21         for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++) {
  22             if (!vout[2+b*8+i].IsNull()) {
  23                 fZero = false;
  24                 continue;
  25             }
  26         }
  27         if (!fZero) {
  28             nLastUsedByte = b + 1;
  29             nNonzeroBytes++;
  30         }
  31     }
  32     nBytes += nLastUsedByte;
  33 }
  34
  35 bool CCoins::Spend(uint32_t nPos)
  36 {
  37     if (nPos >= vout.size() || vout[nPos].IsNull())
  38         return false;
  39     vout[nPos].SetNull();
  40     Cleanup();
  41     return true;
  42 }
  43
  44 bool CCoinsView::GetCoins(const uint256 &txid, CCoins &coins) const { return false; }
  45 bool CCoinsView::HaveCoins(const uint256 &txid) const { return false; }
  46 uint256 CCoinsView::GetBestBlock() const { return uint256(); }
  47 bool CCoinsView::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return false; }
  48 bool CCoinsView::GetStats(CCoinsStats &stats) const { return false; }
  49
  50
  51 CCoinsViewBacked::CCoinsViewBacked(CCoinsView *viewIn) : base(viewIn) { }
  52 bool CCoinsViewBacked::GetCoins(const uint256 &txid, CCoins &coins) const { return base->GetCoins(txid, coins); }
  53 bool CCoinsViewBacked::HaveCoins(const uint256 &txid) const { return base->HaveCoins(txid); }
  54 uint256 CCoinsViewBacked::GetBestBlock() const { return base->GetBestBlock(); }
  55 void CCoinsViewBacked::SetBackend(CCoinsView &viewIn) { base = &viewIn; }
  56 bool CCoinsViewBacked::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) { return base->BatchWrite(mapCoins, hashBlock); }
  57 bool CCoinsViewBacked::GetStats(CCoinsStats &stats) const { return base->GetStats(stats); }
  58
  59 CCoinsKeyHasher::CCoinsKeyHasher() : salt(GetRandHash()) {}
  60
  61 CCoinsViewCache::CCoinsViewCache(CCoinsView *baseIn) : CCoinsViewBacked(baseIn), hasModifier(false), cachedCoinsUsage(0) { }
  62
  63 CCoinsViewCache::~CCoinsViewCache()
  64 {
  65     assert(!hasModifier);
  66 }
  67
  68 size_t CCoinsViewCache::DynamicMemoryUsage() const {
  69     return memusage::DynamicUsage(cacheCoins) + cachedCoinsUsage;
  70 }
  71
  72 CCoinsMap::const_iterator CCoinsViewCache::FetchCoins(const uint256 &txid) const {
  73     CCoinsMap::iterator it = cacheCoins.find(txid);
  74     if (it != cacheCoins.end())
  75         return it;
  76     CCoins tmp;
  77     if (!base->GetCoins(txid, tmp))
  78         return cacheCoins.end();
  79     CCoinsMap::iterator ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry())).first;
  80     tmp.swap(ret->second.coins);
  81     if (ret->second.coins.IsPruned()) {
  82         // The parent only has an empty entry for this txid; we can consider our
  83         // version as fresh.
  84         ret->second.flags = CCoinsCacheEntry::FRESH;
  85     }
  86     cachedCoinsUsage += memusage::DynamicUsage(ret->second.coins);
  87     return ret;
  88 }
  89
  90 bool CCoinsViewCache::GetCoins(const uint256 &txid, CCoins &coins) const {
  91     CCoinsMap::const_iterator it = FetchCoins(txid);
  92     if (it != cacheCoins.end()) {
  93         coins = it->second.coins;
  94         return true;
  95     }
  96     return false;
  97 }
  98
  99 CCoinsModifier CCoinsViewCache::ModifyCoins(const uint256 &txid) {
 100     assert(!hasModifier);
 101     std::pair<CCoinsMap::iterator, bool> ret = cacheCoins.insert(std::make_pair(txid, CCoinsCacheEntry()));
 102     size_t cachedCoinUsage = 0;
 103     if (ret.second) {
 104         if (!base->GetCoins(txid, ret.first->second.coins)) {
 105             // The parent view does not have this entry; mark it as fresh.
 106             ret.first->second.coins.Clear();
 107             ret.first->second.flags = CCoinsCacheEntry::FRESH;
 108         } else if (ret.first->second.coins.IsPruned()) {
 109             // The parent view only has a pruned entry for this; mark it as fresh.
 110             ret.first->second.flags = CCoinsCacheEntry::FRESH;
 111         }
 112     } else {
 113         cachedCoinUsage = memusage::DynamicUsage(ret.first->second.coins);
 114     }
 115     // Assume that whenever ModifyCoins is called, the entry will be modified.
 116     ret.first->second.flags |= CCoinsCacheEntry::DIRTY;
 117     return CCoinsModifier(*this, ret.first, cachedCoinUsage);
 118 }
 119
 120 const CCoins* CCoinsViewCache::AccessCoins(const uint256 &txid) const {
 121     CCoinsMap::const_iterator it = FetchCoins(txid);
 122     if (it == cacheCoins.end()) {
 123         return NULL;
 124     } else {
 125         return &it->second.coins;
 126     }
 127 }
 128
 129 bool CCoinsViewCache::HaveCoins(const uint256 &txid) const {
 130     CCoinsMap::const_iterator it = FetchCoins(txid);
 131     // We're using vtx.empty() instead of IsPruned here for performance reasons,
 132     // as we only care about the case where a transaction was replaced entirely
 133     // in a reorganization (which wipes vout entirely, as opposed to spending
 134     // which just cleans individual outputs).
 135     return (it != cacheCoins.end() && !it->second.coins.vout.empty());
 136 }
 137
 138 uint256 CCoinsViewCache::GetBestBlock() const {
 139     if (hashBlock.IsNull())
 140         hashBlock = base->GetBestBlock();
 141     return hashBlock;
 142 }
 143
 144 void CCoinsViewCache::SetBestBlock(const uint256 &hashBlockIn) {
 145     hashBlock = hashBlockIn;
 146 }
 147
 148 bool CCoinsViewCache::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlockIn) {
 149     assert(!hasModifier);
 150     for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
 151         if (it->second.flags & CCoinsCacheEntry::DIRTY) { // Ignore non-dirty entries (optimization).
 152             CCoinsMap::iterator itUs = cacheCoins.find(it->first);
 153             if (itUs == cacheCoins.end()) {
 154                 if (!it->second.coins.IsPruned()) {
 155                     // The parent cache does not have an entry, while the child
 156                     // cache does have (a non-pruned) one. Move the data up, and
 157                     // mark it as fresh (if the grandparent did have it, we
 158                     // would have pulled it in at first GetCoins).
 159                     assert(it->second.flags & CCoinsCacheEntry::FRESH);
 160                     CCoinsCacheEntry& entry = cacheCoins[it->first];
 161                     entry.coins.swap(it->second.coins);
 162                     cachedCoinsUsage += memusage::DynamicUsage(entry.coins);
 163                     entry.flags = CCoinsCacheEntry::DIRTY | CCoinsCacheEntry::FRESH;
 164                 }
 165             } else {
 166                 if ((itUs->second.flags & CCoinsCacheEntry::FRESH) && it->second.coins.IsPruned()) {
 167                     // The grandparent does not have an entry, and the child is
 168                     // modified and being pruned. This means we can just delete
 169                     // it from the parent.
 170                     cachedCoinsUsage -= memusage::DynamicUsage(itUs->second.coins);
 171                     cacheCoins.erase(itUs);
 172                 } else {
 173                     // A normal modification.
 174                     cachedCoinsUsage -= memusage::DynamicUsage(itUs->second.coins);
 175                     itUs->second.coins.swap(it->second.coins);
 176                     cachedCoinsUsage += memusage::DynamicUsage(itUs->second.coins);
 177                     itUs->second.flags |= CCoinsCacheEntry::DIRTY;
 178                 }
 179             }
 180         }
 181         CCoinsMap::iterator itOld = it++;
 182         mapCoins.erase(itOld);
 183     }
 184     hashBlock = hashBlockIn;
 185     return true;
 186 }
 187
 188 bool CCoinsViewCache::Flush() {
 189     bool fOk = base->BatchWrite(cacheCoins, hashBlock);
 190     cacheCoins.clear();
 191     cachedCoinsUsage = 0;
 192     return fOk;
 193 }
 194
 195 unsigned int CCoinsViewCache::GetCacheSize() const {
 196     return cacheCoins.size();
 197 }
 198
 199 const CTxOut &CCoinsViewCache::GetOutputFor(const CTxIn& input) const
 200 {
 201     const CCoins* coins = AccessCoins(input.prevout.hash);
 202     assert(coins && coins->IsAvailable(input.prevout.n));
 203     return coins->vout[input.prevout.n];
 204 }
 205
 206 CAmount CCoinsViewCache::GetValueIn(const CTransaction& tx) const
 207 {
 208     if (tx.IsCoinBase())
 209         return 0;
 210
 211     CAmount nResult = 0;
 212     for (unsigned int i = 0; i < tx.vin.size(); i++)
 213         nResult += GetOutputFor(tx.vin[i]).nValue;
 214
 215     return nResult;
 216 }
 217
 218 bool CCoinsViewCache::HaveInputs(const CTransaction& tx) const
 219 {
 220     if (!tx.IsCoinBase()) {
 221         for (unsigned int i = 0; i < tx.vin.size(); i++) {
 222             const COutPoint &prevout = tx.vin[i].prevout;
 223             const CCoins* coins = AccessCoins(prevout.hash);
 224             if (!coins || !coins->IsAvailable(prevout.n)) {
 225                 return false;
 226             }
 227         }
 228     }
 229     return true;
 230 }
 231
 232 double CCoinsViewCache::GetPriority(const CTransaction &tx, int nHeight) const
 233 {
 234     if (tx.IsCoinBase())
 235         return 0.0;
 236     double dResult = 0.0;
 237     BOOST_FOREACH(const CTxIn& txin, tx.vin)
 238     {
 239         const CCoins* coins = AccessCoins(txin.prevout.hash);
 240         assert(coins);
 241         if (!coins->IsAvailable(txin.prevout.n)) continue;
 242         if (coins->nHeight < nHeight) {
 243             dResult += coins->vout[txin.prevout.n].nValue * (nHeight-coins->nHeight);
 244         }
 245     }
 246     return tx.ComputePriority(dResult);
 247 }
 248
 249 CCoinsModifier::CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage) : cache(cache_), it(it_), cachedCoinUsage(usage) {
 250     assert(!cache.hasModifier);
 251     cache.hasModifier = true;
 252 }
 253
 254 CCoinsModifier::~CCoinsModifier()
 255 {
 256     assert(cache.hasModifier);
 257     cache.hasModifier = false;
 258     it->second.coins.Cleanup();
 259     cache.cachedCoinsUsage -= cachedCoinUsage; // Subtract the old usage
 260     if ((it->second.flags & CCoinsCacheEntry::FRESH) && it->second.coins.IsPruned()) {
 261         cache.cacheCoins.erase(it);
 262     } else {
 263         // If the coin still exists after the modification, add the new usage
 264         cache.cachedCoinsUsage += memusage::DynamicUsage(it->second.coins);
 265     }
 266 }