src/coins.h

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2014 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #ifndef BITCOIN_COINS_H
   7 #define BITCOIN_COINS_H
   8
   9 #include "compressor.h"
  10 #include "core_memusage.h"
  11 #include "memusage.h"
  12 #include "serialize.h"
  13 #include "uint256.h"
  14
  15 #include <assert.h>
  16 #include <stdint.h>
  17
  18 #include <boost/foreach.hpp>
  19 #include <boost/unordered_map.hpp>
  20
  21 /**
  22  * Pruned version of CTransaction: only retains metadata and unspent transaction outputs
  23  *
  24  * Serialized format:
  25  * - VARINT(nVersion)
  26  * - VARINT(nCode)
  27  * - unspentness bitvector, for vout[2] and further; least significant byte first
  28  * - the non-spent CTxOuts (via CTxOutCompressor)
  29  * - VARINT(nHeight)
  30  *
  31  * The nCode value consists of:
  32  * - bit 1: IsCoinBase()
  33  * - bit 2: vout[0] is not spent
  34  * - bit 4: vout[1] is not spent
  35  * - The higher bits encode N, the number of non-zero bytes in the following bitvector.
  36  *   - In case both bit 2 and bit 4 are unset, they encode N-1, as there must be at
  37  *     least one non-spent output).
  38  *
  39  * Example: 0104835800816115944e077fe7c803cfa57f29b36bf87c1d358bb85e
  40  *          <><><--------------------------------------------><---->
  41  *          |  \                  |                             /
  42  *    version   code             vout[1]                  height
  43  *
  44  *    - version = 1
  45  *    - code = 4 (vout[1] is not spent, and 0 non-zero bytes of bitvector follow)
  46  *    - unspentness bitvector: as 0 non-zero bytes follow, it has length 0
  47  *    - vout[1]: 835800816115944e077fe7c803cfa57f29b36bf87c1d35
  48  *               * 8358: compact amount representation for 60000000000 (600 BTC)
  49  *               * 00: special txout type pay-to-pubkey-hash
  50  *               * 816115944e077fe7c803cfa57f29b36bf87c1d35: address uint160
  51  *    - height = 203998
  52  *
  53  *
  54  * Example: 0109044086ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4eebbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa486af3b
  55  *          <><><--><--------------------------------------------------><----------------------------------------------><---->
  56  *         /  \   \                     |                                                           |                     /
  57  *  version  code  unspentness       vout[4]                                                     vout[16]           height
  58  *
  59  *  - version = 1
  60  *  - code = 9 (coinbase, neither vout[0] or vout[1] are unspent,
  61  *                2 (1, +1 because both bit 2 and bit 4 are unset) non-zero bitvector bytes follow)
  62  *  - unspentness bitvector: bits 2 (0x04) and 14 (0x4000) are set, so vout[2+2] and vout[14+2] are unspent
  63  *  - vout[4]: 86ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4ee
  64  *             * 86ef97d579: compact amount representation for 234925952 (2.35 BTC)
  65  *             * 00: special txout type pay-to-pubkey-hash
  66  *             * 61b01caab50f1b8e9c50a5057eb43c2d9563a4ee: address uint160
  67  *  - vout[16]: bbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa4
  68  *              * bbd123: compact amount representation for 110397 (0.001 BTC)
  69  *              * 00: special txout type pay-to-pubkey-hash
  70  *              * 8c988f1a4a4de2161e0f50aac7f17e7f9555caa4: address uint160
  71  *  - height = 120891
  72  */
  73 class CCoins
  74 {
  75 public:
  76     //! whether transaction is a coinbase
  77     bool fCoinBase;
  78
  79     //! unspent transaction outputs; spent outputs are .IsNull(); spent outputs at the end of the array are dropped
  80     std::vector<CTxOut> vout;
  81
  82     //! at which height this transaction was included in the active block chain
  83     int nHeight;
  84
  85     //! version of the CTransaction; accesses to this value should probably check for nHeight as well,
  86     //! as new tx version will probably only be introduced at certain heights
  87     int nVersion;
  88
  89     void FromTx(const CTransaction &tx, int nHeightIn) {
  90         fCoinBase = tx.IsCoinBase();
  91         vout = tx.vout;
  92         nHeight = nHeightIn;
  93         nVersion = tx.nVersion;
  94         ClearUnspendable();
  95     }
  96
  97     //! construct a CCoins from a CTransaction, at a given height
  98     CCoins(const CTransaction &tx, int nHeightIn) {
  99         FromTx(tx, nHeightIn);
 100     }
 101
 102     void Clear() {
 103         fCoinBase = false;
 104         std::vector<CTxOut>().swap(vout);
 105         nHeight = 0;
 106         nVersion = 0;
 107     }
 108
 109     //! empty constructor
 110     CCoins() : fCoinBase(false), vout(0), nHeight(0), nVersion(0) { }
 111
 112     //!remove spent outputs at the end of vout
 113     void Cleanup() {
 114         while (vout.size() > 0 && vout.back().IsNull())
 115             vout.pop_back();
 116         if (vout.empty())
 117             std::vector<CTxOut>().swap(vout);
 118     }
 119
 120     void ClearUnspendable() {
 121         BOOST_FOREACH(CTxOut &txout, vout) {
 122             if (txout.scriptPubKey.IsUnspendable())
 123                 txout.SetNull();
 124         }
 125         Cleanup();
 126     }
 127
 128     void swap(CCoins &to) {
 129         std::swap(to.fCoinBase, fCoinBase);
 130         to.vout.swap(vout);
 131         std::swap(to.nHeight, nHeight);
 132         std::swap(to.nVersion, nVersion);
 133     }
 134
 135     //! equality test
 136     friend bool operator==(const CCoins &a, const CCoins &b) {
 137          // Empty CCoins objects are always equal.
 138          if (a.IsPruned() && b.IsPruned())
 139              return true;
 140          return a.fCoinBase == b.fCoinBase &&
 141                 a.nHeight == b.nHeight &&
 142                 a.nVersion == b.nVersion &&
 143                 a.vout == b.vout;
 144     }
 145     friend bool operator!=(const CCoins &a, const CCoins &b) {
 146         return !(a == b);
 147     }
 148
 149     void CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const;
 150
 151     bool IsCoinBase() const {
 152         return fCoinBase;
 153     }
 154
 155     unsigned int GetSerializeSize(int nType, int nVersion) const {
 156         unsigned int nSize = 0;
 157         unsigned int nMaskSize = 0, nMaskCode = 0;
 158         CalcMaskSize(nMaskSize, nMaskCode);
 159         bool fFirst = vout.size() > 0 && !vout[0].IsNull();
 160         bool fSecond = vout.size() > 1 && !vout[1].IsNull();
 161         assert(fFirst || fSecond || nMaskCode);
 162         unsigned int nCode = 8*(nMaskCode - (fFirst || fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
 163         // version
 164         nSize += ::GetSerializeSize(VARINT(this->nVersion), nType, nVersion);
 165         // size of header code
 166         nSize += ::GetSerializeSize(VARINT(nCode), nType, nVersion);
 167         // spentness bitmask
 168         nSize += nMaskSize;
 169         // txouts themself
 170         for (unsigned int i = 0; i < vout.size(); i++)
 171             if (!vout[i].IsNull())
 172                 nSize += ::GetSerializeSize(CTxOutCompressor(REF(vout[i])), nType, nVersion);
 173         // height
 174         nSize += ::GetSerializeSize(VARINT(nHeight), nType, nVersion);
 175         return nSize;
 176     }
 177
 178     template<typename Stream>
 179     void Serialize(Stream &s, int nType, int nVersion) const {
 180         unsigned int nMaskSize = 0, nMaskCode = 0;
 181         CalcMaskSize(nMaskSize, nMaskCode);
 182         bool fFirst = vout.size() > 0 && !vout[0].IsNull();
 183         bool fSecond = vout.size() > 1 && !vout[1].IsNull();
 184         assert(fFirst || fSecond || nMaskCode);
 185         unsigned int nCode = 8*(nMaskCode - (fFirst || fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
 186         // version
 187         ::Serialize(s, VARINT(this->nVersion), nType, nVersion);
 188         // header code
 189         ::Serialize(s, VARINT(nCode), nType, nVersion);
 190         // spentness bitmask
 191         for (unsigned int b = 0; b<nMaskSize; b++) {
 192             unsigned char chAvail = 0;
 193             for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++)
 194                 if (!vout[2+b*8+i].IsNull())
 195                     chAvail |= (1 << i);
 196             ::Serialize(s, chAvail, nType, nVersion);
 197         }
 198         // txouts themself
 199         for (unsigned int i = 0; i < vout.size(); i++) {
 200             if (!vout[i].IsNull())
 201                 ::Serialize(s, CTxOutCompressor(REF(vout[i])), nType, nVersion);
 202         }
 203         // coinbase height
 204         ::Serialize(s, VARINT(nHeight), nType, nVersion);
 205     }
 206
 207     template<typename Stream>
 208     void Unserialize(Stream &s, int nType, int nVersion) {
 209         unsigned int nCode = 0;
 210         // version
 211         ::Unserialize(s, VARINT(this->nVersion), nType, nVersion);
 212         // header code
 213         ::Unserialize(s, VARINT(nCode), nType, nVersion);
 214         fCoinBase = nCode & 1;
 215         std::vector<bool> vAvail(2, false);
 216         vAvail[0] = (nCode & 2) != 0;
 217         vAvail[1] = (nCode & 4) != 0;
 218         unsigned int nMaskCode = (nCode / 8) + ((nCode & 6) != 0 ? 0 : 1);
 219         // spentness bitmask
 220         while (nMaskCode > 0) {
 221             unsigned char chAvail = 0;
 222             ::Unserialize(s, chAvail, nType, nVersion);
 223             for (unsigned int p = 0; p < 8; p++) {
 224                 bool f = (chAvail & (1 << p)) != 0;
 225                 vAvail.push_back(f);
 226             }
 227             if (chAvail != 0)
 228                 nMaskCode--;
 229         }
 230         // txouts themself
 231         vout.assign(vAvail.size(), CTxOut());
 232         for (unsigned int i = 0; i < vAvail.size(); i++) {
 233             if (vAvail[i])
 234                 ::Unserialize(s, REF(CTxOutCompressor(vout[i])), nType, nVersion);
 235         }
 236         // coinbase height
 237         ::Unserialize(s, VARINT(nHeight), nType, nVersion);
 238         Cleanup();
 239     }
 240
 241     //! mark a vout spent
 242     bool Spend(uint32_t nPos);
 243
 244     //! check whether a particular output is still available
 245     bool IsAvailable(unsigned int nPos) const {
 246         return (nPos < vout.size() && !vout[nPos].IsNull());
 247     }
 248
 249     //! check whether the entire CCoins is spent
 250     //! note that only !IsPruned() CCoins can be serialized
 251     bool IsPruned() const {
 252         BOOST_FOREACH(const CTxOut &out, vout)
 253             if (!out.IsNull())
 254                 return false;
 255         return true;
 256     }
 257
 258     size_t DynamicMemoryUsage() const {
 259         size_t ret = memusage::DynamicUsage(vout);
 260         BOOST_FOREACH(const CTxOut &out, vout) {
 261             ret += RecursiveDynamicUsage(out.scriptPubKey);
 262         }
 263         return ret;
 264     }
 265 };
 266
 267 class CCoinsKeyHasher
 268 {
 269 private:
 270     uint256 salt;
 271
 272 public:
 273     CCoinsKeyHasher();
 274
 275     /**
 276      * This *must* return size_t. With Boost 1.46 on 32-bit systems the
 277      * unordered_map will behave unpredictably if the custom hasher returns a
 278      * uint64_t, resulting in failures when syncing the chain (#4634).
 279      */
 280     size_t operator()(const uint256& key) const {
 281         return key.GetHash(salt);
 282     }
 283 };
 284
 285 struct CCoinsCacheEntry
 286 {
 287     CCoins coins; // The actual cached data.
 288     unsigned char flags;
 289
 290     enum Flags {
 291         DIRTY = (1 << 0), // This cache entry is potentially different from the version in the parent view.
 292         FRESH = (1 << 1), // The parent view does not have this entry (or it is pruned).
 293     };
 294
 295     CCoinsCacheEntry() : coins(), flags(0) {}
 296 };
 297
 298 typedef boost::unordered_map<uint256, CCoinsCacheEntry, CCoinsKeyHasher> CCoinsMap;
 299
 300 struct CCoinsStats
 301 {
 302     int nHeight;
 303     uint256 hashBlock;
 304     uint64_t nTransactions;
 305     uint64_t nTransactionOutputs;
 306     uint64_t nSerializedSize;
 307     uint256 hashSerialized;
 308     CAmount nTotalAmount;
 309
 310     CCoinsStats() : nHeight(0), nTransactions(0), nTransactionOutputs(0), nSerializedSize(0), nTotalAmount(0) {}
 311 };
 312
 313
 314 /** Abstract view on the open txout dataset. */
 315 class CCoinsView
 316 {
 317 public:
 318     //! Retrieve the CCoins (unspent transaction outputs) for a given txid
 319     virtual bool GetCoins(const uint256 &txid, CCoins &coins) const;
 320
 321     //! Just check whether we have data for a given txid.
 322     //! This may (but cannot always) return true for fully spent transactions
 323     virtual bool HaveCoins(const uint256 &txid) const;
 324
 325     //! Retrieve the block hash whose state this CCoinsView currently represents
 326     virtual uint256 GetBestBlock() const;
 327
 328     //! Do a bulk modification (multiple CCoins changes + BestBlock change).
 329     //! The passed mapCoins can be modified.
 330     virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 331
 332     //! Calculate statistics about the unspent transaction output set
 333     virtual bool GetStats(CCoinsStats &stats) const;
 334
 335     //! As we use CCoinsViews polymorphically, have a virtual destructor
 336     virtual ~CCoinsView() {}
 337 };
 338
 339
 340 /** CCoinsView backed by another CCoinsView */
 341 class CCoinsViewBacked : public CCoinsView
 342 {
 343 protected:
 344     CCoinsView *base;
 345
 346 public:
 347     CCoinsViewBacked(CCoinsView *viewIn);
 348     bool GetCoins(const uint256 &txid, CCoins &coins) const;
 349     bool HaveCoins(const uint256 &txid) const;
 350     uint256 GetBestBlock() const;
 351     void SetBackend(CCoinsView &viewIn);
 352     bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 353     bool GetStats(CCoinsStats &stats) const;
 354 };
 355
 356
 357 class CCoinsViewCache;
 358
 359 /**
 360  * A reference to a mutable cache entry. Encapsulating it allows us to run
 361  *  cleanup code after the modification is finished, and keeping track of
 362  *  concurrent modifications.
 363  */
 364 class CCoinsModifier
 365 {
 366 private:
 367     CCoinsViewCache& cache;
 368     CCoinsMap::iterator it;
 369     size_t cachedCoinUsage; // Cached memory usage of the CCoins object before modification
 370     CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage);
 371
 372 public:
 373     CCoins* operator->() { return &it->second.coins; }
 374     CCoins& operator*() { return it->second.coins; }
 375     ~CCoinsModifier();
 376     friend class CCoinsViewCache;
 377 };
 378
 379 /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
 380 class CCoinsViewCache : public CCoinsViewBacked
 381 {
 382 protected:
 383     /* Whether this cache has an active modifier. */
 384     bool hasModifier;
 385
 386
 387     /**
 388      * Make mutable so that we can "fill the cache" even from Get-methods
 389      * declared as "const".
 390      */
 391     mutable uint256 hashBlock;
 392     mutable CCoinsMap cacheCoins;
 393
 394     /* Cached dynamic memory usage for the inner CCoins objects. */
 395     mutable size_t cachedCoinsUsage;
 396
 397 public:
 398     CCoinsViewCache(CCoinsView *baseIn);
 399     ~CCoinsViewCache();
 400
 401     // Standard CCoinsView methods
 402     bool GetCoins(const uint256 &txid, CCoins &coins) const;
 403     bool HaveCoins(const uint256 &txid) const;
 404     uint256 GetBestBlock() const;
 405     void SetBestBlock(const uint256 &hashBlock);
 406     bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 407
 408     /**
 409      * Return a pointer to CCoins in the cache, or NULL if not found. This is
 410      * more efficient than GetCoins. Modifications to other cache entries are
 411      * allowed while accessing the returned pointer.
 412      */
 413     const CCoins* AccessCoins(const uint256 &txid) const;
 414
 415     /**
 416      * Return a modifiable reference to a CCoins. If no entry with the given
 417      * txid exists, a new one is created. Simultaneous modifications are not
 418      * allowed.
 419      */
 420     CCoinsModifier ModifyCoins(const uint256 &txid);
 421
 422     /**
 423      * Push the modifications applied to this cache to its base.
 424      * Failure to call this method before destruction will cause the changes to be forgotten.
 425      * If false is returned, the state of this cache (and its backing view) will be undefined.
 426      */
 427     bool Flush();
 428
 429     //! Calculate the size of the cache (in number of transactions)
 430     unsigned int GetCacheSize() const;
 431
 432     //! Calculate the size of the cache (in bytes)
 433     size_t DynamicMemoryUsage() const;
 434
 435     /**
 436      * Amount of bitcoins coming in to a transaction
 437      * Note that lightweight clients may not know anything besides the hash of previous transactions,
 438      * so may not be able to calculate this.
 439      *
 440      * @param[in] tx    transaction for which we are checking input total
 441      * @return  Sum of value of all inputs (scriptSigs)
 442      */
 443     CAmount GetValueIn(const CTransaction& tx) const;
 444
 445     //! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
 446     bool HaveInputs(const CTransaction& tx) const;
 447
 448     //! Return priority of tx at height nHeight
 449     double GetPriority(const CTransaction &tx, int nHeight) const;
 450
 451     const CTxOut &GetOutputFor(const CTxIn& input) const;
 452
 453     friend class CCoinsModifier;
 454
 455 private:
 456     CCoinsMap::iterator FetchCoins(const uint256 &txid);
 457     CCoinsMap::const_iterator FetchCoins(const uint256 &txid) const;
 458
 459     /**
 460      * By making the copy constructor private, we prevent accidentally using it when one intends to create a cache on top of a base cache.
 461      */
 462     CCoinsViewCache(const CCoinsViewCache &);
 463 };
 464
 465 #endif // BITCOIN_COINS_H