src/coins.h

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2016 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 "hash.h"
  12 #include "memusage.h"
  13 #include "serialize.h"
  14 #include "uint256.h"
  15
  16 #include <assert.h>
  17 #include <stdint.h>
  18
  19 #include <boost/foreach.hpp>
  20 #include <boost/unordered_map.hpp>
  21
  22 /**
  23  * Pruned version of CTransaction: only retains metadata and unspent transaction outputs
  24  *
  25  * Serialized format:
  26  * - VARINT(nVersion)
  27  * - VARINT(nCode)
  28  * - unspentness bitvector, for vout[2] and further; least significant byte first
  29  * - the non-spent CTxOuts (via CTxOutCompressor)
  30  * - VARINT(nHeight)
  31  *
  32  * The nCode value consists of:
  33  * - bit 0: IsCoinBase()
  34  * - bit 1: vout[0] is not spent
  35  * - bit 2: vout[1] is not spent
  36  * - The higher bits encode N, the number of non-zero bytes in the following bitvector.
  37  *   - In case both bit 1 and bit 2 are unset, they encode N-1, as there must be at
  38  *     least one non-spent output).
  39  *
  40  * Example: 0104835800816115944e077fe7c803cfa57f29b36bf87c1d358bb85e
  41  *          <><><--------------------------------------------><---->
  42  *          |  \                  |                             /
  43  *    version   code             vout[1]                  height
  44  *
  45  *    - version = 1
  46  *    - code = 4 (vout[1] is not spent, and 0 non-zero bytes of bitvector follow)
  47  *    - unspentness bitvector: as 0 non-zero bytes follow, it has length 0
  48  *    - vout[1]: 835800816115944e077fe7c803cfa57f29b36bf87c1d35
  49  *               * 8358: compact amount representation for 60000000000 (600 BTC)
  50  *               * 00: special txout type pay-to-pubkey-hash
  51  *               * 816115944e077fe7c803cfa57f29b36bf87c1d35: address uint160
  52  *    - height = 203998
  53  *
  54  *
  55  * Example: 0109044086ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4eebbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa486af3b
  56  *          <><><--><--------------------------------------------------><----------------------------------------------><---->
  57  *         /  \   \                     |                                                           |                     /
  58  *  version  code  unspentness       vout[4]                                                     vout[16]           height
  59  *
  60  *  - version = 1
  61  *  - code = 9 (coinbase, neither vout[0] or vout[1] are unspent,
  62  *                2 (1, +1 because both bit 1 and bit 2 are unset) non-zero bitvector bytes follow)
  63  *  - unspentness bitvector: bits 2 (0x04) and 14 (0x4000) are set, so vout[2+2] and vout[14+2] are unspent
  64  *  - vout[4]: 86ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4ee
  65  *             * 86ef97d579: compact amount representation for 234925952 (2.35 BTC)
  66  *             * 00: special txout type pay-to-pubkey-hash
  67  *             * 61b01caab50f1b8e9c50a5057eb43c2d9563a4ee: address uint160
  68  *  - vout[16]: bbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa4
  69  *              * bbd123: compact amount representation for 110397 (0.001 BTC)
  70  *              * 00: special txout type pay-to-pubkey-hash
  71  *              * 8c988f1a4a4de2161e0f50aac7f17e7f9555caa4: address uint160
  72  *  - height = 120891
  73  */
  74 class CCoins
  75 {
  76 public:
  77     //! whether transaction is a coinbase
  78     bool fCoinBase;
  79
  80     //! unspent transaction outputs; spent outputs are .IsNull(); spent outputs at the end of the array are dropped
  81     std::vector<CTxOut> vout;
  82
  83     //! at which height this transaction was included in the active block chain
  84     int nHeight;
  85
  86     //! version of the CTransaction; accesses to this value should probably check for nHeight as well,
  87     //! as new tx version will probably only be introduced at certain heights
  88     int nVersion;
  89
  90     void FromTx(const CTransaction &tx, int nHeightIn) {
  91         fCoinBase = tx.IsCoinBase();
  92         vout = tx.vout;
  93         nHeight = nHeightIn;
  94         nVersion = tx.nVersion;
  95         ClearUnspendable();
  96     }
  97
  98     //! construct a CCoins from a CTransaction, at a given height
  99     CCoins(const CTransaction &tx, int nHeightIn) {
 100         FromTx(tx, nHeightIn);
 101     }
 102
 103     void Clear() {
 104         fCoinBase = false;
 105         std::vector<CTxOut>().swap(vout);
 106         nHeight = 0;
 107         nVersion = 0;
 108     }
 109
 110     //! empty constructor
 111     CCoins() : fCoinBase(false), vout(0), nHeight(0), nVersion(0) { }
 112
 113     //!remove spent outputs at the end of vout
 114     void Cleanup() {
 115         while (vout.size() > 0 && vout.back().IsNull())
 116             vout.pop_back();
 117         if (vout.empty())
 118             std::vector<CTxOut>().swap(vout);
 119     }
 120
 121     void ClearUnspendable() {
 122         BOOST_FOREACH(CTxOut &txout, vout) {
 123             if (txout.scriptPubKey.IsUnspendable())
 124                 txout.SetNull();
 125         }
 126         Cleanup();
 127     }
 128
 129     void swap(CCoins &to) {
 130         std::swap(to.fCoinBase, fCoinBase);
 131         to.vout.swap(vout);
 132         std::swap(to.nHeight, nHeight);
 133         std::swap(to.nVersion, nVersion);
 134     }
 135
 136     //! equality test
 137     friend bool operator==(const CCoins &a, const CCoins &b) {
 138          // Empty CCoins objects are always equal.
 139          if (a.IsPruned() && b.IsPruned())
 140              return true;
 141          return a.fCoinBase == b.fCoinBase &&
 142                 a.nHeight == b.nHeight &&
 143                 a.nVersion == b.nVersion &&
 144                 a.vout == b.vout;
 145     }
 146     friend bool operator!=(const CCoins &a, const CCoins &b) {
 147         return !(a == b);
 148     }
 149
 150     void CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const;
 151
 152     bool IsCoinBase() const {
 153         return fCoinBase;
 154     }
 155
 156     template<typename Stream>
 157     void Serialize(Stream &s) const {
 158         unsigned int nMaskSize = 0, nMaskCode = 0;
 159         CalcMaskSize(nMaskSize, nMaskCode);
 160         bool fFirst = vout.size() > 0 && !vout[0].IsNull();
 161         bool fSecond = vout.size() > 1 && !vout[1].IsNull();
 162         assert(fFirst || fSecond || nMaskCode);
 163         unsigned int nCode = 8*(nMaskCode - (fFirst || fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
 164         // version
 165         ::Serialize(s, VARINT(this->nVersion));
 166         // header code
 167         ::Serialize(s, VARINT(nCode));
 168         // spentness bitmask
 169         for (unsigned int b = 0; b<nMaskSize; b++) {
 170             unsigned char chAvail = 0;
 171             for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++)
 172                 if (!vout[2+b*8+i].IsNull())
 173                     chAvail |= (1 << i);
 174             ::Serialize(s, chAvail);
 175         }
 176         // txouts themself
 177         for (unsigned int i = 0; i < vout.size(); i++) {
 178             if (!vout[i].IsNull())
 179                 ::Serialize(s, CTxOutCompressor(REF(vout[i])));
 180         }
 181         // coinbase height
 182         ::Serialize(s, VARINT(nHeight));
 183     }
 184
 185     template<typename Stream>
 186     void Unserialize(Stream &s) {
 187         unsigned int nCode = 0;
 188         // version
 189         ::Unserialize(s, VARINT(this->nVersion));
 190         // header code
 191         ::Unserialize(s, VARINT(nCode));
 192         fCoinBase = nCode & 1;
 193         std::vector<bool> vAvail(2, false);
 194         vAvail[0] = (nCode & 2) != 0;
 195         vAvail[1] = (nCode & 4) != 0;
 196         unsigned int nMaskCode = (nCode / 8) + ((nCode & 6) != 0 ? 0 : 1);
 197         // spentness bitmask
 198         while (nMaskCode > 0) {
 199             unsigned char chAvail = 0;
 200             ::Unserialize(s, chAvail);
 201             for (unsigned int p = 0; p < 8; p++) {
 202                 bool f = (chAvail & (1 << p)) != 0;
 203                 vAvail.push_back(f);
 204             }
 205             if (chAvail != 0)
 206                 nMaskCode--;
 207         }
 208         // txouts themself
 209         vout.assign(vAvail.size(), CTxOut());
 210         for (unsigned int i = 0; i < vAvail.size(); i++) {
 211             if (vAvail[i])
 212                 ::Unserialize(s, REF(CTxOutCompressor(vout[i])));
 213         }
 214         // coinbase height
 215         ::Unserialize(s, VARINT(nHeight));
 216         Cleanup();
 217     }
 218
 219     //! mark a vout spent
 220     bool Spend(uint32_t nPos);
 221
 222     //! check whether a particular output is still available
 223     bool IsAvailable(unsigned int nPos) const {
 224         return (nPos < vout.size() && !vout[nPos].IsNull());
 225     }
 226
 227     //! check whether the entire CCoins is spent
 228     //! note that only !IsPruned() CCoins can be serialized
 229     bool IsPruned() const {
 230         BOOST_FOREACH(const CTxOut &out, vout)
 231             if (!out.IsNull())
 232                 return false;
 233         return true;
 234     }
 235
 236     size_t DynamicMemoryUsage() const {
 237         size_t ret = memusage::DynamicUsage(vout);
 238         BOOST_FOREACH(const CTxOut &out, vout) {
 239             ret += RecursiveDynamicUsage(out.scriptPubKey);
 240         }
 241         return ret;
 242     }
 243 };
 244
 245 class SaltedTxidHasher
 246 {
 247 private:
 248     /** Salt */
 249     const uint64_t k0, k1;
 250
 251 public:
 252     SaltedTxidHasher();
 253
 254     /**
 255      * This *must* return size_t. With Boost 1.46 on 32-bit systems the
 256      * unordered_map will behave unpredictably if the custom hasher returns a
 257      * uint64_t, resulting in failures when syncing the chain (#4634).
 258      */
 259     size_t operator()(const uint256& txid) const {
 260         return SipHashUint256(k0, k1, txid);
 261     }
 262 };
 263
 264 struct CCoinsCacheEntry
 265 {
 266     CCoins coins; // The actual cached data.
 267     unsigned char flags;
 268
 269     enum Flags {
 270         DIRTY = (1 << 0), // This cache entry is potentially different from the version in the parent view.
 271         FRESH = (1 << 1), // The parent view does not have this entry (or it is pruned).
 272         /* Note that FRESH is a performance optimization with which we can
 273          * erase coins that are fully spent if we know we do not need to
 274          * flush the changes to the parent cache.  It is always safe to
 275          * not mark FRESH if that condition is not guaranteed.
 276          */
 277     };
 278
 279     CCoinsCacheEntry() : coins(), flags(0) {}
 280 };
 281
 282 typedef boost::unordered_map<uint256, CCoinsCacheEntry, SaltedTxidHasher> CCoinsMap;
 283
 284 /** Cursor for iterating over CoinsView state */
 285 class CCoinsViewCursor
 286 {
 287 public:
 288     CCoinsViewCursor(const uint256 &hashBlockIn): hashBlock(hashBlockIn) {}
 289     virtual ~CCoinsViewCursor();
 290
 291     virtual bool GetKey(uint256 &key) const = 0;
 292     virtual bool GetValue(CCoins &coins) const = 0;
 293     virtual unsigned int GetValueSize() const = 0;
 294
 295     virtual bool Valid() const = 0;
 296     virtual void Next() = 0;
 297
 298     //! Get best block at the time this cursor was created
 299     const uint256 &GetBestBlock() const { return hashBlock; }
 300 private:
 301     uint256 hashBlock;
 302 };
 303
 304 /** Abstract view on the open txout dataset. */
 305 class CCoinsView
 306 {
 307 public:
 308     //! Retrieve the CCoins (unspent transaction outputs) for a given txid
 309     virtual bool GetCoins(const uint256 &txid, CCoins &coins) const;
 310
 311     //! Just check whether we have data for a given txid.
 312     //! This may (but cannot always) return true for fully spent transactions
 313     virtual bool HaveCoins(const uint256 &txid) const;
 314
 315     //! Retrieve the block hash whose state this CCoinsView currently represents
 316     virtual uint256 GetBestBlock() const;
 317
 318     //! Do a bulk modification (multiple CCoins changes + BestBlock change).
 319     //! The passed mapCoins can be modified.
 320     virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 321
 322     //! Get a cursor to iterate over the whole state
 323     virtual CCoinsViewCursor *Cursor() const;
 324
 325     //! As we use CCoinsViews polymorphically, have a virtual destructor
 326     virtual ~CCoinsView() {}
 327 };
 328
 329
 330 /** CCoinsView backed by another CCoinsView */
 331 class CCoinsViewBacked : public CCoinsView
 332 {
 333 protected:
 334     CCoinsView *base;
 335
 336 public:
 337     CCoinsViewBacked(CCoinsView *viewIn);
 338     bool GetCoins(const uint256 &txid, CCoins &coins) const;
 339     bool HaveCoins(const uint256 &txid) const;
 340     uint256 GetBestBlock() const;
 341     void SetBackend(CCoinsView &viewIn);
 342     bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 343     CCoinsViewCursor *Cursor() const;
 344 };
 345
 346
 347 class CCoinsViewCache;
 348
 349 /**
 350  * A reference to a mutable cache entry. Encapsulating it allows us to run
 351  *  cleanup code after the modification is finished, and keeping track of
 352  *  concurrent modifications.
 353  */
 354 class CCoinsModifier
 355 {
 356 private:
 357     CCoinsViewCache& cache;
 358     CCoinsMap::iterator it;
 359     size_t cachedCoinUsage; // Cached memory usage of the CCoins object before modification
 360     CCoinsModifier(CCoinsViewCache& cache_, CCoinsMap::iterator it_, size_t usage);
 361
 362 public:
 363     CCoins* operator->() { return &it->second.coins; }
 364     CCoins& operator*() { return it->second.coins; }
 365     ~CCoinsModifier();
 366     friend class CCoinsViewCache;
 367 };
 368
 369 /** CCoinsView that adds a memory cache for transactions to another CCoinsView */
 370 class CCoinsViewCache : public CCoinsViewBacked
 371 {
 372 protected:
 373     /* Whether this cache has an active modifier. */
 374     bool hasModifier;
 375
 376
 377     /**
 378      * Make mutable so that we can "fill the cache" even from Get-methods
 379      * declared as "const".
 380      */
 381     mutable uint256 hashBlock;
 382     mutable CCoinsMap cacheCoins;
 383
 384     /* Cached dynamic memory usage for the inner CCoins objects. */
 385     mutable size_t cachedCoinsUsage;
 386
 387 public:
 388     CCoinsViewCache(CCoinsView *baseIn);
 389     ~CCoinsViewCache();
 390
 391     // Standard CCoinsView methods
 392     bool GetCoins(const uint256 &txid, CCoins &coins) const;
 393     bool HaveCoins(const uint256 &txid) const;
 394     uint256 GetBestBlock() const;
 395     void SetBestBlock(const uint256 &hashBlock);
 396     bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 397
 398     /**
 399      * Check if we have the given tx already loaded in this cache.
 400      * The semantics are the same as HaveCoins(), but no calls to
 401      * the backing CCoinsView are made.
 402      */
 403     bool HaveCoinsInCache(const uint256 &txid) const;
 404
 405     /**
 406      * Return a pointer to CCoins in the cache, or NULL if not found. This is
 407      * more efficient than GetCoins. Modifications to other cache entries are
 408      * allowed while accessing the returned pointer.
 409      */
 410     const CCoins* AccessCoins(const uint256 &txid) const;
 411
 412     /**
 413      * Return a modifiable reference to a CCoins. If no entry with the given
 414      * txid exists, a new one is created. Simultaneous modifications are not
 415      * allowed.
 416      */
 417     CCoinsModifier ModifyCoins(const uint256 &txid);
 418
 419     /**
 420      * Return a modifiable reference to a CCoins. Assumes that no entry with the given
 421      * txid exists and creates a new one. This saves a database access in the case where
 422      * the coins were to be wiped out by FromTx anyway.  This should not be called with
 423      * the 2 historical coinbase duplicate pairs because the new coins are marked fresh, and
 424      * in the event the duplicate coinbase was spent before a flush, the now pruned coins
 425      * would not properly overwrite the first coinbase of the pair. Simultaneous modifications
 426      * are not allowed.
 427      */
 428     CCoinsModifier ModifyNewCoins(const uint256 &txid, bool coinbase);
 429
 430     /**
 431      * Push the modifications applied to this cache to its base.
 432      * Failure to call this method before destruction will cause the changes to be forgotten.
 433      * If false is returned, the state of this cache (and its backing view) will be undefined.
 434      */
 435     bool Flush();
 436
 437     /**
 438      * Removes the transaction with the given hash from the cache, if it is
 439      * not modified.
 440      */
 441     void Uncache(const uint256 &txid);
 442
 443     //! Calculate the size of the cache (in number of transactions)
 444     unsigned int GetCacheSize() const;
 445
 446     //! Calculate the size of the cache (in bytes)
 447     size_t DynamicMemoryUsage() const;
 448
 449     /**
 450      * Amount of bitcoins coming in to a transaction
 451      * Note that lightweight clients may not know anything besides the hash of previous transactions,
 452      * so may not be able to calculate this.
 453      *
 454      * @param[in] tx    transaction for which we are checking input total
 455      * @return  Sum of value of all inputs (scriptSigs)
 456      */
 457     CAmount GetValueIn(const CTransaction& tx) const;
 458
 459     //! Check whether all prevouts of the transaction are present in the UTXO set represented by this view
 460     bool HaveInputs(const CTransaction& tx) const;
 461
 462     const CTxOut &GetOutputFor(const CTxIn& input) const;
 463
 464     friend class CCoinsModifier;
 465
 466 private:
 467     CCoinsMap::const_iterator FetchCoins(const uint256 &txid) const;
 468
 469     /**
 470      * By making the copy constructor private, we prevent accidentally using it when one intends to create a cache on top of a base cache.
 471      */
 472     CCoinsViewCache(const CCoinsViewCache &);
 473 };
 474
 475 #endif // BITCOIN_COINS_H