Add CCoins: pruned list of transaction outputs
The CCoins class represents a pruned set of transaction outputs from a given transaction. It only retains information about its height in the block chain, whether it was a coinbase transaction, and its unspent outputs (script + amount). It has a custom serializer that has very low redundancy.
This commit is contained in:
Pieter Wuille
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0fa593d0fb
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10fd8604d7
234
src/main.h
234
src/main.h
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@ -337,7 +337,7 @@ public:
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scriptPubKey.clear();
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}
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bool IsNull()
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bool IsNull() const
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{
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return (nValue == -1);
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}
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@ -673,6 +673,238 @@ public:
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});)
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};
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/** pruned version of CTransaction: only retains metadata and unspent transaction outputs
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*
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* Serialized format:
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* - VARINT(nVersion)
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* - VARINT(nCode)
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* - unspentness bitvector, for vout[2] and further; least significant byte first
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* - the non-spent CTxOuts (via CTxOutCompressor)
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* - VARINT(nHeight)
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*
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* The nCode value consists of:
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* - bit 1: IsCoinBase()
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* - bit 2: vout[0] is not spent
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* - bit 4: vout[1] is not spent
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* - The higher bits encode N, the number of non-zero bytes in the following bitvector.
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* - In case both bit 2 and bit 4 are unset, they encode N-1, as there must be at
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* least one non-spent output).
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*
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* Example: 0104835800816115944e077fe7c803cfa57f29b36bf87c1d358bb85e
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* <><><--------------------------------------------><---->
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* | \ | /
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* version code vout[1] height
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*
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* - version = 1
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* - code = 4 (vout[1] is not spent, and 0 non-zero bytes of bitvector follow)
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* - unspentness bitvector: as 0 non-zero bytes follow, it has length 0
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* - vout[1]: 835800816115944e077fe7c803cfa57f29b36bf87c1d35
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* * 8358: compact amount representation for 60000000000 (600 BTC)
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* * 00: special txout type pay-to-pubkey-hash
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* * 816115944e077fe7c803cfa57f29b36bf87c1d35: address uint160
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* - height = 203998
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*
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*
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* Example: 0109044086ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4eebbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa486af3b
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* <><><--><--------------------------------------------------><----------------------------------------------><---->
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* / \ \ | | /
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* version code unspentness vout[4] vout[16] height
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*
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* - version = 1
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* - code = 9 (coinbase, neither vout[0] or vout[1] are unspent,
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* 2 (1, +1 because both bit 2 and bit 4 are unset) non-zero bitvector bytes follow)
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* - unspentness bitvector: bits 2 (0x04) and 14 (0x4000) are set, so vout[2+2] and vout[14+2] are unspent
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* - vout[4]: 86ef97d5790061b01caab50f1b8e9c50a5057eb43c2d9563a4ee
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* * 86ef97d579: compact amount representation for 234925952 (2.35 BTC)
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* * 00: special txout type pay-to-pubkey-hash
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* * 61b01caab50f1b8e9c50a5057eb43c2d9563a4ee: address uint160
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* - vout[16]: bbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa4
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* * bbd123: compact amount representation for 110397 (0.001 BTC)
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* * 00: special txout type pay-to-pubkey-hash
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* * 8c988f1a4a4de2161e0f50aac7f17e7f9555caa4: address uint160
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* - height = 120891
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*/
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class CCoins
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{
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public:
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// whether transaction is a coinbase
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bool fCoinBase;
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// unspent transaction outputs; spent outputs are .IsNull(); spent outputs at the end of the array are dropped
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std::vector<CTxOut> vout;
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// at which height this transaction was included in the active blockchain
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int nHeight;
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// version of the CTransaction; accesses to this value should probably check for nHeight as well,
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// as new tx version will probably only be introduced at certain heights
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int nVersion;
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// construct a CCoins from a CTransaction, at a given height
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CCoins(const CTransaction &tx, int nHeightIn) : fCoinBase(tx.IsCoinBase()), vout(tx.vout), nHeight(nHeightIn), nVersion(tx.nVersion) { }
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// empty constructor
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CCoins() : fCoinBase(false), vout(0), nHeight(0), nVersion(0) { }
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// remove spent outputs at the end of vout
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void Cleanup() {
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while (vout.size() > 0 && vout.back().IsNull())
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vout.pop_back();
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}
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// equality test
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friend bool operator==(const CCoins &a, const CCoins &b) {
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return a.fCoinBase == b.fCoinBase &&
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a.nHeight == b.nHeight &&
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a.nVersion == b.nVersion &&
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a.vout == b.vout;
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}
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friend bool operator!=(const CCoins &a, const CCoins &b) {
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return !(a == b);
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}
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// calculate number of bytes for the bitmask, and its number of non-zero bytes
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// each bit in the bitmask represents the availability of one output, but the
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// availabilities of the first two outputs are encoded separately
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void CalcMaskSize(unsigned int &nBytes, unsigned int &nNonzeroBytes) const {
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unsigned int nLastUsedByte = 0;
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for (unsigned int b = 0; 2+b*8 < vout.size(); b++) {
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bool fZero = true;
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for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++) {
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if (!vout[2+b*8+i].IsNull()) {
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fZero = false;
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continue;
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}
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}
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if (!fZero) {
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nLastUsedByte = b + 1;
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nNonzeroBytes++;
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}
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}
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nBytes += nLastUsedByte;
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}
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bool IsCoinBase() const {
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return fCoinBase;
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}
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unsigned int GetSerializeSize(int nType, int nVersion) const {
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unsigned int nSize = 0;
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unsigned int nMaskSize = 0, nMaskCode = 0;
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CalcMaskSize(nMaskSize, nMaskCode);
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bool fFirst = vout.size() > 0 && !vout[0].IsNull();
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bool fSecond = vout.size() > 1 && !vout[1].IsNull();
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assert(fFirst || fSecond || nMaskCode);
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unsigned int nCode = 8*(nMaskCode - (fFirst || fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
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// version
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nSize += ::GetSerializeSize(VARINT(this->nVersion), nType, nVersion);
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// size of header code
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nSize += ::GetSerializeSize(VARINT(nCode), nType, nVersion);
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// spentness bitmask
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nSize += nMaskSize;
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// txouts themself
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for (unsigned int i = 0; i < vout.size(); i++)
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if (!vout[i].IsNull())
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nSize += ::GetSerializeSize(CTxOutCompressor(REF(vout[i])), nType, nVersion);
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// height
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nSize += ::GetSerializeSize(VARINT(nHeight), nType, nVersion);
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return nSize;
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}
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template<typename Stream>
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void Serialize(Stream &s, int nType, int nVersion) const {
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unsigned int nMaskSize = 0, nMaskCode = 0;
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CalcMaskSize(nMaskSize, nMaskCode);
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bool fFirst = vout.size() > 0 && !vout[0].IsNull();
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bool fSecond = vout.size() > 1 && !vout[1].IsNull();
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assert(fFirst || fSecond || nMaskCode);
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unsigned int nCode = 8*(nMaskCode - (fFirst || fSecond ? 0 : 1)) + (fCoinBase ? 1 : 0) + (fFirst ? 2 : 0) + (fSecond ? 4 : 0);
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// version
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::Serialize(s, VARINT(this->nVersion), nType, nVersion);
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// header code
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::Serialize(s, VARINT(nCode), nType, nVersion);
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// spentness bitmask
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for (unsigned int b = 0; b<nMaskSize; b++) {
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unsigned char chAvail = 0;
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for (unsigned int i = 0; i < 8 && 2+b*8+i < vout.size(); i++)
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if (!vout[2+b*8+i].IsNull())
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chAvail |= (1 << i);
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::Serialize(s, chAvail, nType, nVersion);
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}
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// txouts themself
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for (unsigned int i = 0; i < vout.size(); i++) {
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if (!vout[i].IsNull())
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::Serialize(s, CTxOutCompressor(REF(vout[i])), nType, nVersion);
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}
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// coinbase height
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::Serialize(s, VARINT(nHeight), nType, nVersion);
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}
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template<typename Stream>
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void Unserialize(Stream &s, int nType, int nVersion) {
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unsigned int nCode = 0;
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// version
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::Unserialize(s, VARINT(this->nVersion), nType, nVersion);
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// header code
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::Unserialize(s, VARINT(nCode), nType, nVersion);
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fCoinBase = nCode & 1;
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std::vector<bool> vAvail(2, false);
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vAvail[0] = nCode & 2;
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vAvail[1] = nCode & 4;
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unsigned int nMaskCode = (nCode / 8) + ((nCode & 6) != 0 ? 0 : 1);
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// spentness bitmask
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while (nMaskCode > 0) {
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unsigned char chAvail = 0;
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::Unserialize(s, chAvail, nType, nVersion);
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for (unsigned int p = 0; p < 8; p++) {
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bool f = (chAvail & (1 << p)) != 0;
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vAvail.push_back(f);
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}
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if (chAvail != 0)
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nMaskCode--;
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}
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// txouts themself
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vout.assign(vAvail.size(), CTxOut());
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for (unsigned int i = 0; i < vAvail.size(); i++) {
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if (vAvail[i])
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::Unserialize(s, REF(CTxOutCompressor(vout[i])), nType, nVersion);
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}
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// coinbase height
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::Unserialize(s, VARINT(nHeight), nType, nVersion);
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Cleanup();
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}
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// mark an outpoint spent
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bool Spend(const COutPoint &out) {
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if (out.n >= vout.size())
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return false;
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if (vout[out.n].IsNull())
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return false;
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vout[out.n].SetNull();
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Cleanup();
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return true;
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}
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// mark a vout spent
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bool Spend(int nPos) {
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COutPoint out(0, nPos);
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return Spend(out);
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}
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// check whether a particular output is still available
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bool IsAvailable(unsigned int nPos) const {
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return (nPos < vout.size() && !vout[nPos].IsNull());
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}
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// check whether the entire CCoins is spent
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// note that only !IsPruned() CCoins can be serialized
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bool IsPruned() const {
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BOOST_FOREACH(const CTxOut &out, vout)
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if (!out.IsNull())
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return false;
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return true;
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}
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};
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