在整个的交易过程中，CTransaction这个类是基础的数据结构，在网络分发的数据中应用的数据结构最终也是它。一个正常的交易从发起到结束，再到确认，需要一个比较长的时间。交易的过程相对来说比较复杂。这里就按照上面的的一个发送交易，对内部的一些内容展开讨论。
在展开前先说一下两个小的概念，一个是最小传播交易费，一个是创建最小交易的费用，这两个时期版本是相同的，但新的分开了。
判断最小传播交易：CFeeRate minRelayTxFee = CFeeRate(5000)； 判断最小创建交易：CFeeRate CWallet::minTxFee = CFeeRate(1000);
WalletModel::SendCoinsReturn WalletModel::prepareTransaction(WalletModelTransaction &transaction, const CCoinControl \*coinControl)
{
......
//此处主要是对本地添加和维护的收款人列表进行处理。
QList<SendCoinsRecipient> recipients = transaction.getRecipients();
std::vector<CRecipient> vecSend;
if(recipients.empty())//接收人为空，退出
{
return OK;
}
......
// Pre-check input data for validity
Q_FOREACH(const SendCoinsRecipient &rcp, recipients)
{
if (rcp.fSubtractFeeFromAmount)
fSubtractFeeFromAmount = true;
if (rcp.paymentRequest.IsInitialized())
{ // PaymentRequest...
CAmount subtotal = 0;
const payments::PaymentDetails& details = rcp.paymentRequest.getDetails();
//从收款人列表中得到相关脚本，供后面的发送币使用。
for (int i = 0; i < details.outputs_size(); i++)
{
const payments::Output& out = details.outputs(i);
if (out.amount() <= 0) continue;
subtotal += out.amount();
const unsigned char* scriptStr = (const unsigned char*)out.script().data();
CScript scriptPubKey(scriptStr, scriptStr+out.script().size());
CAmount nAmount = out.amount();
CRecipient recipient = {scriptPubKey, nAmount, rcp.fSubtractFeeFromAmount};
vecSend.push_back(recipient);
}
if (subtotal <= 0)
{
return InvalidAmount;
}
total += subtotal;
}
else
{ // User-entered bitcoin address / amount:
if(!validateAddress(rcp.address))
{
return InvalidAddress;
}
if(rcp.amount <= 0)
{
return InvalidAmount;
}
setAddress.insert(rcp.address);
++nAddresses;
CScript scriptPubKey = GetScriptForDestination(CBitcoinAddress(rcp.address.toStdString()).Get());
CRecipient recipient = {scriptPubKey, rcp.amount, rcp.fSubtractFeeFromAmount};
vecSend.push_back(recipient);
total += rcp.amount;
}
}
if(setAddress.size() != nAddresses)
{
return DuplicateAddress;
}
//查询帐户余额
CAmount nBalance = getBalance(coinControl);
if(total > nBalance)
{
return AmountExceedsBalance;
}
{
LOCK2(cs_main, wallet->cs_wallet);
//把密钥分配池和钱包绑定
transaction.newPossibleKeyChange(wallet);
CAmount nFeeRequired = 0;
int nChangePosRet = -1;
std::string strFailReason;
//创建交易和密钥
CWalletTx \*newTx = transaction.getTransaction();
CReserveKey \*keyChange = transaction.getPossibleKeyChange();
//创建交易
bool fCreated = wallet->CreateTransaction(vecSend, \*newTx, \*keyChange, nFeeRequired, nChangePosRet, strFailReason, coinControl);
transaction.setTransactionFee(nFeeRequired);
if (fSubtractFeeFromAmount && fCreated)
transaction.reassignAmounts(nChangePosRet);//重新安排零钱帐户的数据
if(!fCreated)
{
if(!fSubtractFeeFromAmount && (total + nFeeRequired) > nBalance)
{
//费用不够
return SendCoinsReturn(AmountWithFeeExceedsBalance);
}
Q_EMIT message(tr("Send Coins"), QString::fromStdString(strFailReason),
CClientUIInterface::MSG_ERROR);
return TransactionCreationFailed;
}
// reject absurdly high fee > 0.1 bitcoin 费用太高
if (nFeeRequired > 10000000)
return AbsurdFee;
}
return SendCoinsReturn(OK);
}SendCoinsEntry入口UI：
自定义费率：
上面的代码在上篇文章中有过但为了清晰，删除了大部分的代码。这次基本贴全了。
重点照顾一下CreateTransaction：
bool CWallet::CreateTransaction(const vector<CRecipient>\& vecSend,
CWalletTx\& wtxNew, CReserveKey\& reservekey, CAmount& nFeeRet, int\& nChangePosRet, std::string\& strFailReason, const CCoinControl\*coinControl)
{
CAmount nValue = 0;
unsigned int nSubtractFeeFromAmount = 0;
BOOST_FOREACH (const CRecipient& recipient, vecSend)
{
if (nValue < 0 || recipient.nAmount < 0)
{
strFailReason = _("Transaction amounts must be positive");
return false;
}
nValue += recipient.nAmount;
if (recipient.fSubtractFeeFromAmount)
nSubtractFeeFromAmount++;
}
if (vecSend.empty() || nValue < 0)
{
strFailReason = _("Transaction amounts must be positive");
return false;
}
wtxNew.fTimeReceivedIsTxTime = true;
wtxNew.BindWallet(this);
CMutableTransaction txNew;
// Discourage fee sniping.防止费用狙击--为处理小BUG，增加块设置，和书上略有不同
// 最新版本是当前块，意思是说（1~5亿间），大于等于当前块，交易都可用。
// 书上说的不太清楚。
// However because of a off-by-one-error in previous versions we need to
// neuter it by setting nLockTime to at least one less than nBestHeight.
// Secondly currently propagation of transactions created for block heights
// corresponding to blocks that were just mined may be iffy - transactions
// aren't re-accepted into the mempool - we additionally neuter the code by
// going ten blocks back. Doesn't yet do anything for sniping, but does act
// to shake out wallet bugs like not showing nLockTime'd transactions at
// all.
txNew.nLockTime = std::max(0, chainActive.Height() - 10); //设置锁定时间
// Secondly occasionally randomly pick a nLockTime even further back, so
// that transactions that are delayed after signing for whatever reason,
// e.g. high-latency mix networks and some CoinJoin implementations, have
// better privacy.
if (GetRandInt(10) == 0)//设置锁定时间
txNew.nLockTime = std::max(0, (int)txNew.nLockTime - GetRandInt(100));
assert(txNew.nLockTime <= (unsigned int)chainActive.Height());
assert(txNew.nLockTime < LOCKTIME_THRESHOLD);
{
LOCK2(cs_main, cs_wallet);
{
nFeeRet = 0;
while (true)
{
txNew.vin.clear();
txNew.vout.clear();
wtxNew.fFromMe = true;
nChangePosRet = -1;
bool fFirst = true;
CAmount nTotalValue = nValue;
if (nSubtractFeeFromAmount == 0)
nTotalValue += nFeeRet;
double dPriority = 0;
// vouts to the payees
BOOST_FOREACH (const CRecipient& recipient, vecSend)
{
//这里填充CTxOut
CTxOut txout(recipient.nAmount, recipient.scriptPubKey);
if (recipient.fSubtractFeeFromAmount)
{
txout.nValue -= nFeeRet / nSubtractFeeFromAmount; // Subtract fee equally from each selected recipient
if (fFirst) // first receiver pays the remainder not divisible by output count
{
fFirst = false;
txout.nValue -= nFeeRet % nSubtractFeeFromAmount;
}
}
//处理是不是小额交易
if (txout.IsDust(::minRelayTxFee))
{
if (recipient.fSubtractFeeFromAmount && nFeeRet > 0)
{
if (txout.nValue < 0)
strFailReason = _("The transaction amount is too small to pay the fee");
else
strFailReason = _("The transaction amount is too small to send after the fee has been deducted");
}
else
strFailReason = _("Transaction amount too small");
return false;
}
txNew.vout.push_back(txout);//加入输出,将txout填充入CWalletTx，继承自CTransaction
}
// Choose coins to use 选择可以花费的币
set<pair<const CWalletTx*,unsigned int> > setCoins;
CAmount nValueIn = 0;
if (!SelectCoins(nTotalValue, setCoins, nValueIn, coinControl))
{
strFailReason = _("Insufficient funds");
return false;
}
//设置币龄相关
BOOST_FOREACH(PAIRTYPE(const CWalletTx\*, unsigned int) pcoin, setCoins)
{
CAmount nCredit = pcoin.first->vout[pcoin.second].nValue;
//The coin age after the next block (depth+1) is used instead of the current,
//reflecting an assumption the user would accept a bit more delay for
//a chance at a free transaction.
//But mempool inputs might still be in the mempool, so their age stays 0
//计算块龄，这个跟进入mempool有一定的联系。
int age = pcoin.first->GetDepthInMainChain();
if (age != 0)
age += 1;
dPriority += (double)nCredit * age;
}
CAmount nChange = nValueIn - nValue;
if (nSubtractFeeFromAmount == 0)
nChange -= nFeeRet;
//处理零钱
if (nChange > 0)
{
// Fill a vout to ourself
// TODO: pass in scriptChange instead of reservekey so
// change transaction isn't always pay-to-bitcoin-address
//提供更健全的处理机制，即不只是处理比特币地址，也包括各种脚本支持的交易。
CScript scriptChange;
// coin control: send change to custom address自定义地址
if (coinControl && !boost::get<CNoDestination>(&coinControl->destChange))
scriptChange = GetScriptForDestination(coinControl->destChange);
// no coin control: send change to newly generated address没有则产生一个新地址
else
{
// Note: We use a new key here to keep it from being obvious which side is the change.
// The drawback is that by not reusing a previous key, the change may be lost if a
// backup is restored, if the backup doesn't have the new private key for the change.
// If we reused the old key, it would be possible to add code to look for and
// rediscover unknown transactions that were written with keys of ours to recover
// post-backup change.
// Reserve a new key pair from key pool
CPubKey vchPubKey;
bool ret;
ret = reservekey.GetReservedKey(vchPubKey);
assert(ret); // should never fail, as we just unlocked
scriptChange = GetScriptForDestination(vchPubKey.GetID());
}
//为零钱创建一个输出
CTxOut newTxOut(nChange, scriptChange);
// We do not move dust-change to fees, because the sender would end up paying more than requested.
// This would be against the purpose of the all-inclusive feature.
// So instead we raise the change and deduct from the recipient.
//我的理解可能是虽然用记可以多付，但是你不能多收，所以要从你那把钱放回到零钱中去。
if (nSubtractFeeFromAmount > 0 && newTxOut.IsDust(::minRelayTxFee))
{
CAmount nDust = newTxOut.GetDustThreshold(::minRelayTxFee) - newTxOut.nValue;
newTxOut.nValue += nDust; // raise change until no more dust
for (unsigned int i = 0; i < vecSend.size(); i++) // subtract from first recipient
{
if (vecSend[i].fSubtractFeeFromAmount)
{
txNew.vout[i].nValue -= nDust;
if (txNew.vout[i].IsDust(::minRelayTxFee))
{
strFailReason = _("The transaction amount is too small to send after the fee has been deducted");
return false;
}
break;
}
}
}
// Never create dust outputs; if we would, just
// add the dust to the fee.
if (newTxOut.IsDust(::minRelayTxFee))
{
nFeeRet += nChange;
reservekey.ReturnKey();
}
else
{
// Insert change txn at random position:
nChangePosRet = GetRandInt(txNew.vout.size()+1);
vector<CTxOut>::iterator position = txNew.vout.begin()+nChangePosRet;//nChangePosRet 是向量长度的随机数取余。
txNew.vout.insert(position, newTxOut); //随机插入零钱交易的位置
}
}
else
reservekey.ReturnKey();
// Fill vin
//
// Note how the sequence number is set to max()-1 so that the
// nLockTime set above actually works.此处处理上面类图中的CTxIn
//包括内部数据的填充其中有COutPoint类型的prevout
BOOST_FOREACH(const PAIRTYPE(const CWalletTx\*,unsigned int)& coin, setCoins)
txNew.vin.push_back(CTxIn(coin.first->GetHash(),coin.second,CScript(),
std::numeric_limits<unsigned int>::max()-1));
// Sign签名
int nIn = 0;
BOOST_FOREACH(const PAIRTYPE(const CWalletTx\*,unsigned int)& coin, setCoins)
if (!SignSignature(\*this, \*coin.first, txNew, nIn++))
{
strFailReason = _("Signing transaction failed");
return false;
}
// Embed the constructed transaction data in wtxNew.生成交易数据
\*static_cast<CTransaction*>(&wtxNew) = CTransaction(txNew);
// Limit size控制大小 不多于
unsigned int nBytes = ::GetSerializeSize(\*(CTransaction\*)&wtxNew, SER_NETWORK, PROTOCOL_VERSION);
if (nBytes >= MAX_STANDARD_TX_SIZE)
{
strFailReason = _("Transaction too large");
return false;
}
dPriority = wtxNew.ComputePriority(dPriority, nBytes);
// Can we complete this as a free transaction?是不是允许成为一个免费的交易
if (fSendFreeTransactions && nBytes <= MAX_FREE_TRANSACTION_CREATE_SIZE)
{
// Not enough fee: enough priority?
double dPriorityNeeded = mempool.estimatePriority(nTxConfirmTarget);
// Not enough mempool history to estimate: use hard-coded AllowFree.
if (dPriorityNeeded <= 0 && AllowFree(dPriority))
break;
// Small enough, and priority high enough, to send for free
if (dPriorityNeeded > 0 && dPriority >= dPriorityNeeded)
break;
}
CAmount nFeeNeeded = GetMinimumFee(nBytes, nTxConfirmTarget, mempool);
// If we made it here and we aren't even able to meet the relay fee on the next pass, give up
// because we must be at the maximum allowed fee.
//小于广播交易费用报错。
if (nFeeNeeded < ::minRelayTxFee.GetFee(nBytes))
{
strFailReason = _("Transaction too large for fee policy");
return false;
}
if (nFeeRet >= nFeeNeeded)//正常成功然后中断循环
break; // Done, enough fee included.
// Include more fee and try again.如果找的输入得出的交易费太小就直接回到初始位置重找重算。
nFeeRet = nFeeNeeded;
continue;
}
}
}
return true;
}最后就是签名了：
两个重载的SignSignature，最重要的是创建了签名的TransactionSignatureCreator类型的creator
bool ProduceSignature(const BaseSignatureCreator& creator, const CScript& fromPubKey, CScript& scriptSig)
{
txnouttype whichType;
if (!SignStep(creator, fromPubKey, scriptSig, whichType))
return false;
if (whichType == TX_SCRIPTHASH)
{
......
bool fSolved =
SignStep(creator, subscript, scriptSig, subType) && subType != TX_SCRIPTHASH;
......
}
// Test solution
return VerifyScript(scriptSig, fromPubKey, STANDARD_SCRIPT_VERIFY_FLAGS, creator.Checker());
}
static bool SignStep(const BaseSignatureCreator& creator, const CScript& scriptPubKey,
CScript& scriptSigRet, txnouttype& whichTypeRet)
{
scriptSigRet.clear();
vector<valtype> vSolutions;
if (!Solver(scriptPubKey, whichTypeRet, vSolutions))
return false;
CKeyID keyID;
switch (whichTypeRet)
{
case TX_NONSTANDARD:
case TX_NULL_DATA:
return false;
case TX_PUBKEY:
keyID = CPubKey(vSolutions[0]).GetID();
return Sign1(keyID, creator, scriptPubKey, scriptSigRet);
case TX_PUBKEYHASH:
keyID = CKeyID(uint160(vSolutions[0]));
if (!Sign1(keyID, creator, scriptPubKey, scriptSigRet))
return false;
else
{
CPubKey vch;
creator.KeyStore().GetPubKey(keyID, vch);
scriptSigRet << ToByteVector(vch);
}
return true;
case TX_SCRIPTHASH:
return creator.KeyStore().GetCScript(uint160(vSolutions[0]), scriptSigRet);
case TX_MULTISIG:
scriptSigRet << OP_0; // workaround CHECKMULTISIG bug
return (SignN(vSolutions, creator, scriptPubKey, scriptSigRet));
}
return false;
}
//返回一个公钥或者哈希
bool Solver(const CScript& scriptPubKey, txnouttype& typeRet, vector<vector<unsigned char> >& vSolutionsRet)
{
// Templates
static multimap<txnouttype, CScript> mTemplates;
if (mTemplates.empty())
{
// Standard tx, sender provides pubkey, receiver adds signature
mTemplates.insert(make_pair(TX_PUBKEY, CScript() << OP_PUBKEY << OP_CHECKSIG));
// Bitcoin address tx, sender provides hash of pubkey, receiver provides signature and pubkey
mTemplates.insert(make_pair(TX_PUBKEYHASH, CScript() << OP_DUP << OP_HASH160 << OP_PUBKEYHASH << OP_EQUALVERIFY << OP_CHECKSIG));
// Sender provides N pubkeys, receivers provides M signatures
mTemplates.insert(make_pair(TX_MULTISIG, CScript() << OP_SMALLINTEGER << OP_PUBKEYS << OP_SMALLINTEGER << OP_CHECKMULTISIG));
// Empty, provably prunable, data-carrying output
if (GetBoolArg("-datacarrier", true))
mTemplates.insert(make_pair(TX_NULL_DATA, CScript() << OP_RETURN << OP_SMALLDATA));
mTemplates.insert(make_pair(TX_NULL_DATA, CScript() << OP_RETURN));
}
// Shortcut for pay-to-script-hash, which are more constrained than the other types:
// it is always OP_HASH160 20 [20 byte hash] OP_EQUAL
if (scriptPubKey.IsPayToScriptHash())
{
typeRet = TX_SCRIPTHASH;
vector<unsigned char> hashBytes(scriptPubKey.begin()+2, scriptPubKey.begin()+22);
vSolutionsRet.push_back(hashBytes);
return true;
}
// Scan templates
const CScript& script1 = scriptPubKey;
BOOST_FOREACH(const PAIRTYPE(txnouttype, CScript)& tplate, mTemplates)
{
const CScript& script2 = tplate.second;
vSolutionsRet.clear();
opcodetype opcode1, opcode2;
vector<unsigned char> vch1, vch2;
// Compare
CScript::const_iterator pc1 = script1.begin();
CScript::const_iterator pc2 = script2.begin();
while (true)
{
if (pc1 == script1.end() && pc2 == script2.end())
{
// Found a match
typeRet = tplate.first;
if (typeRet == TX_MULTISIG)
{
// Additional checks for TX_MULTISIG:
unsigned char m = vSolutionsRet.front()[0];
unsigned char n = vSolutionsRet.back()[0];
if (m < 1 || n < 1 || m > n || vSolutionsRet.size()-2 != n)
return false;
}
return true;
}
if (!script1.GetOp(pc1, opcode1, vch1))
break;
if (!script2.GetOp(pc2, opcode2, vch2))
break;
// Template matching opcodes:
if (opcode2 == OP_PUBKEYS)
{
while (vch1.size() >= 33 && vch1.size() <= 65)
{
vSolutionsRet.push_back(vch1);
if (!script1.GetOp(pc1, opcode1, vch1))
break;
}
if (!script2.GetOp(pc2, opcode2, vch2))
break;
// Normal situation is to fall through
// to other if/else statements
}
if (opcode2 == OP_PUBKEY)
{
if (vch1.size() < 33 || vch1.size() > 65)
break;
vSolutionsRet.push_back(vch1);
}
else if (opcode2 == OP_PUBKEYHASH)
{
if (vch1.size() != sizeof(uint160))
break;
vSolutionsRet.push_back(vch1);
}
else if (opcode2 == OP_SMALLINTEGER)
{ // Single-byte small integer pushed onto vSolutions
if (opcode1 == OP_0 ||
(opcode1 >= OP_1 && opcode1 <= OP_16))
{
char n = (char)CScript::DecodeOP_N(opcode1);
vSolutionsRet.push_back(valtype(1, n));
}
else
break;
}
else if (opcode2 == OP_SMALLDATA)
{
// small pushdata, <= nMaxDatacarrierBytes
if (vch1.size() > nMaxDatacarrierBytes)
break;
}
else if (opcode1 != opcode2 || vch1 != vch2)
{
// Others must match exactly
break;
}
}
}
vSolutionsRet.clear();
typeRet = TX_NONSTANDARD;
return false;
}
static bool Sign1(const CKeyID& address, const BaseSignatureCreator& creator, const CScript& scriptCode, CScript& scriptSigRet)
{
......
if (!creator.CreateSig(vchSig, address, scriptCode))
return false;
......
}
static bool SignN(const vector<valtype>& multisigdata, const BaseSignatureCreator& creator, const CScript& scriptCode, CScript& scriptSigRet)
{
......
CKeyID keyID = CPubKey(pubkey).GetID();
if (Sign1(keyID, creator, scriptCode, scriptSigRet))
++nSigned;
......
return nSigned==nRequired;
}
真正的签名在这Creator中：
bool TransactionSignatureCreator::CreateSig(std::vector<unsigned char>& vchSig, const CKeyID& address, const CScript& scriptCode) const
{
......
uint256 hash = SignatureHash(scriptCode, \*txTo, nIn, nHashType);
......
}
uint256 SignatureHash(const CScript& scriptCode, const CTransaction& txTo, unsigned int nIn, int nHashType)
{
static const uint256 one(uint256S("0000000000000000000000000000000000000000000000000000000000000001"));
.....
return ss.GetHash();
}到现在为止，基本上一个交易的细节就完成了。