比特币源码解读之交易发起

(本文使用的是比特币v0.1.0版本 点击下载源码)

• 新建交易
  • 选取交易
  • 计算交易费
  • 填充输入和输出
  • 计算Merkle值
• 提交交易请求
  • 增加交易到钱包中
• 接受交易
  • 检查交易是否有效
  • 检查交易是否创建成功
  • 检查交易是否冲突
  • 检查是否与已有交易冲突
  • 交易保存到内存中
  • 从钱包移除旧的交易
• 广播钱包中的交易
  • 发送INV消息

本文主要描述交易是如何发起中，其过程包含交易的新建（包含交易的选择，交易费的计算、签名）；提交交易请求；本节点接受交易（验证、检查并保存交易等）；最后广播交易到其他节点中。
流程图如下所示：

新建交易

1. if (!CreateTransaction(scriptPubKey, nValue, wtxNew, nFeeRequired))
2. {
3. string strError;
4. if (nValue + nFeeRequired > GetBalance())
5. strError = strprintf("Error: This is an oversized transaction that requires a transaction fee of %s ", FormatMoney(nFeeRequired).c_str());
6. else
7. strError = "Error: Transaction creation failed ";
8. wxMessageBox(strError, "Sending...");
9. return error("SendMoney() : %s\n", strError.c_str());
10. }

选取交易

具体选择交易使用的“随机逼近算法”在后续《比特币源码解读之选币》一文中介绍

1. set<CWalletTx*> setCoins;
2. if (!SelectCoins(nValue, setCoins))
3. return false;

计算交易费

如果默认的交易费小于当前计算的交易费用，则需要根据当前计算的交易费重新填充交易

1. // Check that enough fee is included
2. if (nFee < wtxNew.GetMinFee(true))
3. {
4. nFee = nFeeRequiredRet = wtxNew.GetMinFee(true);
5. continue;
6. }

填充输入和输出

填充输出

1. wtxNew.vout.push_back(CTxOut(nValueOut, scriptPubKey));
3. // Fill vout[1] back to self with any change
4. if (nValueIn > nValue)
5. {
6. // Use the same key as one of the coins
7. vector<unsigned char> vchPubKey;
8. CTransaction& txFirst = *(*setCoins.begin());
9. foreach(const CTxOut& txout, txFirst.vout)
10. if (txout.IsMine())
11. if (ExtractPubKey(txout.scriptPubKey, true, vchPubKey))
12. break;
13. if (vchPubKey.empty())
14. return false;
16. // Fill vout[1] to ourself
17. CScript scriptPubKey;
18. scriptPubKey << vchPubKey << OP_CHECKSIG;
19. wtxNew.vout.push_back(CTxOut(nValueIn - nValue, scriptPubKey));
20. }

填充输入

1. foreach(CWalletTx* pcoin, setCoins)
2. for (int nOut = 0; nOut < pcoin->vout.size(); nOut++)
3. if (pcoin->vout[nOut].IsMine())
4. wtxNew.vin.push_back(CTxIn(pcoin->GetHash(), nOut));
6. 签名
7. int nIn = 0;
8. foreach(CWalletTx* pcoin, setCoins)
9. for (int nOut = 0; nOut < pcoin->vout.size(); nOut++)
10. if (pcoin->vout[nOut].IsMine())
11. SignSignature(*pcoin, wtxNew, nIn++);

计算Merkle值

1. wtxNew.AddSupportingTransactions(txdb);
3. void CWalletTx::AddSupportingTransactions(CTxDB& txdb)
4. {
5. vtxPrev.clear();
7. const int COPY_DEPTH = 3;
8. if (SetMerkleBranch() < COPY_DEPTH)
9. {
10. vector<uint256> vWorkQueue;
11. foreach(const CTxIn& txin, vin)
12. vWorkQueue.push_back(txin.prevout.hash);
14. // This critsect is OK because txdb is already open
15. CRITICAL_BLOCK(cs_mapWallet)
16. {
17. map<uint256, const CMerkleTx*> mapWalletPrev;
18. set<uint256> setAlreadyDone;
19. for (int i = 0; i < vWorkQueue.size(); i++)
20. {
21. uint256 hash = vWorkQueue[i];
22. if (setAlreadyDone.count(hash))
23. continue;
24. setAlreadyDone.insert(hash);
26. CMerkleTx tx;
27. if (mapWallet.count(hash))
28. {
29. tx = mapWallet[hash];
30. foreach(const CMerkleTx& txWalletPrev, mapWallet[hash].vtxPrev)
31. mapWalletPrev[txWalletPrev.GetHash()] = &txWalletPrev;
32. }
33. else if (mapWalletPrev.count(hash))
34. {
35. tx = *mapWalletPrev[hash];
36. }
37. else if (!fClient && txdb.ReadDiskTx(hash, tx))
38. {
39. ;
40. }
41. else
42. {
43. printf("ERROR: AddSupportingTransactions() : unsupported transaction\n");
44. continue;
45. }
47. int nDepth = tx.SetMerkleBranch();
48. vtxPrev.push_back(tx);
50. if (nDepth < COPY_DEPTH)
51. foreach(const CTxIn& txin, tx.vin)
52. vWorkQueue.push_back(txin.prevout.hash);
53. }
54. }
55. }
57. reverse(vtxPrev.begin(), vtxPrev.end());
58. }

提交交易请求

1. if (!CommitTransactionSpent(wtxNew))
2. {
3. wxMessageBox("Error finalizing transaction", "Sending...");
4. return error("SendMoney() : Error finalizing transaction");
5. }

增加交易到钱包中

增加交易到钱包中并保存在mapWallet变量中，通过将选择交易写入磁盘

1. bool CommitTransactionSpent(const CWalletTx& wtxNew)
2. {
3. ... ...
4. AddToWallet(wtxNew);
6. // Mark old coins as spent
7. set<CWalletTx*> setCoins;
8. foreach(const CTxIn& txin, wtxNew.vin)
9. setCoins.insert(&mapWallet[txin.prevout.hash]);
10. foreach(CWalletTx* pcoin, setCoins)
11. {
12. pcoin->fSpent = true;
13. pcoin->WriteToDisk();
14. vWalletUpdated.push_back(make_pair(pcoin->GetHash(), false));
15. }
16. }
17. MainFrameRepaint();
18. return true;
19. }

接受交易

1. if (!wtxNew.AcceptTransaction())
2. {
3. // This must not fail. The transaction has already been signed and recorded.
4. throw runtime_error("SendMoney() : wtxNew.AcceptTransaction() failed\n");
5. wxMessageBox("Error: Transaction not valid", "Sending...");
6. return error("SendMoney() : Error: Transaction not valid");
7. }

检查交易是否有效

1. if (IsCoinBase())
2. return error("AcceptTransaction() : coinbase as individual tx");
4. if (!CheckTransaction())
5. return error("AcceptTransaction() : CheckTransaction failed");

检查交易是否创建成功

1. uint256 hash = GetHash();
2. CRITICAL_BLOCK(cs_mapTransactions)
3. if (mapTransactions.count(hash))
4. return false;
5. if (fCheckInputs)
6. if (txdb.ContainsTx(hash))
7. return false;

检查交易是否冲突

1. uint256 hash = GetHash();
2. CRITICAL_BLOCK(cs_mapTransactions)
3. if (mapTransactions.count(hash))
4. return false;
5. if (fCheckInputs)
6. if (txdb.ContainsTx(hash))
7. return false;
9. // Check for conflicts with in-memory transactions
10. CTransaction* ptxOld = NULL;
11. for (int i = 0; i < vin.size(); i++)
12. {
13. COutPoint outpoint = vin[i].prevout;
14. if (mapNextTx.count(outpoint))
15. {
16. // Allow replacing with a newer version of the same transaction
17. if (i != 0)
18. return false;
19. ptxOld = mapNextTx[outpoint].ptx;
20. if (!IsNewerThan(*ptxOld))
21. return false;
22. for (int i = 0; i < vin.size(); i++)
23. {
24. COutPoint outpoint = vin[i].prevout;
25. if (!mapNextTx.count(outpoint) || mapNextTx[outpoint].ptx != ptxOld)
26. return false;
27. }
28. break;
29. }
30. }

检查是否与已有交易冲突

1. map<uint256, CTxIndex> mapUnused;
2. int64 nFees = 0;
3. if (fCheckInputs && !ConnectInputs(txdb, mapUnused, CDiskTxPos(1,1,1), 0, nFees, false, false))
4. {
5. if (pfMissingInputs)
6. *pfMissingInputs = true;
7. return error("AcceptTransaction() : ConnectInputs failed %s", hash.ToString().substr(0,6).c_str());
8. }

交易保存到内存中

1. CRITICAL_BLOCK(cs_mapTransactions)
2. {
3. if (ptxOld)
4. {
5. printf("mapTransaction.erase(%s) replacing with new version\n", ptxOld->GetHash().ToString().c_str());
6. mapTransactions.erase(ptxOld->GetHash());
7. }
8. AddToMemoryPool();
9. }

从钱包移除旧的交易

1. if (ptxOld)
2. EraseFromWallet(ptxOld->GetHash());

广播钱包中的交易

1. wtxNew.RelayWalletTransaction();

发送INV消息

1. void CWalletTx::RelayWalletTransaction(CTxDB& txdb)
2. {
3. foreach(const CMerkleTx& tx, vtxPrev)
4. {
5. if (!tx.IsCoinBase())
6. {
7. uint256 hash = tx.GetHash();
8. if (!txdb.ContainsTx(hash))
9. RelayMessage(CInv(MSG_TX, hash), (CTransaction)tx);
10. }
11. }
12. if (!IsCoinBase())
13. {
14. uint256 hash = GetHash();
15. if (!txdb.ContainsTx(hash))
16. {
17. printf("Relaying wtx %s\n", hash.ToString().substr(0,6).c_str());
18. RelayMessage(CInv(MSG_TX, hash), (CTransaction)*this);
19. }
20. }
21. }

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作者：雨后的蚊子

原文链接：http://www.360bchain.com/article/89.html