蹭蹭热度，研究一下区块链和bitcoin，还是Linus的话：
talk is cheap , show me the code
想要分析原理的话，推荐图书： 区块链原理、设计与应用
git bitcoin源码：
git clone https://github.com/bitcoin/bitcoin.git
安装编译环境和依赖包：
sudo apt-get install software-properties-common
sudo add-apt-repository ppa:bitcoin/bitcoin
sudo apt-get update
sudo apt-get install build-essential libtool autotools-dev autoconf pkg-config libssl-dev libevent-dev
sudo apt-get install libboost-all-dev
sudo apt-get install libdb4.8-dev libdb4.8++-dev
sudo apt-get install libminiupnpc-dev
sudo apt-get install libprotobuf-dev protobuf-compiler
sudo apt-get install libqrencode-dev
可以看到bitcoin是C++代码，通过boost库实现，
编译：
./autogen.sh
./configure
make
这时会生成bitcoind 可执行文件， 结尾为加d一般都是指daemon程序，看源码：
int main(int argc, char* argv[])
{
SetupEnvironment(); //该函数设置了本地运行环境
// Connect bitcoind signal handlers
noui_connect(); //连接bitcoind客户端的信号处理程序
return (AppInit(argc, argv) ? EXIT_SUCCESS : EXIT_FAILURE);
}
AppInit(argc, argv)进入主程序，开始应用程序初始化。
AppInit()包含东西较多，简单的分成两块，一块是系统配置和参数解析，一块进入到实际操作AppInitMain：
fRet = AppInitMain();
AppInitMain中，首先获取bitcoin.conf文件中的配置，没有配置的则设置为默认值：
if (!fLogTimestamps)
LogPrintf("Startup time: %s\n", FormatISO8601DateTime(GetTime()));
LogPrintf("Default data directory %s\n", GetDefaultDataDir().string());
LogPrintf("Using data directory %s\n", GetDataDir().string());
LogPrintf("Using config file %s\n", GetConfigFile(gArgs.GetArg("-conf", BITCOIN_CONF_FILENAME)).string());
LogPrintf("Using at most %i automatic connections (%i file descriptors available)\n", nMaxConnections, nFD);
// Warn about relative -datadir path.
if (gArgs.IsArgSet("-datadir") && !fs::path(gArgs.GetArg("-datadir", "")).is_absolute()) {
LogPrintf("Warning: relative datadir option '%s' specified, which will be interpreted relative to the " /* Continued */
"current working directory '%s'. This is fragile, because if bitcoin is started in the future "
"from a different location, it will be unable to locate the current data files. There could "
"also be data loss if bitcoin is started while in a temporary directory.\n",
gArgs.GetArg("-datadir", ""), fs::current_path().string());
}
然后初始化各个线程并运行：
// Start the lightweight task scheduler thread
CScheduler::Function serviceLoop = boost::bind(&CScheduler::serviceQueue, &scheduler);
threadGroup.create_thread(boost::bind(&TraceThread, "scheduler", serviceLoop));
GetMainSignals().RegisterBackgroundSignalScheduler(scheduler);
GetMainSignals().RegisterWithMempoolSignals(mempool);
注册rpc命令并启动rpc服务：
* Register RPC commands regardless of -server setting so they will be
* available in the GUI RPC console even if external calls are disabled.
*/
RegisterAllCoreRPCCommands(tableRPC);
g_wallet_init_interface.RegisterRPC(tableRPC);
/* Start the RPC server already. It will be started in "warmup" mode
* and not really process calls already (but it will signify connections
* that the server is there and will be ready later). Warmup mode will
* be disabled when initialisation is finished.
*/
if (gArgs.GetBoolArg("-server", false))
{
uiInterface.InitMessage.connect(SetRPCWarmupStatus);
if (!AppInitServers())
return InitError(_("Unable to start HTTP server. See debug log for details."));
}
然后验证钱包数据库：
// ********************************************************* Step 5: verify wallet database integrity
if (!g_wallet_init_interface.Verify()) return false;
之后，进程网络初始化和连接，基本都是各种网络参数和不通类型的网络服务的配置。
加入网络后，下一步开始加载区块链
********************************************************* Step 7: load block chain
fReindex = gArgs.GetBoolArg("-reindex", false);
bool fReindexChainState = gArgs.GetBoolArg("-reindex-chainstate", false);
// cache size calculations
int64_t nTotalCache = (gArgs.GetArg("-dbcache", nDefaultDbCache) << 20);
nTotalCache = std::max(nTotalCache, nMinDbCache << 20); // total cache cannot be less than nMinDbCache
nTotalCache = std::min(nTotalCache, nMaxDbCache << 20); // total cache cannot be greater than nMaxDbcache
int64_t nBlockTreeDBCache = std::min(nTotalCache / 8, nMaxBlockDBCache << 20);
nTotalCache -= nBlockTreeDBCache;
int64_t nTxIndexCache = std::min(nTotalCache / 8, gArgs.GetBoolArg("-txindex", DEFAULT_TXINDEX) ? nMaxTxIndexCache << 20 : 0);
nTotalCache -= nTxIndexCache;
int64_t nCoinDBCache = std::min(nTotalCache / 2, (nTotalCache / 4) + (1 << 23)); // use 25%-50% of the remainder for disk cache
nCoinDBCache = std::min(nCoinDBCache, nMaxCoinsDBCache << 20); // cap total coins db cache
nTotalCache -= nCoinDBCache;
nCoinCacheUsage = nTotalCache; // the rest goes to in-memory cache
int64_t nMempoolSizeMax = gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
LogPrintf("Cache configuration:\n");
LogPrintf("* Using %.1fMiB for block index database\n", nBlockTreeDBCache * (1.0 / 1024 / 1024));
if (gArgs.GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
LogPrintf("* Using %.1fMiB for transaction index database\n", nTxIndexCache * (1.0 / 1024 / 1024));
}
LogPrintf("* Using %.1fMiB for chain state database\n", nCoinDBCache * (1.0 / 1024 / 1024));
LogPrintf("* Using %.1fMiB for in-memory UTXO set (plus up to %.1fMiB of unused mempool space)\n", nCoinCacheUsage * (1.0 / 1024 / 1024), nMempoolSizeMax * (1.0 / 1024 / 1024));
加载完成后，进入挖矿阶段， while循环
挖掘成功后，按照钱包地址，加载钱包，进行一系列修改和配置
// if pruning, unset the service bit and perform the initial blockstore prune
// after any wallet rescanning has taken place.
if (fPruneMode) {
LogPrintf("Unsetting NODE_NETWORK on prune mode\n");
nLocalServices = ServiceFlags(nLocalServices & ~NODE_NETWORK);
if (!fReindex) {
uiInterface.InitMessage(_("Pruning blockstore..."));
PruneAndFlush();
}
}
产生新的block之后，创建新节点：
CConnman::Options connOptions;
connOptions.nLocalServices = nLocalServices;
connOptions.nMaxConnections = nMaxConnections;
connOptions.nMaxOutbound = std::min(MAX_OUTBOUND_CONNECTIONS, connOptions.nMaxConnections);
connOptions.nMaxAddnode = MAX_ADDNODE_CONNECTIONS;
connOptions.nMaxFeeler = 1;
connOptions.nBestHeight = chain_active_height;
connOptions.uiInterface = &uiInterface;
connOptions.m_msgproc = peerLogic.get();
connOptions.nSendBufferMaxSize = 1000*gArgs.GetArg("-maxsendbuffer", DEFAULT_MAXSENDBUFFER);
connOptions.nReceiveFloodSize = 1000*gArgs.GetArg("-maxreceivebuffer", DEFAULT_MAXRECEIVEBUFFER);
connOptions.m_added_nodes = gArgs.GetArgs("-addnode");
connOptions.nMaxOutboundTimeframe = nMaxOutboundTimeframe;
connOptions.nMaxOutboundLimit = nMaxOutboundLimit;
新的节点创建完成并加入到区块链中，完成！