比特币源码阅读(rpc命令-getblockhash)

admin07@admin-MS:~/job/github_source/bitcoin$ bitcoin-cli -regtest getblockhash 0
0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206

通过变量chainActive来获得相应高度的区块hash
src/rpc/blockchain.cpp

static UniValue getblockhash(const JSONRPCRequest& request)
{
    if (request.fHelp || request.params.size() != 1)
        throw std::runtime_error(
            "getblockhash height\n"
            "\nReturns hash of block in best-block-chain at height provided.\n"
            "\nArguments:\n"
            "1. height         (numeric, required) The height index\n"
            "\nResult:\n"
            "\"hash\"         (string) The block hash\n"
            "\nExamples:\n"
            + HelpExampleCli("getblockhash", "1000")
            + HelpExampleRpc("getblockhash", "1000")
        );

    LOCK(cs_main);

    int nHeight = request.params[0].get_int(); //获得参数：高度
    if (nHeight < 0 || nHeight > chainActive.Height()) //小于零/大于最大高度
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Block height out of range");

    //访问CChain的operator[]
    CBlockIndex* pblockindex = chainActive[nHeight];  //CChain:chainActive
    return pblockindex->GetBlockHash().GetHex();
}

class CChain {
    private:
    std::vector vChain; //vector是一个能够存放任意类型的动态数组，能够增加和压缩数据
    //特定高度的CBlockIndex
    /** Returns the index entry at a particular height in this chain, or nullptr if no such height exists. */
    CBlockIndex *operator[](int nHeight) const {//覆写operator[]
        if (nHeight < 0 || nHeight >= (int)vChain.size())
            return nullptr;
        return vChain[nHeight];
    }
}