Function waitforblockheight

src/rpc/blockchain.cpp:420–481

}

static RPCMethod waitforblockheight()
{
    return RPCMethod{
        "waitforblockheight",
        "Waits for (at least) block height and returns the height and hash\n"
                "of the current tip.\n"
                "\nReturns the current block on timeout or exit.\n"
                "\nMake sure to use no RPC timeout (bitcoin-cli -rpcclienttimeout=0)",
                {
                    {"height", RPCArg::Type::NUM, RPCArg::Optional::NO, "Block height to wait for."},
                    {"timeout", RPCArg::Type::NUM, RPCArg::Default{0}, "Time in milliseconds to wait for a response. 0 indicates no timeout."},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::STR_HEX, "hash", "The blockhash"},
                        {RPCResult::Type::NUM, "height", "Block height"},
                    }},
                RPCExamples{
                    HelpExampleCli("waitforblockheight", "100 1000")
            + HelpExampleRpc("waitforblockheight", "100, 1000")
                },
        [](const RPCMethod& self, const JSONRPCRequest& request) -> UniValue
{
    int timeout = 0;

    int height = request.params[0].getInt<int>();

    if (!request.params[1].isNull())
        timeout = request.params[1].getInt<int>();
    if (timeout < 0) throw JSONRPCError(RPC_MISC_ERROR, "Negative timeout");

    NodeContext& node = EnsureAnyNodeContext(request.context);
    Mining& miner = EnsureMining(node);

    // Abort if RPC came out of warmup too early
    BlockRef current_block{CHECK_NONFATAL(miner.getTip()).value()};

    const auto deadline{std::chrono::steady_clock::now() + 1ms * timeout};

    while (current_block.height < height) {
        std::optional<BlockRef> block;
        if (timeout) {
            auto now{std::chrono::steady_clock::now()};
            if (now >= deadline) break;
            const MillisecondsDouble remaining{deadline - now};
            block = miner.waitTipChanged(current_block.hash, remaining);
        } else {
            block = miner.waitTipChanged(current_block.hash);
        }
        // Return current block on shutdown
        if (!block) break;
        current_block = *block;
    }

    UniValue ret(UniValue::VOBJ);
    ret.pushKV("hash", current_block.hash.GetHex());
    ret.pushKV("height", current_block.height);