init

15 files changed, 3636 insertions, 0 deletions

diff --git a/src/client.cpp b/src/client.cpp
new file mode 100644
index 0000000..f787003
--- /dev/null
+++ b/src/client.cpp
@@ -0,0 +1,43 @@
+#include "client.h"
+
+namespace hotstuff {
+
+uint64_t CommandDummy::cnt = 0;
+
+void MsgClient::gen_reqcmd(const Command &cmd) {
+    DataStream s;
+    set_opcode(REQ_CMD);
+    s << cmd;
+    set_payload(std::move(s));
+}
+
+void MsgClient::parse_reqcmd(CommandDummy &cmd) const {
+    DataStream s(get_payload());
+    s >> cmd;
+}
+
+void MsgClient::gen_respcmd(const uint256_t &cmd_hash, const Finality &fin) {
+    DataStream s;
+    set_opcode(RESP_CMD);
+    s << cmd_hash << fin;
+    set_payload(std::move(s));
+}
+
+void MsgClient::parse_respcmd(uint256_t &cmd_hash, Finality &fin) const {
+    DataStream s(get_payload());
+    s >> cmd_hash >> fin;
+}
+
+void MsgClient::gen_chkcmd(const uint256_t &cmd_hash) {
+    DataStream s;
+    set_opcode(CHK_CMD);
+    s << cmd_hash;
+    set_payload(std::move(s));
+}
+
+void MsgClient::parse_chkcmd(uint256_t &cmd_hash) const {
+    DataStream s(get_payload());
+    s >> cmd_hash;
+}
+
+}
diff --git a/src/client.h b/src/client.h
new file mode 100644
index 0000000..dd1cfee
--- /dev/null
+++ b/src/client.h
@@ -0,0 +1,66 @@
+#ifndef _HOTSTUFF_CLIENT_H
+#define _HOTSTUFF_CLIENT_H
+
+#include "type.h"
+#include "salticidae/msg.h"
+#include "entity.h"
+
+namespace hotstuff {
+
+enum {
+    REQ_CMD = 0x4,
+    RESP_CMD = 0x5,
+    CHK_CMD = 0x6
+};
+
+class CommandDummy: public Command {
+    static uint64_t cnt;
+    uint64_t n;
+    uint256_t hash;
+
+    public:
+
+    CommandDummy() {}
+
+    ~CommandDummy() override {}
+
+    CommandDummy(uint64_t n):
+        n(n), hash(salticidae::get_hash(*this)) {}
+
+    static command_t make_cmd() {
+        return new CommandDummy(cnt++);
+    }
+
+    void serialize(DataStream &s) const override {
+        s << n;
+    }
+
+    void unserialize(DataStream &s) override {
+        s >> n;
+        hash = salticidae::get_hash(*this);
+    }
+
+    const uint256_t &get_hash() const override {
+        return hash;
+    }
+
+    bool verify() const override {
+        return true;
+    }
+};
+
+struct MsgClient: public salticidae::MsgBase<> {
+    using MsgBase::MsgBase;
+    void gen_reqcmd(const Command &cmd);
+    void parse_reqcmd(CommandDummy &cmd) const;
+
+    void gen_respcmd(const uint256_t &cmd_hash, const Finality &fin);
+    void parse_respcmd(uint256_t &cmd_hash, Finality &fin) const;
+
+    void gen_chkcmd(const uint256_t &cmd_hash);
+    void parse_chkcmd(uint256_t &cmd_hash) const;
+};
+
+}
+
+#endif
diff --git a/src/core.cpp b/src/core.cpp
new file mode 100644
index 0000000..d6a4cc7
--- /dev/null
+++ b/src/core.cpp
@@ -0,0 +1,723 @@
+#include <stack>
+#include "core.h"
+
+using salticidae::DataStream;
+using salticidae::static_pointer_cast;
+using salticidae::get_hash;
+
+#define LOG_INFO HOTSTUFF_LOG_INFO
+#define LOG_DEBUG HOTSTUFF_LOG_DEBUG
+#define LOG_WARN HOTSTUFF_LOG_WARN
+
+namespace hotstuff {
+
+void MsgHotStuff::gen_propose(const Proposal &proposal) {
+    DataStream s;
+    set_opcode(PROPOSE);
+    s << proposal;
+    set_payload(std::move(s));
+}
+
+void MsgHotStuff::parse_propose(Proposal &proposal) const {
+    DataStream(get_payload()) >> proposal;
+}
+
+void MsgHotStuff::gen_vote(const Vote &vote) {
+    DataStream s;
+    set_opcode(VOTE);
+    s << vote;
+    set_payload(std::move(s));
+}
+
+void MsgHotStuff::parse_vote(Vote &vote) const {
+    DataStream(get_payload()) >> vote;
+}
+
+void MsgHotStuff::gen_qfetchblk(const std::vector<uint256_t> &blk_hashes) {
+    DataStream s;
+    set_opcode(QUERY_FETCH_BLK);
+    gen_hash_list(s, blk_hashes);
+    set_payload(std::move(s));
+}
+
+void MsgHotStuff::parse_qfetchblk(std::vector<uint256_t> &blk_hashes) const {
+    DataStream s(get_payload());
+    parse_hash_list(s, blk_hashes);
+}
+
+void MsgHotStuff::gen_rfetchblk(const std::vector<block_t> &blks) {
+    DataStream s;
+    set_opcode(RESP_FETCH_BLK);
+    s << htole((uint32_t)blks.size());
+    for (auto blk: blks) s << *blk;
+    set_payload(std::move(s));
+}
+
+void MsgHotStuff::parse_rfetchblk(std::vector<block_t> &blks, HotStuffCore *hsc) const {
+    DataStream s;
+    uint32_t size;
+    s >> size;
+    size = letoh(size);
+    blks.resize(size);
+    for (auto &blk: blks)
+    {
+        Block _blk;
+        _blk.unserialize(s, hsc);
+        if (!_blk.verify(hsc->get_config()))
+            blk = hsc->storage->add_blk(std::move(_blk));
+        else
+        {
+            blk = nullptr;
+            LOG_WARN("block is invalid");
+        }
+    }
+}
+
+/* The core logic of HotStuff, is farily simple :) */
+/*** begin HotStuff protocol logic ***/
+HotStuffCore::HotStuffCore(ReplicaID id,
+                            privkey_bt &&priv_key,
+                            int32_t parent_limit):
+        b0(new Block(true, 1)),
+        bqc(b0),
+        bexec(b0),
+        vheight(0),
+        priv_key(std::move(priv_key)),
+        tails{bqc},
+        id(id),
+        parent_limit(parent_limit),
+        storage(new EntityStorage()) {
+    storage->add_blk(b0);
+    b0->qc_ref = b0;
+}
+
+void HotStuffCore::sanity_check_delivered(const block_t &blk) {
+    if (!blk->delivered)
+        throw std::runtime_error("block not delivered");
+}
+
+block_t HotStuffCore::sanity_check_delivered(const uint256_t &blk_hash) {
+    block_t blk = storage->find_blk(blk_hash);
+    if (blk == nullptr || !blk->delivered)
+        throw std::runtime_error("block not delivered");
+    return std::move(blk);
+}
+
+bool HotStuffCore::on_deliver_blk(const block_t &blk) {
+    if (blk->delivered)
+    {
+        LOG_WARN("attempt to deliver a block twice");
+        return false;
+    }
+    blk->parents.clear();
+    for (const auto &hash: blk->parent_hashes)
+    {
+        block_t p = sanity_check_delivered(hash);
+        blk->parents.push_back(p);
+    }
+    blk->height = blk->parents[0]->height + 1;
+    for (const auto &cmd: blk->cmds)
+        cmd->container = blk;
+
+    if (blk->qc)
+    {
+        block_t _blk = storage->find_blk(blk->qc->get_blk_hash());
+        if (_blk == nullptr)
+            throw std::runtime_error("block referred by qc not fetched");
+        blk->qc_ref = std::move(_blk);
+    } // otherwise blk->qc_ref remains null
+
+    for (auto pblk: blk->parents) tails.erase(pblk);
+    tails.insert(blk);
+
+    blk->delivered = true;
+    LOG_DEBUG("delivered %.10s", get_hex(blk->get_hash()).c_str());
+    return true;
+}
+
+void HotStuffCore::check_commit(const block_t &_blk) {
+    const block_t &blk = _blk->qc_ref;
+    if (blk->qc_ref == nullptr) return;
+    if (blk->decision) return;
+    block_t p = blk->parents[0];
+    if (p == blk->qc_ref)
+    { /* commit */
+        std::vector<block_t> commit_queue;
+        block_t b;
+        for (b = p; b->height > bexec->height; b = b->parents[0])
+        { /* todo: also commit the uncles/aunts */
+            commit_queue.push_back(b);
+        }
+        if (b != bexec)
+            throw std::runtime_error("safety breached :(");
+        for (auto it = commit_queue.rbegin(); it != commit_queue.rend(); it++)
+        {
+            const block_t &blk = *it;
+            blk->decision = 1;
+#ifdef HOTSTUFF_ENABLE_LOG_PROTO
+            LOG_INFO("commit blk %.10s", get_hex10(blk->get_hash()).c_str());
+#endif
+            for (auto cmd: blk->cmds)
+                do_decide(cmd);
+        }
+        bexec = p;
+    }
+}
+
+bool HotStuffCore::update(const uint256_t &bqc_hash) {
+    block_t _bqc = sanity_check_delivered(bqc_hash);
+    if (_bqc->qc_ref == nullptr) return false;
+    check_commit(_bqc);
+    if (_bqc->qc_ref->height > bqc->qc_ref->height)
+        bqc = _bqc;
+    return true;
+}
+
+void HotStuffCore::on_propose(const std::vector<command_t> &cmds) {
+    size_t nparents = parent_limit < 1 ? tails.size() : parent_limit;
+    assert(tails.size() > 0);
+    block_t p = *tails.rbegin();
+    std::vector<block_t> parents{p};
+    tails.erase(p);
+    nparents--;
+    /* add the rest of tails as "uncles/aunts" */
+    while (nparents--)
+    {
+        auto it = tails.begin();
+        parents.push_back(*it);
+        tails.erase(it);
+    }
+    quorum_cert_bt qc = nullptr;
+    block_t qc_ref = nullptr;
+    if (p != b0 && p->voted.size() >= config.nmajority)
+    {
+        qc = p->self_qc->clone();
+        qc->compute();
+        qc_ref = p;
+    }
+    /* create a new block */
+    block_t bnew = storage->add_blk(
+        Block(
+            parents,
+            cmds,
+            p->height + 1,
+            std::move(qc), qc_ref,
+            nullptr
+        ));
+    const uint256_t bnew_hash = bnew->get_hash();
+    bnew->self_qc = create_quorum_cert(bnew_hash);
+    on_deliver_blk(bnew);
+    update(bnew_hash);
+    Proposal prop(id, bqc->get_hash(), bnew, nullptr);
+#ifdef HOTSTUFF_ENABLE_LOG_PROTO
+    LOG_INFO("propose %s", std::string(*bnew).c_str());
+#endif
+    /* self-vote */
+    on_receive_vote(
+        Vote(id, bqc->get_hash(), bnew_hash,
+            create_part_cert(*priv_key, bnew_hash), this));
+    on_propose_(bnew);
+    /* boradcast to other replicas */
+    do_broadcast_proposal(prop);
+}
+
+void HotStuffCore::on_receive_proposal(const Proposal &prop) {
+    if (!update(prop.bqc_hash)) return;
+#ifdef HOTSTUFF_ENABLE_LOG_PROTO
+    LOG_INFO("got %s", std::string(prop).c_str());
+#endif
+    block_t bnew = prop.blk;
+    sanity_check_delivered(bnew);
+    bool opinion = false;
+    if (bnew->height > vheight)
+    {
+        block_t pref = bqc->qc_ref;
+        block_t b;
+        for (b = bnew;
+            b->height > pref->height;
+            b = b->parents[0]);
+        opinion = b == pref;
+        vheight = bnew->height;
+    }
+#ifdef HOTSTUFF_ENABLE_LOG_PROTO
+    LOG_INFO("now state: %s", std::string(*this).c_str());
+#endif
+    do_vote(prop.proposer,
+        Vote(id,
+            bqc->get_hash(),
+            bnew->get_hash(),
+            (opinion ?
+                create_part_cert(*priv_key, bnew->get_hash()) :
+                nullptr),
+            nullptr));
+}
+
+void HotStuffCore::on_receive_vote(const Vote &vote) {
+    if (!update(vote.bqc_hash)) return;
+#ifdef HOTSTUFF_ENABLE_LOG_PROTO
+    LOG_INFO("got %s", std::string(vote).c_str());
+    LOG_INFO("now state: %s", std::string(*this).c_str());
+#endif
+
+    block_t blk = sanity_check_delivered(vote.blk_hash);
+    if (vote.cert == nullptr) return;
+    if (!vote.verify())
+    {
+        LOG_WARN("invalid vote");
+        return;
+    }
+    if (!blk->voted.insert(vote.voter).second)
+    {
+        LOG_WARN("duplicate votes");
+        return;
+    }
+    size_t qsize = blk->voted.size();
+    if (qsize <= config.nmajority)
+    {
+        blk->self_qc->add_part(vote.voter, *vote.cert);
+        if (qsize == config.nmajority)
+            on_qc_finish(blk);
+    }
+}
+/*** end HotStuff protocol logic ***/
+
+void HotStuffCore::prune(uint32_t staleness) {
+    block_t start;
+    /* skip the blocks */
+    for (start = bexec; staleness; staleness--, start = start->parents[0])
+        if (!start->parents.size()) return;
+    std::stack<block_t> s;
+    start->qc_ref = nullptr;
+    s.push(start);
+    while (!s.empty())
+    {
+        auto &blk = s.top();
+        if (blk->parents.empty())
+        {
+            storage->try_release_blk(blk);
+            s.pop();
+            continue;
+        }
+        blk->qc_ref = nullptr;
+        s.push(blk->parents.back());
+        blk->parents.pop_back();
+    }
+}
+
+int8_t HotStuffCore::get_cmd_decision(const uint256_t &cmd_hash) {
+    auto cmd = storage->find_cmd(cmd_hash);
+    return cmd != nullptr ? cmd->get_decision() : 0;
+}
+
+void HotStuffCore::add_replica(ReplicaID rid, const NetAddr &addr,
+                                pubkey_bt &&pub_key) {
+    config.add_replica(rid, 
+            ReplicaInfo(rid, addr, std::move(pub_key)));
+    b0->voted.insert(rid);
+}
+
+promise_t HotStuffCore::async_qc_finish(const block_t &blk) {
+    if (blk->voted.size() >= config.nmajority)
+        return promise_t([](promise_t &pm) {
+            pm.resolve();
+        });
+    auto it = qc_waiting.find(blk);
+    if (it == qc_waiting.end())
+        it = qc_waiting.insert(std::make_pair(blk, promise_t())).first;
+    return it->second;
+}
+
+void HotStuffCore::on_qc_finish(const block_t &blk) {
+    auto it = qc_waiting.find(blk);
+    if (it != qc_waiting.end())
+    {
+        it->second.resolve();
+        qc_waiting.erase(it);
+    }
+}
+
+promise_t HotStuffCore::async_wait_propose() {
+    return propose_waiting;
+}
+
+void HotStuffCore::on_propose_(const block_t &blk) {
+    auto t = std::move(propose_waiting);
+    propose_waiting = promise_t();
+    t.resolve(blk);
+}
+
+HotStuffCore::operator std::string () const {
+    DataStream s;
+    s << "<hotstuff "
+      << "bqc=" << get_hex10(bqc->get_hash()) << " "
+      << "bexec=" << get_hex10(bqc->get_hash()) << " "
+      << "vheight=" << std::to_string(vheight) << " "
+      << "tails=" << std::to_string(tails.size()) << ">";
+    return std::string(std::move(s));
+}
+
+void HotStuffBase::add_replica(ReplicaID idx, const NetAddr &addr,
+                                pubkey_bt &&pub_key) {
+    HotStuffCore::add_replica(idx, addr, std::move(pub_key));
+    if (addr != listen_addr)
+        pn.add_peer(addr);
+}
+
+void HotStuffBase::on_fetch_blk(const block_t &blk) {
+#ifdef HOTSTUFF_ENABLE_TX_PROFILE
+    blk_profiler.get_tx(blk->get_hash());
+#endif
+    LOG_DEBUG("fetched %.10s", get_hex(blk->get_hash()).c_str());
+    part_fetched++;
+    fetched++;
+    for (auto cmd: blk->get_cmds()) on_fetch_cmd(cmd);
+    const uint256_t &blk_hash = blk->get_hash();
+    auto it = blk_fetch_waiting.find(blk_hash);
+    if (it != blk_fetch_waiting.end())
+    {
+        it->second.resolve(blk);
+        blk_fetch_waiting.erase(it);
+    }
+}
+
+void HotStuffBase::on_fetch_cmd(const command_t &cmd) {
+    const uint256_t &cmd_hash = cmd->get_hash();
+    auto it = cmd_fetch_waiting.find(cmd_hash);
+    if (it != cmd_fetch_waiting.end())
+    {
+        it->second.resolve(cmd);
+        cmd_fetch_waiting.erase(it);
+    }
+}
+
+void HotStuffBase::on_deliver_blk(const block_t &blk) {
+    const uint256_t &blk_hash = blk->get_hash();
+    bool valid;
+    /* sanity check: all parents must be delivered */
+    for (const auto &p: blk->get_parent_hashes())
+        assert(storage->is_blk_delivered(p));
+    if ((valid = HotStuffCore::on_deliver_blk(blk)))
+    {
+        LOG_DEBUG("block %.10s delivered",
+                get_hex(blk_hash).c_str());
+        part_parent_size += blk->get_parent_hashes().size();
+        part_delivered++;
+        delivered++;
+    }
+    else
+    {
+        LOG_WARN("dropping invalid block");
+    }
+
+    auto it = blk_delivery_waiting.find(blk_hash);
+    if (it != blk_delivery_waiting.end())
+    {
+        auto &pm = it->second;
+        if (valid)
+        {
+            pm.elapsed.stop(false);
+            auto sec = pm.elapsed.elapsed_sec;
+            part_delivery_time += sec;
+            part_delivery_time_min = std::min(part_delivery_time_min, sec);
+            part_delivery_time_max = std::max(part_delivery_time_max, sec);
+
+            pm.resolve(blk);
+        }
+        else
+        {
+            pm.reject(blk);
+            // TODO: do we need to also free it from storage?
+        }
+        blk_delivery_waiting.erase(it);
+    }
+}
+
+promise_t HotStuffBase::async_fetch_blk(const uint256_t &blk_hash,
+                                        const NetAddr *replica_id,
+                                        bool fetch_now) {
+    if (storage->is_blk_fetched(blk_hash))
+        return promise_t([this, &blk_hash](promise_t pm){
+            pm.resolve(storage->find_blk(blk_hash));
+        });
+    auto it = blk_fetch_waiting.find(blk_hash);
+    if (it == blk_fetch_waiting.end())
+    {
+#ifdef HOTSTUFF_ENABLE_TX_PROFILE
+        blk_profiler.rec_tx(blk_hash, false);
+#endif
+        it = blk_fetch_waiting.insert(
+            std::make_pair(
+                blk_hash,
+                BlockFetchContext(blk_hash, this))).first;
+    }
+    if (replica_id != nullptr)
+        it->second.add_replica(*replica_id, fetch_now);
+    return static_cast<promise_t &>(it->second);
+}
+
+promise_t HotStuffBase::async_fetch_cmd(const uint256_t &cmd_hash,
+                                    const NetAddr *replica_id,
+                                    bool fetch_now) {
+    if (storage->is_cmd_fetched(cmd_hash))
+        return promise_t([this, &cmd_hash](promise_t pm){
+            pm.resolve(storage->find_cmd(cmd_hash));
+        });
+    auto it = cmd_fetch_waiting.find(cmd_hash);
+    if (it == cmd_fetch_waiting.end())
+    {
+        it = cmd_fetch_waiting.insert(
+            std::make_pair(cmd_hash, CmdFetchContext(cmd_hash, this))).first;
+    }
+    if (replica_id != nullptr)
+        it->second.add_replica(*replica_id, fetch_now);
+    return static_cast<promise_t &>(it->second);
+}
+
+promise_t HotStuffBase::async_deliver_blk(const uint256_t &blk_hash,
+                                        const NetAddr &replica_id) {
+    if (storage->is_blk_delivered(blk_hash))
+        return promise_t([this, &blk_hash](promise_t pm) {
+            pm.resolve(storage->find_blk(blk_hash));
+        });
+    auto it = blk_delivery_waiting.find(blk_hash);
+    if (it != blk_delivery_waiting.end())
+        return static_cast<promise_t &>(it->second);
+    BlockDeliveryContext pm{[](promise_t){}};
+    it = blk_delivery_waiting.insert(std::make_pair(blk_hash, pm)).first;
+    /* otherwise the on_deliver_batch will resolve */
+    async_fetch_blk(blk_hash, &replica_id).then([this, replica_id](block_t blk) {
+        /* qc_ref should be fetched */
+        std::vector<promise_t> pms;
+        const auto &qc = blk->get_qc();
+        if (qc)
+            pms.push_back(async_fetch_blk(qc->get_blk_hash(), &replica_id));
+        /* the parents should be delivered */
+        for (const auto &phash: blk->get_parent_hashes())
+            pms.push_back(async_deliver_blk(phash, replica_id));
+        promise::all(pms).then([this, blk]() {
+            on_deliver_blk(blk);
+        });
+    });
+    return static_cast<promise_t &>(pm);
+}
+
+void HotStuffBase::propose_handler(const MsgHotStuff &msg, conn_t conn_) {
+    auto conn = static_pointer_cast<PeerNetwork<MsgHotStuff>::Conn>(conn_);
+    const NetAddr &peer = conn->get_peer();
+    Proposal prop(this);
+    msg.parse_propose(prop);
+    block_t blk = prop.blk;
+    promise::all(std::vector<promise_t>{
+        async_deliver_blk(prop.bqc_hash, peer),
+        async_deliver_blk(blk->get_hash(), peer),
+    }).then([this, prop = std::move(prop)]() {
+        on_receive_proposal(prop);
+    });
+}
+
+void HotStuffBase::vote_handler(const MsgHotStuff &msg, conn_t conn_) {
+    auto conn = static_pointer_cast<PeerNetwork<MsgHotStuff>::Conn>(conn_);
+    const NetAddr &peer = conn->get_peer();
+    Vote vote(this);
+    msg.parse_vote(vote);
+    promise::all(std::vector<promise_t>{
+        async_deliver_blk(vote.bqc_hash, peer),
+        async_deliver_blk(vote.blk_hash, peer)
+    }).then([this, vote = std::move(vote)]() {
+        on_receive_vote(vote);
+    });
+}
+
+void HotStuffBase::query_fetch_blk_handler(const MsgHotStuff &msg, conn_t conn_) {
+    auto conn = static_pointer_cast<PeerNetwork<MsgHotStuff>::Conn>(conn_);
+    const NetAddr replica = conn->get_peer();
+    std::vector<uint256_t> blk_hashes;
+    msg.parse_qfetchblk(blk_hashes);
+
+    std::vector<promise_t> pms;
+    for (const auto &h: blk_hashes)
+        pms.push_back(async_fetch_blk(h, nullptr));
+    promise::all(pms).then([replica, this](const promise::values_t values) {
+        MsgHotStuff resp;
+        std::vector<block_t> blks;
+        for (auto &v: values)
+        {
+            auto blk = promise::any_cast<block_t>(v);
+            blks.push_back(blk);
+        }
+        resp.gen_rfetchblk(blks);
+        pn.send_msg(resp, replica);
+    });
+}
+
+void HotStuffBase::resp_fetch_blk_handler(const MsgHotStuff &msg, conn_t) {
+    std::vector<block_t> blks;
+    msg.parse_rfetchblk(blks, this);
+    for (const auto &blk: blks)
+        if (blk) on_fetch_blk(blk);
+}
+
+void HotStuffBase::print_stat() const {
+    LOG_INFO("===== begin stats =====");
+    LOG_INFO("-------- queues -------");
+    LOG_INFO("blk_fetch_waiting: %lu", blk_fetch_waiting.size());
+    LOG_INFO("blk_delivery_waiting: %lu", blk_delivery_waiting.size());
+    LOG_INFO("cmd_fetch_waiting: %lu", cmd_fetch_waiting.size());
+    LOG_INFO("decision_waiting: %lu", decision_waiting.size());
+    LOG_INFO("-------- misc ---------");
+    LOG_INFO("fetched: %lu", fetched);
+    LOG_INFO("delivered: %lu", delivered);
+    LOG_INFO("cmd_cache: %lu", storage->get_cmd_cache_size());
+    LOG_INFO("blk_cache: %lu", storage->get_blk_cache_size());
+    LOG_INFO("------ misc (10s) -----");
+    LOG_INFO("fetched: %lu", part_fetched);
+    LOG_INFO("delivered: %lu", part_delivered);
+    LOG_INFO("decided: %lu", part_decided);
+    LOG_INFO("gened: %lu", part_gened);
+    LOG_INFO("avg. parent_size: %.3f",
+            part_delivered ? part_parent_size / double(part_delivered) : 0);
+    LOG_INFO("delivery time: %.3f avg, %.3f min, %.3f max",
+            part_delivered ? part_delivery_time / double(part_delivered) : 0,
+            part_delivery_time_min == double_inf ? 0 : part_delivery_time_min,
+            part_delivery_time_max);
+
+    part_parent_size = 0;
+    part_fetched = 0;
+    part_delivered = 0;
+    part_decided = 0;
+    part_gened = 0;
+    part_delivery_time = 0;
+    part_delivery_time_min = double_inf;
+    part_delivery_time_max = 0;
+    LOG_INFO("-- sent opcode (10s) --");
+    auto &sent_op = pn.get_sent_by_opcode();
+    for (auto &op: sent_op)
+    {
+        auto &val = op.second;
+        LOG_INFO("%02x: %lu, %.2fBpm", op.first,
+                val.first, val.first ? val.second / double(val.first) : 0);
+        val.first = val.second = 0;
+    }
+    LOG_INFO("-- recv opcode (10s) --");
+    auto &recv_op = pn.get_recv_by_opcode();
+    for (auto &op: recv_op)
+    {
+        auto &val = op.second;
+        LOG_INFO("%02x: %lu, %.2fBpm", op.first,
+                val.first, val.first ? val.second / double(val.first) : 0);
+        val.first = val.second = 0;
+    }
+    LOG_INFO("--- replica msg. (10s) ---");
+    size_t _nsent = 0;
+    size_t _nrecv = 0;
+    for (const auto &replica: pn.all_peers())
+    {
+        auto conn = pn.get_peer_conn(replica);
+        size_t ns = conn->get_nsent();
+        size_t nr = conn->get_nrecv();
+        conn->clear_nsent();
+        conn->clear_nrecv();
+        LOG_INFO("%s: %u, %u, %u",
+            std::string(replica).c_str(), ns, nr, part_fetched_replica[replica]);
+        _nsent += ns;
+        _nrecv += nr;
+        part_fetched_replica[replica] = 0;
+    }
+    nsent += _nsent;
+    nrecv += _nrecv;
+    LOG_INFO("sent: %lu", _nsent);
+    LOG_INFO("recv: %lu", _nrecv);
+    LOG_INFO("--- replica msg. total ---");
+    LOG_INFO("sent: %lu", nsent);
+    LOG_INFO("recv: %lu", nrecv);
+    LOG_INFO("====== end stats ======");
+}
+
+promise_t HotStuffBase::async_decide(const uint256_t &cmd_hash) {
+    if (get_cmd_decision(cmd_hash))
+        return promise_t([this, cmd_hash](promise_t pm){
+            pm.resolve(storage->find_cmd(cmd_hash));
+        });
+    /* otherwise the do_decide will resolve the promise */
+    auto it = decision_waiting.find(cmd_hash);
+    if (it == decision_waiting.end())
+    {
+        promise_t pm{[](promise_t){}};
+        it = decision_waiting.insert(std::make_pair(cmd_hash, pm)).first;
+    }
+    return it->second;
+}
+
+HotStuffBase::HotStuffBase(uint32_t blk_size,
+                    int32_t parent_limit,
+                    ReplicaID rid,
+                    privkey_bt &&priv_key,
+                    NetAddr listen_addr,
+                    EventContext eb,
+                    pacemaker_bt pmaker):
+        HotStuffCore(rid, std::move(priv_key), parent_limit),
+        listen_addr(listen_addr),
+        blk_size(blk_size),
+        eb(eb),
+        pmaker(std::move(pmaker)),
+        pn(eb),
+
+        fetched(0), delivered(0),
+        nsent(0), nrecv(0),
+        part_parent_size(0),
+        part_fetched(0),
+        part_delivered(0),
+        part_decided(0),
+        part_gened(0),
+        part_delivery_time(0),
+        part_delivery_time_min(double_inf),
+        part_delivery_time_max(0)
+{
+    if (pmaker == nullptr)
+        this->pmaker = new PaceMakerDummy(this);
+    /* register the handlers for msg from replicas */
+    pn.reg_handler(PROPOSE, std::bind(&HotStuffBase::propose_handler, this, _1, _2));
+    pn.reg_handler(VOTE, std::bind(&HotStuffBase::vote_handler, this, _1, _2));
+    pn.reg_handler(QUERY_FETCH_BLK, std::bind(&HotStuffBase::query_fetch_blk_handler, this, _1, _2));
+    pn.reg_handler(RESP_FETCH_BLK, std::bind(&HotStuffBase::resp_fetch_blk_handler, this, _1, _2));
+    pn.init(listen_addr);
+}
+
+void HotStuffBase::do_broadcast_proposal(const Proposal &prop) {
+    MsgHotStuff prop_msg;
+    prop_msg.gen_propose(prop);
+    for (const auto &replica: pn.all_peers())
+        pn.send_msg(prop_msg, replica);
+}
+
+void HotStuffBase::do_vote(ReplicaID last_proposer, const Vote &vote) {
+    MsgHotStuff vote_msg;
+    vote_msg.gen_vote(vote);
+    pmaker->next_proposer(last_proposer)
+            .then([this, vote_msg](ReplicaID proposer) {
+        pn.send_msg(vote_msg, get_config().get_addr(proposer));
+    });
+}
+
+void HotStuffBase::do_decide(const command_t &cmd) {
+    auto it = decision_waiting.find(cmd->get_hash());
+    if (it != decision_waiting.end())
+    {
+        it->second.resolve(cmd);
+        decision_waiting.erase(it);
+    }
+}
+
+HotStuffBase::~HotStuffBase() {}
+
+void HotStuffBase::start(bool eb_loop) {
+    /* ((n - 1) + 1 - 1) / 3 */
+    uint32_t nfaulty = pn.all_peers().size() / 3;
+    if (nfaulty == 0)
+        LOG_WARN("too few replicas in the system to tolerate any failure");
+    on_init(nfaulty);
+    if (eb_loop)
+        eb.dispatch();
+}
+
+}
diff --git a/src/core.h b/src/core.h
new file mode 100644
index 0000000..c7e1fe6
--- /dev/null
+++ b/src/core.h
@@ -0,0 +1,631 @@
+#ifndef _HOTSTUFF_CORE_H
+#define _HOTSTUFF_CORE_H
+
+#include <queue>
+#include <set>
+#include <unordered_map>
+#include <unordered_set>
+
+#include "salticidae/stream.h"
+#include "salticidae/util.h"
+#include "salticidae/network.h"
+#include "salticidae/msg.h"
+
+#include "promise.hpp"
+#include "util.h"
+#include "entity.h"
+#include "crypto.h"
+
+using salticidae::EventContext;
+using salticidae::Event;
+using salticidae::NetAddr;
+using salticidae::MsgNetwork;
+using salticidae::PeerNetwork;
+using salticidae::ElapsedTime;
+using salticidae::_1;
+using salticidae::_2;
+
+namespace hotstuff {
+
+const double ent_waiting_timeout = 10;
+const double double_inf = 1e10;
+
+enum {
+    PROPOSE = 0x0,
+    VOTE = 0x1,
+    QUERY_FETCH_BLK = 0x2,
+    RESP_FETCH_BLK = 0x3,
+};
+
+using promise::promise_t;
+
+struct Proposal;
+struct Vote;
+
+/** Abstraction for HotStuff protocol state machine (without network implementation). */
+class HotStuffCore {
+    block_t b0;                                  /** the genesis block */
+    /* === state variables === */
+    /** block containing the QC for the highest block having one */
+    block_t bqc;
+    block_t bexec;                            /**< last executed block */
+    uint32_t vheight;          /**< height of the block last voted for */
+    /* === auxilliary variables === */
+    privkey_bt priv_key;            /**< private key for signing votes */
+    std::set<block_t, BlockHeightCmp> tails;   /**< set of tail blocks */
+    ReplicaConfig config;                   /**< replica configuration */
+    /* === async event queues === */
+    std::unordered_map<block_t, promise_t> qc_waiting;
+    promise_t propose_waiting;
+
+    block_t sanity_check_delivered(const uint256_t &blk_hash);
+    void sanity_check_delivered(const block_t &blk);
+    void check_commit(const block_t &_bqc);
+    bool update(const uint256_t &bqc_hash);
+    void on_qc_finish(const block_t &blk);
+    void on_propose_(const block_t &blk);
+
+    protected:
+    ReplicaID id;                  /**< identity of the replica itself */
+    const int32_t parent_limit;         /**< maximum number of parents */
+
+    public:
+    BoxObj<EntityStorage> storage;
+
+    HotStuffCore(ReplicaID id,
+                privkey_bt &&priv_key,
+                int32_t parent_limit);
+    virtual ~HotStuffCore() = default;
+
+    /* Inputs of the state machine triggered by external events, should called
+     * by the class user, with proper invariants. */
+
+    /** Call to initialize the protocol, should be called once before all other
+     * functions. */
+    void on_init(uint32_t nfaulty) { config.nmajority = 2 * nfaulty + 1; }
+
+    /** Call to deliver a block.
+     * A block is only delivered if itself is fetched, the block for the
+     * contained qc is fetched and all parents are delivered. The user should
+     * always ensure this invariant. The invalid blocks will be dropped by this
+     * function.
+     * @return true if valid */
+    bool on_deliver_blk(const block_t &blk);
+
+    /** Call upon the delivery of a proposal message.
+     * The block mentioned in the message should be already delivered. */
+    void on_receive_proposal(const Proposal &prop);
+
+    /** Call upon the delivery of a vote message.
+     * The block mentioned in the message should be already delivered. */
+    void on_receive_vote(const Vote &vote);
+
+    /** Call to submit new commands to be decided (executed). */
+    void on_propose(const std::vector<command_t> &cmds);
+
+    /* Functions required to construct concrete instances for abstract classes.
+     * */
+
+    /* Outputs of the state machine triggering external events.  The virtual
+     * functions should be implemented by the user to specify the behavior upon
+     * the events. */
+    protected:
+    /** Called by HotStuffCore upon the decision being made for cmd. */
+    virtual void do_decide(const command_t &cmd) = 0;
+    /** Called by HotStuffCore upon broadcasting a new proposal.
+     * The user should send the proposal message to all replicas except for
+     * itself. */
+    virtual void do_broadcast_proposal(const Proposal &prop) = 0;
+    /** Called upon sending out a new vote to the next proposer.  The user
+     * should send the vote message to a *good* proposer to have good liveness,
+     * while safety is always guaranteed by HotStuffCore. */
+    virtual void do_vote(ReplicaID last_proposer, const Vote &vote) = 0;
+
+    /* The user plugs in the detailed instances for those
+     * polymorphic data types. */
+    public:
+    /** Create a partial certificate that proves the vote for a block. */
+    virtual part_cert_bt create_part_cert(const PrivKey &priv_key, const uint256_t &blk_hash) = 0;
+    /** Create a partial certificate from its seralized form. */
+    virtual part_cert_bt parse_part_cert(DataStream &s) = 0;
+    /** Create a quorum certificate that proves 2f+1 votes for a block. */
+    virtual quorum_cert_bt create_quorum_cert(const uint256_t &blk_hash) = 0;
+    /** Create a quorum certificate from its serialized form. */
+    virtual quorum_cert_bt parse_quorum_cert(DataStream &s) = 0;
+    /** Create a command object from its serialized form. */
+    virtual command_t parse_cmd(DataStream &s) = 0;
+
+    public:
+    /** Add a replica to the current configuration. This should only be called
+     * before running HotStuffCore protocol. */
+    void add_replica(ReplicaID rid, const NetAddr &addr, pubkey_bt &&pub_key);
+    /** Try to prune blocks lower than last committed height - staleness. */
+    void prune(uint32_t staleness);
+
+    /* PaceMaker can use these functions to monitor the core protocol state
+     * transition */
+    /** Get a promise resolved when the block gets a QC. */
+    promise_t async_qc_finish(const block_t &blk);
+    /** Get a promise resolved when a new block is proposed. */
+    promise_t async_wait_propose();
+
+    /* Other useful functions */
+    block_t get_genesis() { return b0; }
+    const ReplicaConfig &get_config() { return config; }
+    int8_t get_cmd_decision(const uint256_t &cmd_hash);
+    ReplicaID get_id() { return id; }
+    operator std::string () const;
+};
+
+/** Abstraction for proposal messages. */
+struct Proposal: public Serializable {
+    ReplicaID proposer;
+    /** hash for the block containing the highest QC */
+    uint256_t bqc_hash;
+    /** block being proposed */
+    block_t blk;
+
+    /** handle of the core object to allow polymorphism. The user should use
+     * a pointer to the object of the class derived from HotStuffCore */
+    HotStuffCore *hsc;
+
+    Proposal(HotStuffCore *hsc): blk(nullptr), hsc(hsc) {}
+    Proposal(ReplicaID proposer,
+            const uint256_t &bqc_hash,
+            block_t &blk,
+            HotStuffCore *hsc):
+        proposer(proposer),
+        bqc_hash(bqc_hash),
+        blk(blk), hsc(hsc) {}
+
+    void serialize(DataStream &s) const override {
+        s << proposer
+          << bqc_hash
+          << *blk;
+    }
+
+    void unserialize(DataStream &s) override {
+        assert(hsc != nullptr);
+        s >> proposer
+          >> bqc_hash;
+        Block _blk;
+        _blk.unserialize(s, hsc);
+        blk = hsc->storage->add_blk(std::move(_blk));
+    }
+
+    operator std::string () const {
+        DataStream s;
+        s << "<proposal "
+          << "rid=" << std::to_string(proposer) << " "
+          << "bqc=" << get_hex10(bqc_hash) << " "
+          << "blk=" << get_hex10(blk->get_hash()) << ">";
+        return std::string(std::move(s));
+    }
+};
+
+/** Abstraction for vote messages. */
+struct Vote: public Serializable {
+    ReplicaID voter;
+    /** hash for the block containing the highest QC */
+    uint256_t bqc_hash;
+    /** block being voted */
+    uint256_t blk_hash;
+    /** proof of validity for the vote (nullptr for a negative vote) */
+    part_cert_bt cert;
+    
+    /** handle of the core object to allow polymorphism */
+    HotStuffCore *hsc;
+
+    Vote(HotStuffCore *hsc): cert(nullptr), hsc(hsc) {}
+    Vote(ReplicaID voter,
+        const uint256_t &bqc_hash,
+        const uint256_t &blk_hash,
+        part_cert_bt &&cert,
+        HotStuffCore *hsc):
+        voter(voter),
+        bqc_hash(bqc_hash),
+        blk_hash(blk_hash),
+        cert(std::move(cert)), hsc(hsc) {}
+
+    Vote(const Vote &other):
+        voter(other.voter),
+        bqc_hash(other.bqc_hash),
+        blk_hash(other.blk_hash),
+        cert(other.cert->clone()),
+        hsc(other.hsc) {}
+
+    Vote(Vote &&other) = default;
+    
+    void serialize(DataStream &s) const override {
+        s << voter
+          << bqc_hash
+          << blk_hash;
+        if (cert == nullptr)
+            s << (uint8_t)0;
+        else
+            s << (uint8_t)1 << *cert;
+    }
+
+    void unserialize(DataStream &s) override {
+        assert(hsc != nullptr);
+        uint8_t has_cert;
+        s >> voter
+          >> bqc_hash
+          >> blk_hash
+          >> has_cert;
+        cert = has_cert ? hsc->parse_part_cert(s) : nullptr;
+    }
+
+    bool verify() const {
+        assert(hsc != nullptr);
+        return cert->verify(hsc->get_config().get_pubkey(voter)) &&
+                cert->get_blk_hash() == blk_hash;
+    }
+
+    operator std::string () const {
+        DataStream s;
+        s << "<vote "
+          << "rid=" << std::to_string(voter) << " "
+          << "bqc=" << get_hex10(bqc_hash) << " "
+          << "blk=" << get_hex10(blk_hash) << " "
+          << "cert=" << (cert ? "yes" : "no") << ">";
+        return std::string(std::move(s));
+    }
+};
+
+/** Abstraction for liveness gadget (oracle). */
+class PaceMaker {
+    public:
+    virtual ~PaceMaker() = default;
+    /** Get a promise resolved when the pace maker thinks it is a *good* time
+     * to issue new commands. When promise is resolved with the ID of itself,
+     * the replica should propose the command, otherwise it will forward the
+     * command to the proposer indicated by the ID. */
+    virtual promise_t beat() = 0;
+    /** Get a promise resolved when the pace maker thinks it is a *good* time
+     * to vote for a block. The promise is resolved with the next proposer's ID
+     * */
+    virtual promise_t next_proposer(ReplicaID last_proposer) = 0;
+};
+
+using pacemaker_bt = BoxObj<PaceMaker>;
+
+/** A pace maker that waits for the qc of the last proposed block. */
+class PaceMakerDummy: public PaceMaker {
+    HotStuffCore *hsc;
+    std::queue<promise_t> pending_beats;
+    block_t last_proposed;
+    bool locked;
+
+    void schedule_next() {
+        if (!pending_beats.empty() && !locked)
+        {
+            auto pm = pending_beats.front();
+            pending_beats.pop();
+            hsc->async_qc_finish(last_proposed).then(
+                    [id = hsc->get_id(), pm]() {
+                pm.resolve(id);
+            });
+            locked = true;
+        }
+    }
+
+    void update_last_proposed() {
+        hsc->async_wait_propose().then([this](block_t blk) {
+            update_last_proposed();
+            last_proposed = blk;
+            locked = false;
+            schedule_next();
+        });
+    }
+
+    public:
+    PaceMakerDummy(HotStuffCore *hsc):
+            hsc(hsc),
+            last_proposed(hsc->get_genesis()),
+            locked(false) {
+        update_last_proposed();
+    }
+
+    promise_t beat() override {
+        promise_t pm;
+        pending_beats.push(pm);
+        schedule_next();
+        return pm;
+    }
+
+    promise_t next_proposer(ReplicaID last_proposer) override {
+        return promise_t([last_proposer](promise_t &pm) {
+            pm.resolve(last_proposer);
+        });
+    }
+};
+
+/** Network message format for HotStuff. */
+struct MsgHotStuff: public salticidae::MsgBase<> {
+    using MsgBase::MsgBase;
+    void gen_propose(const Proposal &);
+    void parse_propose(Proposal &) const;
+
+    void gen_vote(const Vote &);
+    void parse_vote(Vote &) const;
+
+    void gen_qfetchblk(const std::vector<uint256_t> &blk_hashes);
+    void parse_qfetchblk(std::vector<uint256_t> &blk_hashes) const;
+
+    void gen_rfetchblk(const std::vector<block_t> &blks);
+    void parse_rfetchblk(std::vector<block_t> &blks, HotStuffCore *hsc) const;
+};
+
+using promise::promise_t;
+
+class HotStuffBase;
+
+template<EntityType ent_type>
+class FetchContext: public promise_t {
+    Event timeout;
+    HotStuffBase *hs;
+    MsgHotStuff fetch_msg;
+    const uint256_t ent_hash;
+    std::unordered_set<NetAddr> replica_ids;
+    inline void timeout_cb(evutil_socket_t, short);
+    public:
+    FetchContext(const FetchContext &) = delete;
+    FetchContext &operator=(const FetchContext &) = delete;
+    FetchContext(FetchContext &&other);
+
+    FetchContext(const uint256_t &ent_hash, HotStuffBase *hs);
+    ~FetchContext() {}
+
+    inline void send(const NetAddr &replica_id);
+    inline void reset_timeout();
+    inline void add_replica(const NetAddr &replica_id, bool fetch_now = true);
+};
+
+class BlockDeliveryContext: public promise_t {
+    public:
+    ElapsedTime elapsed;
+    BlockDeliveryContext &operator=(const BlockDeliveryContext &) = delete;
+    BlockDeliveryContext(const BlockDeliveryContext &other):
+        promise_t(static_cast<const promise_t &>(other)),
+        elapsed(other.elapsed) {}
+    BlockDeliveryContext(BlockDeliveryContext &&other):
+        promise_t(static_cast<const promise_t &>(other)),
+        elapsed(std::move(other.elapsed)) {}
+    template<typename Func>
+    BlockDeliveryContext(Func callback): promise_t(callback) {
+        elapsed.start();
+    }
+};
+
+
+/** HotStuff protocol (with network implementation). */
+class HotStuffBase: public HotStuffCore {
+    using BlockFetchContext = FetchContext<ENT_TYPE_BLK>;
+    using CmdFetchContext = FetchContext<ENT_TYPE_CMD>;
+    using conn_t = MsgNetwork<MsgHotStuff>::conn_t;
+
+    friend BlockFetchContext;
+    friend CmdFetchContext;
+
+    protected:
+    /** the binding address in replica network */
+    NetAddr listen_addr;
+    /** the block size */
+    size_t blk_size;
+    /** libevent handle */
+    EventContext eb;
+    pacemaker_bt pmaker;
+
+    private:
+    /** whether libevent handle is owned by itself */
+    bool eb_loop;
+    /** network stack */
+    PeerNetwork<MsgHotStuff> pn;
+#ifdef HOTSTUFF_ENABLE_BLK_PROFILE
+    BlockProfiler blk_profiler;
+#endif
+    /* queues for async tasks */
+    std::unordered_map<const uint256_t, BlockFetchContext> blk_fetch_waiting;
+    std::unordered_map<const uint256_t, BlockDeliveryContext> blk_delivery_waiting;
+    std::unordered_map<const uint256_t, CmdFetchContext> cmd_fetch_waiting;
+    std::unordered_map<const uint256_t, promise_t> decision_waiting;
+    std::queue<command_t> cmd_pending;
+
+    /* statistics */
+    uint64_t fetched;
+    uint64_t delivered;
+    mutable uint64_t nsent;
+    mutable uint64_t nrecv;
+
+    mutable uint32_t part_parent_size;
+    mutable uint32_t part_fetched;
+    mutable uint32_t part_delivered;
+    mutable uint32_t part_decided;
+    mutable uint32_t part_gened;
+    mutable double part_delivery_time;
+    mutable double part_delivery_time_min;
+    mutable double part_delivery_time_max;
+    mutable std::unordered_map<const NetAddr, uint32_t> part_fetched_replica;
+
+    void on_fetch_cmd(const command_t &cmd);
+    void on_fetch_blk(const block_t &blk);
+    void on_deliver_blk(const block_t &blk);
+
+    /** deliver consensus message: <propose> */
+    inline void propose_handler(const MsgHotStuff &, conn_t);
+    /** deliver consensus message: <vote> */
+    inline void vote_handler(const MsgHotStuff &, conn_t);
+    /** fetches full block data */
+    inline void query_fetch_blk_handler(const MsgHotStuff &, conn_t);
+    /** receives a block */
+    inline void resp_fetch_blk_handler(const MsgHotStuff &, conn_t);
+
+    void do_broadcast_proposal(const Proposal &) override;
+    void do_vote(ReplicaID, const Vote &) override;
+    void do_decide(const command_t &) override;
+
+    public:
+    HotStuffBase(uint32_t blk_size,
+            int32_t parent_limit,
+            ReplicaID rid,
+            privkey_bt &&priv_key,
+            NetAddr listen_addr,
+            EventContext eb = EventContext(),
+            pacemaker_bt pmaker = nullptr);
+
+    ~HotStuffBase();
+
+    /* the API for HotStuffBase */
+
+    /* Submit the command to be decided. */
+    void add_command(command_t cmd) {
+        cmd_pending.push(storage->add_cmd(cmd));
+        if (cmd_pending.size() >= blk_size)
+        {
+            std::vector<command_t> cmds;
+            for (uint32_t i = 0; i < blk_size; i++)
+            {
+                cmds.push_back(cmd_pending.front());
+                cmd_pending.pop();
+            }
+            pmaker->beat().then([this, cmds = std::move(cmds)]() {
+                on_propose(cmds);
+            });
+        }
+    }
+
+    void add_replica(ReplicaID idx, const NetAddr &addr, pubkey_bt &&pub_key);
+    void start(bool eb_loop = false);
+
+    size_t size() const { return pn.all_peers().size(); }
+    void print_stat() const;
+
+    /* Helper functions */
+    /** Returns a promise resolved (with command_t cmd) when Command is fetched. */
+    promise_t async_fetch_cmd(const uint256_t &cmd_hash, const NetAddr *replica_id, bool fetch_now = true);
+    /** Returns a promise resolved (with block_t blk) when Block is fetched. */
+    promise_t async_fetch_blk(const uint256_t &blk_hash, const NetAddr *replica_id, bool fetch_now = true);
+    /** Returns a promise resolved (with block_t blk) when Block is delivered (i.e. prefix is fetched). */
+    promise_t async_deliver_blk(const uint256_t &blk_hash,  const NetAddr &replica_id);
+    /** Returns a promise resolved (with command_t cmd) when Command is decided. */
+    promise_t async_decide(const uint256_t &cmd_hash);
+};
+
+/** HotStuff protocol (templated by cryptographic implementation). */
+template<typename PrivKeyType = PrivKeyDummy,
+        typename PubKeyType = PubKeyDummy,
+        typename PartCertType = PartCertDummy,
+        typename QuorumCertType = QuorumCertDummy>
+class HotStuff: public HotStuffBase {
+    using HotStuffBase::HotStuffBase;
+    protected:
+
+    part_cert_bt create_part_cert(const PrivKey &priv_key, const uint256_t &blk_hash) override {
+        return new PartCertType(
+                    static_cast<const PrivKeyType &>(priv_key),
+                    blk_hash);
+    }
+
+    part_cert_bt parse_part_cert(DataStream &s) override {
+        PartCert *pc = new PartCertType();
+        s >> *pc;
+        return pc;
+    }
+
+    quorum_cert_bt create_quorum_cert(const uint256_t &blk_hash) override {
+        return new QuorumCertType(get_config(), blk_hash);
+    }
+
+    quorum_cert_bt parse_quorum_cert(DataStream &s) override {
+        QuorumCert *qc = new QuorumCertType();
+        s >> *qc;
+        return qc;
+    }
+
+    public:
+    HotStuff(uint32_t blk_size,
+            int32_t parent_limit,
+            ReplicaID rid,
+            const bytearray_t &raw_privkey,
+            NetAddr listen_addr,
+            EventContext eb = nullptr):
+        HotStuffBase(blk_size,
+                    parent_limit,
+                    rid,
+                    new PrivKeyType(raw_privkey),
+                    listen_addr,
+                    eb) {}
+
+    void add_replica(ReplicaID idx, const NetAddr &addr, const bytearray_t &pubkey_raw) {
+        DataStream s(pubkey_raw);
+        HotStuffBase::add_replica(idx, addr, new PubKeyType(pubkey_raw));
+    }
+};
+
+using HotStuffNoSig = HotStuff<>;
+using HotStuffSecp256k1 = HotStuff<PrivKeySecp256k1, PubKeySecp256k1,
+                                    PartCertSecp256k1, QuorumCertSecp256k1>;
+
+template<EntityType ent_type>
+FetchContext<ent_type>::FetchContext(FetchContext && other):
+        promise_t(static_cast<const promise_t &>(other)),
+        hs(other.hs),
+        fetch_msg(std::move(other.fetch_msg)),
+        ent_hash(other.ent_hash),
+        replica_ids(std::move(other.replica_ids)) {
+    other.timeout.del();
+    timeout = Event(hs->eb, -1, 0,
+            std::bind(&FetchContext::timeout_cb, this, _1, _2));
+    reset_timeout();
+}
+
+template<>
+inline void FetchContext<ENT_TYPE_CMD>::timeout_cb(evutil_socket_t, short) {
+    HOTSTUFF_LOG_WARN("cmd fetching %.10s timeout", get_hex(ent_hash).c_str());
+    for (const auto &replica_id: replica_ids)
+        send(replica_id);
+    reset_timeout();
+}
+
+template<>
+inline void FetchContext<ENT_TYPE_BLK>::timeout_cb(evutil_socket_t, short) {
+    HOTSTUFF_LOG_WARN("block fetching %.10s timeout", get_hex(ent_hash).c_str());
+    for (const auto &replica_id: replica_ids)
+        send(replica_id);
+    reset_timeout();
+}
+
+template<EntityType ent_type>
+FetchContext<ent_type>::FetchContext(
+                                const uint256_t &ent_hash, HotStuffBase *hs):
+            promise_t([](promise_t){}),
+            hs(hs), ent_hash(ent_hash) {
+    fetch_msg.gen_qfetchblk(std::vector<uint256_t>{ent_hash});
+
+    timeout = Event(hs->eb, -1, 0,
+            std::bind(&FetchContext::timeout_cb, this, _1, _2));
+    reset_timeout();
+}
+
+template<EntityType ent_type>
+void FetchContext<ent_type>::send(const NetAddr &replica_id) {
+    hs->part_fetched_replica[replica_id]++;
+    hs->pn.send_msg(fetch_msg, replica_id);
+}
+
+template<EntityType ent_type>
+void FetchContext<ent_type>::reset_timeout() {
+    timeout.add_with_timeout(salticidae::gen_rand_timeout(ent_waiting_timeout));
+}
+
+template<EntityType ent_type>
+void FetchContext<ent_type>::add_replica(const NetAddr &replica_id, bool fetch_now) {
+    if (replica_ids.empty() && fetch_now)
+        send(replica_id);
+    replica_ids.insert(replica_id);
+}
+
+}
+
+#endif
diff --git a/src/crypto.cpp b/src/crypto.cpp
new file mode 100644
index 0000000..335a521
--- /dev/null
+++ b/src/crypto.cpp
@@ -0,0 +1,25 @@
+#include "entity.h"
+#include "crypto.h"
+
+namespace hotstuff {
+
+secp256k1_context_t secp256k1_default_sign_ctx = new Secp256k1Context(true);
+secp256k1_context_t secp256k1_default_verify_ctx = new Secp256k1Context(false);
+
+QuorumCertSecp256k1::QuorumCertSecp256k1(
+        const ReplicaConfig &config, const uint256_t &blk_hash):
+            QuorumCert(), blk_hash(blk_hash), rids(config.nmajority) {
+    rids.clear();
+}
+   
+bool QuorumCertSecp256k1::verify(const ReplicaConfig &config) {
+    bytearray_t _blk_hash(blk_hash);
+    if (rids.size() < config.nmajority) return false;
+    for (size_t i = 0; i < rids.size(); i++)
+        if (!sigs[i].verify(_blk_hash,
+                            static_cast<const PubKeySecp256k1 &>(config.get_pubkey(rids.get(i)))))
+            return false;
+    return true;
+}
+
+}
diff --git a/src/crypto.h b/src/crypto.h
new file mode 100644
index 0000000..2fbf745
--- /dev/null
+++ b/src/crypto.h
@@ -0,0 +1,386 @@
+#ifndef _HOTSTUFF_CRYPTO_H
+#define _HOTSTUFF_CRYPTO_H
+
+#include "salticidae/crypto.h"
+#include "salticidae/ref.h"
+#include "secp256k1.h"
+#include <openssl/rand.h>
+#include "type.h"
+
+using salticidae::RcObj;
+using salticidae::BoxObj;
+
+namespace hotstuff {
+
+using salticidae::SHA256;
+
+class PubKey: public Serializable, Cloneable {
+    public:
+    virtual ~PubKey() = default;
+    virtual PubKey *clone() override = 0;
+};
+
+using pubkey_bt = BoxObj<PubKey>;
+
+class PrivKey: public Serializable {
+    public:
+    virtual ~PrivKey() = default;
+    virtual pubkey_bt get_pubkey() const = 0;
+    virtual void from_rand() = 0;
+};
+
+using privkey_bt = BoxObj<PrivKey>;
+
+class PartCert: public Serializable, public Cloneable {
+    public:
+    virtual ~PartCert() = default;
+    virtual bool verify(const PubKey &pubkey) = 0;
+    virtual const uint256_t &get_blk_hash() const = 0;
+    virtual PartCert *clone() override = 0;
+};
+
+class ReplicaConfig;
+
+class QuorumCert: public Serializable, public Cloneable {
+    public:
+    virtual ~QuorumCert() = default;
+    virtual void add_part(ReplicaID replica, const PartCert &pc) = 0;
+    virtual void compute() = 0;
+    virtual bool verify(const ReplicaConfig &config) = 0;
+    virtual const uint256_t &get_blk_hash() const = 0;
+    virtual QuorumCert *clone() override = 0;
+};
+
+using part_cert_bt = BoxObj<PartCert>;
+using quorum_cert_bt = BoxObj<QuorumCert>;
+
+class PubKeyDummy: public PubKey {
+    PubKeyDummy *clone() override { return new PubKeyDummy(*this); }
+    void serialize(DataStream &) const override {}
+    void unserialize(DataStream &) override {}
+};
+
+class PrivKeyDummy: public PrivKey {
+    pubkey_bt get_pubkey() const override { return new PubKeyDummy(); }
+    void serialize(DataStream &) const override {}
+    void unserialize(DataStream &) override {}
+    void from_rand() override {}
+};
+
+class PartCertDummy: public PartCert {
+    uint256_t blk_hash;
+    public:
+    PartCertDummy() {}
+    PartCertDummy(const uint256_t &blk_hash):
+        blk_hash(blk_hash) {}
+
+    void serialize(DataStream &s) const override {
+        s << (uint32_t)0 << blk_hash;
+    }
+
+    void unserialize(DataStream &s) override {
+        uint32_t tmp;
+        s >> tmp >> blk_hash;
+    }
+
+    PartCert *clone() override {
+        return new PartCertDummy(blk_hash);
+    }
+
+    bool verify(const PubKey &) override { return true; }
+
+    const uint256_t &get_blk_hash() const override { return blk_hash; }
+};
+
+class QuorumCertDummy: public QuorumCert {
+    uint256_t blk_hash;
+    public:
+    QuorumCertDummy() {}
+    QuorumCertDummy(const ReplicaConfig &, const uint256_t &blk_hash):
+        blk_hash(blk_hash) {}
+
+    void serialize(DataStream &s) const override {
+        s << (uint32_t)1 << blk_hash;
+    }
+
+    void unserialize(DataStream &s) override {
+        uint32_t tmp;
+        s >> tmp >> blk_hash;
+    }
+
+    QuorumCert *clone() override {
+        return new QuorumCertDummy(*this);
+    }
+
+    void add_part(ReplicaID, const PartCert &) override {}
+    void compute() override {}
+    bool verify(const ReplicaConfig &) override { return true; }
+
+    const uint256_t &get_blk_hash() const override { return blk_hash; }
+};
+
+
+class Secp256k1Context {
+    secp256k1_context *ctx;
+    friend class PubKeySecp256k1;
+    friend class SigSecp256k1;
+    public:
+    Secp256k1Context(bool sign = false):
+        ctx(secp256k1_context_create(
+            sign ? SECP256K1_CONTEXT_SIGN :
+                    SECP256K1_CONTEXT_VERIFY)) {}
+
+    Secp256k1Context(const Secp256k1Context &) = delete;
+
+    Secp256k1Context(Secp256k1Context &&other): ctx(other.ctx) {
+        other.ctx = nullptr;
+    }
+
+    ~Secp256k1Context() {
+        if (ctx) secp256k1_context_destroy(ctx);
+    }
+};
+
+using secp256k1_context_t = RcObj<Secp256k1Context>;
+
+extern secp256k1_context_t secp256k1_default_sign_ctx;
+extern secp256k1_context_t secp256k1_default_verify_ctx;
+
+class PrivKeySecp256k1;
+
+class PubKeySecp256k1: public PubKey {
+    static const auto _olen = 33;
+    friend class SigSecp256k1;
+    secp256k1_pubkey data;
+    secp256k1_context_t ctx;
+
+    public:
+    PubKeySecp256k1(const secp256k1_context_t &ctx =
+                            secp256k1_default_sign_ctx):
+        PubKey(), ctx(ctx) {}
+    
+    PubKeySecp256k1(const bytearray_t &raw_bytes,
+                    const secp256k1_context_t &ctx =
+                            secp256k1_default_sign_ctx):
+        PubKeySecp256k1(ctx) { from_bytes(raw_bytes); }
+
+    inline PubKeySecp256k1(const PrivKeySecp256k1 &priv_key,
+                            const secp256k1_context_t &ctx =
+                                    secp256k1_default_sign_ctx);
+
+    void serialize(DataStream &s) const override {
+        static uint8_t output[_olen];
+        size_t olen = _olen;
+        (void)secp256k1_ec_pubkey_serialize(
+                ctx->ctx, (unsigned char *)output,
+                &olen, &data, SECP256K1_EC_COMPRESSED);
+        s.put_data(output, output + _olen);
+    }
+
+    void unserialize(DataStream &s) override {
+        static const auto _exc = std::invalid_argument("ill-formed public key");
+        try {
+            if (!secp256k1_ec_pubkey_parse(
+                    ctx->ctx, &data, s.get_data_inplace(_olen), _olen))
+                throw _exc;
+        } catch (std::ios_base::failure &) {
+            throw _exc;
+        }
+    }
+
+    PubKeySecp256k1 *clone() override {
+        return new PubKeySecp256k1(*this);
+    }
+};
+
+class PrivKeySecp256k1: public PrivKey {
+    static const auto nbytes = 32;
+    friend class PubKeySecp256k1;
+    friend class SigSecp256k1;
+    uint8_t data[nbytes];
+    secp256k1_context_t ctx;
+
+    public:
+    PrivKeySecp256k1(const secp256k1_context_t &ctx =
+                            secp256k1_default_sign_ctx):
+        PrivKey(), ctx(ctx) {}
+
+    PrivKeySecp256k1(const bytearray_t &raw_bytes,
+                     const secp256k1_context_t &ctx =
+                            secp256k1_default_sign_ctx):
+        PrivKeySecp256k1(ctx) { from_bytes(raw_bytes); }
+
+    void serialize(DataStream &s) const override {
+        s.put_data(data, data + nbytes);
+    }
+
+    void unserialize(DataStream &s) override {
+        static const auto _exc = std::invalid_argument("ill-formed private key");
+        try {
+            memmove(data, s.get_data_inplace(nbytes), nbytes);
+        } catch (std::ios_base::failure &) {
+            throw _exc;
+        }
+    }
+
+    void from_rand() override {
+        if (!RAND_bytes(data, nbytes))
+            throw std::runtime_error("cannot get rand bytes from openssl");
+    }
+
+    inline pubkey_bt get_pubkey() const override;
+};
+
+pubkey_bt PrivKeySecp256k1::get_pubkey() const {
+    return new PubKeySecp256k1(*this, ctx);
+}
+
+PubKeySecp256k1::PubKeySecp256k1(
+        const PrivKeySecp256k1 &priv_key,
+        const secp256k1_context_t &ctx): PubKey(), ctx(ctx) {
+    if (!secp256k1_ec_pubkey_create(ctx->ctx, &data, priv_key.data))
+        throw std::invalid_argument("invalid secp256k1 private key");
+}
+
+class SigSecp256k1: public Serializable {
+    secp256k1_ecdsa_signature data;
+    secp256k1_context_t ctx;
+
+    void check_msg_length(const bytearray_t &msg) {
+        if (msg.size() != 32)
+            throw std::invalid_argument("the message should be 32-bytes");
+    }
+
+    public:
+    SigSecp256k1(const secp256k1_context_t &ctx =
+                        secp256k1_default_sign_ctx):
+        Serializable(), ctx(ctx) {}
+    SigSecp256k1(const uint256_t &digest,
+                const PrivKeySecp256k1 &priv_key,
+                secp256k1_context_t &ctx =
+                        secp256k1_default_sign_ctx):
+        Serializable(), ctx(ctx) {
+        sign(digest, priv_key);
+    }
+
+    void serialize(DataStream &s) const override {
+        static uint8_t output[64];
+        (void)secp256k1_ecdsa_signature_serialize_compact(
+            ctx->ctx, (unsigned char *)output,
+            &data);
+        s.put_data(output, output + 64);
+    }
+
+    void unserialize(DataStream &s) override {
+        static const auto _exc = std::invalid_argument("ill-formed signature");
+        try {
+            if (!secp256k1_ecdsa_signature_parse_compact(
+                    ctx->ctx, &data, s.get_data_inplace(64)))
+                throw _exc;
+        } catch (std::ios_base::failure &) {
+            throw _exc;
+        }
+    }
+
+    void sign(const bytearray_t &msg, const PrivKeySecp256k1 &priv_key) {
+        check_msg_length(msg);
+        if (!secp256k1_ecdsa_sign(
+                ctx->ctx, &data,
+                (unsigned char *)&*msg.begin(),
+                (unsigned char *)priv_key.data,
+                NULL, // default nonce function
+                NULL))
+            throw std::invalid_argument("failed to create secp256k1 signature");
+    }
+
+    bool verify(const bytearray_t &msg, const PubKeySecp256k1 &pub_key,
+                const secp256k1_context_t &_ctx) {
+        check_msg_length(msg);
+        return secp256k1_ecdsa_verify(
+                _ctx->ctx, &data,
+                (unsigned char *)&*msg.begin(),
+                &pub_key.data) == 1;
+    }
+
+    bool verify(const bytearray_t &msg, const PubKeySecp256k1 &pub_key) {
+        return verify(msg, pub_key, ctx);
+    }
+};
+
+class PartCertSecp256k1: public SigSecp256k1, public PartCert {
+    uint256_t blk_hash;
+
+    public:
+    PartCertSecp256k1() = default;
+    PartCertSecp256k1(const PrivKeySecp256k1 &priv_key, const uint256_t &blk_hash):
+        SigSecp256k1(blk_hash, priv_key),
+        PartCert(),
+        blk_hash(blk_hash) {}
+
+    bool verify(const PubKey &pub_key) override {
+        return SigSecp256k1::verify(blk_hash,
+                                    static_cast<const PubKeySecp256k1 &>(pub_key),
+                                    secp256k1_default_verify_ctx);
+    }
+
+    const uint256_t &get_blk_hash() const override { return blk_hash; }
+
+    PartCertSecp256k1 *clone() override {
+        return new PartCertSecp256k1(*this);
+    }
+
+    void serialize(DataStream &s) const override {
+        s << blk_hash;
+        this->SigSecp256k1::serialize(s);
+    }
+
+    void unserialize(DataStream &s) override {
+        s >> blk_hash;
+        this->SigSecp256k1::unserialize(s);
+    }
+};
+
+class QuorumCertSecp256k1: public QuorumCert {
+    uint256_t blk_hash;
+    salticidae::Bits rids;
+    std::vector<SigSecp256k1> sigs;
+
+    public:
+    QuorumCertSecp256k1() = default;
+    QuorumCertSecp256k1(const ReplicaConfig &config, const uint256_t &blk_hash);
+
+    void add_part(ReplicaID rid, const PartCert &pc) override {
+        if (pc.get_blk_hash() != blk_hash)
+            throw std::invalid_argument("PartCert does match the block hash");
+        if (!rids.get(rid))
+        {
+            rids.set(rid);
+            sigs.push_back(static_cast<const PartCertSecp256k1 &>(pc));
+        }
+    }
+
+    void compute() override {}
+
+    bool verify(const ReplicaConfig &config) override;
+
+    const uint256_t &get_blk_hash() const override { return blk_hash; }
+
+    QuorumCertSecp256k1 *clone() override {
+        return new QuorumCertSecp256k1(*this);
+    }
+
+    void serialize(DataStream &s) const override {
+        s << blk_hash << rids;
+        for (const auto &sig: sigs) s << sig;
+    }
+
+    void unserialize(DataStream &s) override {
+        s >> blk_hash >> rids;
+        sigs.resize(rids.size());
+        for (auto &sig: sigs) s >> sig;
+    }
+};
+
+}
+
+#endif
diff --git a/src/entity.cpp b/src/entity.cpp
new file mode 100644
index 0000000..1294484
--- /dev/null
+++ b/src/entity.cpp
@@ -0,0 +1,35 @@
+#include "entity.h"
+#include "core.h"
+
+namespace hotstuff {
+
+void Block::serialize(DataStream &s) const {
+    s << (uint32_t)parent_hashes.size();
+    for (const auto &hash: parent_hashes)
+        s << hash;
+    s << (uint32_t)cmds.size();
+    for (auto cmd: cmds)
+        s << *cmd;
+    if (qc == nullptr)
+        s << (uint8_t)0;
+    else
+        s << (uint8_t)1 << *qc;
+}
+
+void Block::unserialize(DataStream &s, HotStuffCore *hsc) {
+    uint32_t n;
+    uint8_t has_qc;
+    s >> n;
+    parent_hashes.resize(n);
+    for (auto &hash: parent_hashes)
+        s >> hash;
+    s >> n;
+    cmds.resize(n);
+    for (auto &cmd: cmds)
+        cmd = hsc->parse_cmd(s);
+    s >> has_qc;
+    qc = has_qc ? hsc->parse_quorum_cert(s) : nullptr;
+    this->hash = salticidae::get_hash(*this);
+}
+
+}
diff --git a/src/entity.h b/src/entity.h
new file mode 100644
index 0000000..b3a0df4
--- /dev/null
+++ b/src/entity.h
@@ -0,0 +1,309 @@
+#ifndef _HOTSTUFF_ENT_H
+#define _HOTSTUFF_ENT_H
+
+#include <vector>
+#include <unordered_map>
+#include <unordered_set>
+#include <string>
+#include <cstddef>
+#include <ios>
+
+#include "salticidae/netaddr.h"
+#include "salticidae/ref.h"
+#include "type.h"
+#include "util.h"
+#include "crypto.h"
+
+namespace hotstuff {
+
+enum EntityType {
+    ENT_TYPE_CMD = 0x0,
+    ENT_TYPE_BLK = 0x1
+};
+
+struct ReplicaInfo {
+    ReplicaID id;
+    salticidae::NetAddr addr;
+    pubkey_bt pubkey;
+
+    ReplicaInfo(ReplicaID id,
+                const salticidae::NetAddr &addr,
+                pubkey_bt &&pubkey):
+        id(id), addr(addr), pubkey(std::move(pubkey)) {}
+
+    ReplicaInfo(const ReplicaInfo &other):
+        id(other.id), addr(other.addr),
+        pubkey(other.pubkey->clone()) {}
+
+    ReplicaInfo(ReplicaInfo &&other):
+        id(other.id), addr(other.addr),
+        pubkey(std::move(other.pubkey)) {}
+};
+
+class ReplicaConfig {
+    std::unordered_map<ReplicaID, ReplicaInfo> replica_map;
+
+    public:
+    size_t nmajority;
+
+    void add_replica(ReplicaID rid, const ReplicaInfo &info) {
+        replica_map.insert(std::make_pair(rid, info));
+    }
+
+    const ReplicaInfo &get_info(ReplicaID rid) const {
+        auto it = replica_map.find(rid);
+        if (it == replica_map.end())
+            throw HotStuffError("rid %s not found",
+                    get_hex(rid).c_str());
+        return it->second;
+    }
+
+    const PubKey &get_pubkey(ReplicaID rid) const {
+        return *(get_info(rid).pubkey);
+    }
+
+    const salticidae::NetAddr &get_addr(ReplicaID rid) const {
+        return get_info(rid).addr;
+    }
+};
+
+class Block;
+class HotStuffCore;
+
+using block_t = salticidae::RcObj<Block>;
+using block_weak_t = salticidae::WeakObj<Block>;
+
+struct Finality: public Serializable {
+    int8_t decision;
+    uint256_t blk_hash;
+    
+    public:
+    Finality(): decision(0) {}
+    Finality(int8_t decision, uint256_t blk_hash):
+        decision(decision), blk_hash(blk_hash) {}
+
+    void serialize(DataStream &s) const override {
+        s << decision;
+        if (decision == 1) s << blk_hash;
+    }
+
+    void unserialize(DataStream &s) override {
+        s >> decision;
+        if (decision == 1) s >> blk_hash;
+    }
+};
+
+class Command: public Serializable {
+    friend HotStuffCore;
+    block_weak_t container;
+    public:
+    virtual ~Command() = default;
+    virtual const uint256_t &get_hash() const = 0;
+    virtual bool verify() const = 0;
+    inline int8_t get_decision() const;
+    inline Finality get_finality() const;
+    block_t get_container() const {
+        return container;
+    }
+};
+
+using command_t = RcObj<Command>;
+
+template<typename Hashable>
+inline static std::vector<uint256_t>
+get_hashes(const std::vector<Hashable> &plist) {
+    std::vector<uint256_t> hashes;
+    for (const auto &p: plist)
+        hashes.push_back(p->get_hash());
+    return std::move(hashes);
+}
+
+class Block {
+    friend HotStuffCore;
+    std::vector<uint256_t> parent_hashes;
+    std::vector<command_t> cmds;
+    quorum_cert_bt qc;
+    uint256_t hash;
+
+    std::vector<block_t> parents;
+    block_t qc_ref;
+    quorum_cert_bt self_qc;
+    uint32_t height;
+    bool delivered;
+    int8_t decision;
+
+    std::unordered_set<ReplicaID> voted;
+
+    public:
+    Block():
+        qc(nullptr),
+        qc_ref(nullptr),
+        self_qc(nullptr), height(0),
+        delivered(false), decision(0) {}
+
+    Block(bool delivered, int8_t decision):
+        qc(nullptr),
+        hash(salticidae::get_hash(*this)),
+        qc_ref(nullptr),
+        self_qc(nullptr), height(0),
+        delivered(delivered), decision(decision) {}
+
+    Block(const std::vector<block_t> &parents,
+        const std::vector<command_t> &cmds,
+        uint32_t height,
+        quorum_cert_bt &&qc,
+        const block_t &qc_ref,
+        quorum_cert_bt &&self_qc,
+        int8_t decision = 0):
+            parent_hashes(get_hashes(parents)),
+            cmds(cmds),
+            qc(std::move(qc)),
+            hash(salticidae::get_hash(*this)),
+            parents(parents),
+            qc_ref(qc_ref),
+            self_qc(std::move(self_qc)),
+            height(height),
+            delivered(0),
+            decision(decision) {}
+
+    void serialize(DataStream &s) const;
+
+    void unserialize(DataStream &s, HotStuffCore *hsc);
+
+    const std::vector<command_t> &get_cmds() const {
+        return cmds;
+    }
+
+    const std::vector<block_t> &get_parents() const {
+        return parents;
+    }
+
+    const std::vector<uint256_t> &get_parent_hashes() const {
+        return parent_hashes;
+    }
+
+    const uint256_t &get_hash() const { return hash; }
+
+    bool verify(const ReplicaConfig &config) const {
+        if (qc && !qc->verify(config)) return false;
+        for (auto cmd: cmds)
+            if (!cmd->verify()) return false;
+        return true;
+    }
+
+    int8_t get_decision() const { return decision; }
+
+    bool is_delivered() const { return delivered; }
+
+    uint32_t get_height() const { return height; }
+
+    const quorum_cert_bt &get_qc() const { return qc; }
+
+    operator std::string () const {
+        DataStream s;
+        s << "<block "
+          << "id="  << get_hex10(hash) << " "
+          << "height=" << std::to_string(height) << " "
+          << "parent=" << get_hex10(parent_hashes[0]) << ">";
+        return std::string(std::move(s));
+    }
+};
+
+struct BlockHeightCmp {
+    bool operator()(const block_t &a, const block_t &b) const {
+        return a->get_height() < b->get_height();
+    }
+};
+
+int8_t Command::get_decision() const {
+    block_t cptr = container;
+    return cptr ? cptr->get_decision() : 0;
+}
+
+Finality Command::get_finality() const {
+    block_t blk = get_container();
+    return Finality(get_decision(),
+                    blk ? blk->get_hash() : uint256_t());
+}
+
+class EntityStorage {
+    std::unordered_map<const uint256_t, block_t> blk_cache;
+    std::unordered_map<const uint256_t, command_t> cmd_cache;
+    public:
+    bool is_blk_delivered(const uint256_t &blk_hash) {
+        auto it = blk_cache.find(blk_hash);
+        if (it == blk_cache.end()) return false;
+        return it->second->is_delivered();
+    }
+
+    bool is_blk_fetched(const uint256_t &blk_hash) {
+        return blk_cache.count(blk_hash);
+    }
+
+    const block_t &add_blk(Block &&_blk) {
+        block_t blk = new Block(std::move(_blk));
+        return blk_cache.insert(std::make_pair(blk->get_hash(), blk)).first->second;
+    }
+
+    const block_t &add_blk(const block_t &blk) {
+        return blk_cache.insert(std::make_pair(blk->get_hash(), blk)).first->second;
+    }
+
+    block_t find_blk(const uint256_t &blk_hash) {
+        auto it = blk_cache.find(blk_hash);
+        return it == blk_cache.end() ? nullptr : it->second;
+    }
+
+    bool is_cmd_fetched(const uint256_t &cmd_hash) {
+        return cmd_cache.count(cmd_hash);
+    }
+
+    const command_t &add_cmd(const command_t &cmd) {
+        return cmd_cache.insert(std::make_pair(cmd->get_hash(), cmd)).first->second;
+    }
+
+    command_t find_cmd(const uint256_t &cmd_hash) {
+        auto it = cmd_cache.find(cmd_hash);
+        return it == cmd_cache.end() ? nullptr: it->second;
+    }
+
+    size_t get_cmd_cache_size() {
+        return cmd_cache.size();
+    }
+    size_t get_blk_cache_size() {
+        return blk_cache.size();
+    }
+
+    bool try_release_cmd(const command_t &cmd) {
+        if (cmd.get_cnt() == 2) /* only referred by cmd and the storage */
+        {
+            const auto &cmd_hash = cmd->get_hash();
+            cmd_cache.erase(cmd_hash);
+            return true;
+        }
+        return false;
+    }
+
+    bool try_release_blk(const block_t &blk) {
+        if (blk.get_cnt() == 2) /* only referred by blk and the storage */
+        {
+            const auto &blk_hash = blk->get_hash();
+#ifdef HOTSTUFF_ENABLE_LOG_PROTO
+            HOTSTUFF_LOG_INFO("releasing blk %.10s", get_hex(blk_hash).c_str());
+#endif
+            for (const auto &cmd: blk->get_cmds())
+                try_release_cmd(cmd);
+            blk_cache.erase(blk_hash);
+            return true;
+        }
+#ifdef HOTSTUFF_ENABLE_LOG_PROTO
+        else
+            HOTSTUFF_LOG_INFO("cannot release (%lu)", blk.get_cnt());
+#endif
+        return false;
+    }
+};
+
+}
+
+#endif
diff --git a/src/hotstuff.cpp b/src/hotstuff.cpp
new file mode 100644
index 0000000..b10f103
--- /dev/null
+++ b/src/hotstuff.cpp
@@ -0,0 +1,287 @@
+#include <iostream>
+#include <cstring>
+#include <cassert>
+#include <algorithm>
+#include <random>
+#include <unistd.h>
+#include <signal.h>
+#include <event2/event.h>
+
+#include "salticidae/stream.h"
+#include "salticidae/util.h"
+#include "salticidae/network.h"
+#include "salticidae/msg.h"
+#include "promise.hpp"
+#include "type.h"
+#include "core.h"
+#include "entity.h"
+#include "util.h"
+#include "client.h"
+
+using promise::promise_t;
+using salticidae::NetAddr;
+using salticidae::MsgNetwork;
+using salticidae::ClientNetwork;
+using salticidae::Event;
+using salticidae::ElapsedTime;
+using salticidae::Config;
+using salticidae::_1;
+using salticidae::_2;
+using salticidae::static_pointer_cast;
+using salticidae::get_hash;
+using salticidae::trim_all;
+using salticidae::split;
+
+using hotstuff::HotStuffError;
+using hotstuff::CommandDummy;
+using hotstuff::Finality;
+using hotstuff::command_t;
+using hotstuff::uint256_t;
+using hotstuff::bytearray_t;
+using hotstuff::DataStream;
+using hotstuff::ReplicaID;
+using hotstuff::MsgClient;
+
+using HotStuff = hotstuff::HotStuffSecp256k1;
+
+#define LOG_INFO HOTSTUFF_LOG_INFO
+#define LOG_DEBUG HOTSTUFF_LOG_DEBUG
+#define LOG_WARN HOTSTUFF_LOG_WARN
+#define LOG_ERROR HOTSTUFF_LOG_ERROR
+
+class HotStuffApp;
+
+class HotStuffApp: public HotStuff {
+    double stat_period;
+    /** libevent handle */
+    EventContext eb;
+    /** network messaging between a replica and its client */
+    ClientNetwork<MsgClient> cn;
+    /** timer object to schedule a periodic printing of system statistics */
+    Event ev_stat_timer;
+    /** the binding address for client RPC */
+    NetAddr clisten_addr;
+
+    using conn_client_t = MsgNetwork<MsgClient>::conn_t;
+
+    /** Client  */
+    /** submits a new command */
+    inline void client_request_cmd_handler(const MsgClient &, conn_client_t);
+    /** checks if a cmd is decided */
+    inline void client_check_cmd_handler(const MsgClient &, conn_client_t);
+
+    /** The callback function to print stat */
+    inline void print_stat_cb(evutil_socket_t, short);
+
+    command_t parse_cmd(DataStream &s) override {
+        auto cmd = new CommandDummy();
+        s >> *cmd;
+        return cmd;
+    }
+
+    public:
+    HotStuffApp(uint32_t blk_size,
+                int32_t parent_limit,
+                double stat_period,
+                ReplicaID idx,
+                const bytearray_t &raw_privkey,
+                NetAddr plisten_addr,
+                NetAddr clisten_addr,
+                const EventContext &eb);
+
+    void start();
+};
+
+
+std::pair<std::string, std::string> split_ip_port_cport(const std::string &s) {
+    auto ret = trim_all(split(s, ";"));
+    if (ret.size() != 2)
+        throw std::invalid_argument("invalid cport format");
+    return std::make_pair(ret[0], ret[1]);
+}
+
+void signal_handler(int) {
+    throw HotStuffError("got terminal signal");
+}
+
+BoxObj<HotStuffApp> papp = nullptr;
+
+int main(int argc, char **argv) {
+    Config config("hotstuff.conf");
+
+    ElapsedTime elapsed;
+    elapsed.start();
+
+    signal(SIGTERM, signal_handler);
+    signal(SIGINT, signal_handler);
+
+    auto opt_blk_size = Config::OptValInt::create(1);
+    auto opt_parent_limit = Config::OptValInt::create(-1);
+    auto opt_stat_period = Config::OptValDouble::create(10);
+    auto opt_replicas = Config::OptValStrVec::create();
+    auto opt_idx = Config::OptValInt::create(0);
+    auto opt_client_port = Config::OptValInt::create(-1);
+    auto opt_privkey = Config::OptValStr::create();
+    auto opt_help = Config::OptValFlag::create(false);
+
+    config.add_opt("block-size", opt_blk_size, Config::SET_VAL);
+    config.add_opt("parent-limit", opt_parent_limit, Config::SET_VAL);
+    config.add_opt("stat-period", opt_stat_period, Config::SET_VAL);
+    config.add_opt("replica", opt_replicas, Config::APPEND);
+    config.add_opt("idx", opt_idx, Config::SET_VAL);
+    config.add_opt("cport", opt_client_port, Config::SET_VAL);
+    config.add_opt("privkey", opt_privkey, Config::SET_VAL);
+    config.add_opt("help", opt_help, Config::SWITCH_ON, 'h', "show this help info");
+
+    EventContext eb;
+#ifndef HOTSTUFF_ENABLE_LOG_DEBUG
+    try {
+#endif
+        config.parse(argc, argv);
+        if (opt_help->get())
+        {
+            config.print_help();
+            exit(0);
+        }
+        auto idx = opt_idx->get();
+        auto client_port = opt_client_port->get();
+        std::vector<std::pair<std::string, std::string>> replicas;
+        for (const auto &s: opt_replicas->get())
+        {
+            auto res = trim_all(split(s, ","));
+            if (res.size() != 2)
+                throw HotStuffError("invalid replica info");
+            replicas.push_back(std::make_pair(res[0], res[1]));
+        }
+
+        if (!(0 <= idx && (size_t)idx < replicas.size()))
+            throw HotStuffError("replica idx out of range");
+        std::string binding_addr = replicas[idx].first;
+        if (client_port == -1)
+        {
+            auto p = split_ip_port_cport(binding_addr);
+            size_t idx;
+            try {
+                client_port = stoi(p.second, &idx);
+            } catch (std::invalid_argument &) {
+                throw HotStuffError("client port not specified");
+            }
+        }
+
+        NetAddr plisten_addr{split_ip_port_cport(binding_addr).first};
+
+        papp = new HotStuffApp(opt_blk_size->get(),
+                            opt_parent_limit->get(),
+                            opt_stat_period->get(),
+                            idx,
+                            hotstuff::from_hex(opt_privkey->get()),
+                            plisten_addr,
+                            NetAddr("0.0.0.0", client_port),
+                            eb);
+        for (size_t i = 0; i < replicas.size(); i++)
+        {
+            auto p = split_ip_port_cport(replicas[i].first);
+            papp->add_replica(i, NetAddr(p.first),
+                                hotstuff::from_hex(replicas[i].second));
+        }
+        papp->start();
+#ifndef HOTSTUFF_ENABLE_LOG_DEBUG
+    } catch (std::exception &e) {
+        HOTSTUFF_LOG_INFO("exception: %s", e.what());
+        elapsed.stop(true);
+    }
+#endif
+    return 0;
+}
+
+HotStuffApp::HotStuffApp(uint32_t blk_size,
+                        int32_t parent_limit,
+                        double stat_period,
+                        ReplicaID idx,
+                        const bytearray_t &raw_privkey,
+                        NetAddr plisten_addr,
+                        NetAddr clisten_addr,
+                        const EventContext &eb):
+    HotStuff(blk_size, parent_limit, idx, raw_privkey,
+            plisten_addr, eb),
+    stat_period(stat_period),
+    eb(eb),
+    cn(eb),
+    clisten_addr(clisten_addr) {
+    /* register the handlers for msg from clients */
+    cn.reg_handler(hotstuff::REQ_CMD, std::bind(&HotStuffApp::client_request_cmd_handler, this, _1, _2));
+    cn.reg_handler(hotstuff::CHK_CMD, std::bind(&HotStuffApp::client_check_cmd_handler, this, _1, _2));
+    cn.init(clisten_addr);
+}
+
+void HotStuffApp::client_request_cmd_handler(const MsgClient &msg, conn_client_t conn_) {
+    auto conn = static_pointer_cast<ClientNetwork<MsgClient>::Conn>(conn_);
+    const NetAddr addr = conn->get_addr();
+    command_t cmd = new CommandDummy();
+    std::vector<promise_t> pms;
+    msg.parse_reqcmd(static_cast<CommandDummy &>(*cmd));
+
+    bool flag = true;
+#ifndef HOTSTUFF_DISABLE_TX_VERIFY
+    flag &= cmd->verify();
+#endif
+    if (!flag)
+    {
+        LOG_WARN("invalid client cmd");
+        MsgClient resp;
+        resp.gen_respcmd(cmd->get_hash(), Finality(-1, uint256_t()));
+        cn.send_msg(resp, addr);
+    }
+    else
+    {
+        const uint256_t cmd_hash = cmd->get_hash();
+        add_command(cmd);
+        /** wait for the decision of tx */
+        LOG_DEBUG("processing client cmd %.10s", get_hex(cmd_hash).c_str());
+        async_decide(cmd_hash).then([this, addr](command_t cmd) {
+            MsgClient resp;
+            resp.gen_respcmd(cmd->get_hash(), cmd->get_finality());
+            cn.send_msg(resp, addr);
+        });
+    }
+}
+
+void HotStuffApp::client_check_cmd_handler(const MsgClient &msg, conn_client_t conn_) {
+    auto conn = static_pointer_cast<ClientNetwork<MsgClient>::Conn>(conn_);
+    const NetAddr addr = conn->get_addr();
+    uint256_t cmd_hash;
+    msg.parse_chkcmd(cmd_hash);
+    MsgClient resp;
+    command_t cmd = storage->find_cmd(cmd_hash);
+    Finality fin;
+    if (cmd) fin = cmd->get_finality();
+    resp.gen_respcmd(cmd_hash, fin);
+    cn.send_msg(resp, addr);
+}
+
+
+void HotStuffApp::start() {
+    ev_stat_timer = Event(eb, -1, 0,
+            std::bind(&HotStuffApp::print_stat_cb, this, _1, _2));
+    ev_stat_timer.add_with_timeout(stat_period);
+    LOG_INFO("** starting the system with parameters **");
+    LOG_INFO("blk_size = %lu", blk_size);
+    LOG_INFO("parent_limit = %d", parent_limit);
+    LOG_INFO("conns = %lu", HotStuff::size());
+    LOG_INFO("** starting the event loop...");
+#ifdef HOTSTUFF_DISABLE_TX_VERIFY
+    LOG_INFO("!! verification disabled !!");
+#else
+    LOG_INFO("** verification enabled **");
+#endif
+    HotStuff::start();
+    /* enter the event main loop */
+    eb.dispatch();
+}
+
+
+void HotStuffApp::print_stat_cb(evutil_socket_t, short) {
+    HotStuff::print_stat();
+    HotStuffCore::prune(100);
+    ev_stat_timer.add_with_timeout(stat_period);
+}
diff --git a/src/hotstuff_client.cpp b/src/hotstuff_client.cpp
new file mode 100644
index 0000000..5c04e5f
--- /dev/null
+++ b/src/hotstuff_client.cpp
@@ -0,0 +1,181 @@
+#include <cassert>
+#include "salticidae/type.h"
+#include "salticidae/netaddr.h"
+#include "salticidae/network.h"
+#include "salticidae/util.h"
+#include "util.h"
+#include "type.h"
+#include "client.h"
+
+using salticidae::NetAddr;
+using salticidae::Config;
+using salticidae::ElapsedTime;
+using salticidae::EventContext;
+using salticidae::Event;
+using salticidae::bytearray_t;
+using salticidae::trim_all;
+using salticidae::split;
+
+using hotstuff::uint256_t;
+using hotstuff::MsgClient;
+using hotstuff::CommandDummy;
+using hotstuff::Finality;
+
+size_t max_async_num = 10;
+int max_iter_num = 100;
+
+struct Request {
+    ElapsedTime et;
+    Request() { et.start(); }
+};
+
+std::unordered_map<int, salticidae::RingBuffer> buffers;
+std::unordered_map<const uint256_t, Request> waiting;
+
+int connect(const NetAddr &node) {
+    int fd;
+    if ((fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1)
+        assert(0);
+    struct sockaddr_in sockin;
+    memset(&sockin, 0, sizeof(struct sockaddr_in));
+    sockin.sin_family = AF_INET;
+    sockin.sin_addr.s_addr = node.ip;
+    sockin.sin_port = node.port;
+    if (connect(fd, (struct sockaddr *)&sockin, sizeof(struct sockaddr_in)) == -1)
+        assert(0);
+    HOTSTUFF_LOG_INFO("connected to %s", std::string(node).c_str());
+    return fd;
+}
+
+void write_msg(int fd, const MsgClient &msg) {
+    bytearray_t msg_data = msg.serialize();
+    if (write(fd, msg_data.data(), msg_data.size()) != (ssize_t)msg_data.size())
+        assert(0);
+}
+
+void read_msg(int fd, MsgClient &msg) {
+    static const size_t BUFF_SEG_SIZE = 1024;
+    ssize_t ret;
+    auto &buffer = buffers[fd];
+    bool read_body = false;
+    for (;;)
+    {
+        bytearray_t buff_seg;
+        if (!read_body && buffer.size() >= MsgClient::header_size)
+        {
+            buff_seg = buffer.pop(MsgClient::header_size);
+            msg = MsgClient(buff_seg.data());
+            read_body = true;
+        }
+        if (read_body && buffer.size() >= msg.get_length())
+        {
+            buff_seg = buffer.pop(msg.get_length());
+            msg.set_payload(std::move(buff_seg));
+            return;
+        }
+
+        buff_seg.resize(BUFF_SEG_SIZE);
+        ret = read(fd, buff_seg.data(), BUFF_SEG_SIZE);
+        assert(ret != -1);
+        if (ret > 0)
+        {
+            buff_seg.resize(ret);
+            buffer.push(std::move(buff_seg));
+        }
+    }
+}
+
+void try_send(int fd) {
+    while (waiting.size() < max_async_num && max_iter_num)
+    {
+        auto cmd = CommandDummy::make_cmd();
+        MsgClient msg;
+        msg.gen_reqcmd(*cmd);
+        write_msg(fd, msg);
+        HOTSTUFF_LOG_INFO("send new cmd %.10s",
+                            get_hex(cmd->get_hash()).c_str());
+        waiting.insert(std::make_pair(
+            cmd->get_hash(), Request()));
+        if (max_iter_num > 0)
+            max_iter_num--;
+    }
+}
+
+void on_receive(int fd) {
+    MsgClient msg;
+    uint256_t cmd_hash;
+    Finality fin;
+    read_msg(fd, msg);
+    HOTSTUFF_LOG_DEBUG("got %s", std::string(msg).c_str());
+    if (!msg.verify_checksum())
+        HOTSTUFF_LOG_ERROR("incorrect checksum %08x", msg.get_checksum());
+    msg.parse_respcmd(cmd_hash, fin);
+    HOTSTUFF_LOG_INFO(
+        "fd %d got response for %.10s: <decision=%d, blk=%.10s>",
+        fd, get_hex(cmd_hash).c_str(),
+        fin.decision,
+        get_hex(fin.blk_hash).c_str());
+    auto it = waiting.find(cmd_hash);
+    if (it == waiting.end()) return;
+    waiting.erase(it);
+    try_send(fd);
+}
+
+std::pair<std::string, std::string> split_ip_port_cport(const std::string &s) {
+    auto ret = trim_all(split(s, ";"));
+    return std::make_pair(ret[0], ret[1]);
+}
+
+Event *on_receive_ev;
+
+int main(int argc, char **argv) {
+    Config config("hotstuff.conf");
+    std::vector<NetAddr> peers2;
+    EventContext eb;
+    auto opt_idx = Config::OptValInt::create(-1);
+    auto opt_server_addr = Config::OptValStr::create("127.0.0.1:2234");
+    auto opt_replicas = Config::OptValStrVec::create();
+    auto opt_max_iter_num = Config::OptValInt::create();
+
+    try {
+        config.add_opt("idx", opt_idx, Config::SET_VAL);
+        config.add_opt("server", opt_server_addr, Config::SET_VAL);
+        config.add_opt("replica", opt_replicas, Config::APPEND);
+        config.add_opt("ntx", opt_max_iter_num, Config::SET_VAL);
+        config.parse(argc, argv);
+        auto idx = opt_idx->get();
+        max_iter_num = opt_max_iter_num->get();
+        std::vector<std::pair<std::string, std::string>> replicas;
+        for (const auto &s: opt_replicas->get())
+        {
+            auto res = trim_all(split(s, ","));
+            assert(res.size() == 2);
+            replicas.push_back(std::make_pair(res[0], res[1]));
+        }
+
+        NetAddr server(opt_server_addr->get());
+        if (-1 < idx && (size_t)idx < replicas.size() &&
+            replicas.size() > 0)
+        {
+            for (const auto &p: replicas)
+            {
+                auto _p = split_ip_port_cport(p.first);
+                size_t _;
+                peers2.push_back(NetAddr(NetAddr(_p.first).ip, htons(stoi(_p.second, &_))));
+            }
+            server = peers2[idx];
+        }
+
+        int fd = connect(server);
+        on_receive_ev = new Event{eb, fd, EV_READ, [](int fd, short) {
+            on_receive(fd);
+            on_receive_ev->add();
+        }};
+        on_receive_ev->add();
+        try_send(fd);
+        eb.dispatch();
+    } catch (hotstuff::HotStuffError &e) {
+        HOTSTUFF_LOG_ERROR("exception: %s", std::string(e).c_str());
+    }
+    return 0;
+}
diff --git a/src/hotstuff_keygen.cpp b/src/hotstuff_keygen.cpp
new file mode 100644
index 0000000..7a7e615
--- /dev/null
+++ b/src/hotstuff_keygen.cpp
@@ -0,0 +1,33 @@
+#include <error.h>
+#include "salticidae/util.h"
+#include "crypto.h"
+
+using salticidae::Config;
+using hotstuff::privkey_bt;
+using hotstuff::pubkey_bt;
+
+int main(int argc, char **argv) {
+    Config config("hotstuff.conf");
+    privkey_bt priv_key;
+    auto opt_n = Config::OptValInt::create(1);
+    auto opt_algo = Config::OptValStr::create("secp256k1");
+    config.add_opt("num", opt_n, Config::SET_VAL);
+    config.add_opt("algo", opt_algo, Config::SET_VAL);
+    config.parse(argc, argv);
+    auto &algo = opt_algo->get();
+    if (algo == "secp256k1")
+        priv_key = new hotstuff::PrivKeySecp256k1();
+    else
+        error(1, 0, "algo not supported");
+    int n = opt_n->get();
+    if (n < 1)
+        error(1, 0, "n must be >0");
+    while (n--)
+    {
+        priv_key->from_rand();
+        pubkey_bt pub_key = priv_key->get_pubkey();
+        printf("pub:%s sec:%s\n", get_hex(*pub_key).c_str(),
+                            get_hex(*priv_key).c_str());
+    }
+    return 0;
+}
diff --git a/src/promise.hpp b/src/promise.hpp
new file mode 100644
index 0000000..593d5c1
--- /dev/null
+++ b/src/promise.hpp
@@ -0,0 +1,745 @@
+#ifndef _CPPROMISE_HPP
+#define _CPPROMISE_HPP
+
+/**
+ * MIT License
+ * Copyright (c) 2018 Ted Yin <[email protected]>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <stack>
+#include <vector>
+#include <memory>
+#include <functional>
+#include <type_traits>
+
+#if __cplusplus >= 201703L
+#ifdef __has_include
+#   if __has_include(<any>)
+#       include <any>
+#       ifdef __cpp_lib_any
+#           define _CPPROMISE_STD_ANY
+#       endif
+#   endif
+#endif
+#endif
+
+#ifndef _CPPROMISE_STD_ANY
+#include <boost/any.hpp>
+#endif
+
+/**
+ * Implement type-safe Promise primitives similar to the ones specified by
+ * Javascript Promise/A+.
+ */
+namespace promise {
+#ifdef _CPPROMISE_STD_ANY
+    using pm_any_t = std::any;
+    template<typename T>
+    constexpr auto any_cast = static_cast<T(*)(const std::any&)>(std::any_cast<T>);
+    using bad_any_cast = std::bad_any_cast;
+#else
+#   warning "using boost::any"
+#   pragma message "using boost::any"
+    using pm_any_t = boost::any;
+    template<typename T>
+    constexpr auto any_cast = static_cast<T(*)(const boost::any&)>(boost::any_cast<T>);
+    using bad_any_cast = boost::bad_any_cast;
+#endif
+    using callback_t = std::function<void()>;
+    using values_t = std::vector<pm_any_t>;
+
+    /* match lambdas */
+    template<typename T>
+    struct function_traits:
+        public function_traits<decltype(&T::operator())> {};
+ 
+    template<typename ReturnType>
+    struct function_traits<ReturnType()> {
+        using ret_type = ReturnType;
+        using arg_type = void;
+        using empty_arg = void;
+    };
+   
+    /* match plain functions */
+    template<typename ReturnType, typename ArgType>
+    struct function_traits<ReturnType(ArgType)> {
+        using ret_type = ReturnType;
+        using arg_type = ArgType;
+        using non_empty_arg = void;
+    };
+ 
+    /* match function pointers */
+    template<typename ReturnType, typename... ArgType>
+    struct function_traits<ReturnType(*)(ArgType...)>:
+        public function_traits<ReturnType(ArgType...)> {};
+
+    /* match const member functions */
+    template<typename ClassType, typename ReturnType, typename... ArgType>
+    struct function_traits<ReturnType(ClassType::*)(ArgType...) const>:
+        public function_traits<ReturnType(ArgType...)> {};
+
+    /* match member functions */
+    template<typename ClassType, typename ReturnType, typename... ArgType>
+    struct function_traits<ReturnType(ClassType::*)(ArgType...)>:
+        public function_traits<ReturnType(ArgType...)> {};
+
+    template<typename Func, typename ReturnType>
+    using enable_if_return = typename std::enable_if<
+            std::is_same<typename function_traits<Func>::ret_type,
+                         ReturnType>::value>;
+
+    template<typename Func, typename ReturnType>
+    using disable_if_return = typename std::enable_if<
+            !std::is_same<typename function_traits<Func>::ret_type,
+                         ReturnType>::value>;
+
+    template<typename Func, typename ArgType>
+    using enable_if_arg = typename std::enable_if<
+            std::is_same<typename function_traits<Func>::arg_type,
+                         ArgType>::value>;
+
+    template<typename Func, typename ArgType>
+    using disable_if_arg = typename std::enable_if<
+            !std::is_same<typename function_traits<Func>::arg_type,
+                         ArgType>::value>;
+
+    class Promise;
+    //class promise_t: public std::shared_ptr<Promise> {
+    class promise_t {
+        Promise *pm;
+        size_t *ref_cnt;
+        public:
+        friend Promise;
+        template<typename PList> friend promise_t all(const PList &promise_list);
+        template<typename PList> friend promise_t race(const PList &promise_list);
+
+        inline promise_t();
+        inline ~promise_t();
+        template<typename Func> inline promise_t(Func callback);
+
+        void swap(promise_t &other) {
+            std::swap(pm, other.pm);
+            std::swap(ref_cnt, other.ref_cnt);
+        }
+
+        promise_t &operator=(const promise_t &other) {
+            if (this != &other)
+            {
+                promise_t tmp(other);
+                tmp.swap(*this);
+            }
+            return *this;
+        }
+
+        promise_t &operator=(promise_t &&other) {
+            if (this != &other)
+            {
+                promise_t tmp(std::move(other));
+                tmp.swap(*this);
+            }
+            return *this;
+        }
+
+        promise_t(const promise_t &other):
+            pm(other.pm),
+            ref_cnt(other.ref_cnt) {
+            ++*ref_cnt;
+        }
+
+        promise_t(promise_t &&other):
+            pm(other.pm),
+            ref_cnt(other.ref_cnt) {
+            other.pm = nullptr;
+        }
+
+        Promise *operator->() const {
+            return pm;
+        }
+
+        template<typename T> inline void resolve(T result) const;
+        template<typename T> inline void reject(T reason) const;
+        inline void resolve() const;
+        inline void reject() const;
+
+        template<typename FuncFulfilled>
+        inline promise_t then(FuncFulfilled on_fulfilled) const;
+
+        template<typename FuncFulfilled, typename FuncRejected>
+        inline promise_t then(FuncFulfilled on_fulfilled,
+                            FuncRejected on_rejected) const;
+
+        template<typename FuncRejected>
+        inline promise_t fail(FuncRejected on_rejected) const;
+    };
+
+#define PROMISE_ERR_INVALID_STATE do {throw std::runtime_error("invalid promise state");} while (0)
+#define PROMISE_ERR_MISMATCH_TYPE do {throw std::runtime_error("mismatching promise value types");} while (0)
+    
+    class Promise {
+        template<typename PList> friend promise_t all(const PList &promise_list);
+        template<typename PList> friend promise_t race(const PList &promise_list);
+        std::vector<callback_t> fulfilled_callbacks;
+        std::vector<callback_t> rejected_callbacks;
+#ifdef CPPROMISE_USE_STACK_FREE
+        std::vector<Promise *> fulfilled_pms;
+        std::vector<Promise *> rejected_pms;
+#endif
+        enum class State {
+            Pending,
+#ifdef CPPROMISE_USE_STACK_FREE
+            PreFulfilled,
+            PreRejected,
+#endif
+            Fulfilled,
+            Rejected,
+        } state;
+        pm_any_t result;
+        pm_any_t reason;
+
+        void add_on_fulfilled(callback_t &&cb) {
+            fulfilled_callbacks.push_back(std::move(cb));
+        }
+
+        void add_on_rejected(callback_t &&cb) {
+            rejected_callbacks.push_back(std::move(cb));
+        }
+
+        template<typename Func,
+            typename function_traits<Func>::non_empty_arg * = nullptr>
+        static constexpr auto cps_transform(
+                Func f, const pm_any_t &result, const promise_t &npm) {
+            return [&result, npm, f = std::forward<Func>(f)]() mutable {
+#ifndef CPPROMISE_USE_STACK_FREE
+                f(result)->then(
+                    [npm] (pm_any_t result) {npm->resolve(result);},
+                    [npm] (pm_any_t reason) {npm->reject(reason);});
+#else
+                promise_t rpm{f(result)};
+                rpm->then(
+                    [rpm, npm] (pm_any_t result) {
+                        npm->_resolve(result);
+                    },
+                    [rpm, npm] (pm_any_t reason) {
+                        npm->_reject(reason);
+                    });
+                rpm->_dep_resolve(npm);
+                rpm->_dep_reject(npm);
+#endif
+            };
+        }
+
+        template<typename Func,
+            typename function_traits<Func>::empty_arg * = nullptr>
+        static constexpr auto cps_transform(
+                Func f, const pm_any_t &, const promise_t &npm) {
+            return [npm, f = std::forward<Func>(f)]() mutable {
+#ifndef CPPROMISE_USE_STACK_FREE
+                f()->then(
+                    [npm] (pm_any_t result) {npm->resolve(result);},
+                    [npm] (pm_any_t reason) {npm->reject(reason);});
+#else
+                promise_t rpm{f()};
+                rpm->then(
+                    [rpm, npm] (pm_any_t result) {
+                        npm->_resolve(result);
+                    },
+                    [rpm, npm] (pm_any_t reason) {
+                        npm->_reject(reason);
+                    });
+                rpm->_dep_resolve(npm);
+                rpm->_dep_reject(npm);
+#endif
+            };
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, promise_t>::type * = nullptr>
+        constexpr auto gen_on_fulfilled(Func on_fulfilled, const promise_t &npm) {
+            return cps_transform(std::forward<Func>(on_fulfilled), this->result, npm);
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, promise_t>::type * = nullptr>
+        constexpr auto gen_on_rejected(Func on_rejected, const promise_t &npm) {
+            return cps_transform(std::forward<Func>(on_rejected), this->reason, npm);
+        }
+
+
+        template<typename Func,
+            typename enable_if_return<Func, void>::type * = nullptr,
+            typename function_traits<Func>::non_empty_arg * = nullptr>
+        constexpr auto gen_on_fulfilled(Func on_fulfilled, const promise_t &npm) {
+            return [this, npm,
+                    on_fulfilled = std::forward<Func>(on_fulfilled)]() mutable {
+                on_fulfilled(result);
+                npm->_resolve();
+            };
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, void>::type * = nullptr,
+            typename function_traits<Func>::empty_arg * = nullptr>
+        constexpr auto gen_on_fulfilled(Func on_fulfilled, const promise_t &npm) {
+            return [on_fulfilled = std::forward<Func>(on_fulfilled), npm]() mutable {
+                on_fulfilled();
+                npm->_resolve();
+            };
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, void>::type * = nullptr,
+            typename function_traits<Func>::non_empty_arg * = nullptr>
+        constexpr auto gen_on_rejected(Func on_rejected, const promise_t &npm) {
+            return [this, npm,
+                    on_rejected = std::forward<Func>(on_rejected)]() mutable {
+                on_rejected(reason);
+                npm->_reject();
+            };
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, void>::type * = nullptr,
+            typename function_traits<Func>::empty_arg * = nullptr>
+        constexpr auto gen_on_rejected(Func on_rejected, const promise_t &npm) {
+            return [npm,
+                    on_rejected = std::forward<Func>(on_rejected)]() mutable {
+                on_rejected();
+                npm->_reject();
+            };
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, pm_any_t>::type * = nullptr,
+            typename function_traits<Func>::non_empty_arg * = nullptr>
+        constexpr auto gen_on_fulfilled(Func on_fulfilled, const promise_t &npm) {
+            return [this, npm,
+                    on_fulfilled = std::forward<Func>(on_fulfilled)]() mutable {
+                npm->_resolve(on_fulfilled(result));
+            };
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, pm_any_t>::type * = nullptr,
+            typename function_traits<Func>::empty_arg * = nullptr>
+        constexpr auto gen_on_fulfilled(Func on_fulfilled, const promise_t &npm) {
+            return [npm, on_fulfilled = std::forward<Func>(on_fulfilled)]() mutable {
+                npm->_resolve(on_fulfilled());
+            };
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, pm_any_t>::type * = nullptr,
+            typename function_traits<Func>::non_empty_arg * = nullptr>
+        constexpr auto gen_on_rejected(Func on_rejected, const promise_t &npm) {
+            return [this, npm, on_rejected = std::forward<Func>(on_rejected)]() mutable {
+                npm->_reject(on_rejected(reason));
+            };
+        }
+
+        template<typename Func,
+            typename enable_if_return<Func, pm_any_t>::type * = nullptr,
+            typename function_traits<Func>::empty_arg * = nullptr>
+        constexpr auto gen_on_rejected(Func on_rejected, const promise_t &npm) {
+            return [npm, on_rejected = std::forward<Func>(on_rejected)]() mutable {
+                npm->_reject(on_rejected());
+            };
+        }
+
+#ifdef CPPROMISE_USE_STACK_FREE
+        void _trigger() {
+            std::stack<std::tuple<
+                std::vector<Promise *>::const_iterator,
+                std::vector<Promise *> *,
+                Promise *>> s;
+            auto push_frame = [&s](Promise *pm) {
+                if (pm->state == State::PreFulfilled)
+                {
+                    pm->state = State::Fulfilled;
+                    for (auto &cb: pm->fulfilled_callbacks) cb();
+                    s.push(std::make_tuple(pm->fulfilled_pms.begin(),
+                                          &pm->fulfilled_pms,
+                                          pm));
+                }
+                else if (pm->state == State::PreRejected)
+                {
+                    pm->state = State::Rejected;
+                    for (auto &cb: pm->rejected_callbacks) cb();
+                    s.push(std::make_tuple(pm->rejected_pms.begin(),
+                                          &pm->rejected_pms,
+                                          pm));
+                }
+            };
+            push_frame(this);
+            while (!s.empty())
+            {
+                auto &u = s.top();
+                auto &it = std::get<0>(u);
+                auto vec = std::get<1>(u);
+                auto pm = std::get<2>(u);
+                if (it == vec->end())
+                {
+                    s.pop();
+                    vec->clear();
+                    pm->fulfilled_callbacks.clear();
+                    pm->rejected_callbacks.clear();
+                    continue;
+                }
+                push_frame(*it++);
+            }
+        }
+
+        void trigger_fulfill() {
+            state = State::PreFulfilled;
+            _trigger();
+        }
+
+        void trigger_reject() {
+            state = State::PreRejected;
+            _trigger();
+        }
+
+        void _resolve() {
+            if (state == State::Pending) state = State::PreFulfilled;
+        }
+
+        void _reject() {
+            if (state == State::Pending) state = State::PreRejected;
+        }
+
+        void _dep_resolve(const promise_t &npm) {
+            if (state == State::Pending)
+                fulfilled_pms.push_back(npm.pm);
+            else
+                npm->_trigger();
+        }
+
+        void _dep_reject(const promise_t &npm) {
+            if (state == State::Pending)
+                rejected_pms.push_back(npm.pm);
+            else
+                npm->_trigger();
+        }
+
+        void _resolve(pm_any_t _result) {
+            if (state == State::Pending)
+            {
+                result = _result;
+                state = State::PreFulfilled;
+            }
+        }
+
+        void _reject(pm_any_t _reason) {
+            if (state == State::Pending)
+            {
+                reason = _reason;
+                state = State::PreRejected;
+            }
+        }
+#else
+        void _resolve() { resolve(); }
+        void _reject() { reject(); }
+        void _resolve(pm_any_t result) { resolve(result); }
+        void _reject(pm_any_t reason) { reject(reason); }
+
+        void trigger_fulfill() {
+            state = State::Fulfilled;
+            for (const auto &cb: fulfilled_callbacks) cb();
+            fulfilled_callbacks.clear();
+        }
+
+        void trigger_reject() {
+            state = State::Rejected;
+            for (const auto &cb: rejected_callbacks) cb();
+            rejected_callbacks.clear();
+        }
+#endif
+        public:
+
+        Promise(): state(State::Pending) {}
+        ~Promise() {}
+
+        template<typename FuncFulfilled, typename FuncRejected>
+        promise_t then(FuncFulfilled on_fulfilled,
+                      FuncRejected on_rejected) {
+            switch (state)
+            {
+                case State::Pending:
+                return promise_t([this,
+                                on_fulfilled = std::forward<FuncFulfilled>(on_fulfilled),
+                                on_rejected = std::forward<FuncRejected>(on_rejected)
+                                ](promise_t &npm) {
+                    add_on_fulfilled(gen_on_fulfilled(std::move(on_fulfilled), npm));
+                    add_on_rejected(gen_on_rejected(std::move(on_rejected), npm));
+#ifdef CPPROMISE_USE_STACK_FREE
+                    _dep_resolve(npm);
+                    _dep_reject(npm);
+#endif
+                });
+                case State::Fulfilled:
+                return promise_t([this,
+                                on_fulfilled = std::forward<FuncFulfilled>(on_fulfilled)
+                                ](promise_t &npm) {
+                    gen_on_fulfilled(std::move(on_fulfilled), npm)();
+                });
+                case State::Rejected:
+                return promise_t([this,
+                                on_rejected = std::forward<FuncRejected>(on_rejected)
+                                ](promise_t &npm) {
+                    gen_on_rejected(std::move(on_rejected), npm)();
+                });
+                default: PROMISE_ERR_INVALID_STATE;
+            }
+        }
+
+        template<typename FuncFulfilled>
+        promise_t then(FuncFulfilled &&on_fulfilled) {
+            switch (state)
+            {
+                case State::Pending:
+                return promise_t([this,
+                                on_fulfilled = std::forward<FuncFulfilled>(on_fulfilled)
+                                ](promise_t &npm) {
+                    add_on_fulfilled(gen_on_fulfilled(std::move(on_fulfilled), npm));
+                    add_on_rejected([this, npm]() {npm->_reject(reason);});
+#ifdef CPPROMISE_USE_STACK_FREE
+                    _dep_resolve(npm);
+                    _dep_reject(npm);
+#endif
+                });
+                case State::Fulfilled:
+                return promise_t([this,
+                                on_fulfilled = std::forward<FuncFulfilled>(on_fulfilled)
+                                ](promise_t &npm) {
+                    gen_on_fulfilled(std::move(on_fulfilled), npm)();
+                });
+                case State::Rejected:
+                return promise_t([this](promise_t &npm) {npm->_reject(reason);});
+                default: PROMISE_ERR_INVALID_STATE;
+            }
+        }
+ 
+        template<typename FuncRejected>
+        promise_t fail(FuncRejected &&on_rejected) {
+            switch (state)
+            {
+                case State::Pending:
+                return promise_t([this,
+                                on_rejected = std::forward<FuncRejected>(on_rejected)
+                                ](promise_t &npm) {
+                    callback_t ret;
+                    add_on_rejected(gen_on_rejected(std::move(on_rejected), npm));
+                    add_on_fulfilled([this, npm]() {npm->_resolve(result);});
+#ifdef CPPROMISE_USE_STACK_FREE
+                    _dep_resolve(npm);
+                    _dep_reject(npm);
+#endif
+                });
+                case State::Fulfilled:
+                return promise_t([this](promise_t &npm) {npm->_resolve(result);});
+                case State::Rejected:
+                return promise_t([this,
+                                on_rejected = std::forward<FuncRejected>(on_rejected)
+                                ](promise_t &npm) {
+                    gen_on_rejected(std::move(on_rejected), npm)();
+                });
+                default: PROMISE_ERR_INVALID_STATE;
+            }
+        }
+  
+        void resolve() {
+            if (state == State::Pending) trigger_fulfill();
+        }
+
+        void reject() {
+            if (state == State::Pending) trigger_reject();
+        }
+
+        void resolve(pm_any_t _result) {
+            if (state == State::Pending)
+            {
+                result = _result;
+                trigger_fulfill();
+            }
+        }
+
+        void reject(pm_any_t _reason) {
+            if (state == State::Pending)
+            {
+                reason = _reason;
+                trigger_reject();
+            }
+        }
+    };
+        
+    template<typename PList> promise_t all(const PList &promise_list) {
+        return promise_t([&promise_list] (promise_t &npm) {
+            auto size = std::make_shared<size_t>(promise_list.size());
+            auto results = std::make_shared<values_t>();
+            if (!*size) PROMISE_ERR_MISMATCH_TYPE;
+            results->resize(*size);
+            size_t idx = 0;
+            for (const auto &pm: promise_list) {
+                pm->then(
+                    [results, size, idx, npm](pm_any_t result) {
+                        (*results)[idx] = result;
+                        if (!--(*size))
+                            npm->_resolve(*results);
+                    },
+                    [npm](pm_any_t reason) {npm->_reject(reason);});
+#ifdef CPPROMISE_USE_STACK_FREE
+                pm->_dep_resolve(npm);
+                pm->_dep_reject(npm);
+#endif
+                idx++;
+            }
+        });
+    }
+
+    template<typename PList> promise_t race(const PList &promise_list) {
+        return promise_t([&promise_list] (promise_t &npm) {
+            for (const auto &pm: promise_list) {
+                pm->then([npm](pm_any_t result) {npm->_resolve(result);},
+                        [npm](pm_any_t reason) {npm->_reject(reason);});
+#ifdef CPPROMISE_USE_STACK_FREE
+                pm->_dep_resolve(npm);
+                pm->_dep_reject(npm);
+#endif
+            }
+        });
+    }
+
+    template<typename Func>
+    inline promise_t::promise_t(Func callback):
+            pm(new Promise()),
+        ref_cnt(new size_t(1)) {
+        callback(*this);
+    }
+
+    inline promise_t::promise_t():
+        pm(new Promise()),
+        ref_cnt(new size_t(1)) {}
+
+    inline promise_t::~promise_t() {
+        if (pm)
+        {
+            if (--*ref_cnt) return;
+            delete pm;
+            delete ref_cnt;
+        }
+    }
+
+    template<typename T>
+    inline void promise_t::resolve(T result) const { (*this)->resolve(result); }
+
+    template<typename T>
+    inline void promise_t::reject(T reason) const { (*this)->reject(reason); }
+
+    inline void promise_t::resolve() const { (*this)->resolve(); }
+    inline void promise_t::reject() const { (*this)->reject(); }
+
+    template<typename T>
+    struct callback_types {
+        using arg_type = typename function_traits<T>::arg_type;
+        using ret_type = typename std::conditional<
+            std::is_same<typename function_traits<T>::ret_type, promise_t>::value,
+            promise_t, pm_any_t>::type;
+    };
+
+    template<typename Func,
+        typename disable_if_arg<Func, pm_any_t>::type * = nullptr,
+        typename enable_if_return<Func, void>::type * = nullptr,
+        typename function_traits<Func>::non_empty_arg * = nullptr>
+    constexpr auto gen_any_callback(Func f) {
+        using func_t = callback_types<Func>;
+        return [f = std::forward<Func>(f)](pm_any_t v) mutable {
+            try {
+                f(any_cast<typename func_t::arg_type>(v));
+            } catch (bad_any_cast &e) { PROMISE_ERR_MISMATCH_TYPE; }
+        };
+    }
+
+    template<typename Func,
+        typename enable_if_arg<Func, pm_any_t>::type * = nullptr,
+        typename enable_if_return<Func, void>::type * = nullptr,
+        typename function_traits<Func>::non_empty_arg * = nullptr>
+    constexpr auto gen_any_callback(Func f) {
+        return [f = std::forward<Func>(f)](pm_any_t v) mutable {f(v);};
+    }
+
+    template<typename Func,
+        typename enable_if_return<Func, void>::type * = nullptr,
+        typename function_traits<Func>::empty_arg * = nullptr>
+    constexpr auto gen_any_callback(Func f) { return std::forward<Func>(f); }
+
+    template<typename Func,
+        typename enable_if_arg<Func, pm_any_t>::type * = nullptr,
+        typename disable_if_return<Func, void>::type * = nullptr,
+        typename function_traits<Func>::non_empty_arg * = nullptr>
+    constexpr auto gen_any_callback(Func f) {
+        using func_t = callback_types<Func>;
+        return [f = std::forward<Func>(f)](pm_any_t v) mutable {
+            return typename func_t::ret_type(f(v));
+        };
+    }
+
+    template<typename Func,
+        typename disable_if_arg<Func, pm_any_t>::type * = nullptr,
+        typename disable_if_return<Func, void>::type * = nullptr,
+        typename function_traits<Func>::non_empty_arg * = nullptr>
+    constexpr auto gen_any_callback(Func f) {
+        using func_t = callback_types<Func>;
+        return [f = std::forward<Func>(f)](pm_any_t v) mutable {
+            try {
+                return typename func_t::ret_type(
+                    f(any_cast<typename func_t::arg_type>(v)));
+            } catch (bad_any_cast &e) { PROMISE_ERR_MISMATCH_TYPE; }
+        };
+    }
+
+    template<typename Func,
+        typename disable_if_return<Func, void>::type * = nullptr,
+        typename function_traits<Func>::empty_arg * = nullptr>
+    constexpr auto gen_any_callback(Func f) {
+        using func_t = callback_types<Func>;
+        return [f = std::forward<Func>(f)]() mutable {
+            return typename func_t::ret_type(f());
+        };
+    }
+
+    template<typename FuncFulfilled>
+    inline promise_t promise_t::then(FuncFulfilled on_fulfilled) const {
+        return (*this)->then(gen_any_callback(std::forward<FuncFulfilled>(on_fulfilled)));
+    }
+
+    template<typename FuncFulfilled, typename FuncRejected>
+    inline promise_t promise_t::then(FuncFulfilled on_fulfilled,
+                                    FuncRejected on_rejected) const {
+        return (*this)->then(gen_any_callback(std::forward<FuncFulfilled>(on_fulfilled)),
+                            gen_any_callback(std::forward<FuncRejected>(on_rejected)));
+    }
+
+    template<typename FuncRejected>
+    inline promise_t promise_t::fail(FuncRejected on_rejected) const {
+        return (*this)->fail(gen_any_callback(std::forward<FuncRejected>(on_rejected)));
+    }
+}
+
+#endif
diff --git a/src/type.h b/src/type.h
new file mode 100644
index 0000000..4665979
--- /dev/null
+++ b/src/type.h
@@ -0,0 +1,46 @@
+#ifndef _HOTSTUFF_TYPE_H
+#define _HOTSTUFF_TYPE_H
+
+#include "salticidae/stream.h"
+#include "salticidae/type.h"
+#include "salticidae/util.h"
+
+namespace hotstuff {
+
+using salticidae::uint256_t;
+using salticidae::DataStream;
+using salticidae::htole;
+using salticidae::letoh;
+using salticidae::get_hex;
+using salticidae::from_hex;
+using salticidae::bytearray_t;
+
+inline std::string get_hex10(const uint256_t &x) {
+    return get_hex(x).substr(0, 10);
+}
+
+class HotStuffError: public salticidae::SalticidaeError {
+    public:
+    template<typename... Args>
+    HotStuffError(Args... args): salticidae::SalticidaeError(args...) {}
+};
+
+class HotStuffInvalidEntity: public HotStuffError {
+    public:
+    template<typename... Args>
+    HotStuffInvalidEntity(Args... args): HotStuffError(args...) {}
+};
+
+using salticidae::Serializable;
+
+class Cloneable {
+    public:
+    virtual ~Cloneable() = default;
+    virtual Cloneable *clone() = 0;
+};
+
+using ReplicaID = uint16_t;
+
+}
+
+#endif
diff --git a/src/util.cpp b/src/util.cpp
new file mode 100644
index 0000000..dc509f1
--- /dev/null
+++ b/src/util.cpp
@@ -0,0 +1,7 @@
+#include "util.h"
+
+namespace hotstuff {
+
+Logger logger("hotstuff");
+
+}
diff --git a/src/util.h b/src/util.h
new file mode 100644
index 0000000..42c0135
--- /dev/null
+++ b/src/util.h
@@ -0,0 +1,119 @@
+#ifndef _HOTSTUFF_UTIL_H
+#define _HOTSTUFF_UTIL_H
+
+#include "salticidae/util.h"
+
+namespace hotstuff {
+
+class Logger: public salticidae::Logger {
+    public:
+    using salticidae::Logger::Logger;
+};
+
+extern Logger logger;
+
+#ifdef HOTSTUFF_DEBUG_LOG
+#define HOTSTUFF_NORMAL_LOG
+#define HOTSTUFF_ENABLE_LOG_DEBUG
+#endif
+
+#ifdef HOTSTUFF_NORMAL_LOG
+#define HOTSTUFF_ENABLE_LOG_INFO
+#define HOTSTUFF_ENABLE_LOG_WARN
+#endif
+
+#ifdef HOTSTUFF_ENABLE_LOG_INFO
+#define HOTSTUFF_LOG_INFO(...) hotstuff::logger.info(__VA_ARGS__)
+#else
+#define HOTSTUFF_LOG_INFO(...) ((void)0)
+#endif
+
+#ifdef HOTSTUFF_ENABLE_LOG_DEBUG
+#define HOTSTUFF_LOG_DEBUG(...) hotstuff::logger.debug(__VA_ARGS__)
+#else
+#define HOTSTUFF_LOG_DEBUG(...) ((void)0)
+#endif
+
+#ifdef HOTSTUFF_ENABLE_LOG_WARN
+#define HOTSTUFF_LOG_WARN(...) hotstuff::logger.warning(__VA_ARGS__)
+#else
+#define HOTSTUFF_LOG_WARN(...) ((void)0)
+#endif
+
+#define HOTSTUFF_LOG_ERROR(...) hotstuff::logger.error(__VA_ARGS__)
+
+#ifdef HOTSTUFF_ENABLE_BLK_PROFILE
+class BlockProfiler {
+    enum BlockState {
+        BLK_SEEN,
+        BLK_FETCH,
+        BLK_CC
+    };
+
+    struct BlockProfile {
+        bool is_local;          /* is the block proposed by the replica itself? */
+        BlockState state;
+        double hash_seen_time;  /* the first time to see block hash */
+        double full_fetch_time; /* the first time to get full block content */
+        double cc_time;         /* the time when it receives cc */
+        double commit_time;     /* the time when it commits */
+    };
+
+    std::unordered_map<const uint256, BlockProfile> blocks;
+    ElapsedTime timer;
+
+    public:
+    BlockProfiler() { timer.start(); }
+
+    auto rec_blk(const uint256 &blk_hash, bool is_local) {
+        auto it = blocks.find(blk_hash);
+        assert(it == blocks.end());
+        timer.stop(false);
+        return blocks.insert(std::make_pair(blk_hash,
+            BlockProfile{is_local, BLK_SEEN, timer.elapsed_sec, 0, 0, 0})).first;
+    }
+
+    void get_blk(const uint256 &blk_hash) {
+        auto it = blocks.find(blk_hash);
+        if (it == blocks.end())
+            it = rec_blk(blk_hash, false);
+        BlockProfile &blkp = it->second;
+        assert(blkp.state == BLK_SEEN);
+        timer.stop(false);
+        blkp.full_fetch_time = timer.elapsed_sec;
+        blkp.state = BLK_FETCH;
+    }
+
+    void have_cc(const uint256 &blk_hash) {
+        auto it = blocks.find(blk_hash);
+        assert(it != blocks.end());
+        BlockProfile &blkp = it->second;
+        assert(blkp.state == BLK_FETCH);
+        timer.stop(false);
+        blkp.polling_start_time = timer.elapsed_sec;
+        blkp.state = BLK_CC;
+    }
+
+    const char *decide_blk(const uint256 &blk_hash) {
+        static char buff[1024];
+        auto it = blocks.find(blk_hash);
+        assert(it != blocks.end());
+        BlockProfile &blkp = it->second;
+        assert(blkp.state == BLK_CC);
+        timer.stop(false);
+        blkp.commit_time = timer.elapsed_sec;
+        snprintf(buff, sizeof buff, "(%d,%.4f,%.4f,%.4f,%.4f,%.4f)",
+                blkp.is_local,
+                blkp.hash_seen_time, blkp.full_fetch_time,
+                blkp.polling_start_time, blkp.polling_end_time,
+                blkp.commit_time);
+        blocks.erase(it);
+        return buff;
+    }
+};
+
+#endif
+
+}
+
+#endif