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1 files changed, 78 insertions, 0 deletions

diff --git a/include/hotstuff/liveness.h b/include/hotstuff/liveness.h
new file mode 100644
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+++ b/include/hotstuff/liveness.h
@@ -0,0 +1,78 @@
+#ifndef _HOTSTUFF_LIVENESS_H
+#define _HOTSTUFF_LIVENESS_H
+
+#include "hotstuff/consensus.h"
+
+namespace hotstuff {
+
+/** 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);
+        });
+    }
+};
+
+}
+
+#endif