init

sim/hash.go

@@ -0,0 +1,56 @@
+package sim
+
+import (
+	"crypto/sha256"
+	"encoding/binary"
+	"sort"
+)
+
+// Hash returns a digest of the complete simulation state. Two runs from the
+// same seed and inputs must produce identical hashes.
+func (s *State) Hash() [32]byte {
+	h := sha256.New()
+	w := func(vs ...int64) {
+		var b [8]byte
+		for _, v := range vs {
+			binary.LittleEndian.PutUint64(b[:], uint64(v))
+			h.Write(b[:])
+		}
+	}
+	w(s.Day, int64(len(s.Asteroids)))
+	for i := range s.Asteroids {
+		a := &s.Asteroids[i]
+		w(a.ID)
+		for _, o := range a.Ore {
+			w(o)
+		}
+	}
+	w(int64(len(s.Ships)))
+	for _, sh := range s.Ships {
+		alive := int64(0)
+		if sh.Alive {
+			alive = 1
+		}
+		w(sh.ID, sh.Owner, alive, int64(sh.Pos.X), int64(sh.Pos.Y), int64(sh.Pos.Z),
+			int64(sh.Vel.X), int64(sh.Vel.Y), int64(sh.Vel.Z),
+			int64(sh.Fuel), sh.Earned, int64(sh.Throttle), int64(sh.Azimuth), int64(sh.Pitch), sh.Target)
+		for _, c := range sh.Cargo {
+			w(c)
+		}
+		h.Write(sh.CPU.MarshalState())
+	}
+	owners := make([]int64, 0, len(s.Credits))
+	for o := range s.Credits {
+		owners = append(owners, o)
+	}
+	sort.Slice(owners, func(i, j int) bool { return owners[i] < owners[j] })
+	for _, o := range owners {
+		w(o, s.Credits[o])
+	}
+	for _, v := range s.Market.Supply {
+		w(v)
+	}
+	var out [32]byte
+	copy(out[:], h.Sum(nil))
+	return out
+}