mipsevm: state cache

mipsevm/state_oracle.go

+package main
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+type StateOracle interface {
+	Get(key [32]byte) (a, b [32]byte)
+	Remember(a, b [32]byte) [32]byte
+}
+
+type StateCache struct {
+	data    map[[32]byte][2][32]byte
+	reverse map[[2][32]byte][32]byte
+}
+
+func NewStateCache() *StateCache {
+	return &StateCache{
+		data:    make(map[[32]byte][2][32]byte),
+		reverse: make(map[[2][32]byte][32]byte),
+	}
+}
+
+func (s *StateCache) Get(key [32]byte) (a, b [32]byte) {
+	ab, ok := s.data[key]
+	if !ok {
+		panic(fmt.Errorf("missing key %x", key))
+	}
+	return ab[0], ab[1]
+}
+
+func (s *StateCache) Remember(left [32]byte, right [32]byte) [32]byte {
+	value := [2][32]byte{left, right}
+	if key, ok := s.reverse[value]; ok {
+		return key
+	}
+	key := crypto.Keccak256Hash(left[:], right[:])
+	s.data[key] = value
+	s.reverse[value] = key
+	return key
+}