code: func (self *stateObject) SetState(db Database, key, value common.Hash) {
  	// If the new value is the same as old, don't set
  	prev := self.GetState(db, key)
  	if prev == value {
  		return
  	}
  	// New value is different, update and journal the change
  	self.db.journal.append(storageChange{
  		account:  &self.address,
  		key:      key,
  		prevalue: prev,
  	})
  	self.setState(key, value)
  }
docs: // SetState updates a value in account storage.