package core import ( "bytes" "fmt" "io" "github.com/CityOfZion/neo-go/pkg/core/storage" "github.com/CityOfZion/neo-go/pkg/core/transaction" "github.com/CityOfZion/neo-go/pkg/util" ) // UnspentCoins is mapping between transactions and their unspent // coin state. type UnspentCoins map[util.Uint256]*UnspentCoinState func (u UnspentCoins) getAndUpdate(s storage.Store, hash util.Uint256) (*UnspentCoinState, error) { if unspent, ok := u[hash]; ok { return unspent, nil } unspent := &UnspentCoinState{} key := storage.AppendPrefix(storage.STCoin, hash.BytesReverse()) if b, err := s.Get(key); err == nil { if err := unspent.DecodeBinary(bytes.NewReader(b)); err != nil { return nil, fmt.Errorf("failed to decode (UnspentCoinState): %s", err) } } else { unspent = &UnspentCoinState{ states: []CoinState{}, } } u[hash] = unspent return unspent, nil } // UnspentCoinState hold the state of a unspent coin. type UnspentCoinState struct { states []CoinState } // NewUnspentCoinState returns a new unspent coin state with N confirmed states. func NewUnspentCoinState(n int) *UnspentCoinState { u := &UnspentCoinState{ states: make([]CoinState, n), } for i := 0; i < n; i++ { u.states[i] = CoinStateConfirmed } return u } // commit writes all unspent coin states to the given Batch. func (u UnspentCoins) commit(b storage.Batch) error { buf := new(bytes.Buffer) for hash, state := range u { if err := state.EncodeBinary(buf); err != nil { return err } key := storage.AppendPrefix(storage.STCoin, hash.BytesReverse()) b.Put(key, buf.Bytes()) buf.Reset() } return nil } // EncodeBinary encodes UnspentCoinState to the given io.Writer. func (s *UnspentCoinState) EncodeBinary(w io.Writer) error { bw := util.BinWriter{W: w} bw.WriteVarUint(uint64(len(s.states))) for _, state := range s.states { bw.WriteLE(byte(state)) } return bw.Err } // DecodeBinary decodes UnspentCoinState from the given io.Reader. func (s *UnspentCoinState) DecodeBinary(r io.Reader) error { br := util.BinReader{R: r} lenStates := br.ReadVarUint() s.states = make([]CoinState, lenStates) for i := 0; i < int(lenStates); i++ { var state uint8 br.ReadLE(&state) s.states[i] = CoinState(state) } return br.Err } // IsDoubleSpend verifies that the input transactions are not double spent. func IsDoubleSpend(s storage.Store, tx *transaction.Transaction) bool { if len(tx.Inputs) == 0 { return false } for prevHash, inputs := range tx.GroupInputsByPrevHash() { unspent := &UnspentCoinState{} key := storage.AppendPrefix(storage.STCoin, prevHash.BytesReverse()) if b, err := s.Get(key); err == nil { if err := unspent.DecodeBinary(bytes.NewReader(b)); err != nil { return false } if unspent == nil { return true } for _, input := range inputs { if int(input.PrevIndex) >= len(unspent.states) || unspent.states[input.PrevIndex] == CoinStateSpent { return true } } } } return false }