package block import ( "encoding/json" "errors" "github.com/nspcc-dev/neo-go/pkg/core/transaction" "github.com/nspcc-dev/neo-go/pkg/crypto/hash" "github.com/nspcc-dev/neo-go/pkg/encoding/address" "github.com/nspcc-dev/neo-go/pkg/io" "github.com/nspcc-dev/neo-go/pkg/util" ) // Header holds the base info of a block. type Header struct { // Version of the block. Version uint32 // hash of the previous block. PrevHash util.Uint256 // Root hash of a transaction list. MerkleRoot util.Uint256 // Timestamp is a millisecond-precision timestamp. // The time stamp of each block must be later than previous block's time stamp. // Generally the difference of two block's time stamp is about 15 seconds and imprecision is allowed. // The height of the block must be exactly equal to the height of the previous block plus 1. Timestamp uint64 // index/height of the block Index uint32 // Contract address of the next miner NextConsensus util.Uint160 // Script used to validate the block Script transaction.Witness // StateRootEnabled specifies if header contains state root. StateRootEnabled bool // PrevStateRoot is state root of the previous block. PrevStateRoot util.Uint256 // PrimaryIndex is the index of primary consensus node for this block. PrimaryIndex byte // Hash of this block, created when binary encoded (double SHA256). hash util.Uint256 } // baseAux is used to marshal/unmarshal to/from JSON, it's almost the same // as original Base, but with Nonce and NextConsensus fields differing and // Hash added. type baseAux struct { Hash util.Uint256 `json:"hash"` Version uint32 `json:"version"` PrevHash util.Uint256 `json:"previousblockhash"` MerkleRoot util.Uint256 `json:"merkleroot"` Timestamp uint64 `json:"time"` Index uint32 `json:"index"` NextConsensus string `json:"nextconsensus"` PrimaryIndex byte `json:"primary"` PrevStateRoot *util.Uint256 `json:"previousstateroot,omitempty"` Witnesses []transaction.Witness `json:"witnesses"` } // Hash returns the hash of the block. func (b *Header) Hash() util.Uint256 { if b.hash.Equals(util.Uint256{}) { b.createHash() } return b.hash } // DecodeBinary implements Serializable interface. func (b *Header) DecodeBinary(br *io.BinReader) { b.decodeHashableFields(br) witnessCount := br.ReadVarUint() if br.Err == nil && witnessCount != 1 { br.Err = errors.New("wrong witness count") return } b.Script.DecodeBinary(br) } // EncodeBinary implements Serializable interface. func (b *Header) EncodeBinary(bw *io.BinWriter) { b.encodeHashableFields(bw) bw.WriteVarUint(1) b.Script.EncodeBinary(bw) } // createHash creates the hash of the block. // When calculating the hash value of the block, instead of calculating the entire block, // only first seven fields in the block head will be calculated, which are // version, PrevBlock, MerkleRoot, timestamp, and height, the nonce, NextMiner. // Since MerkleRoot already contains the hash value of all transactions, // the modification of transaction will influence the hash value of the block. func (b *Header) createHash() { buf := io.NewBufBinWriter() // No error can occur while encoding hashable fields. b.encodeHashableFields(buf.BinWriter) b.hash = hash.Sha256(buf.Bytes()) } // encodeHashableFields will only encode the fields used for hashing. // see Hash() for more information about the fields. func (b *Header) encodeHashableFields(bw *io.BinWriter) { bw.WriteU32LE(b.Version) bw.WriteBytes(b.PrevHash[:]) bw.WriteBytes(b.MerkleRoot[:]) bw.WriteU64LE(b.Timestamp) bw.WriteU32LE(b.Index) bw.WriteB(b.PrimaryIndex) bw.WriteBytes(b.NextConsensus[:]) if b.StateRootEnabled { bw.WriteBytes(b.PrevStateRoot[:]) } } // decodeHashableFields decodes the fields used for hashing. // see Hash() for more information about the fields. func (b *Header) decodeHashableFields(br *io.BinReader) { b.Version = br.ReadU32LE() br.ReadBytes(b.PrevHash[:]) br.ReadBytes(b.MerkleRoot[:]) b.Timestamp = br.ReadU64LE() b.Index = br.ReadU32LE() b.PrimaryIndex = br.ReadB() br.ReadBytes(b.NextConsensus[:]) if b.StateRootEnabled { br.ReadBytes(b.PrevStateRoot[:]) } // Make the hash of the block here so we dont need to do this // again. if br.Err == nil { b.createHash() } } // MarshalJSON implements json.Marshaler interface. func (b Header) MarshalJSON() ([]byte, error) { aux := baseAux{ Hash: b.Hash(), Version: b.Version, PrevHash: b.PrevHash, MerkleRoot: b.MerkleRoot, Timestamp: b.Timestamp, Index: b.Index, PrimaryIndex: b.PrimaryIndex, NextConsensus: address.Uint160ToString(b.NextConsensus), Witnesses: []transaction.Witness{b.Script}, } if b.StateRootEnabled { aux.PrevStateRoot = &b.PrevStateRoot } return json.Marshal(aux) } // UnmarshalJSON implements json.Unmarshaler interface. func (b *Header) UnmarshalJSON(data []byte) error { var aux = new(baseAux) var nextC util.Uint160 err := json.Unmarshal(data, aux) if err != nil { return err } nextC, err = address.StringToUint160(aux.NextConsensus) if err != nil { return err } if len(aux.Witnesses) != 1 { return errors.New("wrong number of witnesses") } b.Version = aux.Version b.PrevHash = aux.PrevHash b.MerkleRoot = aux.MerkleRoot b.Timestamp = aux.Timestamp b.Index = aux.Index b.PrimaryIndex = aux.PrimaryIndex b.NextConsensus = nextC b.Script = aux.Witnesses[0] if b.StateRootEnabled { if aux.PrevStateRoot == nil { return errors.New("'previousstateroot' is empty") } b.PrevStateRoot = *aux.PrevStateRoot } if !aux.Hash.Equals(b.Hash()) { return errors.New("json 'hash' doesn't match block hash") } return nil }