core: retrieve contract hash by ID

We'll need this ability further to retrieve contracts hashes for Nep5Balances.

pkg/core/blockchain.go

@@ -982,6 +982,11 @@ func (bc *Blockchain) GetContractState(hash util.Uint160) *state.Contract {
 	return contract
 }
 
+// GetContractScriptHash returns contract script hash by its ID.
+func (bc *Blockchain) GetContractScriptHash(id int32) (util.Uint160, error) {
+	return bc.dao.GetContractScriptHash(id)
+}
+
 // GetAccountState returns the account state from its script hash.
 func (bc *Blockchain) GetAccountState(scriptHash util.Uint160) *state.Account {
 	as, err := bc.dao.GetAccountState(scriptHash)

pkg/core/blockchainer/blockchainer.go

@@ -26,6 +26,7 @@ type Blockchainer interface {
 	HeaderHeight() uint32
 	GetBlock(hash util.Uint256) (*block.Block, error)
 	GetContractState(hash util.Uint160) *state.Contract
+	GetContractScriptHash(id int32) (util.Uint160, error)
 	GetEnrollments() ([]state.Validator, error)
 	GetGoverningTokenBalance(acc util.Uint160) (*big.Int, uint32)
 	GetHeaderHash(int) util.Uint256

pkg/core/dao/dao.go

@@ -27,6 +27,7 @@ type DAO interface {
 	GetBatch() *storage.MemBatch
 	GetBlock(hash util.Uint256) (*block.Block, error)
 	GetContractState(hash util.Uint160) (*state.Contract, error)
+	GetContractScriptHash(id int32) (util.Uint160, error)
 	GetCurrentBlockHeight() (uint32, error)
 	GetCurrentHeaderHeight() (i uint32, h util.Uint256, err error)
 	GetHeaderHashes() ([]util.Uint256, error)
@@ -163,7 +164,10 @@ func (dao *Simple) GetContractState(hash util.Uint160) (*state.Contract, error)
 // PutContractState puts given contract state into the given store.
 func (dao *Simple) PutContractState(cs *state.Contract) error {
 	key := storage.AppendPrefix(storage.STContract, cs.ScriptHash().BytesBE())
-	return dao.Put(cs, key)
+	if err := dao.Put(cs, key); err != nil {
+		return err
+	}
+	return dao.putContractScriptHash(cs)
 }
 
 // DeleteContractState deletes given contract state in the given store.
@@ -187,6 +191,29 @@ func (dao *Simple) GetAndUpdateNextContractID() (int32, error) {
 	return id, dao.Store.Put(key, data)
 }
 
+// putContractScriptHash puts given contract script hash into the given store.
+// It's a private method because it should be used after PutContractState to keep
+// ID-Hash pair always up-to-date.
+func (dao *Simple) putContractScriptHash(cs *state.Contract) error {
+	key := make([]byte, 5)
+	key[0] = byte(storage.STContractID)
+	binary.LittleEndian.PutUint32(key[1:], uint32(cs.ID))
+	return dao.Store.Put(key, cs.ScriptHash().BytesBE())
+}
+
+// GetContractScriptHash returns script hash of the contract with the specified ID.
+// Contract with the script hash may be destroyed.
+func (dao *Simple) GetContractScriptHash(id int32) (util.Uint160, error) {
+	key := make([]byte, 5)
+	key[0] = byte(storage.STContractID)
+	binary.LittleEndian.PutUint32(key[1:], uint32(id))
+	data := &util.Uint160{}
+	if err := dao.GetAndDecode(data, key); err != nil {
+		return *data, err
+	}
+	return *data, nil
+}
+
 // -- end contracts.
 
 // -- start nep5 balances.

pkg/core/storage/store.go

@@ -12,6 +12,7 @@ const (
 	STAccount        KeyPrefix = 0x40
 	STNotification   KeyPrefix = 0x4d
 	STContract       KeyPrefix = 0x50
+	STContractID     KeyPrefix = 0x51
 	STStorage        KeyPrefix = 0x70
 	STNEP5Transfers  KeyPrefix = 0x72
 	STNEP5Balances   KeyPrefix = 0x73

pkg/network/helper_test.go

@@ -67,6 +67,9 @@ func (chain testChain) GetBlock(hash util.Uint256) (*block.Block, error) {
 func (chain testChain) GetContractState(hash util.Uint160) *state.Contract {
 	panic("TODO")
 }
+func (chain testChain) GetContractScriptHash(id int32) (util.Uint160, error) {
+	panic("TODO")
+}
 func (chain testChain) GetHeaderHash(int) util.Uint256 {
 	return util.Uint256{}
 }