eth, internal/web3ext: implement storageAt

StorageAt is currently limited and requires needless iterations due to
the limitation of the trie iterator. At present we can't start
iterating from any given key, thus we need to loop over any key
that's not inclusive in the range of start and end.

eth/api.go

@@ -547,3 +547,87 @@ func (api *PrivateDebugAPI) TraceTransaction(ctx context.Context, txHash common.
 	}
 	return nil, errors.New("database inconsistency")
 }
+
+type StorageRangeAtResult struct {
+	Storage  map[string]string `json:"storage"`
+	Complete bool              `json:"complete"`
+}
+
+// StorageRangeAt returns the storage at the given block height and
+// transaction index (exclusive). It may be limited using the
+// storageAddress, storageAddressEnd (inclusive) and maxResult parameters.
+//
+// StorageRangeAt is currently limited and requires needless iterators
+// due to the limitation of the trie iterator. At present we can't start
+// iterating from any given key, thus we need to loop over any key that's
+// not inclusive in the range of start and end.
+//
+// BUG: Because the state objects make use of the secure storage, iterating
+// trie keys is out of order and will be returned the exact same way.
+func (api *PrivateDebugAPI) StorageRangeAt(ctx context.Context, blockHash common.Hash, txIndex int, contractAddress common.Address, storageAddressStart, storageAddressEnd common.Hash, maxResult int) (interface{}, error) {
+	block := api.eth.BlockChain().GetBlockByHash(blockHash)
+	if block == nil {
+		return nil, fmt.Errorf("block %x not found", blockHash)
+	}
+	// Create the state database to mutate and eventually trace
+	parent := api.eth.BlockChain().GetBlock(block.ParentHash(), block.NumberU64()-1)
+	if parent == nil {
+		return nil, fmt.Errorf("block parent %x not found", block.ParentHash())
+	}
+	stateDb, err := api.eth.BlockChain().StateAt(parent.Root())
+	if err != nil {
+		return nil, err
+	}
+
+	result := StorageRangeAtResult{Storage: make(map[string]string)}
+
+	signer := types.MakeSigner(api.config, block.Number())
+	// Mutate the state and trace the selected transaction
+done:
+	for idx, tx := range block.Transactions() {
+		// Assemble the transaction call message
+		msg, err := tx.AsMessage(signer)
+		if err != nil {
+			return nil, fmt.Errorf("sender retrieval failed: %v", err)
+		}
+		context := core.NewEVMContext(msg, block.Header(), api.eth.BlockChain())
+
+		// Mutate the state if we haven't reached the tracing transaction yet
+		if idx < txIndex {
+			vmenv := vm.NewEnvironment(context, stateDb, api.config, vm.Config{})
+			_, _, err := core.ApplyMessage(vmenv, msg, new(core.GasPool).AddGas(tx.Gas()))
+			if err != nil {
+				return nil, fmt.Errorf("mutation failed: %v", err)
+			}
+			stateDb.DeleteSuicides()
+			continue
+		}
+
+		stateObject := stateDb.GetStateObject(contractAddress)
+		// We need to check if the object exists again. It might have been deleted in between the
+		// transactions.
+		if stateObject != nil {
+			trie := stateObject.GetTrie(api.eth.ChainDb())
+			it := trie.Iterator()
+
+			for it.Next() && len(result.Storage) < maxResult {
+				var (
+					value common.Hash
+					key   = trie.GetKey(it.Key)
+				)
+
+				if bytes.Compare(storageAddressStart[:], key[:]) > 0 {
+					continue
+				}
+				if bytes.Compare(storageAddressEnd[:], key[:]) < 0 {
+					break done
+				}
+
+				rlp.DecodeBytes(it.Value, &value)
+				result.Storage[common.ToHex(key)] = value.Hex()
+			}
+			result.Complete = !it.Next()
+		}
+	}
+	return result, nil
+}

internal/web3ext/web3ext.go

@@ -385,6 +385,11 @@ web3._extend({
 			call: 'debug_traceTransaction',
 			params: 2,
 			inputFormatter: [null, null]
+		}),
+		new web3._extend.Method({
+			name: 'storageRangeAt',
+			call: 'debug_storageRangeAt',
+			params: 6,
 		})
 	],
 	properties: []