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Improve result/event unpack (#2348)
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@cgrigis
cgrigis authored Aug 18, 2020
1 parent d5a62b5 commit 6e09132
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Showing 9 changed files with 270 additions and 195 deletions.
131 changes: 19 additions & 112 deletions bevm/api.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -87,96 +87,19 @@ func (contractInstance EvmContractInstance) getAbi() abi.ABI {
}

func unpackResult(contractAbi abi.ABI, methodName string,
resultBytes []byte) (interface{}, error) {
resultBytes []byte) ([]interface{}, error) {
methodAbi, ok := contractAbi.Methods[methodName]
if !ok {
return nil, xerrors.Errorf("method \"%s\" does not exist for "+
"this contract", methodName)
}

return unpackData(contractAbi, methodName, resultBytes, methodAbi.Outputs)
}

func unpackData(contractAbi abi.ABI, objectName string,
dataBytes []byte, args abi.Arguments) (interface{}, error) {

switch len(args) {
case 0:
return nil, nil

case 1:
// Create a pointer to the desired type
result := reflect.New(args[0].Type.Type)

err := contractAbi.Unpack(result.Interface(),
objectName, dataBytes)
if err != nil {
return nil, xerrors.Errorf("failed to unpack single "+
"element of EVM data: %v", err)
}

// Dereference the result pointer
return result.Elem().Interface(), nil

default:
// Abi.Unpack() on multiple values supports a struct or array/slice as
// structure into which the result is stored. Struct is cleaner, but it
// does not support unnamed outputs ("or purely underscored"). If this
// is needed, an array implementation, commented out, follows.

// Build a struct naming the fields after the outputs
var fields []reflect.StructField
for _, output := range args {
// Adapt names to what Abi.Unpack() does
name := abi.ToCamelCase(output.Name)

fields = append(fields, reflect.StructField{
Name: name,
Type: output.Type.Type,
})
}

structType := reflect.StructOf(fields)
s := reflect.New(structType)

err := contractAbi.Unpack(s.Interface(),
objectName, dataBytes)
if err != nil {
return nil, xerrors.Errorf("failed to unpack multiple "+
"elements of EVM data: %v", err)
}

// Dereference the result pointer
return s.Elem().Interface(), nil

// // Build an array of interface{}
// var empty interface{}
// arrType := reflect.ArrayOf(len(abiOutputs),
// reflect.ValueOf(&empty).Type().Elem())
// result := reflect.New(arrType)

// // Create a value of the desired type for each output
// for i, output := range abiOutputs {
// val := reflect.New(output.Type.Type)
// result.Elem().Index(i).Set(val)
// }

// err := contractInstance.Parent.Abi.Unpack(result.Interface(),
// method, resultBytes)
// if err != nil {
// return nil, xerrors.Errorf("unpacking multiple result: %v", err)
// }

// for i := range abiOutputs {
// val := result.Elem().Index(i)
// // Need to dereference values twice:
// // val is interface{}, *val is *type, **val is type
// val.Set(val.Elem().Elem())
// }

// // Dereference the result pointer
// return result.Elem().Interface(), nil
result, err := methodAbi.Outputs.UnpackValues(resultBytes)
if err != nil {
return nil, xerrors.Errorf("failed to unpack result data: %v", err)
}

return result, nil
}

// ---------------------------------------------------------------------------
Expand Down Expand Up @@ -343,7 +266,7 @@ func (client *Client) Transaction(gasLimit uint64, gasPrice uint64,
// on the EVM
func (client *Client) Call(account *EvmAccount,
contractInstance *EvmContractInstance,
method string, args ...interface{}) (interface{}, error) {
method string, args ...interface{}) ([]interface{}, error) {
log.Lvlf2(">>> EVM view method '%s()' on %s", method, contractInstance)
defer log.Lvlf2("<<< EVM view method '%s()' on %s",
method, contractInstance)
Expand Down Expand Up @@ -611,43 +534,27 @@ func decodeEvmArray(abiType string, abi abi.Argument, arg interface{}) (
// EncodeEvmReturnValue encodes the return value of an EVM call to JSON.
// This can be useful for command-line tools or calls serialized over the
// network.
func EncodeEvmReturnValue(returnValue interface{},
func EncodeEvmReturnValue(returnValue []interface{},
outputs abi.Arguments) (string, error) {
var jsonReturnValue []byte
var err error

if len(outputs) == 1 {
abiType := outputs[0].Type.String()
encodedReturnValue, err := encodeEvmValue(abiType, returnValue)
if len(returnValue) != len(outputs) {
return "", xerrors.Errorf("received slice of length %v, expected "+
"to be of length %v", len(returnValue), len(outputs))
}

encodedReturnValue := make([]interface{}, len(outputs))
for i, output := range outputs {
abiType := output.Type.String()
encodedReturnValue[i], err = encodeEvmValue(abiType,
returnValue[i])
if err != nil {
return "", xerrors.Errorf("failed to encode EVM value: %v", err)
}

jsonReturnValue, err = json.Marshal(encodedReturnValue)
} else {
returnValueSlice, ok := returnValue.([]interface{})
if !ok {
return "", xerrors.Errorf("received return value of type: %v, "+
"expected to be a slice", reflect.TypeOf(returnValue))
}
if len(returnValueSlice) != len(outputs) {
return "", xerrors.Errorf("received slice of length %v, expected "+
"to be of length %v", len(returnValueSlice), len(outputs))
}

encodedReturnValue := make([]interface{}, len(outputs))
for i, output := range outputs {
abiType := output.Type.String()
encodedReturnValue[i], err = encodeEvmValue(abiType,
returnValueSlice[i])
if err != nil {
return "", xerrors.Errorf("failed to encode EVM value: %v", err)
}
}

jsonReturnValue, err = json.Marshal(encodedReturnValue)
}

jsonReturnValue, err = json.Marshal(encodedReturnValue)
if err != nil {
return "", xerrors.Errorf("failed to encode return value to JSON: %v",
err)
Expand Down
11 changes: 8 additions & 3 deletions bevm/attr.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -158,11 +158,16 @@ func MakeBevmAttr(rst byzcoin.ReadOnlyStateTrie,
"method result: %v (is the contract address valid?)", err)
}

errorMsg, ok := result.(string)
if len(result) != 1 {
return xerrors.Errorf("EVM validation view method returned %v "+
"values, expected 1", len(result))
}

errorMsg, ok := result[0].(string)
if !ok {
return xerrors.Errorf("EVM validation view method did not return "+
"expected type: %+v (%+v)", result,
reflect.TypeOf(result))
"expected type: %+v (%+v)", result[0],
reflect.TypeOf(result[0]))
}

if errorMsg != "" {
Expand Down
4 changes: 2 additions & 2 deletions bevm/bevmclient/test.sh
View file
Original file line number Diff line number Diff line change
Expand Up @@ -122,7 +122,7 @@ testBevmInteraction(){
'"100"'

# Check Candy balance
testGrep '"100"' runBevmClient call \
testGrep '["100"]' runBevmClient call \
--sign "${BEVM_USER}" \
getRemainingCandies

Expand All @@ -133,7 +133,7 @@ testBevmInteraction(){
'"58"'

# Check Candy balance
testGrep '"42"' runBevmClient call \
testGrep '["42"]' runBevmClient call \
--sign "${BEVM_USER}" \
getRemainingCandies

Expand Down
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