Official Go implementation of the Ethereum protocol
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go-ethereum/accounts/abi/reflect.go

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// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package abi
import (
"errors"
"fmt"
"math/big"
"reflect"
"strings"
)
// ConvertType converts an interface of a runtime type into a interface of the
// given type
// e.g. turn
// var fields []reflect.StructField
// fields = append(fields, reflect.StructField{
// Name: "X",
// Type: reflect.TypeOf(new(big.Int)),
// Tag: reflect.StructTag("json:\"" + "x" + "\""),
// }
// into
// type TupleT struct { X *big.Int }
func ConvertType(in interface{}, proto interface{}) interface{} {
protoType := reflect.TypeOf(proto)
if reflect.TypeOf(in).ConvertibleTo(protoType) {
return reflect.ValueOf(in).Convert(protoType).Interface()
}
// Use set as a last ditch effort
if err := set(reflect.ValueOf(proto), reflect.ValueOf(in)); err != nil {
panic(err)
}
return proto
}
// indirect recursively dereferences the value until it either gets the value
// or finds a big.Int
func indirect(v reflect.Value) reflect.Value {
if v.Kind() == reflect.Ptr && v.Elem().Type() != reflect.TypeOf(big.Int{}) {
return indirect(v.Elem())
}
return v
}
// reflectIntType returns the reflect using the given size and
// unsignedness.
func reflectIntType(unsigned bool, size int) reflect.Type {
if unsigned {
switch size {
case 8:
return reflect.TypeOf(uint8(0))
case 16:
return reflect.TypeOf(uint16(0))
case 32:
return reflect.TypeOf(uint32(0))
case 64:
return reflect.TypeOf(uint64(0))
}
}
switch size {
case 8:
return reflect.TypeOf(int8(0))
case 16:
return reflect.TypeOf(int16(0))
case 32:
return reflect.TypeOf(int32(0))
case 64:
return reflect.TypeOf(int64(0))
}
return reflect.TypeOf(&big.Int{})
}
// mustArrayToByteSlice creates a new byte slice with the exact same size as value
// and copies the bytes in value to the new slice.
func mustArrayToByteSlice(value reflect.Value) reflect.Value {
slice := reflect.MakeSlice(reflect.TypeOf([]byte{}), value.Len(), value.Len())
reflect.Copy(slice, value)
return slice
}
// set attempts to assign src to dst by either setting, copying or otherwise.
//
// set is a bit more lenient when it comes to assignment and doesn't force an as
// strict ruleset as bare `reflect` does.
func set(dst, src reflect.Value) error {
dstType, srcType := dst.Type(), src.Type()
switch {
case dstType.Kind() == reflect.Interface && dst.Elem().IsValid():
return set(dst.Elem(), src)
case dstType.Kind() == reflect.Ptr && dstType.Elem() != reflect.TypeOf(big.Int{}):
return set(dst.Elem(), src)
case srcType.AssignableTo(dstType) && dst.CanSet():
dst.Set(src)
case dstType.Kind() == reflect.Slice && srcType.Kind() == reflect.Slice && dst.CanSet():
return setSlice(dst, src)
case dstType.Kind() == reflect.Array:
return setArray(dst, src)
case dstType.Kind() == reflect.Struct:
return setStruct(dst, src)
default:
return fmt.Errorf("abi: cannot unmarshal %v in to %v", src.Type(), dst.Type())
}
return nil
}
// setSlice attempts to assign src to dst when slices are not assignable by default
// e.g. src: [][]byte -> dst: [][15]byte
// setSlice ignores if we cannot copy all of src' elements.
func setSlice(dst, src reflect.Value) error {
slice := reflect.MakeSlice(dst.Type(), src.Len(), src.Len())
for i := 0; i < src.Len(); i++ {
if err := set(slice.Index(i), src.Index(i)); err != nil {
return err
}
}
if dst.CanSet() {
dst.Set(slice)
return nil
}
return errors.New("Cannot set slice, destination not settable")
}
func setArray(dst, src reflect.Value) error {
if src.Kind() == reflect.Ptr {
return set(dst, indirect(src))
}
array := reflect.New(dst.Type()).Elem()
min := src.Len()
if src.Len() > dst.Len() {
min = dst.Len()
}
for i := 0; i < min; i++ {
if err := set(array.Index(i), src.Index(i)); err != nil {
return err
}
}
if dst.CanSet() {
dst.Set(array)
return nil
}
return errors.New("Cannot set array, destination not settable")
}
func setStruct(dst, src reflect.Value) error {
for i := 0; i < src.NumField(); i++ {
srcField := src.Field(i)
dstField := dst.Field(i)
if !dstField.IsValid() || !srcField.IsValid() {
return fmt.Errorf("Could not find src field: %v value: %v in destination", srcField.Type().Name(), srcField)
}
if err := set(dstField, srcField); err != nil {
return err
}
}
return nil
}
// mapArgNamesToStructFields maps a slice of argument names to struct fields.
// first round: for each Exportable field that contains a `abi:""` tag
// and this field name exists in the given argument name list, pair them together.
// second round: for each argument name that has not been already linked,
// find what variable is expected to be mapped into, if it exists and has not been
// used, pair them.
// Note this function assumes the given value is a struct value.
func mapArgNamesToStructFields(argNames []string, value reflect.Value) (map[string]string, error) {
typ := value.Type()
abi2struct := make(map[string]string)
struct2abi := make(map[string]string)
// first round ~~~
for i := 0; i < typ.NumField(); i++ {
structFieldName := typ.Field(i).Name
// skip private struct fields.
if structFieldName[:1] != strings.ToUpper(structFieldName[:1]) {
continue
}
// skip fields that have no abi:"" tag.
tagName, ok := typ.Field(i).Tag.Lookup("abi")
if !ok {
continue
}
// check if tag is empty.
if tagName == "" {
return nil, fmt.Errorf("struct: abi tag in '%s' is empty", structFieldName)
}
// check which argument field matches with the abi tag.
found := false
for _, arg := range argNames {
if arg == tagName {
if abi2struct[arg] != "" {
return nil, fmt.Errorf("struct: abi tag in '%s' already mapped", structFieldName)
}
// pair them
abi2struct[arg] = structFieldName
struct2abi[structFieldName] = arg
found = true
}
}
// check if this tag has been mapped.
if !found {
return nil, fmt.Errorf("struct: abi tag '%s' defined but not found in abi", tagName)
}
}
// second round ~~~
for _, argName := range argNames {
structFieldName := ToCamelCase(argName)
if structFieldName == "" {
return nil, fmt.Errorf("abi: purely underscored output cannot unpack to struct")
}
// this abi has already been paired, skip it... unless there exists another, yet unassigned
// struct field with the same field name. If so, raise an error:
// abi: [ { "name": "value" } ]
// struct { Value *big.Int , Value1 *big.Int `abi:"value"`}
if abi2struct[argName] != "" {
if abi2struct[argName] != structFieldName &&
struct2abi[structFieldName] == "" &&
value.FieldByName(structFieldName).IsValid() {
return nil, fmt.Errorf("abi: multiple variables maps to the same abi field '%s'", argName)
}
continue
}
// return an error if this struct field has already been paired.
if struct2abi[structFieldName] != "" {
return nil, fmt.Errorf("abi: multiple outputs mapping to the same struct field '%s'", structFieldName)
}
if value.FieldByName(structFieldName).IsValid() {
// pair them
abi2struct[argName] = structFieldName
struct2abi[structFieldName] = argName
} else {
// not paired, but annotate as used, to detect cases like
// abi : [ { "name": "value" }, { "name": "_value" } ]
// struct { Value *big.Int }
struct2abi[structFieldName] = argName
}
}
return abi2struct, nil
}