path: root/accounts/abi/reflect.go

// 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 (
    "fmt"
    "reflect"
    "strings"
)

// 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() != derefbigT {
        return indirect(v.Elem())
    }
    return v
}

// reflectIntKind returns the reflect using the given size and
// unsignedness.
func reflectIntKindAndType(unsigned bool, size int) (reflect.Kind, reflect.Type) {
    switch size {
    case 8:
        if unsigned {
            return reflect.Uint8, uint8T
        }
        return reflect.Int8, int8T
    case 16:
        if unsigned {
            return reflect.Uint16, uint16T
        }
        return reflect.Int16, int16T
    case 32:
        if unsigned {
            return reflect.Uint32, uint32T
        }
        return reflect.Int32, int32T
    case 64:
        if unsigned {
            return reflect.Uint64, uint64T
        }
        return reflect.Int64, int64T
    }
    return reflect.Ptr, bigT
}

// mustArrayToBytesSlice 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() != derefbigT:
        return set(dst.Elem(), src)
    case srcType.AssignableTo(dstType) && dst.CanSet():
        dst.Set(src)
    case dstType.Kind() == reflect.Slice && srcType.Kind() == reflect.Slice:
        return setSlice(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
func setSlice(dst, src reflect.Value) error {
    slice := reflect.MakeSlice(dst.Type(), src.Len(), src.Len())
    for i := 0; i < src.Len(); i++ {
        v := src.Index(i)
        reflect.Copy(slice.Index(i), v)
    }

    dst.Set(slice)
    return nil
}

// requireAssignable assures that `dest` is a pointer and it's not an interface.
func requireAssignable(dst, src reflect.Value) error {
    if dst.Kind() != reflect.Ptr && dst.Kind() != reflect.Interface {
        return fmt.Errorf("abi: cannot unmarshal %v into %v", src.Type(), dst.Type())
    }
    return nil
}

// requireUnpackKind verifies preconditions for unpacking `args` into `kind`
func requireUnpackKind(v reflect.Value, t reflect.Type, k reflect.Kind,
    args Arguments) error {

    switch k {
    case reflect.Struct:
    case reflect.Slice, reflect.Array:
        if minLen := args.LengthNonIndexed(); v.Len() < minLen {
            return fmt.Errorf("abi: insufficient number of elements in the list/array for unpack, want %d, got %d",
                minLen, v.Len())
        }
    default:
        return fmt.Errorf("abi: cannot unmarshal tuple into %v", t)
    }
    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.
        var ok bool
        var tagName string
        if tagName, ok = typ.Field(i).Tag.Lookup("abi"); !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
}