path: root/accounts/abi/argument.go

// Copyright 2015 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 (
    "encoding/json"
    "fmt"
    "reflect"
    "strings"
)

// Argument holds the name of the argument and the corresponding type.
// Types are used when packing and testing arguments.
type Argument struct {
    Name    string
    Type    Type
    Indexed bool // indexed is only used by events
}

type Arguments []Argument

// UnmarshalJSON implements json.Unmarshaler interface
func (argument *Argument) UnmarshalJSON(data []byte) error {
    var extarg struct {
        Name    string
        Type    string
        Indexed bool
    }
    err := json.Unmarshal(data, &extarg)
    if err != nil {
        return fmt.Errorf("argument json err: %v", err)
    }

    argument.Type, err = NewType(extarg.Type)
    if err != nil {
        return err
    }
    argument.Name = extarg.Name
    argument.Indexed = extarg.Indexed

    return nil
}

// LengthNonIndexed returns the number of arguments when not counting 'indexed' ones. Only events
// can ever have 'indexed' arguments, it should always be false on arguments for method input/output
func (arguments Arguments) LengthNonIndexed() int {
    out := 0
    for _, arg := range arguments {
        if !arg.Indexed {
            out++
        }
    }
    return out
}

// NonIndexed returns the arguments with indexed arguments filtered out
func (arguments Arguments) NonIndexed() Arguments {
    var ret []Argument
    for _, arg := range arguments {
        if !arg.Indexed {
            ret = append(ret, arg)
        }
    }
    return ret
}

// isTuple returns true for non-atomic constructs, like (uint,uint) or uint[]
func (arguments Arguments) isTuple() bool {
    return len(arguments) > 1
}

// Unpack performs the operation hexdata -> Go format
func (arguments Arguments) Unpack(v interface{}, data []byte) error {

    // make sure the passed value is arguments pointer
    if reflect.Ptr != reflect.ValueOf(v).Kind() {
        return fmt.Errorf("abi: Unpack(non-pointer %T)", v)
    }
    marshalledValues, err := arguments.UnpackValues(data)
    if err != nil {
        return err
    }
    if arguments.isTuple() {
        return arguments.unpackTuple(v, marshalledValues)
    }
    return arguments.unpackAtomic(v, marshalledValues)
}

func (arguments Arguments) unpackTuple(v interface{}, marshalledValues []interface{}) error {

    var (
        value = reflect.ValueOf(v).Elem()
        typ   = value.Type()
        kind  = value.Kind()
    )

    if err := requireUnpackKind(value, typ, kind, arguments); err != nil {
        return err
    }
    // If the output interface is a struct, make sure names don't collide
    if kind == reflect.Struct {
        exists := make(map[string]bool)
        for _, arg := range arguments {
            field := capitalise(arg.Name)
            if field == "" {
                return fmt.Errorf("abi: purely underscored output cannot unpack to struct")
            }
            if exists[field] {
                return fmt.Errorf("abi: multiple outputs mapping to the same struct field '%s'", field)
            }
            exists[field] = true
        }
    }
    for i, arg := range arguments.NonIndexed() {

        reflectValue := reflect.ValueOf(marshalledValues[i])

        switch kind {
        case reflect.Struct:
            name := capitalise(arg.Name)
            for j := 0; j < typ.NumField(); j++ {
                // TODO read tags: `abi:"fieldName"`
                if typ.Field(j).Name == name {
                    if err := set(value.Field(j), reflectValue, arg); err != nil {
                        return err
                    }
                }
            }
        case reflect.Slice, reflect.Array:
            if value.Len() < i {
                return fmt.Errorf("abi: insufficient number of arguments for unpack, want %d, got %d", len(arguments), value.Len())
            }
            v := value.Index(i)
            if err := requireAssignable(v, reflectValue); err != nil {
                return err
            }

            if err := set(v.Elem(), reflectValue, arg); err != nil {
                return err
            }
        default:
            return fmt.Errorf("abi:[2] cannot unmarshal tuple in to %v", typ)
        }
    }
    return nil
}

// unpackAtomic unpacks ( hexdata -> go ) a single value
func (arguments Arguments) unpackAtomic(v interface{}, marshalledValues []interface{}) error {
    if len(marshalledValues) != 1 {
        return fmt.Errorf("abi: wrong length, expected single value, got %d", len(marshalledValues))
    }
    elem := reflect.ValueOf(v).Elem()
    reflectValue := reflect.ValueOf(marshalledValues[0])
    return set(elem, reflectValue, arguments.NonIndexed()[0])
}

// Computes the full size of an array;
// i.e. counting nested arrays, which count towards size for unpacking.
func getArraySize(arr *Type) int {
    size := arr.Size
    // Arrays can be nested, with each element being the same size
    arr = arr.Elem
    for arr.T == ArrayTy {
        // Keep multiplying by elem.Size while the elem is an array.
        size *= arr.Size
        arr = arr.Elem
    }
    // Now we have the full array size, including its children.
    return size
}

// UnpackValues can be used to unpack ABI-encoded hexdata according to the ABI-specification,
// without supplying a struct to unpack into. Instead, this method returns a list containing the
// values. An atomic argument will be a list with one element.
func (arguments Arguments) UnpackValues(data []byte) ([]interface{}, error) {
    retval := make([]interface{}, 0, arguments.LengthNonIndexed())
    virtualArgs := 0
    for index, arg := range arguments.NonIndexed() {
        marshalledValue, err := toGoType((index+virtualArgs)*32, arg.Type, data)
        if arg.Type.T == ArrayTy {
            // If we have a static array, like [3]uint256, these are coded as
            // just like uint256,uint256,uint256.
            // This means that we need to add two 'virtual' arguments when
            // we count the index from now on.
            //
            // Array values nested multiple levels deep are also encoded inline:
            // [2][3]uint256: uint256,uint256,uint256,uint256,uint256,uint256
            //
            // Calculate the full array size to get the correct offset for the next argument.
            // Decrement it by 1, as the normal index increment is still applied.
            virtualArgs += getArraySize(&arg.Type) - 1
        }
        if err != nil {
            return nil, err
        }
        retval = append(retval, marshalledValue)
    }
    return retval, nil
}

// PackValues performs the operation Go format -> Hexdata
// It is the semantic opposite of UnpackValues
func (arguments Arguments) PackValues(args []interface{}) ([]byte, error) {
    return arguments.Pack(args...)
}

// Pack performs the operation Go format -> Hexdata
func (arguments Arguments) Pack(args ...interface{}) ([]byte, error) {
    // Make sure arguments match up and pack them
    abiArgs := arguments
    if len(args) != len(abiArgs) {
        return nil, fmt.Errorf("argument count mismatch: %d for %d", len(args), len(abiArgs))
    }
    // variable input is the output appended at the end of packed
    // output. This is used for strings and bytes types input.
    var variableInput []byte

    // input offset is the bytes offset for packed output
    inputOffset := 0
    for _, abiArg := range abiArgs {
        if abiArg.Type.T == ArrayTy {
            inputOffset += 32 * abiArg.Type.Size
        } else {
            inputOffset += 32
        }
    }
    var ret []byte
    for i, a := range args {
        input := abiArgs[i]
        // pack the input
        packed, err := input.Type.pack(reflect.ValueOf(a))
        if err != nil {
            return nil, err
        }
        // check for a slice type (string, bytes, slice)
        if input.Type.requiresLengthPrefix() {
            // calculate the offset
            offset := inputOffset + len(variableInput)
            // set the offset
            ret = append(ret, packNum(reflect.ValueOf(offset))...)
            // Append the packed output to the variable input. The variable input
            // will be appended at the end of the input.
            variableInput = append(variableInput, packed...)
        } else {
            // append the packed value to the input
            ret = append(ret, packed...)
        }
    }
    // append the variable input at the end of the packed input
    ret = append(ret, variableInput...)

    return ret, nil
}

// capitalise makes the first character of a string upper case, also removing any
// prefixing underscores from the variable names.
func capitalise(input string) string {
    for len(input) > 0 && input[0] == '_' {
        input = input[1:]
    }
    if len(input) == 0 {
        return ""
    }
    return strings.ToUpper(input[:1]) + input[1:]
}