path: root/accounts/abi/abi.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"
    "io"
    "reflect"
    "strings"

    "github.com/ethereum/go-ethereum/common"
)

// The ABI holds information about a contract's context and available
// invokable methods. It will allow you to type check function calls and
// packs data accordingly.
type ABI struct {
    Constructor Method
    Methods     map[string]Method
    Events      map[string]Event
}

// JSON returns a parsed ABI interface and error if it failed.
func JSON(reader io.Reader) (ABI, error) {
    dec := json.NewDecoder(reader)

    var abi ABI
    if err := dec.Decode(&abi); err != nil {
        return ABI{}, err
    }

    return abi, nil
}

// Pack the given method name to conform the ABI. Method call's data
// will consist of method_id, args0, arg1, ... argN. Method id consists
// of 4 bytes and arguments are all 32 bytes.
// Method ids are created from the first 4 bytes of the hash of the
// methods string signature. (signature = baz(uint32,string32))
func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
    // Fetch the ABI of the requested method
    var method Method

    if name == "" {
        method = abi.Constructor
    } else {
        m, exist := abi.Methods[name]
        if !exist {
            return nil, fmt.Errorf("method '%s' not found", name)
        }
        method = m
    }
    arguments, err := method.pack(args...)
    if err != nil {
        return nil, err
    }
    // Pack up the method ID too if not a constructor and return
    if name == "" {
        return arguments, nil
    }
    return append(method.Id(), arguments...), nil
}

// these variable are used to determine certain types during type assertion for
// assignment.
var (
    r_interSlice = reflect.TypeOf([]interface{}{})
    r_hash       = reflect.TypeOf(common.Hash{})
    r_bytes      = reflect.TypeOf([]byte{})
    r_byte       = reflect.TypeOf(byte(0))
)

// Unpack output in v according to the abi specification
func (abi ABI) Unpack(v interface{}, name string, output []byte) error {
    var method = abi.Methods[name]

    if len(output) == 0 {
        return fmt.Errorf("abi: unmarshalling empty output")
    }

    // make sure the passed value is a pointer
    valueOf := reflect.ValueOf(v)
    if reflect.Ptr != valueOf.Kind() {
        return fmt.Errorf("abi: Unpack(non-pointer %T)", v)
    }

    var (
        value = valueOf.Elem()
        typ   = value.Type()
    )

    if len(method.Outputs) > 1 {
        switch value.Kind() {
        // struct will match named return values to the struct's field
        // names
        case reflect.Struct:
            for i := 0; i < len(method.Outputs); i++ {
                marshalledValue, err := toGoType(i, method.Outputs[i], output)
                if err != nil {
                    return err
                }
                reflectValue := reflect.ValueOf(marshalledValue)

                for j := 0; j < typ.NumField(); j++ {
                    field := typ.Field(j)
                    // TODO read tags: `abi:"fieldName"`
                    if field.Name == strings.ToUpper(method.Outputs[i].Name[:1])+method.Outputs[i].Name[1:] {
                        if err := set(value.Field(j), reflectValue, method.Outputs[i]); err != nil {
                            return err
                        }
                    }
                }
            }
        case reflect.Slice:
            if !value.Type().AssignableTo(r_interSlice) {
                return fmt.Errorf("abi: cannot marshal tuple in to slice %T (only []interface{} is supported)", v)
            }

            // if the slice already contains values, set those instead of the interface slice itself.
            if value.Len() > 0 {
                if len(method.Outputs) > value.Len() {
                    return fmt.Errorf("abi: cannot marshal in to slices of unequal size (require: %v, got: %v)", len(method.Outputs), value.Len())
                }

                for i := 0; i < len(method.Outputs); i++ {
                    marshalledValue, err := toGoType(i, method.Outputs[i], output)
                    if err != nil {
                        return err
                    }
                    reflectValue := reflect.ValueOf(marshalledValue)
                    if err := set(value.Index(i).Elem(), reflectValue, method.Outputs[i]); err != nil {
                        return err
                    }
                }
                return nil
            }

            // create a new slice and start appending the unmarshalled
            // values to the new interface slice.
            z := reflect.MakeSlice(typ, 0, len(method.Outputs))
            for i := 0; i < len(method.Outputs); i++ {
                marshalledValue, err := toGoType(i, method.Outputs[i], output)
                if err != nil {
                    return err
                }
                z = reflect.Append(z, reflect.ValueOf(marshalledValue))
            }
            value.Set(z)
        default:
            return fmt.Errorf("abi: cannot unmarshal tuple in to %v", typ)
        }

    } else {
        marshalledValue, err := toGoType(0, method.Outputs[0], output)
        if err != nil {
            return err
        }
        if err := set(value, reflect.ValueOf(marshalledValue), method.Outputs[0]); err != nil {
            return err
        }
    }

    return nil
}

func (abi *ABI) UnmarshalJSON(data []byte) error {
    var fields []struct {
        Type      string
        Name      string
        Constant  bool
        Indexed   bool
        Anonymous bool
        Inputs    []Argument
        Outputs   []Argument
    }

    if err := json.Unmarshal(data, &fields); err != nil {
        return err
    }

    abi.Methods = make(map[string]Method)
    abi.Events = make(map[string]Event)
    for _, field := range fields {
        switch field.Type {
        case "constructor":
            abi.Constructor = Method{
                Inputs: field.Inputs,
            }
        // empty defaults to function according to the abi spec
        case "function", "":
            abi.Methods[field.Name] = Method{
                Name:    field.Name,
                Const:   field.Constant,
                Inputs:  field.Inputs,
                Outputs: field.Outputs,
            }
        case "event":
            abi.Events[field.Name] = Event{
                Name:      field.Name,
                Anonymous: field.Anonymous,
                Inputs:    field.Inputs,
            }
        }
    }

    return nil
}