path: root/accounts/abi/event.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"

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

// Event is an event potentially triggered by the EVM's LOG mechanism. The Event
// holds type information (inputs) about the yielded output. Anonymous events
// don't get the signature canonical representation as the first LOG topic.
type Event struct {
    Name      string
    Anonymous bool
    Inputs    []Argument
}

// Id returns the canonical representation of the event's signature used by the
// abi definition to identify event names and types.
func (e Event) Id() common.Hash {
    types := make([]string, len(e.Inputs))
    i := 0
    for _, input := range e.Inputs {
        types[i] = input.Type.String()
        i++
    }
    return common.BytesToHash(crypto.Keccak256([]byte(fmt.Sprintf("%v(%v)", e.Name, strings.Join(types, ",")))))
}

// unpacks an event return tuple into a struct of corresponding go types
//
// Unpacking can be done into a struct or a slice/array.
func (e Event) tupleUnpack(v interface{}, output []byte) error {
    // 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()
        kind  = value.Kind()
    )
    if err := requireUnpackKind(value, typ, kind, e.Inputs, true); err != nil {
        return err
    }

    // `i` counts the nonindexed arguments.
    // `j` counts the number of complex types.
    // both `i` and `j` are used to to correctly compute `data` offset.
    i, j := -1, 0
    for _, input := range e.Inputs {
        if input.Indexed {
            // Indexed arguments are not packed into data
            continue
        }
        i++
        marshalledValue, err := toGoType((i+j)*32, input.Type, output)
        if err != nil {
            return err
        }
        if input.Type.T == ArrayTy {
            // combined index ('i' + 'j') need to be adjusted only by size of array, thus
            // we need to decrement 'j' because 'i' was incremented
            j += input.Type.Size - 1
        }
        reflectValue := reflect.ValueOf(marshalledValue)

        switch kind {
        case reflect.Struct:
            for j := 0; j < typ.NumField(); j++ {
                field := typ.Field(j)
                // TODO read tags: `abi:"fieldName"`
                if field.Name == strings.ToUpper(input.Name[:1])+input.Name[1:] {
                    if err := set(value.Field(j), reflectValue, input); err != nil {
                        return err
                    }
                }
            }
        case reflect.Slice, reflect.Array:
            v := value.Index(i)
            if err := requireAssignable(v, reflectValue); err != nil {
                return err
            }
            if err := set(v.Elem(), reflectValue, input); err != nil {
                return err
            }
        }
    }
    return nil
}

func (e Event) isTupleReturn() bool { return len(e.Inputs) > 1 }

func (e Event) singleUnpack(v interface{}, output []byte) error {
    // 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)
    }

    if e.Inputs[0].Indexed {
        return fmt.Errorf("abi: attempting to unpack indexed variable into element.")
    }

    value := valueOf.Elem()

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