plugeth/accounts/abi/abi.go

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// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
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//
// The go-ethereum library is free software: you can redistribute it and/or modify
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// 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,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// 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/>.
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package abi
import (
"encoding/json"
"fmt"
"io"
"reflect"
"strings"
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"github.com/ethereum/go-ethereum/common"
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)
// 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
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}
// 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
}
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// tests, tests whether the given input would result in a successful
// call. Checks argument list count and matches input to `input`.
func (abi ABI) pack(method Method, args ...interface{}) ([]byte, error) {
// variable input is the output appended at the end of packed
// output. This is used for strings and bytes types input.
var variableInput []byte
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var ret []byte
for i, a := range args {
input := method.Inputs[i]
// pack the input
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packed, err := input.Type.pack(a)
if err != nil {
return nil, fmt.Errorf("`%s` %v", method.Name, err)
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}
// check for a slice type (string, bytes, slice)
if input.Type.T == StringTy || input.Type.T == BytesTy || input.Type.IsSlice {
// calculate the offset
offset := len(method.Inputs)*32 + len(variableInput)
// set the offset
ret = append(ret, packNum(reflect.ValueOf(offset), UintTy)...)
// 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...)
}
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}
// append the variable input at the end of the packed input
ret = append(ret, variableInput...)
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return ret, 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
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if name == "" {
method = abi.Constructor
} else {
m, exist := abi.Methods[name]
if !exist {
return nil, fmt.Errorf("method '%s' not found", name)
}
method = m
}
// Make sure arguments match up and pack them
if len(args) != len(method.Inputs) {
return nil, fmt.Errorf("argument count mismatch: %d for %d", len(args), len(method.Inputs))
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}
arguments, err := abi.pack(method, args...)
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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
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}
// toGoType parses the input and casts it to the proper type defined by the ABI
// argument in T.
func toGoType(i int, t Argument, output []byte) (interface{}, error) {
index := i * 32
if index+32 > len(output) {
return nil, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %d require %d", len(output), index+32)
}
// Parse the given index output and check whether we need to read
// a different offset and length based on the type (i.e. string, bytes)
var returnOutput []byte
switch t.Type.T {
case StringTy, BytesTy: // variable arrays are written at the end of the return bytes
// parse offset from which we should start reading
offset := int(common.BytesToBig(output[index : index+32]).Uint64())
if offset+32 > len(output) {
return nil, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %d require %d", len(output), offset+32)
}
// parse the size up until we should be reading
size := int(common.BytesToBig(output[offset : offset+32]).Uint64())
if offset+32+size > len(output) {
return nil, fmt.Errorf("abi: cannot marshal in to go type: length insufficient %d require %d", len(output), offset+32+size)
}
// get the bytes for this return value
returnOutput = output[offset+32 : offset+32+size]
default:
returnOutput = output[index : index+32]
}
// cast bytes to abi return type
switch t.Type.T {
case IntTy:
return common.BytesToBig(returnOutput), nil
case UintTy:
return common.BytesToBig(returnOutput), nil
case BoolTy:
return common.BytesToBig(returnOutput).Uint64() > 0, nil
case AddressTy:
return common.BytesToAddress(returnOutput), nil
case HashTy:
return common.BytesToHash(returnOutput), nil
case BytesTy, FixedBytesTy:
return returnOutput, nil
case StringTy:
return string(returnOutput), nil
}
return nil, fmt.Errorf("abi: unknown type %v", t.Type.T)
}
// 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")
}
value := reflect.ValueOf(v).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)
}
// 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
}
// 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, output Argument) error {
dstType := dst.Type()
srcType := src.Type()
switch {
case dstType.AssignableTo(src.Type()):
dst.Set(src)
case dstType.Kind() == reflect.Array && srcType.Kind() == reflect.Slice:
if !dstType.Elem().AssignableTo(r_byte) {
return fmt.Errorf("abi: cannot unmarshal %v in to array of elem %v", src.Type(), dstType.Elem())
}
if dst.Len() < output.Type.Size {
return fmt.Errorf("abi: cannot unmarshal src (len=%d) in to dst (len=%d)", output.Type.Size, dst.Len())
}
reflect.Copy(dst, src)
default:
return fmt.Errorf("abi: cannot unmarshal %v in to %v", src.Type(), dst.Type())
}
return nil
}
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func (abi *ABI) UnmarshalJSON(data []byte) error {
var fields []struct {
Type string
Name string
Constant bool
Indexed bool
Inputs []Argument
Outputs []Argument
}
if err := json.Unmarshal(data, &fields); err != nil {
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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,
Inputs: field.Inputs,
}
}
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}
return nil
}