a0bf2ea7e7
Added calling mechanism and return value parsing
164 lines
4.7 KiB
Go
164 lines
4.7 KiB
Go
// Copyright 2015 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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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
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// 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
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package abi
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import (
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"encoding/json"
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"fmt"
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"io"
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"math"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/logger"
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"github.com/ethereum/go-ethereum/logger/glog"
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)
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// Executer is an executer method for performing state executions. It takes one
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// argument which is the input data and expects output data to be returned as
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// multiple 32 byte word length concatenated slice
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type Executer func(datain []byte) []byte
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// The ABI holds information about a contract's context and available
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// invokable methods. It will allow you to type check function calls and
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// packs data accordingly.
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type ABI struct {
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Methods map[string]Method
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}
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// JSON returns a parsed ABI interface and error if it failed.
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func JSON(reader io.Reader) (ABI, error) {
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dec := json.NewDecoder(reader)
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var abi ABI
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if err := dec.Decode(&abi); err != nil {
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return ABI{}, err
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}
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return abi, nil
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}
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// tests, tests whether the given input would result in a successful
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// call. Checks argument list count and matches input to `input`.
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func (abi ABI) pack(name string, args ...interface{}) ([]byte, error) {
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method := abi.Methods[name]
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var ret []byte
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for i, a := range args {
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input := method.Inputs[i]
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packed, err := input.Type.pack(a)
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if err != nil {
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return nil, fmt.Errorf("`%s` %v", name, err)
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}
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ret = append(ret, packed...)
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}
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return ret, nil
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}
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// Pack the given method name to conform the ABI. Method call's data
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// will consist of method_id, args0, arg1, ... argN. Method id consists
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// of 4 bytes and arguments are all 32 bytes.
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// Method ids are created from the first 4 bytes of the hash of the
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// methods string signature. (signature = baz(uint32,string32))
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func (abi ABI) Pack(name string, args ...interface{}) ([]byte, error) {
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method, exist := abi.Methods[name]
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if !exist {
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return nil, fmt.Errorf("method '%s' not found", name)
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}
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// start with argument count match
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if len(args) != len(method.Inputs) {
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return nil, fmt.Errorf("argument count mismatch: %d for %d", len(args), len(method.Inputs))
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}
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arguments, err := abi.pack(name, args...)
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if err != nil {
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return nil, err
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}
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// Set function id
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packed := abi.Methods[name].Id()
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packed = append(packed, arguments...)
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return packed, nil
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}
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// toGoType parses the input and casts it to the proper type defined by the ABI
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// argument in t.
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func toGoType(t Argument, input []byte) interface{} {
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switch t.Type.T {
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case IntTy:
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return common.BytesToBig(input)
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case UintTy:
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return common.BytesToBig(input)
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case BoolTy:
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return common.BytesToBig(input).Uint64() > 0
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case AddressTy:
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return common.BytesToAddress(input)
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case HashTy:
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return common.BytesToHash(input)
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}
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return nil
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}
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// Call executes a call and attemps to parse the return values and returns it as
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// an interface. It uses the executer method to perform the actual call since
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// the abi knows nothing of the lower level calling mechanism.
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//
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// Call supports all abi types and includes multiple return values. When only
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// one item is returned a single interface{} will be returned, if a contract
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// method returns multiple values an []interface{} slice is returned.
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func (abi ABI) Call(executer Executer, name string, args ...interface{}) interface{} {
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callData, err := abi.Pack(name, args...)
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if err != nil {
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glog.V(logger.Debug).Infoln("pack error:", err)
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return nil
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}
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output := executer(callData)
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method := abi.Methods[name]
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ret := make([]interface{}, int(math.Max(float64(len(method.Outputs)), float64(len(output)/32))))
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for i := 0; i < len(ret); i += 32 {
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index := i / 32
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ret[index] = toGoType(method.Outputs[index], output[i:i+32])
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}
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// return single interface
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if len(ret) == 1 {
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return ret[0]
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}
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return ret
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}
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func (abi *ABI) UnmarshalJSON(data []byte) error {
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var methods []Method
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if err := json.Unmarshal(data, &methods); err != nil {
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return err
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}
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abi.Methods = make(map[string]Method)
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for _, method := range methods {
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abi.Methods[method.Name] = method
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}
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return nil
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}
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