customize CallContract

Author: CoderZhi

accounts/abi/abi.go

@@ -0,0 +1,146 @@
+// 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 (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+)
+
+// 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
+	if name == "" {
+		// constructor
+		arguments, err := abi.Constructor.Inputs.Pack(args...)
+		if err != nil {
+			return nil, err
+		}
+		return arguments, nil
+
+	}
+	method, exist := abi.Methods[name]
+	if !exist {
+		return nil, fmt.Errorf("method '%s' not found", name)
+	}
+
+	arguments, err := method.Inputs.Pack(args...)
+	if err != nil {
+		return nil, err
+	}
+	// Pack up the method ID too if not a constructor and return
+	return append(method.Id(), arguments...), nil
+}
+
+// Unpack output in v according to the abi specification
+func (abi ABI) Unpack(v interface{}, name string, output []byte) (err error) {
+	if len(output) == 0 {
+		return fmt.Errorf("abi: unmarshalling empty output")
+	}
+	// since there can't be naming collisions with contracts and events,
+	// we need to decide whether we're calling a method or an event
+	if method, ok := abi.Methods[name]; ok {
+		if len(output)%32 != 0 {
+			return fmt.Errorf("abi: improperly formatted output")
+		}
+		return method.Outputs.Unpack(v, output)
+	} else if event, ok := abi.Events[name]; ok {
+		return event.Inputs.Unpack(v, output)
+	}
+	return fmt.Errorf("abi: could not locate named method or event")
+}
+
+// UnmarshalJSON implements json.Unmarshaler interface
+func (abi *ABI) UnmarshalJSON(data []byte) error {
+	var fields []struct {
+		Type      string
+		Name      string
+		Constant  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
+}
+
+// MethodById looks up a method by the 4-byte id
+// returns nil if none found
+func (abi *ABI) MethodById(sigdata []byte) (*Method, error) {
+	for _, method := range abi.Methods {
+		if bytes.Equal(method.Id(), sigdata[:4]) {
+			return &method, nil
+		}
+	}
+	return nil, fmt.Errorf("no method with id: %#x", sigdata[:4])
+}