Implemented contract ABI

1 files changed, 155 insertions, 0 deletions

diff --git a/accounts/abi/abi.go b/accounts/abi/abi.go
new file mode 100644
index 000000000..067381a48
--- /dev/null
+++ b/accounts/abi/abi.go
@@ -0,0 +1,155 @@
+package abi
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+// Callable method given a `Name` and whether the method is a constant.
+// If the method is `Const` no transaction needs to be created for this
+// particular Method call. It can easily be simulated using a local VM.
+// For example a `Balance()` method only needs to retrieve something
+// from the storage and therefor requires no Tx to be send to the
+// network. A method such as `Transact` does require a Tx and thus will
+// be flagged `true`.
+// Input specifies the required input parameters for this gives method.
+type Method struct {
+	Name   string
+	Const  bool
+	Input  []Argument
+	Return Type // not yet implemented
+}
+
+// Returns the methods string signature according to the ABI spec.
+//
+// Example
+//
+//     function foo(uint32 a, int b)    =    "foo(uint32,int256)"
+//
+// Please note that "int" is substitute for its canonical representation "int256"
+func (m Method) String() (out string) {
+	out += m.Name
+	types := make([]string, len(m.Input))
+	i := 0
+	for _, input := range m.Input {
+		types[i] = input.Type.String()
+		i++
+	}
+	out += "(" + strings.Join(types, ",") + ")"
+
+	return
+}
+
+func (m Method) Id() []byte {
+	return crypto.Sha3([]byte(m.String()))[:4]
+}
+
+// Argument holds the name of the argument and the corresponding type.
+// Types are used when packing and testing arguments.
+type Argument struct {
+	Name string
+	Type Type
+}
+
+func (a *Argument) UnmarshalJSON(data []byte) error {
+	var extarg struct {
+		Name string
+		Type string
+	}
+	err := json.Unmarshal(data, &extarg)
+	if err != nil {
+		return fmt.Errorf("argument json err: %v", err)
+	}
+
+	a.Type, err = NewType(extarg.Type)
+	if err != nil {
+		return err
+	}
+	a.Name = extarg.Name
+
+	return nil
+}
+
+// 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 {
+	Methods map[string]Method
+}
+
+// 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(name string, args ...interface{}) ([]byte, error) {
+	method := abi.Methods[name]
+
+	var ret []byte
+	for i, a := range args {
+		input := method.Input[i]
+
+		packed, err := input.Type.pack(a)
+		if err != nil {
+			return nil, fmt.Errorf("`%s` %v", name, err)
+		}
+		ret = append(ret, packed...)
+
+	}
+
+	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) {
+	method, exist := abi.Methods[name]
+	if !exist {
+		return nil, fmt.Errorf("method '%s' not found", name)
+	}
+
+	// start with argument count match
+	if len(args) != len(method.Input) {
+		return nil, fmt.Errorf("argument count mismatch: %d for %d", len(args), len(method.Input))
+	}
+
+	arguments, err := abi.pack(name, args...)
+	if err != nil {
+		return nil, err
+	}
+
+	// Set function id
+	packed := abi.Methods[name].Id()
+	packed = append(packed, arguments...)
+
+	return packed, nil
+}
+
+func (abi *ABI) UnmarshalJSON(data []byte) error {
+	var methods []Method
+	if err := json.Unmarshal(data, &methods); err != nil {
+		return err
+	}
+
+	abi.Methods = make(map[string]Method)
+	for _, method := range methods {
+		abi.Methods[method.Name] = method
+	}
+
+	return nil
+}
+
+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
+}