Add a function to generate frc42 method number (#129)

* Add a function to generate frc42 method number

abi/actor.go

@@ -1,6 +1,8 @@
 package abi
 
-import "strconv"
+import (
+	"strconv"
+)
 
 // A sequential number assigned to an actor when created by the InitActor.
 // This ID is embedded in ID-type addresses.
@@ -35,4 +37,3 @@ type Multiaddrs = []byte
 
 // PeerID is a byte array representing a Libp2p PeerID
 type PeerID = []byte
-

builtin/methods.go

@@ -1,7 +1,11 @@
 package builtin
 
 import (
+	"encoding/binary"
 	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/minio/blake2b-simd"
+	"golang.org/x/xerrors"
+	"unicode"
 )
 
 const (
@@ -161,3 +165,45 @@ var MethodsEAM = struct {
 	Create      abi.MethodNum
 	Create2     abi.MethodNum
 }{MethodConstructor, 2, 3}
+
+// Generates a standard FRC-42 compliant method number
+// Reference: https://github.com/filecoin-project/FIPs/blob/master/FRCs/frc-0042.md
+func GenerateMethodNum(name string) (abi.MethodNum, error) {
+	err := validateMethodName(name)
+	if err != nil {
+		return 0, err
+	}
+
+	if name == "Constructor" {
+		return MethodConstructor, nil
+	}
+
+	digest := blake2b.Sum512([]byte("1|" + name))
+
+	for i := 0; i < 64; i += 4 {
+		methodId := binary.BigEndian.Uint32(digest[i : i+4])
+		if methodId >= (1 << 24) {
+			return abi.MethodNum(methodId), nil
+		}
+	}
+
+	return abi.MethodNum(0), xerrors.Errorf("Could not generate method num from method name %s:", name)
+}
+
+func validateMethodName(name string) error {
+	if name == "" {
+		return xerrors.Errorf("empty name string")
+	}
+
+	if !unicode.IsUpper(rune(name[0])) {
+		return xerrors.Errorf("Method name first letter must be uppercase, method name: %s", name)
+	}
+
+	for _, c := range name {
+		if !(unicode.IsLetter(c) || unicode.IsDigit(c) || c == '_') {
+			return xerrors.Errorf("method name has illegal characters, method name: %s", name)
+		}
+	}
+
+	return nil
+}

builtin/methods_test.go

@@ -0,0 +1,14 @@
+package builtin
+
+import (
+	"github.com/filecoin-project/go-state-types/abi"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestGenerateMethodNum(t *testing.T) {
+
+	methodNum, err := GenerateMethodNum("Receive")
+	require.NoError(t, err)
+	require.Equal(t, methodNum, abi.MethodNum(3726118371))
+}

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/ipfs/go-block-format v0.0.3
 	github.com/ipfs/go-cid v0.2.0
 	github.com/ipfs/go-ipld-cbor v0.0.6
+	github.com/minio/blake2b-simd v0.0.0-20160723061019-3f5f724cb5b1
 	github.com/multiformats/go-multibase v0.0.3
 	github.com/multiformats/go-multihash v0.0.15
 	github.com/multiformats/go-varint v0.0.6