arbitrum: Add helper to check resource kind

arbitrum/multigas/resources.go

@@ -2,6 +2,7 @@ package multigas
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
 	"math/bits"
 
@@ -25,6 +26,14 @@ const (
 	NumResourceKind
 )
 
+// CheckResourceKind checks whether the given id is a valid resource.
+func CheckResourceKind(id uint8) (ResourceKind, error) {
+	if id <= uint8(ResourceKindUnknown) || id >= uint8(NumResourceKind) {
+		return ResourceKindUnknown, fmt.Errorf("invalid resource id: %v", id)
+	}
+	return ResourceKind(id), nil
+}
+
 // MultiGas tracks gas usage across multiple resource kinds, while also
 // maintaining a single-dimensional total gas sum and refund amount.
 type MultiGas struct {

arbitrum/multigas/resources_test.go

@@ -10,6 +10,24 @@ import (
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
+func TestCheckResourceKind(t *testing.T) {
+	_, err := CheckResourceKind(0)
+	if err == nil {
+		t.Errorf("expected error, got nil")
+	}
+	_, err = CheckResourceKind(uint8(NumResourceKind))
+	if err == nil {
+		t.Errorf("expected error, got nil")
+	}
+	resource, err := CheckResourceKind(uint8(ResourceKindComputation))
+	if err != nil {
+		t.Errorf("unexpected error, got %v", err)
+	}
+	if resource != ResourceKindComputation {
+		t.Errorf("expected computation resource, got %v", resource)
+	}
+}
+
 func TestZeroGas(t *testing.T) {
 	zero := ZeroGas()
 	if zero.SingleGas() != 0 {