Support encoding of pointers as interface types

asn1_test.go

@@ -4,6 +4,7 @@ import (
 	"math/big"
 	"reflect"
 	"testing"
+	"fmt"
 )
 
 // isBytesEqual compares two byte arrays/slices.
@@ -26,9 +27,14 @@ type testCase struct {
 	expected []byte
 }
 
+func (t testCase) String() string {
+	return fmt.Sprintf("testCase: value %#v (%T) expects %#v", t.value, t.value, t.expected)
+}
+
 // testEncode encodes an object and compares with the expected bytes.
 func testEncode(t *testing.T, ctx *Context, options string, tests ...testCase) {
 	for _, test := range tests {
+		t.Logf("Testing case: %v", test)
 		data, err := ctx.EncodeWithOptions(test.value, options)
 		if err != nil {
 			t.Fatal(err)
@@ -670,3 +676,30 @@ func TestArraySlice(t *testing.T) {
 	ctx := NewContext()
 	testEncodeDecode(t, ctx, "", testCases...)
 }
+
+func TestPointerInterface(t *testing.T) {
+	type I interface {}
+	type Type struct {
+		A int
+		B string
+		C bool
+	}
+	var obj I
+	obj = &Type{1, "abc", true}
+	ctx := NewContext()
+	// We cannot use testSimple because the type is I
+	data, err := ctx.Encode(obj)
+	if err != nil {
+		t.Fatal(err)
+	}
+	value := new(Type)
+	rest, err := ctx.Decode(data, value)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(rest) > 0 {
+		t.Fatalf("Unexpected remaining bytes when decoding \"%v\": %#v\n",
+			obj, rest)
+	}
+	checkEqual(t, obj, value)
+}

encode.go

@@ -37,10 +37,7 @@ func (ctx *Context) EncodeWithOptions(obj interface{}, options string) (data []b
 func (ctx *Context) encode(value reflect.Value, opts *fieldOptions) (*rawValue, error) {
 
 	// Skip the interface type
-	switch value.Kind() {
-	case reflect.Interface:
-		value = value.Elem()
-	}
+	value = getActualType(value)
 
 	// If a value is missing the default value is used
 	empty := isEmpty(value)

types.go

@@ -347,6 +347,21 @@ func (ctx *Context) decodeNull(data []byte, value reflect.Value) error {
  * Helper functions
  */
 
+// getActualType recursively gets the underlying type of Interfaces and Pointers.
+func getActualType(value reflect.Value) reflect.Value {
+	for {
+		if value.Type() == bigIntType {
+			return value
+		}
+		switch value.Kind() {
+		case reflect.Interface, reflect.Ptr:
+			value = value.Elem()
+		default:
+			return value
+		}
+	}
+}
+
 func checkInt(ctx *Context, data []byte) error {
 	if ctx.der.decoding {
 		if len(data) >= 2 {