FEAT: implemented passing a struct value to an extension

resolves: Oldes/Rebol-issues#2536

src/boot/types-ext.reb

@@ -61,3 +61,5 @@ gob			47	ser
 object		48	object
 module		*	object
 
+struct		54  struct
+

src/core/f-extension.c

@@ -47,6 +47,7 @@ enum {
 	RXE_DATE,	// from upper section
 	RXE_OBJECT, // any object
 	RXE_TUPLE,  // 3-12 bytes tuple value
+	RXE_STRUCT,	// structure data and fields spec series
 	RXE_MAX
 };
 
@@ -121,6 +122,10 @@ x*/	RXIARG Value_To_RXI(REBVAL *val)
 		arg.tuple_len = VAL_TUPLE_LEN(val);
 		COPY_MEM(arg.tuple_bytes, VAL_TUPLE(val), MAX_TUPLE);
 		break;
+	case RXE_STRUCT:
+		arg.structure.data = VAL_STRUCT_DATA(val);
+		arg.structure.fields = VAL_STRUCT_FIELDS(val);
+		break;
 	case RXE_NULL:
 	default:
 		arg.int64 = 0;
@@ -176,6 +181,12 @@ x*/	void RXI_To_Value(REBVAL *val, RXIARG arg, REBCNT type)
 		VAL_TUPLE_LEN(val) = arg.tuple_len;
 		COPY_MEM(VAL_TUPLE(val), arg.tuple_bytes, MAX_TUPLE);
 		break;
+	case RXE_STRUCT:
+		//TODO: review!
+		// There is no room in RXIARG to pass the spec part of the struct!
+		VAL_STRUCT_DATA(val) = arg.structure.data;
+		VAL_STRUCT_FIELDS(val) = arg.structure.fields;
+		break;
 	case RXE_NULL:
 		VAL_INT64(val) = 0;
 		break;

src/include/reb-ext.h

@@ -97,6 +97,11 @@ typedef union rxi_arg_val {
 		REBYTE tuple_len;
 		REBYTE tuple_bytes[MAX_TUPLE];
 	};
+	struct {
+		REBSER *data;
+		REBSER *fields;
+	} structure;
+
 } RXIARG;
 
 // For direct access to arg array:

src/os/host-ext-test.c

@@ -89,6 +89,7 @@ char *RX_Spec =
 
 	"a: b: c: h: x: none\n"
 	"i: make image! 2x2\n"
+	"s: #[struct! [r [uint8!]]]\n"
 	"xtest: does [\n"
 		"foreach blk [\n"
 			"[x: hob1 #{0102}]"
@@ -124,6 +125,9 @@ char *RX_Spec =
 			"[echo i]\n"
 			"[probe i probe echo i]\n"
 			"[loop 1 [probe echo i]]\n"
+
+			// https://github.com/Oldes/Rebol-issues/issues/2536
+			"[same? s probe echo s]\n"
 		"][\n"
 			"print [{^/^[[7mtest:^[[0m^[[1;32m} mold blk {^[[0m}]\n"
 			//"replace {x} {x} {y}\n"