lib: introduce new proto() ucode function

The proto() function allows getting and setting the prototype value of
array or object values, which is useful to build object instances.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

2 files changed, 67 insertions, 0 deletions

diff --git a/README.md b/README.md
index d09ff27..d6e6b25 100644
--- a/README.md
+++ b/README.md
@@ -1060,3 +1060,16 @@ Right now, any positive non-zero value will enable tracing while future
 implementation might provide different different verbosity levels or treat
 the level argument as bit mask to enable or disable individual debug
 elements.
+
+#### 6.54. `proto(val[, proto])`
+
+Get or set the prototype of the array or object value `val`.
+
+When invoked without a second argument, the function returns the current
+prototype of the value in `val` or `null` if there is no prototype or if
+the given value is neither an object, nor an array.
+
+When invoked with a second prototype argument, the given `proto` value is
+set as prototype on the array or object in `val`.
+
+Throws an exception if the given prototype value is not an object.
diff --git a/lib.c b/lib.c
index c8b50b6..ba49927 100644
--- a/lib.c
+++ b/lib.c
@@ -2328,6 +2328,59 @@ uc_trace(uc_vm *vm, size_t nargs)
 	return xjs_new_int64(prev_level);
 }
 
+static json_object *
+uc_proto(uc_vm *vm, size_t nargs)
+{
+	json_object *val = uc_get_arg(0);
+	json_object *proto = NULL;
+	uc_prototype *p, *ref;
+
+	if (nargs < 2) {
+		switch (uc_object_type(val)) {
+		case UC_OBJ_PROTOTYPE:
+			p = uc_object_as_prototype(val)->parent;
+
+			return p ? uc_value_get(p->header.jso) : NULL;
+
+		case UC_OBJ_RESSOURCE:
+			p = uc_ressource_prototype(val);
+
+			return p ? uc_value_get(p->header.jso) : NULL;
+
+		default:
+			return NULL;
+		}
+	}
+
+	proto = uc_get_arg(1);
+
+	switch (uc_object_type(proto)) {
+	case UC_OBJ_PROTOTYPE:
+		p = uc_object_as_prototype(proto);
+		break;
+
+	case UC_OBJ_RESSOURCE:
+		p = uc_ressource_prototype(proto);
+		break;
+
+	default:
+		switch (json_object_get_type(proto)) {
+		case json_type_object:
+			p = uc_protoref_new(proto, NULL);
+			break;
+
+		default:
+			uc_vm_raise_exception(vm, EXCEPTION_TYPE, "Passed value is neither a prototype, ressource or object");
+
+			return NULL;
+		}
+	}
+
+	ref = uc_protoref_new(val, p);
+
+	return ref ? uc_value_get(ref->header.jso) : NULL;
+}
+
 static const uc_cfunction_list functions[] = {
 	{ "chr",		uc_chr },
 	{ "delete",		uc_delete },
@@ -2376,6 +2429,7 @@ static const uc_cfunction_list functions[] = {
 	{ "warn",		uc_warn },
 	{ "system",		uc_system },
 	{ "trace",		uc_trace },
+	{ "proto",		uc_proto }
 };