Add JS_NewArrayFrom (#870)

Add a version of JS_NewArray that takes the initial elements as its
argument.

Change the OP_array_from bytecode handler to use it, to show that it
works.

Refs: #868

Author: bnoordhuis

quickjs.c

@@ -1284,6 +1284,7 @@ static JSValue *build_arg_list(JSContext *ctx, uint32_t *plen,
 static JSValue js_create_array(JSContext *ctx, int len, JSValue *tab);
 static bool js_get_fast_array(JSContext *ctx, JSValue obj,
                               JSValue **arrpp, uint32_t *countp);
+static int expand_fast_array(JSContext *ctx, JSObject *p, uint32_t new_len);
 static JSValue JS_CreateAsyncFromSyncIterator(JSContext *ctx,
                                               JSValue sync_iter);
 static void js_c_function_data_finalizer(JSRuntime *rt, JSValue val);
@@ -5043,6 +5044,28 @@ JSValue JS_NewArray(JSContext *ctx)
                                  JS_CLASS_ARRAY);
 }
 
+// note: takes ownership of |values|, unlike js_create_array
+JSValue JS_NewArrayFrom(JSContext *ctx, int count, const JSValue *values)
+{
+    JSObject *p;
+    JSValue obj;
+
+    obj = JS_NewArray(ctx);
+    if (JS_IsException(obj))
+        return JS_EXCEPTION;
+    if (count > 0) {
+        p = JS_VALUE_GET_OBJ(obj);
+        if (expand_fast_array(ctx, p, count)) {
+            JS_FreeValue(ctx, obj);
+            return JS_EXCEPTION;
+        }
+        p->u.array.count = count;
+        p->prop[0].u.value = js_int32(count);
+        memcpy(p->u.array.u.values, values, count * sizeof(*values));
+    }
+    return obj;
+}
+
 JSValue JS_NewObject(JSContext *ctx)
 {
     /* inline JS_NewObjectClass(ctx, JS_CLASS_OBJECT); */
@@ -15355,23 +15378,12 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValue func_obj,
             BREAK;
         CASE(OP_array_from):
             {
-                int i, ret;
-
                 call_argc = get_u16(pc);
                 pc += 2;
-                ret_val = JS_NewArray(ctx);
+                call_argv = sp - call_argc;
+                ret_val = JS_NewArrayFrom(ctx, call_argc, call_argv);
                 if (unlikely(JS_IsException(ret_val)))
                     goto exception;
-                call_argv = sp - call_argc;
-                for(i = 0; i < call_argc; i++) {
-                    ret = JS_DefinePropertyValue(ctx, ret_val, __JS_AtomFromUInt32(i), call_argv[i],
-                                                 JS_PROP_C_W_E | JS_PROP_THROW);
-                    call_argv[i] = JS_UNDEFINED;
-                    if (ret < 0) {
-                        JS_FreeValue(ctx, ret_val);
-                        goto exception;
-                    }
-                }
                 sp -= call_argc;
                 *sp++ = ret_val;
             }

quickjs.h

@@ -728,6 +728,9 @@ JS_EXTERN bool JS_IsRegExp(JSValue val);
 JS_EXTERN bool JS_IsMap(JSValue val);
 
 JS_EXTERN JSValue JS_NewArray(JSContext *ctx);
+// takes ownership of the values
+JS_EXTERN JSValue JS_NewArrayFrom(JSContext *ctx, int count,
+                                  const JSValue *values);
 JS_EXTERN int JS_IsArray(JSContext *ctx, JSValue val);
 
 JS_EXTERN JSValue JS_NewDate(JSContext *ctx, double epoch_ms);