Allow the JS objects to have more than one native pointer data (#2814)

Currently JS objects can only have one native pointer data which could be a limitation in special cases.
This patch allows to register multiple native infos, which can be accessed/associated with the corresponding `jerry_object_native_info_t`.

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

Author: rerobika

docs/02.API-REFERENCE.md

@@ -4756,97 +4756,197 @@ jerry_set_prototype (const jerry_value_t obj_val,
 
 **Summary**
 
-Get native pointer and its type information.
+Get native pointer by the given type information.
 The pointer and the type information are previously associated with the object by jerry_set_object_native_pointer.
 
-*Note*: It is recommended to ensure that the `out_native_info_p` value pointer
-        is equal to the native info pointer that is expected, before casting
-        and accessing the `out_native_pointer_p`.
-        An example of when this is important: external functions that expect
-        `this` to have a native pointer of a certain C type.
-        It is possible in JavaScript to change `this` at will – using `call()`,
-        `apply()` or `bind()`. Therefore, it is possible that the native pointer
-        of `this` is not of the expected C type. To handle this safely and
-        securely, one must always add type checks to make sure that the
-        `out_native_pointer_p` is of the expected type, before casting
-        and dereferencing `out_native_pointer_p`.
-
-*Note*: `out_native_pointer_p` and `out_native_info_p` can be NULL, and it means the
-        caller doesn't want to get the native_pointer or type information.
+*Note*: `out_native_pointer_p` can be NULL, and it means the
+        caller doesn't want to get the native_pointer.
 
 **Prototype**
 
 ```c
 bool
 jerry_get_object_native_pointer (const jerry_value_t obj_val,
                                  void **out_native_pointer_p,
-                                 const jerry_object_native_info_t **out_native_info_p)
+                                 const jerry_object_native_info_t *native_info_p)
 ```
 
 - `obj_val` - object value to get native pointer from.
 - `out_native_pointer_p` - native pointer (output parameter).
-- `out_native_info_p` - native pointer's type information (output parameter).
+- `native_info_p` - native pointer's type information.
 - return value
-  - true, if there is native pointer associated with the object
+  - true, if there is native pointer associated of the specified object with the given native type info
   - false, otherwise
 
 **Example**
 
+[doctest]: # ()
+
 ```c
-typedef struct {
-  int foo;
-  bool bar;
-} native_obj_t;
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "jerryscript.h"
 
-static void native_freecb (void *native_p)
+typedef struct
 {
-  ... // free the native pointer
+  char *data_p;
+  unsigned int length;
+} buffer_native_object_t;
+
+typedef struct
+{
+  int area;
+  int perimeter;
+} shape_native_object_t;
+
+#define SECRET_INFO ((void *) 42)
+
+static void
+buffer_native_freecb (void *native_p)
+{
+  char *data_p = ((buffer_native_object_t*)native_p)->data_p;
+
+  if (data_p != NULL)
+  {
+    free (data_p);
+  }
+
+  free (native_p);
+}
+
+static void
+shape_native_freecb (void *native_p)
+{
+  free (native_p);
+}
+
+static void
+destructor_freecb (void *native_p)
+{
+   printf("Note: the object has been freed\n");
 }
 
 // NOTE: The address (!) of type_info acts as a way to uniquely "identify" the
-// C type `native_obj_t *`.
-static const jerry_object_native_info_t native_obj_type_info =
+// C type `buffer_native_object_t *`.
+static const jerry_object_native_info_t buffer_obj_type_info =
 {
-  .free_cb = native_freecb
+  .free_cb = buffer_native_freecb
 };
 
-// Function creating JS object that is "backed" by a native_obj_t *:
+// NOTE: The address (!) of type_info acts as a way to uniquely "identify" the
+// C type `shape_native_object_t *`.
+static const jerry_object_native_info_t shape_obj_type_info =
 {
-  ...
+  .free_cb = shape_native_freecb
+};
 
-  // construct object and native_set value:
-  jerry_value_t object = ...;
-  native_obj_t *native_obj = malloc(sizeof(*native_obj));
-  jerry_set_object_native_pointer (object, native_obj, &native_obj_type_info);
+// NOTE: The address (!) of type_info is the unique "identifier"
+static const jerry_object_native_info_t destructor_obj_type_info =
+{
+  .free_cb = destructor_freecb
+};
 
-  ...
+static void
+print_buffer (char *data_p,
+              unsigned int length)
+{
+  for (unsigned int i = 0; i < length; ++i)
+  {
+    printf("%c", data_p[i]);
+  }
+
+  printf("\n");
 }
 
-// Native method, `this` is expected to be "backed" by a native_obj_t *:
+static void
+do_stuff (jerry_value_t object)
 {
   void *native_p;
-  const jerry_object_native_info_t *type_p;
-  bool has_p = jerry_get_object_native_pointer (this_val, &native_p, &type_p);
+  bool has_p = jerry_get_object_native_pointer (object, &native_p, &buffer_obj_type_info);
+
+  if (!has_p)
+  {
+    // Process the error
+    return;
+  }
+
+  // It is safe to cast to buffer_native_object_t * and dereference the pointer:
+  buffer_native_object_t *buffer_p = (buffer_native_object_t *) native_p;
+  print_buffer (buffer_p->data_p, buffer_p->length); // Usage of buffer_p
+
+  bool need_shape_info = true; // implementation dependent
 
-  if (has_p)
+  if (need_shape_info)
   {
-    // The type_p pointer address itself is used to identify the type:
-    if (type_p == &native_obj_type_info)
+    has_p = jerry_get_object_native_pointer (object, &native_p, &shape_obj_type_info);
+
+    if (!has_p)
     {
-      // The type of this's native pointer matches what is expected.
-      // Only now is it safe to cast to native_obj_t * and dereference the
-      // pointer:
-      native_obj_t *native_obj = native_p;
-      native_obj->bar = ...; // Safe to access now!
+      // Process the error
+      return;
     }
-    else
+
+    // It is safe to cast to shape_native_object_t * and dereference the pointer:
+    shape_native_object_t *shape_p = (shape_native_object_t *) native_p;
+
+    printf("Area: %d\tPerimeter: %d\n", shape_p->area, shape_p->perimeter); // Usage of shape_p
+  }
+
+  bool need_secret_info = true; // implementation dependent
+
+  if (need_secret_info)
+  {
+    has_p = jerry_get_object_native_pointer (object, &native_p, NULL);
+
+    if (!has_p)
+    {
+      // Process the error
+      return;
+    }
+
+    printf("Secret: %d\n", (int)((uintptr_t) native_p)); // Usage of native_p
+
+    bool deleted = jerry_delete_object_native_pointer (object, NULL);
+
+    if (deleted)
     {
-      // The type of this's native pointer is NOT what we expected!
-      // We should not cast to native_obj_t * and dereference because it's unsafe.
-      // Handle the error here, for example throw an error.
+      printf("The secret is no longer available\n");
     }
   }
-  ...
+}
+
+int
+main (void)
+{
+  jerry_init (JERRY_INIT_EMPTY);
+
+  jerry_value_t object = jerry_create_object ();
+  buffer_native_object_t *buffer_p = (buffer_native_object_t *) malloc (sizeof (buffer_native_object_t));
+  buffer_p->length = 14;
+  buffer_p->data_p = (char *) malloc (buffer_p->length * sizeof (char));
+  memcpy (buffer_p->data_p, "My buffer data", buffer_p->length);
+  jerry_set_object_native_pointer (object, buffer_p, &buffer_obj_type_info);
+
+  shape_native_object_t *shape_p = (shape_native_object_t *) malloc (sizeof (shape_native_object_t));
+  shape_p->area = 6;
+  shape_p->perimeter = 12;
+  jerry_set_object_native_pointer (object, shape_p, &shape_obj_type_info);
+
+  // The native pointer can be NULL. This gives possibily to get notified via the native type info's
+  // free callback when the object has been freed by the GC.
+  jerry_set_object_native_pointer (object, NULL, &destructor_obj_type_info);
+
+  // The native type info can be NULL as well. In this case the registered property is simply freed
+  // when the object is freed by te GC.
+  jerry_set_object_native_pointer (object, SECRET_INFO, NULL);
+
+  do_stuff (object);
+
+  jerry_release_value (object);
+  jerry_cleanup ();
+
+  return 0;
 }
 ```
 
@@ -4897,6 +4997,40 @@ best-practice example.
 - [jerry_get_object_native_pointer](#jerry_get_object_native_pointer)
 - [jerry_object_native_info_t](#jerry_object_native_info_t)
 
+## jerry_delete_object_native_pointer
+
+**Summary**
+
+Delete the native pointer of the specified object associated with the given native type info.
+You can get them by calling jerry_get_object_native_pointer later.
+
+*Note*:
+ - If the specified object has no matching native pointer for the given native type info the operation has no effect.
+ - This operation cannot throw an exception.
+
+**Prototype**
+
+```c
+bool
+jerry_delete_object_native_pointer (const jerry_value_t obj_val,
+                                    const jerry_object_native_info_t *info_p)
+```
+
+- `obj_val` - object to delete native pointer from.
+- `info_p` - native pointer's type information.
+
+**Example**
+
+See [jerry_get_object_native_pointer](#jerry_get_object_native_pointer) for a
+best-practice example.
+
+**See also**
+
+- [jerry_create_object](#jerry_create_object)
+- [jerry_get_object_native_pointer](#jerry_get_object_native_pointer)
+- [jerry_get_object_native_pointer](#jerry_set_object_native_pointer)
+- [jerry_object_native_info_t](#jerry_object_native_info_t)
+
 
 ## jerry_foreach_object_property
 

jerry-core/api/jerry.c

@@ -2591,9 +2591,8 @@ jerry_objects_foreach_by_native_info (const jerry_object_native_info_t *native_i
   {
     if (!ecma_is_lexical_environment (iter_p))
     {
-      native_pointer_p = ecma_get_native_pointer_value (iter_p);
+      native_pointer_p = ecma_get_native_pointer_value (iter_p, (void *) native_info_p);
       if (native_pointer_p
-          && ((const jerry_object_native_info_t *) native_pointer_p->info_p) == native_info_p
           && !foreach_p (ecma_make_object_value (iter_p), native_pointer_p->data_p, user_data_p))
       {
         return true;
@@ -2605,20 +2604,19 @@ jerry_objects_foreach_by_native_info (const jerry_object_native_info_t *native_i
 } /* jerry_objects_foreach_by_native_info */
 
 /**
- * Get native pointer and its type information, associated with specified object.
+ * Get native pointer and its type information, associated with the given native type info.
  *
  * Note:
- *  If native pointer is present, its type information is returned
- *  in out_native_pointer_p and out_native_info_p.
+ *  If native pointer is present, its type information is returned in out_native_pointer_p
  *
  * @return true - if there is an associated pointer,
  *         false - otherwise
  */
 bool
 jerry_get_object_native_pointer (const jerry_value_t obj_val, /**< object to get native pointer from */
                                  void **out_native_pointer_p, /**< [out] native pointer */
-                                 const jerry_object_native_info_t **out_native_info_p) /**< [out] the type info
-                                                                                        *   of the native pointer */
+                                 const jerry_object_native_info_t *native_info_p) /**< the type info
+                                                                                   *   of the native pointer */
 {
   jerry_assert_api_available ();
 
@@ -2628,7 +2626,7 @@ jerry_get_object_native_pointer (const jerry_value_t obj_val, /**< object to get
   }
 
   ecma_native_pointer_t *native_pointer_p;
-  native_pointer_p = ecma_get_native_pointer_value (ecma_get_object_from_value (obj_val));
+  native_pointer_p = ecma_get_native_pointer_value (ecma_get_object_from_value (obj_val), (void *) native_info_p);
 
   if (native_pointer_p == NULL)
   {
@@ -2640,11 +2638,6 @@ jerry_get_object_native_pointer (const jerry_value_t obj_val, /**< object to get
     *out_native_pointer_p = native_pointer_p->data_p;
   }
 
-  if (out_native_info_p != NULL)
-  {
-    *out_native_info_p = (const jerry_object_native_info_t *) native_pointer_p->info_p;
-  }
-
   return true;
 } /* jerry_get_object_native_pointer */
 
@@ -2676,6 +2669,35 @@ jerry_set_object_native_pointer (const jerry_value_t obj_val, /**< object to set
   }
 } /* jerry_set_object_native_pointer */
 
+/**
+ * Delete the previously set native pointer by the native type info from the specified object.
+ *
+ * Note:
+ *      If the specified object has no matching native pointer for the given native type info
+ *      the function has no effect.
+ *
+ * Note:
+ *      This operation cannot throw an exception.
+ *
+ * @return true - if the native pointer has been deleted succesfully
+ *         false - otherwise
+ */
+bool
+jerry_delete_object_native_pointer (const jerry_value_t obj_val, /**< object to delete native pointer from */
+                                    const jerry_object_native_info_t *native_info_p) /**< object's native type info */
+{
+  jerry_assert_api_available ();
+
+  if (ecma_is_value_object (obj_val))
+  {
+    ecma_object_t *object_p = ecma_get_object_from_value (obj_val);
+
+    return ecma_delete_native_pointer_property (object_p, (void *) native_info_p);
+  }
+
+  return false;
+} /* jerry_delete_object_native_pointer */
+
 /**
  * Applies the given function to the every property in the object.
  *