Rework external string free operation (#4690)

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

docs/02.API-REFERENCE.md

@@ -769,6 +769,34 @@ typedef void (*jerry_object_native_free_callback_t) (void *native_p, struct jerr
 
 - [jerry_object_native_info_t](#jerry_object_native_info_t)
 
+## jerry_external_string_free_callback_t
+
+**Summary**
+
+Free callback for external strings. See
+[jerry_string_set_external_string_free_callback](#jerry_string_set_external_string_free_callback)
+for more information.
+
+**Prototype**
+
+```c
+typedef void (*jerry_external_string_free_callback_t) (jerry_char_t *string_p,
+                                                       jerry_size_t string_size,
+                                                       void *user_p);
+```
+
+- `string_p` - extrenal string pointer
+- `string_size` - size of external string
+- `user_p` - pointer passed when the external string is created
+
+*New in version [[NEXT_RELEASE]]*.
+
+**See also**
+
+- [jerry_string_set_external_string_free_callback](#jerry_string_set_external_string_free_callback)
+- [jerry_create_external_string](#jerry_create_external_string)
+- [jerry_create_external_string_sz](#jerry_create_external_string_sz)
+
 ## jerry_error_object_created_callback_t
 
 **Summary**
@@ -4195,6 +4223,70 @@ jerry_substring_to_utf8_char_buffer (const jerry_value_t value,
 - [jerry_is_valid_utf8_string](#jerry_is_valid_utf8_string)
 
 
+# jerry_string_set_external_string_free_callback
+
+**Summary**
+
+Sets the global callback which is called when the string data of an external
+string is no longer used. It is recommended to set this function before the
+first external string is created.
+
+*Note*:
+  - When the callback is NULL, no function is called when an external string is freed.
+  - In some cases (e.g. when the string is also a magic string registered by
+    [jerry_register_magic_strings](#jerry_register_magic_strings)), the callback
+    is called when the string is created, not when it is released.
+
+**Prototype**
+
+```c
+void jerry_string_set_external_string_free_callback (jerry_external_string_free_callback_t callback_p);
+```
+
+- `callback_p` - callback which is called when an external string is freed.
+
+*New in version [[NEXT_RELEASE]]*.
+
+**Example**
+
+[doctest]: # ()
+
+```c
+#include "jerryscript.h"
+#include <stdio.h>
+
+static void
+external_string_free_callback (jerry_char_t *string_p, /**< string pointer */
+                               jerry_size_t string_size, /**< size of the string */
+                               void *user_p) /**< user pointer */
+{
+  printf ("External string is freed!\n");
+}
+
+int
+main (void)
+{
+  jerry_init (JERRY_INIT_EMPTY);
+
+  jerry_string_set_external_string_free_callback (external_string_free_callback);
+
+  const char *string_p = "This is a long external string, should not be duplicated!";
+  jerry_value_t external_string = jerry_create_external_string ((jerry_char_t *) string_p, NULL);
+  /* The external_string_free_callback is called. */
+  jerry_release_value (external_string);
+
+  jerry_cleanup ();
+  return 0;
+}
+```
+
+**See also**
+
+- [jerry_external_string_free_callback_t](#jerry_external_string_free_callback_t)
+- [jerry_create_external_string](#jerry_create_external_string)
+- [jerry_create_external_string_sz](#jerry_create_external_string_sz)
+
+
 # Functions for array object values
 
 ## jerry_get_array_length
@@ -7293,24 +7385,25 @@ Create an external string from a valid CESU8 string. The string buffer passed to
 should not be modified until the free callback is called. This function can be used to avoid
 the duplication of large strings.
 
-*Note*: Returned value must be freed with [jerry_release_value](#jerry_release_value) when it
-is no longer needed.
+*Note*:
+ - The free callback can be set by [jerry_string_set_external_string_free_callback](#jerry_string_set_external_string_free_callback)
+ - Returned value must be freed with [jerry_release_value](#jerry_release_value)
+   when it is no longer needed.
 
 **Prototype**
 
 ```c
 jerry_value_t
-jerry_create_external_string (const jerry_char_t *str_p,
-                              jerry_value_free_callback_t free_cb)
+jerry_create_external_string (const jerry_char_t *str_p, void *user_p);
 ```
 
 - `str_p` - non-null pointer to string
-- `free_cb` - optional callback which is called right before the string is freed
+- `user_p` - user pointer passed to the callback when the string is freed
 - return value - value of the created string
 
 *New in version 2.4*.
 
-*Changed in version [[NEXT_RELEASE]]*: type of `free_cb` has been changed.
+*Changed in version [[NEXT_RELEASE]]*: `free_cb` is replaced by `user_p`.
 
 **Example**
 
@@ -7330,6 +7423,7 @@ jerry_create_external_string (const jerry_char_t *str_p,
 
 - [jerry_is_valid_cesu8_string](#jerry_is_valid_cesu8_string)
 - [jerry_create_external_string_sz](#jerry_create_external_string_sz)
+- [jerry_string_set_external_string_free_callback](#jerry_string_set_external_string_free_callback)
 
 
 ## jerry_create_external_string_sz
@@ -7340,8 +7434,10 @@ Create an external string from a valid CESU8 string. The string buffer passed to
 should not be modified until the free callback is called. This function can be used to avoid
 the duplication of large strings.
 
-*Note*: Returned value must be freed with [jerry_release_value](#jerry_release_value) when it
-is no longer needed.
+*Note*:
+ - The free callback can be set by [jerry_string_set_external_string_free_callback](#jerry_string_set_external_string_free_callback)
+ - Returned value must be freed with [jerry_release_value](#jerry_release_value)
+   when it is no longer needed.
 
 **Prototype**
 
@@ -7349,17 +7445,17 @@ is no longer needed.
 jerry_value_t
 jerry_create_external_string_sz (const jerry_char_t *str_p,
                                  jerry_size_t str_size,
-                                 jerry_value_free_callback_t free_cb)
+                                 void *user_p);
 ```
 
 - `str_p` - non-null pointer to string
 - `str_size` - size of the string
-- `free_cb` - optional callback which is called right before the string is freed
+- `user_p` - user pointer passed to the callback when the string is freed
 - return value - value of the created string
 
 *New in version 2.4*.
 
-*Changed in version [[NEXT_RELEASE]]*: type of `free_cb` has been changed.
+*Changed in version [[NEXT_RELEASE]]*: `free_cb` is replaced by `user_p`.
 
 **Example**
 
@@ -7381,6 +7477,7 @@ jerry_create_external_string_sz (const jerry_char_t *str_p,
 
 - [jerry_is_valid_cesu8_string](#jerry_is_valid_cesu8_string)
 - [jerry_create_external_string](#jerry_create_external_string)
+- [jerry_string_set_external_string_free_callback](#jerry_string_set_external_string_free_callback)
 
 
 ## jerry_create_symbol

jerry-core/api/jerry.c

@@ -2700,9 +2700,9 @@ jerry_create_string_sz (const jerry_char_t *str_p, /**< pointer to string */
  */
 jerry_value_t
 jerry_create_external_string (const jerry_char_t *str_p, /**< pointer to string */
-                              jerry_value_free_callback_t free_cb) /**< free callback */
+                              void *user_p) /**< user pointer passed to the callback when the string is freed */
 {
-  return jerry_create_external_string_sz (str_p, lit_zt_utf8_string_size ((lit_utf8_byte_t *) str_p), free_cb);
+  return jerry_create_external_string_sz (str_p, lit_zt_utf8_string_size ((lit_utf8_byte_t *) str_p), user_p);
 } /* jerry_create_external_string */
 
 /**
@@ -2716,13 +2716,13 @@ jerry_create_external_string (const jerry_char_t *str_p, /**< pointer to string
 jerry_value_t
 jerry_create_external_string_sz (const jerry_char_t *str_p, /**< pointer to string */
                                  jerry_size_t str_size, /**< string size */
-                                 jerry_value_free_callback_t free_cb) /**< free callback */
+                                 void *user_p) /**< user pointer passed to the callback when the string is freed */
 {
   jerry_assert_api_available ();
 
   ecma_string_t *ecma_str_p = ecma_new_ecma_external_string_from_cesu8 ((lit_utf8_byte_t *) str_p,
                                                                         (lit_utf8_size_t) str_size,
-                                                                        free_cb);
+                                                                        user_p);
   return ecma_make_string_value (ecma_str_p);
 } /* jerry_create_external_string_sz */
 
@@ -3107,6 +3107,16 @@ jerry_substring_to_utf8_char_buffer (const jerry_value_t value, /**< input strin
                                              buffer_size);
 } /* jerry_substring_to_utf8_char_buffer */
 
+/**
+ * Sets the global callback which is called when an external string is freed.
+ */
+void
+jerry_string_set_external_string_free_callback (jerry_external_string_free_callback_t callback_p) /**< free
+                                                                                                   *   callback */
+{
+  JERRY_CONTEXT (external_string_free_callback_p) = callback_p;
+} /* jerry_string_set_external_string_free_callback */
+
 /**
  * Checks whether the object or it's prototype objects have the given property.
  *

jerry-core/ecma/base/ecma-globals.h

@@ -1804,8 +1804,8 @@ typedef struct
  */
 typedef struct
 {
-  ecma_long_string_t header;
-  jerry_value_free_callback_t free_cb; /**< free callback */
+  ecma_long_string_t header; /**< long string header */
+  void *user_p; /**< user pointer passed to the callback when the string is freed */
 } ecma_external_string_t;
 
 /**

jerry-core/ecma/base/ecma-helpers-string.c

@@ -19,6 +19,7 @@
 #include "ecma-gc.h"
 #include "ecma-globals.h"
 #include "ecma-helpers.h"
+#include "jcontext.h"
 #include "jrt.h"
 #include "jrt-libc-includes.h"
 #include "lit-char-helpers.h"
@@ -455,7 +456,8 @@ ecma_new_ecma_string_from_utf8_converted_to_cesu8 (const lit_utf8_byte_t *string
 ecma_string_t *
 ecma_new_ecma_external_string_from_cesu8 (const lit_utf8_byte_t *string_p, /**< cesu-8 string */
                                           lit_utf8_size_t string_size, /**< string size */
-                                          jerry_value_free_callback_t free_cb) /**< free callback */
+                                          void *user_p) /**< user pointer passed to the callback
+                                                         *   when the string is freed */
 {
   JERRY_ASSERT (string_p != NULL || string_size == 0);
   JERRY_ASSERT (lit_is_valid_cesu8_string (string_p, string_size));
@@ -465,9 +467,11 @@ ecma_new_ecma_external_string_from_cesu8 (const lit_utf8_byte_t *string_p, /**<
     /* Normal strings are created for short strings. */
     ecma_string_t *string_desc_p = ecma_new_ecma_string_from_utf8 (string_p, string_size);
 
+    jerry_external_string_free_callback_t free_cb = JERRY_CONTEXT (external_string_free_callback_p);
+
     if (free_cb != NULL)
     {
-      free_cb ((void *) string_p);
+      free_cb ((lit_utf8_byte_t *) string_p, string_size, user_p);
     }
     return string_desc_p;
   }
@@ -476,9 +480,11 @@ ecma_new_ecma_external_string_from_cesu8 (const lit_utf8_byte_t *string_p, /**<
 
   if (string_desc_p != NULL)
   {
+    jerry_external_string_free_callback_t free_cb = JERRY_CONTEXT (external_string_free_callback_p);
+
     if (free_cb != NULL)
     {
-      free_cb ((void *) string_p);
+      free_cb ((lit_utf8_byte_t *) string_p, string_size, user_p);
     }
     return string_desc_p;
   }
@@ -491,7 +497,7 @@ ecma_new_ecma_external_string_from_cesu8 (const lit_utf8_byte_t *string_p, /**<
   long_string_p->string_p = string_p;
   long_string_p->size = string_size;
   long_string_p->length = lit_utf8_string_length (string_p, string_size);
-  external_string_p->free_cb = free_cb;
+  external_string_p->user_p = user_p;
 
   return (ecma_string_t *) external_string_p;
 } /* ecma_new_ecma_external_string_from_cesu8 */
@@ -961,10 +967,13 @@ ecma_destroy_ecma_string (ecma_string_t *string_p) /**< ecma-string */
       }
 
       ecma_external_string_t *external_string_p = (ecma_external_string_t *) string_p;
+      jerry_external_string_free_callback_t free_cb = JERRY_CONTEXT (external_string_free_callback_p);
 
-      if (external_string_p->free_cb != NULL)
+      if (free_cb != NULL)
       {
-        external_string_p->free_cb ((void *) external_string_p->header.string_p);
+        free_cb ((lit_utf8_byte_t *) external_string_p->header.string_p,
+                 external_string_p->header.size,
+                 external_string_p->user_p);
       }
 
       ecma_dealloc_external_string (external_string_p);

jerry-core/ecma/base/ecma-helpers.h

@@ -303,7 +303,7 @@ ecma_string_t *ecma_new_ecma_string_from_utf8 (const lit_utf8_byte_t *string_p,
 ecma_string_t *ecma_new_ecma_string_from_utf8_converted_to_cesu8 (const lit_utf8_byte_t *string_p,
                                                                   lit_utf8_size_t string_size);
 ecma_string_t *ecma_new_ecma_external_string_from_cesu8 (const lit_utf8_byte_t *string_p, lit_utf8_size_t string_size,
-                                                         jerry_value_free_callback_t free_cb);
+                                                         void *user_p);
 ecma_string_t *ecma_new_ecma_string_from_code_unit (ecma_char_t code_unit);
 #if JERRY_ESNEXT
 ecma_string_t *ecma_new_ecma_string_from_code_units (ecma_char_t first_code_unit, ecma_char_t second_code_unit);

jerry-core/include/jerryscript-core.h

@@ -135,6 +135,7 @@ jerry_size_t jerry_substring_to_utf8_char_buffer (const jerry_value_t value,
                                                   jerry_length_t end_pos,
                                                   jerry_char_t *buffer_p,
                                                   jerry_size_t buffer_size);
+void jerry_string_set_external_string_free_callback (jerry_external_string_free_callback_t callback_p);
 
 /**
  * Functions for array object values.
@@ -188,10 +189,8 @@ jerry_value_t jerry_create_string_from_utf8 (const jerry_char_t *str_p);
 jerry_value_t jerry_create_string_sz_from_utf8 (const jerry_char_t *str_p, jerry_size_t str_size);
 jerry_value_t jerry_create_string (const jerry_char_t *str_p);
 jerry_value_t jerry_create_string_sz (const jerry_char_t *str_p, jerry_size_t str_size);
-jerry_value_t jerry_create_external_string (const jerry_char_t *str_p,
-                                            jerry_value_free_callback_t free_cb);
-jerry_value_t jerry_create_external_string_sz (const jerry_char_t *str_p, jerry_size_t str_size,
-                                               jerry_value_free_callback_t free_cb);
+jerry_value_t jerry_create_external_string (const jerry_char_t *str_p, void *user_p);
+jerry_value_t jerry_create_external_string_sz (const jerry_char_t *str_p, jerry_size_t str_size, void *user_p);
 jerry_value_t jerry_create_symbol (const jerry_value_t value);
 jerry_value_t jerry_create_bigint (const uint64_t *digits_p, uint32_t size, bool sign);
 jerry_value_t jerry_create_undefined (void);

jerry-core/include/jerryscript-types.h

@@ -291,6 +291,12 @@ struct jerry_object_native_info_t;
  */
 typedef void (*jerry_object_native_free_callback_t) (void *native_p, struct jerry_object_native_info_t *info_p);
 
+/**
+ * Free callback for external strings.
+ */
+typedef void (*jerry_external_string_free_callback_t) (jerry_char_t *string_p, jerry_size_t string_size,
+                                                       void *user_p);
+
 /**
  * Decorator callback for Error objects. The decorator can create
  * or update any properties of the newly created Error object.

jerry-core/jcontext/jcontext.h

@@ -158,6 +158,7 @@ struct jerry_context_t
 
   vm_frame_ctx_t *vm_top_context_p; /**< top (current) interpreter context */
   jerry_context_data_header_t *context_data_p; /**< linked list of user-provided context-specific pointers */
+  jerry_external_string_free_callback_t external_string_free_callback_p; /**< free callback for external strings */
   void *error_object_created_callback_user_p; /**< user pointer for error_object_update_callback_p */
   jerry_error_object_created_callback_t error_object_created_callback_p; /**< decorator callback for Error objects */
   size_t ecma_gc_objects_number; /**< number of currently allocated objects */

tests/unit-core/test-external-string.c

@@ -25,25 +25,37 @@ static const char *external_3 = "x!?:s";
 static const char *external_4 = "Object property external string! Object property external string!";
 
 static void
-free_external1 (void *ptr)
+external_string_free_callback_1 (jerry_char_t *string_p, /**< string pointer */
+                                 jerry_size_t string_size, /**< size of the string */
+                                 void *user_p) /**< user pointer */
 {
-  TEST_ASSERT (ptr == external_1);
+  TEST_ASSERT ((const char *) string_p == external_1);
+  TEST_ASSERT (string_size == strlen (external_1));
+  TEST_ASSERT (user_p == NULL);
   free_count++;
-} /* free_external1 */
+} /* external_string_free_callback_1 */
 
 static void
-free_external2 (void *ptr)
+external_string_free_callback_2 (jerry_char_t *string_p, /**< string pointer */
+                                 jerry_size_t string_size, /**< size of the string */
+                                 void *user_p) /**< user pointer */
 {
-  TEST_ASSERT (ptr == external_2);
+  TEST_ASSERT ((const char *) string_p == external_2);
+  TEST_ASSERT (string_size == strlen (external_2));
+  TEST_ASSERT (user_p == (void *) &free_count);
   free_count++;
-} /* free_external2 */
+} /* external_string_free_callback_2 */
 
 static void
-free_external3 (void *ptr)
+external_string_free_callback_3 (jerry_char_t *string_p, /**< string pointer */
+                                 jerry_size_t string_size, /**< size of the string */
+                                 void *user_p) /**< user pointer */
 {
-  TEST_ASSERT (ptr == external_3);
+  TEST_ASSERT ((const char *) string_p == external_3);
+  TEST_ASSERT (string_size == strlen (external_3));
+  TEST_ASSERT (user_p == (void *) string_p);
   free_count++;
-} /* free_external3 */
+} /* external_string_free_callback_3 */
 
 int
 main (void)
@@ -53,38 +65,45 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Test external callback calls. */
-  jerry_value_t external_string = jerry_create_external_string ((jerry_char_t *) external_1, free_external1);
+  jerry_string_set_external_string_free_callback (external_string_free_callback_1);
+  jerry_value_t external_string = jerry_create_external_string ((jerry_char_t *) external_1, NULL);
   TEST_ASSERT (free_count == 0);
   jerry_release_value (external_string);
   TEST_ASSERT (free_count == 1);
 
+  jerry_string_set_external_string_free_callback (NULL);
   external_string = jerry_create_external_string ((jerry_char_t *) external_1, NULL);
   TEST_ASSERT (free_count == 1);
   jerry_release_value (external_string);
   TEST_ASSERT (free_count == 1);
 
-  external_string = jerry_create_external_string ((jerry_char_t *) external_2, free_external2);
+  jerry_string_set_external_string_free_callback (external_string_free_callback_2);
+  external_string = jerry_create_external_string ((jerry_char_t *) external_2, (void *) &free_count);
   TEST_ASSERT (free_count == 2);
   jerry_release_value (external_string);
   TEST_ASSERT (free_count == 2);
 
-  external_string = jerry_create_external_string ((jerry_char_t *) external_2, NULL);
+  jerry_string_set_external_string_free_callback (NULL);
+  external_string = jerry_create_external_string ((jerry_char_t *) external_2, (void *) &free_count);
   TEST_ASSERT (free_count == 2);
   jerry_release_value (external_string);
   TEST_ASSERT (free_count == 2);
 
-  external_string = jerry_create_external_string ((jerry_char_t *) external_3, free_external3);
+  jerry_string_set_external_string_free_callback (external_string_free_callback_3);
+  external_string = jerry_create_external_string ((jerry_char_t *) external_3, (void *) external_3);
   TEST_ASSERT (free_count == 3);
   jerry_release_value (external_string);
   TEST_ASSERT (free_count == 3);
 
-  external_string = jerry_create_external_string ((jerry_char_t *) external_3, NULL);
+  jerry_string_set_external_string_free_callback (NULL);
+  external_string = jerry_create_external_string ((jerry_char_t *) external_3, (void *) external_3);
   TEST_ASSERT (free_count == 3);
   jerry_release_value (external_string);
   TEST_ASSERT (free_count == 3);
 
   /* Test string comparison. */
-  external_string = jerry_create_external_string ((jerry_char_t *) external_1, free_external1);
+  jerry_string_set_external_string_free_callback (external_string_free_callback_1);
+  external_string = jerry_create_external_string ((jerry_char_t *) external_1, NULL);
   jerry_value_t other_string = jerry_create_string ((jerry_char_t *) external_1);
 
   jerry_value_t result = jerry_binary_operation (JERRY_BIN_OP_STRICT_EQUAL, external_string, other_string);
@@ -103,7 +122,8 @@ main (void)
   jerry_release_value (other_string);
 
   /* Test getting string. */
-  external_string = jerry_create_external_string ((jerry_char_t *) external_1, free_external1);
+  jerry_string_set_external_string_free_callback (external_string_free_callback_1);
+  external_string = jerry_create_external_string ((jerry_char_t *) external_1, NULL);
   size_t length = strlen (external_1);
 
   TEST_ASSERT (jerry_value_is_string (external_string));
@@ -119,6 +139,7 @@ main (void)
   TEST_ASSERT (free_count == 5);
 
   /* Test property access. */
+  jerry_string_set_external_string_free_callback (NULL);
   external_string = jerry_create_external_string ((jerry_char_t *) external_4, NULL);
   other_string = jerry_create_string ((jerry_char_t *) external_4);