Make the underlying buffer of the ArrayBuffer accessible. (#2836)

JerryScript-DCO-1.0-Signed-off-by: László Langó llango.u-szeged@partner.samsung.com

docs/02.API-REFERENCE.md

@@ -6426,16 +6426,13 @@ jerry_arraybuffer_write (const jerry_value_t value,
 **Summary**
 
 The function allows access to the contents of the Array Buffer directly.
-Only allowed for Array Buffers which were created with
-[jerry_create_arraybuffer_external](#jerry_create_arraybuffer_external)
-function calls. In any other case this function will return `NULL`.
-
-After using the pointer the [jerry_release_value](#jerry_release_value)
-function must be called.
 
 **WARNING!** This operation is for expert use only! The programmer must
 ensure that the returned memory area is used correctly. That is
-there is no out of bounds reads or writes.
+there is no out of bounds reads or writes. The lifetime of the underlying
+data buffer is managed by the ArrayBuffer value. Make sure to acquire the
+value with [`jerry_acquire_value`](#jerry_acquire_value) if the data
+buffer is needed later.
 
 **Prototype**
 
@@ -6447,26 +6444,22 @@ jerry_get_arraybuffer_pointer (const jerry_value_t value);
 - `value` - Array Buffer object.
 - return value
   - pointer to the Array Buffer's data area.
-  - NULL if the `value` is not an Array Buffer object with external memory.
+  - NULL if the `value` is not an Array Buffer object.
 
 **Example**
 
 ```c
 {
-  jerry_value_t buffer;
-
-  // acquire buffer somewhere which was created by a jerry_create_array_buffer_external call.
+  // create the ArrayBuffer
+  jerry_value_t buffer = jerry_create_arraybuffer (16);
 
   uint8_t *const data = jerry_get_arraybuffer_pointer (buffer);
 
-  for (int i = 0; i < 22; i++)
+  for (int i = 0; i < 16; i++)
   {
     data[i] = (uint8_t) (i + 4);
   }
 
-  // required after jerry_get_arraybuffer_pointer call.
-  jerry_release_value (buffer);
-
   // use the Array Buffer
 
   // release buffer as it is not needed after this point