mirror of https://github.com/svaarala/duktape.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
52 lines
1.5 KiB
52 lines
1.5 KiB
name: duk_get_heapptr
|
|
|
|
proto: |
|
|
void *duk_get_heapptr(duk_context *ctx, duk_idx_t idx);
|
|
|
|
stack: |
|
|
[ ... val! ... ]
|
|
|
|
summary: |
|
|
<p>Get a borrowed <code>void *</code> reference to a Duktape heap allocated
|
|
value (object, buffer, string) at <code>idx</code>. Return <code>NULL</code>
|
|
if the index is invalid or the target value is not heap allocated.
|
|
The returned pointer must not be interpreted or dereferenced, but
|
|
<code><a href="#duk_push_heapptr">duk_push_heapptr()</a></code> can be used
|
|
to push the original value into the value stack later.</p>
|
|
|
|
<p>The returned void pointer is only valid while the original value is
|
|
reachable from a garbage collection point of view. If this is not the case,
|
|
it is memory unsafe to use
|
|
<code><a href="#duk_push_heapptr">duk_push_heapptr()</a></code>.</p>
|
|
|
|
example: |
|
|
duk_context *new_ctx;
|
|
void *ptr;
|
|
|
|
duk_eval_string(ctx, "({ foo: 'bar' })");
|
|
ptr = duk_get_heapptr(ctx, -1);
|
|
|
|
/* The original value must remain reachable for Duktape up to a future
|
|
* duk_push_heapptr(). Here we just write it to the global object, but
|
|
* it could also be a value stack somewhere, a stash object, etc.
|
|
*/
|
|
duk_put_global_string(ctx, "ref");
|
|
|
|
/* Later, assuming the original value has been reachable all the way
|
|
* to here:
|
|
*/
|
|
|
|
duk_push_heapptr(ctx, ptr);
|
|
duk_get_prop_string(ctx, -1, "foo");
|
|
printf("obj.foo: %s\n", duk_safe_to_string(ctx, -1)); /* prints 'bar' */
|
|
|
|
tags:
|
|
- stack
|
|
- borrowed
|
|
|
|
seealso:
|
|
- duk_require_heapptr
|
|
- duk_push_heapptr
|
|
- duk_get_heapptr_default
|
|
|
|
introduced: 1.1.0
|
|
|