On 30.3.2012 15:21, Glenn Maynard wrote:
2012/3/29 Bronislav Klučka <[email protected]
<mailto:[email protected]>>
If I understand you, you find it problematic that by using weak
ref, URL would for some time reference actual Blob and other time
it would not?
The problem is that the following code might or might not work,
depending on the behavior of the browser's GC:
url = createObjectURL(blob);
blob = null;
setTimeout(function() { img.src = url; }, 0);
If the timer executes before GC collects the blob, this works, because
the URL is still valid. Otherwise, it fails, because--since the Blob
no longer exists--the URL is no longer valid.
--
Glenn Maynard
That should not be problematic; yes, GC may actually free that blob
allocated memory later than that timeout function triggers, but there is
explicit release of that blob (blob = null), so this must fail (memory
might be allocated by blob data, but that variable should be out). But
following may cause the same issue
var url = createObjectUrl(new Blob(['hello']));
setTimeout(function() { img.src = url; }, 0);
and even this in some aggressive GC implementation
img.src = createObjectUrl(new Blob(['hello']));
//since nothing references this blob, it could be destroyed right after
function ends, but before assigning result,
// thou GC works most likely in some application idle state not to delay
application process, theoretically this
// applies as well, since the functionality of GS is not specified =
implementation specific
Thou I could live with such issue, I see the problem (from others
programmers perspective and from specification perspective)... there's
no light at the end of this tunnel...
Either carefully treat weak refs, or have one time ULRs with
dereferencing and concurrency issues, or explicit URL release one might
forget..
Brona
