On Wed, 28 Mar 2012 10:51:59 +0200, Jonas Sicking <[email protected]> wrote:
On Wed, Mar 28, 2012 at 2:17 AM, Anne van Kesteren <[email protected]>
wrote:
What does dereferencing mean exactly?
It means "initiating the load" or some such. Implementation-wise for
blob URLs it would likely mean going through the blob-url hash table
to find the underlying Blob object and start a read from it. So if the
URL is removed from the hash using revokeObjectURL this wouldn't
affect the load. Likewise for the FileSystem API it would mean that a
read from the blob has started and so any writes need to be queued
until after the read is finished.
xhr.open() resolves URLs currently and then xhr.send() will fetch the
URL.
Yup, this is the stuff that needs to be defined. In Gecko we actually
"dereference" the URL in xhr.open which means that the caller can call
revokeObjectURL after the call to xhr.open but before xhr.send. But
it's certainly possible to change this so that the URL is dereferenced
in xhr.send instead.
Given that the start of the fetch algorithm
http://www.whatwg.org/specs/web-apps/current-work/multipage/fetching-resources.html#fetch
is synchronous maybe dereferencing can be defined as part of that. The
change to XMLHttpRequest that would be needed then is to invoke fetch
before returning from send(). Not sure how well that would work for other
contexts such as <img> and 'background-image' though.
--
Anne van Kesteren
http://annevankesteren.nl/
