Re: Lazy Blob

On Aug 1, 2012, at 8:44 AM, Glenn Maynard <glenn@zewt.org> wrote:

> On Wed, Aug 1, 2012 at 9:59 AM, Robin Berjon <robin@berjon.com> wrote:
> var bb = new BlobBuilder()
> ,   blob = bb.getBlobFromURL("http://specifiction.com/kitten.png", "GET", { Authorization: "Basic DEADBEEF" });
> 
> Everything is the same as the previous version but the method and some headers can be set by enumerating the Object. I *think* that those are all that would ever be needed.
> 
> We already have an API to allow scripts to make network requests: XHR.  Please don't create a new API that will end up duplicating all of that.  However this might be done, it should hang off of XHR.
> 
> Ideally, a new responseType could be added to XHR which operates like "blob", except instead of reading the whole resource, it just performs a HEAD to retrieve the response length and immediately returns the Blob, which can be read to perform further Content-Range reads.  This sits relatively cleanly within the XHR API.  It also has nice security properties, as if you send that Blob somewhere else--possibly to a different origin--it can do nothing with the Blob but read it as it was given.
> 
> The trouble is chunked responses, where the length of the resource isn't known in advance, since Blobs have a static length and aren't designed for streaming.


The "HEAD" request seems a little like a FileEntry for use with FileReader.

Something similar (very similar) is done for http+fuse on several platforms.

It's quite useful for working with large archives such as PDF or ZIP.


-Charles