Re: Lazy Blob

[Charles Pritchard]

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

> On Wed, Aug 1, 2012 at 9:59 AM, Robin Berjon <ro...@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