[whatwg] API for encoding/decoding ArrayBuffers into text

Joshua Bell jsbell at chromium.org
Mon Mar 26 14:49:02 PDT 2012

On Mon, Mar 26, 2012 at 2:42 PM, Anne van Kesteren <annevk at opera.com> wrote:

> On Mon, 26 Mar 2012 17:56:41 +0100, Joshua Bell <jsbell at chromium.org>
> wrote:
>> Bikeshed: The |continues| term doesn't completely thrill me; it's clear
>> in context, but not necessarily what someone might go searching for.
>> {eof:true} would be lovely except we want the default to be yes-EOF but a
>> falsy JS value. |noEOF| ?
> Peter Beverloo suggests "stream" on IRC. I like it.


> Opinions on one object type (Encoding) vs. two (Encoder, Decoder) ?
> Two seems cleaner.

I've gone ahead and updated the wiki/draft:

This includes:

* TextEncoder / TextDecoder objects, with |encode| and |decode| methods
that take option dicts
* A |stream| option, per the above
* A |nullTerminator| option eliminates the need for a stringLength method
(hasta la vista, baby!)
* |encodedLength| method is dropped since you can't in-place encode anyway
* decoding errors yield fallback code points by default, but setting a
|fatal| option cause a DOMException to be thrown instead
* specified exceptions as DOMException of type "EncodingError", as a

New issues resulting from this refactor:

* You can change the options (stream, nullTerminator, fatal) midway through
decoding a stream. This would be silly to do, but as written I don't think
this makes the implementation more difficult. Alternately, the non-stream
options could be set on the TextDecoder object itself.

* BOM handling needs to be resolved. The Encoding spec makes the encoding
label secondary to the BOM. With this API it's unclear if that should be
the case. Options include having a mismatching BOM throw, treating a
mismatching BOM as a decoding error (i.e. fallback or throw, depending on
options), or allow the BOM to actually switch the decoder used for this
"stream" - possibly if-and-only-if the default encoding was specified.

I've also partially updated the JS "polyfill" proof-of-concept
implementation, tests, and examples as well, but it does not implement
streaming yet (i.e. a "stream" option is ignored, state is always lost); I
need to do a tiny bit more refactoring first.

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