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Re: What happens if input ArrayBufferView changes during a WebCrypto operation ?

From: Harry Halpin <hhalpin@w3.org>
Date: Thu, 07 Mar 2013 14:48:15 +0100
Message-ID: <51389A9F.6000105@w3.org>
To: Mark Watson <watsonm@netflix.com>
CC: Ryan Sleevi <sleevi@google.com>, "public-webcrypto@w3.org Group" <public-webcrypto@w3.org>
On 03/06/2013 09:02 PM, Mark Watson wrote:
> On Mar 6, 2013, at 11:41 AM, Ryan Sleevi wrote:
>> On Wed, Mar 6, 2013 at 11:33 AM, Mark Watson <watsonm@netflix.com> wrote:
>>> Our operations are asynchronous. We pass in ArrayBufferView objects. What is the expected behavior if the application changes the ArrayBufferView before the WebCrypto operation completes ?
>>> If the expectation is that the operation completes normally on the input data as it was when the call was made, then the UA either needs to make a copy of the data when the call is first made or do some fancy lazy copy-on-write thing to ensure the web crypto operation retains access to the original data.
>> Correct. That is what I was trying to express through the description
>> of pending data, but I recognize this needs work, and have been
>> working on rewriting this.
>>> Alternatively, we may say that the behavior is undefined if you modify the ArrayBuffer that you pass in.
>> If there is anything I have learned from C/C++, it's that undefined
>> behaviour is the root of all error.
>>> Are there other async web APIs that accept ArrayBufferView objects that have established a precedent for this ?
>>> ůMark
>> We can force it to be ArrayBuffer, to make it explicit there's a copy,
>> but the intent of using ABV was to give greater implementation
>> flexibility in optimization, while also allowing easier use for
>> developers.
> Ok. Are you aware of anywhere else in the web platform where this problem exists and what solution they've chosen ?

Very good question. One option brought up to be to to cast it to an 
immutable Blob.

The official advice is to bring it up on public-script-coord@w3.org as 
this may effect how other WGs deal with the question - if they haven't 
already dealt with it.


> ůMark
Received on Thursday, 7 March 2013 13:48:29 UTC

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