Re: Thoughts behind the Streams API ED

Le 07/11/2013 10:21, Takeshi Yoshino a écrit :
> On Thu, Nov 7, 2013 at 6:05 PM, Aymeric Vitte <vitteaymeric@gmail.com 
> <mailto:vitteaymeric@gmail.com>> wrote:
>
>     stop/resume:
>
>     Indeed as I mentioned this is related to WebCrypto Issue22 but I
>     don't think this is a unique case. Issue22 was closed because of
>     lack of proposals to solve it, apparently I was the only one to
>     care about it (but I saw recently some other messages that seem to
>     be related), and finally this would involve a public clone method
>     with associated security concerns.
>
>     But with Streams it could be different, the application will
>     internally clone the state of the operation probably eliminating
>     the security issues, as simple as that.
>
>     To describe simply the use case, let's take a progressive hash
>     computing 4 bytes by 4 bytes:
>
>     incoming stream: ABCDE bytes
>     hash operation: process ABCD, keep E for the next computation
>     incoming stream: FGHI bytes + STOP-EOF
>     hash operation: process EFGH, process STOP-EOF: clone the state of
>     the hash, close the operation: digest hash with I
>
>
> So, here, partial hash for ABCDEFGH is output

No, you get the digest for ABCDEFGHI and you get a cloned operation 
which will restart from ABCDEFGH

>
>     resume:
>     incoming stream: JKLF
>     hash operation (clone): process IJKL, keep F for next computation
>     etc...
>
>
> and if we close the stream here we'll get a hash for ABCDEFGHIJKLFPPP 
> (P is padding). Right?

If you close the stream here you get the digest for ABCDEFGHIJKLF

>     So you do not restart the operation as if it was the first time it
>     was receiving data, you just continue it from the state it was
>     when stop was received.
>
>     That's not so unusual to do this, it has been requested many times
>     in node.
>

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