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Re: Static JSON parser for embedded

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  Re: Static JSON parser for embedded Clifford Heath <no.spam@please.net> - 2019-06-06 09:48 +1000
    Re: Static JSON parser for embedded pozz <pozzugno@gmail.com> - 2019-06-06 09:54 +0200

#28654 — Re: Static JSON parser for embedded

On 6/6/19 12:44 am, pozz wrote:
>> So there is existing work, and no doubt community support for more.
>> You could do a lot worse than start with ASN1CC.
> 
> I eventually take a look at asn1scc and found a big limitation: it 
> doesn't support extensibility feature of ASN.1.

One more comment. You mention (in other messages) that JSON is difficult 
without using dynamic memory. ASN1CC is designed to avoid using dynamic 
memory (for the same reason; embedded system constraints), which is why 
it cannot implement arbitrary extensions. The best it could do is to 
skip unknown extensions. But in PER, items are not tagged or 
length-delimited, and skipping an extension requires at least a 
knowledge of how big it is.

Clifford Heath.

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#28656

Il 06/06/2019 01:48, Clifford Heath ha scritto:
> On 6/6/19 12:44 am, pozz wrote:
>>> So there is existing work, and no doubt community support for more.
>>> You could do a lot worse than start with ASN1CC.
>>
>> I eventually take a look at asn1scc and found a big limitation: it 
>> doesn't support extensibility feature of ASN.1.
> 
> One more comment. You mention (in other messages) that JSON is difficult 
> without using dynamic memory. ASN1CC is designed to avoid using dynamic 
> memory (for the same reason; embedded system constraints), which is why 
> it cannot implement arbitrary extensions. The best it could do is to 
> skip unknown extensions. 

Yes, many times this behaviour is good, instead of breaking at all the 
system.

> But in PER, items are not tagged or 
> length-delimited, and skipping an extension requires at least a 
> knowledge of how big it is.

Ok, PER can't be used to skip extended variables. However I can use BER. 
Why do asn1scc refuses to compile definitions file with extensions when 
BER is used?

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