Re: [xml-dev] I think XML tools should handle XML files up to 2^64bytes

[David Carlisle <d.p.carlisle@gmail.com>]

On Tue, 13 Nov 2018 at 13:32, Costello, Roger L. <costello@mitre.org> wrote:
>
> Hi Folks,
>
> I think XML tools (e.g., XML parsers, schema validators, XSLT processors) should handle XML files up to 2^64 bytes in size.
>
> 2^64 = 18,446,744,073,709,551,616 (20 digits)
>
> Why that number? Here's why:

None of the reasons given below appear to apply to XML though.

Firstly why count the size in bytes? The file size in bytes is rather
secondary to almost all the Unicode based processing
secondly what internal structures have you in mind that mean that you
ever need to reference a byte count as a
"single word on a 64-bit processor"?
You might internally index elements or attributes or nodes or
something and so the total number of such nodes might
need to be below some type-specific value, but why the file size?

Once files get above a certain size then you would hopefully be able
to process them in a streaming fashion and have no upper limit
on the total size of the document.


David

>
> The number 2^64 is:
>
> The number of distinct values representable in a single word on a 64-bit processor. Or, the number of values representable in a doubleword on a 32-bit processor. Or, the number of values representable in a quadword on a 16-bit processor, such as the original x86 processors.
>
> The range of a long variable in the Java and C# programming languages.
>
> The range of a Int64 or QWord variable in the Pascal programming language.
>
> The total number of IPv6 addresses generally given to a single LAN or subnet.
>
> Thoughts?
>
> https://www.quora.com/How-big-is-2-power-64
>
> /Roger
>
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