# [RFC] Base convert changes

- Thread: https://externals.io/message/105740
- Original archive: https://news-web.php.net/php.internals/105740
- Started by Scott Dutton on 2019-05-18T09:21:39+00:00
- Messages: 8
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## #105740 — Scott Dutton — 2019-05-18T09:21:39+00:00

URL: https://externals.io/message/105740#105740

Hi all

I have made some changes to base_convert which I feel would be more 
consistent with the current PHP (warning when there are errors, and not 
just returning the best value it can)

The RFC has some examples of what will change.

Currently the code works but a lot of tests fail due to extreme range's 
(also mentioned in the RFC)

If this passes I will fix the effected tests and add some more covering 
the new behavior.

https://wiki.php.net/rfc/base_convert_improvements

Let me know your thoughts

Thanks

Scott

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## #105768 — Scott Dutton — 2019-05-21T05:42:32+00:00

URL: https://externals.io/message/105740#105768

Not sure if I can add and example to the RFC at this point, but I came 
across another example of this recently.

https://gist.github.com/iansltx/4820b02ab276c3306314daaa41573445#file-getlines-php-L9

     // `bindec()` was doing weird things, hence converting through hex 
first
     // sttrev() to match endian-ness to expectations; zip file values 
are little-endian
     $compressedSize = hexdec(bin2hex(strrev(fread($stream, 4)))); // 
compressed size

bindec was returning 0 without warning, as it was passed binary data 
not a binary string. No warning bin2hex actually does the correct 
translation.

a warning here would have at least indicated there was something wrong 
with the input it was being passed instead of just 0.

Thanks

Scott

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## #105771 — G. P. B. — 2019-05-21T08:43:34+00:00

URL: https://externals.io/message/105740#105771

>
> Not sure if I can add and example to the RFC at this point, but I came
> across another example of this recently.
>
>
> https://gist.github.com/iansltx/4820b02ab276c3306314daaa41573445#file-getlines-php-L9
>
>      // `bindec()` was doing weird things, hence converting through hex
> first
>      // sttrev() to match endian-ness to expectations; zip file values
> are little-endian
>      $compressedSize = hexdec(bin2hex(strrev(fread($stream, 4)))); //
> compressed size
>
> bindec was returning 0 without warning, as it was passed binary data
> not a binary string. No warning bin2hex actually does the correct
> translation.
>
> a warning here would have at least indicated there was something wrong
> with the input it was being passed instead of just 0.
>
> Thanks
>
> Scott
>
> --
> 
> 


Until the RFC is in voting you can still make amendments to it.
So feel free to add these functions/examples to the RFC.

Best regards

George Peter Banyard

---

## #105779 — Nikita Popov — 2019-05-23T12:36:21+00:00

URL: https://externals.io/message/105740#105779

> Hi all
>
> I have made some changes to base_convert which I feel would be more
> consistent with the current PHP (warning when there are errors, and not
> just returning the best value it can)
>
> The RFC has some examples of what will change.
>
> Currently the code works but a lot of tests fail due to extreme range's
> (also mentioned in the RFC)
>
> If this passes I will fix the effected tests and add some more covering
> the new behavior.
>
> https://wiki.php.net/rfc/base_convert_improvements
>
> Let me know your thoughts
>
> Thanks
>
> Scott
>

Hi Scott,

I definitely agree with the part of the RFC that warns on garbage
characters in the string. I'm not so sure about the changes in sign
handling. The problem I see is that certain bases (in particular hex) are
pretty much never used with an explicit sign, instead they are understood
to be in two's complement representation.

For example, code like this will currently work:

var_dump(dechex(0xffffffff00000000));
// string(16) "ffffffff00000000"

While after your change it will result in "-100000000", which for hex
numbers is rather unexpected. (This example is somewhat non-great because
there is a loss of accuracy for 64bit numbers represented as doubles -- the
same examples with 32-bit integers on 32-bit systems would be fully
reliable.)

Nikita

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## #105780 — Derick Rethans — 2019-05-23T16:32:55+00:00

URL: https://externals.io/message/105740#105780

> 
> 
> > […]
> 
> I definitely agree with the part of the RFC that warns on garbage
> characters in the string. I'm not so sure about the changes in sign
> handling. The problem I see is that certain bases (in particular hex) are
> pretty much never used with an explicit sign, instead they are understood
> to be in two's complement representation.
> 
> For example, code like this will currently work:
> 
> var_dump(dechex(0xffffffff00000000));
> // string(16) "ffffffff00000000"

I concur with Nikita here. I don't think you should change the sign 
handling. I think this is something that actually use in real life 
projects.

cheers,
Derick

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---

## #105783 — Scott Dutton — 2019-05-23T20:32:21+00:00

URL: https://externals.io/message/105740#105783

Hi Nikita, Derick

Thanks for your time looking at this. Not sure if this will sway you 
either way, Other programming languages do handle negatives correctly, 
for example (i can add this to the RFC if that helps)

Javascript - https://jsfiddle.net/c16b4usp/
Python - https://repl.it/repls/OliveBlushingModem
Go - https://play.golang.org/p/aLWg15c00Fy

Its interesting that Javascript handles the large value example 
correctly, the other two error. There is likely a way to handle 
negatives in a way which also handles the large numbers though I'm not 
sure what that would be, I am happy to take any suggestions or look 
further into the engine to see how this could be done.

I was planning on two votes, one for the invalid char changes and one 
for the negative changes. Either way the documentation should be changes 
to make it clear that either negative numbers or extremely large values 
will not return the expected value (unless there is a way to avoid both 
of these?)

Happy to make any changes to the implementation as I said in the PR, my 
C is quite rusty

Thanks

Scott



> 
>
> > […]
>
> I concur with Nikita here. I don't think you should change the sign
> handling. I think this is something that actually use in real life
> projects.
>
> cheers,
> Derick
>
> --
> https://derickrethans.nl | https://xdebug.org | https://dram.io
> Like Xdebug? Consider a donation: https://xdebug.org/donate.php,
> or become my Patron: https://www.patreon.com/derickr
> twitter: @derickr and @xdebug

---

## #105874 — Scott Dutton — 2019-06-11T19:02:41+00:00

URL: https://externals.io/message/105740#105874

Hi all,

I plan to put this to vote early next week with the two options

One vote for the invalid char deprecation for php7.4 and Exception in 
PHP8

One vote for negative numbers PHP8 only - due to BC concerns

Thanks

Scott

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## #105879 — Derick Rethans — 2019-06-12T14:52:57+00:00

URL: https://externals.io/message/105740#105879

> Hi all,
> 
> I plan to put this to vote early next week with the two options
> 
> One vote for the invalid char deprecation for php7.4 and Exception in PHP8
> 
> One vote for negative numbers PHP8 only - due to BC concerns

Could you update the relevent section(s) in the RFC? → 
https://wiki.php.net/rfc/base_convert_improvements#proposed_voting_choices

You might be able to remove some other sections that have no content 
besides the templated content as well.

cheers,
Derick

-- 
https://derickrethans.nl | https://xdebug.org | https://dram.io
Like Xdebug? Consider a donation: https://xdebug.org/donate.php,
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