Everything

php

[RFC] Base convert changes

php.internals

Scott Dutton

7 years ago

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

Scott Dutton

7 years ago

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

Girgias

7 years ago

On Tue, 21 May 2019, 06:42 Scott Dutton, <scott@exussum.co.uk> wrote:

>
> 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
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php

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

Nikita Popov

7 years ago

On Sat, May 18, 2019 at 11:22 AM Scott Dutton <scott@exussum.co.uk> wrote:

> 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

Derick Rethans

7 years ago

On Thu, 23 May 2019, Nikita Popov wrote:

> On Sat, May 18, 2019 at 11:22 AM Scott Dutton <scott@exussum.co.uk> wrote:
>
> > 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
>
> 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

--
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

Scott Dutton

7 years ago

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


On 23.05.2019 17:32, Derick Rethans wrote:

Scott Dutton

7 years ago

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

Derick Rethans

7 years ago

On Tue, 11 Jun 2019, Scott Dutton wrote:

> 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,
or become my Patron: https://www.patreon.com/derickr
twitter: @derickr and @xdebug