Req #68480 [Com]: unpack unsigned large number becoming negative
| From: | ignasimg at gmail dot com | Date: | Mon, 01 Dec 2014 00:49:52 +0000 |
| Subject: | Req #68480 [Com]: unpack unsigned large number becoming negative | ||
| References: | 1 | Groups: | php.bugs |
| Request: | Send a blank email to php-bugs+get-188860@lists.php.net to get a copy of this message | ||
Edit report at https://bugs.php.net/bug.php?id=68480&edit=1
ID: 68480
Comment by: ignasimg at gmail dot com
Reported by: ignasimg at gmail dot com
Summary: unpack unsigned large number becoming negative
Status: Wont fix
Type: Feature/Change Request
Package: *General Issues
Operating System: Irrelevant
PHP Version: Irrelevant
Block user comment: N
Private report: N
New Comment:
"so there's no way to return it as an unsigned integer unless the number gets returned as
a float" so do it!
The only problem you point out is the possible loss of precission, but afaik loss of precission only
occurs with fractional values and values that are much larger than the maximum integer.
And even if it was the case that some big integer value say X did loss precission when converting to
float. This precission would be lost aswell when you do:
$a = X;
because as said php would store it as a float.
Maybe I'm missing something but I really can't understand why it can't return a float
type.
Previous Comments:
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[2014-11-25 17:52:25] aharvey@php.net
PHP doesn't have an unsigned integer (or bigint) type, so there's no way to return it as
an unsigned integer unless the number gets returned as a float, which obviously risks losing
precision. (This is effectively what the "solution" does â on a 32 bit
architecture, that addition will cause $unpackedVal to be converted to a float.)
Closing, since this requires a language change (which then requires an RFC, a patch, et cetera).
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[2014-11-22 12:07:57] ignasimg at gmail dot com
Description:
------------
According to the documentation page about unpack:
http://php.net/manual/en/function.unpack.php
Caution
[...] If you unpack a large unsigned long and it is of the same size as PHP internally stored values
the result will be a negative number even though unsigned unpacking was specified.
My question (beside wtf?) is would it be so hard to specify inside the unpack function that if
unsigned was required make it become unsigned?
I mean... it might sound stupidly ridicoulous but why is there an unsigned format if it acts the
same as with signed?
There's even some funny solution on the same page comments:
if ($unpackedVal <0)
{
$unpackedVal += 4294967296;
}
which is platform dependent and probably inefficient.
But since I have no idea about the inner workings of PHP my question again is would it be so
difficult to make it behave properly?
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Edit this bug report at https://bugs.php.net/bug.php?id=68480&edit=1