| Re: signed int64 pack/unpack [message #184592 is a reply to message #184589] |
Sun, 12 January 2014 12:37   |
Ben Bacarisse
Messages: 82
Registered: November 2013
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Jerry Stuckle <jstucklex(at)attglobal(dot)net> writes:
> On 1/11/2014 10:11 PM, Ben Bacarisse wrote:
>> Jerry Stuckle <jstucklex(at)attglobal(dot)net> writes:
>>
>>> On 1/11/2014 9:42 PM, Ben Bacarisse wrote:
>>>> cameron7(at)gmail(dot)com writes:
>>>>
>>>> > I'm having a bit of trouble figuring out a straightforward way to
>>>> > "pack" / "unpack" a signed int64.
>>>> >
>>>> > I'm on a 64-bit machine, but the 'i' and 'I' are coming back with
>>>> > 4-byte length.
>>>>
>>>> There is no explicit format for 64-bit ints. The i/I formats are used
>>>> for a native "int" but that need not be 64 bits on a 64-bit machine.
>>>> The function is borrowed from Perl whose documentation says a bit more
>>>>
>>>> This 'integer' is _at_least_ 32 bits wide. Its exact size depends on
>>>> what a local C compiler calls 'int'.
>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>> On my 64-bit Linux machine, 'int' is 32 bits.
>>>
>>> On my 64 bit Linux system, 'int' is 64 bits. But then I have the 64
>>> bit PHP version (and 64 bit OS) loaded.
>>
>> Yes, me too.
>>
>>> What do you get when you do:
>>>
>>> <?php
>>> echo PHP_INT_MAX . "\n";
>>> ?>
>>
>> Same as you but I don't think that's relevant. PHP stores values
>> internally using a C long. I think the Perl document describes what's
>> really happening.
>
> It is totally relevant. You can't operate on 64 bit values if you
> don't have 64 bit support.
The Perl documentation seems to describe what's happening. The PHP
documentation leaves the nature of the integer of "machine dependent
size" unspecified so some clarification is helpful.
64 bit support may be necessary but it seems not to be sufficient. Many
64 systems leave C's "int" as 32 bits, so if pack is still doing what
the Perl version describes, it's at least an explanation of what's
happening.
> And this is PHP, not Perl. Things have changed a *lot* since the
> original versions were created. Much of the Perl documentation no
> longer applies to PHP (if it ever did).
I am sure that's true, but, other than the source, I don't think there
is much more to go on. What is your explanation of what's going on?
--
Ben.
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