| Re: signed int64 pack/unpack [message #184595 is a reply to message #184594] |
Sun, 12 January 2014 16:00   |
Christoph Michael Bec
Messages: 207
Registered: June 2013
Karma:
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Senior Member |
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Jerry Stuckle wrote:
> On 1/12/2014 7:37 AM, Ben Bacarisse wrote:
>> 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?
>>
>
> You can argue, or you can answer our questions and get help.
>
> I see you've already got the answers and all you want to do is argue.
> Sorry I wasted my time and the network's bandwidth trying to help you.
Jerry, please note that Ben, to whom you've replied, is not the OP. :)
--
Christoph M. Becker
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