in reply to Re^3: Storable- long integer size
in thread Storable- long integer size

An IV has not only length shown by ivsize, but also an order, as shown by byteorder. Both have to match for Storable to work

Yes, I knew that ivsize and byteorder would have to match for Storable to work, but I was unsure whether ivtype also had to match.

I take it that ivtype does *not* have to match.
Thanks !!

Cheers,
Rob

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Re^5: Storable- long integer size
by syphilis (Archbishop) on Oct 22, 2015 at 06:25 UTC
    I take it that ivtype does *not* have to match.

    That may be so, but it seems that longsize also has to match - because that's apparently what Storable stipulates(and for no good reason, AFAICT).
    On an Ubuntu box using a perl whose ivsize was 8 and byteorder was 12345678, I ran: 
    use strict;
use warnings;
use Storable;

my $val = 12345678;
my $file = 'store.ubu';

store (\$val, $file);

my $valref = retrieve($file);
print "$val $$valref\n";

    [download]
    Then I copied (via scp) the generated 'store.ubu' over to a Windows box. (The file does not get changed by the transfer.) Using a compatible Windows perl (ivsize of 8 and byteorder of 12345678) I ran this script to retrieve the value: 
    use strict;
use warnings;
use Storable;

my $file = 'store.ubu';

print "Retrieving $file\n";

my $r = retrieve($file);
print $$r, "\n";

    [download]
    It output: 
    Retrieving store.ubu
Long integer size is not compatible at C:/_64/perl522_492/lib/Storable
+.pm line 383, at retrieve.pl line 9.

    [download]
    I then went into the Storable-2.51 source and changed line 6037 of Storable.xs from: 
    if ((int) *current++ != sizeof(long))
to
if ((int) *current++ != sizeof(IV))

    [download]
    (That's the condition that terminates the script and emits the "Long integer size is not compatible" error message.)
    I then rebuilt and installed this modified Storable-2.51 and re-ran the retrieval script. This time I got exactly what (I think) I should have been getting all along: 
    Retrieving store.ubu
12345678

    [download]
    Storable is actively disabling retrieval when it's not necessary to do that.
    Is that the way it's supposed to behave ?
    Why is it effectively insisting that longsize be the same - especially given that longsize typically differs between linux and windows ?

    Cheers,
    Rob
[reply]
[d/l]
[select]
      Why is it effectively insisting that longsize be the same - especially given that longsize typically differs between linux and windows ?

      My guess is that its because no one who appreciates the difference between LP64 & LLP64 programming models has really looked at the code since it was ported to 64-bit.

      The code simply makes no attempt at differentiation. The magic_check function from Storable.xs :

      /*
 * magic_check
 *
 * Make sure the stored data we're trying to retrieve has been produce
+d
 * on an ILP compatible system with the same byteorder. It croaks out 
+in
 * case an error is detected. [ILP = integer-long-pointer sizes]
 * Returns null if error is detected, &PL_sv_undef otherwise.
 *
 * Note that there's no byte ordering info emitted when network order 
+was
 * used at store time.
 */
static SV *magic_check(pTHX_ stcxt_t *cxt)
{

    ...


    current = buf + c;
    
    /* sizeof(int) */
    if ((int) *current++ != sizeof(int))
        CROAK(("Integer size is not compatible"));

    /* sizeof(long) */
    if ((int) *current++ != sizeof(long))
        CROAK(("Long integer size is not compatible"));

    /* sizeof(char *) */
    if ((int) *current != sizeof(char *))
        CROAK(("Pointer size is not compatible"));

    if (use_NV_size) {
        /* sizeof(NV) */
        if ((int) *++current != sizeof(NV))
            CROAK(("Double size is not compatible"));
    }

    return &PL_sv_undef;    /* OK */
}

      [download]

      (The comment could be read to suggest another, less generous, interpretation.)

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
      In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]
        I really didn't expect that Storable would be so fragile over a cross-platform network.

        I can now clearly see that the posts advising the OP to "do it another way" are well founded.
        (Of course, at no stage did I think those posts would prove to be otherwise ;-)

        Cheers,
        Rob
[reply]

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