I have been trying to unserialize on a 32-bit server an object that was serialized on a 64-bit server. I have isolated my problem to an integer in the object. Here is a small reproduction of the problem.
On a 64-bit machine:
$i = serialize('20110510134021'); //i:20110510134021;
On a 32-bit machine:
$i = unserialize('i:20110510134021;');
Gives the error
Notice: unserialize(): Error at offset 0 of 16 bytes
Now I understand that those serialization method shouldn't be used for cross system data transmition. However, we are merely trying to migrate the data to another system, not use it actively for transfers. This is a one time thing.
I would think that this might be due to integer overflow, but even on the 32-bit server I can do something like
$i = 20110510134021;
echo $i;
And it will work fine. I'm guessing PHP integer types scale to some double type or something like that. But why doesn't it do that when it unserializes?
How can I unserialize those objects? If I can't, is there any way to convert them to something else? Finally, has anyone written a deserialize method in PHP itself? Or has details on the protocol? I could use that and have a custom case for those integers.
Thanks.
Note: I do not have access to the original data, only the serialized result.
The max integer on 32 bit system is 4294967296;
$i = 20110510134021; works because PHP converts the variable to double.
So replace i with d
$i = unserialize('d:20110510134021;');
If you run this script, you will see the correct represenation of the variable on the system you are running (d: on 32 bit system, i: on 64 bit system):
$int = 20110510134021;
var_dump(serialize($int));
The simple solution is if you know that there is a chance that data serialized on 64 bit will be unserialized on 32 bit machine is to cast it to (double) before serializing.
Then it will be unserialized as a double, giving you more bits per integer than a standard 4-byte per integer (32 bits)
Once unserialized just work with that number as a double. In 99% of the cases this is a good solution. There is still a chance that for a very large number the number of bits allocated to the 'real' part on the number to a double on a 32 bit machine will not be enough. I think it's 56 bits, so the maximum integer is still significantly larger that the 32bits for the int type.
How about:
$serialized = 'i:20110510134021';
if (preg_match('/i\:([\d]+)/', $serialized, $match))
{
$unserialized = $match[1];
}
Related
I understand Integer size, PHP_INT_MAX is platform dependent.
On 64-bit system I can get a:
$large_number = 9223372036854775807
From what I read from PHP Document Example 3 here, when integer overflows, PHP handles integer as float with a precision of roughly 14 decimals digits, i.e:
Unsigned Int64: 18446744073709551615
PHP will handles as: 1.844674407371E+19
So it seems all precision only kept up to the max of Signed Int64.
Is this really just a limitation of PHP and there is nothing I can do about it?
This is pretty hacky, and I assure you your life will be easier using GMP but it is possible using pack() and a little binary thinking:
<?php
$large_number = 9223372036854775807;
$left = 0xffffffff00000000;
$right = 0x00000000ffffffff;
$l = ($large_number & $left) >>32; //shift 32 bits left
$r = $large_number & $right;
$int64_binary_string = pack('NN', $l, $r);
I haven't tested this, and wouldn't use it in real life, but it's probably close to what you're looking for.
http://tw1.php.net/manual/en/function.pack.php
if you need precision or numbers outside of PHP_INT_MAX / PHP_INT_MIN, learn to use GMP, which will probably keep going until you run out of memory... to give you some idea of how far you can take it,
$large_number = gmp_init("9223372036854775807");
$i=0;
while(true){
echo 'iteration '.$i++.':'.gmp_strval($large_number).'*1337=';
$large_number = gmp_mul($large_number,"1337");
echo gmp_strval($large_number).PHP_EOL;
}
will eventually
iteration 1291:63173727399431265977452467325176816266767500735669001788445953704
99100022309199341754638029233101065727095873054512847649411469159231474984853877
29990385564525384931210393372816147935077346316357322846070505282141866990047417
69795035320095201175780336777052639896516690649784147989039497959127394363606555
18277493016490689369408018504673663458745651065704848764945821685549595325229654
78521759046816461228651950877052534907426557036526546565508337234675673499891633
29265311281809541141691613057522094435618917713573494707844587004419303204290366
80410319411622496279245084808349790649184389864091281089934776245296259423173088
37125998364710920001673776690982404095905353172292803413540568804924330209161221
68502039031454119485450113377479892509776976500478875924900269471621353800015849
16768619446056453580306524878177680668058129358555807454509042635315136209751306
28888008462882394248192470687562440408441365704520299664521180552207604024174563
43137016510143518117853956283018500610190006192251441907450531358798897519852285
89712288688300401723956266383086427686519451058576140512867416675873224992592868
63873656820691379608416040082157797343590944870890093034489537997624441231196880
03716995482080107872348544579795198224539076738023147659657987086535844760748293
51680757422559231216506109885022428024013042708325323490543266063675126192858475
51062320509059668456301511665702512575733290996693385011230330439062943182094596
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15486864936613368395909757833185705018554557948762713677856056206953385065593915
49326215023945424937441813782143778143766220175505533500485707438756395764163323
47714668439588417016028256182365660677880890399143415948539281432076160651247693
72982310275084829961404187585100633245654443972233743905144338234758859827413170
88983027723373315156469586730671906768407758289550985343535503818941377020797426
18604249085624012174154963219214543971133251713032811649089587541472009254502083
21938426925234679535003649815691245256828585977342824147515002509080267191887689
93756807224396178461744274960675671607151017304225081498878127594506757910634207
82366257650930768410626608502254524385838019829644847875689142861722171975269086
27152913039908221672006718321592434013558052896236283594560899204934144043552210
8813052796446077685440711695302241857244755302464656726076289075058391*1337=8446
32735330396026118539488137614033486681484835894553911522401035729672982739951992
59510450846561248771271822738836773072631342658924820547496339499714549977043965
30282959394551897891984120249697406451962655622236761656933974621596222296728397
20183102709193795416428153987614058613458087713533262641419642793700816304805168
68985207407486880443429354748473827987325635935798089498320484478359184559360866
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53300041031861800262087455987369484209627287346984244451204684319717267396169213
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87664513792449357865428353820641409325285645926908332041329290558106564944174076
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54729823959690842761271167222679111659279222369969505862293059483051588848405865
434231536619097363136237839395246042763998493353068767
*and by "eventually", i mean less than 5 seconds on my laptop..
Yes it is a limitation of PHP and there is nothing you can do about it short of recompiling your PHP interpreter. Even then you are limited to the types your native system supports which wouldn't be bigger than 64bit normally. You can, as you know, use GMP, or BCMath, but that is not what your asking.
Under the hood, depending on your system the PHP integer and PHP floating point types corresponds to a signed C integer type, and C float types (PHP always uses C doubles for 'floats' AFAIK). This is a static relationship and can't change after compile time. Since the C types have fixed precision of course the PHP ones do too.
The "overflow" into a float is just a convenient compromise so you can store really big numbers, rather than not at all. Your losing some precision yeah, but only in the significand. PHP is not going to automatically convert the number to some other bigger precision floating point format because it doesn't have one.
I understand Integer size, PHP_INT_MAX is platform dependent.
On 64-bit system I can get a:
$large_number = 9223372036854775807
From what I read from PHP Document Example 3 here, when integer overflows, PHP handles integer as float with a precision of roughly 14 decimals digits, i.e:
Unsigned Int64: 18446744073709551615
PHP will handles as: 1.844674407371E+19
So it seems all precision only kept up to the max of Signed Int64.
Is this really just a limitation of PHP and there is nothing I can do about it?
This is pretty hacky, and I assure you your life will be easier using GMP but it is possible using pack() and a little binary thinking:
<?php
$large_number = 9223372036854775807;
$left = 0xffffffff00000000;
$right = 0x00000000ffffffff;
$l = ($large_number & $left) >>32; //shift 32 bits left
$r = $large_number & $right;
$int64_binary_string = pack('NN', $l, $r);
I haven't tested this, and wouldn't use it in real life, but it's probably close to what you're looking for.
http://tw1.php.net/manual/en/function.pack.php
if you need precision or numbers outside of PHP_INT_MAX / PHP_INT_MIN, learn to use GMP, which will probably keep going until you run out of memory... to give you some idea of how far you can take it,
$large_number = gmp_init("9223372036854775807");
$i=0;
while(true){
echo 'iteration '.$i++.':'.gmp_strval($large_number).'*1337=';
$large_number = gmp_mul($large_number,"1337");
echo gmp_strval($large_number).PHP_EOL;
}
will eventually
iteration 1291:63173727399431265977452467325176816266767500735669001788445953704
99100022309199341754638029233101065727095873054512847649411469159231474984853877
29990385564525384931210393372816147935077346316357322846070505282141866990047417
69795035320095201175780336777052639896516690649784147989039497959127394363606555
18277493016490689369408018504673663458745651065704848764945821685549595325229654
78521759046816461228651950877052534907426557036526546565508337234675673499891633
29265311281809541141691613057522094435618917713573494707844587004419303204290366
80410319411622496279245084808349790649184389864091281089934776245296259423173088
37125998364710920001673776690982404095905353172292803413540568804924330209161221
68502039031454119485450113377479892509776976500478875924900269471621353800015849
16768619446056453580306524878177680668058129358555807454509042635315136209751306
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03716995482080107872348544579795198224539076738023147659657987086535844760748293
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27152913039908221672006718321592434013558052896236283594560899204934144043552210
8813052796446077685440711695302241857244755302464656726076289075058391*1337=8446
32735330396026118539488137614033486681484835894553911522401035729672982739951992
59510450846561248771271822738836773072631342658924820547496339499714549977043965
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53506783887636700979595292482900428172427958399610988487824191523745981361850004
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20468015856906162855718175811402571115916602835577500306211903371964419937747843
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53300041031861800262087455987369484209627287346984244451204684319717267396169213
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11439273457043778342886520414406889931665405902225381466032093468840906182958490
40067007538064972385604595988992584428764922065891385936525652108407127397334152
77577987012630748507156907484796296338436704249630828087630933181681675714232538
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89878879946652085040124400663361621041802303798851312902275116583020189066763097
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84494632525395498991320929552989623300263691567683124365569447208054714159350718
63081591475681297110348362690241888609141200075894224902233777226934570198564942
62389139828831041708163976489496312464200707570741034016781184280864313770936734
13966676078625322832980760007005101208004862489022724360915838409882820115703865
87664513792449357865428353820641409325285645926908332041329290558106564944174076
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40734756324139507980786753851729563208385832156894416773034762738098032723080792
44765548714573368685710420592114171685959409873882010592984896309489553137529668
91261773670019374523853883132878624380432154218001861595424734463034850618569271
90374542447907623411522862507612119581666719929400829186215604902943767120983212
02544471505640473874642620655839478699640912521556176910985261615442047526176536
97235141776796603138771014504394692811314927335598670398583505556436746592441767
65771005964615976778954300093716097017729308511008961468237442731938425891977201
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434231536619097363136237839395246042763998493353068767
*and by "eventually", i mean less than 5 seconds on my laptop..
Yes it is a limitation of PHP and there is nothing you can do about it short of recompiling your PHP interpreter. Even then you are limited to the types your native system supports which wouldn't be bigger than 64bit normally. You can, as you know, use GMP, or BCMath, but that is not what your asking.
Under the hood, depending on your system the PHP integer and PHP floating point types corresponds to a signed C integer type, and C float types (PHP always uses C doubles for 'floats' AFAIK). This is a static relationship and can't change after compile time. Since the C types have fixed precision of course the PHP ones do too.
The "overflow" into a float is just a convenient compromise so you can store really big numbers, rather than not at all. Your losing some precision yeah, but only in the significand. PHP is not going to automatically convert the number to some other bigger precision floating point format because it doesn't have one.
In PHP I have a 64 bit number which represents tasks that must be completed. A second 64 bit number represents the tasks which have been completed:
$pack_code = 1001111100100000000000000011111101001111100100000000000000011111
$veri_code = 0000000000000000000000000001110000000000000000000000000000111110
I need to compare the two and provide a percentage of tasks completed figure. I could loop through both and find how many bits are set, but I don't know if this is the fastest way?
Assuming that these are actually strings, perhaps something like:
$pack_code = '1001111100100000000000000011111101001111100100000000000000011111';
$veri_code = '0000000000000000000000000001110000000000000000000000000000111110';
$matches = array_intersect_assoc(str_split($pack_code),str_split($veri_code));
$finished_matches = array_intersect($matches,array(1));
$percentage = (count($finished_matches) / 64) * 100
Because you're getting the numbers as hex strings instead of ones and zeros, you'll need to do a bit of extra work.
PHP does not reliably support numbers over 32 bits as integers. 64-bit support requires being compiled and running on a 64-bit machine. This means that attempts to represent a 64-bit integer may fail depending on your environment. For this reason, it will be important to ensure that PHP only ever deals with these numbers as strings. This won't be hard, as hex strings coming out of the database will be, well, strings, not ints.
There are a few options here. The first would be using the GMP extension's gmp_xor function, which performs a bitwise-XOR operation on two numbers. The resulting number will have bits turned on when the two numbers have opposing bits in that location, and off when the two numbers have identical bits in that location. Then it's just a matter of counting the bits to get the remaining task count.
Another option would be transforming the number-as-a-string into a string of ones and zeros, as you've represented in your question. If you have GMP, you can use gmp_init to read it as a base-16 number, and use gmp_strval to return it as a base-2 number.
If you don't have GMP, this function provided in another answer (scroll to "Step 2") can accurately transform a string-as-number into anything between base-2 and 36. It will be slower than using GMP.
In both of these cases, you'd end up with a string of ones and zeros and can use code like that posted by #Mark Baker to get the difference.
Optimization in this case is not worth of considering. I'm 100% sure that you don't really care whether your scrip will be generated 0.00000014 sec. faster, am I right?
Just loop through each bit of that number, compare it with another and you're done.
Remember words of Donald Knuth:
We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.
This code utilizes the GNU Multi Precision library, which is supported by PHP, and since it is implemented in C, should be fast enough, and supports arbitrary precision.
$pack_code = gmp_init("1001111100100000000000000011111101001111100100000000000000011111", 2);
$veri_code = gmp_init("0000000000000000000000000001110000000000000000000000000000111110", 2);
$number_of_different_bits = gmp_popcount(gmp_xor($pack_code, $veri_code));
$a = 11111;
echo sprintf('%032b',$a)."\n";
$b = 12345;
echo sprintf('%032b',$b)."\n";
$c = $a & $b;
echo sprintf('%032b',$c)."\n";
$n=0;
while($c)
{
$n += $c & 1;
$c = $c >> 1;
}
echo $n."\n";
Output:
00000000000000000010101101100111
00000000000000000011000000111001
00000000000000000010000000100001
3
Given your PHP-setuo can handle 64bit, this can be easily extended.
If not you can sidestep this restriction using GNU Multiple Precision
You could also split up the HEx-Representation and then operate on those coresponding parts parts instead. As you need just the local fact of 1 or 0 and not which number actually is represented! I think that would solve your problem best.
For example:
0xF1A35C and 0xD546C1
you just compare the binary version of F and D, 1 and 5, A and 4, ...
I've used unpack to convert most of the data types I have in a binary file that I'm parsing with little problems. I have no idea how to work with a big endian 64-bit signed long. I think this data type is stored using 2's complement. The application of the data file I'm reading is a java app so I assume it's 2's complement. I don't need to work with it as a number but simply work with it as a string.
Java 64-bit integers are indeed stored natively as "network-order" (big endian, i.e. start with the most significant byte) 8-byte 2's complement format. So typically you take byte at a time, shift left by 8, repeat. Byte values can be thought of as unsigned (while result is signed), but with left-shifting this should not matter.
So: first you just created equivalent 64-bit int from bytes, and display from there. No point in using short cuts; while it is possible, you just end up with more complicated and less efficient code.
32-bit PHP will only have signed 32-bit integers, thus as far as I know, there's no way to natively unpack the data.
The following code should be able to read a big endian, two's complement 64-bit integer:
<?php
function read_int64($fp)
{
$hex = unpack('H16a', fread($fp, 8));
$hex = '0x'.$hex['a'];
$n = gmp_init($hex);
if (gmp_testbit($n, 63))
{
$n = gmp_xor($n, '0xffffffffffffffff'); // flip the bits
$n = gmp_neg(gmp_add($n, 1)); // add one and negate
}
return gmp_strval($n);
}
?>
It returns the integer as a string. It can be used like:
$fp = fopen('test.bin', 'rb');
echo read_int64($fp)."\n";
fclose($fp);
(Edit: Updated code to call fewer GMP functions.)
I have a simple function that I'm using but for some reason the number doesn't calculate correctly as it would in a calculator. I think it has something to do with the numbers being too large, or something to do with 64 bit. Is there any way I can convert them so that they would work correctly?
$sSteamComID = 76561197990369545;
$steamBase = 76561197960265728;
function convertToSteamID($sSteamComID) {
$sServer = bcmod($sSteamComID, '2') == '0' ? '0' : '1';
$sCommID = bcsub($sSteamComID, $sServer);
$sCommID = bcsub($sCommID, $steamBase);
$sAuth = bcdiv($sCommID, '2');
echo "$sServer:$sAuth";
}
convertToSteamID($sSteamComID);
This function outputs 0:15051912 on a server when it should be printing 1:15051908
The missing global $steamBase was the problem, as already mentioned in a comment. (Tip: turn on E_NOTICE during development.) However, I'd like to address your question:
I think it has something to do with
the numbers being too large, or
something to do with 64 bit. Is there
any way I can convert them so that
they would work correctly?
PHP integers are signed and platform-dependent. Using 64-bit numbers will not work if you are on a 32-bit host.
So your concern is valid. But even on a 64-bit system:
$x = 9223372036854775808; // highest bit (64th) set
var_dump($x);
--> float(9.2233720368548E+18)
Note that PHP's BC Math routines operate on strings, not integers. Thus, you should be storing your big numbers as strings.
This will work around the potential problem of integers being converted to floats, which will happen even on your 64-bit environment if you are using large, unsigned integers.