Convert 4-byte string to integer

[Dave Turner]

Ive used fwrite to store 4 bytes in a file: "Test" (or 0x54657374 /
1953719636). Its easy enough to use fread to get those 4 bytes, but the
problem is I need to work with the data as a number and not a string, so how
can I convert it to the number 1953719636 ?

[Ewoud Dronkert]

Re: Convert 4-byte string to integer

"Dave Turner" <nobody@nowhere .nohow> wrote in message
news:426f6ca7$1 @quokka.wn.com. au...[color=blue]
> Ive used fwrite to store 4 bytes in a file: "Test" (or 0x54657374 /
> 1953719636). Its easy enough to use fread to get those 4 bytes, but the
> problem is I need to work with the data as a number and not a string, so
> how can I convert it to the number 1953719636 ?[/color]

http://php.net/unpack

[Dave Turner]

Re: Convert 4-byte string to integer

Example please? It doesnt seem to be working ...

<?
$packed = "Test";
$unpacked = unpack("L", $packed);
echo $unpacked;
?>

It should echo 1953719636, but it's not displaying anything

[Dave Turner]

Re: Convert 4-byte string to integer

Hmmm, ok :-) Well this works, but it doesnt seem very efficient:

<?
$Buffer = "Test";

$Number = ord($Buffer{0}) | (ord($Buffer{1} )<<8) | (ord($Buffer{2} )<<16) |
(ord($Buffer{3} )<<24);

echo $Number;
?>

If anyone knows of a better method I'd appreciate it, thanks

[Ewoud Dronkert]

Re: Convert 4-byte string to integer

"Dave Turner" <nobody@nowhere .nohow> wrote:[color=blue]
> Example please? It doesnt seem to be working ...
>
> <?
> $packed = "Test";
> $unpacked = unpack("L", $packed);
> echo $unpacked;
> ?>
>
> It should echo 1953719636, but it's not displaying anything[/color]

It does work, but you didn't read the docpage well. unpack() returns an
array so use print_r() instead of echo.

E.

[Dave Turner]

Re: Convert 4-byte string to integer

> It does work, but you didn't read the docpage well. unpack() returns an[color=blue]
> array so use print_r() instead of echo.[/color]
Thankyou for clarifying that, "echo $unpacked[1];" also works

So i guess my final question is - what is more efficient? unpack() or 4 x
Ord() ?

[Ewoud Dronkert]

Re: Convert 4-byte string to integer

"Dave Turner" <nobody@nowhere .nohow> wrote:[color=blue]
> So i guess my final question is - what is more efficient? unpack() or 4 x
> Ord() ?[/color]

function utime()
{
list( $usec, $sec ) = explode( ' ', microtime() );
return ((float)$usec + (float)$sec);
}

$t = utime();
for ( $i = 0; $i < 1000000; ++$i )
{
//insert code for testing here
}
$t = utime() - $t;
echo "Time : $t sec\n";

[Dave Turner]

Re: Convert 4-byte string to integer

Very useful timing routine, thanks. The unpack/array[1] method is faster by
about 25% over the 4 x ord() method