On 08 June 2004 19:00, Ren� Fournier wrote:
> OK, that makes sense. But here's the problem: I receive binary data
> from SuperSPARC (big-endian), which I need to unpack according to
> certain documented type definitions. For example, let's say that $msg
> has the value "3961595508" and is packed as an unsigned long integer
> (on the remote SPARC). But when I receive it, and unpack it...
>
> $unpacked = unpack('Nval', $msg); // N for unsigned long integer,
> big-endian (SPARC) echo $unpacked["val"];
>
> ...the output value is "-333371788". (???) Which tells me that PHP is
> NOT unpacking $msg as an unsigned long integer, but rather as
> a signed
> integer (since unsigned integers cannot be negative).
>
> Now, thanks to your suggestions, I can convert that number back to an
> unsigned integer-or at least make it positive. But I
> shouldn't have to
> convert it, should I?
Yes.
Whether an integer is signed or unsigned is simply a matter of how you interpret the
32 bits representing it -- unsigned 3961595508 is represented in 32 bits in exactly
the same way as signed -333371788. This explains the results you are getting: PHP
*is* unpacking your binary(?) data as unsigned, but, as PHP doesn't have an unsigned
type, the only place it has to put the resulting 32-bit representation is in a PHP
integer, which is signed -- so when you print it, you get the signed representation.
To get PHP to print the unsigned representation of an integer, you can use the %u
format specifier of sprintf() (http://www.php.net/sprintf) or one of its *printf
friends.
Cheers!
Mike
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