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(tye)Re: Win32::API

by tye (Cardinal)
on May 24, 2001 at 02:54 UTC ( #82768=note: print w/ replies, xml ) Need Help??


in reply to Win32::API

Tell Win32::API that your pointers to addresses are of type "P". Then you need to allocate space for the address to be placed: my $addr= '\0' x 4;
then pass in $addr to Call().

Then to extract the data, you'll have to use unpack. (APIs that require pointers to addresses often also require you to free buffers that get allocated for you, so don't forget to do that if it is required for your case.)

If the data that the address points to is of known length, then you use "P$len" as the unpack format. If the data that the address points to is a '\0'-terminated string, then use "p" as the unpack format. If the length of the data is inferred from parts of the data itself, then you'll have to use "P$len" to get enough data to infer the next value to use for $len and repeat until you have all of the data. Using "P$len" with $len too large can cause a "core dump". So, for a worst-case example, if the data is a string terminated by a '$', then you'd have to extract the list via something slow and ugly like:

my $addr= '\0' x 4; $api->Call( $addr ); my $len= 1; my $string; do { $string= unpack "p$len", $string; } until( '$' eq substr($string,-1) );

        - tye (but my friends call me "Tye")


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Re: (tye)Re: Win32::API
by brettc (Novice) on May 24, 2001 at 03:55 UTC
    Thanks that is the second time you have saved my bacon. Thanks tye Brett

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