Given that weekends are typically slower than through the week, I thought I'd ask for a quick code review of those who understand the perl internals. This is my real first attempt at doing anything regarding manipulating and managing perl data types in C/XS, and am just wondering if what I've got below is reasonable, sane and safe, or if there are better ways to do it.
Instead of passing an integer into the C function then doing a bunch of bit shifting to get out the required number of bytes, I wanted to pass in an array reference so that the number of bytes can be dynamic (otherwise with an int, I'm limited to a maximum of four bytes in a call to testing()).
use warnings;
use strict;
use Inline 'C';
my $channel = 0;
my @bytes = (0x00, 0x01, 0x02, 0x03);
testing($channel, \@bytes, 4);
__END__
__C__
int testing(int channel, SV* byte_ref, int len){
if (channel != 0 && channel != 1){
croak("channel param must be 0 or 1\n");
}
if (! SvROK(byte_ref) || SvTYPE(SvRV(byte_ref)) != SVt_PVAV){
croak("not an aref\n");
}
AV* bytes = (AV*)SvRV(byte_ref);
int num_bytes = av_len(bytes) + 1;
if (len != num_bytes){
croak("$len param != elem count\n");
}
unsigned char buf[num_bytes];
int i;
for (i=0; i<len; i++){
SV** elem = av_fetch(bytes, i, 0);
buf[i] = (int)SvNV(*elem);
}
/*
* here, I'll be passing the char buffer and len
* to an external C function. For display, I'll
* just print the elements (the return is from ioctl())
*
* if ((spiDataRW(channel, buf, len) < 0){
* croak("failed to write to the SPI bus\n");
* }
*/
int x;
for (x=0; x<len; x++){
printf("%d\n", buf[x]);
}
}
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