http://qs1969.pair.com?node_id=1180088

stevieb has asked for the wisdom of the Perl Monks concerning the following question:

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]); } }