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Re^3: Is this a sane/safe way to pass an aref into a C function?

by BrowserUk (Patriarch)
on Jan 22, 2017 at 23:47 UTC ( #1180131=note: print w/replies, xml ) Need Help??


in reply to Re^2: Is this a sane/safe way to pass an aref into a C function?
in thread Is this a sane/safe way to pass an aref into a C function?

I need a dynamic number of bytes incoming, without having to change the underlying C code,

I'm not quite sure why you think you cannot pass variable length strings in scalars?

Also, whilst pack is one way to encode unsigned bytes into strings, it is not the only way:

#! perl -slw use strict; use Inline C => Config => BUILD_NOISY => 1; use Inline C => <<'END_C', NAME => '_1180095', CLEAN_AFTER_BUILD =>0; int doStuff( SV *sv ) { STRLEN len, i; unsigned char *bytes = SvPVx( sv, len ); printf( "%d : ", len ); // print the hi & lo nybbles, of the unsigned bytes passed, in hex for( i=0; i < len; ++i ) { printf( "%01x %01x\t", ( bytes[ i ] & 0xf0 ) >> 4, bytes[ i ] +& 0x0f ); } printf( "\n" ); return 1; } END_C doStuff( "\x0f\xf0\xaa\x55\x01\x80" ); doStuff( join '', map chr, 0x00 .. 0xff ); doStuff( pack 'C*', 1 .. 10 );

Output:

C:\test>1180095.pl 6 : 0 f f 0 a a 5 5 0 1 8 0 256 : 0 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 + 0 8 0 9 0 a 0 b 0 c 0 d 0 e 0 f 1 0 + 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 +1 9 1 a 1 b 1 c 1 d 1 e 1 f 2 0 2 1 + 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 2 +a 2 b 2 c 2 d 2 e 2 f 3 0 3 1 3 2 + 3 3 3 4 3 5 3 6 3 7 3 8 3 9 3 a 3 b + 3 c 3 d 3 e 3 f 4 0 4 1 4 2 4 3 4 + 4 4 5 4 6 4 7 4 8 4 9 4 a 4 b 4 c + 4 d 4 e 4 f 5 0 5 1 5 2 5 3 5 4 5 5 + 5 6 5 7 5 8 5 9 5 a 5 b 5 c 5 d +5 e 5 f 6 0 6 1 6 2 6 3 6 4 6 5 6 6 + 6 7 6 8 6 9 6 a 6 b 6 c 6 d 6 e 6 +f 7 0 7 1 7 2 7 3 7 4 7 5 7 6 7 7 + 7 8 7 9 7 a 7 b 7 c 7 d 7 e 7 f 8 0 + 8 1 8 2 8 3 8 4 8 5 8 6 8 7 8 8 +8 9 8 a 8 b 8 c 8 d 8 e 8 f 9 0 9 1 + 9 2 9 3 9 4 9 5 9 6 9 7 9 8 9 9 9 +a 9 b 9 c 9 d 9 e 9 f a 0 a 1 a 2 + a 3 a 4 a 5 a 6 a 7 a 8 a 9 a a a b + a c a d a e a f b 0 b 1 b 2 b 3 b + 4 b 5 b 6 b 7 b 8 b 9 b a b b b c + b d b e b f c 0 c 1 c 2 c 3 c 4 c 5 + c 6 c 7 c 8 c 9 c a c b c c c d +c e c f d 0 d 1 d 2 d 3 d 4 d 5 d 6 + d 7 d 8 d 9 d a d b d c d d d e d +f e 0 e 1 e 2 e 3 e 4 e 5 e 6 e 7 + e 8 e 9 e a e b e c e d e e e f f 0 + f 1 f 2 f 3 f 4 f 5 f 6 f 7 f 8 f + 9 f a f b f c f d f e f f 10 : 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 + 0 9 0 a C:\test>

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