caa@com50.c2s.mn.org (Charles Anderson) (05/31/91)
Yesterday a coworker asked me if I could flip all of the bits in the
font file he was using, and I decided to try using perl to do it.
(I could easily do it in C but I'm trying to learn perl and thought
I'd give it a go.) I tried all sorts of things tr/\000-\377/\377-\000/
didn't work neither did s/./~$&/g in various type of things. I even
tried unpacking it into an array and flipping from there but that wasn't
very succesful either. I but a vec() into the code (something like
vec("blah", 0, 1) to see if the bit twiddling would start working after
that but it didn't. I'm stumped...anybody know how to do it. All I
really want is a bit negation or xor $ff.
-Thanks
Charlie
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big guy -Crash Davis | Suite 170 | Eagan, MN 55121 (I speak for myself)merlyn@iWarp.intel.com (Randal L. Schwartz) (05/31/91)
In article <1991May30.231900.12417@com50.c2s.mn.org>, caa@com50 (Charles Anderson) writes: | | Yesterday a coworker asked me if I could flip all of the bits in the | font file he was using, and I decided to try using perl to do it. | (I could easily do it in C but I'm trying to learn perl and thought | I'd give it a go.) I tried all sorts of things tr/\000-\377/\377-\000/ | didn't work neither did s/./~$&/g in various type of things. I even | tried unpacking it into an array and flipping from there but that wasn't | very succesful either. I but a vec() into the code (something like | vec("blah", 0, 1) to see if the bit twiddling would start working after | that but it didn't. I'm stumped...anybody know how to do it. All I | really want is a bit negation or xor $ff. Here's a really awfully fast program hand-tuned by Larry and me while we were one-upping each other while writing the book. It does exactly what you asked for. *How* it does it should be a useful puzzle to figure out... #!/usr/bin/perl $bufsize = 16384; vec($ones,0,8) = 255; $ones x= $bufsize; while(read(STDIN,$_,$bufsize)) { print STDOUT length != $bufsize ? substr($_ ^ $ones, 0, length) : $_ ^ $ones; } or, you can try it like this: print pack("C*",grep(($_^=255)||1,unpack("C*",pack("H*","b58a8c8bdf9e91908b979a8ddfaf9a8d93df979e9c949a8dd3")))) -- /=Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ==========\ | on contract to Intel's iWarp project, Beaverton, Oregon, USA, Sol III | | merlyn@iwarp.intel.com ...!any-MX-mailer-like-uunet!iwarp.intel.com!merlyn | \=Cute Quote: "Intel: putting the 'backward' in 'backward compatible'..."====/
lwall@jpl-devvax.jpl.nasa.gov (Larry Wall) (06/01/91)
In article <1991May31.162709.7069@iWarp.intel.com> merlyn@iWarp.intel.com (Randal L. Schwartz) writes: : In article <1991May30.231900.12417@com50.c2s.mn.org>, caa@com50 (Charles Anderson) writes: : | : | Yesterday a coworker asked me if I could flip all of the bits in the : | font file he was using, and I decided to try using perl to do it. : | (I could easily do it in C but I'm trying to learn perl and thought : | I'd give it a go.) I tried all sorts of things tr/\000-\377/\377-\000/ You can't give negative ranges like \377-\000. You could construct one and eval it, however. : | didn't work neither did s/./~$&/g in various type of things. I even You'd have to say pack(C,~unpack(C,$&)), or some such. : | tried unpacking it into an array and flipping from there but that wasn't : | very succesful either. I but a vec() into the code (something like : | vec("blah", 0, 1) to see if the bit twiddling would start working after : | that but it didn't. I'm stumped...anybody know how to do it. All I : | really want is a bit negation or xor $ff. : : Here's a really awfully fast program hand-tuned by Larry and me while : we were one-upping each other while writing the book. It does exactly : what you asked for. *How* it does it should be a useful puzzle to : figure out... : : #!/usr/bin/perl : $bufsize = 16384; : vec($ones,0,8) = 255; : $ones x= $bufsize; : while(read(STDIN,$_,$bufsize)) { : print STDOUT length != $bufsize ? : substr($_ ^ $ones, 0, length) : $_ ^ $ones; : } Note that there's a bug in vector ^ (in 4.003) that may prevent this from working. It might work to use the assignment operator, $_ ^= $ones, however. Larry