Re^4: calculating the 3 MSBs from an integer

I am running on AIX and I guess you may be on Windows ? I think your byte order must be the other way round than mine. When you get up to 253..256 does the last value go 7,7,7,0

apart from the binary bytes being reversed the rest works as expected for me on 'doze (NT4)

253     11111101000000000000000000000000        7
254     11111110000000000000000000000000        7
255     11111111000000000000000000000000        7
256     00000000000000010000000000000000        0
[download]

If you replace the I* in the pack with N (force byte order we want and the * was never really required) I think you may see something nicer. This version works on box *nix and *dose for me

perl -le'print join "\t", $_, (unpack "B*", pack "N", $_), ($_ & 0xFF)
+ >>5 for (0..256)'
[download]

Cheers,
R.

Pereant, qui ante nos nostra dixerunt!

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Re^5: calculating the 3 MSBs from an integer by insaniac (Friar) on Feb 17, 2005 at 21:14 UTC
that was it! And I'm using Linux btw, it's been ages since I used MS ;-) but i still don't understand why the `& 0xFF` is required... without it, it seems to work as well -- to ask a question is a moment of shame to remain ignorant is a lifelong shame	[reply] [d/l]
Re^6: calculating the 3 MSBs from an integer by Random_Walk (Prior) on Feb 17, 2005 at 22:20 UTC
Hi Again, Sorry for implying allegiance to Redmond ;). Back home now and just given it a taz on x86/Linux and I get the same reversed byte order. I guess it is the Intel architecture not the OS. Sadly my Alpha/Linux is in another country and offline so no testing possible there. I will try it on a SPARC at work tomorrow just for fun. The & 0xff is a bit mask that will only drop through bits from the first (8 bit) byte. If I take it off when I get to 256 my total goes up to 8 (Intel/Linux). As long as your input is only 1 byte then it will not be a problem. `perl -le'print join "\t", $_, (unpack "B*", pack "N", $_), $_ >>5 for +(0..256)' <snip> 254 00000000000000000000000011111110 7 255 00000000000000000000000011111111 7 256 00000000000000000000000100000000 8` [download] Cheers, R. Pereant, qui ante nos nostra dixerunt!	[reply] [d/l]
Re^7: calculating the 3 MSBs from an integer by insaniac (Friar) on Feb 18, 2005 at 06:43 UTC
ah thanks! now i understand... and at work, i also have a (ultra)sparc(5) with debian linux on it ;-) -- to ask a question is a moment of shame to remain ignorant is a lifelong shame	[reply]