Messages in this thread |  | | Date | Tue, 18 Feb 2003 18:12:48 +0100 | From | Jan-Benedict Glaw <> | Subject | Re: [PATCH] morse code panics for 2.5.62 |
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On Tue, 2003-02-18 11:00:23 -0500, Andrew Rodland <arodland@noln.com> wrote in message <b2tl9c$48c$1@main.gmane.org>: > Jan-Benedict Glaw wrote: > > On Tue, 2003-02-18 14:50:38 +0100, Tomas Szepe <szepe@pinerecords.com> > > wrote in message <20030218135038.GA1048@louise.pinerecords.com>: > > > > This is the first time I really look at the code, so please forgive if I > > talk about things where already a consens was given... > > >> +const unsigned char morsetable[] = { > >> + 0122, 0, 0310, 0, 0, 0163, /* "#$%&' */ > >> + 055, 0155, 0, 0, 0163, 0141, 0152, 0051, /* ()*+,-./ */ > >> + 077, 076, 074, 070, 060, 040, 041, 043, 047, 057, /* 0-9 */ > >> + 0107, 0125, 0, 0061, 0, 0114, 0, /* :;<=>?@ */ > >> + 006, 021, 025, 011, 002, 024, 013, 020, 004, /* A-I */ > >> + 036, 015, 022, 007, 005, 017, 026, 033, 012, /* J-R */ > >> + 010, 003, 014, 030, 016, 031, 035, 023, /* S-Z */ > >> + 0, 0, 0, 0, 0154 /* [\]^_ */ > >> +}; > > > > > You're using a set bit for long and an unset bit for a short beep, don't > > you? Storing these values in octal/as chars is quite low on memory > > consumption, but I'd like to learn so I suggest: > > It's slightly more complicated than that: > It's set bits for long, unset bits for short, and termination when the byte > equals 0x01 (in other words, there's an extra set bit to the left of what > we want). This lets us represent any variable-length morse of up to 7 > dits/dahs with a byte, which is cool because nothing is more than 6, that > I've ever seen.
So you've got a leading I bit set. Morse alphabet has got 2, 3, 4, 5 or 6 dots/dashes, right? Then I vote for either having a macro like this:
#define MORSE(letter, len, b1, b2, b3, b4, b5, b6, b7) \ (1<<(len)| [all the shifting stuff here as of the last mail])
or let's have5 separate macros for all possible lengths (which are possibly defined by using the above macro).
Really, I'm 100% for learning!
> The use of macros is an OK hack though, it reminds me of the nethack source. > :) > > The reason someone proposed this in the first place is because I had had > > const unsigned char * morsetable [] = { > ".-..-.", NULL, "...-..-" > > and so on in the initial revision of my patch, which is quite readable, but > takes up a lot more space, and makes the code actually a bit messier too.
Oh, that's long, too...
What about
#define IS_DASH(letter, shift) \ ((letter) == '-'? (1 << shift): (0 << shift)) MORSE(shift, b1, b2, b3, b4, b5, b6) \ (1 << (shift) | IS_DASH((b1), 5) | IS_DASH((b2), 4) \ | IS_DASH((b3), 3) | IS_DASH((b4), 2) \ | IS_DASH((b5), 1) | IS_DASH((b6), 0) #define MORSE1(letter, b1) \ MORSE(1, '.', '.', '.', '.', '.', (b1))) #define MORSE2(letter, b1, b2) \ MORSE(2, '.', '.', '.', '.', (b1), (b2))) #define MORSE3(letter, b1, b2, b3) \ MORSE(3, '.', '.', '.', (b1), (b2), (b3)) #define MORSE4(letter, b1, b2, b3, b4) \ MORSE(4, '.', '.', (b1), (b1), (b3), (b4)) #define MORSE5(letter, b1, b2, b3, b4, b5) \ MORSE(5, '.', (b1), (b2), (b3), (b4), (b5)) #define MORSE6(letter, b1, b2, b3, b4, b5, b6) \ MORSE(6, (b1), (b2), (b3), (b4), (b5), (b6))
Then, you can have const char morses[] = { MORSE2('A', '.', '-'), MORSE4('B', '-', '.', '.', '.'), MORSE4('C', '-', '.', '-', '.'), MORSE3('D', '-', '.', '.'), MORSE1('E', '.'), MORSE4('F', '.', '.', '-', '.') ... };
That's going to take exactly the same memory in the compiled vmlinux image, *and* it's really readable:-) Of course, gcc will optimize any added "bloat" away...
MfG, JBG
-- Jan-Benedict Glaw jbglaw@lug-owl.de . +49-172-7608481 "Eine Freie Meinung in einem Freien Kopf | Gegen Zensur fuer einen Freien Staat voll Freier Bürger" | im Internet! Shell Script APT-Proxy: http://lug-owl.de/~jbglaw/software/ap2/ [unhandled content-type:application/pgp-signature] |  |