From: MagerValp on 17 Oct 2006 14:12 >>>>> "WM" == Wolfgang Moser writes: WM> Something that took my attention, too, were the two lines with the WM> bit shift quirks done in BASIC. I had the feeling that doing WM> floating point math would a bit more "type- in-efficient". WM> 200 v=0 : for k=1 to 4 WM> 210 q=asc(mid\$(q\$,k,1)): gosub 300 WM> 220 v=v*64 + q: next WM> 230 for k=2 to 0 step -1 WM> 240 q=v : v=v/256 : q=q-256*int(v) WM> 250 poke a+k,q: c=(c+q) and 255: next WM> 260 return Aha, interesting. -- ___ . . . . . + . . o _|___|_ + . + . + . Per Olofsson, arkadspelare o-o . . . o + MagerValp(a)cling.gu.se - + + . http://www.cling.gu.se/~cl3polof/ From: MagerValp on 17 Oct 2006 14:18 >>>>> "WM" == Wolfgang Moser writes: WM> Btw. this just remembered me to some old software registration key WM> system, where the following 5-Bit mapping was used. WM> convTable:array [0..\$1F] of char =( WM> '0','1','2','3','A','B','C','D','E','F','G','H','4','5','6','J', WM> 'K','L','M','N','7','8','9','P','Q','R','S','T','W','X','Y','Z' WM> ); WM> ... WM> if not (Key[i] in ['0'..'9', 'A'..'H', 'J'..'N', WM> 'P'..'T', 'W'..'Z']) then break; WM> The characters: 'I', 'O' (Oh), 'U' and 'V' were omitted to reduce WM> misinterpretations. Hmm, we might have a winner here. You can fit 19+1 bytes per line with this scheme, resulting in 36 lines of data. The tricky part is handling the checksum byte in a convenient way. -- ___ . . . . . + . . o _|___|_ + . + . + . Per Olofsson, arkadspelare o-o . . . o + MagerValp(a)cling.gu.se - + + . http://www.cling.gu.se/~cl3polof/ From: Wolfgang Moser on 17 Oct 2006 14:45 MagerValp schrieb:> WM> 200 v=0 : for k=1 to 4 > WM> 210 q=asc(mid\$(q\$,k,1)): gosub 300 > WM> 220 v=v*64 + q: next > WM> 230 for k=2 to 0 step -1 > WM> 240 q=v : v=v/256 : q=q-256*int(v) > WM> 250 poke a+k,q: c=(c+q) and 255: next > WM> 260 return > > Aha, interesting. and perhaps easy adoptable to a 5-bit scheme, not? Which bit depth comes with the C64's floating point format regarding the base (anything but exponent and sign)? Too less, hmmm... thus another technique is needed like intermediate-15-bit-register shifting, with "shifting" meaning to use '*' and '/' operations. Womo From: Wolfgang Moser on 17 Oct 2006 18:01 Hi Per, I don't like competitions. They're simply costing too much time for nothing. > WM> if not (Key[i] in ['0'..'9', 'A'..'H', 'J'..'N', > WM> 'P'..'T', 'W'..'Z']) then break; > > Hmm, we might have a winner here. You can fit 19+1 bytes per line with > this scheme, resulting in 36 lines of data. The tricky part is > handling the checksum byte in a convenient way. hmmmm, 18 byte for data and 11 bits per line as a checksum sounds reasonable. A (not so) quick proof of concept may be (char decoding at 300 omitted): 10 data 1234567890abcdefghjklmnpqrstwxy 20 data yzxwtsrqpnmlkjhgfedcba098765432 99 data end 110 read a\$ 120 if a\$="end" then end 130 r=0 : s=0 : ck=0 140 for i=1 to len(a\$) 150 : if s<8 goto 200 160 : s=s-8 170 : q=r/exp(s * log(2)) and 255 180 : print q;","; 190 : ck = ck + q and 2047 200 : q=asc(mid\$(a\$,i,1)) : gosub 300 210 : r=32 * (r and 127) + q 220 : s=s+5 230 next i 240 print " ==> 11 bit checksum is: ";r and 2047;" vs. ";ck 250 goto 110 300 return Womo PS: line 170 means shift r right by s From: MagerValp on 18 Oct 2006 04:41 >>>>> "WM" == Wolfgang Moser writes: WM> Which bit depth comes with the C64's floating point format WM> regarding the base (anything but exponent and sign)? IIRC, 8-bit exponent, 1-bit sign, and 31-bit mantissa. Plenty of precision there. How about something like this: readline: read a\$ if a\$="end" then end v=0 : s=0 : c=0 for i=1 to len(a\$) q=asc(mid\$(a\$,i,1)) : gosub conv32 v=v*32+q : s=s+5 if s<7 goto nextchar q=v and 255 : v=v/256 : s=s-8 if i=len(a\$) goto checksum poke a,q : a=a+1 : c=c+q goto nextchar checksum: if c<>q then print "checksum error" : end nextchar: next goto readline (Hmm, I should write a simple basic preprocessor, so you can write line number-less code like this) 19+1 bytes per line gives 36 lines of data. The same method can be used with base-64 of course, giving 30 lines of data. What would people prefer though? -- ___ . . . . . + . . o _|___|_ + . + . + . Per Olofsson, arkadspelare o-o . . . o + MagerValp(a)cling.gu.se - + + . http://www.cling.gu.se/~cl3polof/ First  |  Prev  |  Next  |  Last