Re: Base36
From: Justin Rogers (Justin_at_games4dotnet.com)
Date: 11/08/04
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Date: Sun, 7 Nov 2004 19:54:11 -0800
I'll go ahead and add some additional types. That is a a fairly easy process. I
need to put some thought into the byte array. Base64 encoding uses a special
padding character to overcome some of the issues you are noting below.
Version 1.1 is posted at the space with all of the base types added.
-- Justin Rogers DigiTec Web Consultants, LLC. Blog: http://weblogs.asp.net/justin_rogers "William Stacey [MVP]" <staceywREMOVE@mvps.org> wrote in message news:OTYmxEUxEHA.3336@TK2MSFTNGP11.phx.gbl... > Thanks Justin. Any chance you could add long and short support, and maybe > arbitrary byte[]s? TIA > For byte[]s I was thinking just converting each byte to base36, but that > results in 2 char min after dec 36. So maybe need to take 4 or 8 bytes at a > time and convert to int or long and convert that to a base to leverage the > resulting chars better - not sure. Any thoughts? > -- > William Stacey, MVP > http://mvp.support.microsoft.com > > "Justin Rogers" <Justin@games4dotnet.com> wrote in message > news:Om9Pw9RxEHA.1260@TK2MSFTNGP12.phx.gbl... >> Code-Only: Arbitrary alphabet encoding (aka BaseN encoding) for base2 > through >> base36. >> >> The notes are extensive as to the direction the library may or may not go >> depending on what >> problems people are trying to solve. What I've realized is that there are > a >> number of additional >> and interesting problems associated with alphabet encoding, such as > permuations, >> cyclic >> rotations, error correction, and the like that may be interesting to build > into >> the libraries. An >> example of an error correction alphabet would be the base32 encoding which >> removes >> characters that may be confused for other characters when read by a human. >> >> >> -- >> Justin Rogers >> DigiTec Web Consultants, LLC. >> Blog: http://weblogs.asp.net/justin_rogers >> >> "Roy Fine" <rlfine@twt.obfuscate.net> wrote in message >> news:unkF9yRxEHA.2192@TK2MSFTNGP14.phx.gbl... >> > William >> > >> > The other base was base 26 and used *just* the uppercase alphabetic >> > characters (A..Z). The only change would be to specify the token set of > the >> > number set and the weights of each position. For the Base26 case, it > was >> > this: >> > >> > /* ***************** */ >> > public class BASE32{ >> > static string tokens = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; >> > static long [] powers = >> > > {1L,26L,26L*26L,26L*26L*26L,26L*26L*26L*26L,26L*26L*26L*26L*26L,26L*26L*26L* >> > > 26L*26L*26L,26L*26L*26L*26L*26L*26L*26L,26L*26L*26L*26L*26L*26L*26L*26L,26L* >> > > 26L*26L*26L*26L*26L*26L*26L*26L,26L*26L*26L*26L*26L*26L*26L*26L*26L*26L,26L* >> > 26L*26L*26L*26L*26L*26L*26L*26L*26L*26L}; >> > ... >> > ... >> > } >> > /* ***************** */ >> > >> > conversion is each direction is based on the tokens and powers arrays. > the >> > first entry in the tokens aray always corresponds to the empty or zero >> > value, etc. >> > >> > happy to help >> > roy >> > >> > >> > "William Stacey [MVP]" <staceywREMOVE@mvps.org> wrote in message >> > news:u$MPFPQxEHA.3908@TK2MSFTNGP12.phx.gbl... >> >> Hey thanks a lot Roy. Care to post the other base as well? Either > way, >> >> thanks again!! >> >> >> >> -- >> >> William Stacey, MVP >> >> http://mvp.support.microsoft.com >> >> >> >> "Roy Fine" <rlfine@twt.obfuscate.net> wrote in message >> >> news:#wPFSCQxEHA.3976@TK2MSFTNGP09.phx.gbl... >> >> > William, >> >> > >> >> > this is something that i did some time ago - actually for a different >> >> base, >> >> > but it was easy enough to change to handle base32. >> >> > >> >> > you did not specify the symbol set for your number base - i will > assume >> >> > 0,1,2,3... X,Y,Z. if yours is different, change the tokens string >> >> > accordingly. >> >> > >> >> > for performance reasons, the weights of the digits are computed at >> > compile >> >> > time. >> >> > >> >> > note - there is absolutely no error checking, and it handles only >> > positive >> >> > values, and assumes that all character codes are upper case. >> >> > >> >> > regards >> >> > roy fine >> >> > >> >> > >> >> > namespace CONVERSION{ >> >> > // handles positive only values up to 4,738,381,338,321,616,896 - 1; >> >> > public class BASE32{ >> >> > static string tokens = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; >> >> > static long [] powers = >> >> > >> >> >> > > {1L,36L,36L*36L,36L*36L*36L,36L*36L*36L*36L,36L*36L*36L*36L*36L,36L*36L*36L* >> >> > >> >> >> > > 36L*36L*36L,36L*36L*36L*36L*36L*36L*36L,36L*36L*36L*36L*36L*36L*36L*36L,36L* >> >> > >> >> >> > > 36L*36L*36L*36L*36L*36L*36L*36L,36L*36L*36L*36L*36L*36L*36L*36L*36L*36L,36L* >> >> > 36L*36L*36L*36L*36L*36L*36L*36L*36L*36L}; >> >> > >> >> > public static string ToString(long lval){ >> >> > int maxStrLen = powers.Length; >> >> > long curval = lval; >> >> > char [] tb = new char[maxStrLen]; >> >> > int outpos = 0; >> >> > for(int i=0; i<maxStrLen; i++){ >> >> > long pval = powers[maxStrLen - i - 1]; >> >> > int pos = (int)(curval / pval); >> >> > tb[outpos++] = tokens.Substring(pos,1).ToCharArray()[0]; >> >> > curval = curval % pval; >> >> > } >> >> > if(outpos==0) tb[outpos++] = '0'; >> >> > return new string(tb,0,outpos).TrimStart('0'); >> >> > } >> >> > >> >> > public static long ToLong(string t){ >> >> > long ival = 0; >> >> > char [] tb = t.ToCharArray(); >> >> > for(int i=0; i<tb.Length; i++){ >> >> > ival += powers[i]*tokens.IndexOf(tb[tb.Length-i-1]); >> >> > } >> >> > return ival; >> >> > } >> >> > } >> >> > } >> >> > >> >> > "William Stacey [MVP]" <staceywREMOVE@mvps.org> wrote in message >> >> > news:uc3%23MkOxEHA.1988@TK2MSFTNGP12.phx.gbl... >> >> > > Anyone have a c# Base10ToBase36 and Base36ToBase10 conversion >> > routines? >> >> > TIA >> >> > > >> >> > > -- >> >> > > William Stacey, MVP >> >> > > http://mvp.support.microsoft.com >> >> > > >> >> > >> >> > >> >> >> > >> > >> >> >
- Next message: Roy Fine: "Re: Base36"
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