Re: Base36
From: William Stacey [MVP] (staceywREMOVE_at_mvps.org)
Date: 11/08/04
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Date: Sun, 7 Nov 2004 22:09:38 -0500
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 > >> > > > >> > > >> > > >> > > > > > >
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