#############################################################################
#
#	File:     base64.icn
#
#	Subject:  Procedures for base64 encodings for MIME (RFC 2045)
#
#	Author:   David A. Gamey
#
#	Date:     May 2, 2001
#
#############################################################################
#
#   This file is in the public domain.
#
#############################################################################
#
#     Descriptions:
#
#     base64encode( s1 ) : s2
#
#        returns the base64 encoding of a string s1
#
#     base64decode( s1 ) : s2
#
#        returns the base64 decoding of a string s1
#        fails if s1 isn't base64 encoded
#
#     references:  MIME encoding Internet RFC 2045
#
#############################################################################

procedure base64encode(s)   #: encode a string into base 64 (MIME)
   local  pad, t, i, j, k
   static b64
   initial b64 := &ucase || &lcase || &digits || "+/"

   i := (3 - (*s % 3)) % 3
   s ||:= repl("\x00",i)
   pad := repl("=",i)

   t := ""
   s ? while ( i := ord(move(1)), j := ord(move(1)), k := ord(move(1)) ) do {
      t ||:= b64[ 1 + ishift(i,-2) ]
      t ||:= b64[ 1 + ior( ishift(iand(i,3),4), ishift(j,-4) ) ]
      t ||:= b64[ 1 + ior( ishift(iand(j,15),2), ishift(k,-6) ) ]
      t ||:= b64[ 1 + iand(k,63) ]
      }
   t[ 0 -: *pad ] := pad

   return t
end

procedure base64decode(s)  #: decode a string from base 64 (MIME)
   local t, w, x, y, z
   static b64, c64, n64
   initial {
      b64 := &ucase || &lcase || &digits || "+/"
      c64 := cset(b64)
      n64 := string(&cset)[1+:64]
      }

   if not s ? ( tab(many(c64)), =("===" | "==" | "=" | ""), pos(0)) then fail
   if ( *s % 4 ) ~= 0 then fail

   s := map(s,"=","\x00")
   s := map(s,b64,n64)

   t := ""
   s ? while ( w := ord(move(1)), x := ord(move(1)),
               y := ord(move(1)), z := ord(move(1)) ) do {
      t ||:= char( ior( ishift(w,2), ishift(x,-4) ) )
      t ||:= char( ior( iand(ishift(x,4),255), ishift(y,-2) ) )
      t ||:= char( ior( iand(ishift(y,6),255), z ) )
      }

   return trim(t,'\x00')
end