/*************************************************************************
 *
 * HTCd - Copyright (C) 1998-2006 Henrik Rydberg
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include <mime/enc.h>

static unsigned char char2six[256]={
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,62,65,65,65,63,
  52,53,54,55,56,57,58,59,
  60,61,65,65,65,64,65,65,
  65, 0, 1, 2, 3, 4, 5, 6,
   7, 8, 9,10,11,12,13,14,
  15,16,17,18,19,20,21,22,
  23,24,25,65,65,65,65,65,
  65,26,27,28,29,30,31,32,
  33,34,35,36,37,38,39,40,
  41,42,43,44,45,46,47,48,
  49,50,51,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65,
  65,65,65,65,65,65,65,65
};
static unsigned char six2char[64]={
  'A','B','C','D','E','F','G','H',
  'I','J','K','L','M','N','O','P',
  'Q','R','S','T','U','V','W','X',
  'Y','Z','a','b','c','d','e','f',
  'g','h','i','j','k','l','m','n',
  'o','p','q','r','s','t','u','v',
  'w','x','y','z','0','1','2','3',
  '4','5','6','7','8','9','+','/'
};
inline void tri2quad(mstream& out,unsigned code,int m=4)
{
  char buf[4];
  buf[3]=six2char[code&63U]; code>>=6;
  buf[2]=six2char[code&63U]; code>>=6;
  buf[1]=six2char[code&63U]; code>>=6;
  buf[0]=six2char[code&63U];
  out.write(buf,m);
}
inline void quad2tri(mstream& out,unsigned code,int m=3)
{
  char buf[3];
  buf[2]=code&255U; code>>=8;
  buf[1]=code&255U; code>>=8;
  buf[0]=code&255U;
  out.write(buf,m);
}

void encode64(mstream& out,const sref& in)
{
  unsigned m=0,code=0,wrap=0;
  for(const char* p=in.begin();p!=in.end();p++) {
    code<<=8;
    code|=(unsigned char)*p;
    if(++m==3) {
      tri2quad(out,code);
      m=0;
      if(++wrap==15) { out<<CRLF; wrap=0; }
    }
  }
  if(m==1) {
    code<<=16;
    tri2quad(out,code,2);
    out<<"==";
    if(++wrap==15) { out<<CRLF; wrap=0; }
  }
  else if(m==2) {
    code<<=8;
    tri2quad(out,code,3);
    out.put('=');
    if(++wrap==15) { out<<CRLF; wrap=0; }
  }
  if(wrap>0) out<<CRLF;
}

void decode64(mstream& out,const sref& in)
{
  unsigned m=0,code=0,six=0;
  for(const char* p=in.begin();p!=in.end();p++) {
    six=char2six[(unsigned char)*p];
    if(six>=64) continue;
    code<<=6;
    code|=six;
    if(++m==4) {
      quad2tri(out,code);
      m=0;
    }
  }
  if(m==2) {
    code<<=12;
    quad2tri(out,code,1);
  }
  else if(m==3) {
    code<<=6;
    quad2tri(out,code,2);
  }
}