/*
 *
 * b a s e 6 4 . c			-- Base64 support for STk
 *
 * Copyright © 1998 Erick Gallesio - I3S-CNRS/ESSI <eg@unice.fr>
 * 
 *
 * Permission to use, copy, and/or distribute this software and its
 * documentation for any purpose and without fee is hereby granted, provided
 * that both the above copyright notice and this permission notice appear in
 * all copies and derived works.  Fees for distribution or use of this
 * software or derived works may only be charged with express written
 * permission of the copyright holder.  
 * This software is provided ``as is'' without express or implied warranty.
 *
 *           Author: Erick Gallesio [eg@unice.fr]
 *    Creation date: 20-Jul-1998 12:19
 * Last file update: 20-Jul-1998 19:40
 */

#include <stk.h>
#include <ctype.h>

static char table[] =  
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static char rev_table[128];

#define OutChar(c, f) {Putc((c), (f)); if (++count>=72) {Putc('\n', (f)); count=0;}}

static void initialize_rev_table(void)
{
  char *p;
  int count = 0;

  for (p = table; *p; p++) rev_table[*p] = count++;
}

static void encode(FILE *f, FILE *g)
{
  int c, state, count, old;

  state = old = count = 0;
  while ((c = Getc(f)) != EOF) {
    switch (++state) {
      case 1: OutChar(table[(c>>2) & 0x3f], g); 
	      break;
      case 2: OutChar(table[((old<<4) & 0x30) | ((c>>4) & 0x0f)], g); 
	      break;
      case 3: OutChar(table[((old<<2) & 0x3c) | ((c>>6) & 0x03)], g);
	      OutChar(table[c & 0x3f], g);
	      state = 0;
	      break;
    }
    old = c;
  }
  switch (state) {
    case 0: /* nothing */;
    case 1: OutChar(table[(old<<4) & 0x30], g);
            OutChar('=', g);
            OutChar('=', g);
	    break;
    case 2: OutChar(table[(old<<2) & 0x3c], g);
            OutChar('=', g);
	    break;
  }
}

static void decode(FILE *f, FILE *g)
{
  static int initialized = 0;
  int c, bits, group, j;

  if (!initialized) {
    initialize_rev_table();    
    initialized = 1;
  }

  group = 0;  j = 18;
  while ((c = Getc(f)) != EOF) {
    if (c != '\n') {
      if (c != '=') {
	bits = rev_table[c];
	group |= bits << j;
      }
      
      j -= 6;
      
      if (j < 0) {
	c = (group&0xff0000) >> 16; if (c) Putc(c, g);
	c = (group&0x00ff00) >> 8;  if (c) Putc(c, g);
	c = (group&0x0000ff);       if (c) Putc(c, g);
	group = 0;
	j = 18;
      }
    }
  }
}

static PRIMITIVE base64_encode(SCM f, SCM g)
{
  ENTER_PRIMITIVE("base64-encode");

  if (!INP(f))  Serror("bad input port", f);
  if (g == UNBOUND)
    g = STk_curr_oport;
  else
    if (!OUTP(g)) Serror("bad output port", g);
  
  encode(PORT_FILE(f), PORT_FILE(g));
  return UNDEFINED;
}

static PRIMITIVE base64_decode(SCM f, SCM g)
{
  ENTER_PRIMITIVE("base64-decode");

  if (!INP(f))  Serror("bad input port", f);
  if (g == UNBOUND)
    g = STk_curr_oport;
  else
    if (!OUTP(g)) Serror("bad output port", g);
  
  decode(PORT_FILE(f), PORT_FILE(g));
  return UNDEFINED;
}

PRIMITIVE STk_init_base64(void)
{
  STk_add_new_primitive("base64-decode",  tc_subr_1_or_2,  base64_decode);
  STk_add_new_primitive("base64-encode",  tc_subr_1_or_2,  base64_encode);
  return UNDEFINED;
}