/* conversion.c - String conversion helper functions.
 * Copyright (C) 2000 Werner Koch (dd9jn)
 * Copyright (C) 2001, 2002, 2003, 2004, 2007, 2009 g10 Code GmbH
 *
 * This file is part of Assuan.
 *
 * Assuan is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * Assuan 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, see <http://www.gnu.org/licenses/>.
 * SPDX-License-Identifier: LGPL-2.1+
 */

#if HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>

#include "assuan-defs.h"
#include "debug.h"


/* Convert the number NR to a hexadecimal string.  Returns the tail
   pointer.  */
static char *
_assuan_bytetohex (int nr, char *str)
{
  static char hexdigits[] = "0123456789abcdef";
  int i;

#define NROFHEXDIGITS 2
  for (i = 0; i < NROFHEXDIGITS; i++)
    {
      int digit = (nr >> (i << 2)) & 0xf;
      *(str++) = hexdigits[digit];
    }
  return str;
}


/* Encode the C formatted string SRC and return the malloc'ed result.  */
char *
_assuan_encode_c_string (assuan_context_t ctx, const char *src)
{
  const unsigned char *istr;
  char *res;
  char *ostr;

  ostr = _assuan_malloc (ctx, 4 * strlen (src) + 1);
  if (! *ostr)
    return NULL;

  res = ostr;

  for (istr = (const unsigned char *) src; *istr; istr++)
    {
      int c = 0;

      switch (*istr)
	{
	case '\r':
	  c = 'r';
	  break;

	case '\n':
	  c = 'n';
	  break;

	case '\f':
	  c = 'f';
	  break;

	case '\v':
	  c = 'v';
	  break;

	case '\b':
	  c = 'b';
	  break;

	default:
	  if ((isascii (*istr) && isprint (*istr)) || (*istr >= 0x80))
	    *(ostr++) = *istr;
	  else
	    {
	      *(ostr++) = '\\';
	      *(ostr++) = 'x';
	      ostr = _assuan_bytetohex (*istr, ostr);
	    }
	}

      if (c)
	{
	  *(ostr++) = '\\';
	  *(ostr++) = c;
	}
    }
  *(ostr) = '\0';

  return res;
}