/* Unicode character output to streams with locale dependent encoding.

   Copyright (C) 2000, 2001 Free Software Foundation, Inc.

   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, 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Written by Bruno Haible <haible@clisp.cons.org>.  */

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

#if HAVE_STDDEF_H
# include <stddef.h>
#endif

#include <stdio.h>
#if HAVE_STRING_H
# include <string.h>
#else
# include <strings.h>
#endif

#include <errno.h>
#ifndef errno
extern int errno;
#endif

#if HAVE_ICONV
# include <iconv.h>
#endif

/* Some systems, like SunOS 4, don't have EILSEQ.  On these systems,
   define EILSEQ to some value other than EINVAL, because our invokers
   may want to distinguish EINVAL from EILSEQ.  */
#ifndef EILSEQ
# define EILSEQ ENOENT
#endif
#ifndef ENOTSUP
# define ENOTSUP EINVAL
#endif

#if HAVE_LANGINFO_CODESET && ! USE_INCLUDED_LIBINTL
# include <langinfo.h>
#endif

#include "unicodeio.h"

/* When we pass a Unicode character to iconv(), we must pass it in a
   suitable encoding. The standardized Unicode encodings are
   UTF-8, UCS-2, UCS-4, UTF-16, UTF-16BE, UTF-16LE, UTF-7.
   UCS-2 supports only characters up to \U0000FFFF.
   UTF-16 and variants support only characters up to \U0010FFFF.
   UTF-7 is way too complex and not supported by glibc-2.1.
   UCS-4 specification leaves doubts about endianness and byte order
   mark. glibc currently interprets it as big endian without byte order
   mark, but this is not backed by an RFC.
   So we use UTF-8. It supports characters up to \U7FFFFFFF and is
   unambiguously defined.  */

/* Stores the UTF-8 representation of the Unicode character wc in r[0..5].
   Returns the number of bytes stored, or -1 if wc is out of range.  */
static int
utf8_wctomb (unsigned char *r, unsigned int wc)
{
  int count;

  if (wc < 0x80)
    count = 1;
  else if (wc < 0x800)
    count = 2;
  else if (wc < 0x10000)
    count = 3;
  else if (wc < 0x200000)
    count = 4;
  else if (wc < 0x4000000)
    count = 5;
  else if (wc <= 0x7fffffff)
    count = 6;
  else
    return -1;

  switch (count)
    {
      /* Note: code falls through cases! */
      case 6: r[5] = 0x80 | (wc & 0x3f); wc = wc >> 6; wc |= 0x4000000;
      case 5: r[4] = 0x80 | (wc & 0x3f); wc = wc >> 6; wc |= 0x200000;
      case 4: r[3] = 0x80 | (wc & 0x3f); wc = wc >> 6; wc |= 0x10000;
      case 3: r[2] = 0x80 | (wc & 0x3f); wc = wc >> 6; wc |= 0x800;
      case 2: r[1] = 0x80 | (wc & 0x3f); wc = wc >> 6; wc |= 0xc0;
      case 1: r[0] = wc;
    }

  return count;
}

/* Luckily, the encoding's name is platform independent.  */
#define UTF8_NAME "UTF-8"

/* Converts the Unicode character CODE to its multibyte representation
   in the current locale and calls SUCCESS on the resulting byte
   sequence.  If an error occurs, invoke FAILURE instead,
   passing it CODE with errno set appropriately.
   Assumes that the locale doesn't change between two calls.
   Return whatever the SUCCESS or FAILURE returns.  */
int
unicode_to_mb (unsigned int code,
	       int (*success) PARAMS((const char *buf, size_t buflen,
				      void *callback_arg)),
	       int (*failure) PARAMS((unsigned int code,
				      void *callback_arg)),
	       void *callback_arg)
{
  static int initialized;
  static int is_utf8;
#if HAVE_ICONV
  static iconv_t utf8_to_local;
#endif

  char inbuf[6];
  int count;

  if (!initialized)
    {
      const char *charset;

#if USE_INCLUDED_LIBINTL
      extern const char *locale_charset PARAMS ((void));
      charset = locale_charset ();
#else
# if HAVE_LANGINFO_CODESET
      charset = nl_langinfo (CODESET);
# else
      charset = "";
# endif
#endif

      is_utf8 = !strcmp (charset, UTF8_NAME);
#if HAVE_ICONV
      if (!is_utf8)
	{
	  utf8_to_local = iconv_open (charset, UTF8_NAME);
	  if (utf8_to_local == (iconv_t)(-1))
	    {
	      /* For an unknown encoding, assume ASCII.  */
	      utf8_to_local = iconv_open ("ASCII", UTF8_NAME);
	      if (utf8_to_local == (iconv_t)(-1))
		return failure (code, callback_arg);
	    }
	}
#endif
      initialized = 1;
    }

  /* Convert the character to UTF-8.  */
  count = utf8_wctomb ((unsigned char *) inbuf, code);
  if (count < 0)
    {
      errno = EILSEQ;
      return failure (code, callback_arg);
    }

  if (is_utf8)
    {
      return success (inbuf, count, callback_arg);
    }
  else
    {
#if HAVE_ICONV
      char outbuf[25];
      const char *inptr;
      size_t inbytesleft;
      char *outptr;
      size_t outbytesleft;
      size_t res;

      inptr = inbuf;
      inbytesleft = count;
      outptr = outbuf;
      outbytesleft = sizeof (outbuf);

      /* Convert the character from UTF-8 to the locale's charset.  */
      res = iconv (utf8_to_local,
		   (ICONV_CONST char **)&inptr, &inbytesleft,
		   &outptr, &outbytesleft);
      if (inbytesleft > 0 || res == (size_t)(-1)
	  /* Irix iconv() inserts a NUL byte if it cannot convert. */
# if !defined _LIBICONV_VERSION && (defined sgi || defined __sgi)
	  || (res > 0 && code != 0 && outptr - outbuf == 1 && *outbuf == '\0')
# endif
         )
	{
	  if (res != (size_t)(-1))
	    errno = EILSEQ;
	  return failure (code, callback_arg);
	}

      /* Avoid glibc-2.1 bug and Solaris 2.7 bug.  */
# if defined _LIBICONV_VERSION \
    || !((__GLIBC__ - 0 == 2 && __GLIBC_MINOR__ - 0 <= 1) || defined __sun)

      /* Get back to the initial shift state.  */
      res = iconv (utf8_to_local, NULL, NULL, &outptr, &outbytesleft);
      if (res == (size_t)(-1))
	return failure (code, callback_arg);
# endif

      return success (outbuf, outptr - outbuf, callback_arg);
#else
      errno = ENOTSUP;
      return failure (code, callback_arg);
#endif
    }
}

/* Simple success callback that outputs the converted string.
   The STREAM is passed as callback_arg.  */
int
print_unicode_success (const char *buf, size_t buflen, void *callback_arg)
{
  FILE *stream = (FILE *) callback_arg;

  return fwrite (buf, 1, buflen, stream) == 0 ? -1 : 0;
}

/* Simple failure callback that prints an ASCII representation, using
   the same notation as C99 strings.  */
int
print_unicode_failure (unsigned int code, void *callback_arg)
{
  int e = errno;
  FILE *stream = callback_arg;
  
  fprintf (stream, code < 0x10000 ? "\\u%04X" : "\\U%08X", code);
  errno = e;
  return -1;
}

/* Outputs the Unicode character CODE to the output stream STREAM.
   Returns zero if successful, -1 (setting errno) otherwise.
   Assumes that the locale doesn't change between two calls.  */
int
print_unicode_char (FILE *stream, unsigned int code)
{
  return unicode_to_mb (code, print_unicode_success, print_unicode_failure,
			stream);
}