mad_utf8.c

这个程序实现了FLUTE协议

/* $Author: peltotal $ $Date: 2006/02/17 08:07:17 $ $Revision: 1.2 $ */
/*
 *   MAD-FLUTELIB: Implementation of FLUTE protocol.
 *   Copyright (c) 2003-2006 TUT - Tampere University of Technology
 *   main authors/contacts: [e-mail] and [e-mail]
 *
 *   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "flute_inc.h"

/* Map from the most-significant 6 bits of the first byte to the total number of bytes in a UTF-8 character. */

static char UTF8_2_ISO_8859_1_len[] =
  {
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* erroneous */
    2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 5, 6
  };

static char UTF8_2_ISO_8859_1_mask[] = {0x3F, 0x7F, 0x1F, 0x0F, 0x07, 0x03, 0x01};

/* Convert a UTF-8 string to a ISO-8859-1 MultiByte string.
   No more than 'count' bytes will be written to the output buffer.
   Return the size of the converted string in bytes, excl null terminator. */

int x_utf8s_to_iso_8859_1s( char *mbstr, const char *utf8str, size_t count ) {
  
  int res = 0;

  while (*utf8str != '\0')
    {
      int len = UTF8_2_ISO_8859_1_len[(*utf8str >> 2) & 0x3F];
      unsigned long u = *utf8str & UTF8_2_ISO_8859_1_mask[len];
      
      /* erroneous */
      if (len == 0)
	len = 5;
      
      for (++utf8str; --len > 0 && (*utf8str != '\0'); ++utf8str)
	{
	  /* be sure this is not an unexpected start of a new character */
	  if ((*utf8str & 0xC0) != 0x80)
	    break;
	  
	  u = (u << 6) | (*utf8str & 0x3F);
	}
      
      if (mbstr != 0 && count != 0)
	{
	  /* be sure there is enough space left in the destination buffer */
	  if (res >= (int)count)
	    return res;
	  
	  /* add the mapped character to the destination string or '?' (0x1A, SUB) if character */
	  /* can't be represented in ISO-8859-1 */
	  *mbstr++ = (u <= 0xFF ? (char)u : '?');
	}
      ++res;
    }
  
  /* add the terminating null character */
  if (mbstr != 0 && count != 0)
    {
      // be sure there is enough space left in the destination buffer
      if (res >= (int)count)
	return res;
      *mbstr = 0;
    }
  
  return res;
}

/* Convert a ISO-8859-1 MultiByte string to a UTF-8 string.
   No more than 'count' bytes will be written to the output buffer.
   Return the size of the converted string in bytes, excl null terminator. */

int x_iso_8859_1s_to_utf8s(char *utf8str, const char *mbstr, size_t count) {
  
  int res = 0;
  
  /* loop until we reach the end of the mb string */
  for (; *mbstr != '\0'; ++mbstr)
    {
      /* the character needs no mapping if the highest bit is not set */
      if ((*mbstr & 0x80) == 0) 
	{
	  if (utf8str != 0 && count != 0)
	    {
	      /* be sure there is enough space left in the destination buffer */
	      if (res >= (int)count)
		return res;
	      
	      *utf8str++ = *mbstr;
	    }
	  ++res;
	}
      
      /* otherwise mapping is necessary */
      else
	{
	  if (utf8str != 0 && count != 0)
	    {
	      /* be sure there is enough space left in the destination buffer */
	      if (res+1 >= (int)count)
		return res;
	      
	      *utf8str++ = (0xC0 | (0x03 & (*mbstr >> 6)));
	      *utf8str++ = (0x80 | (0x3F & *mbstr));
	    }
	  res += 2;
	}
    }
  
  /* add the terminating null character */
  if (utf8str != 0 && count != 0)
    {
      /* be sure there is enough space left in the destination buffer */
      if (res >= (int)count)
	return res;
      *utf8str = 0;
    }
  
  return res;
}