irssi/src/fe-text/utf8.c

#define UTF8_COMPUTE(Char, Mask, Len)					      \
  if (Char < 128)							      \
    {									      \
      Len = 1;								      \
      Mask = 0x7f;							      \
    }									      \
  else if ((Char & 0xe0) == 0xc0)					      \
    {									      \
      Len = 2;								      \
      Mask = 0x1f;							      \
    }									      \
  else if ((Char & 0xf0) == 0xe0)					      \
    {									      \
      Len = 3;								      \
      Mask = 0x0f;							      \
    }									      \
  else if ((Char & 0xf8) == 0xf0)					      \
    {									      \
      Len = 4;								      \
      Mask = 0x07;							      \
    }									      \
  else if ((Char & 0xfc) == 0xf8)					      \
    {									      \
      Len = 5;								      \
      Mask = 0x03;							      \
    }									      \
  else if ((Char & 0xfe) == 0xfc)					      \
    {									      \
      Len = 6;								      \
      Mask = 0x01;							      \
    }									      \
  else									      \
    Len = -1;

#define UTF8_GET(Result, Chars, Count, Mask, Len)			      \
  (Result) = (Chars)[0] & (Mask);					      \
  for ((Count) = 1; (Count) < (Len); ++(Count))				      \
    {									      \
      if (((Chars)[(Count)] & 0xc0) != 0x80)				      \
	{								      \
	  (Result) = -1;						      \
	  break;							      \
	}								      \
      (Result) <<= 6;							      \
      (Result) |= ((Chars)[(Count)] & 0x3f);				      \
    }

void get_utf8_char(const unsigned char **ptr)
{
	int i, mask = 0, len;
	unsigned int result;
	unsigned char c = (unsigned char) **ptr;

	UTF8_COMPUTE(c, mask, len);
	if (len == -1)
		return;

	UTF8_GET(result, *ptr, i, mask, len);
	if (result == -1)
                return;

        *ptr += len-1;
}