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// Emacs style mode select -*- C++ -*-
//-----------------------------------------------------------------------------
//
// Copyright(C) 2012 Simon Howard
//
// 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 <stdlib.h>
#include <string.h>
#include "txt_utf8.h"
// Encode a Unicode character as UTF-8, storing it in the buffer 'p'
// and returning the new, incremented position.
char *TXT_EncodeUTF8(char *p, unsigned int c)
{
if (c < 0x80) // 1 character (ASCII):
{
p[0] = c;
return p + 1;
}
else if (c < 0x800) // 2 character:
{
p[0] = 0xc0 | (c >> 6);
p[1] = 0x80 | (c & 0x3f);
return p + 2;
}
else if (c < 0x10000) // 3 chacater:
{
p[0] = 0xe0 | (c >> 12);
p[1] = 0x80 | ((c >> 6) & 0x3f);
p[2] = 0x80 | (c & 0x3f);
return p + 3;
}
else if (c < 0x200000) // 4 character:
{
p[0] = 0xf0 | (c >> 18);
p[1] = 0x80 | ((c >> 12) & 0x3f);
p[2] = 0x80 | ((c >> 6) & 0x3f);
p[3] = 0x80 | (c & 0x3f);
return p + 4;
}
else
{
// Too big!
return p;
}
}
// Decode UTF-8 character, incrementing *ptr over the decoded bytes.
unsigned int TXT_DecodeUTF8(const char **ptr)
{
const char *p = *ptr;
unsigned int c;
// UTF-8 decode.
if ((*p & 0x80) == 0) // 1 character (ASCII):
{
c = *p;
*ptr += 1;
}
else if ((p[0] & 0xe0) == 0xc0 // 2 character:
&& (p[1] & 0xc0) == 0x80)
{
c = ((p[0] & 0x1f) << 6)
| (p[1] & 0x3f);
*ptr += 2;
}
else if ((p[0] & 0xf0) == 0xe0 // 3 character:
&& (p[1] & 0xc0) == 0x80
&& (p[2] & 0xc0) == 0x80)
{
c = ((p[0] & 0x0f) << 12)
| ((p[1] & 0x3f) << 6)
| (p[2] & 0x3f);
*ptr += 3;
}
else if ((p[0] & 0xf8) == 0xf0 // 4 character:
&& (p[1] & 0xc0) == 0x80
&& (p[2] & 0xc0) == 0x80
&& (p[3] & 0xc0) == 0x80)
{
c = ((p[0] & 0x07) << 18)
| ((p[1] & 0x3f) << 12)
| ((p[2] & 0x3f) << 6)
| (p[3] & 0x3f);
*ptr += 4;
}
else
{
// Decode failure.
// Don't bother with 5/6 byte sequences.
c = 0;
}
return c;
}
// Count the number of characters in a UTF-8 string.
unsigned int TXT_UTF8_Strlen(const char *s)
{
const char *p;
unsigned int result = 0;
unsigned int c;
for (p = s; *p != '\0';)
{
c = TXT_DecodeUTF8(&p);
if (c == 0)
{
break;
}
++result;
}
return result;
}
// Skip past the first n characters in a UTF-8 string.
char *TXT_UTF8_SkipChars(const char *s, unsigned int n)
{
unsigned int i;
const char *p;
p = s;
for (i = 0; i < n; ++i)
{
if (TXT_DecodeUTF8(&p) == 0)
{
break;
}
}
return (char *) p;
}
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