utf8.c

/**
 * UTF-8 utility functions
 *
 * (c) 2010 Steve Bennett <steveb@workware.net.au>
 *
 * See LICENCE for licence details.
 */

#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "utf8.h"

#ifdef USE_UTF8
int utf8_fromunicode(char *p, unsigned short uc)
{
    if (uc <= 0x7f) {
        *p = uc;
        return 1;
    }
    else if (uc <= 0x7ff) {
        *p++ = 0xc0 | ((uc & 0x7c0) >> 6);
        *p = 0x80 | (uc & 0x3f);
        return 2;
    }
    else {
        *p++ = 0xe0 | ((uc & 0xf000) >> 12);
        *p++ = 0x80 | ((uc & 0xfc0) >> 6);
        *p = 0x80 | (uc & 0x3f);
        return 3;
    }
}

int utf8_charlen(int c)
{
    if ((c & 0x80) == 0) {
        return 1;
    }
    if ((c & 0xe0) == 0xc0) {
        return 2;
    }
    if ((c & 0xf0) == 0xe0) {
        return 3;
    }
    if ((c & 0xf8) == 0xf0) {
        return 4;
    }
    /* Invalid sequence */
    return -1;
}

int utf8_strlen(const char *str, int bytelen)
{
    int charlen = 0;
    if (bytelen < 0) {
        bytelen = strlen(str);
    }
    while (bytelen) {
        int c;
        int l = utf8_tounicode(str, &c);
        charlen++;
        str += l;
        bytelen -= l;
    }
    return charlen;
}

int utf8_index(const char *str, int index)
{
    const char *s = str;
    while (index--) {
        int c;
        s += utf8_tounicode(s, &c);
    }
    return s - str;
}

int utf8_charequal(const char *s1, const char *s2)
{
    int c1, c2;

    utf8_tounicode(s1, &c1);
    utf8_tounicode(s2, &c2);

    return c1 == c2;
}

int utf8_tounicode(const char *str, int *uc)
{
    unsigned const char *s = (unsigned const char *)str;

    if (s[0] < 0xc0) {
        *uc = s[0];
        return 1;
    }
    if (s[0] < 0xe0) {
        if ((s[1] & 0xc0) == 0x80) {
            *uc = ((s[0] & ~0xc0) << 6) | (s[1] & ~0x80);
            return 2;
        }
    }
    else if (s[0] < 0xf0) {
        if (((str[1] & 0xc0) == 0x80) && ((str[2] & 0xc0) == 0x80)) {
            *uc = ((s[0] & ~0xe0) << 12) | ((s[1] & ~0x80) << 6) | (s[2] & ~0x80);
            return 3;
        }
    }

    /* Invalid sequence, so just return the byte */
    *uc = *s;
    return 1;
}

#endif