gmqcc/utf8lib.c

#include "gmqcc.h"

static unsigned char utf8_lengths[256] = {
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* ascii characters */
	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,
	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,
	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,
	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, /* 0x80 - 0xBF are within multibyte sequences
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  * they could be interpreted as 2-byte starts but
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  * the codepoint would be < 127
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  *
	0, 0, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  * C0 and C1 would also result in overlong encodings
	2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  */
	3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
	4, 4, 4, 4, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
	/* with F5 the codepoint is above 0x10FFFF,
	 * F8-FB would start 5-byte sequences
	 * FC-FD would start 6-byte sequences
	 * ...
	 */
};

static Uchar utf8_range[5] = {
	1,       /* invalid - let's not allow the creation of 0-bytes :P
	1,        * ascii minimum
	0x80,     * 2-byte minimum
	0x800,    * 3-byte minimum
	0x10000,  * 4-byte minimum */
};

/** Analyze the next character and return various information if requested.
 * @param _s      An utf-8 string.
 * @param _start  Filled with the start byte-offset of the next valid character
 * @param _len    Fileed with the length of the next valid character
 * @param _ch     Filled with the unicode value of the next character
 * @param _maxlen Maximum number of bytes to read from _s
 * @return        Whether or not another valid character is in the string
 */
static bool u8_analyze(const char *_s, size_t *_start, size_t *_len, Uchar *_ch, size_t _maxlen)
{
	const unsigned char *s = (const unsigned char*)_s;
	size_t i, j;
	size_t bits = 0;
	Uchar ch;

	i = 0;
/* findchar: */
	while (i < _maxlen && s[i] && (bits = utf8_lengths[s[i]]) == 0)
		++i;

	if (i >= _maxlen || !s[i]) {
		if (_start) *_start = i;
		if (_len) *_len = 0;
		return false;
	}

	if (bits == 1) { /* ascii */
		if (_start) *_start = i;
		if (_len) *_len = 1;
		if (_ch) *_ch = (Uchar)s[i];
		return true;
	}

	ch = (s[i] & (0xFF >> bits));
	for (j = 1; j < bits; ++j)
	{
		if ( (s[i+j] & 0xC0) != 0x80 )
		{
			i += j;
			/* in gmqcc, invalid / overlong encodings are considered an error
			 * goto findchar;
			 */
			return false;
		}
		ch = (ch << 6) | (s[i+j] & 0x3F);
	}
	if (ch < utf8_range[bits] || ch >= 0x10FFFF)
	{
		/* same: error
		 * i += bits;
		 * goto findchar;
		 */
		return false;
	}

	if (_start)
		*_start = i;
	if (_len)
		*_len = bits;
	if (_ch)
		*_ch = ch;
	return true;
}

/* might come in handy */
size_t u8_strlen(const char *_s)
{
	size_t st, ln;
	size_t len = 0;
	const unsigned char *s = (const unsigned char*)_s;

	while (*s)
	{
		/* ascii char, skip u8_analyze */
		if (*s < 0x80)
		{
			++len;
			++s;
			continue;
		}

		/* invalid, skip u8_analyze */
		if (*s < 0xC2)
		{
			++s;
			continue;
		}

		if (!u8_analyze((const char*)s, &st, &ln, NULL, 0x10))
			break;
		/* valid character, skip after it */
		s += st + ln;
		++len;
	}
	return len;
}

size_t u8_strnlen(const char *_s, size_t n)
{
	size_t st, ln;
	size_t len = 0;
	const unsigned char *s = (const unsigned char*)_s;

	while (*s && n)
	{
		/* ascii char, skip u8_analyze */
		if (*s < 0x80)
		{
			++len;
			++s;
			--n;
			continue;
		}

		/* invalid, skip u8_analyze */
		if (*s < 0xC2)
		{
			++s;
			--n;
			continue;
		}

		if (!u8_analyze((const char*)s, &st, &ln, NULL, n))
			break;
		/* valid character, see if it's still inside the range specified by n: */
		if (n < st + ln)
			return len;
		++len;
		n -= st + ln;
		s += st + ln;
	}
	return len;
}

/* Required for character constants */
Uchar u8_getchar(const char *_s, const char **_end)
{
	size_t st, ln;
	Uchar ch;

	if (!u8_analyze(_s, &st, &ln, &ch, 0x10))
		ch = 0;
	if (_end)
		*_end = _s + st + ln;
	return ch;
}

Uchar u8_getnchar(const char *_s, const char **_end, size_t _maxlen)
{
	size_t st, ln;
	Uchar ch;

	if (!u8_analyze(_s, &st, &ln, &ch, _maxlen))
		ch = 0;
	if (_end)
		*_end = _s + st + ln;
	return ch;
}

/* required for \x{asdf}-like string escape sequences */
int u8_fromchar(Uchar w, char *to, size_t maxlen)
{
	if (maxlen < 1)
		return 0;

	if (!w)
		return 0;

/* We may want an -f flag for this behaviour...
	if (w >= 0xE000)
		w -= 0xE000;
*/

	if (w < 0x80)
	{
		to[0] = (char)w;
		if (maxlen < 2)
			return -1;
		to[1] = 0;
		return 1;
	}
	/* for a little speedup */
	if (w < 0x800)
	{
		if (maxlen < 3)
		{
			to[0] = 0;
			return -1;
		}
		to[2] = 0;
		to[1] = 0x80 | (w & 0x3F); w >>= 6;
		to[0] = 0xC0 | w;
		return 2;
	}
	if (w < 0x10000)
	{
		if (maxlen < 4)
		{
			to[0] = 0;
			return -1;
		}
		to[3] = 0;
		to[2] = 0x80 | (w & 0x3F); w >>= 6;
		to[1] = 0x80 | (w & 0x3F); w >>= 6;
		to[0] = 0xE0 | w;
		return 3;
	}

	/* RFC 3629 */
	if (w <= 0x10FFFF)
	{
		if (maxlen < 5)
		{
			to[0] = 0;
			return -1;
		}
		to[4] = 0;
		to[3] = 0x80 | (w & 0x3F); w >>= 6;
		to[2] = 0x80 | (w & 0x3F); w >>= 6;
		to[1] = 0x80 | (w & 0x3F); w >>= 6;
		to[0] = 0xF0 | w;
		return 4;
	}
	return 0;
}