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#include	<u.h>
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#include	<libc.h>
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#define Bit(i) (7-(i))
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/* N 0's preceded by i 1's, T(Bit(2)) is 1100 0000 */
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#define T(i) (((1 << (Bit(i)+1))-1) ^ 0xFF)
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/* 0000 0000 0000 0111 1111 1111 */
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#define	RuneX(i) ((1 << (Bit(i) + ((i)-1)*Bitx))-1)
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enum
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{
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	Bitx	= Bit(1),
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	Tx	= T(1),			/* 1000 0000 */
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	Rune1 = (1<<(Bit(0)+0*Bitx))-1,	/* 0000 0000 0000 0000 0111 1111 */
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	Maskx	= (1<<Bitx)-1,		/* 0011 1111 */
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	Testx	= Maskx ^ 0xFF,		/* 1100 0000 */
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	SurrogateMin	= 0xD800,
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	SurrogateMax	= 0xDFFF,
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	Bad	= Runeerror,
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};
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int
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chartorune(Rune *rune, char *str)
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{
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	int c[UTFmax], i;
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	Rune l;
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	/*
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	 * N character sequence
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	 *	00000-0007F => T1
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	 *	00080-007FF => T2 Tx
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	 *	00800-0FFFF => T3 Tx Tx
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	 *	10000-10FFFF => T4 Tx Tx Tx
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	 */
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	c[0] = *(uchar*)(str);
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	if(c[0] < Tx){
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		*rune = c[0];
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		return 1;
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	}
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	l = c[0];
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	for(i = 1; i < UTFmax; i++) {
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		c[i] = *(uchar*)(str+i);
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		c[i] ^= Tx;
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		if(c[i] & Testx)
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			goto bad;
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		l = (l << Bitx) | c[i];
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		if(c[0] < T(i + 2)) {
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			l &= RuneX(i + 1);
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			if(i == 1) {
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				if(c[0] < T(2) || l <= Rune1)
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					goto bad;
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			} else if(l <= RuneX(i) || l > Runemax)
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				goto bad;
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			if (i == 2 && SurrogateMin <= l && l <= SurrogateMax)
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				goto bad;
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			*rune = l;
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			return i + 1;
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		}
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	}
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	/*
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	 * bad decoding
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	 */
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bad:
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	*rune = Bad;
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	return 1;
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}
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int
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runetochar(char *str, Rune *rune)
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{
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	int i, j;
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	Rune c;
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	c = *rune;
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	if(c <= Rune1) {
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		str[0] = c;
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		return 1;
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	}
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	/*
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	 * one character sequence
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	 *	00000-0007F => 00-7F
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	 * two character sequence
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	 *	0080-07FF => T2 Tx
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	 * three character sequence
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	 *	0800-FFFF => T3 Tx Tx
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	 * four character sequence (21-bit value)
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	 *     10000-1FFFFF => T4 Tx Tx Tx
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	 * If the Rune is out of range or a surrogate half,
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	 * convert it to the error rune.
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	 * Do this test when i==3 because the error rune encodes to three bytes.
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	 * Doing it earlier would duplicate work, since an out of range
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	 * Rune wouldn't have fit in one or two bytes.
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	 */
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	for(i = 2; i < UTFmax + 1; i++){
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		if(i == 3){
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			if(c > Runemax)
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				c = Runeerror;
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			if(SurrogateMin <= c && c <= SurrogateMax)
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				c = Runeerror;
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		}
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		if (c <= RuneX(i) || i == UTFmax ) {
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			str[0] = T(i) |  (c >> (i - 1)*Bitx);
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			for(j = 1; j < i; j++)
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				str[j] = Tx | ((c >> (i - j - 1)*Bitx) & Maskx);
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			return i;
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		}
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	}
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	return UTFmax;
117 
}
118 
 
119 
int
120 
runelen(long c)
121 
{
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	Rune rune;
123 
	char str[10];
124 
 
125 
	rune = c;
126 
	return runetochar(str, &rune);
127 
}
128 
 
129 
int
130 
runenlen(Rune *r, int nrune)
131 
{
132 
	int nb, i;
133 
	Rune c;
134 
 
135 
	nb = 0;
136 
	while(nrune--) {
137 
		c = *r++;
138 
		if(c <= Rune1){
139 
			nb++;
140 
		} else {
141 
			for(i = 2; i < UTFmax + 1; i++)
142 
				if(c <= RuneX(i) || i == UTFmax){
143 
					nb += i;
144 
					break;
145 
				}
146 
		}
147 
	}
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	return nb;
149 
}
150 
 
151 
int
152 
fullrune(char *str, int n)
153 
{
154 
	int  i;
155 
	Rune c;
156 
 
157 
	if(n <= 0)
158 
		return 0;
159 
	c = *(uchar*)str;
160 
	if(c < Tx)
161 
		return 1;
162 
	for(i = 3; i < UTFmax + 1; i++)
163 
		if(c < T(i))
164 
			return n >= i - 1;
165 
	return n >= UTFmax;
166 
}