a

libc/rune.c

@@ -0,0 +1,162 @@
+#include	<u.h>
+#include	<libc.h>
+
+enum
+{
+	Bit1	= 7,
+	Bitx	= 6,
+	Bit2	= 5,
+	Bit3	= 4,
+	Bit4	= 3,
+
+	T1	= ((1<<(Bit1+1))-1) ^ 0xFF,	/* 0000 0000 */
+	Tx	= ((1<<(Bitx+1))-1) ^ 0xFF,	/* 1000 0000 */
+	T2	= ((1<<(Bit2+1))-1) ^ 0xFF,	/* 1100 0000 */
+	T3	= ((1<<(Bit3+1))-1) ^ 0xFF,	/* 1110 0000 */
+	T4	= ((1<<(Bit4+1))-1) ^ 0xFF,	/* 1111 0000 */
+
+	Rune1	= (1<<(Bit1+0*Bitx))-1,		/* 0000 0000 0111 1111 */
+	Rune2	= (1<<(Bit2+1*Bitx))-1,		/* 0000 0111 1111 1111 */
+	Rune3	= (1<<(Bit3+2*Bitx))-1,		/* 1111 1111 1111 1111 */
+
+	Maskx	= (1<<Bitx)-1,			/* 0011 1111 */
+	Testx	= Maskx ^ 0xFF,			/* 1100 0000 */
+
+	Bad	= Runeerror,
+};
+
+int
+chartorune(Rune *rune, char *str)
+{
+	int c, c1, c2;
+	long l;
+
+	/*
+	 * one character sequence
+	 *	00000-0007F => T1
+	 */
+	c = *(uchar*)str;
+	if(c < Tx) {
+		*rune = c;
+		return 1;
+	}
+
+	/*
+	 * two character sequence
+	 *	0080-07FF => T2 Tx
+	 */
+	c1 = *(uchar*)(str+1) ^ Tx;
+	if(c1 & Testx)
+		goto bad;
+	if(c < T3) {
+		if(c < T2)
+			goto bad;
+		l = ((c << Bitx) | c1) & Rune2;
+		if(l <= Rune1)
+			goto bad;
+		*rune = l;
+		return 2;
+	}
+
+	/*
+	 * three character sequence
+	 *	0800-FFFF => T3 Tx Tx
+	 */
+	c2 = *(uchar*)(str+2) ^ Tx;
+	if(c2 & Testx)
+		goto bad;
+	if(c < T4) {
+		l = ((((c << Bitx) | c1) << Bitx) | c2) & Rune3;
+		if(l <= Rune2)
+			goto bad;
+		*rune = l;
+		return 3;
+	}
+
+	/*
+	 * bad decoding
+	 */
+bad:
+	*rune = Bad;
+	return 1;
+}
+
+int
+runetochar(char *str, Rune *rune)
+{
+	long c;
+
+	/*
+	 * one character sequence
+	 *	00000-0007F => 00-7F
+	 */
+	c = *rune;
+	if(c <= Rune1) {
+		str[0] = c;
+		return 1;
+	}
+
+	/*
+	 * two character sequence
+	 *	0080-07FF => T2 Tx
+	 */
+	if(c <= Rune2) {
+		str[0] = T2 | (c >> 1*Bitx);
+		str[1] = Tx | (c & Maskx);
+		return 2;
+	}
+
+	/*
+	 * three character sequence
+	 *	0800-FFFF => T3 Tx Tx
+	 */
+	str[0] = T3 |  (c >> 2*Bitx);
+	str[1] = Tx | ((c >> 1*Bitx) & Maskx);
+	str[2] = Tx |  (c & Maskx);
+	return 3;
+}
+
+int
+runelen(long c)
+{
+	Rune rune;
+	char str[10];
+
+	rune = c;
+	return runetochar(str, &rune);
+}
+
+int
+runenlen(Rune *r, int nrune)
+{
+	int nb, c;
+
+	nb = 0;
+	while(nrune--) {
+		c = *r++;
+		if(c <= Rune1)
+			nb++;
+		else
+		if(c <= Rune2)
+			nb += 2;
+		else
+			nb += 3;
+	}
+	return nb;
+}
+
+int
+fullrune(char *str, int n)
+{
+	int c;
+
+	if(n > 0) {
+		c = *(uchar*)str;
+		if(c < Tx)
+			return 1;
+		if(n > 1)
+			if(c < T3 || n > 2)
+				return 1;
+	}
+	return 0;
+}