eqn: add working mbtowc and wctomb

Fixes UTF-8 input files.

R=rsc
http://codereview.appspot.com/4132042

src/cmd/eqn/mbwc.c

@@ -0,0 +1,165 @@
+#include <stdlib.h>
+
+/*
+ * Use the FSS-UTF transformation proposed by posix.
+ *	We define 7 byte types:
+ *	T0	0xxxxxxx	7 free bits
+ *	Tx	10xxxxxx	6 free bits
+ *	T1	110xxxxx	5 free bits
+ *	T2	1110xxxx	4 free bits
+ *
+ *	Encoding is as follows.
+ *	From hex	Thru hex	Sequence		Bits
+ *	00000000	0000007F	T0			7
+ *	00000080	000007FF	T1 Tx			11
+ *	00000800	0000FFFF	T2 Tx Tx		16
+ */
+
+int
+mblen(const char *s, size_t n)
+{
+
+	return mbtowc(0, s, n);
+}
+
+int
+mbtowc(wchar_t *pwc, const char *s, size_t n)
+{
+	int c, c1, c2;
+	long l;
+
+	if(!s)
+		return 0;
+
+	if(n < 1)
+		goto bad;
+	c = s[0] & 0xff;
+	if((c & 0x80) == 0x00) {
+		if(pwc)
+			*pwc = c;
+		if(c == 0)
+			return 0;
+		return 1;
+	}
+
+	if(n < 2)
+		goto bad;
+	c1 = (s[1] ^ 0x80) & 0xff;
+	if((c1 & 0xC0) != 0x00)
+		goto bad;
+	if((c & 0xE0) == 0xC0) {
+		l = ((c << 6) | c1) & 0x7FF;
+		if(l < 0x080)
+			goto bad;
+		if(pwc)
+			*pwc = l;
+		return 2;
+	}
+
+	if(n < 3)
+		goto bad;
+	c2 = (s[2] ^ 0x80) & 0xff;
+	if((c2 & 0xC0) != 0x00)
+		goto bad;
+	if((c & 0xF0) == 0xE0) {
+		l = ((((c << 6) | c1) << 6) | c2) & 0xFFFF;
+		if(l < 0x0800)
+			goto bad;
+		if(pwc)
+			*pwc = l;
+		return 3;
+	}
+
+	/*
+	 * bad decoding
+	 */
+bad:
+	return -1;
+
+}
+
+int
+wctomb(char *s, wchar_t wchar)
+{
+	long c;
+
+	if(!s)
+		return 0;
+
+	c = wchar & 0xFFFF;
+	if(c < 0x80) {
+		s[0] = c;
+		return 1;
+	}
+
+	if(c < 0x800) {
+		s[0] = 0xC0 | (c >> 6);
+		s[1] = 0x80 | (c & 0x3F);
+		return 2;
+	}
+
+	s[0] = 0xE0 |  (c >> 12);
+	s[1] = 0x80 | ((c >> 6) & 0x3F);
+	s[2] = 0x80 |  (c & 0x3F);
+	return 3;
+}
+
+size_t
+mbstowcs(wchar_t *pwcs, const char *s, size_t n)
+{
+	int i, d, c;
+
+	for(i=0; i < n; i++) {
+		c = *s & 0xff;
+		if(c < 0x80) {
+			*pwcs = c;
+			if(c == 0)
+				break;
+			s++;
+		} else {
+			d = mbtowc(pwcs, s, 3);
+			if(d <= 0)
+				return (size_t)((d<0) ? -1 : i);
+			s += d;
+		}
+		pwcs++;
+	}
+	return i;
+}
+
+size_t
+wcstombs(char *s, const wchar_t *pwcs, size_t n)
+{
+	int d;
+	long c;
+	char *p, *pe;
+	char buf[3];
+
+	p = s;
+	pe = p+n-3;
+	while(p < pe) {
+		c = *pwcs++;
+		if(c < 0x80)
+			*p++ = c;
+		else
+			p += wctomb(p, c);
+		if(c == 0)
+			return p-s;
+	}
+	while(p < pe+3) {
+		c = *pwcs++;
+		d = wctomb(buf, c);
+		if(p+d <= pe+3) {
+			*p++ = buf[0];
+			if(d > 1) {
+				*p++ = buf[1];
+				if(d > 2)
+					*p++ = buf[2];
+			}
+		}
+		if(c == 0)
+			break;
+	}
+	return p-s;
+}
+

src/cmd/eqn/mkfile

@@ -15,6 +15,7 @@ OFILES=main.$O\
 	lookup.$O\
 	mark.$O\
 	matrix.$O\
+	mbwc.$O\
 	move.$O\
 	over.$O\
 	paren.$O\