1 #include <stdlib.h>
2 
3 /*
4  * Use the FSS-UTF transformation proposed by posix.
5  *	We define 7 byte types:
6  *	T0	0xxxxxxx	7 free bits
7  *	Tx	10xxxxxx	6 free bits
8  *	T1	110xxxxx	5 free bits
9  *	T2	1110xxxx	4 free bits
10  *
11  *	Encoding is as follows.
12  *	From hex	Thru hex	Sequence		Bits
13  *	00000000	0000007F	T0			7
14  *	00000080	000007FF	T1 Tx			11
15  *	00000800	0000FFFF	T2 Tx Tx		16
16  */
17 
18 int
19 mblen(const char *s, size_t n)
20 {
21 
22 	return mbtowc(0, s, n);
23 }
24 
25 int
26 mbtowc(wchar_t *pwc, const char *s, size_t n)
27 {
28 	int c, c1, c2;
29 	long l;
30 
31 	if(!s)
32 		return 0;
33 
34 	if(n < 1)
35 		goto bad;
36 	c = s[0] & 0xff;
37 	if((c & 0x80) == 0x00) {
38 		if(pwc)
39 			*pwc = c;
40 		if(c == 0)
41 			return 0;
42 		return 1;
43 	}
44 
45 	if(n < 2)
46 		goto bad;
47 	c1 = (s[1] ^ 0x80) & 0xff;
48 	if((c1 & 0xC0) != 0x00)
49 		goto bad;
50 	if((c & 0xE0) == 0xC0) {
51 		l = ((c << 6) | c1) & 0x7FF;
52 		if(l < 0x080)
53 			goto bad;
54 		if(pwc)
55 			*pwc = l;
56 		return 2;
57 	}
58 
59 	if(n < 3)
60 		goto bad;
61 	c2 = (s[2] ^ 0x80) & 0xff;
62 	if((c2 & 0xC0) != 0x00)
63 		goto bad;
64 	if((c & 0xF0) == 0xE0) {
65 		l = ((((c << 6) | c1) << 6) | c2) & 0xFFFF;
66 		if(l < 0x0800)
67 			goto bad;
68 		if(pwc)
69 			*pwc = l;
70 		return 3;
71 	}
72 
73 	/*
74 	 * bad decoding
75 	 */
76 bad:
77 	return -1;
78 
79 }
80 
81 int
82 wctomb(char *s, wchar_t wchar)
83 {
84 	long c;
85 
86 	if(!s)
87 		return 0;
88 
89 	c = wchar & 0xFFFF;
90 	if(c < 0x80) {
91 		s[0] = c;
92 		return 1;
93 	}
94 
95 	if(c < 0x800) {
96 		s[0] = 0xC0 | (c >> 6);
97 		s[1] = 0x80 | (c & 0x3F);
98 		return 2;
99 	}
100 
101 	s[0] = 0xE0 |  (c >> 12);
102 	s[1] = 0x80 | ((c >> 6) & 0x3F);
103 	s[2] = 0x80 |  (c & 0x3F);
104 	return 3;
105 }
106 
107 size_t
108 mbstowcs(wchar_t *pwcs, const char *s, size_t n)
109 {
110 	int i, d, c;
111 
112 	for(i=0; i < n; i++) {
113 		c = *s & 0xff;
114 		if(c < 0x80) {
115 			*pwcs = c;
116 			if(c == 0)
117 				break;
118 			s++;
119 		} else {
120 			d = mbtowc(pwcs, s, 3);
121 			if(d <= 0)
122 				return (size_t)((d<0) ? -1 : i);
123 			s += d;
124 		}
125 		pwcs++;
126 	}
127 	return i;
128 }
129 
130 size_t
131 wcstombs(char *s, const wchar_t *pwcs, size_t n)
132 {
133 	int d;
134 	long c;
135 	char *p, *pe;
136 	char buf[3];
137 
138 	p = s;
139 	pe = p+n-3;
140 	while(p < pe) {
141 		c = *pwcs++;
142 		if(c < 0x80)
143 			*p++ = c;
144 		else
145 			p += wctomb(p, c);
146 		if(c == 0)
147 			return p-s;
148 	}
149 	while(p < pe+3) {
150 		c = *pwcs++;
151 		d = wctomb(buf, c);
152 		if(p+d <= pe+3) {
153 			*p++ = buf[0];
154 			if(d > 1) {
155 				*p++ = buf[2];
156 				if(d > 2)
157 					*p++ = buf[3];
158 			}
159 		}
160 		if(c == 0)
161 			break;
162 	}
163 	return p-s;
164 }
165