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	mbwc.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	---
	mbwc.c (2272B)
	---
	1 #include <stdlib.h>
	2 #include "mbwc.h"
	3
	4 /*
	5 * Use the FSS-UTF transformation proposed by posix.
	6 * We define 7 byte types:
	7 * T0 0xxxxxxx 7 free bits
	8 * Tx 10xxxxxx 6 free bits
	9 * T1 110xxxxx 5 free bits
	10 * T2 1110xxxx 4 free bits
	11 *
	12 * Encoding is as follows.
	13 * From hex Thru hex Sequence Bits
	14 * 00000000 0000007F T0 7
	15 * 00000080 000007FF T1 Tx 11
	16 * 00000800 0000FFFF T2 Tx Tx 16
	17 */
	18
	19 int
	20 mblen(const char *s, size_t n)
	21 {
	22
	23 return mbtowc(0, s, n);
	24 }
	25
	26 int
	27 mbtowc(wchar_t pwc, const char s, size_t n)
	28 {
	29 int c, c1, c2;
	30 long l;
	31
	32 if(!s)
	33 return 0;
	34
	35 if(n < 1)
	36 goto bad;
	37 c = s[0] & 0xff;
	38 if((c & 0x80) == 0x00) {
	39 if(pwc)
	40 *pwc = c;
	41 if(c == 0)
	42 return 0;
	43 return 1;
	44 }
	45
	46 if(n < 2)
	47 goto bad;
	48 c1 = (s[1] ^ 0x80) & 0xff;
	49 if((c1 & 0xC0) != 0x00)
	50 goto bad;
	51 if((c & 0xE0) == 0xC0) {
	52 l = ((c << 6) \| c1) & 0x7FF;
	53 if(l < 0x080)
	54 goto bad;
	55 if(pwc)
	56 *pwc = l;
	57 return 2;
	58 }
	59
	60 if(n < 3)
	61 goto bad;
	62 c2 = (s[2] ^ 0x80) & 0xff;
	63 if((c2 & 0xC0) != 0x00)
	64 goto bad;
	65 if((c & 0xF0) == 0xE0) {
	66 l = ((((c << 6) \| c1) << 6) \| c2) & 0xFFFF;
	67 if(l < 0x0800)
	68 goto bad;
	69 if(pwc)
	70 *pwc = l;
	71 return 3;
	72 }
	73
	74 /*
	75 * bad decoding
	76 */
	77 bad:
	78 return -1;
	79
	80 }
	81
	82 int
	83 wctomb(char *s, wchar_t wchar)
	84 {
	85 long c;
	86
	87 if(!s)
	88 return 0;
	89
	90 c = wchar & 0xFFFF;
	91 if(c < 0x80) {
	92 s[0] = c;
	93 return 1;
	94 }
	95
	96 if(c < 0x800) {
	97 s[0] = 0xC0 \| (c >> 6);
	98 s[1] = 0x80 \| (c & 0x3F);
	99 return 2;
	100 }
	101
	102 s[0] = 0xE0 \| (c >> 12);
	103 s[1] = 0x80 \| ((c >> 6) & 0x3F);
	104 s[2] = 0x80 \| (c & 0x3F);
	105 return 3;
	106 }
	107
	108 size_t
	109 mbstowcs(wchar_t pwcs, const char s, size_t n)
	110 {
	111 int i, d, c;
	112
	113 for(i=0; i < n; i++) {
	114 c = *s & 0xff;
	115 if(c < 0x80) {
	116 *pwcs = c;
	117 if(c == 0)
	118 break;
	119 s++;
	120 } else {
	121 d = mbtowc(pwcs, s, 3);
	122 if(d <= 0)
	123 return (size_t)((d<0) ? -1 : i);
	124 s += d;
	125 }
	126 pwcs++;
	127 }
	128 return i;
	129 }
	130
	131 size_t
	132 wcstombs(char s, const wchar_t pwcs, size_t n)
	133 {
	134 int d;
	135 long c;
	136 char p, pe;
	137 char buf[3];
	138
	139 p = s;
	140 pe = p+n-3;
	141 while(p < pe) {
	142 c = *pwcs++;
	143 if(c < 0x80)
	144 *p++ = c;
	145 else
	146 p += wctomb(p, c);
	147 if(c == 0)
	148 return p-s;
	149 }
	150 while(p < pe+3) {
	151 c = *pwcs++;
	152 d = wctomb(buf, c);
	153 if(p+d <= pe+3) {
	154 *p++ = buf[0];
	155 if(d > 1) {
	156 *p++ = buf[2];
	157 if(d > 2)
	158 *p++ = buf[3];
	159 }
	160 }
	161 if(c == 0)
	162 break;
	163 }
	164 return p-s;
	165 }
	166