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	rune.c - 9base - revived minimalist port of Plan 9 userland to Unix
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	rune.c (3963B)
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	1 /*
	2 * The authors of this software are Rob Pike and Ken Thompson.
	3 * Copyright (c) 2002 by Lucent Technologies.
	4 * Permission to use, copy, modify, and distribute this software for any
	5 * purpose without fee is hereby granted, provided that this entire noti…
	6 * is included in all copies of any software which is or includes a copy
	7 * or modification of this software and in all copies of the supporting
	8 * documentation for such software.
	9 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLI…
	10 * WARRANTY. IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES…
	11 * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABI…
	12 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
	13 */
	14 #include <stdarg.h>
	15 #include <string.h>
	16 #include "plan9.h"
	17 #include "utf.h"
	18
	19 enum
	20 {
	21 Bit1 = 7,
	22 Bitx = 6,
	23 Bit2 = 5,
	24 Bit3 = 4,
	25 Bit4 = 3,
	26 Bit5 = 2,
	27
	28 T1 = ((1<<(Bit1+1))-1) ^ 0xFF, /* 0000 0000 */
	29 Tx = ((1<<(Bitx+1))-1) ^ 0xFF, /* 1000 0000 */
	30 T2 = ((1<<(Bit2+1))-1) ^ 0xFF, /* 1100 0000 */
	31 T3 = ((1<<(Bit3+1))-1) ^ 0xFF, /* 1110 0000 */
	32 T4 = ((1<<(Bit4+1))-1) ^ 0xFF, /* 1111 0000 */
	33 T5 = ((1<<(Bit5+1))-1) ^ 0xFF, /* 1111 1000 */
	34
	35 Rune1 = (1<<(Bit1+0Bitx))-1, / 0000 0000…
	36 Rune2 = (1<<(Bit2+1Bitx))-1, / 0000 0000…
	37 Rune3 = (1<<(Bit3+2Bitx))-1, / 0000 0000…
	38 Rune4 = (1<<(Bit4+3Bitx))-1, / 0011 1111…
	39
	40 Maskx = (1<<Bitx)-1, /* 0011 1111 …
	41 Testx = Maskx ^ 0xFF, /* 1100 0000…
	42
	43 Bad = Runeerror
	44 };
	45
	46 int
	47 chartorune(Rune rune, char str)
	48 {
	49 int c, c1, c2, c3;
	50 long l;
	51
	52 /*
	53 * one character sequence
	54 * 00000-0007F => T1
	55 */
	56 c = (uchar)str;
	57 if(c < Tx) {
	58 *rune = c;
	59 return 1;
	60 }
	61
	62 /*
	63 * two character sequence
	64 * 0080-07FF => T2 Tx
	65 */
	66 c1 = (uchar)(str+1) ^ Tx;
	67 if(c1 & Testx)
	68 goto bad;
	69 if(c < T3) {
	70 if(c < T2)
	71 goto bad;
	72 l = ((c << Bitx) \| c1) & Rune2;
	73 if(l <= Rune1)
	74 goto bad;
	75 *rune = l;
	76 return 2;
	77 }
	78
	79 /*
	80 * three character sequence
	81 * 0800-FFFF => T3 Tx Tx
	82 */
	83 c2 = (uchar)(str+2) ^ Tx;
	84 if(c2 & Testx)
	85 goto bad;
	86 if(c < T4) {
	87 l = ((((c << Bitx) \| c1) << Bitx) \| c2) & Rune3;
	88 if(l <= Rune2)
	89 goto bad;
	90 *rune = l;
	91 return 3;
	92 }
	93
	94 /*
	95 * four character sequence
	96 * 10000-10FFFF => T4 Tx Tx Tx
	97 */
	98 if(UTFmax >= 4) {
	99 c3 = (uchar)(str+3) ^ Tx;
	100 if(c3 & Testx)
	101 goto bad;
	102 if(c < T5) {
	103 l = ((((((c << Bitx) \| c1) << Bitx) \| c2) << Bit…
	104 if(l <= Rune3)
	105 goto bad;
	106 if(l > Runemax)
	107 goto bad;
	108 *rune = l;
	109 return 4;
	110 }
	111 }
	112
	113 /*
	114 * bad decoding
	115 */
	116 bad:
	117 *rune = Bad;
	118 return 1;
	119 }
	120
	121 int
	122 runetochar(char str, Rune rune)
	123 {
	124 long c;
	125
	126 /*
	127 * one character sequence
	128 * 00000-0007F => 00-7F
	129 */
	130 c = *rune;
	131 if(c <= Rune1) {
	132 str[0] = c;
	133 return 1;
	134 }
	135
	136 /*
	137 * two character sequence
	138 * 00080-007FF => T2 Tx
	139 */
	140 if(c <= Rune2) {
	141 str[0] = T2 \| (c >> 1*Bitx);
	142 str[1] = Tx \| (c & Maskx);
	143 return 2;
	144 }
	145
	146 /*
	147 * three character sequence
	148 * 00800-0FFFF => T3 Tx Tx
	149 */
	150 if(c > Runemax)
	151 c = Runeerror;
	152 if(c <= Rune3) {
	153 str[0] = T3 \| (c >> 2*Bitx);
	154 str[1] = Tx \| ((c >> 1*Bitx) & Maskx);
	155 str[2] = Tx \| (c & Maskx);
	156 return 3;
	157 }
	158
	159 /*
	160 * four character sequence
	161 * 010000-1FFFFF => T4 Tx Tx Tx
	162 */
	163 str[0] = T4 \| (c >> 3*Bitx);
	164 str[1] = Tx \| ((c >> 2*Bitx) & Maskx);
	165 str[2] = Tx \| ((c >> 1*Bitx) & Maskx);
	166 str[3] = Tx \| (c & Maskx);
	167 return 4;
	168 }
	169
	170 int
	171 runelen(long c)
	172 {
	173 Rune rune;
	174 char str[10];
	175
	176 rune = c;
	177 return runetochar(str, &rune);
	178 }
	179
	180 int
	181 runenlen(Rune *r, int nrune)
	182 {
	183 int nb, c;
	184
	185 nb = 0;
	186 while(nrune--) {
	187 c = *r++;
	188 if(c <= Rune1)
	189 nb++;
	190 else
	191 if(c <= Rune2)
	192 nb += 2;
	193 else
	194 if(c <= Rune3 \|\| c > Runemax)
	195 nb += 3;
	196 else
	197 nb += 4;
	198 }
	199 return nb;
	200 }
	201
	202 int
	203 fullrune(char *str, int n)
	204 {
	205 int c;
	206
	207 if(n <= 0)
	208 return 0;
	209 c = (uchar)str;
	210 if(c < Tx)
	211 return 1;
	212 if(c < T3)
	213 return n >= 2;
	214 if(UTFmax == 3 \|\| c < T4)
	215 return n >= 3;
	216 return n >= 4;
	217 }