vis

a vi-like editor based on Plan 9's structural regular expressions
libutf.c

(1251B)
      1 /* libutf8 © 2012-2015 Connor Lane Smith <cls@lubutu.com> */
      2 #include "libutf.h"
      3 #include "util.h"
      4 
      5 int
      6 runelen(Rune r)
      7 {
      8 	if(r <= 0x7F)
      9 		return 1;
     10 	else if(r <= 0x07FF)
     11 		return 2;
     12 	else if(r <= 0xD7FF)
     13 		return 3;
     14 	else if(r <= 0xDFFF)
     15 		return 0; /* surrogate character */
     16 	else if(r <= 0xFFFD)
     17 		return 3;
     18 	else if(r <= 0xFFFF)
     19 		return 0; /* illegal character */
     20 	else if(r <= Runemax)
     21 		return 4;
     22 	else
     23 		return 0; /* rune too large */
     24 }
     25 
     26 int
     27 runetochar(char *s, const Rune *p)
     28 {
     29 	Rune r = *p;
     30 
     31 	switch(runelen(r)) {
     32 	case 1: /* 0aaaaaaa */
     33 		s[0] = r;
     34 		return 1;
     35 	case 2: /* 00000aaa aabbbbbb */
     36 		s[0] = 0xC0 | ((r & 0x0007C0) >>  6); /* 110aaaaa */
     37 		s[1] = 0x80 |  (r & 0x00003F);        /* 10bbbbbb */
     38 		return 2;
     39 	case 3: /* aaaabbbb bbcccccc */
     40 		s[0] = 0xE0 | ((r & 0x00F000) >> 12); /* 1110aaaa */
     41 		s[1] = 0x80 | ((r & 0x000FC0) >>  6); /* 10bbbbbb */
     42 		s[2] = 0x80 |  (r & 0x00003F);        /* 10cccccc */
     43 		return 3;
     44 	case 4: /* 000aaabb bbbbcccc ccdddddd */
     45 		s[0] = 0xF0 | ((r & 0x1C0000) >> 18); /* 11110aaa */
     46 		s[1] = 0x80 | ((r & 0x03F000) >> 12); /* 10bbbbbb */
     47 		s[2] = 0x80 | ((r & 0x000FC0) >>  6); /* 10cccccc */
     48 		s[3] = 0x80 |  (r & 0x00003F);        /* 10dddddd */
     49 		return 4;
     50 	default:
     51 		return 0; /* error */
     52 	}
     53 }