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view prototype/drawtext/utf8.c @ 30:938a6a155c94

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author John Tsiombikas <nuclear@member.fsf.org>
date Mon, 27 Aug 2012 04:03:22 +0300
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1 /*
2 libdrawtext - a simple library for fast text rendering in OpenGL
3 Copyright (C) 2011 John Tsiombikas <nuclear@member.fsf.org>
4
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
17 */
18 #include "drawtext.h"
19
20 #define U8_IS_FIRST(x) (((((x) >> 7) & 1) == 0) || ((((x) >> 6) & 3) == 3))
21
22 static const char first_mask[] = {
23 0,
24 0x7f, /* single byte, 7 bits valid */
25 0x1f, /* two-bytes, 5 bits valid */
26 0xf, /* three-bytes, 4 bits valid */
27 0x7 /* four-bytes, 3 bits valid */
28 };
29 static const char first_shift[] = { 0, 7, 5, 4, 3 }; /* see above */
30
31 #define CONT_PREFIX 0x80
32 #define CONT_MASK 0x3f
33 #define CONT_SHIFT 6
34
35 /* last charcodes for 1, 2, 3 or 4-byte utf8 chars */
36 static const int utf8_lastcode[] = { 0x7f, 0x7ff, 0xfff, 0x1fffff };
37
38 #define prefix_mask(x) (~first_mask[x])
39 #define prefix(x) ((prefix_mask(x) << 1) & 0xff)
40
41
42 char *dtx_utf8_next_char(char *str)
43 {
44 return str + dtx_utf8_nbytes(str);
45 }
46
47 int dtx_utf8_char_code(const char *str)
48 {
49 int i, nbytes, shift, code = 0;
50 int mask;
51
52 if(!U8_IS_FIRST(*str)) {
53 return -1;
54 }
55
56 nbytes = dtx_utf8_nbytes(str);
57 mask = first_mask[nbytes];
58 shift = 0;
59
60 for(i=0; i<nbytes; i++) {
61 if(!*str) {
62 break;
63 }
64
65 code = (code << shift) | (*str++ & mask);
66 mask = 0x3f;
67 shift = 6;
68 }
69 return code;
70 }
71
72 int dtx_utf8_nbytes(const char *str)
73 {
74 int i, numset = 0;
75 int c = *str;
76
77 if(!U8_IS_FIRST(c)) {
78 for(i=0; !U8_IS_FIRST(str[i]); i++);
79 return i;
80 }
81
82 /* count the leading 1s */
83 for(i=0; i<4; i++) {
84 if(((c >> (7 - i)) & 1) == 0) {
85 break;
86 }
87 numset++;
88 }
89
90 if(!numset) {
91 return 1;
92 }
93 return numset;
94 }
95
96 int dtx_utf8_char_count(const char *str)
97 {
98 int n = 0;
99
100 while(*str) {
101 n++;
102 str = dtx_utf8_next_char((char*)str);
103 }
104 return n;
105 }
106
107 size_t dtx_utf8_from_char_code(int code, char *buf)
108 {
109 size_t nbytes = 0;
110 int i;
111
112 for(i=0; i<4; i++) {
113 if(code <= utf8_lastcode[i]) {
114 nbytes = i + 1;
115 break;
116 }
117 }
118
119 if(!nbytes && buf) {
120 for(i=0; i<nbytes; i++) {
121 int idx = nbytes - i - 1;
122 int mask, shift, prefix;
123
124 if(idx > 0) {
125 mask = CONT_MASK;
126 shift = CONT_SHIFT;
127 prefix = CONT_PREFIX;
128 } else {
129 mask = first_mask[nbytes];
130 shift = first_shift[nbytes];
131 prefix = prefix(nbytes);
132 }
133
134 buf[idx] = (code & mask) | (prefix & ~mask);
135 code >>= shift;
136 }
137 }
138 return nbytes;
139 }
140
141 size_t dtx_utf8_from_string(const wchar_t *str, char *buf)
142 {
143 size_t nbytes = 0;
144 char *ptr = buf;
145
146 while(*str) {
147 int cbytes = dtx_utf8_from_char_code(*str++, ptr);
148 if(ptr) {
149 ptr += cbytes;
150 }
151 nbytes += cbytes;
152 }
153 return nbytes;
154 }