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