1 : /* utf8_decode.c */
2 :
3 : /* 2005-12-25 */
4 :
5 : /*
6 : Copyright (c) 2005 JSON.org
7 :
8 : Permission is hereby granted, free of charge, to any person obtaining a copy
9 : of this software and associated documentation files (the "Software"), to deal
10 : in the Software without restriction, including without limitation the rights
11 : to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
12 : copies of the Software, and to permit persons to whom the Software is
13 : furnished to do so, subject to the following conditions:
14 :
15 : The above copyright notice and this permission notice shall be included in all
16 : copies or substantial portions of the Software.
17 :
18 : The Software shall be used for Good, not Evil.
19 :
20 : THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21 : IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22 : FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
23 : AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
24 : LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
25 : OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
26 : SOFTWARE.
27 : */
28 :
29 : #include "utf8_decode.h"
30 :
31 : /*
32 : Very Strict UTF-8 Decoder
33 :
34 : UTF-8 is a multibyte character encoding of Unicode. A character can be
35 : represented by 1-4 bytes. The bit pattern of the first byte indicates the
36 : number of continuation bytes.
37 :
38 : Most UTF-8 decoders tend to be lenient, attempting to recover as much
39 : information as possible, even from badly encoded input. This UTF-8
40 : decoder is not lenient. It will reject input which does not include
41 : proper continuation bytes. It will reject aliases (or suboptimal
42 : codings). It will reject surrogates. (Surrogate encoding should only be
43 : used with UTF-16.)
44 :
45 : Code Contination Minimum Maximum
46 : 0xxxxxxx 0 0 127
47 : 10xxxxxx error
48 : 110xxxxx 1 128 2047
49 : 1110xxxx 2 2048 65535 excluding 55296 - 57343
50 : 11110xxx 3 65536 1114111
51 : 11111xxx error
52 : */
53 :
54 :
55 : /*
56 : Get the next byte. It returns UTF8_END if there are no more bytes.
57 : */
58 : static int
59 : get(json_utf8_decode *utf8)
60 18585 : {
61 : int c;
62 18585 : if (utf8->the_index >= utf8->the_length) {
63 6 : return UTF8_END;
64 : }
65 18579 : c = utf8->the_input[utf8->the_index] & 0xFF;
66 18579 : utf8->the_index += 1;
67 18579 : return c;
68 : }
69 :
70 :
71 : /*
72 : Get the 6-bit payload of the next continuation byte.
73 : Return UTF8_ERROR if it is not a contination byte.
74 : */
75 : static int
76 : cont(json_utf8_decode *utf8)
77 315 : {
78 315 : int c = get(utf8);
79 315 : return ((c & 0xC0) == 0x80) ? (c & 0x3F) : UTF8_ERROR;
80 : }
81 :
82 :
83 : /*
84 : Initialize the UTF-8 decoder. The decoder is not reentrant,
85 : */
86 : void
87 : utf8_decode_init(json_utf8_decode *utf8, char p[], int length)
88 464 : {
89 464 : utf8->the_index = 0;
90 464 : utf8->the_input = p;
91 464 : utf8->the_length = length;
92 464 : utf8->the_char = 0;
93 464 : utf8->the_byte = 0;
94 464 : }
95 :
96 :
97 : /*
98 : Get the current byte offset. This is generally used in error reporting.
99 : */
100 : int
101 : utf8_decode_at_byte(json_utf8_decode *utf8)
102 0 : {
103 0 : return utf8->the_byte;
104 : }
105 :
106 :
107 : /*
108 : Get the current character offset. This is generally used in error reporting.
109 : The character offset matches the byte offset if the text is strictly ASCII.
110 : */
111 : int
112 : utf8_decode_at_character(json_utf8_decode *utf8)
113 0 : {
114 0 : return utf8->the_char > 0 ? utf8->the_char - 1 : 0;
115 : }
116 :
117 :
118 : /*
119 : Extract the next character.
120 : Returns: the character (between 0 and 1114111)
121 : or UTF8_END (the end)
122 : or UTF8_ERROR (error)
123 : */
124 : int
125 : utf8_decode_next(json_utf8_decode *utf8)
126 18730 : {
127 : int c; /* the first byte of the character */
128 : int r; /* the result */
129 :
130 18730 : if (utf8->the_index >= utf8->the_length) {
131 460 : return utf8->the_index == utf8->the_length ? UTF8_END : UTF8_ERROR;
132 : }
133 18270 : utf8->the_byte = utf8->the_index;
134 18270 : utf8->the_char += 1;
135 18270 : c = get(utf8);
136 : /*
137 : Zero continuation (0 to 127)
138 : */
139 18270 : if ((c & 0x80) == 0) {
140 18113 : return c;
141 : }
142 : /*
143 : One contination (128 to 2047)
144 : */
145 157 : if ((c & 0xE0) == 0xC0) {
146 16 : int c1 = cont(utf8);
147 16 : if (c1 < 0) {
148 0 : return UTF8_ERROR;
149 : }
150 16 : r = ((c & 0x1F) << 6) | c1;
151 16 : return r >= 128 ? r : UTF8_ERROR;
152 : }
153 : /*
154 : Two continuation (2048 to 55295 and 57344 to 65535)
155 : */
156 141 : if ((c & 0xF0) == 0xE0) {
157 124 : int c1 = cont(utf8);
158 124 : int c2 = cont(utf8);
159 124 : if (c1 < 0 || c2 < 0) {
160 4 : return UTF8_ERROR;
161 : }
162 120 : r = ((c & 0x0F) << 12) | (c1 << 6) | c2;
163 120 : return r >= 2048 && (r < 55296 || r > 57343) ? r : UTF8_ERROR;
164 : }
165 : /*
166 : Three continuation (65536 to 1114111)
167 : */
168 17 : if ((c & 0xF8) == 0xF0) {
169 17 : int c1 = cont(utf8);
170 17 : int c2 = cont(utf8);
171 17 : int c3 = cont(utf8);
172 17 : if (c1 < 0 || c2 < 0 || c3 < 0) {
173 0 : return UTF8_ERROR;
174 : }
175 17 : r = ((c & 0x0F) << 18) | (c1 << 12) | (c2 << 6) | c3;
176 17 : return r >= 65536 && r <= 1114111 ? r : UTF8_ERROR;
177 : }
178 0 : return UTF8_ERROR;
179 : }
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