forked from vstinner/unicode_book
-
Notifications
You must be signed in to change notification settings - Fork 0
/
guess_encoding.c
180 lines (158 loc) · 5.14 KB
/
guess_encoding.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
#include <stdio.h> /* printf() */
#include <stdint.h> /* uint32_t */
#include <string.h> /* memcmp() */
static void
dump_byte_string(FILE *f,
const char *prefix,
const char *string,
size_t len,
const char *suffix)
{
const char *end;
unsigned c;
fputs(prefix, f);
end = string + len;
for (; string != end; string++) {
c = (unsigned char)*string;
if (32 <= c && c <= 127)
fputc((char)c, f);
else
fprintf(f, "\\x%02X", c);
}
fputs(suffix, f);
fflush(f);
}
int
isASCII(const char *data, size_t size)
{
const unsigned char *str = (unsigned char*)data;
const unsigned char *end = str + size;
for (; str != end; str++) {
if (*str & 0x80)
return 0;
}
return 1;
}
int
isUTF8(const char *data, size_t size)
{
const unsigned char *str = (unsigned char*)data;
unsigned int code_length, i;
uint32_t ch;
const unsigned char *end = str + size;
while (str != end) {
if (*str <= 0x7F) {
/* 1 byte character (ASCII): U+0000..U+007F */
str += 1;
continue;
}
if (0xC2 <= *str && *str <= 0xDF)
code_length = 2;
else if (0xE0 <= *str && *str <= 0xEF)
code_length = 3;
else if (0xF0 <= *str && *str <= 0xF4)
code_length = 4;
else {
/* invalid first byte of a multibyte character */
return 0;
}
if (str + (code_length -1) >= end) {
/* truncated string or invalid byte sequence */
return 0;
}
/* Check continuation bytes: bit 7 should be set, bit 6 should unset */
for (i=1; i < code_length; i++) {
if ((str[i] & 0xc0) != 0x80)
return 0;
}
if (code_length == 2) {
ch = ((str[0] & 0x1f) << 6) + (str[1] & 0x3f);
/* 2 bytes sequence: U+0080..U+07FF */
if ((ch < 0x0080) || (0x07FF < ch))
return 0;
} else if (code_length == 3) {
ch = ((str[0] & 0x0f) << 12) + ((str[1] & 0x3f) << 6) +
(str[2] & 0x3f);
/* 3 bytes sequence: U+0800..U+FFFF */
if ((ch < 0x0800) || (0xFFFF < ch))
return 0;
/* 3 bytes sequence: U+0800..U+FFFF... excluding U+D800..U+DFFF:
* surrogates are invalid in UTF-8 */
if ((0xD800 <= ch) && (ch <= 0xDFFF))
return 0;
} else if (code_length == 4) {
ch = ((str[0] & 0x7) << 18) + ((str[1] & 0x3f) << 12) +
((str[2] & 0x3f) << 6) + (str[3] & 0x3f);
/* 4 bytes sequence: U+10000..U+10FFFF */
if ((ch < 0x10000) || (0x10FFFF < ch))
return 0;
}
str += code_length;
}
return 1;
}
const char UTF_8_BOM[] = "\xEF\xBB\xBF"; /* 3 bytes */
const char UTF_16_BE_BOM[] = "\xFE\xFF"; /* 2 bytes */
const char UTF_16_LE_BOM[] = "\xFF\xFE"; /* 2 bytes */
const char UTF_32_BE_BOM[] = "\x00\x00\xFE\xFF"; /* 4 bytes */
const char UTF_32_LE_BOM[] = "\xFF\xFE\x00\x00"; /* 4 bytes */
void guess_encoding(const char *data, size_t size)
{
#define FOUND(name) \
do { \
if (found) fputs(", ", stdout); \
fputs(name, stdout); \
found = 1; \
} while (0)
int found = 0;
dump_byte_string(stdout, "guess_encoding(\"", data, size, "\"): ");
if (size >= 3) {
if (memcmp(data, UTF_8_BOM, 3) == 0)
FOUND("UTF-8 (BOM)");
}
if (size >= 4) {
if (memcmp(data, UTF_32_LE_BOM, 4) == 0)
FOUND("UTF-32-LE (BOM)");
if (memcmp(data, UTF_32_BE_BOM, 4) == 0)
FOUND("UTF-32-BE (BOM)");
}
if (size >= 2) {
if (memcmp(data, UTF_16_LE_BOM, 2) == 0)
FOUND("UTF-16-LE (BOM)");
if (memcmp(data, UTF_16_BE_BOM, 2) == 0)
FOUND("UTF-16-BE (BOM)");
}
if (isASCII(data, size)) { FOUND("ASCII"); }
if (isUTF8(data, size)) { FOUND("UTF-8"); }
if (!found)
printf("<unknown>");
fputs("\n", stdout);
}
#define GUESS_ENCODING(data) guess_encoding(data, sizeof(data) - 1)
int main()
{
char ascii[] = "ascii";
char utf8_ecute[] = "\xC3\xA9"; /* U+00E9 */
char utf8_euro[] = "\xE2\x82\xAC"; /* U+20AC */
char utf8_10ffff[] = "\xF4\x8F\xBF\xBF"; /* U+10FFFF */
char invalid_utf8[] = "\xC0\x80";
char utf8_surrogate[] = "\xED\xB2\x80";
/* U+00E9, U+20AC */
char utf8_bom[] = "\xEF\xBB\xBF\xC3\xA9\xE2\x82\xAC";
char utf16le_bom[] = "\xFF\xFE\xE9\x00\xAC\x20";
char utf16be_bom[] = "\xFE\xFF\x00\xE9\x20\xAC";
char utf32le_bom[] = "\xFF\xFE\x00\x00\xE9\x00\x00\x00\xAC\x20\x00\x00";
char utf32be_bom[] = "\x00\x00\xFE\xFF\x00\x00\x00\xE9\x00\x00\x20\xAC";
GUESS_ENCODING(ascii);
GUESS_ENCODING(utf8_ecute);
GUESS_ENCODING(utf8_euro);
GUESS_ENCODING(utf8_10ffff);
GUESS_ENCODING(invalid_utf8);
GUESS_ENCODING(utf8_surrogate);
GUESS_ENCODING(utf8_bom);
GUESS_ENCODING(utf16le_bom);
GUESS_ENCODING(utf16be_bom);
GUESS_ENCODING(utf32le_bom);
GUESS_ENCODING(utf32be_bom);
return 0;
}