1 | /* |
2 | * Dealing with Unicode |
3 | * |
4 | * Copyright (C) 2013 Red Hat, Inc. |
5 | * |
6 | * Authors: |
7 | * Markus Armbruster <armbru@redhat.com> |
8 | * |
9 | * This work is licensed under the terms of the GNU GPL, version 2 or |
10 | * later. See the COPYING file in the top-level directory. |
11 | */ |
12 | |
13 | #include "qemu/osdep.h" |
14 | #include "qemu/unicode.h" |
15 | |
16 | static bool is_valid_codepoint(int codepoint) |
17 | { |
18 | if (codepoint > 0x10FFFFu) { |
19 | return false; /* beyond Unicode range */ |
20 | } |
21 | if ((codepoint >= 0xFDD0 && codepoint <= 0xFDEF) |
22 | || (codepoint & 0xFFFE) == 0xFFFE) { |
23 | return false; /* noncharacter */ |
24 | } |
25 | if (codepoint >= 0xD800 && codepoint <= 0xDFFF) { |
26 | return false; /* surrogate code point */ |
27 | } |
28 | return true; |
29 | } |
30 | |
31 | /** |
32 | * mod_utf8_codepoint: |
33 | * @s: string encoded in modified UTF-8 |
34 | * @n: maximum number of bytes to read from @s, if less than 6 |
35 | * @end: set to end of sequence on return |
36 | * |
37 | * Convert the modified UTF-8 sequence at the start of @s. Modified |
38 | * UTF-8 is exactly like UTF-8, except U+0000 is encoded as |
39 | * "\xC0\x80". |
40 | * |
41 | * If @n is zero or @s points to a zero byte, the sequence is invalid, |
42 | * and @end is set to @s. |
43 | * |
44 | * If @s points to an impossible byte (0xFE or 0xFF) or a continuation |
45 | * byte, the sequence is invalid, and @end is set to @s + 1 |
46 | * |
47 | * Else, the first byte determines how many continuation bytes are |
48 | * expected. If there are fewer, the sequence is invalid, and @end is |
49 | * set to @s + 1 + actual number of continuation bytes. Else, the |
50 | * sequence is well-formed, and @end is set to @s + 1 + expected |
51 | * number of continuation bytes. |
52 | * |
53 | * A well-formed sequence is valid unless it encodes a codepoint |
54 | * outside the Unicode range U+0000..U+10FFFF, one of Unicode's 66 |
55 | * noncharacters, a surrogate codepoint, or is overlong. Except the |
56 | * overlong sequence "\xC0\x80" is valid. |
57 | * |
58 | * Conversion succeeds if and only if the sequence is valid. |
59 | * |
60 | * Returns: the Unicode codepoint on success, -1 on failure. |
61 | */ |
62 | int mod_utf8_codepoint(const char *s, size_t n, char **end) |
63 | { |
64 | static int min_cp[5] = { 0x80, 0x800, 0x10000, 0x200000, 0x4000000 }; |
65 | const unsigned char *p; |
66 | unsigned byte, mask, len, i; |
67 | int cp; |
68 | |
69 | if (n == 0 || *s == 0) { |
70 | /* empty sequence */ |
71 | *end = (char *)s; |
72 | return -1; |
73 | } |
74 | |
75 | p = (const unsigned char *)s; |
76 | byte = *p++; |
77 | if (byte < 0x80) { |
78 | cp = byte; /* one byte sequence */ |
79 | } else if (byte >= 0xFE) { |
80 | cp = -1; /* impossible bytes 0xFE, 0xFF */ |
81 | } else if ((byte & 0x40) == 0) { |
82 | cp = -1; /* unexpected continuation byte */ |
83 | } else { |
84 | /* multi-byte sequence */ |
85 | len = 0; |
86 | for (mask = 0x80; byte & mask; mask >>= 1) { |
87 | len++; |
88 | } |
89 | assert(len > 1 && len < 7); |
90 | cp = byte & (mask - 1); |
91 | for (i = 1; i < len; i++) { |
92 | byte = i < n ? *p : 0; |
93 | if ((byte & 0xC0) != 0x80) { |
94 | cp = -1; /* continuation byte missing */ |
95 | goto out; |
96 | } |
97 | p++; |
98 | cp <<= 6; |
99 | cp |= byte & 0x3F; |
100 | } |
101 | if (!is_valid_codepoint(cp)) { |
102 | cp = -1; |
103 | } else if (cp < min_cp[len - 2] && !(cp == 0 && len == 2)) { |
104 | cp = -1; /* overlong, not \xC0\x80 */ |
105 | } |
106 | } |
107 | |
108 | out: |
109 | *end = (char *)p; |
110 | return cp; |
111 | } |
112 | |
113 | /** |
114 | * mod_utf8_encode: |
115 | * @buf: Destination buffer |
116 | * @bufsz: size of @buf, at least 5. |
117 | * @codepoint: Unicode codepoint to encode |
118 | * |
119 | * Convert Unicode codepoint @codepoint to modified UTF-8. |
120 | * |
121 | * Returns: the length of the UTF-8 sequence on success, -1 when |
122 | * @codepoint is invalid. |
123 | */ |
124 | ssize_t mod_utf8_encode(char buf[], size_t bufsz, int codepoint) |
125 | { |
126 | assert(bufsz >= 5); |
127 | |
128 | if (!is_valid_codepoint(codepoint)) { |
129 | return -1; |
130 | } |
131 | |
132 | if (codepoint > 0 && codepoint <= 0x7F) { |
133 | buf[0] = codepoint & 0x7F; |
134 | buf[1] = 0; |
135 | return 1; |
136 | } |
137 | if (codepoint <= 0x7FF) { |
138 | buf[0] = 0xC0 | ((codepoint >> 6) & 0x1F); |
139 | buf[1] = 0x80 | (codepoint & 0x3F); |
140 | buf[2] = 0; |
141 | return 2; |
142 | } |
143 | if (codepoint <= 0xFFFF) { |
144 | buf[0] = 0xE0 | ((codepoint >> 12) & 0x0F); |
145 | buf[1] = 0x80 | ((codepoint >> 6) & 0x3F); |
146 | buf[2] = 0x80 | (codepoint & 0x3F); |
147 | buf[3] = 0; |
148 | return 3; |
149 | } |
150 | buf[0] = 0xF0 | ((codepoint >> 18) & 0x07); |
151 | buf[1] = 0x80 | ((codepoint >> 12) & 0x3F); |
152 | buf[2] = 0x80 | ((codepoint >> 6) & 0x3F); |
153 | buf[3] = 0x80 | (codepoint & 0x3F); |
154 | buf[4] = 0; |
155 | return 4; |
156 | } |
157 | |