summaryrefslogtreecommitdiff
path: root/util/unicode.c
blob: 8580bc598b3391f80854b0b0971470d62638b26e (plain)
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
/*
 * Dealing with Unicode
 *
 * Copyright (C) 2013 Red Hat, Inc.
 *
 * Authors:
 *  Markus Armbruster <armbru@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or
 * later.  See the COPYING file in the top-level directory.
 */

#include "qemu/osdep.h"
#include "qemu/unicode.h"

static bool is_valid_codepoint(int codepoint)
{
    if (codepoint > 0x10FFFFu) {
        return false;            /* beyond Unicode range */
    }
    if ((codepoint >= 0xFDD0 && codepoint <= 0xFDEF)
        || (codepoint & 0xFFFE) == 0xFFFE) {
        return false;            /* noncharacter */
    }
    if (codepoint >= 0xD800 && codepoint <= 0xDFFF) {
        return false;            /* surrogate code point */
    }
    return true;
}

/**
 * mod_utf8_codepoint:
 * @s: string encoded in modified UTF-8
 * @n: maximum number of bytes to read from @s, if less than 6
 * @end: set to end of sequence on return
 *
 * Convert the modified UTF-8 sequence at the start of @s.  Modified
 * UTF-8 is exactly like UTF-8, except U+0000 is encoded as
 * "\xC0\x80".
 *
 * If @n is zero or @s points to a zero byte, the sequence is invalid,
 * and @end is set to @s.
 *
 * If @s points to an impossible byte (0xFE or 0xFF) or a continuation
 * byte, the sequence is invalid, and @end is set to @s + 1
 *
 * Else, the first byte determines how many continuation bytes are
 * expected.  If there are fewer, the sequence is invalid, and @end is
 * set to @s + 1 + actual number of continuation bytes.  Else, the
 * sequence is well-formed, and @end is set to @s + 1 + expected
 * number of continuation bytes.
 *
 * A well-formed sequence is valid unless it encodes a codepoint
 * outside the Unicode range U+0000..U+10FFFF, one of Unicode's 66
 * noncharacters, a surrogate codepoint, or is overlong.  Except the
 * overlong sequence "\xC0\x80" is valid.
 *
 * Conversion succeeds if and only if the sequence is valid.
 *
 * Returns: the Unicode codepoint on success, -1 on failure.
 */
int mod_utf8_codepoint(const char *s, size_t n, char **end)
{
    static int min_cp[5] = { 0x80, 0x800, 0x10000, 0x200000, 0x4000000 };
    const unsigned char *p;
    unsigned byte, mask, len, i;
    int cp;

    if (n == 0 || *s == 0) {
        /* empty sequence */
        *end = (char *)s;
        return -1;
    }

    p = (const unsigned char *)s;
    byte = *p++;
    if (byte < 0x80) {
        cp = byte;              /* one byte sequence */
    } else if (byte >= 0xFE) {
        cp = -1;                /* impossible bytes 0xFE, 0xFF */
    } else if ((byte & 0x40) == 0) {
        cp = -1;                /* unexpected continuation byte */
    } else {
        /* multi-byte sequence */
        len = 0;
        for (mask = 0x80; byte & mask; mask >>= 1) {
            len++;
        }
        assert(len > 1 && len < 7);
        cp = byte & (mask - 1);
        for (i = 1; i < len; i++) {
            byte = i < n ? *p : 0;
            if ((byte & 0xC0) != 0x80) {
                cp = -1;        /* continuation byte missing */
                goto out;
            }
            p++;
            cp <<= 6;
            cp |= byte & 0x3F;
        }
        if (!is_valid_codepoint(cp)) {
            cp = -1;
        } else if (cp < min_cp[len - 2] && !(cp == 0 && len == 2)) {
            cp = -1;            /* overlong, not \xC0\x80 */
        }
    }

out:
    *end = (char *)p;
    return cp;
}

/**
 * mod_utf8_encode:
 * @buf: Destination buffer
 * @bufsz: size of @buf, at least 5.
 * @codepoint: Unicode codepoint to encode
 *
 * Convert Unicode codepoint @codepoint to modified UTF-8.
 *
 * Returns: the length of the UTF-8 sequence on success, -1 when
 * @codepoint is invalid.
 */
ssize_t mod_utf8_encode(char buf[], size_t bufsz, int codepoint)
{
    assert(bufsz >= 5);

    if (!is_valid_codepoint(codepoint)) {
        return -1;
    }

    if (codepoint > 0 && codepoint <= 0x7F) {
        buf[0] = codepoint & 0x7F;
        buf[1] = 0;
        return 1;
    }
    if (codepoint <= 0x7FF) {
        buf[0] = 0xC0 | ((codepoint >> 6) & 0x1F);
        buf[1] = 0x80 | (codepoint & 0x3F);
        buf[2] = 0;
        return 2;
    }
    if (codepoint <= 0xFFFF) {
        buf[0] = 0xE0 | ((codepoint >> 12) & 0x0F);
        buf[1] = 0x80 | ((codepoint >> 6) & 0x3F);
        buf[2] = 0x80 | (codepoint & 0x3F);
        buf[3] = 0;
        return 3;
    }
    buf[0] = 0xF0 | ((codepoint >> 18) & 0x07);
    buf[1] = 0x80 | ((codepoint >> 12) & 0x3F);
    buf[2] = 0x80 | ((codepoint >> 6) & 0x3F);
    buf[3] = 0x80 | (codepoint & 0x3F);
    buf[4] = 0;
    return 4;
}