balloon: Don't balloon roms
[qemu.git] / util / unicode.c
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 /**
17 * mod_utf8_codepoint:
18 * @s: string encoded in modified UTF-8
19 * @n: maximum number of bytes to read from @s, if less than 6
20 * @end: set to end of sequence on return
21 *
22 * Convert the modified UTF-8 sequence at the start of @s. Modified
23 * UTF-8 is exactly like UTF-8, except U+0000 is encoded as
24 * "\xC0\x80".
25 *
26 * If @n is zero or @s points to a zero byte, the sequence is invalid,
27 * and @end is set to @s.
28 *
29 * If @s points to an impossible byte (0xFE or 0xFF) or a continuation
30 * byte, the sequence is invalid, and @end is set to @s + 1
31 *
32 * Else, the first byte determines how many continuation bytes are
33 * expected. If there are fewer, the sequence is invalid, and @end is
34 * set to @s + 1 + actual number of continuation bytes. Else, the
35 * sequence is well-formed, and @end is set to @s + 1 + expected
36 * number of continuation bytes.
37 *
38 * A well-formed sequence is valid unless it encodes a codepoint
39 * outside the Unicode range U+0000..U+10FFFF, one of Unicode's 66
40 * noncharacters, a surrogate codepoint, or is overlong. Except the
41 * overlong sequence "\xC0\x80" is valid.
42 *
43 * Conversion succeeds if and only if the sequence is valid.
44 *
45 * Returns: the Unicode codepoint on success, -1 on failure.
46 */
47 int mod_utf8_codepoint(const char *s, size_t n, char **end)
48 {
49 static int min_cp[5] = { 0x80, 0x800, 0x10000, 0x200000, 0x4000000 };
50 const unsigned char *p;
51 unsigned byte, mask, len, i;
52 int cp;
53
54 if (n == 0 || *s == 0) {
55 /* empty sequence */
56 *end = (char *)s;
57 return -1;
58 }
59
60 p = (const unsigned char *)s;
61 byte = *p++;
62 if (byte < 0x80) {
63 cp = byte; /* one byte sequence */
64 } else if (byte >= 0xFE) {
65 cp = -1; /* impossible bytes 0xFE, 0xFF */
66 } else if ((byte & 0x40) == 0) {
67 cp = -1; /* unexpected continuation byte */
68 } else {
69 /* multi-byte sequence */
70 len = 0;
71 for (mask = 0x80; byte & mask; mask >>= 1) {
72 len++;
73 }
74 assert(len > 1 && len < 7);
75 cp = byte & (mask - 1);
76 for (i = 1; i < len; i++) {
77 byte = i < n ? *p : 0;
78 if ((byte & 0xC0) != 0x80) {
79 cp = -1; /* continuation byte missing */
80 goto out;
81 }
82 p++;
83 cp <<= 6;
84 cp |= byte & 0x3F;
85 }
86 if (cp > 0x10FFFF) {
87 cp = -1; /* beyond Unicode range */
88 } else if ((cp >= 0xFDD0 && cp <= 0xFDEF)
89 || (cp & 0xFFFE) == 0xFFFE) {
90 cp = -1; /* noncharacter */
91 } else if (cp >= 0xD800 && cp <= 0xDFFF) {
92 cp = -1; /* surrogate code point */
93 } else if (cp < min_cp[len - 2] && !(cp == 0 && len == 2)) {
94 cp = -1; /* overlong, not \xC0\x80 */
95 }
96 }
97
98 out:
99 *end = (char *)p;
100 return cp;
101 }