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 } 102