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-common.h" 14 15 /** 16 * mod_utf8_codepoint: 17 * @s: string encoded in modified UTF-8 18 * @n: maximum number of bytes to read from @s, if less than 6 19 * @end: set to end of sequence on return 20 * 21 * Convert the modified UTF-8 sequence at the start of @s. Modified 22 * UTF-8 is exactly like UTF-8, except U+0000 is encoded as 23 * "\xC0\x80". 24 * 25 * If @n is zero or @s points to a zero byte, the sequence is invalid, 26 * and @end is set to @s. 27 * 28 * If @s points to an impossible byte (0xFE or 0xFF) or a continuation 29 * byte, the sequence is invalid, and @end is set to @s + 1 30 * 31 * Else, the first byte determines how many continuation bytes are 32 * expected. If there are fewer, the sequence is invalid, and @end is 33 * set to @s + 1 + actual number of continuation bytes. Else, the 34 * sequence is well-formed, and @end is set to @s + 1 + expected 35 * number of continuation bytes. 36 * 37 * A well-formed sequence is valid unless it encodes a codepoint 38 * outside the Unicode range U+0000..U+10FFFF, one of Unicode's 66 39 * noncharacters, a surrogate codepoint, or is overlong. Except the 40 * overlong sequence "\xC0\x80" is valid. 41 * 42 * Conversion succeeds if and only if the sequence is valid. 43 * 44 * Returns: the Unicode codepoint on success, -1 on failure. 45 */ 46 int mod_utf8_codepoint(const char *s, size_t n, char **end) 47 { 48 static int min_cp[5] = { 0x80, 0x800, 0x10000, 0x200000, 0x4000000 }; 49 const unsigned char *p; 50 unsigned byte, mask, len, i; 51 int cp; 52 53 if (n == 0 || *s == 0) { 54 /* empty sequence */ 55 *end = (char *)s; 56 return -1; 57 } 58 59 p = (const unsigned char *)s; 60 byte = *p++; 61 if (byte < 0x80) { 62 cp = byte; /* one byte sequence */ 63 } else if (byte >= 0xFE) { 64 cp = -1; /* impossible bytes 0xFE, 0xFF */ 65 } else if ((byte & 0x40) == 0) { 66 cp = -1; /* unexpected continuation byte */ 67 } else { 68 /* multi-byte sequence */ 69 len = 0; 70 for (mask = 0x80; byte & mask; mask >>= 1) { 71 len++; 72 } 73 assert(len > 1 && len < 7); 74 cp = byte & (mask - 1); 75 for (i = 1; i < len; i++) { 76 byte = i < n ? *p : 0; 77 if ((byte & 0xC0) != 0x80) { 78 cp = -1; /* continuation byte missing */ 79 goto out; 80 } 81 p++; 82 cp <<= 6; 83 cp |= byte & 0x3F; 84 } 85 if (cp > 0x10FFFF) { 86 cp = -1; /* beyond Unicode range */ 87 } else if ((cp >= 0xFDD0 && cp <= 0xFDEF) 88 || (cp & 0xFFFE) == 0xFFFE) { 89 cp = -1; /* noncharacter */ 90 } else if (cp >= 0xD800 && cp <= 0xDFFF) { 91 cp = -1; /* surrogate code point */ 92 } else if (cp < min_cp[len - 2] && !(cp == 0 && len == 2)) { 93 cp = -1; /* overlong, not \xC0\x80 */ 94 } 95 } 96 97 out: 98 *end = (char *)p; 99 return cp; 100 } 101