/* * 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" /** * 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 (cp > 0x10FFFF) { cp = -1; /* beyond Unicode range */ } else if ((cp >= 0xFDD0 && cp <= 0xFDEF) || (cp & 0xFFFE) == 0xFFFE) { cp = -1; /* noncharacter */ } else if (cp >= 0xD800 && cp <= 0xDFFF) { cp = -1; /* surrogate code point */ } else if (cp < min_cp[len - 2] && !(cp == 0 && len == 2)) { cp = -1; /* overlong, not \xC0\x80 */ } } out: *end = (char *)p; return cp; }