/*
* 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-common.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;
}
