mirror of https://gitee.com/openkylin/qemu.git
101 lines
3.1 KiB
C
101 lines
3.1 KiB
C
/*
|
|
* 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;
|
|
}
|