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/* Look at first character in UTF-8 string.
Copyright (C) 1999-2000, 2002, 2006-2007, 2009-2024 Free Software
Foundation, Inc.
Written by Bruno Haible <bruno@clisp.org>, 2002.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include "unistr.h"
int
u8_mblen (const uint8_t *s, size_t n)
{
if (n > 0)
{
/* Keep in sync with unistr.h and u8-mbtouc-aux.c. */
uint8_t c = *s;
if (c < 0x80)
return (c != 0 ? 1 : 0);
if (c >= 0xc2)
{
if (c < 0xe0)
{
if (n >= 2
&& (s[1] ^ 0x80) < 0x40)
return 2;
}
else if (c < 0xf0)
{
if (n >= 3
&& (s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
&& (c >= 0xe1 || s[1] >= 0xa0)
&& (c != 0xed || s[1] < 0xa0))
return 3;
}
else if (c <= 0xf4)
{
if (n >= 4
&& (s[1] ^ 0x80) < 0x40 && (s[2] ^ 0x80) < 0x40
&& (s[3] ^ 0x80) < 0x40
&& (c >= 0xf1 || s[1] >= 0x90)
&& (c < 0xf4 || (/* c == 0xf4 && */ s[1] < 0x90)))
return 4;
}
}
}
/* invalid or incomplete multibyte character */
return -1;
}
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