1 /* Iterate over previous character in UTF-8 string.
2 Copyright (C) 2002, 2006-2007, 2009-2019 Free Software Foundation, Inc.
3 Written by Bruno Haible <bruno@clisp.org>, 2002.
5 This program is free software: you can redistribute it and/or modify it
6 under the terms of the GNU Lesser General Public License as published
7 by the Free Software Foundation; either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
24 u8_prev (ucs4_t
*puc
, const uint8_t *s
, const uint8_t *start
)
26 /* Keep in sync with unistr.h and u8-mbtouc-aux.c. */
36 if ((c_1
^ 0x80) < 0x40)
41 if (c_2
>= 0xc2 && c_2
< 0xe0)
43 *puc
= ((unsigned int) (c_2
& 0x1f) << 6)
44 | (unsigned int) (c_1
^ 0x80);
47 if ((c_2
^ 0x80) < 0x40)
52 if (c_3
>= 0xe0 && c_3
< 0xf0
53 && (c_3
>= 0xe1 || c_2
>= 0xa0)
54 && (c_3
!= 0xed || c_2
< 0xa0))
56 *puc
= ((unsigned int) (c_3
& 0x0f) << 12)
57 | ((unsigned int) (c_2
^ 0x80) << 6)
58 | (unsigned int) (c_1
^ 0x80);
61 if ((c_3
^ 0x80) < 0x40)
66 if (c_4
>= 0xf0 && c_4
< 0xf8
67 && (c_4
>= 0xf1 || c_3
>= 0x90)
68 && (c_4
< 0xf4 || (c_4
== 0xf4 && c_3
< 0x90)))
70 *puc
= ((unsigned int) (c_4
& 0x07) << 18)
71 | ((unsigned int) (c_3
^ 0x80) << 12)
72 | ((unsigned int) (c_2
^ 0x80) << 6)
73 | (unsigned int) (c_1
^ 0x80);