unistr/u{8,16,32}-uctomb: Avoid possible trouble with huge strings.
[gnulib.git] / lib / unistr / u8-uctomb-aux.c
blob4e66c95073da266b27438ff463ca2b88e3e305fb
1 /* Conversion UCS-4 to UTF-8.
2 Copyright (C) 2002, 2006-2007, 2009-2020 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/>. */
18 #include <config.h>
20 /* Specification. */
21 #include "unistr.h"
23 #include "attribute.h"
25 int
26 u8_uctomb_aux (uint8_t *s, ucs4_t uc, ptrdiff_t n)
28 int count;
30 if (uc < 0x80)
31 /* The case n >= 1 is already handled by the caller. */
32 return -2;
33 else if (uc < 0x800)
34 count = 2;
35 else if (uc < 0x10000)
37 if (uc < 0xd800 || uc >= 0xe000)
38 count = 3;
39 else
40 return -1;
42 else if (uc < 0x110000)
43 count = 4;
44 else
45 return -1;
47 if (n < count)
48 return -2;
50 switch (count) /* note: code falls through cases! */
52 case 4: s[3] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x10000;
53 FALLTHROUGH;
54 case 3: s[2] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0x800;
55 FALLTHROUGH;
56 case 2: s[1] = 0x80 | (uc & 0x3f); uc = uc >> 6; uc |= 0xc0;
57 /*case 1:*/ s[0] = uc;
59 return count;