| /* Copyright (C) 2013-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library 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. |
| |
| The GNU C Library 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 the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <string.h> |
| #include <stdint.h> |
| #include "string-endian.h" |
| |
| /* Find the length of S, but scan at most MAXLEN characters. If no |
| '\0' terminator is found in that many characters, return MAXLEN. */ |
| size_t |
| __strnlen (const char *s, size_t maxlen) |
| { |
| /* When maxlen is 0, can't read any bytes or it might cause a page fault. */ |
| if (maxlen == 0) |
| return 0; |
| |
| /* Get an aligned pointer. */ |
| const uintptr_t s_int = (uintptr_t) s; |
| const uint64_t *p = (const uint64_t *) (s_int & -8); |
| size_t bytes_read = sizeof (*p) - (s_int & (sizeof (*p) - 1)); |
| |
| /* Read and MASK the first word. */ |
| uint64_t v = *p | MASK (s_int); |
| |
| uint64_t bits; |
| while ((bits = v1cmpeqi (v, 0)) == 0) |
| { |
| if (bytes_read >= maxlen) |
| { |
| /* Read maxlen bytes and didn't find the terminator. */ |
| return maxlen; |
| } |
| v = *++p; |
| bytes_read += sizeof (v); |
| } |
| |
| /* Found '\0', check it is not larger than maxlen */ |
| size_t len = ((const char *) p) + (CFZ (bits) >> 3) - s; |
| return (len < maxlen ? len : maxlen); |
| } |
| libc_hidden_def (__strnlen) |
| weak_alias (__strnlen, strnlen) |
| libc_hidden_def (strnlen) |
