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/* Zero byte detection; indexes. Generic C version.
Copyright (C) 2023-2026 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/>. */
#ifndef _STRING_FZI_H
#define _STRING_FZI_H 1
#include <limits.h>
#include <endian.h>
#include <string-fza.h>
#include <string-bitops.h>
#include <stdbit.h>
static __always_inline unsigned int
ctzb (find_t c)
{
#if HAVE_BITOPTS_WORKING
return stdc_trailing_zeros (c) / CHAR_BIT;
#else
if (sizeof (find_t) <= 4)
return (((c & -c) >> 7) * 0x00010203) >> 24;
else
return (((c & -c) >> 7) * 0x0001020304050607UL) >> 56;
#endif
}
static __always_inline unsigned int
clzb (find_t c)
{
#if HAVE_BITOPTS_WORKING
return stdc_leading_zeros (c) / CHAR_BIT;
#else
# if ULONG_MAX == 0xFFFFFFFFUL
c |= c >> 8;
c |= c >> 16;
return ((c >> 7) * 0x30f0f0f0) >> 28;
# else
c |= c >> 8;
c |= c >> 16;
c |= c >> 32;
return ((c >> 7) * 0x70f0f0f0f0f0f0f0UL) >> 60;
# endif
#endif
}
/* A subroutine for the index_zero functions. Given a test word C, return
the (memory order) index of the first byte (in memory order) that is
non-zero. */
static __always_inline unsigned int
index_first (find_t c)
{
unsigned int r;
if (__BYTE_ORDER == __LITTLE_ENDIAN)
r = ctzb (c);
else
r = clzb (c);
return r;
}
/* Similarly, but return the (memory order) index of the last byte that is
non-zero. */
static __always_inline unsigned int
index_last (find_t c)
{
unsigned int r;
if (__BYTE_ORDER == __LITTLE_ENDIAN)
r = clzb (c);
else
r = ctzb (c);
return sizeof (find_t) - 1 - r;
}
#endif /* STRING_FZI_H */
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