sysdeps/generic/string-fzi.h

   1 /* Zero byte detection; indexes.  Generic C version.
   2    Copyright (C) 2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _STRING_FZI_H
  20 #define _STRING_FZI_H 1
  21
  22 #include <limits.h>
  23 #include <endian.h>
  24 #include <string-fza.h>
  25
  26 static __always_inline int
  27 clz (find_t c)
  28 {
  29   if (sizeof (find_t) == sizeof (unsigned long))
  30     return __builtin_clzl (c);
  31   else
  32     return __builtin_clzll (c);
  33 }
  34
  35 static __always_inline int
  36 ctz (find_t c)
  37 {
  38   if (sizeof (find_t) == sizeof (unsigned long))
  39     return __builtin_ctzl (c);
  40   else
  41     return __builtin_ctzll (c);
  42 }
  43
  44 /* A subroutine for the index_zero functions.  Given a test word C, return
  45    the (memory order) index of the first byte (in memory order) that is
  46    non-zero.  */
  47 static __always_inline unsigned int
  48 index_first (find_t c)
  49 {
  50   int r;
  51   if (__BYTE_ORDER == __LITTLE_ENDIAN)
  52     r = ctz (c);
  53   else
  54     r = clz (c);
  55   return r / CHAR_BIT;
  56 }
  57
  58 /* Similarly, but return the (memory order) index of the last byte that is
  59    non-zero.  */
  60 static __always_inline unsigned int
  61 index_last (find_t c)
  62 {
  63   int r;
  64   if (__BYTE_ORDER == __LITTLE_ENDIAN)
  65     r = clz (c);
  66   else
  67     r = ctz (c);
  68   return sizeof (find_t) - 1 - (r / CHAR_BIT);
  69 }
  70
  71 #endif /* STRING_FZI_H */