sysdeps/generic/string-shift.h

   1 /* Shift unaligned word read  Generic C version.
   2    Copyright (C) 2023-2024 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_SHIFT_H
  20 #define _STRING_SHIFT_H 1
  21
  22 #include <endian.h>
  23 #include <limits.h>
  24 #include <stdint.h>
  25 #include <string-fza.h>
  26
  27 /* Return the mask WORD shifted based on S_INT address value, to ignore
  28    values not presented in the aligned word read.  */
  29 static __always_inline find_t
  30 shift_find (find_t word, uintptr_t s)
  31 {
  32   if (__BYTE_ORDER == __LITTLE_ENDIAN)
  33     return word >> (CHAR_BIT * (s % sizeof (op_t)));
  34   else
  35     return word << (CHAR_BIT * (s % sizeof (op_t)));
  36 }
  37
  38 /* Mask off the bits defined for the S alignment value, or return WORD if
  39    S is 0.  */
  40 static __always_inline find_t
  41 shift_find_last (find_t word, uintptr_t s)
  42 {
  43   s = s % sizeof (op_t);
  44   if (s == 0)
  45     return word;
  46   if (__BYTE_ORDER == __LITTLE_ENDIAN)
  47     return word & ~(((op_t)-1) << (s * CHAR_BIT));
  48   else
  49     return word & ~(((op_t)-1) >> (s * CHAR_BIT));
  50 }
  51
  52 #endif /* _STRING_SHIFT_H */