sysdeps/generic/string-misc.h

   1 /* Miscellaneous functions used in string implementations.  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_MISC_H
  20 #define _STRING_MISC_H 1
  21
  22 #include <limits.h>
  23 #include <endian.h>
  24 #include <string-optype.h>
  25
  26 /* Extract the byte at index IDX from word X, with index 0 being the
  27    least significant byte.  */
  28 static __always_inline unsigned char
  29 extractbyte (op_t x, unsigned int idx)
  30 {
  31   if (__BYTE_ORDER == __LITTLE_ENDIAN)
  32     return x >> (idx * CHAR_BIT);
  33   else
  34     return x >> (sizeof (x) - 1 - idx) * CHAR_BIT;
  35 }
  36
  37 /* Setup an word with each byte being c_in.  For instance, on a 64 bits
  38    machine with input as 0xce the functions returns 0xcececececececece.  */
  39 static __always_inline op_t
  40 repeat_bytes (unsigned char c_in)
  41 {
  42   return ((op_t)-1 / 0xff) * c_in;
  43 }
  44
  45 #endif /* _STRING_MISC_H */