sysdeps/generic/memswap.h

   1 /* Swap the content of two memory blocks, overlap is NOT handled.
   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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <string.h>
  20
  21 static inline void
  22 __memswap (void *__restrict p1, void *__restrict p2, size_t n)
  23 {
  24   /* Use multiple small memcpys with constant size to enable inlining on most
  25      targets.  */
  26   enum { SWAP_GENERIC_SIZE = 32 };
  27   unsigned char tmp[SWAP_GENERIC_SIZE];
  28   while (n > SWAP_GENERIC_SIZE)
  29     {
  30       memcpy (tmp, p1, SWAP_GENERIC_SIZE);
  31       p1 = __mempcpy (p1, p2, SWAP_GENERIC_SIZE);
  32       p2 = __mempcpy (p2, tmp, SWAP_GENERIC_SIZE);
  33       n -= SWAP_GENERIC_SIZE;
  34     }
  35   while (n > 0)
  36     {
  37       unsigned char t = ((unsigned char *)p1)[--n];
  38       ((unsigned char *)p1)[n] = ((unsigned char *)p2)[n];
  39       ((unsigned char *)p2)[n] = t;
  40     }
  41 }