1  /* Copy memory to memory until the specified number of bytes
       2     has been copied.  Overlap is handled correctly.
       3     Copyright (C) 1991-2023 Free Software Foundation, Inc.
       4     This file is part of the GNU C Library.
       5  
       6     The GNU C Library is free software; you can redistribute it and/or
       7     modify it under the terms of the GNU Lesser General Public
       8     License as published by the Free Software Foundation; either
       9     version 2.1 of the License, or (at your option) any later version.
      10  
      11     The GNU C Library is distributed in the hope that it will be useful,
      12     but WITHOUT ANY WARRANTY; without even the implied warranty of
      13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      14     Lesser General Public License for more details.
      15  
      16     You should have received a copy of the GNU Lesser General Public
      17     License along with the GNU C Library; if not, see
      18     <https://www.gnu.org/licenses/>.  */
      19  
      20  #include <string.h>
      21  #include <memcopy.h>
      22  
      23  /* All this is so that bcopy.c can #include
      24     this file after defining some things.  */
      25  #ifndef	a1
      26  #define	a1	dest	/* First arg is DEST.  */
      27  #define	a1const
      28  #define	a2	src	/* Second arg is SRC.  */
      29  #define	a2const	const
      30  #undef memmove
      31  #endif
      32  #if	!defined(RETURN) || !defined(rettype)
      33  #define	RETURN(s)	return (s)	/* Return DEST.  */
      34  #define	rettype		void *
      35  #endif
      36  
      37  #ifndef MEMMOVE
      38  #define MEMMOVE memmove
      39  #endif
      40  
      41  rettype
      42  inhibit_loop_to_libcall
      43  MEMMOVE (a1const void *a1, a2const void *a2, size_t len)
      44  {
      45    unsigned long int dstp = (long int) dest;
      46    unsigned long int srcp = (long int) src;
      47  
      48    /* This test makes the forward copying code be used whenever possible.
      49       Reduces the working set.  */
      50    if (dstp - srcp >= len)	/* *Unsigned* compare!  */
      51      {
      52        /* Copy from the beginning to the end.  */
      53  
      54  #if MEMCPY_OK_FOR_FWD_MEMMOVE
      55        dest = memcpy (dest, src, len);
      56  #else
      57        /* If there not too few bytes to copy, use word copy.  */
      58        if (len >= OP_T_THRES)
      59  	{
      60  	  /* Copy just a few bytes to make DSTP aligned.  */
      61  	  len -= (-dstp) % OPSIZ;
      62  	  BYTE_COPY_FWD (dstp, srcp, (-dstp) % OPSIZ);
      63  
      64  	  /* Copy whole pages from SRCP to DSTP by virtual address
      65  	     manipulation, as much as possible.  */
      66  
      67  	  PAGE_COPY_FWD_MAYBE (dstp, srcp, len, len);
      68  
      69  	  /* Copy from SRCP to DSTP taking advantage of the known
      70  	     alignment of DSTP.  Number of bytes remaining is put
      71  	     in the third argument, i.e. in LEN.  This number may
      72  	     vary from machine to machine.  */
      73  
      74  	  WORD_COPY_FWD (dstp, srcp, len, len);
      75  
      76  	  /* Fall out and copy the tail.  */
      77  	}
      78  
      79        /* There are just a few bytes to copy.  Use byte memory operations.  */
      80        BYTE_COPY_FWD (dstp, srcp, len);
      81  #endif /* MEMCPY_OK_FOR_FWD_MEMMOVE */
      82      }
      83    else
      84      {
      85        /* Copy from the end to the beginning.  */
      86        srcp += len;
      87        dstp += len;
      88  
      89        /* If there not too few bytes to copy, use word copy.  */
      90        if (len >= OP_T_THRES)
      91  	{
      92  	  /* Copy just a few bytes to make DSTP aligned.  */
      93  	  len -= dstp % OPSIZ;
      94  	  BYTE_COPY_BWD (dstp, srcp, dstp % OPSIZ);
      95  
      96  	  /* Copy from SRCP to DSTP taking advantage of the known
      97  	     alignment of DSTP.  Number of bytes remaining is put
      98  	     in the third argument, i.e. in LEN.  This number may
      99  	     vary from machine to machine.  */
     100  
     101  	  WORD_COPY_BWD (dstp, srcp, len, len);
     102  
     103  	  /* Fall out and copy the tail.  */
     104  	}
     105  
     106        /* There are just a few bytes to copy.  Use byte memory operations.  */
     107        BYTE_COPY_BWD (dstp, srcp, len);
     108      }
     109  
     110    RETURN (dest);
     111  }
     112  #ifndef memmove
     113  libc_hidden_builtin_def (memmove)
     114  #endif