Blame string/memcpy.c

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/* Copy memory to memory until the specified number of bytes
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   has been copied.  Overlap is NOT handled correctly.
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   Copyright (C) 1991-2018 Free Software Foundation, Inc.
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   This file is part of the GNU C Library.
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   Contributed by Torbjorn Granlund (tege@sics.se).
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   The GNU C Library is free software; you can redistribute it and/or
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   modify it under the terms of the GNU Lesser General Public
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   License as published by the Free Software Foundation; either
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   version 2.1 of the License, or (at your option) any later version.
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   The GNU C Library is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   Lesser General Public License for more details.
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   You should have received a copy of the GNU Lesser General Public
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   License along with the GNU C Library; if not, see
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   <http://www.gnu.org/licenses/>.  */
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#include <string.h>
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#include <memcopy.h>
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#undef memcpy
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void *
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memcpy (void *dstpp, const void *srcpp, size_t len)
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{
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  unsigned long int dstp = (long int) dstpp;
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  unsigned long int srcp = (long int) srcpp;
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  /* Copy from the beginning to the end.  */
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  /* If there not too few bytes to copy, use word copy.  */
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  if (len >= OP_T_THRES)
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    {
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      /* Copy just a few bytes to make DSTP aligned.  */
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      len -= (-dstp) % OPSIZ;
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      BYTE_COPY_FWD (dstp, srcp, (-dstp) % OPSIZ);
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      /* Copy whole pages from SRCP to DSTP by virtual address manipulation,
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	 as much as possible.  */
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      PAGE_COPY_FWD_MAYBE (dstp, srcp, len, len);
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      /* Copy from SRCP to DSTP taking advantage of the known alignment of
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	 DSTP.  Number of bytes remaining is put in the third argument,
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	 i.e. in LEN.  This number may vary from machine to machine.  */
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      WORD_COPY_FWD (dstp, srcp, len, len);
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      /* Fall out and copy the tail.  */
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    }
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  /* There are just a few bytes to copy.  Use byte memory operations.  */
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  BYTE_COPY_FWD (dstp, srcp, len);
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  return dstpp;
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}
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libc_hidden_builtin_def (memcpy)