string/memmove.c

   1 /* Copy memory to memory until the specified number of bytes
   2    has been copied.  Overlap is handled correctly.
   3    Copyright (C) 1991-2017 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5    Contributed by Torbjorn Granlund (tege@sics.se).
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 #include <string.h>
  22 #include <memcopy.h>
  23
  24 /* All this is so that bcopy.c can #include
  25    this file after defining some things.  */
  26 #ifndef a1
  27 #define a1      dest    /* First arg is DEST.  */
  28 #define a1const
  29 #define a2      src     /* Second arg is SRC.  */
  30 #define a2const const
  31 #undef memmove
  32 #endif
  33 #if     !defined(RETURN) || !defined(rettype)
  34 #define RETURN(s)       return (s)      /* Return DEST.  */
  35 #define rettype         void *
  36 #endif
  37
  38 #ifndef MEMMOVE
  39 #define MEMMOVE memmove
  40 #endif
  41
  42 rettype
  43 inhibit_loop_to_libcall
  44 MEMMOVE (a1const void *a1, a2const void *a2, size_t len)
  45 {
  46   unsigned long int dstp = (long int) dest;
  47   unsigned long int srcp = (long int) src;
  48
  49   /* This test makes the forward copying code be used whenever possible.
  50      Reduces the working set.  */
  51   if (dstp - srcp >= len)       /* *Unsigned* compare!  */
  52     {
  53       /* Copy from the beginning to the end.  */
  54
  55 #if MEMCPY_OK_FOR_FWD_MEMMOVE
  56       dest = memcpy (dest, src, len);
  57 #else
  58       /* If there not too few bytes to copy, use word copy.  */
  59       if (len >= OP_T_THRES)
  60         {
  61           /* Copy just a few bytes to make DSTP aligned.  */
  62           len -= (-dstp) % OPSIZ;
  63           BYTE_COPY_FWD (dstp, srcp, (-dstp) % OPSIZ);
  64
  65           /* Copy whole pages from SRCP to DSTP by virtual address
  66              manipulation, as much as possible.  */
  67
  68           PAGE_COPY_FWD_MAYBE (dstp, srcp, len, len);
  69
  70           /* Copy from SRCP to DSTP taking advantage of the known
  71              alignment of DSTP.  Number of bytes remaining is put
  72              in the third argument, i.e. in LEN.  This number may
  73              vary from machine to machine.  */
  74
  75           WORD_COPY_FWD (dstp, srcp, len, len);
  76
  77           /* Fall out and copy the tail.  */
  78         }
  79
  80       /* There are just a few bytes to copy.  Use byte memory operations.  */
  81       BYTE_COPY_FWD (dstp, srcp, len);
  82 #endif /* MEMCPY_OK_FOR_FWD_MEMMOVE */
  83     }
  84   else
  85     {
  86       /* Copy from the end to the beginning.  */
  87       srcp += len;
  88       dstp += len;
  89
  90       /* If there not too few bytes to copy, use word copy.  */
  91       if (len >= OP_T_THRES)
  92         {
  93           /* Copy just a few bytes to make DSTP aligned.  */
  94           len -= dstp % OPSIZ;
  95           BYTE_COPY_BWD (dstp, srcp, dstp % OPSIZ);
  96
  97           /* Copy from SRCP to DSTP taking advantage of the known
  98              alignment of DSTP.  Number of bytes remaining is put
  99              in the third argument, i.e. in LEN.  This number may
 100              vary from machine to machine.  */
 101
 102           WORD_COPY_BWD (dstp, srcp, len, len);
 103
 104           /* Fall out and copy the tail.  */
 105         }
 106
 107       /* There are just a few bytes to copy.  Use byte memory operations.  */
 108       BYTE_COPY_BWD (dstp, srcp, len);
 109     }
 110
 111   RETURN (dest);
 112 }
 113 #ifndef memmove
 114 libc_hidden_builtin_def (memmove)
 115 #endif