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, 1995, 1996, 1997, 2003 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, write to the Free
  19    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  20    02111-1307 USA.  */
  21
  22 #include <string.h>
  23 #include <memcopy.h>
  24 #include <pagecopy.h>
  25
  26 /* All this is so that bcopy.c can #include
  27    this file after defining some things.  */
  28 #ifndef a1
  29 #define a1      dest    /* First arg is DEST.  */
  30 #define a1const
  31 #define a2      src     /* Second arg is SRC.  */
  32 #define a2const const
  33 #undef memmove
  34 #endif
  35 #if     !defined(RETURN) || !defined(rettype)
  36 #define RETURN(s)       return (s)      /* Return DEST.  */
  37 #define rettype         void *
  38 #endif
  39
  40
  41 rettype
  42 memmove (a1, a2, len)
  43      a1const void *a1;
  44      a2const void *a2;
  45      size_t len;
  46 {
  47   unsigned long int dstp = (long int) dest;
  48   unsigned long int srcp = (long int) src;
  49
  50   /* This test makes the forward copying code be used whenever possible.
  51      Reduces the working set.  */
  52   if (dstp - srcp >= len)       /* *Unsigned* compare!  */
  53     {
  54       /* Copy from the beginning to the end.  */
  55
  56       /* If there not too few bytes to copy, use word copy.  */
  57       if (len >= OP_T_THRES)
  58         {
  59           /* Copy just a few bytes to make DSTP aligned.  */
  60           len -= (-dstp) % OPSIZ;
  61           BYTE_COPY_FWD (dstp, srcp, (-dstp) % OPSIZ);
  62
  63           /* Copy whole pages from SRCP to DSTP by virtual address
  64              manipulation, as much as possible.  */
  65
  66           PAGE_COPY_FWD_MAYBE (dstp, srcp, len, len);
  67
  68           /* Copy from SRCP to DSTP taking advantage of the known
  69              alignment of DSTP.  Number of bytes remaining is put
  70              in the third argument, i.e. in LEN.  This number may
  71              vary from machine to machine.  */
  72
  73           WORD_COPY_FWD (dstp, srcp, len, len);
  74
  75           /* Fall out and copy the tail.  */
  76         }
  77
  78       /* There are just a few bytes to copy.  Use byte memory operations.  */
  79       BYTE_COPY_FWD (dstp, srcp, len);
  80     }
  81   else
  82     {
  83       /* Copy from the end to the beginning.  */
  84       srcp += len;
  85       dstp += len;
  86
  87       /* If there not too few bytes to copy, use word copy.  */
  88       if (len >= OP_T_THRES)
  89         {
  90           /* Copy just a few bytes to make DSTP aligned.  */
  91           len -= dstp % OPSIZ;
  92           BYTE_COPY_BWD (dstp, srcp, dstp % OPSIZ);
  93
  94           /* Copy from SRCP to DSTP taking advantage of the known
  95              alignment of DSTP.  Number of bytes remaining is put
  96              in the third argument, i.e. in LEN.  This number may
  97              vary from machine to machine.  */
  98
  99           WORD_COPY_BWD (dstp, srcp, len, len);
 100
 101           /* Fall out and copy the tail.  */
 102         }
 103
 104       /* There are just a few bytes to copy.  Use byte memory operations.  */
 105       BYTE_COPY_BWD (dstp, srcp, len);
 106     }
 107
 108   RETURN (dest);
 109 }
 110 #ifndef memmove
 111 libc_hidden_builtin_def (memmove)
 112 #endif