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glibc  2.9
Functions
memmove_chk.c File Reference
#include <string.h>
#include <memcopy.h>
#include <pagecopy.h>

Go to the source code of this file.

Functions

void * __memmove_chk (void *dest, const void *src, size_t len, size_t destlen)

Function Documentation

void* __memmove_chk ( void *  dest,
const void *  src,
size_t  len,
size_t  destlen 
)

Definition at line 27 of file memmove_chk.c.

{
  if (__builtin_expect (destlen < len, 0))
    __chk_fail ();

  unsigned long int dstp = (long int) dest;
  unsigned long int srcp = (long int) src;

  /* This test makes the forward copying code be used whenever possible.
     Reduces the working set.  */
  if (dstp - srcp >= len)   /* *Unsigned* compare!  */
    {
      /* Copy from the beginning to the end.  */

      /* If there not too few bytes to copy, use word copy.  */
      if (len >= OP_T_THRES)
       {
         /* Copy just a few bytes to make DSTP aligned.  */
         len -= (-dstp) % OPSIZ;
         BYTE_COPY_FWD (dstp, srcp, (-dstp) % OPSIZ);

         /* Copy whole pages from SRCP to DSTP by virtual address
            manipulation, as much as possible.  */

         PAGE_COPY_FWD_MAYBE (dstp, srcp, len, len);

         /* Copy from SRCP to DSTP taking advantage of the known
            alignment of DSTP.  Number of bytes remaining is put
            in the third argument, i.e. in LEN.  This number may
            vary from machine to machine.  */

         WORD_COPY_FWD (dstp, srcp, len, len);

         /* Fall out and copy the tail.  */
       }

      /* There are just a few bytes to copy.  Use byte memory operations.  */
      BYTE_COPY_FWD (dstp, srcp, len);
    }
  else
    {
      /* Copy from the end to the beginning.  */
      srcp += len;
      dstp += len;

      /* If there not too few bytes to copy, use word copy.  */
      if (len >= OP_T_THRES)
       {
         /* Copy just a few bytes to make DSTP aligned.  */
         len -= dstp % OPSIZ;
         BYTE_COPY_BWD (dstp, srcp, dstp % OPSIZ);

         /* Copy from SRCP to DSTP taking advantage of the known
            alignment of DSTP.  Number of bytes remaining is put
            in the third argument, i.e. in LEN.  This number may
            vary from machine to machine.  */

         WORD_COPY_BWD (dstp, srcp, len, len);

         /* Fall out and copy the tail.  */
       }

      /* There are just a few bytes to copy.  Use byte memory operations.  */
      BYTE_COPY_BWD (dstp, srcp, len);
    }

  return dest;
}

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