memmove.c

标准c库代码,可以应用于各个系统提供了大量的基本函数

/*
FUNCTION
	<<memmove>>---move possibly overlapping memory

INDEX
	memmove

ANSI_SYNOPSIS
	#include <string.h>
	void *memmove(void *<[dst]>, const void *<[src]>, size_t <[length]>);

TRAD_SYNOPSIS
	#include <string.h>
	void *memmove(<[dst]>, <[src]>, <[length]>)
	void *<[dst]>;
	void *<[src]>;
	size_t <[length]>;

DESCRIPTION
	This function moves <[length]> characters from the block of
	memory starting at <<*<[src]>>> to the memory starting at
	<<*<[dst]>>>. <<memmove>> reproduces the characters correctly
	at <<*<[dst]>>> even if the two areas overlap.


RETURNS
	The function returns <[dst]> as passed.

PORTABILITY
<<memmove>> is ANSI C.

<<memmove>> requires no supporting OS subroutines.

QUICKREF
	memmove ansi pure
*/

#include <string.h>

/*SUPPRESS 20*/
_PTR
_DEFUN (memmove, (dst_void, src_void, length),
	_PTR dst_void _AND
	_CONST _PTR src_void _AND
	size_t length)
{
  char *dst = dst_void;
  _CONST char *src = src_void;

  if (src < dst && dst < src + length)
    {
      /* Have to copy backwards */
      src += length;
      dst += length;
      while (length--)
	{
	  *--dst = *--src;
	}
    }
  else
    {
      while (length--)
	{
	  *dst++ = *src++;
	}
    }

  return dst_void;
}