home | help 
std::memmove(3) 	       C++ Standard Libary		 std::memmove(3)

NAME
     std::memmove - std::memmove

Synopsis
	Defined in header <cstring>
	void* memmove( void* dest, const void* src, std::size_t count );

	Copies	count characters from the object pointed to by src to the object
     pointed to
	by dest. Both objects are reinterpreted as arrays of unsigned char.

	The objects may overlap: copying takes place as if the	characters  were
     copied to a
	temporary  character  array and then the characters were copied from the
     array to
	dest.

	If either dest or src is an invalid or null pointer, the behavior is un-
     defined, even
	if count is zero.

	If the objects are potentially-overlapping or not TriviallyCopyable, the
     behavior of
	memmove is not specified and may be undefined.

Parameters
	dest  - pointer to the memory location to copy to
	src   - pointer to the memory location to copy from
	count - number of bytes to copy

Return value
	dest

Notes
	std::memmove may be used to implicitly create objects in the destination
     buffer.

	Despite being specified "as if" a temporary buffer is used,  actual  im-
     plementations
	of  this  function  do not incur the overhead of double copying or extra
     memory. For
	small count, it may load up and write out registers; for larger  blocks,
     a common
	approach  (glibc and bsd libc) is to copy bytes forwards from the begin-
     ning of the
	buffer if the destination starts before the source, and  backwards  from
     the end
	otherwise,  with  a fall back to std::memcpy when there is no overlap at
     all.

	Where strict aliasing prohibits examining the same memory as  values  of
     two different
	types, std::memmove may be used to convert the values.

Example
     // Run this code

      #include <cstring>
      #include <iostream>

      int main()
      {
	  char str[] = "1234567890";
	  std::cout << str << '\n';
	  std::memmove(str  + 4, str + 3, 3); // copies from [4, 5, 6] to [5, 6,
     7]
	  std::cout << str << '\n';
      }

Output:
      1234567890
      1234456890

See also
	memcpy		      copies one buffer to another
			      (function)
	memset		      fills a buffer with a character
			      (function)
			      copies a certain amount of wide characters between
     two,
	wmemmove	      possibly overlapping, arrays
			      (function)
	copy		      copies a range of elements to a new location
	copy_if 	      (function template)
	(C++11)
	copy_backward	      copies a range of elements in backwards order
			      (function template)
	is_trivially_copyable checks if a type is trivially copyable
	(C++11) 	      (class template)
	C documentation for
	memmove

http://cppreference.com 	   2024.06.10			 std::memmove(3)
home | help