memmove_s, wmemmove_s

Article
06/05/2017

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The latest version of this topic can be found at memmove_s, wmemmove_s.

Moves one buffer to another. These are versions of memmove, wmemmove with security enhancements as described in Security Features in the CRT.

Syntax

  
      errno_t memmove_s(  
   void *dest,  
   size_t numberOfElements,  
   const void *src,  
   size_t count  
);  
errno_t wmemmove_s(  
   wchar_t *dest,  
   size_t numberOfElements,  
   const wchar_t *src,  
   size_t count  
);

Parameters

dest
Destination object.

numberOfElements
Size of the destination buffer.

src
Source object.

count
Number of bytes (memmove_s) or characters (wmemmove_s) to copy.

Return Value

Zero if successful; an error code on failure

Error Conditions

`dest`	`numberOfElements`	`src`	Return value	Contents of `dest`
`NULL`	any	any	`EINVAL`	not modified
any	any	`NULL`	`EINVAL`	not modified
any	< `count`	any	`ERANGE`	not modified

Remarks

Copies count bytes of characters from src to dest. If some regions of the source area and the destination overlap, memmove_s ensures that the original source bytes in the overlapping region are copied before being overwritten.

If dest or if src is a null pointer, or if the destination string is too small, these functions invoke an invalid parameter handler, as described in Parameter Validation . If execution is allowed to continue, these functions return EINVAL and set errno to EINVAL.

Requirements

Routine	Required header
`memmove_s`	<string.h>
`wmemmove_s`	<wchar.h>

For additional compatibility information, see Compatibility in the Introduction.

Example

// crt_memmove_s.c  
//  
// The program demonstrates the   
// memmove_s function which works as expected  
// for moving overlapping regions.  
  
#include <stdio.h>  
#include <string.h>  
  
int main()  
{  
   char str[] = "0123456789";  
  
   printf("Before: %s\n", str);  
  
   // Move six bytes from the start of the string  
   // to a new position shifted by one byte. To protect against  
   // buffer overrun, the secure version of memmove requires the  
   // the length of the destination string to be specified.   
  
   memmove_s((str + 1), strnlen(str + 1, 10), str, 6);   
  
   printf_s(" After: %s\n", str);  
}

Output

Before: 0123456789  
 After: 0012345789

.NET Framework Equivalent

System::Buffer::BlockCopy

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