memmove_s, wmemmove_s

Article
11/16/2012

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

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

Change History

Date	History	Reason
July 2009	Corrected the code sample.	Content bug fix.

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