memmove() in C

Introduction: In this article we are discuss about the memmove() function in C. This function transfers memory blocks from one location to another. The memmove() function is declared in the string.h header file.

Returns a pointer to the target. The memmove() feature works when objects overlap.

Syntax of the memmove() function in C:

The syntax of the memmove() function in C is given below –

void *memmove(void *str1, const void *str2, size_t n);  

Header file of the memmove() function in C:

The header file of the memmove() function in C is string.h. Which is written below –

#include <string.h>

Parameters of the memmove() function in C:

str1: str1 is a pointer to a memory block where the contents of the source memory block will be copied. The pointer data type is *void.

str2: str2 is a pointer to the memory block whose contents will be copied to the destination memory block. The pointer data type is *void.

n: Number of data bytes to move from one place to another.

Return value of the memmove() function in C:

Returns a pointer to the target of the memory block. According to the syntax, this is str1.

Example 1: Here, we implement of memmove() function in C. We have written a program below using this function –

#include <stdio.h>
#include <string.h>
int main ()
{
char dest [] = “Oldstring”;
const char src [] = “Newstring”;
printf (“Before the memmove dest = %s, src = %s\n”, dest, src);
memmove (dest, src, 9);
printf (“After the memmove dest = %s, src = %s\n”, dest, src);
return 0;
}

Result: We compile the above program and also run this program. After a successful compilation, the result is given below:

Before the memmove dest = Oldstring, src = Newstring
After the memmove dest = Newstring, src = Newstring

Example 2: Here, we implement of memmove() function in C. We have written another program below using this function –

#include <stdio.h>
#include <string.h>
int main ()
{
char str1 [] = “Priya”;
char str2 [] = “Biswas”;
puts (“str1 before memmove”);
puts (str1);
memmove (str1, str2, sizeof(str2));
puts (“\nstr1 after memmove”);
puts (str1);
return 0; }

Result: We compile the above program and also run this program. After a successful compilation, the result is given below:

Str1 before memmove
Priya
Str1 after memmove
Biswas

Example 3: Here, we implement the memmove() function in C. Using this function, we have written another program below –

#include <string.h>  
#include <stdio.h>  
#include <time.h>  
#define BUFFERSIZE  (100 * 1024)  
#define LOOP 10000  
int main()  
{  
 char destn[BUFFERSIZE] = {0};  
char source[BUFFERSIZE] = {0};  
 int i = 0;  
 double t_spent;  
clock_t start, end;  
start = clock();  
 for ( i = 0; i < LOOP; i++)  
 {  
memmove(destn,source,BUFFERSIZE);  
}  
end = clock();  
t_spent = (double)(end - start) / CLOCKS_PER_SEC;  
 printf("memmove() took %f seconds to complete\n", t_spent);
start = clock();  
for ( i = 0; i < LOOP; i++)  
 {  
memcpy(destn,source,BUFFERSIZE);  
 }  
  end = clock();  
t_spent = (double)(end - start) / CLOCKS_PER_SEC;  
printf("memcpy() took %f seconds to complete\n", t_spent);  
return 0;  
}  

Result: We compile the above program and also run this program. After a successful compilation the result is given below:

memmove() took 0.098000 seconds to complete
memcpy() took 0.083000 seconds to complete

What is the difference between memcpy() function and memmove() function in C?

The memcpy() function copies the data from one place to another. On the other hand, the memmove() function first copies the data to an intermediate buffer, then from the buffer to the destination. The memcpy() function causes problems with duplicate strings. The main difference in behaviour between the memmove() and memcpy() functions is that the memmove() function is bidirectional and the memcpy() function is unidirectional.

So, in this article, we clearly discuss the memmove() function in C. We discuss this function’s syntax, header file, parameters, and return value. We also give examples of the memmove() function in C and share the output of the programs.