memcpy

Copies characters between buffers.

void *memcpy( void *dest, const void *src, size_t count );

For additional compatibility information, see Compatibility in the Introduction.

Libraries

Return Value

memcpy returns the value of dest.

Parameters

dest

New buffer

src

Buffer to copy from

count

Number of characters to copy

Remarks

The memcpy function copies count bytes of src to dest. If the source and destination overlap, this function does not ensure that the original source bytes in the overlapping region are copied before being overwritten. Use memmove to handle overlapping regions.

Example

/* MEMCPY.C: Illustrate overlapping copy: memmove
 * handles it correctly; memcpy does not.
 */

#include <memory.h>
#include <string.h>
#include <stdio.h>

char string1[60] = "The quick brown dog jumps over the lazy fox";
char string2[60] = "The quick brown fox jumps over the lazy dog";
/*                           1         2         3         4         5
 *                  12345678901234567890123456789012345678901234567890
 */

void main( void )
{
   printf( "Function:\tmemcpy without overlap\n" );
   printf( "Source:\t\t%s\n", string1 + 40 );
   printf( "Destination:\t%s\n", string1 + 16 );
   memcpy( string1 + 16, string1 + 40, 3 );
   printf( "Result:\t\t%s\n", string1 );
   printf( "Length:\t\t%d characters\n\n", strlen( string1 ) );

   /* Restore string1 to original contents */
   memcpy( string1 + 16, string2 + 40, 3 );

   printf( "Function:\tmemmove with overlap\n" );
   printf( "Source:\t\t%s\n", string2 + 4 );
   printf( "Destination:\t%s\n", string2 + 10 );
   memmove( string2 + 10, string2 + 4, 40 );
   printf( "Result:\t\t%s\n", string2 );
   printf( "Length:\t\t%d characters\n\n", strlen( string2 ) );

   printf( "Function:\tmemcpy with overlap\n" );
   printf( "Source:\t\t%s\n", string1 + 4 );
   printf( "Destination:\t%s\n", string1 + 10 );
   memcpy( string1 + 10, string1 + 4, 40 );
   printf( "Result:\t\t%s\n", string1 );
   printf( "Length:\t\t%d characters\n\n", strlen( string1 ) );
}

Output

Function:   memcpy without overlap
Source:      fox
Destination:   dog jumps over the lazy fox
Result:      The quick brown fox jumps over the lazy fox
Length:      43 characters

Function:   memmove with overlap
Source:      quick brown fox jumps over the lazy dog
Destination:   brown fox jumps over the lazy dog
Result:      The quick quick brown fox jumps over the lazy dog
Length:      49 characters

Function:   memcpy with overlap
Source:      quick brown dog jumps over the lazy fox
Destination:   brown dog jumps over the lazy fox
Result:      The quick quick brown dog jumps over the lazy fox
Length:      49 characters

Buffer Manipulation Routines

See Also   _memccpy, memchr, memcmp, memmove, memset, strcpy, strncpy