memcpy, _fmemcpy

Description

Copy characters between buffers.

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

void __far * __far _fmemcpy( void __far *dest, const void __far *src,
size_t count );

Remarks

The memcpy and _fmemcpy functions copy count bytes of src to dest. If the source and destination overlap, these functions do not ensure that the original source bytes in the overlapping region are copied before being overwritten. Use memmove to handle overlapping regions.

The _fmemcpy function is a model-independent (large-model) form of the memcpy function. It can be called from any point in any program.

There is a semantic difference between the function version of memcpy and its intrinsic version. The function version supports huge pointers in compact-, large-, and huge-model programs, but the intrinsic version does not.

Return Value

The memcpy and _fmemcpy functions return the value of dest.

Compatibility

memcpy

Standards:ANSI, UNIX

16-Bit:DOS, QWIN, WIN, WIN DLL

32-Bit:DOS32X

_fmemcpy

Standards:None

16-Bit:DOS, QWIN, WIN, WIN DLL

32-Bit:None

See Also

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

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 quick quick quick quick quick quick

Length: 50 characters