CareerCup

Basic first version - copies one byte at a time.

void memcpy(void* src, void* dst, size_t len)
{
char* p = (char*)src;
char* q = (char*)dst;
while(len--)
*p++ = *q++;
}

Version 2 - copies int at a time - better performance.

void memcpy(void* src, void* dst, size_t len)
{
/* Copy whatever can be copied as integers */

size_t nTimes = len/sizeof(int);
int* pIntSrc = (int*) src;
int* pIntDst = (int*) dst;

while( nTimes-- )
*pIntSrc++ = *pIntDst++;

/* copy the remainder */
nTimes = len % sizeof(int);
char* pCharSrc = (char*) pIntSrc;
char* pCharDst = (char*) pIntDst;

while( nTimes-- )
*pCharSrc++ = *pCharDst++;

/* Done */
}

int memcpy(void* dest,const void* src,int num)
{
while(num--)
*(char*)dest=*(char*)src;
dest=(char*)dest+1;
src=(char*)src+1;
}

what about overlap checking ?

instead of (int *) typecase use (long *) and take care for remaining bytes
take care for over lapping