Memswap implementation in ISO C.

memswap.h

#ifndef MEMSWAP_H
#define MEMSWAP_H

static inline void
memswap(void *restrict aptr, void *restrict bptr, size_t len)
{
    register unsigned char *a = aptr;
    register unsigned char *b = bptr;
    register unsigned char t;
  
    while (len--)
    {
        t = *a;
        *a++ = *b;
        *b++ = t;
    }
}

#endif /* MEMSWAP_H */