stpncpy.c 769 B

1234567891011121314151617181920212223242526272829303132
  1. #include <string.h>
  2. #include <stdlib.h>
  3. #include <stdint.h>
  4. #include <limits.h>
  5. #include "libc.h"
  6. #define ALIGN (sizeof(size_t)-1)
  7. #define ONES ((size_t)-1/UCHAR_MAX)
  8. #define HIGHS (ONES * (UCHAR_MAX/2+1))
  9. #define HASZERO(x) ((x)-ONES & ~(x) & HIGHS)
  10. char *__stpncpy(char *d, const char *s, size_t n)
  11. {
  12. size_t *wd;
  13. const size_t *ws;
  14. if (((uintptr_t)s & ALIGN) == ((uintptr_t)d & ALIGN)) {
  15. for (; ((uintptr_t)s & ALIGN) && n && (*d=*s); n--, s++, d++);
  16. if (!n || !*s) goto tail;
  17. wd=(void *)d; ws=(const void *)s;
  18. for (; n>=sizeof(size_t) && !HASZERO(*ws);
  19. n-=sizeof(size_t), ws++, *wd++) *wd = *ws;
  20. d=(void *)wd; s=(const void *)ws;
  21. }
  22. for (; n && (*d=*s); n--, s++, d++);
  23. tail:
  24. memset(d, 0, n);
  25. return d;
  26. }
  27. weak_alias(__stpncpy, stpncpy);