basics/sources/string.c

   1 #include <string.h>
   2 #include <stdint.h>
   3
   4 static void *copy_forward(void *restrict dst, const void *restrict src, size_t n) {
   5     char *d = (char *)dst;
   6     const char *s = (const char *)src;
   7     while (n-- != 0) {
   8         *d++ = *s++;
   9     }
  10     return dst;
  11 }
  12
  13 static void *copy_backward(void *restrict dst, const void *restrict src, size_t n) {
  14     char *d = (char *)dst;
  15     const char *s = (const char *)src;
  16     d += n;
  17     s += n;
  18     while (n-- != 0) {
  19         *--d = *--s;
  20     }
  21     return dst;
  22 }
  23
  24 void *memcpy(void *restrict dst, const void *restrict src, size_t n) {
  25     return copy_forward(dst, src, n);
  26 }
  27
  28 void *memmove(void *dst, const void *src, size_t n) {
  29     if ((uintptr_t)dst - (uintptr_t)src >= n) {
  30         return copy_forward(dst, src, n);
  31     }
  32     return copy_backward(dst, src, n);
  33 }
  34
  35 void *memset(void *restrict dst, int c, size_t n) {
  36     char *d = (char *)dst;
  37     while (n-- != 0) {
  38         *d++ = c;
  39     }
  40     return dst;
  41 }