memdisk/memmove.c

   1 /*
   2  * memmove.c
   3  */
   4
   5 #include <string.h>
   6
   7 void *memmove(void *dst, const void *src, size_t n)
   8 {
   9         const char *p = src;
  10         char *q = dst;
  11 #if defined(__i386__) || defined(__x86_64__)
  12         if (q < p) {
  13                 asm volatile("cld; rep; movsb"
  14                              : "+c" (n), "+S"(p), "+D"(q));
  15         } else {
  16                 p += (n - 1);
  17                 q += (n - 1);
  18                 asm volatile("std; rep; movsb; cld"
  19                              : "+c" (n), "+S"(p), "+D"(q));
  20         }
  21 #else
  22         if (q < p) {
  23                 while (n--) {
  24                         *q++ = *p++;
  25                 }
  26         } else {
  27                 p += n;
  28                 q += n;
  29                 while (n--) {
  30                         *--q = *--p;
  31                 }
  32         }
  33 #endif
  34
  35         return dst;
  36 }