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  1. /* Shao Miller, 2012 */
  2.  
  3. #include <stdio.h>
  4. #include <stdlib.h>
  5.  
  6. void * pmemcpy(void * s1, const void * s2, size_t n);
  7. void * pmemmove(void * s1, const void * s2, size_t n);
  8.  
  9. int main(void) {
  10.     char test1[] = "0123456789";
  11.     char test2[] = "ABCDEFGHIJ";
  12.     char * t1;
  13.     char * t2;
  14.  
  15.     t1 = pmemmove(test1, test1 + 5, 5);
  16.     t2 = pmemmove(test2 + 5, test2, 5);
  17.     (void) t2;
  18.  
  19.     printf("%s\n%s\n", t1, test2);
  20.  
  21.     return EXIT_SUCCESS;
  22.   }
  23.  
  24. void * pmemcpy(void * s1, const void * s2, size_t n) {
  25.     unsigned char * dest;
  26.     const unsigned char * src;
  27.  
  28.     if (!s1 || !s2 || !n)
  29.       return s1;
  30.  
  31.     dest = s1;
  32.     src = s2;
  33.  
  34.     while (n--)
  35.       *dest++ = *src++;
  36.  
  37.     return s1;
  38.   }
  39.  
  40. /* Portability wins over performance, here */
  41. void * pmemmove(void * s1, const void * s2, size_t n) {
  42.     unsigned char * dest;
  43.     const unsigned char * src;
  44.     const unsigned char * src_end;
  45.  
  46.     if (!s1 || !s2 || !n || s1 == s2)
  47.       return s1;
  48.  
  49.     dest = s1;
  50.     src = s2;
  51.  
  52.     /* The only interesting case is where src < dest with overlap */
  53.     for (src_end = src + n; src < src_end; ++src) {
  54.         if (src == dest)
  55.           break;
  56.       }
  57.  
  58.     /* Is src > dest or non-overlapping? */
  59.     if (src == src_end)
  60.       return pmemcpy(s1, s2, n);
  61.  
  62.     /* Otherwise, src < dest with overlap */
  63.     dest += n;
  64.     src = src_end;
  65.  
  66.     while (n--)
  67.       *dest-- = *src--;
  68.  
  69.     return s1;
  70.   }
  71.  
Success #stdin #stdout 0.01s 1676KB
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stdin
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Standard input is empty
stdout
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5678956789
ABCDEABCDE
https://ideone.com/VbMskd
language:
C (gcc 8.3)
created:
11 years ago
visibility:
public

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