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  1. #include <stdio.h>
  2. #include <time.h> 
  3. #include <string.h>
  4.  
  5. int main(void) { 
  6.     unsigned int a1 = 0xf3040506;
  7.     unsigned int *a = ( unsigned int *)&a1;
  8.     unsigned char *m  = (unsigned char* )&a1;
  9.     unsigned long forcount = 300000000  ,i;
  10.     unsigned char r , g , b , al;
  11.  
  12.  
  13. 	printf("%x\n", *a);
  14.  
  15.  
  16. 	printf("r i %x\n", m[0]);
  17. 	printf("g i %x\n", m[1]);
  18. 	printf("b i %x\n", m[2]);
  19. 	printf("a i %x\n", m[3]);
  20.  
  21.  
  22.  
  23. 	printf("r p %x\n", (unsigned char) *a );
  24. 	printf("g p %x\n", (unsigned char) (*a >> 8));
  25. 	printf("b p %x\n", (unsigned char) (*a >> 16) );
  26. 	printf("a p %x\n", (unsigned char) (*a >> 24) );
  27.  
  28.  
  29.     clock_t t;
  30.  
  31.     t = clock();
  32.  
  33.     for(i = 0;i < forcount ;i++)   
  34.     {   
  35. 	  r =  m[0];
  36. 	  g =  m[1];
  37. 	  b =  m[2];
  38. 	  al = m[3];
  39.     }   
  40.     t = clock() - t ;
  41.  
  42.     printf ("pointer take (%f seconds).\n",((float)t)/CLOCKS_PER_SEC);
  43.  
  44.  
  45.     t = clock();
  46.  
  47.     for(i = 0;i < forcount ;i++)   
  48.     {   
  49. 	  r = (unsigned char) *a;
  50. 	  g = (unsigned char) (*a >> 8);
  51. 	  b = (unsigned char) (*a >> 16);
  52. 	  al = (unsigned char) (*a >> 24);
  53.     }   
  54.     t = clock() - t ;
  55.  
  56.     printf ("shift take (%f seconds).\n",((float)t)/CLOCKS_PER_SEC);
  57.  
  58.     m[0] = r;
  59.     m[0] = g;
  60.     m[0] = b;
  61.     m[0] = al;
  62.     return 0;
  63. }
Success #stdin #stdout 3.78s 2248KB
comments (?)
stdin
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Standard input is empty
stdout
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f3040506
r i 6
g i 5
b i 4
a i f3
r p 6
g p 5
b p 4
a p f3
pointer take (1.770000 seconds).
shift take (2.010000 seconds).
https://ideone.com/97W4lC
language:
C99 (gcc 8.3)
created:
10 years ago
visibility:
secret

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