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  1. #include <stdio.h>
  2. #include <assert.h>
  3.  
  4. static int len(unsigned int u)
  5. {
  6. 	assert(u < 0xFFFFFFFFU);
  7. 	const int lb = __builtin_clz(u);
  8. 	const int num_bits = 32 - lb;
  9. 	const int ret =  (num_bits + 7) / 8;
  10. 	return ret;
  11. }
  12.  
  13. int main(void) {
  14. 	unsigned int u;
  15. 	for(u = 1U; u < 256U; ++u) assert(len(u) == 1);
  16. 	for(u = 256U; u < 256U * 256U; ++u) assert(len(u) == 2);
  17. 	for(u = 256U * 256U; u < 256U * 256U * 256U; ++u) assert(len(u) == 3);
  18. 	for(u = 256U * 256U * 256U; u < 256U * 256U * 256U * 256U; ++u) assert(len(u) == 4);
  19. 	// [...]
  20. 	return 0;
  21. }
  22.  
Success #stdin #stdout 0s 9296KB
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https://ideone.com/H1f1o7
language:
C (gcc 8.3)
created:
8 years ago
visibility:
public

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