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  1. #include <iostream>
  2. #include <cstdint>
  3.  
  4. uint32_t getBits(const void *Data, uint32_t DataLen, uint32_t StartBit, uint8_t NumBits)
  5. {
  6. 	uint32_t Result = 0;
  7. 	if (DataLen != 0)
  8. 	{
  9. 		const uint8_t *pData = &(static_cast<const uint8_t*>(Data)[StartBit / 8]);
  10. 		uint8_t b = *pData;
  11. 		int BitOffset = 7 - (StartBit % 8);
  12. 		for(int i = 0; i < NumBits; ++i)
  13. 		{
  14. 			Result <<= 1;
  15. 			Result |= ((b >> BitOffset) & 0x01);
  16. 			if (--BitOffset < 0)
  17. 			{
  18. 				b = *(++pData);
  19. 				BitOffset = 7;
  20. 			}
  21. 		}
  22. 	}
  23. 	return Result;
  24. }
  25.  
  26. int main() {
  27. 	uint8_t arr[] = {0x00, 0x00, 0xFF, 0xF1, 0x6D, 0xA2, 0x00, 0x00};
  28. 	uint32_t value = getBits(arr, 8, 17, 13);
  29. 	std::cout << value << " (" << std::hex << value << ")";
  30. 	return 0;
  31. }
Success #stdin #stdout 0s 4520KB
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8188 (1ffc)
https://ideone.com/d2jTKM
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
public

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