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  1. #include <cstdint>
  2. #include <cstdio>
  3.  
  4. using namespace std;
  5.  
  6. struct Q_23_8
  7. {
  8.     int32_t fractional :  8;
  9.     int32_t integral   : 23;
  10. };
  11.  
  12. static_assert(sizeof(Q_23_8) == sizeof(int32_t), "Sizes differ!");
  13.  
  14. Q_23_8 operator*(const Q_23_8& lhs, const Q_23_8& rhs)
  15. {
  16.     // Math is incorrect here, of course!
  17.     return {
  18.         lhs.fractional * rhs.fractional,
  19.         lhs.integral * rhs.integral };
  20. }
  21.  
  22. int main()
  23. {
  24.     int32_t encoded[2] = { (321 << 8) + 11, 0 };
  25.     printf("encoded = %08x\n", encoded[0]);
  26.  
  27.     Q_23_8* decoded = reinterpret_cast<Q_23_8*>(encoded);
  28.     decoded[1] = decoded[0] * decoded[0];
  29.     printf("decoded = %06x.%02x\n", decoded[0].integral, decoded[0].fractional);
  30.     printf("result  = %06x.%02x\n", decoded[1].integral, decoded[1].fractional);
  31. }
Success #stdin #stdout 0s 3140KB
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stdin
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Standard input is empty
stdout
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encoded = 0001410b
decoded = 000141.0b
result  = 019281.79
https://ideone.com/X177fQ
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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