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  1. #include <stdio.h>
  2. #include <stdint.h>
  3.  
  4. #define LOW(exp)  ((exp) & 0x00FF)
  5. #define HIGH(exp) (((exp) & 0xFF00) >> 8)
  6.  
  7.  
  8. uint16_t prng(uint16_t v) {
  9.  
  10.     uint16_t low  = LOW(v);
  11.     uint16_t high = HIGH(v);
  12.  
  13.     uint16_t mul_low  = low  * 5;
  14.     uint16_t  mul_high = high * 5;
  15.  
  16.     // need to check for overflow, since final addition is adc as well
  17.     uint16_t v1    = LOW(mul_high) + HIGH(mul_low) + 1;
  18.     uint8_t  carry = HIGH(v1) & 0b00000001;
  19.  
  20.     uint16_t v2 = (LOW(v1) << 8) + LOW(mul_low);
  21.  
  22.     return (v2 + 0b00010001 + carry);
  23. }
  24.  
  25. int main()
  26. {
  27.     printf("%d\n", prng(13054));
  28.     printf("%d\n", prng(13055));
  29.     printf("%d\n", prng(13056));
  30.     printf("%d\n", prng(13057));
  31.  
  32.     printf("---\n");
  33.  
  34.     printf("%d\n", prng(13310));
  35.     printf("%d\n", prng(13311));
  36.     printf("%d\n", prng(13312));
  37.     printf("%d\n", prng(13313));
  38.  
  39.     return 0;
  40. }
Success #stdin #stdout 0s 2160KB
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1288
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https://ideone.com/MSkbSa
language:
C (gcc 8.3)
created:
8 years ago
visibility:
secret

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