Subversion Repositories NedoOS

Rev

Blame | Last modification | View Log | Download

  1. // Copyright 2008 Google Inc.
  2. // All Rights Reserved.
  3. //
  4. // Redistribution and use in source and binary forms, with or without
  5. // modification, are permitted provided that the following conditions are
  6. // met:
  7. //
  8. //     * Redistributions of source code must retain the above copyright
  9. // notice, this list of conditions and the following disclaimer.
  10. //     * Redistributions in binary form must reproduce the above
  11. // copyright notice, this list of conditions and the following disclaimer
  12. // in the documentation and/or other materials provided with the
  13. // distribution.
  14. //     * Neither the name of Google Inc. nor the names of its
  15. // contributors may be used to endorse or promote products derived from
  16. // this software without specific prior written permission.
  17. //
  18. // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19. // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20. // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  21. // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  22. // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  23. // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  24. // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25. // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26. // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27. // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  28. // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29.  
  30.  
  31.  
  32. // This provides interface PrimeTable that determines whether a number is a
  33. // prime and determines a next prime number. This interface is used
  34. // in Google Test samples demonstrating use of parameterized tests.
  35.  
  36. #ifndef GTEST_SAMPLES_PRIME_TABLES_H_
  37. #define GTEST_SAMPLES_PRIME_TABLES_H_
  38.  
  39. #include <algorithm>
  40.  
  41. // The prime table interface.
  42. class PrimeTable {
  43.  public:
  44.   virtual ~PrimeTable() {}
  45.  
  46.   // Returns true iff n is a prime number.
  47.   virtual bool IsPrime(int n) const = 0;
  48.  
  49.   // Returns the smallest prime number greater than p; or returns -1
  50.   // if the next prime is beyond the capacity of the table.
  51.   virtual int GetNextPrime(int p) const = 0;
  52. };
  53.  
  54. // Implementation #1 calculates the primes on-the-fly.
  55. class OnTheFlyPrimeTable : public PrimeTable {
  56.  public:
  57.   virtual bool IsPrime(int n) const {
  58.     if (n <= 1) return false;
  59.  
  60.     for (int i = 2; i*i <= n; i++) {
  61.       // n is divisible by an integer other than 1 and itself.
  62.       if ((n % i) == 0) return false;
  63.     }
  64.  
  65.     return true;
  66.   }
  67.  
  68.   virtual int GetNextPrime(int p) const {
  69.     for (int n = p + 1; n > 0; n++) {
  70.       if (IsPrime(n)) return n;
  71.     }
  72.  
  73.     return -1;
  74.   }
  75. };
  76.  
  77. // Implementation #2 pre-calculates the primes and stores the result
  78. // in an array.
  79. class PreCalculatedPrimeTable : public PrimeTable {
  80.  public:
  81.   // 'max' specifies the maximum number the prime table holds.
  82.   explicit PreCalculatedPrimeTable(int max)
  83.       : is_prime_size_(max + 1), is_prime_(new bool[max + 1]) {
  84.     CalculatePrimesUpTo(max);
  85.   }
  86.   virtual ~PreCalculatedPrimeTable() { delete[] is_prime_; }
  87.  
  88.   virtual bool IsPrime(int n) const {
  89.     return 0 <= n && n < is_prime_size_ && is_prime_[n];
  90.   }
  91.  
  92.   virtual int GetNextPrime(int p) const {
  93.     for (int n = p + 1; n < is_prime_size_; n++) {
  94.       if (is_prime_[n]) return n;
  95.     }
  96.  
  97.     return -1;
  98.   }
  99.  
  100.  private:
  101.   void CalculatePrimesUpTo(int max) {
  102.     ::std::fill(is_prime_, is_prime_ + is_prime_size_, true);
  103.     is_prime_[0] = is_prime_[1] = false;
  104.  
  105.     // Checks every candidate for prime number (we know that 2 is the only even
  106.     // prime).
  107.     for (int i = 2; i*i <= max; i += i%2+1) {
  108.       if (!is_prime_[i]) continue;
  109.  
  110.       // Marks all multiples of i (except i itself) as non-prime.
  111.       // We are starting here from i-th multiplier, because all smaller
  112.       // complex numbers were already marked.
  113.       for (int j = i*i; j <= max; j += i) {
  114.         is_prime_[j] = false;
  115.       }
  116.     }
  117.   }
  118.  
  119.   const int is_prime_size_;
  120.   bool* const is_prime_;
  121.  
  122.   // Disables compiler warning "assignment operator could not be generated."
  123.   void operator=(const PreCalculatedPrimeTable& rhs);
  124. };
  125.  
  126. #endif  // GTEST_SAMPLES_PRIME_TABLES_H_
  127.