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 GOOGLETEST_SAMPLES_PRIME_TABLES_H_ 37 #define GOOGLETEST_SAMPLES_PRIME_TABLES_H_ 38 39 #include <algorithm> 40 41 // The prime table interface. 42 class PrimeTable { 43 public: ~PrimeTable()44 virtual ~PrimeTable() {} 45 46 // Returns true if and only if 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: IsPrime(int n)57 bool IsPrime(int n) const override { 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 GetNextPrime(int p)68 int GetNextPrime(int p) const override { 69 if (p < 0) return -1; 70 71 for (int n = p + 1;; n++) { 72 if (IsPrime(n)) return n; 73 } 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. PreCalculatedPrimeTable(int max)82 explicit PreCalculatedPrimeTable(int max) 83 : is_prime_size_(max + 1), is_prime_(new bool[max + 1]) { 84 CalculatePrimesUpTo(max); 85 } ~PreCalculatedPrimeTable()86 ~PreCalculatedPrimeTable() override { delete[] is_prime_; } 87 IsPrime(int n)88 bool IsPrime(int n) const override { 89 return 0 <= n && n < is_prime_size_ && is_prime_[n]; 90 } 91 GetNextPrime(int p)92 int GetNextPrime(int p) const override { 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: CalculatePrimesUpTo(int max)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 // GOOGLETEST_SAMPLES_PRIME_TABLES_H_ 127