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 // Author: wan@google.com (Zhanyong Wan) 31 // Author: vladl@google.com (Vlad Losev) 32 33 // This provides interface PrimeTable that determines whether a number is a 34 // prime and determines a next prime number. This interface is used 35 // in Google Test samples demonstrating use of parameterized tests. 36 37 #ifndef GTEST_SAMPLES_PRIME_TABLES_H_ 38 #define GTEST_SAMPLES_PRIME_TABLES_H_ 39 40 #include <algorithm> 41 42 // The prime table interface. 43 class PrimeTable { 44 public: ~PrimeTable()45 virtual ~PrimeTable() {} 46 47 // Returns true iff n is a prime number. 48 virtual bool IsPrime(int n) const = 0; 49 50 // Returns the smallest prime number greater than p; or returns -1 51 // if the next prime is beyond the capacity of the table. 52 virtual int GetNextPrime(int p) const = 0; 53 }; 54 55 // Implementation #1 calculates the primes on-the-fly. 56 class OnTheFlyPrimeTable : public PrimeTable { 57 public: IsPrime(int n)58 virtual bool IsPrime(int n) const { 59 if (n <= 1) return false; 60 61 for (int i = 2; i*i <= n; i++) { 62 // n is divisible by an integer other than 1 and itself. 63 if ((n % i) == 0) return false; 64 } 65 66 return true; 67 } 68 GetNextPrime(int p)69 virtual int GetNextPrime(int p) const { 70 for (int n = p + 1; n > 0; n++) { 71 if (IsPrime(n)) return n; 72 } 73 74 return -1; 75 } 76 }; 77 78 // Implementation #2 pre-calculates the primes and stores the result 79 // in an array. 80 class PreCalculatedPrimeTable : public PrimeTable { 81 public: 82 // 'max' specifies the maximum number the prime table holds. PreCalculatedPrimeTable(int max)83 explicit PreCalculatedPrimeTable(int max) 84 : is_prime_size_(max + 1), is_prime_(new bool[max + 1]) { 85 CalculatePrimesUpTo(max); 86 } ~PreCalculatedPrimeTable()87 virtual ~PreCalculatedPrimeTable() { delete[] is_prime_; } 88 IsPrime(int n)89 virtual bool IsPrime(int n) const { 90 return 0 <= n && n < is_prime_size_ && is_prime_[n]; 91 } 92 GetNextPrime(int p)93 virtual int GetNextPrime(int p) const { 94 for (int n = p + 1; n < is_prime_size_; n++) { 95 if (is_prime_[n]) return n; 96 } 97 98 return -1; 99 } 100 101 private: CalculatePrimesUpTo(int max)102 void CalculatePrimesUpTo(int max) { 103 ::std::fill(is_prime_, is_prime_ + is_prime_size_, true); 104 is_prime_[0] = is_prime_[1] = false; 105 106 for (int i = 2; i <= max; i++) { 107 if (!is_prime_[i]) continue; 108 109 // Marks all multiples of i (except i itself) as non-prime. 110 for (int j = 2*i; j <= max; j += i) { 111 is_prime_[j] = false; 112 } 113 } 114 } 115 116 const int is_prime_size_; 117 bool* const is_prime_; 118 119 // Disables compiler warning "assignment operator could not be generated." 120 void operator=(const PreCalculatedPrimeTable& rhs); 121 }; 122 123 #endif // GTEST_SAMPLES_PRIME_TABLES_H_ 124