michael@0: // Copyright 2008 Google Inc.
michael@0: // All Rights Reserved.
michael@0: //
michael@0: // Redistribution and use in source and binary forms, with or without
michael@0: // modification, are permitted provided that the following conditions are
michael@0: // met:
michael@0: //
michael@0: //     * Redistributions of source code must retain the above copyright
michael@0: // notice, this list of conditions and the following disclaimer.
michael@0: //     * Redistributions in binary form must reproduce the above
michael@0: // copyright notice, this list of conditions and the following disclaimer
michael@0: // in the documentation and/or other materials provided with the
michael@0: // distribution.
michael@0: //     * Neither the name of Google Inc. nor the names of its
michael@0: // contributors may be used to endorse or promote products derived from
michael@0: // this software without specific prior written permission.
michael@0: //
michael@0: // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0: // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0: // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
michael@0: // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
michael@0: // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
michael@0: // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
michael@0: // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
michael@0: // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
michael@0: // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
michael@0: // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
michael@0: // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0: //
michael@0: // Author: wan@google.com (Zhanyong Wan)
michael@0: // Author: vladl@google.com (Vlad Losev)
michael@0: 
michael@0: // This provides interface PrimeTable that determines whether a number is a
michael@0: // prime and determines a next prime number. This interface is used
michael@0: // in Google Test samples demonstrating use of parameterized tests.
michael@0: 
michael@0: #ifndef GTEST_SAMPLES_PRIME_TABLES_H_
michael@0: #define GTEST_SAMPLES_PRIME_TABLES_H_
michael@0: 
michael@0: #include <algorithm>
michael@0: 
michael@0: // The prime table interface.
michael@0: class PrimeTable {
michael@0:  public:
michael@0:   virtual ~PrimeTable() {}
michael@0: 
michael@0:   // Returns true iff n is a prime number.
michael@0:   virtual bool IsPrime(int n) const = 0;
michael@0: 
michael@0:   // Returns the smallest prime number greater than p; or returns -1
michael@0:   // if the next prime is beyond the capacity of the table.
michael@0:   virtual int GetNextPrime(int p) const = 0;
michael@0: };
michael@0: 
michael@0: // Implementation #1 calculates the primes on-the-fly.
michael@0: class OnTheFlyPrimeTable : public PrimeTable {
michael@0:  public:
michael@0:   virtual bool IsPrime(int n) const {
michael@0:     if (n <= 1) return false;
michael@0: 
michael@0:     for (int i = 2; i*i <= n; i++) {
michael@0:       // n is divisible by an integer other than 1 and itself.
michael@0:       if ((n % i) == 0) return false;
michael@0:     }
michael@0: 
michael@0:     return true;
michael@0:   }
michael@0: 
michael@0:   virtual int GetNextPrime(int p) const {
michael@0:     for (int n = p + 1; n > 0; n++) {
michael@0:       if (IsPrime(n)) return n;
michael@0:     }
michael@0: 
michael@0:     return -1;
michael@0:   }
michael@0: };
michael@0: 
michael@0: // Implementation #2 pre-calculates the primes and stores the result
michael@0: // in an array.
michael@0: class PreCalculatedPrimeTable : public PrimeTable {
michael@0:  public:
michael@0:   // 'max' specifies the maximum number the prime table holds.
michael@0:   explicit PreCalculatedPrimeTable(int max)
michael@0:       : is_prime_size_(max + 1), is_prime_(new bool[max + 1]) {
michael@0:     CalculatePrimesUpTo(max);
michael@0:   }
michael@0:   virtual ~PreCalculatedPrimeTable() { delete[] is_prime_; }
michael@0: 
michael@0:   virtual bool IsPrime(int n) const {
michael@0:     return 0 <= n && n < is_prime_size_ && is_prime_[n];
michael@0:   }
michael@0: 
michael@0:   virtual int GetNextPrime(int p) const {
michael@0:     for (int n = p + 1; n < is_prime_size_; n++) {
michael@0:       if (is_prime_[n]) return n;
michael@0:     }
michael@0: 
michael@0:     return -1;
michael@0:   }
michael@0: 
michael@0:  private:
michael@0:   void CalculatePrimesUpTo(int max) {
michael@0:     ::std::fill(is_prime_, is_prime_ + is_prime_size_, true);
michael@0:     is_prime_[0] = is_prime_[1] = false;
michael@0: 
michael@0:     for (int i = 2; i <= max; i++) {
michael@0:       if (!is_prime_[i]) continue;
michael@0: 
michael@0:       // Marks all multiples of i (except i itself) as non-prime.
michael@0:       for (int j = 2*i; j <= max; j += i) {
michael@0:         is_prime_[j] = false;
michael@0:       }
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   const int is_prime_size_;
michael@0:   bool* const is_prime_;
michael@0: 
michael@0:   // Disables compiler warning "assignment operator could not be generated."
michael@0:   void operator=(const PreCalculatedPrimeTable& rhs);
michael@0: };
michael@0: 
michael@0: #endif  // GTEST_SAMPLES_PRIME_TABLES_H_