github.com/jlmucb/cloudproxy@v0.0.0-20170830161738-b5aa0b619bc4/src/third_party/googlemock/gtest/samples/prime_tables.h (about)

     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:
    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:
    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  
    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.
    83    explicit PreCalculatedPrimeTable(int max)
    84        : is_prime_size_(max + 1), is_prime_(new bool[max + 1]) {
    85      CalculatePrimesUpTo(max);
    86    }
    87    virtual ~PreCalculatedPrimeTable() { delete[] is_prime_; }
    88  
    89    virtual bool IsPrime(int n) const {
    90      return 0 <= n && n < is_prime_size_ && is_prime_[n];
    91    }
    92  
    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:
   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_