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