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prime_tables.h
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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.
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.
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.
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 // Checks every candidate for prime number (we know that 2 is the only even
107 // prime).
108 for (int i = 2; i*i <= max; i += i%2+1) {
109 if (!is_prime_[i]) continue;
110
111 // Marks all multiples of i (except i itself) as non-prime.
112 // We are starting here from i-th multiplier, because all smaller
113 // complex numbers were already marked.
114 for (int j = i*i; j <= max; j += i) {
115 is_prime_[j] = false;
116 }
117 }
118 }
119
120 const int is_prime_size_;
121 bool* const is_prime_;
122
123 // Disables compiler warning "assignment operator could not be generated."
124 void operator=(const PreCalculatedPrimeTable& rhs);
125};
126
127#endif // GTEST_SAMPLES_PRIME_TABLES_H_
const mie::Vuint & p
Definition bn.cpp:27
virtual bool IsPrime(int n) const
virtual int GetNextPrime(int p) const
virtual int GetNextPrime(int p) const
virtual ~PreCalculatedPrimeTable()
virtual bool IsPrime(int n) const
virtual bool IsPrime(int n) const =0
virtual int GetNextPrime(int p) const =0
virtual ~PrimeTable()
uint16_t j