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authorLexi Winter <lexi@le-fay.org>2025-06-29 19:25:29 +0100
committerLexi Winter <lexi@le-fay.org>2025-06-29 19:25:29 +0100
commitbc524d70253a4ab2fe40c3ca3e5666e267c0a4d1 (patch)
tree1e629e7b46b1d9972a973bc93fd100bcebd395be /src/catch2/internal/catch_random_number_generator.hpp
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Diffstat (limited to 'src/catch2/internal/catch_random_number_generator.hpp')
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diff --git a/src/catch2/internal/catch_random_number_generator.hpp b/src/catch2/internal/catch_random_number_generator.hpp
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+
+// Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE.txt or copy at
+// https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+#ifndef CATCH_RANDOM_NUMBER_GENERATOR_HPP_INCLUDED
+#define CATCH_RANDOM_NUMBER_GENERATOR_HPP_INCLUDED
+
+#include <cstdint>
+
+namespace Catch {
+
+ // This is a simple implementation of C++11 Uniform Random Number
+ // Generator. It does not provide all operators, because Catch2
+ // does not use it, but it should behave as expected inside stdlib's
+ // distributions.
+ // The implementation is based on the PCG family (http://pcg-random.org)
+ class SimplePcg32 {
+ using state_type = std::uint64_t;
+ public:
+ using result_type = std::uint32_t;
+ static constexpr result_type (min)() {
+ return 0;
+ }
+ static constexpr result_type (max)() {
+ return static_cast<result_type>(-1);
+ }
+
+ // Provide some default initial state for the default constructor
+ SimplePcg32():SimplePcg32(0xed743cc4U) {}
+
+ explicit SimplePcg32(result_type seed_);
+
+ void seed(result_type seed_);
+ void discard(uint64_t skip);
+
+ result_type operator()();
+
+ private:
+ friend bool operator==(SimplePcg32 const& lhs, SimplePcg32 const& rhs);
+ friend bool operator!=(SimplePcg32 const& lhs, SimplePcg32 const& rhs);
+
+ // In theory we also need operator<< and operator>>
+ // In practice we do not use them, so we will skip them for now
+
+
+ std::uint64_t m_state;
+ // This part of the state determines which "stream" of the numbers
+ // is chosen -- we take it as a constant for Catch2, so we only
+ // need to deal with seeding the main state.
+ // Picked by reading 8 bytes from `/dev/random` :-)
+ static const std::uint64_t s_inc = (0x13ed0cc53f939476ULL << 1ULL) | 1ULL;
+ };
+
+} // end namespace Catch
+
+#endif // CATCH_RANDOM_NUMBER_GENERATOR_HPP_INCLUDED