114 lines
3.9 KiB
C++
114 lines
3.9 KiB
C++
// Copyright 2021 The Tint Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef FUZZERS_RANDOM_GENERATOR_H_
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#define FUZZERS_RANDOM_GENERATOR_H_
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#include <random>
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#include <vector>
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namespace tint {
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namespace fuzzers {
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/// Pseudo random generator utility class for fuzzing
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class RandomGenerator {
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public:
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/// @brief Initializes the internal engine
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/// @param seed - seed value passed to engine
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explicit RandomGenerator(uint64_t seed);
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/// @brief Wrapper that invokes CalculateSeed for caller
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/// @param data - data fuzzer to calculate seed from
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/// @param size - size of data buffer
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explicit RandomGenerator(const uint8_t* data, size_t size);
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~RandomGenerator() = default;
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RandomGenerator(RandomGenerator&&) = default;
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/// Get uint32_t value from uniform distribution.
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/// @param lower - lower bound of integer generated
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/// @param upper - upper bound of integer generated
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/// @returns i, where lower <= i < upper
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uint32_t GetUInt32(uint32_t lower, uint32_t upper);
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/// Get uint32_t value from uniform distribution.
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/// @param bound - Upper bound of integer generated
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/// @returns i, where 0 <= i < bound
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uint32_t GetUInt32(uint32_t bound);
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/// Get uint32_t value from uniform distribution.
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/// @param lower - lower bound of integer generated
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/// @param upper - upper bound of integer generated
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/// @returns i, where lower <= i < upper
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uint64_t GetUInt64(uint64_t lower, uint64_t upper);
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/// Get uint64_t value from uniform distribution.
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/// @param bound - Upper bound of integer generated
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/// @returns i, where 0 <= i < bound
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uint64_t GetUInt64(uint64_t bound);
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/// Get 1 byte of pseudo-random data
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/// Should be more efficient then calling GetNBytes(1);
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/// @returns 1-byte of random data
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uint8_t GetByte();
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/// Get 4 bytes of pseudo-random data
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/// Should be more efficient then calling GetNBytes(4);
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/// @returns 4-bytes of random data
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uint32_t Get4Bytes();
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/// Get N bytes of pseudo-random data
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/// @param dest - memory location to store data
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/// @param n - number of bytes of data to generate
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void GetNBytes(uint8_t* dest, size_t n);
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/// Get random bool with even odds
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/// @returns true 50% of the time and false %50 of time.
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bool GetBool();
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/// Get random bool with weighted odds
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/// @param percentage - likelihood of true being returned
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/// @returns true |percentage|% of the time, and false (100 - |percentage|)%
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/// of the time.
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bool GetWeightedBool(uint32_t percentage);
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/// Calculate a seed value based on a blob of data.
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/// Currently hashes bytes near the front of the buffer, after skipping N
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/// bytes.
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/// @param data - pointer to data to base calculation off of, must be !nullptr
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/// @param size - number of elements in |data|, must be > 0
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static uint64_t CalculateSeed(const uint8_t* data, size_t size);
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/// Returns a randomly-chosen element from vector v.
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/// @param v - the vector from which the random element will be selected.
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/// @return a random element of vector v.
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template <typename T>
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inline T GetRandomElement(const std::vector<T>& v) {
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return v[GetUInt64(0, v.size() - 1)];
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}
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private:
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std::mt19937_64 engine_;
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// Disallow copy & assign
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RandomGenerator(const RandomGenerator&) = delete;
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RandomGenerator& operator=(const RandomGenerator&) = delete;
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}; // class RandomGenerator
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} // namespace fuzzers
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} // namespace tint
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#endif // FUZZERS_RANDOM_GENERATOR_H_
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