Mercurial > hg
view contrib/fuzz/FuzzedDataProvider.h @ 48393:1a8a70b4b0ad
dirstate: cleanup remaining of "now" during write
Since the whole `need_delay` have been removed, we no longer need this.
Differential Revision: https://phab.mercurial-scm.org/D11797
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
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date | Fri, 19 Nov 2021 03:03:01 +0100 |
parents | 5a9e2ae9899b |
children |
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//===- FuzzedDataProvider.h - Utility header for fuzz targets ---*- C++ -* ===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // A single header library providing an utility class to break up an array of // bytes. Whenever run on the same input, provides the same output, as long as // its methods are called in the same order, with the same arguments. //===----------------------------------------------------------------------===// #ifndef LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_ #define LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_ #include <algorithm> #include <climits> #include <cstddef> #include <cstdint> #include <cstring> #include <initializer_list> #include <string> #include <type_traits> #include <utility> #include <vector> // In addition to the comments below, the API is also briefly documented at // https://github.com/google/fuzzing/blob/master/docs/split-inputs.md#fuzzed-data-provider class FuzzedDataProvider { public: // |data| is an array of length |size| that the FuzzedDataProvider wraps // to provide more granular access. |data| must outlive the // FuzzedDataProvider. FuzzedDataProvider(const uint8_t *data, size_t size) : data_ptr_(data), remaining_bytes_(size) { } ~FuzzedDataProvider() = default; // Returns a std::vector containing |num_bytes| of input data. If fewer // than |num_bytes| of data remain, returns a shorter std::vector // containing all of the data that's left. Can be used with any byte // sized type, such as char, unsigned char, uint8_t, etc. template <typename T> std::vector<T> ConsumeBytes(size_t num_bytes) { num_bytes = std::min(num_bytes, remaining_bytes_); return ConsumeBytes<T>(num_bytes, num_bytes); } // Similar to |ConsumeBytes|, but also appends the terminator value at // the end of the resulting vector. Useful, when a mutable // null-terminated C-string is needed, for example. But that is a rare // case. Better avoid it, if possible, and prefer using |ConsumeBytes| // or |ConsumeBytesAsString| methods. template <typename T> std::vector<T> ConsumeBytesWithTerminator(size_t num_bytes, T terminator = 0) { num_bytes = std::min(num_bytes, remaining_bytes_); std::vector<T> result = ConsumeBytes<T>(num_bytes + 1, num_bytes); result.back() = terminator; return result; } // Returns a std::string containing |num_bytes| of input data. Using // this and // |.c_str()| on the resulting string is the best way to get an // immutable null-terminated C string. If fewer than |num_bytes| of data // remain, returns a shorter std::string containing all of the data // that's left. std::string ConsumeBytesAsString(size_t num_bytes) { static_assert(sizeof(std::string::value_type) == sizeof(uint8_t), "ConsumeBytesAsString cannot convert the data to " "a string."); num_bytes = std::min(num_bytes, remaining_bytes_); std::string result( reinterpret_cast<const std::string::value_type *>( data_ptr_), num_bytes); Advance(num_bytes); return result; } // Returns a number in the range [min, max] by consuming bytes from the // input data. The value might not be uniformly distributed in the given // range. If there's no input data left, always returns |min|. |min| // must be less than or equal to |max|. template <typename T> T ConsumeIntegralInRange(T min, T max) { static_assert(std::is_integral<T>::value, "An integral type is required."); static_assert(sizeof(T) <= sizeof(uint64_t), "Unsupported integral type."); if (min > max) abort(); // Use the biggest type possible to hold the range and the // result. uint64_t range = static_cast<uint64_t>(max) - min; uint64_t result = 0; size_t offset = 0; while (offset < sizeof(T) * CHAR_BIT && (range >> offset) > 0 && remaining_bytes_ != 0) { // Pull bytes off the end of the seed data. // Experimentally, this seems to allow the fuzzer to // more easily explore the input space. This makes // sense, since it works by modifying inputs that caused // new code to run, and this data is often used to // encode length of data read by |ConsumeBytes|. // Separating out read lengths makes it easier modify // the contents of the data that is actually read. --remaining_bytes_; result = (result << CHAR_BIT) | data_ptr_[remaining_bytes_]; offset += CHAR_BIT; } // Avoid division by 0, in case |range + 1| results in overflow. if (range != std::numeric_limits<decltype(range)>::max()) result = result % (range + 1); return static_cast<T>(min + result); } // Returns a std::string of length from 0 to |max_length|. When it runs // out of input data, returns what remains of the input. Designed to be // more stable with respect to a fuzzer inserting characters than just // picking a random length and then consuming that many bytes with // |ConsumeBytes|. std::string ConsumeRandomLengthString(size_t max_length) { // Reads bytes from the start of |data_ptr_|. Maps "\\" to "\", // and maps "\" followed by anything else to the end of the // string. As a result of this logic, a fuzzer can insert // characters into the string, and the string will be lengthened // to include those new characters, resulting in a more stable // fuzzer than picking the length of a string independently from // picking its contents. std::string result; // Reserve the anticipated capaticity to prevent several // reallocations. result.reserve(std::min(max_length, remaining_bytes_)); for (size_t i = 0; i < max_length && remaining_bytes_ != 0; ++i) { char next = ConvertUnsignedToSigned<char>(data_ptr_[0]); Advance(1); if (next == '\\' && remaining_bytes_ != 0) { next = ConvertUnsignedToSigned<char>(data_ptr_[0]); Advance(1); if (next != '\\') break; } result += next; } result.shrink_to_fit(); return result; } // Returns a std::vector containing all remaining bytes of the input // data. template <typename T> std::vector<T> ConsumeRemainingBytes() { return ConsumeBytes<T>(remaining_bytes_); } // Returns a std::string containing all remaining bytes of the input // data. Prefer using |ConsumeRemainingBytes| unless you actually need a // std::string object. std::string ConsumeRemainingBytesAsString() { return ConsumeBytesAsString(remaining_bytes_); } // Returns a number in the range [Type's min, Type's max]. The value // might not be uniformly distributed in the given range. If there's no // input data left, always returns |min|. template <typename T> T ConsumeIntegral() { return ConsumeIntegralInRange(std::numeric_limits<T>::min(), std::numeric_limits<T>::max()); } // Reads one byte and returns a bool, or false when no data remains. bool ConsumeBool() { return 1 & ConsumeIntegral<uint8_t>(); } // Returns a copy of the value selected from the given fixed-size // |array|. template <typename T, size_t size> T PickValueInArray(const T (&array)[size]) { static_assert(size > 0, "The array must be non empty."); return array[ConsumeIntegralInRange<size_t>(0, size - 1)]; } template <typename T> T PickValueInArray(std::initializer_list<const T> list) { // TODO(Dor1s): switch to static_assert once C++14 is allowed. if (!list.size()) abort(); return *(list.begin() + ConsumeIntegralInRange<size_t>(0, list.size() - 1)); } // Returns an enum value. The enum must start at 0 and be contiguous. It // must also contain |kMaxValue| aliased to its largest (inclusive) // value. Such as: enum class Foo { SomeValue, OtherValue, kMaxValue = // OtherValue }; template <typename T> T ConsumeEnum() { static_assert(std::is_enum<T>::value, "|T| must be an enum type."); return static_cast<T>(ConsumeIntegralInRange<uint32_t>( 0, static_cast<uint32_t>(T::kMaxValue))); } // Returns a floating point number in the range [0.0, 1.0]. If there's // no input data left, always returns 0. template <typename T> T ConsumeProbability() { static_assert(std::is_floating_point<T>::value, "A floating point type is required."); // Use different integral types for different floating point // types in order to provide better density of the resulting // values. using IntegralType = typename std::conditional<(sizeof(T) <= sizeof(uint32_t)), uint32_t, uint64_t>::type; T result = static_cast<T>(ConsumeIntegral<IntegralType>()); result /= static_cast<T>(std::numeric_limits<IntegralType>::max()); return result; } // Returns a floating point value in the range [Type's lowest, Type's // max] by consuming bytes from the input data. If there's no input data // left, always returns approximately 0. template <typename T> T ConsumeFloatingPoint() { return ConsumeFloatingPointInRange<T>( std::numeric_limits<T>::lowest(), std::numeric_limits<T>::max()); } // Returns a floating point value in the given range by consuming bytes // from the input data. If there's no input data left, returns |min|. // Note that |min| must be less than or equal to |max|. template <typename T> T ConsumeFloatingPointInRange(T min, T max) { if (min > max) abort(); T range = .0; T result = min; constexpr T zero(.0); if (max > zero && min < zero && max > min + std::numeric_limits<T>::max()) { // The diff |max - min| would overflow the given // floating point type. Use the half of the diff as the // range and consume a bool to decide whether the result // is in the first of the second part of the diff. range = (max / 2.0) - (min / 2.0); if (ConsumeBool()) { result += range; } } else { range = max - min; } return result + range * ConsumeProbability<T>(); } // Reports the remaining bytes available for fuzzed input. size_t remaining_bytes() { return remaining_bytes_; } private: FuzzedDataProvider(const FuzzedDataProvider &) = delete; FuzzedDataProvider &operator=(const FuzzedDataProvider &) = delete; void Advance(size_t num_bytes) { if (num_bytes > remaining_bytes_) abort(); data_ptr_ += num_bytes; remaining_bytes_ -= num_bytes; } template <typename T> std::vector<T> ConsumeBytes(size_t size, size_t num_bytes_to_consume) { static_assert(sizeof(T) == sizeof(uint8_t), "Incompatible data type."); // The point of using the size-based constructor below is to // increase the odds of having a vector object with capacity // being equal to the length. That part is always implementation // specific, but at least both libc++ and libstdc++ allocate the // requested number of bytes in that constructor, which seems to // be a natural choice for other implementations as well. To // increase the odds even more, we also call |shrink_to_fit| // below. std::vector<T> result(size); if (size == 0) { if (num_bytes_to_consume != 0) abort(); return result; } std::memcpy(result.data(), data_ptr_, num_bytes_to_consume); Advance(num_bytes_to_consume); // Even though |shrink_to_fit| is also implementation specific, // we expect it to provide an additional assurance in case // vector's constructor allocated a buffer which is larger than // the actual amount of data we put inside it. result.shrink_to_fit(); return result; } template <typename TS, typename TU> TS ConvertUnsignedToSigned(TU value) { static_assert(sizeof(TS) == sizeof(TU), "Incompatible data types."); static_assert(!std::numeric_limits<TU>::is_signed, "Source type must be unsigned."); // TODO(Dor1s): change to `if constexpr` once C++17 becomes // mainstream. if (std::numeric_limits<TS>::is_modulo) return static_cast<TS>(value); // Avoid using implementation-defined unsigned to signer // conversions. To learn more, see // https://stackoverflow.com/questions/13150449. if (value <= std::numeric_limits<TS>::max()) { return static_cast<TS>(value); } else { constexpr auto TS_min = std::numeric_limits<TS>::min(); return TS_min + static_cast<char>(value - TS_min); } } const uint8_t *data_ptr_; size_t remaining_bytes_; }; #endif // LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_ // no-check-code since this is from a third party