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/*
* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef TEST_FUZZERS_FUZZ_DATA_HELPER_H_
#define TEST_FUZZERS_FUZZ_DATA_HELPER_H_
#include <limits>
#include "api/array_view.h"
#include "modules/rtp_rtcp/source/byte_io.h"
namespace webrtc {
namespace test {
// Helper class to take care of the fuzzer input, read from it, and keep track
// of when the end of the data has been reached.
class FuzzDataHelper {
public:
explicit FuzzDataHelper(rtc::ArrayView<const uint8_t> data);
// Returns true if n bytes can be read.
bool CanReadBytes(size_t n) const { return data_ix_ + n <= data_.size(); }
// Reads and returns data of type T.
template <typename T>
T Read() {
RTC_CHECK(CanReadBytes(sizeof(T)));
T x = ByteReader<T>::ReadLittleEndian(&data_[data_ix_]);
data_ix_ += sizeof(T);
return x;
}
// Reads and returns data of type T. Returns default_value if not enough
// fuzzer input remains to read a T.
template <typename T>
T ReadOrDefaultValue(T default_value) {
if (!CanReadBytes(sizeof(T))) {
return default_value;
}
return Read<T>();
}
// Like ReadOrDefaultValue, but replaces the value 0 with default_value.
template <typename T>
T ReadOrDefaultValueNotZero(T default_value) {
static_assert(std::is_integral<T>::value, "");
T x = ReadOrDefaultValue(default_value);
return x == 0 ? default_value : x;
}
// Returns one of the elements from the provided input array. The selection
// is based on the fuzzer input data. If not enough fuzzer data is available,
// the method will return the first element in the input array. The reason for
// not flagging this as an error is to allow the method to be called from
// class constructors, and in constructors we typically do not handle
// errors. The code will work anyway, and the fuzzer will likely see that
// providing more data will actually make this method return something else.
template <typename T, size_t N>
T SelectOneOf(const T (&select_from)[N]) {
static_assert(N <= std::numeric_limits<uint8_t>::max(), "");
// Read an index between 0 and select_from.size() - 1 from the fuzzer data.
uint8_t index = ReadOrDefaultValue<uint8_t>(0) % N;
return select_from[index];
}
rtc::ArrayView<const uint8_t> ReadByteArray(size_t bytes) {
if (!CanReadBytes(bytes)) {
return rtc::ArrayView<const uint8_t>(nullptr, 0);
}
const size_t index_to_return = data_ix_;
data_ix_ += bytes;
return data_.subview(index_to_return, bytes);
}
// If sizeof(T) > BytesLeft then the remaining bytes will be used and the rest
// of the object will be zero initialized.
template <typename T>
void CopyTo(T* object) {
memset(object, 0, sizeof(T));
size_t bytes_to_copy = std::min(BytesLeft(), sizeof(T));
memcpy(object, data_.data() + data_ix_, bytes_to_copy);
data_ix_ += bytes_to_copy;
}
size_t BytesRead() const { return data_ix_; }
size_t BytesLeft() const { return data_.size() - data_ix_; }
private:
rtc::ArrayView<const uint8_t> data_;
size_t data_ix_ = 0;
};
} // namespace test
} // namespace webrtc
#endif // TEST_FUZZERS_FUZZ_DATA_HELPER_H_
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