cborutil: add a buffering decoder
The sansiodecoder leaves it up to the callers to feed in data that
wasn't fully consumed last time.
This commit implements a decoder that performs buffering of
leftover chunks from the previous invocation. It otherwise
behaves identically to sansiodecoder.
Differential Revision: https://phab.mercurial-scm.org/D4434
#include "fuzzutil.h"
#include <cstring>
#include <utility>
contrib::optional<two_inputs> SplitInputs(const uint8_t *Data, size_t Size)
{
if (!Size) {
return contrib::nullopt;
}
// figure out a random point in [0, Size] to split our input.
size_t left_size = (Data[0] / 255.0) * (Size - 1);
// Copy inputs to new allocations so if bdiff over-reads
// AddressSanitizer can detect it.
std::unique_ptr<char[]> left(new char[left_size]);
std::memcpy(left.get(), Data + 1, left_size);
// right starts at the next byte after left ends
size_t right_size = Size - (left_size + 1);
std::unique_ptr<char[]> right(new char[right_size]);
std::memcpy(right.get(), Data + 1 + left_size, right_size);
LOG(2) << "inputs are " << left_size << " and " << right_size
<< " bytes" << std::endl;
two_inputs result = {std::move(right), right_size, std::move(left),
left_size};
return result;
}