lib/overnet/datagram_stream/linearizer_fuzzer_helpers.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <vector>
#include "garnet/lib/overnet/vocabulary/optional.h"
#include "linearizer.h"

namespace overnet {
namespace linearizer_fuzzer {

// Main fuzzer logic... to be used in the fuzzer itself, and in unit tests
class LinearizerFuzzer {
 public:
  static const uint64_t kBuffer = 1024;

  ~LinearizerFuzzer() { SetClosed(StatusCode::CANCELLED); }

  void Close(uint8_t status_code) {
    SetClosed(static_cast<StatusCode>(status_code));
    linearizer_.Close(static_cast<StatusCode>(status_code));
  }

  void Push(uint16_t offset, uint8_t length, bool end_of_message,
            const uint8_t* data) {
    uint64_t last_byte = static_cast<uint64_t>(offset) + length;
    const bool resource_exhausted = last_byte > offset_ + kBuffer;
    if (!resource_exhausted) {
      if (length_) {
        if (last_byte > *length_) {
          SetClosed(StatusCode::INVALID_ARGUMENT);
        } else if (end_of_message && *length_ != last_byte) {
          SetClosed(StatusCode::INVALID_ARGUMENT);
        }
      } else if (end_of_message) {
        if (offset_ > last_byte)
          SetClosed(StatusCode::INVALID_ARGUMENT);
        for (unsigned i = last_byte; i < sizeof(bytes_) / sizeof(*bytes_);
             i++) {
          if (bytes_[i].present)
            SetClosed(StatusCode::INVALID_ARGUMENT);
        }
        if (offset_ == last_byte)
          SetClosed(StatusCode::OK);
        length_ = last_byte;
      }
      for (unsigned i = 0; i < length; i++) {
        unsigned idx = i + offset;
        ByteState& st = bytes_[idx];
        if (st.present) {
          if (st.byte != data[i] && idx >= offset_) {
            SetClosed(StatusCode::DATA_LOSS);
          }
        } else {
          st.byte = data[i];
          st.present = true;
        }
      }
    }
    auto ignore = [](bool) {};
    ignore(linearizer_.Push(
        Chunk{offset, end_of_message, Slice::FromCopiedBuffer(data, length)}));
  }

  void Pull() {
    if (waiting_for_pull_)
      return;
    waiting_for_pull_ = true;
    linearizer_.Pull(StatusOrCallback<Optional<Slice>>(
        [this](const StatusOr<Optional<Slice>>& status) {
          assert(waiting_for_pull_);
          waiting_for_pull_ = false;
#ifndef NDEBUG
          if (is_closed_) {
            assert(status.code() == closed_status_);
          } else {
            assert(status.is_ok());
            if (*status) {
              for (auto b : **status) {
                ByteState st = bytes_[offset_++];
                assert(st.present);
                assert(b == st.byte);
              }
            }
            if (length_ && *length_ == offset_) {
              SetClosed(StatusCode::OK);
            }
          }
#endif
        }));
  }

 private:
  void SetClosed(StatusCode status_code) {
    if (!is_closed_) {
      is_closed_ = true;
      closed_status_ = status_code;
    }
  }

  struct ByteState {
    bool present = false;
    uint8_t byte = 0;
  };
  uint64_t offset_ = 0;
  Optional<uint64_t> length_;
  ByteState bytes_[(1 << 16) + (1 << 8)];
  bool is_closed_ = false;
  StatusCode closed_status_;
  bool waiting_for_pull_ = false;

  Linearizer linearizer_{kBuffer};
};

}  // namespace linearizer_fuzzer
}  // namespace overnet