payload_consumer/extent_writer.h

//
// Copyright (C) 2009 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#ifndef UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_
#define UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_

#include <memory>
#include <utility>

#include <base/logging.h>
#include <brillo/secure_blob.h>

#include "update_engine/payload_consumer/file_descriptor.h"
#include "update_engine/update_metadata.pb.h"

// ExtentWriter is an abstract class which synchronously writes to a given
// file descriptor at the extents given.

namespace chromeos_update_engine {

class ExtentWriter {
 public:
  ExtentWriter() = default;
  virtual ~ExtentWriter() = default;

  // Returns true on success.
  virtual bool Init(const google::protobuf::RepeatedPtrField<Extent>& extents,
                    uint32_t block_size) = 0;

  // Returns true on success.
  virtual bool Write(const void* bytes, size_t count) = 0;
};

// DirectExtentWriter is probably the simplest ExtentWriter implementation.
// It writes the data directly into the extents.

class DirectExtentWriter : public ExtentWriter {
 public:
  explicit DirectExtentWriter(FileDescriptorPtr fd) : fd_(fd) {}
  ~DirectExtentWriter() override = default;

  bool Init(const google::protobuf::RepeatedPtrField<Extent>& extents,
            uint32_t block_size) override {
    block_size_ = block_size;
    extents_ = extents;
    cur_extent_ = extents_.begin();
    return true;
  }
  bool Write(const void* bytes, size_t count) override;

 private:
  FileDescriptorPtr fd_{nullptr};

  size_t block_size_{0};
  // Bytes written into |cur_extent_| thus far.
  uint64_t extent_bytes_written_{0};
  google::protobuf::RepeatedPtrField<Extent> extents_;
  // The next call to write should correspond to |cur_extents_|.
  google::protobuf::RepeatedPtrField<Extent>::iterator cur_extent_;
};

}  // namespace chromeos_update_engine

#endif  // UPDATE_ENGINE_PAYLOAD_CONSUMER_EXTENT_WRITER_H_