libcryfs/src/blobstore/implementations/onblocks/datanodestore/DataNodeView.h

#pragma once
#ifndef MESSMER_BLOBSTORE_IMPLEMENTATIONS_ONBLOCKS_DATANODESTORE_DATANODEVIEW_H_
#define MESSMER_BLOBSTORE_IMPLEMENTATIONS_ONBLOCKS_DATANODESTORE_DATANODEVIEW_H_

#include <blockstore/interface/Block.h>
#include "../BlobStoreOnBlocks.h"
#include "DataInnerNode_ChildEntry.h"

#include <cpp-utils/pointer/unique_ref.h>

#include <memory>
#include <stdexcept>
#include <type_traits>

namespace blobstore {
namespace onblocks {
namespace datanodestore {

//TODO Move DataNodeLayout into own file
class DataNodeLayout final {
public:
  constexpr DataNodeLayout(uint64_t blocksizeBytes)
    :_blocksizeBytes(
        (HEADERSIZE_BYTES + 2*sizeof(DataInnerNode_ChildEntry) <= blocksizeBytes)
        ? blocksizeBytes
        : throw std::logic_error("Blocksize too small, not enough space to store two children in an inner node")) {
  }

  //Total size of the header
  static constexpr uint32_t HEADERSIZE_BYTES = 8;
  //Where in the header is the format version field (used to allow compatibility with future versions of CryFS)
  static constexpr uint32_t FORMAT_VERSION_OFFSET_BYTES = 0; //format version uses 2 bytes
  //Where in the header is the depth field
  static constexpr uint32_t DEPTH_OFFSET_BYTES = 3; // depth uses 1 byte
  //Where in the header is the size field (for inner nodes: number of children, for leafs: content data size)
  static constexpr uint32_t SIZE_OFFSET_BYTES = 4; // size uses 4 bytes


  //Size of a block (header + data region)
  constexpr uint64_t blocksizeBytes() const {
    return _blocksizeBytes;
  }

  //Number of bytes in the data region of a node
  constexpr uint64_t datasizeBytes() const {
    return _blocksizeBytes - HEADERSIZE_BYTES;
  }

  //Maximum number of children an inner node can store
  constexpr uint64_t maxChildrenPerInnerNode() const {
    return datasizeBytes() / sizeof(DataInnerNode_ChildEntry);
  }

  //Maximum number of bytes a leaf can store
  constexpr uint64_t maxBytesPerLeaf() const {
    return datasizeBytes();
  }
private:
  uint32_t _blocksizeBytes;
};

class DataNodeView final {
public:
  DataNodeView(cpputils::unique_ref<blockstore::Block> block): _block(std::move(block)) {
  }
  ~DataNodeView() {}

  static DataNodeView create(blockstore::BlockStore *blockStore, const DataNodeLayout &layout, uint16_t formatVersion, uint8_t depth, uint32_t size, cpputils::Data data) {
    ASSERT(data.size() <= layout.datasizeBytes(), "Data is too large for node");
    cpputils::Data serialized = serialize_(layout, formatVersion, depth, size, std::move(data));
    ASSERT(serialized.size() == layout.blocksizeBytes(), "Wrong block size");
    auto block = blockStore->create(serialized);
    return DataNodeView(std::move(block));
  }

  static DataNodeView initialize(cpputils::unique_ref<blockstore::Block> block, const DataNodeLayout &layout, uint16_t formatVersion, uint8_t depth, uint32_t size, cpputils::Data data) {
    ASSERT(data.size() <= DataNodeLayout(block->size()).datasizeBytes(), "Data is too large for node");
    cpputils::Data serialized = serialize_(layout, formatVersion, depth, size, std::move(data));
    ASSERT(serialized.size() == block->size(), "Block has wrong size");
    block->write(serialized.data(), 0, serialized.size());
    return DataNodeView(std::move(block));
  }

  static DataNodeView overwrite(blockstore::BlockStore *blockStore, const DataNodeLayout &layout, uint16_t formatVersion, uint8_t depth, uint32_t size, const blockstore::BlockId &blockId, cpputils::Data data) {
    ASSERT(data.size() <= layout.datasizeBytes(), "Data is too large for node");
    cpputils::Data serialized = serialize_(layout, formatVersion, depth, size, std::move(data));
    auto block = blockStore->overwrite(blockId, std::move(serialized));
    return DataNodeView(std::move(block));
  }

  DataNodeView(DataNodeView &&rhs) = default;

  uint16_t FormatVersion() const {
    return cpputils::deserializeWithOffset<uint16_t>(_block->data(), DataNodeLayout::FORMAT_VERSION_OFFSET_BYTES);
  }

  void setFormatVersion(uint16_t value) {
    _block->write(&value, DataNodeLayout::FORMAT_VERSION_OFFSET_BYTES, sizeof(value));
  }

  uint8_t Depth() const {
    return cpputils::deserializeWithOffset<uint8_t>(_block->data(), DataNodeLayout::DEPTH_OFFSET_BYTES);
  }

  void setDepth(uint8_t value) {
    _block->write(&value, DataNodeLayout::DEPTH_OFFSET_BYTES, sizeof(value));
  }

  uint32_t Size() const {
    return cpputils::deserializeWithOffset<uint32_t>(_block->data(), DataNodeLayout::SIZE_OFFSET_BYTES);
  }

  void setSize(uint32_t value) {
    _block->write(&value, DataNodeLayout::SIZE_OFFSET_BYTES, sizeof(value));
  }

  const void *data() const {
    return static_cast<const uint8_t*>(_block->data()) + DataNodeLayout::HEADERSIZE_BYTES;
  }

  void write(const void *source, uint64_t offset, uint64_t size) {
    _block->write(source, offset + DataNodeLayout::HEADERSIZE_BYTES, size);
  }

  DataNodeLayout layout() const {
    return DataNodeLayout(_block->size());
  }

  cpputils::unique_ref<blockstore::Block> releaseBlock() {
    return std::move(_block);
  }

  const blockstore::Block &block() const {
    return *_block;
  }

  const blockstore::BlockId &blockId() const {
    return _block->blockId();
  }

  void flush() const {
    _block->flush();
  }

private:
  static cpputils::Data serialize_(const DataNodeLayout &layout, uint16_t formatVersion, uint8_t depth, uint32_t size, cpputils::Data data) {
    cpputils::Data result(layout.blocksizeBytes());
    cpputils::serialize<uint16_t>(result.dataOffset(layout.FORMAT_VERSION_OFFSET_BYTES), formatVersion);
    cpputils::serialize<uint8_t>(result.dataOffset(layout.DEPTH_OFFSET_BYTES), depth);
    cpputils::serialize<uint32_t>(result.dataOffset(layout.SIZE_OFFSET_BYTES), size);
    std::memcpy(result.dataOffset(layout.HEADERSIZE_BYTES), data.data(), data.size());
    std::memset(result.dataOffset(layout.HEADERSIZE_BYTES+data.size()), 0, layout.datasizeBytes()-data.size());
    return result;
  }

  cpputils::unique_ref<blockstore::Block> _block;

  DISALLOW_COPY_AND_ASSIGN(DataNodeView);

};

}
}
}

#endif