libcryfs/implementations/testfake/FakeBlockStore.h

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#pragma once
#ifndef BLOCKSTORE_IMPLEMENTATIONS_INMEMORY_INMEMORYBLOCKSTORE_H_
#define BLOCKSTORE_IMPLEMENTATIONS_INMEMORY_INMEMORYBLOCKSTORE_H_
#include "../../interface/helpers/BlockStoreWithRandomKeys.h"
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#include "../../utils/Data.h"
#include "messmer/cpp-utils/macros.h"
#include <mutex>
#include <map>
namespace blockstore {
namespace testfake {
class FakeBlock;
/**
* This blockstore is meant to be used for unit tests when the module under test needs a blockstore to work with.
* It basically is the same as the InMemoryBlockStore, but much less forgiving for programming mistakes.
*
* InMemoryBlockStore for example simply ignores flushing and gives you access to the same data region each time
* you request a block. This is very performant, but also forgiving to mistakes. Say you write over the boundaries
* of a block, then you wouldn't notice, since the next time you access the block, the overflow data is (probably)
* still there. Or say an application is relying on flushing the block store in the right moment. Since flushing
* is a no-op in InMemoryBlockStore, you wouldn't notice either.
*
* So this FakeBlockStore has a background copy of each block. When you request a block, you will get a copy of
* the data (instead of a direct pointer as InMemoryBlockStore does) and flushing will copy the data back to the
* background. This way, tests are more likely to fail if they use the blockstore wrongly.
*/
class FakeBlockStore: public BlockStoreWithRandomKeys {
public:
FakeBlockStore();
std::unique_ptr<Block> create(const Key &key, size_t size) override;
std::unique_ptr<Block> load(const Key &key) override;
void remove(std::unique_ptr<Block> block) override;
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uint64_t numBlocks() const override;
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void updateData(const Key &key, const Data &data);
private:
std::map<std::string, Data> _blocks;
//This vector keeps a handle of the data regions for all created FakeBlock objects.
//This way, it is ensured that no two created FakeBlock objects will work on the
//same data region. Without this, it could happen that a test case creates a FakeBlock,
//destructs it, creates another one, and the new one gets the same memory region.
//We want to avoid this for the reasons mentioned above (overflow data).
std::vector<std::shared_ptr<Data>> _used_dataregions_for_blocks;
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std::unique_ptr<Block> makeFakeBlockFromData(const Key &key, const Data &data);
DISALLOW_COPY_AND_ASSIGN(FakeBlockStore);
};
}
}
#endif