BufferManager.h

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// storage/BufferManager.h
#pragma once
 
#include "tdb.h"
 
#include <absl/container/flat_hash_map.h>
 
#include "utils/Latch.h"
#include "utils/ResourceGuard.h"
 
namespace taco {
 
// private data structure
struct BufferMeta;
 
struct BufferUnpin {
    void operator()(BufferId bufid);
};
 
struct BufferUnlatch {
    void operator()(BufferId bufid);
};
 
using ScopedBufferId = ResourceGuard<BufferId, BufferUnpin,
                                     BufferId, INVALID_BUFID>;
 
using ScopedBufferLatch = ResourceGuard<BufferId, BufferUnlatch,
                                        BufferId, INVALID_BUFID>;
 
class BufferManager {
public:
    BufferManager();
 
    ~BufferManager();
 
    void Init(BufferId buffer_size);
 
 
    void Destroy();
 
    BufferId PinPage(PageNumber pid, char **frame);
 
    BufferId PinPage(PageNumber pid, char **frame, FileId expected_fid);
 
    void UnpinPage(BufferId bufid);
 
    void
    UnpinPage(ScopedBufferId &bufid) {
        bufid.Reset();
    }
 
    BufferId LatchPage(BufferId bufid, LatchMode mode);
 
    void UnlatchPage(BufferId bufid);
 
    void UnlatchPage(ScopedBufferLatch bufid) {
        bufid.Reset();
    }
 
    void MarkDirty(BufferId bufid);
 
    PageNumber GetPageNumber(BufferId bufid) const;
 
    char* GetBuffer(BufferId bufid) const;
 
private:
    void Flush();
 
    BufferId GetFreeFrame();
 
    bool initialized;
    absl::flat_hash_map<PageNumber, BufferId> lookup_table;
    BufferId n;
    BufferId clock_hand;
    BufferMeta* metas;
    char* buffer_frames;
 
};
 
}   // namespace taco