/*
 * Copyright 2017, Chế Vũ Gia Hy, cvghy116@gmail.com.
 * Copyright 2001-2008, Axel Dörfler, axeld@pinc-software.de.
 * This file may be used under the terms of the MIT License.
 */
#ifndef CACHED_BLOCK_H
#define CACHED_BLOCK_H

//!     interface for the block cache


#include "Volume.h"


//#define TRACE_BTRFS
#ifdef TRACE_BTRFS
#       define TRACE(x...) dprintf("\33[34mbtrfs:\33[0m " x)
#else
#       define TRACE(x...) ;
#endif


class CachedBlock {
public:
                                                        CachedBlock(Volume* volume);
                                                        CachedBlock(Volume* volume, off_t block);
                                                        ~CachedBlock();

                        void                    Keep();
                        void                    Unset();

                        const uint8*    SetTo(off_t block);
                        uint8*                  SetToWritable(off_t block, int32 transactionId,
                                                                bool empty);

                        const uint8*    Block() const { return fBlock; }
                        off_t                   BlockNumber() const { return fBlockNumber; }
                        bool                    IsWritable() const { return fWritable; }

private:
                                                        CachedBlock(const CachedBlock&);
                                                        CachedBlock& operator=(const CachedBlock&);
                                                                // no implementation

protected:
                        Volume*                 fVolume;
                        off_t                   fBlockNumber;
                        uint8*                  fBlock;
                        bool                    fWritable;
};


// inlines


inline
CachedBlock::CachedBlock(Volume* volume)
        :
        fVolume(volume),
        fBlockNumber(0),
        fBlock(NULL),
        fWritable(false)
{
}


inline
CachedBlock::CachedBlock(Volume* volume, off_t block)
        :
        fVolume(volume),
        fBlockNumber(0),
        fBlock(NULL),
        fWritable(false)
{
        SetTo(block);
}


inline
CachedBlock::~CachedBlock()
{
        Unset();
}


inline void
CachedBlock::Keep()
{
        fBlock = NULL;
}


inline void
CachedBlock::Unset()
{
        if (fBlock != NULL) {
                block_cache_put(fVolume->BlockCache(), fBlockNumber);
                fBlock = NULL;
        }
}


inline const uint8*
CachedBlock::SetTo(off_t block)
{
        Unset();
        fBlockNumber = block;
        return fBlock = (uint8*)block_cache_get(fVolume->BlockCache(), block);
}


inline uint8*
CachedBlock::SetToWritable(off_t block, int32 transactionId, bool empty)
{
        Unset();
        fBlockNumber = block;
        fWritable = true;
        if (empty) {
                fBlock = (uint8*)block_cache_get_empty(fVolume->BlockCache(),
                        block, transactionId);
        } else {
                fBlock = (uint8*)block_cache_get_writable(fVolume->BlockCache(),
                        block, transactionId);
        }

        return fBlock;
}


#endif  // CACHED_BLOCK_H