FF_T_UINT32 FF_FindFreeCluster	(	FF_IOMAN *	pIoman,
		FF_ERROR *	pError
	)

Finds a Free Cluster and returns its number.

Parameters:

pIoman IOMAN Object.

Returns:: The number of the cluster found to be free.; 0 on error.

Definition at line 481 of file ff_fat.c.

Referenced by FF_CreateClusterChain(), FF_ExtendDirectory(), FF_ExtendFile(), and FF_MountPartition().

                                                                   {
    FF_BUFFER   *pBuffer;
    FF_T_UINT32 i, x, nCluster = pIoman->pPartition->LastFreeCluster;
    FF_T_UINT32 FatOffset;
    FF_T_UINT32 FatSector;
    FF_T_UINT32 FatSectorEntry;
    FF_T_UINT32 EntriesPerSector;
    FF_T_UINT32 FatEntry = 1;

    *pError = FF_ERR_NONE;

#ifdef FF_FAT12_SUPPORT
    if(pIoman->pPartition->Type == FF_T_FAT12) {    // FAT12 tables are too small to optimise, and would make it very complicated!
        return FF_FindFreeClusterOLD(pIoman, pError);
    }
#endif

    if(pIoman->pPartition->Type == FF_T_FAT32) {
        EntriesPerSector = pIoman->BlkSize / 4;
        FatOffset = nCluster * 4;
    } else {
        EntriesPerSector = pIoman->BlkSize / 2;
        FatOffset = nCluster * 2;
    }
    
    // HT addition: don't use non-existing clusters
    if (nCluster >= pIoman->pPartition->NumClusters) {
        *pError = FF_ERR_FAT_NO_FREE_CLUSTERS;
        return 0;
    }

    FatSector = (FatOffset / pIoman->pPartition->BlkSize);
    
    for(i = FatSector; i < pIoman->pPartition->SectorsPerFAT; i++) {
        pBuffer = FF_GetBuffer(pIoman, pIoman->pPartition->FatBeginLBA + i, FF_MODE_READ);
        {
            if(!pBuffer) {
                *pError = FF_ERR_DEVICE_DRIVER_FAILED;
                return 0;
            }
            for(x = nCluster % EntriesPerSector; x < EntriesPerSector; x++) {
                if(pIoman->pPartition->Type == FF_T_FAT32) {
                    FatOffset = x * 4;
                    FatSectorEntry  = FatOffset % pIoman->pPartition->BlkSize;
                    FatEntry = FF_getLong(pBuffer->pBuffer, (FF_T_UINT16)FatSectorEntry);
                    FatEntry &= 0x0fffffff; // Clear the top 4 bits.
                } else {
                    FatOffset = x * 2;
                    FatSectorEntry  = FatOffset % pIoman->pPartition->BlkSize;
                    FatEntry = (FF_T_UINT32) FF_getShort(pBuffer->pBuffer, (FF_T_UINT16)FatSectorEntry);
                }
                if(FatEntry == 0x00000000) {
                    FF_ReleaseBuffer(pIoman, pBuffer);
                    pIoman->pPartition->LastFreeCluster = nCluster;
                    
                    return nCluster;
                }
                
                nCluster++;
            }   
        }
        FF_ReleaseBuffer(pIoman, pBuffer);
    }

    return 0;
}

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