/// <summary>
/// Scan FAT o miniFAT for free sectors to reuse.
/// </summary>
/// <param name="sType">Type of sector to look for</param>
/// <returns>A stack of available sectors or minisectors already allocated</returns>
internal Queue<Sector> FindFreeSectors(SectorType sType)
{
var freeList = new Queue<Sector>();
if (sType == SectorType.Normal)
{
var fatChain = GetSectorChain(-1, SectorType.FAT);
var fatStream = new StreamView(fatChain, GetSectorSize(), _header.FATSectorsNumber*GetSectorSize(),
SourceStream);
var idx = 0;
while (idx < _sectors.Count)
{
var id = fatStream.ReadInt32();
if (id == Sector.FreeSector)
{
if (_sectors[idx] == null)
{
var sector = new Sector(GetSectorSize(), SourceStream) {Id = idx};
_sectors[idx] = sector;
}
freeList.Enqueue(_sectors[idx]);
}
idx++;
}
}
else
{
var miniFAT
= GetSectorChain(_header.FirstMiniFATSectorId, SectorType.Normal);
var miniFATView
= new StreamView(miniFAT, GetSectorSize(), _header.MiniFATSectorsNumber*Sector.MinisectorSize,
SourceStream);
var miniStream
= GetSectorChain(RootEntry.StartSector, SectorType.Normal);
var miniStreamView
= new StreamView(miniStream, GetSectorSize(), RootStorage.Size, SourceStream);
long ptr = 0;
var nMinisectors = (int) (miniStreamView.Length/Sector.MinisectorSize);
while (ptr < nMinisectors)
{
//AssureLength(miniStreamView, (int)miniFATView.Length);
var id = miniFATView.ReadInt32();
ptr += 4;
if (id != Sector.FreeSector) continue;
var miniSector = new Sector(Sector.MinisectorSize, SourceStream)
{
Id = (int) ((ptr - 4)/4),
Type = SectorType.Mini
};
miniStreamView.Seek(miniSector.Id*Sector.MinisectorSize, SeekOrigin.Begin);
miniStreamView.Read(miniSector.GetData(), 0, Sector.MinisectorSize);
freeList.Enqueue(miniSector);
}
}
return freeList;
}
/// <summary>
/// Get a standard sector chain
/// </summary>
/// <param name="secId">First SecID of the required chain</param>
/// <returns>A list of sectors</returns>
/// <exception cref="CFCorruptedFileException">Raised when the file is corrupt</exception>
private List<Sector> GetNormalSectorChain(int secId)
{
var result = new List<Sector>();
var nextSecId = secId;
var fatSectors = GetFatSectorChain();
var fatStream
= new StreamView(fatSectors, GetSectorSize(), fatSectors.Count*GetSectorSize(), SourceStream);
while (true)
{
if (nextSecId == Sector.Endofchain) break;
if (nextSecId >= _sectors.Count)
throw new CFCorruptedFileException(
string.Format(
"Next Sector ID reference an out of range sector. NextID : {0} while sector count {1}",
nextSecId, _sectors.Count));
var sector = _sectors[nextSecId];
if (sector == null)
{
sector = new Sector(GetSectorSize(), SourceStream) {Id = nextSecId, Type = SectorType.Normal};
_sectors[nextSecId] = sector;
}
result.Add(sector);
fatStream.Seek(nextSecId*4, SeekOrigin.Begin);
var next = fatStream.ReadInt32();
if (next != nextSecId)
nextSecId = next;
else
throw new CFCorruptedFileException("Cyclic sector chain found. File is corrupted");
}
return result;
}
