source: trunk/eraser6/Eraser.Util.FileSystem/Fat16Api.cpp @ 1227

/* 
 * $Id$
 * Copyright 2009 The Eraser Project
 * Original Author: Joel Low <lowjoel@users.sourceforge.net>
 * Modified By: 
 * 
 * This file is part of Eraser.
 * 
 * Eraser is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 * 
 * Eraser is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 * 
 * A copy of the GNU General Public License can be found at
 * <http://www.gnu.org/licenses/>.
 */

#include <stdafx.h>
#include "FatApi.h"

using namespace System::IO;
using namespace System::Runtime::InteropServices;

namespace Eraser {
namespace Util {
    Fat16Api::Fat16Api(VolumeInfo^ info) : Fat12Or16Api(info)
    {
        //Sanity checks: check that this volume is FAT16!
        if (IsFat12() || info->VolumeFormat == L"FAT12")
            throw gcnew ArgumentException(L"The volume provided is not a FAT16 volume.");
    }

    Fat16Api::Fat16Api(VolumeInfo^ info, IO::Stream^ stream) : Fat12Or16Api(info, stream)
    {
        //Sanity checks: check that this volume is FAT16!
        if (IsFat12() || info->VolumeFormat == L"FAT12")
            throw gcnew ArgumentException(L"The volume provided is not a FAT16 volume.");
    }

    bool Fat16Api::IsClusterAllocated(unsigned cluster)
    {
        unsigned short* fatPtr = reinterpret_cast<unsigned short*>(Fat);
        if (
            fatPtr[cluster] <= 0x0001 ||
            (fatPtr[cluster] >= 0xFFF0 && fatPtr[cluster] <= 0xFFF6) ||
            fatPtr[cluster] == 0xFFF7
        )
            return false;

        return true;
    }

    unsigned Fat16Api::GetNextCluster(unsigned cluster)
    {
        unsigned short* fatPtr = reinterpret_cast<unsigned short*>(Fat);
        if (fatPtr[cluster] <= 0x0001 || (fatPtr[cluster] >= 0xFFF0 && fatPtr[cluster] <= 0xFFF6))
            throw gcnew ArgumentException(L"Invalid FAT cluster: cluster is marked free.");
        else if (fatPtr[cluster] == 0xFFF7)
            throw gcnew ArgumentException(L"Invalid FAT cluster: cluster is marked bad.");
        else if (fatPtr[cluster] >= 0xFFF8)
            return 0xFFFFFFFF;
        else
            return fatPtr[cluster];
    }

    unsigned Fat16Api::FileSize(unsigned cluster)
    {
        unsigned short* fatPtr = reinterpret_cast<unsigned short*>(Fat);
        for (unsigned result = 1; ; ++result)
        {
            if (fatPtr[cluster] <= 0x0001 || (fatPtr[cluster] >= 0xFFF0 && fatPtr[cluster] <= 0xFFF6))
                throw gcnew ArgumentException(L"Invalid FAT cluster: cluster is marked free.");
            else if (fatPtr[cluster] == 0xFFF7)
                throw gcnew ArgumentException(L"Invalid FAT cluster: cluster is marked bad.");
            else if (fatPtr[cluster] >= 0xFFF8)
                return result * ClusterSize;
            else
                cluster = fatPtr[cluster];
        }
    }
}
}