source: trunk/eraser6/Eraser.Util.FileSystem/Fat12Or16Api.cpp @ 1228

/* 
 * $Id$
 * 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 {
    Fat12Or16Api::Fat12Or16Api(VolumeInfo^ info) : FatApi(info)
    {
        //Sanity checks: check that this volume is FAT12 or FAT16!
        if (info->VolumeFormat != L"FAT12" && info->VolumeFormat != "FAT16")
            throw gcnew ArgumentException(L"The volume provided is not a FAT12 or FAT16 volume.");
    }

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

    void Fat12Or16Api::LoadFat()
    {
        Fat = new char[SectorSizeToSize(BootSector->SectorsPerFat)];

        //Seek to the FAT
        VolumeStream->Seek(SectorToOffset(BootSector->ReservedSectorCount), SeekOrigin::Begin);

        //Read the FAT
        array<Byte>^ buffer = gcnew array<Byte>(SectorSizeToSize(BootSector->SectorsPerFat));
        VolumeStream->Read(buffer, 0, SectorSizeToSize(BootSector->SectorsPerFat));
        Marshal::Copy(buffer, 0, static_cast<IntPtr>(Fat), buffer->Length);
    }

    FatDirectoryBase^ Fat12Or16Api::LoadDirectory(unsigned cluster, String^ name,
        FatDirectoryBase^ parent)
    {
        //Return the root directory if we get cluster 0, name is blank and the parent is null
        if (cluster == 0 && name == String::Empty && parent == nullptr)
            return gcnew RootDirectory(this);
        return gcnew Directory(name, parent, cluster, this);
    }

    long long Fat12Or16Api::ClusterToOffset(unsigned cluster)
    {
        unsigned long long sector = BootSector->ReservedSectorCount +                                           //Reserved area
            BootSector->FatCount * BootSector->SectorsPerFat +                                                  //FAT area
            (BootSector->RootDirectoryEntryCount * sizeof(::FatDirectoryEntry) / (ClusterSize / SectorSize)) +  //Root directory area
            (static_cast<unsigned long long>(cluster) - 2) * (ClusterSize / SectorSize);
        return SectorToOffset(sector);
    }

    unsigned Fat12Or16Api::DirectoryToCluster(String^ path)
    {
        //The path must start with a backslash as it must be volume-relative.
        if (path->Length != 0 && path[0] != L'\\')
            throw gcnew ArgumentException(L"The path provided is not volume relative. " +
                gcnew String(L"Volume relative paths must begin with a backslash."));

        //Chop the path into it's constituent directory components
        array<String^>^ components = path->Split(Path::DirectorySeparatorChar,
            Path::AltDirectorySeparatorChar);

        //Traverse the directories until we get the cluster we want.
        unsigned cluster = 0;
        FatDirectoryBase^ parentDir = gcnew RootDirectory(this);
        for each (String^ component in components)
        {
            if (component == String::Empty)
                break;

            parentDir = LoadDirectory(cluster, parentDir == nullptr ? nullptr : parentDir->Name,
                parentDir);
            cluster = parentDir->Items[component]->Cluster;
        }

        return cluster;
    }

    bool Fat12Or16Api::IsFat12()
    {
        unsigned long long numberOfSectors = (BootSector->SectorCount16 == 0 ?
            BootSector->SectorCount32 : BootSector->SectorCount16);
        unsigned long long availableSectors = numberOfSectors - (
            BootSector->ReservedSectorCount +                                                                   //Reserved area
            BootSector->FatCount * BootSector->SectorsPerFat +                                                  //FAT area
            (BootSector->RootDirectoryEntryCount * sizeof(::FatDirectoryEntry) / (ClusterSize / SectorSize))    //Root directory area
        );
        unsigned long long numberOfClusters = availableSectors / (ClusterSize / SectorSize);

        return numberOfClusters < 0xFF0;
    }

    Fat12Or16Api::RootDirectory::RootDirectory(Fat12Or16Api^ api)
        : Api(api),
          FatDirectoryBase(String::Empty, nullptr, 0)
    {
    }

    void Fat12Or16Api::RootDirectory::ReadDirectory()
    {
        //Calculate the starting sector of the root directory
        unsigned long long startPos = Api->SectorToOffset(Api->BootSector->ReservedSectorCount +
            Api->BootSector->FatCount * Api->BootSector->SectorsPerFat);
        int directoryLength = Api->BootSector->RootDirectoryEntryCount *
            sizeof(::FatDirectoryEntry);

        array<Byte>^ buffer = gcnew array<Byte>(directoryLength);
        Api->VolumeStream->Seek(startPos, SeekOrigin::Begin);
        Api->VolumeStream->Read(buffer, 0, directoryLength);

        DirectorySize = Api->BootSector->RootDirectoryEntryCount;
        Directory = new ::FatDirectoryEntry[DirectorySize];
        Marshal::Copy(buffer, 0, static_cast<IntPtr>(Directory), directoryLength);

        ParseDirectory();
    }

    void Fat12Or16Api::RootDirectory::WriteDirectory()
    {
        //Calculate the starting sector of the root directory
        unsigned long long startPos = Api->SectorToOffset(Api->BootSector->ReservedSectorCount +
            Api->BootSector->FatCount * Api->BootSector->SectorsPerFat);
        int directoryLength = Api->BootSector->RootDirectoryEntryCount *
            sizeof(::FatDirectoryEntry);

        array<Byte>^ buffer = gcnew array<Byte>(directoryLength);
        Marshal::Copy(static_cast<IntPtr>(Directory), buffer, 0, directoryLength);
        Api->VolumeStream->Seek(startPos, SeekOrigin::Begin);
        Api->VolumeStream->Write(buffer, 0, directoryLength);
    }

    unsigned Fat12Or16Api::RootDirectory::GetStartCluster(::FatDirectoryEntry& directory)
    {
        if (directory.Short.Attributes == 0x0F)
            throw gcnew ArgumentException(L"The provided directory is a long file name.");
        return directory.Short.StartClusterLow;
    }

    Fat12Or16Api::Directory::Directory(String^ name, FatDirectoryBase^ parent, unsigned cluster,
        Fat12Or16Api^ api) : FatDirectory(name, parent, cluster, api)
    {
    }

    unsigned Fat12Or16Api::Directory::GetStartCluster(::FatDirectoryEntry& directory)
    {
        if (directory.Short.Attributes == 0x0F)
            throw gcnew ArgumentException(L"The provided directory is a long file name.");
        return directory.Short.StartClusterLow;
    }
}
}