source: trunk/eraser/Eraser.Util.Native/FatApi.cpp @ 2516

/* 
 * $Id$
 * Copyright 2008-2012 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 <vector>
#include <windows.h>

#include "FatApi.h"

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

namespace Eraser {
namespace Util {
    FatApi::FatApi(VolumeInfo^ info)
    {
        BootSector = new FatBootSector();
        memset(BootSector, 0, sizeof(*BootSector));
        Fat = NULL;

        //Open the handle to the drive
        VolumeStream = info->Open(FileAccess::Read);

        //Then read the boot sector for information
        array<Byte>^ bootSector = gcnew array<Byte>(sizeof(*BootSector));
        VolumeStream->Seek(0, SeekOrigin::Begin);
        VolumeStream->Read(bootSector, 0, sizeof(*BootSector));
        Marshal::Copy(bootSector, 0, static_cast<IntPtr>(BootSector), bootSector->Length);

        //Then load the FAT
        LoadFat();
    }

    FatApi::FatApi(Stream^ stream)
    {
        BootSector = new FatBootSector();
        memset(BootSector, 0, sizeof(*BootSector));
        Fat = NULL;

        //Open the handle to the drive
        VolumeStream = stream;

        //Then read the boot sector for information
        array<Byte>^ bootSector = gcnew array<Byte>(sizeof(*BootSector));
        VolumeStream->Seek(0, SeekOrigin::Begin);
        VolumeStream->Read(bootSector, 0, sizeof(*BootSector));
        Marshal::Copy(bootSector, 0, static_cast<IntPtr>(BootSector), bootSector->Length);

        //Then load the FAT
        LoadFat();
    }

    FatDirectoryBase^ FatApi::LoadDirectory(String^ directory)
    {
        //Return the root directory if nothing is specified
        if (String::IsNullOrEmpty(directory))
            return LoadDirectory(DirectoryToCluster(directory), String::Empty, nullptr);

        array<wchar_t>^ pathSeparators = { Path::DirectorySeparatorChar, Path::AltDirectorySeparatorChar };
        int lastIndex = directory->LastIndexOfAny(pathSeparators);
        return LoadDirectory(DirectoryToCluster(directory), directory->Substring(lastIndex + 1),
            LoadDirectory(directory->Substring(0, lastIndex)));
    }

    unsigned long long FatApi::SectorToOffset(unsigned long long sector)
    {
        return sector * BootSector->BytesPerSector;
    }

    unsigned FatApi::SectorSizeToSize(unsigned size)
    {
        return size * BootSector->BytesPerSector;
    }

    unsigned FatApi::ClusterSizeToSize(unsigned size)
    {
        return size * (BootSector->BytesPerSector * BootSector->SectorsPerCluster);
    }

    array<Byte>^ FatApi::GetFileContents(unsigned cluster)
    {
        if (!IsClusterAllocated(cluster))
            throw gcnew ArgumentException(S::_(L"The specified cluster is not used."));

        array<Byte>^ result = gcnew array<Byte>(FileSize(cluster));
        const int clusterSize = ClusterSizeToSize(1);
        int nextIndex = 0;

        do
        {
            VolumeStream->Seek(ClusterToOffset(cluster), SeekOrigin::Begin);
            VolumeStream->Read(result, nextIndex, clusterSize);
            nextIndex += clusterSize;
        }
        while ((cluster = GetNextCluster(cluster)) != 0xFFFFFFFF);

        return result;
    }

    void FatApi::SetFileContents(array<Byte>^ buffer, unsigned cluster)
    {
        if (!IsClusterAllocated(cluster))
            throw gcnew ArgumentException(S::_(L"The specified cluster is not used."));
        if (static_cast<unsigned>(buffer->Length) != FileSize(cluster))
            throw gcnew ArgumentException(S::_(L"The provided file contents will not fit in the "
                L"allocated file."));

        int clusterSize = static_cast<int>(ClusterSizeToSize(1));
        for (int i = 0; i < buffer->Length; i += clusterSize)
        {
            VolumeStream->Seek(ClusterToOffset(cluster), SeekOrigin::Begin);
            VolumeStream->Write(buffer, i, clusterSize);
            cluster = GetNextCluster(cluster);
        }
    }

    FatDirectoryEntry::FatDirectoryEntry(String^ name, FatDirectoryBase^ parent,
        FatDirectoryEntryType type, unsigned cluster)
    {
        Name = name;
        Parent = parent;
        EntryType = type;
        Cluster = cluster;
    }

    String^ FatDirectoryEntry::FullName::get()
    {
        String^ result = Name;
        FatDirectoryEntry^ currentEntry = this;

        while (currentEntry->Parent != nullptr)
        {
            currentEntry = currentEntry->Parent;
            result = currentEntry->Name + Path::DirectorySeparatorChar + result;
        }

        return result;
    }

    FatDirectoryBase::FatDirectoryBase(String^ name, FatDirectoryBase^ parent, unsigned cluster)
        : FatDirectoryEntry(name, parent, FatDirectoryEntryType::Directory, cluster)
    {
        Entries = gcnew Dictionary<String^, FatDirectoryEntry^>();
        ReadDirectory();
    }

    void FatDirectoryBase::ClearDeletedEntries()
    {
        std::vector<::FatDirectoryEntry> validEntries;

        //Parse the directory structures
        for (::FatDirectoryEntry* i = Directory; i != Directory + DirectorySize; ++i)
        {
            //Check if we have checked the last valid entry
            if (i->Short.Name[0] == 0x00)
                break;

            //Skip deleted entries.
            if (static_cast<unsigned char>(i->Short.Name[0]) == 0xE5)
                continue;

            if (i->Short.Attributes == 0x0F)
            {
                //This is a long file name.
                ::FatDirectoryEntry* longFileNameBegin = i;
                for (unsigned char sequence = 0; i->Short.Attributes == 0x0F; ++i)
                {
                    if (static_cast<unsigned char>(i->Short.Name[0]) == 0xE5)
                        continue;
                    else if (!(i->LongFileName.Sequence & 0x40)) //Second entry onwards
                    {
                        //Check that the checksum of the file name is the same as the previous
                        //long file name entry, to ensure no corruption has taken place
                        if ((i - 1)->LongFileName.Checksum != i->LongFileName.Checksum)
                            continue;

                        //Check that the sequence is one less than the previous one.
                        if (sequence != i->LongFileName.Sequence + 1)
                            throw gcnew ArgumentException(S::_(L"Invalid directory entry."));
                    }
                    
                    sequence = i->LongFileName.Sequence & ~0x40;
                }

                //Checksum the string
                unsigned char sum = 0;
                char* shortFileName = i->Short.Name;
                for (int j = 11; j; --j)
                    sum = ((sum & 1) << 7) + (sum >> 1) + *shortFileName++;

                if (sum == (i - 1)->LongFileName.Checksum)
                {
                    //The previous few entries contained the correct file name. Save these entries
                    validEntries.insert(validEntries.end(), longFileNameBegin, i);
                }
                else
                {
                    --i;
                    continue;
                }
            }

            validEntries.push_back(*i);
        }

        //validEntries now contains the compacted list of directory entries. Zero
        //the memory used.
        memset(Directory, 0, DirectorySize * sizeof(::FatDirectoryEntry));

        //Copy the memory back if we have any valid entries. The root directory can
        //be empty (no . and .. entries)
        if (!validEntries.empty())
            memcpy(Directory, &validEntries.front(), validEntries.size() * sizeof(::FatDirectoryEntry));

        //Write the entries to disk
        WriteDirectory();
    }

    void FatDirectoryBase::ParseDirectory()
    {
        //Clear the list of entries
        Entries->Clear();

        //Parse the directory structures
        for (::FatDirectoryEntry* i = Directory; i != Directory + DirectorySize; ++i)
        {
            //Check if we have checked the last valid entry
            if (i->Short.Name[0] == 0x00)
                break;

            //Skip deleted entries.
            if (static_cast<unsigned char>(i->Short.Name[0]) == 0xE5)
                continue;

            if (i->Short.Attributes == 0x0F)
            {
                //This is a long file name.
                std::wstring longFileName;
                for (unsigned char sequence = 0; i->Short.Attributes == 0x0F; ++i)
                {
                    if (static_cast<unsigned char>(i->Short.Name[0]) == 0xE5)
                        continue;
                    else if (!(i->LongFileName.Sequence & 0x40)) //Second entry onwards
                    {
                        //Check that the checksum of the file name is the same as the previous
                        //long file name entry, to ensure no corruption has taken place
                        if ((i - 1)->LongFileName.Checksum != i->LongFileName.Checksum)
                            continue;

                        //Check that the sequence is one less than the previous one.
                        if (sequence != i->LongFileName.Sequence + 1)
                            throw gcnew ArgumentException(S::_(L"Invalid directory entry."));
                    }
                    else
                        longFileName.clear();
                    
                    sequence = i->LongFileName.Sequence & ~0x40;
                    std::wstring namePart(i->LongFileName.Name1, sizeof(i->LongFileName.Name1) / sizeof(i->LongFileName.Name1[0]));
                    namePart += std::wstring(i->LongFileName.Name2, sizeof(i->LongFileName.Name2) / sizeof(i->LongFileName.Name2[0]));
                    namePart += std::wstring(i->LongFileName.Name3, sizeof(i->LongFileName.Name3) / sizeof(i->LongFileName.Name3[0]));
                    namePart += longFileName;
                    longFileName = namePart;
                }

                //Checksum the string
                unsigned char sum = 0;
                char* shortFileName = i->Short.Name;
                for (int j = 11; j; --j)
                    sum = ((sum & 1) << 7) + (sum >> 1) + *shortFileName++;

                if (sum == (i - 1)->LongFileName.Checksum)
                {
                    //fileName contains the correct full long file name, strip the file name of the
                    //invalid characters.
                    String^ fileName = gcnew String(longFileName.c_str());
                    Entries->Add(fileName, gcnew FatDirectoryEntry(fileName, this,
                        (i->Short.Attributes & FILE_ATTRIBUTE_DIRECTORY) ?
                            FatDirectoryEntryType::Directory : FatDirectoryEntryType::File,
                        GetStartCluster(*i)));
                }
                else
                {
                    --i;
                    continue;
                }
            }

            //Skip the dot directories.
            if (i->Short.Name[0] == '.')
                continue;

            //Substitute 0x05 with 0xE5
            if (i->Short.Name[0] == 0x05)
                i->Short.Name[0] = static_cast<unsigned char>(0xE5);
            
            //Then read the 8.3 entry for the file details
            wchar_t shortFileName[8 + 3 + 2];
            if (mbstowcs(shortFileName, i->Short.Name, sizeof(i->Short.Name)) != sizeof(i->Short.Name))
                continue;

            //If the extension is blank, don't care about it
            if (strncmp(i->Short.Extension, "   ", 3) == 0)
            {
                shortFileName[8] = '\0';
            }
            else
            {
                mbstowcs(shortFileName + 9, i->Short.Extension, sizeof(i->Short.Extension) + 1);
                shortFileName[8] = L'.';
                shortFileName[8 + 3 + 1] = '\0';
            }

            String^ fileName = gcnew String(shortFileName);
            Entries->Add(fileName, gcnew FatDirectoryEntry(fileName, this,
                (i->Short.Attributes & FILE_ATTRIBUTE_DIRECTORY) ?
                    FatDirectoryEntryType::Directory : FatDirectoryEntryType::File,
                GetStartCluster(*i)));
        }
    }

    FatDirectory::FatDirectory(String^ name, FatDirectoryBase^ parent, unsigned cluster, FatApi^ api)
        : Api(api),
          FatDirectoryBase(name, parent, cluster)
    {
    }

    void FatDirectory::ReadDirectory()
    {
        array<Byte>^ dir = Api->GetFileContents(Cluster);
        DirectorySize = dir->Length / sizeof(::FatDirectoryEntry);
        Directory = new ::FatDirectoryEntry[DirectorySize];
        Marshal::Copy(dir, 0, static_cast<IntPtr>(Directory), dir->Length);

        ParseDirectory();
    }

    void FatDirectory::WriteDirectory()
    {
        array<Byte>^ buffer = gcnew array<Byte>(static_cast<int>(DirectorySize *
            sizeof(::FatDirectoryEntry)));
        Marshal::Copy(static_cast<IntPtr>(Directory), buffer, 0, buffer->Length);
        Api->SetFileContents(buffer, Cluster);
    }
}
}