//this file is part of eMule
//Copyright (C)2002 Merkur ( merkur-@users.sourceforge.net / http://www.emule-project.net )
//
//This program 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 2 of the License, or (at your option) any later version.
//
//This program 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.
//
//You should have received a copy of the GNU General Public License
//along with this program; if not, write to the Free Software
//Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
#include "stdafx.h"
#include "emule.h"
#include "ArchiveRecovery.h"
#include "OtherFunctions.h"
#include "Preferences.h"
#include "PartFile.h"
#include <zlib/zlib.h>

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif


// At some point it may be worth displaying messages to alert the user if there were errors, or where to find the file.

void CArchiveRecovery::recover(CPartFile *partFile, bool preview)
{
	if (partFile->m_bPreviewing || partFile->m_bRecoveringArchive)
		return;
	partFile->m_bRecoveringArchive = true;

	AddLogLine(true, GetResString(IDS_ATTEMPTING_RECOVERY) );

	// Get the current filled list for this file
	CTypedPtrList<CPtrList, Gap_Struct*> *filled = new CTypedPtrList<CPtrList, Gap_Struct*>;
	partFile->GetFilledList(filled);

	// The rest of the work can be safely done in a new thread
	ThreadParam *tp = new ThreadParam;
	tp->partFile = partFile;
	tp->filled = filled;
	tp->preview = preview;
	// - do NOT use Windows API 'CreateThread' to create a thread which uses MFC/CRT -> lot of mem leaks!
	if (!AfxBeginThread(run, (LPVOID)tp)){
		partFile->m_bRecoveringArchive = false;
		AddLogLine(true, GetResString(IDS_RECOVERY_FAILED));
		// Need to delete the memory here as won't be done in thread
		DeleteMemory(tp);
	}
}

UINT AFX_CDECL CArchiveRecovery::run(LPVOID lpParam)
{
	ThreadParam *tp = (ThreadParam *)lpParam;
	DbgSetThreadName("ArchiveRecovery");

	//::SetThreadLocale(thePrefs.GetLanguageID()); // 01.06.03 EC - ArchiveRecovery Thread wasn't localized

	if (!performRecovery(tp->partFile, tp->filled, tp->preview))
		AddLogLine(true, GetResString(IDS_RECOVERY_FAILED));

	tp->partFile->m_bRecoveringArchive = false;

	// Delete memory used by copied gap list
	DeleteMemory(tp);

	return 0;
}

bool CArchiveRecovery::performRecovery(CPartFile *partFile, CTypedPtrList<CPtrList, Gap_Struct*> *filled, bool preview)
{
	bool success = false;
	try
	{
		// Copy the file
		CString tempFileName = CString(thePrefs.GetTempDir()) + CString("\\") + CString(partFile->GetFileName()).Mid(0,5) + CString("-rec.tmp");
		if (!CopyFile(partFile, filled, tempFileName))
			return false;

		// Open temp file for reading
		CFile temp;
		if (!temp.Open(tempFileName, CFile::modeRead))
			return false;

		// Open the output file
		CString ext = CString(partFile->GetFileName()).Right(4);
		CString outputFileName = CString(thePrefs.GetTempDir()) + CString("\\") + CString(partFile->GetFileName()).Mid(0,5) + CString("-rec") + ext;
		CFile output;
		if (output.Open(outputFileName, CFile::modeWrite | CFile::shareExclusive | CFile::modeCreate))
		{
			// Process the output file
			if (ext.CompareNoCase(".zip") == 0)
				success = recoverZip(&temp, &output, filled, (temp.GetLength() == partFile->GetFileSize()));
			else if (ext.CompareNoCase(".rar") == 0)
				success = recoverRar(&temp, &output, filled);

			// Close output
			output.Close();
		}
		// Close temp file
		temp.Close();

		// Report success
		if (success)
		{
			AddLogLine(true, GetResString(IDS_RECOVERY_SUCCESSFUL));
			// Preview file if required
			if (preview)
			{
				SHELLEXECUTEINFO SE;
				memset(&SE,0,sizeof(SE));
				SE.fMask = SEE_MASK_NOCLOSEPROCESS ;
				SE.lpVerb = "open";
				SE.lpFile = outputFileName.GetBuffer();
				SE.nShow = SW_SHOW;
				SE.cbSize = sizeof(SE);
				ShellExecuteEx(&SE);
				if (SE.hProcess)
				{
					WaitForSingleObject(SE.hProcess, INFINITE);
					CloseHandle(SE.hProcess);
				}
				CFile::Remove(outputFileName);
			}
		}

		// Remove temp file
		CFile::Remove(tempFileName);
	}
	catch (CFileException* error){
		error->Delete();
	}
	catch (...){
		ASSERT(0);
	}
	return success;
}

bool CArchiveRecovery::recoverZip(CFile *zipInput, CFile *zipOutput, CTypedPtrList<CPtrList, Gap_Struct*> *filled, bool fullSize)
{
	bool retVal = false;
	long fileCount = 0;
	try
	{
		CTypedPtrList<CPtrList, ZIP_CentralDirectory*> centralDirectoryEntries;
		Gap_Struct *fill;

		// If the central directory is intact this is simple
		if (fullSize && readZipCentralDirectory(zipInput, &centralDirectoryEntries, filled))
		{
			if (centralDirectoryEntries.GetCount() == 0)
				return false;
			ZIP_CentralDirectory *cdEntry;
			POSITION pos = centralDirectoryEntries.GetHeadPosition();
			bool deleteCD;
			for (int i=centralDirectoryEntries.GetCount(); i>0; i--)
			{
				deleteCD = false;
				cdEntry = centralDirectoryEntries.GetAt(pos);
				uint32 lenEntry = sizeof(ZIP_Entry) + cdEntry->lenFilename + cdEntry->lenExtraField + cdEntry->lenCompressed;
				if (IsFilled(cdEntry->relativeOffsetOfLocalHeader, cdEntry->relativeOffsetOfLocalHeader + lenEntry, filled))
				{
					zipInput->Seek(cdEntry->relativeOffsetOfLocalHeader, CFile::begin);
					// Update offset
					cdEntry->relativeOffsetOfLocalHeader = zipOutput->GetPosition();
					if (!processZipEntry(zipInput, zipOutput, lenEntry, NULL))
						deleteCD = true;
				}
				else
					deleteCD = true;

				if (deleteCD)
				{
					delete [] cdEntry->filename;
					if (cdEntry->lenExtraField > 0)
						delete [] cdEntry->extraField;
					if (cdEntry->lenComment > 0)
						delete [] cdEntry->comment;
					delete cdEntry;
					POSITION del = pos;
					centralDirectoryEntries.GetNext(pos);
					centralDirectoryEntries.RemoveAt(del);
				}
				else
					centralDirectoryEntries.GetNext(pos);
			}
		}
		else // Have to scan the file the hard way
		{		
			// Loop through filled areas of the file looking for entries
			POSITION pos = filled->GetHeadPosition();
			while (pos != NULL)
			{
				fill = filled->GetNext(pos);
				uint32 filePos = zipInput->GetPosition();
				// The file may have been positioned to the next entry in ScanForMarker() or processZipEntry()
				if (filePos > fill->end)
					continue;
				if (filePos < fill->start)
					zipInput->Seek(fill->start, CFile::begin);

				// If there is any problem, then don't bother checking the rest of this part
				for (;;)
				{
					// Scan for entry marker within this filled area
					if (!scanForZipMarker(zipInput, (uint32)ZIP_LOCAL_HEADER_MAGIC, (fill->end - zipInput->GetPosition() + 1)))
						break;
					if (zipInput->GetPosition() > fill->end)
						break;
					if (!processZipEntry(zipInput, zipOutput, (fill->end - zipInput->GetPosition() + 1), &centralDirectoryEntries))
						break;
				}
			}
		}

		// Remember offset before CD entries
		uint32 startOffset = zipOutput->GetPosition();

		// Write all central directory entries
		fileCount = centralDirectoryEntries.GetCount();
		if (fileCount > 0)
		{
			ZIP_CentralDirectory *cdEntry;
			POSITION pos = centralDirectoryEntries.GetHeadPosition();
			while (pos != NULL)
			{
				cdEntry = centralDirectoryEntries.GetNext(pos);

				writeUInt32(zipOutput, ZIP_CD_MAGIC);
				writeUInt16(zipOutput, cdEntry->versionMadeBy);
				writeUInt16(zipOutput, cdEntry->versionToExtract);
				writeUInt16(zipOutput, cdEntry->generalPurposeFlag);
				writeUInt16(zipOutput, cdEntry->compressionMethod);
				writeUInt16(zipOutput, cdEntry->lastModFileTime);
				writeUInt16(zipOutput, cdEntry->lastModFileDate);
				writeUInt32(zipOutput, cdEntry->crc32);
				writeUInt32(zipOutput, cdEntry->lenCompressed);
				writeUInt32(zipOutput, cdEntry->lenUnompressed);
				writeUInt16(zipOutput, cdEntry->lenFilename);
				writeUInt16(zipOutput, cdEntry->lenExtraField);
				writeUInt16(zipOutput, cdEntry->lenComment);
				writeUInt16(zipOutput, 0); // Disk number start
				writeUInt16(zipOutput, cdEntry->internalFileAttributes);
				writeUInt32(zipOutput, cdEntry->externalFileAttributes);
				writeUInt32(zipOutput, cdEntry->relativeOffsetOfLocalHeader);
				zipOutput->Write(cdEntry->filename, cdEntry->lenFilename);
				if (cdEntry->lenExtraField > 0)
					zipOutput->Write(cdEntry->extraField, cdEntry->lenExtraField);
				if (cdEntry->lenComment > 0)
					zipOutput->Write(cdEntry->comment, cdEntry->lenComment);

				delete [] cdEntry->filename;
				if (cdEntry->lenExtraField > 0)
					delete [] cdEntry->extraField;
				if (cdEntry->lenComment > 0)
					delete [] cdEntry->comment;
				delete cdEntry;
			}

			// Remember offset before CD entries
			uint32 endOffset = zipOutput->GetPosition();

			// Write end of central directory
			writeUInt32(zipOutput, ZIP_END_CD_MAGIC);
			writeUInt16(zipOutput, 0); // Number of this disk
			writeUInt16(zipOutput, 0); // Number of the disk with the start of the central directory
			writeUInt16(zipOutput, fileCount);
			writeUInt16(zipOutput, fileCount);
			writeUInt32(zipOutput, endOffset - startOffset);
			writeUInt32(zipOutput, startOffset);
			writeUInt16(zipOutput, strlen(ZIP_COMMENT));
			zipOutput->Write(ZIP_COMMENT, strlen(ZIP_COMMENT));

			centralDirectoryEntries.RemoveAll();
		}
		retVal = true;
	}
	catch (CFileException* error){
		error->Delete();
	}
	catch (...){
		ASSERT(0);
	}

	// Tell the user how many files were recovered
	CString msg;	
	if (fileCount == 1)
		msg = GetResString(IDS_RECOVER_SINGLE);
	else
		msg.Format(GetResString(IDS_RECOVER_MULTIPLE), fileCount);
	//AfxMessageBox(msg, MB_OK | MB_ICONINFORMATION);
	AddLogLine(true, _T("%s"), msg);

	return retVal;
}

bool CArchiveRecovery::readZipCentralDirectory(CFile *zipInput, CTypedPtrList<CPtrList, ZIP_CentralDirectory*> *centralDirectoryEntries, CTypedPtrList<CPtrList, Gap_Struct*> *filled)
{
	bool retVal = false;
	try
	{
		// Ideally this zip file will not have a comment and the End-CD will be easy to find
		zipInput->Seek(-22, CFile::end);
		if (!(readUInt32(zipInput) == ZIP_END_CD_MAGIC))
		{
			// Have to look for it, comment could be up to 65535 chars but only try with less than 1k
			zipInput->Seek(-1046, CFile::end);
			if (!scanForZipMarker(zipInput, (uint32)ZIP_END_CD_MAGIC, 1046))
				return false;
			// Skip it again
			readUInt32(zipInput);
		}

		// Found End-CD
		// Only interested in offset of first CD
		zipInput->Seek(12, CFile::current);
		uint32 startOffset = readUInt32(zipInput);
		if (!IsFilled(startOffset, zipInput->GetLength(), filled))
			return false;

		// Goto first CD and start reading
		zipInput->Seek(startOffset, CFile::begin);
		ZIP_CentralDirectory *cdEntry;
		while (readUInt32(zipInput) == ZIP_CD_MAGIC)
		{
			cdEntry = new ZIP_CentralDirectory;
			cdEntry->versionMadeBy				= readUInt16(zipInput);
			cdEntry->versionToExtract			= readUInt16(zipInput);
			cdEntry->generalPurposeFlag			= readUInt16(zipInput);
			cdEntry->compressionMethod			= readUInt16(zipInput);
			cdEntry->lastModFileTime			= readUInt16(zipInput);
			cdEntry->lastModFileDate			= readUInt16(zipInput);
			cdEntry->crc32						= readUInt32(zipInput);
			cdEntry->lenCompressed				= readUInt32(zipInput);
			cdEntry->lenUnompressed				= readUInt32(zipInput);
			cdEntry->lenFilename				= readUInt16(zipInput);
			cdEntry->lenExtraField				= readUInt16(zipInput);
			cdEntry->lenComment					= readUInt16(zipInput);
			cdEntry->diskNumberStart			= readUInt16(zipInput);
			cdEntry->internalFileAttributes		= readUInt16(zipInput);
			cdEntry->externalFileAttributes		= readUInt32(zipInput);
			cdEntry->relativeOffsetOfLocalHeader= readUInt32(zipInput);

			if (cdEntry->lenFilename > 0)
			{
				cdEntry->filename					= new BYTE[cdEntry->lenFilename];
				zipInput->Read(cdEntry->filename, cdEntry->lenFilename);
			}
			if (cdEntry->lenExtraField > 0)
			{
				cdEntry->extraField					= new BYTE[cdEntry->lenExtraField];
				zipInput->Read(cdEntry->extraField, cdEntry->lenExtraField);
			}
			if (cdEntry->lenComment > 0)
			{
				cdEntry->comment					= new BYTE[cdEntry->lenComment];
				zipInput->Read(cdEntry->comment, cdEntry->lenComment);
			}

			centralDirectoryEntries->AddTail(cdEntry);
		}

		retVal = true;
	}
	catch (CFileException* error){
		error->Delete();
	}
	catch (...){
		ASSERT(0);
	}
	return retVal;
}

bool CArchiveRecovery::processZipEntry(CFile *zipInput, CFile *zipOutput, uint32 available, CTypedPtrList<CPtrList, ZIP_CentralDirectory*> *centralDirectoryEntries)
{
	if (available < 26)
		return false;

	bool retVal = false;
	try
	{
		// Need to know where it started
		long startOffset = zipOutput->GetPosition();

		// Entry format :
		//  4      2 bytes  Version needed to extract
		//  6      2 bytes  General purpose bit flag
		//  8      2 bytes  Compression method
		// 10      2 bytes  Last mod file time
		// 12      2 bytes  Last mod file date
		// 14      4 bytes  CRC-32
		// 18      4 bytes  Compressed size (n)
		// 22      4 bytes  Uncompressed size
		// 26      2 bytes  Filename length (f)
		// 28      2 bytes  Extra field length (e)
		//        (f)bytes  Filename
		//        (e)bytes  Extra field
		//        (n)bytes  Compressed data

		// Read header
		if (readUInt32(zipInput) != ZIP_LOCAL_HEADER_MAGIC)
			return false;

		ZIP_Entry entry={0};
		entry.versionToExtract		= readUInt16(zipInput);
		entry.generalPurposeFlag	= readUInt16(zipInput);
		entry.compressionMethod		= readUInt16(zipInput);
		entry.lastModFileTime		= readUInt16(zipInput);
		entry.lastModFileDate		= readUInt16(zipInput);
		entry.crc32					= readUInt32(zipInput);
		entry.lenCompressed			= readUInt32(zipInput);
		entry.lenUncompressed		= readUInt32(zipInput);
		entry.lenFilename			= readUInt16(zipInput);
		entry.lenExtraField			= readUInt16(zipInput);
		
		// Do some quick checks at this stage that data is looking ok
		if ((entry.crc32 == 0) || (entry.lenCompressed == 0) || (entry.lenUncompressed == 0) || (entry.lenFilename == 0))
			return false;

		// Is this entry complete
		if ((entry.lenFilename + entry.lenExtraField + entry.lenCompressed) > (available - 26))
		{
			// Move the file pointer to the start of the next entry
			zipInput->Seek((entry.lenFilename + entry.lenExtraField + entry.lenCompressed), CFile::current);
			return false;
		}

		// Filename
		if (entry.lenFilename > MAX_PATH)
			return false; // Possibly corrupt, don't allocate lots of memory
		entry.filename = new BYTE[entry.lenFilename];
		if (zipInput->Read(entry.filename, entry.lenFilename) != entry.lenFilename)
		{
			delete [] entry.filename;
			return false;
		}

		// Extra data
		if (entry.lenExtraField > 0)
		{
			entry.extraField = new BYTE[entry.lenExtraField];
			zipInput->Read(entry.extraField, entry.lenExtraField);
		}

		// Output
		writeUInt32(zipOutput, ZIP_LOCAL_HEADER_MAGIC);
		writeUInt16(zipOutput, entry.versionToExtract);
		writeUInt16(zipOutput, entry.generalPurposeFlag);
		writeUInt16(zipOutput, entry.compressionMethod);
		writeUInt16(zipOutput, entry.lastModFileTime);
		writeUInt16(zipOutput, entry.lastModFileDate);
		writeUInt32(zipOutput, entry.crc32);
		writeUInt32(zipOutput, entry.lenCompressed);
		writeUInt32(zipOutput, entry.lenUncompressed);
		writeUInt16(zipOutput, entry.lenFilename);
		writeUInt16(zipOutput, entry.lenExtraField);
		if (entry.lenFilename > 0)
			zipOutput->Write(entry.filename, entry.lenFilename);
		if (entry.lenExtraField > 0)
			zipOutput->Write(entry.extraField, entry.lenExtraField);

		// Read and write compressed data to avoid reading all into memory
		uint32 written = 0;
		BYTE buf[4096];
		uint32 lenChunk = 4096;
		while (written < entry.lenCompressed)
		{
			lenChunk  = (entry.lenCompressed - written);
			if (lenChunk > 4096)
				lenChunk = 4096;
			lenChunk = zipInput->Read(buf, lenChunk);
			if (lenChunk == 0)
				break;
			written += lenChunk;
			zipOutput->Write(buf, lenChunk);
		}
		zipOutput->Flush();

		//Central directory:
		if (centralDirectoryEntries != NULL)
		{
			ZIP_CentralDirectory *cdEntry = new ZIP_CentralDirectory;
			cdEntry->header = ZIP_CD_MAGIC;
			cdEntry->versionMadeBy = entry.versionToExtract;
			cdEntry->versionToExtract = entry.versionToExtract;
			cdEntry->generalPurposeFlag = entry.generalPurposeFlag;
			cdEntry->compressionMethod = entry.compressionMethod;
			cdEntry->lastModFileTime = entry.lastModFileTime;
			cdEntry->lastModFileDate = entry.lastModFileDate;
			cdEntry->crc32 = entry.crc32;
			cdEntry->lenCompressed = entry.lenCompressed;
			cdEntry->lenUnompressed = entry.lenUncompressed;
			cdEntry->lenFilename = entry.lenFilename;
			cdEntry->lenExtraField = entry.lenExtraField;
			cdEntry->lenComment = strlen(ZIP_COMMENT);
			cdEntry->diskNumberStart = 0;
			cdEntry->internalFileAttributes = 1;
			cdEntry->externalFileAttributes = 0x81B60020;
			cdEntry->relativeOffsetOfLocalHeader = startOffset;
			cdEntry->filename = entry.filename;
			if (entry.lenExtraField > 0)
				cdEntry->extraField = entry.extraField;
			cdEntry->comment = new BYTE[cdEntry->lenComment];
			memcpy(cdEntry->comment, ZIP_COMMENT, cdEntry->lenComment);

			centralDirectoryEntries->AddTail(cdEntry);
		}
		else
		{
			delete [] entry.filename;
			if (entry.lenExtraField > 0)
				delete [] entry.extraField;
		}
		retVal = true;
	}
	catch (CFileException* error){
		error->Delete();
	}
	catch (...){
		ASSERT(0);
	}
	return retVal;
}

void CArchiveRecovery::DeleteMemory(ThreadParam *tp)
{
	POSITION pos = tp->filled->GetHeadPosition();
	while (pos != NULL)
		delete tp->filled->GetNext(pos);
	tp->filled->RemoveAll();
	delete tp->filled;
	delete tp;
}

bool CArchiveRecovery::CopyFile(CPartFile *partFile, CTypedPtrList<CPtrList, Gap_Struct*> *filled, CString tempFileName)
{
	bool retVal = false;
	CFile *srcFile = NULL;
	try
	{
		// Get a new handle to the part file
		srcFile = partFile->m_hpartfile.Duplicate();

		// Open destination file and set length to last filled end position
		CFile destFile;
		destFile.Open(tempFileName, CFile::modeWrite | CFile::shareExclusive | CFile::modeCreate);
		Gap_Struct *fill = filled->GetTail();
		destFile.SetLength(fill->end);

		BYTE buffer[4096];
		uint32 read;
		uint32 copied;

		// Loop through filled areas and copy data
		partFile->m_bPreviewing = true;
		POSITION pos = filled->GetHeadPosition();
		while (pos != NULL)
		{
			fill = filled->GetNext(pos);
			copied = 0;
			srcFile->Seek(fill->start, CFile::begin);
			destFile.Seek(fill->start, CFile::begin);
			while ((read = srcFile->Read(buffer, 4096)) > 0)
			{
				destFile.Write(buffer, read);
				copied += read;
				// Stop when finished fill (don't worry abuot extra)
				if (fill->start + copied >= fill->end)
					break;
			}
		}
		destFile.Close();
		srcFile->Close();
		partFile->m_bPreviewing = false;

		retVal = true;
	}
	catch (CFileException* error){
		error->Delete();
	}
	catch (...){
		ASSERT(0);
	}

	if (srcFile)
		delete srcFile;

	return retVal;
}

bool CArchiveRecovery::recoverRar(CFile *rarInput, CFile *rarOutput, CTypedPtrList<CPtrList, Gap_Struct*> *filled)
{
	bool retVal = false;
	long fileCount = 0;
	try
	{
		BYTE start[] = RAR_START_OF_FILE;
		rarOutput->Write(start, sizeof(start));

		RAR_BlockFile *block;
		while ((block = scanForRarFileHeader(rarInput, (uint32)rarInput->GetLength())) != NULL)
		{
			if (IsFilled(block->offsetData, block->offsetData + block->dataLength, filled))
			{
				// Don't include directories in file count
				if ((block->HEAD_FLAGS & 0xE0) != 0xE0) 
					fileCount++;
				writeRarBlock(rarInput, rarOutput, block);
			}
			else
			{
				rarInput->Seek(block->offsetData + block->dataLength, CFile::begin);
			}
			delete [] block->FILE_NAME;
			delete block;
		}
		retVal = true;
	}
	catch (CFileException* error){
		error->Delete();
	}
	catch (...){
		ASSERT(0);
	}

	// Tell the user how many files were recovered
	CString msg;	
	if (fileCount == 1)
		msg = GetResString(IDS_RECOVER_SINGLE);
	else
		msg.Format(GetResString(IDS_RECOVER_MULTIPLE), fileCount);
	//AfxMessageBox(msg, MB_OK | MB_ICONINFORMATION);
	AddLogLine(true, _T("%s"), msg);

	return retVal;
}

bool CArchiveRecovery::IsFilled(uint32 start, uint32 end, CTypedPtrList<CPtrList, Gap_Struct*> *filled)
{
	POSITION pos = filled->GetHeadPosition();
	Gap_Struct *fill;
	while (pos != NULL)
	{
		fill = filled->GetNext(pos);
		if (fill->start > start)
			return false;
		if (fill->end >= end)
			return true;
	}
	return false;
}

// This will find the marker in the file and leave it positioned at the position to read the marker again
bool CArchiveRecovery::scanForZipMarker(CFile *input, uint32 marker, uint32 available)
{
	try
	{
		//uint32 originalOffset = input->GetPosition();
		int lenChunk = 51200; // 50k buffer 
		BYTE chunk[51200];
		BYTE *foundPos = NULL;
		int pos = 0;

		while ((available > 0) && ((lenChunk = input->Read(chunk, lenChunk)) > 0))
		{
			available -= lenChunk;
			foundPos = &chunk[0];
			// Move back one, will be incremented in loop
			foundPos--;
			while (foundPos != NULL)
			{
				// Find first matching byte
				foundPos = (BYTE*)memchr( foundPos+1, (marker & 0xFF), (lenChunk - (foundPos+1 - (&chunk[0]))) );
				if (foundPos == NULL)
					continue;

				// Test for end of buffer
				pos = foundPos - (&chunk[0]);
				if ((pos + 3) > lenChunk)
				{
					// Re-read buffer starting from found first byte position
					input->Seek(pos - lenChunk, CFile::current);
					break;
				}

				// Check for other bytes
				if (chunk[pos + 1] == ((marker >> 8) & 0xFF))
				{
					if (chunk[pos + 2] == ((marker >> 16) & 0xFF))
					{
						if (chunk[pos + 3] == ((marker >> 24) & 0xFF))
						{
							// Found it
							input->Seek(pos - lenChunk, CFile::current);
							return true;
						}
					}
				}
			}
		}
	}
	catch (CFileException* error){
		error->Delete();
	}
	catch (...){
		ASSERT(0);
	}
	return false;
}

// This will find a file block in the file and leave it positioned at the end of the filename
RAR_BlockFile *CArchiveRecovery::scanForRarFileHeader(CFile *input, uint32 available)
{
	RAR_BlockFile *retVal = NULL;
	try
	{
		int lenChunk = 51200; // 50k buffer 
		BYTE chunk[51200];
		BYTE *foundPos = NULL;
		int pos = 0;
		ULONGLONG searchOffset;
		ULONGLONG foundOffset;
		uint16 headCRC;
		BYTE checkCRC[38];
		uint16 lenFileName;
		BYTE *fileName;
		uint32 crc;

		while ((available > 0) && ((lenChunk = input->Read(chunk, lenChunk)) > 0))
		{
			available -= lenChunk;
			foundPos = &chunk[0];
			searchOffset = input->GetPosition() - lenChunk;

			// Move back one, will be incremented in loop
			foundPos--;
			while (foundPos != NULL)
			{
				// Find rar head block marker
				foundPos = (BYTE*)memchr( foundPos+1, RAR_HEAD_FILE, (lenChunk - (foundPos+1 - (&chunk[0]))) );
				if (foundPos == NULL)
					continue;

				// Move back 2 bytes to get crc and read block
				pos = (int)(foundPos - (&chunk[0]) - 2);
				input->Seek(pos - lenChunk, CFile::current);
				foundOffset = input->GetPosition();
				headCRC = readUInt16(input); // CRC of fields from HEAD_TYPE to ATTR + filename
				input->Read(&checkCRC[0], 30);
				// Also need filename for crc
				lenFileName = (((uint16)checkCRC[25]) << 8) + ((uint16)checkCRC[24]);
				fileName = new BYTE[lenFileName];
				if (checkCRC[2] & 0x1) // If HEAD_FLAG & 0x100
					input->Read(&checkCRC[30], 8);
				input->Read(fileName, lenFileName);
				crc = crc32(0, &checkCRC[0], 30);
				crc = crc32(crc, fileName, lenFileName);
				if ((crc & 0xFFFF) == headCRC)
				{
					// Found valid crc, build block and return
					// Note that it may still be invalid data, so more checks should be performed
					retVal = new RAR_BlockFile;
					retVal->HEAD_CRC		= headCRC;
					retVal->HEAD_TYPE		= 0x74;
					retVal->HEAD_FLAGS		= calcUInt16(&checkCRC[ 1]);
					retVal->HEAD_SIZE		= calcUInt16(&checkCRC[ 3]);
					retVal->PACK_SIZE		= calcUInt32(&checkCRC[ 5]);
					retVal->UNP_SIZE		= calcUInt32(&checkCRC[ 9]);
					retVal->HOST_OS			= checkCRC[13];
					retVal->FILE_CRC		= calcUInt32(&checkCRC[14]);
					retVal->FTIME			= calcUInt32(&checkCRC[18]);
					retVal->UNP_VER			= checkCRC[22];
					retVal->METHOD			= checkCRC[23];
					retVal->NAME_SIZE		= lenFileName;
					retVal->ATTR			= calcUInt32(&checkCRC[26]);
					// Optional values, present only if bit 0x100 in HEAD_FLAGS is set.
					if ((retVal->HEAD_FLAGS & 0x100) == 0x100)
					{
						retVal->HIGH_PACK_SIZE	= calcUInt32(&checkCRC[30]);
						retVal->HIGH_UNP_SIZE	= calcUInt32(&checkCRC[34]);
					}
					retVal->FILE_NAME		= fileName;
					// Run some quick checks
					if (validateRarFileBlock(retVal))
					{
						// Set some useful markers in the block
						retVal->offsetData = input->GetPosition();
						uint32 dataLength = retVal->PACK_SIZE;
						// If comment present find length
						if ((retVal->HEAD_FLAGS & 0x08) == 0x08)
						{
							// Skip start of comment block
							input->Seek(5, CFile::current);
							// Read comment length
							dataLength += readUInt16(input);
						}
						retVal->dataLength = dataLength;

						return retVal;
					}
				}
				// If not valid, return to original position, re-read and continue searching
				delete [] fileName;
				if (retVal != NULL)
					delete retVal;
				retVal = NULL;
				input->Seek(searchOffset, CFile::begin);
				input->Read(chunk, lenChunk);
			}
		}
	}
	catch (CFileException* error){
		error->Delete();
	}
	catch (...){
		ASSERT(0);
	}
	return false;
}

// This assumes that head crc has already been checked
bool CArchiveRecovery::validateRarFileBlock(RAR_BlockFile *block)
{
	if (block->HEAD_TYPE != 0x74)
		return false;
	if (block->UNP_SIZE < block->PACK_SIZE)
		return false;
	if (block->HOST_OS > 5)
		return false;
	switch (block->METHOD)
	{
		case 0x30: // storing
		case 0x31: // fastest compression
		case 0x32: // fast compression
		case 0x33: // normal compression
		case 0x34: // good compression
		case 0x35: // best compression
			break;
		default:
			return false;
	}
	if (block->NAME_SIZE > MAX_PATH)
		return false;
	// Check directory entry has no size
	if (((block->HEAD_FLAGS & 0xE0) == 0xE0) && ((block->PACK_SIZE + block->UNP_SIZE + block->FILE_CRC) > 0))
		return false;

	return true;
}

void CArchiveRecovery::writeRarBlock(CFile *input, CFile *output, RAR_BlockFile *block)
{
	ULONGLONG offsetStart = output->GetPosition();
	try
	{
		writeUInt16(output, block->HEAD_CRC);
		output->Write(&block->HEAD_TYPE, 1);
		writeUInt16(output, block->HEAD_FLAGS);
		writeUInt16(output, block->HEAD_SIZE);
		writeUInt32(output, block->PACK_SIZE);
		writeUInt32(output, block->UNP_SIZE);
		output->Write(&block->HOST_OS, 1);
		writeUInt32(output, block->FILE_CRC);
		writeUInt32(output, block->FTIME);
		output->Write(&block->UNP_VER, 1);
		output->Write(&block->METHOD, 1);
		writeUInt16(output, block->NAME_SIZE);
		writeUInt32(output, block->ATTR);
		// Optional values, present only if bit 0x100 in HEAD_FLAGS is set.
		if ((block->HEAD_FLAGS & 0x100) == 0x100)
		{
			writeUInt32(output, block->HIGH_PACK_SIZE);
			writeUInt32(output, block->HIGH_UNP_SIZE);
		}
		output->Write(block->FILE_NAME, block->NAME_SIZE);

		// Now copy compressed data from input file
		uint32 lenToCopy = block->dataLength;
		if (lenToCopy > 0)
		{
			input->Seek(block->offsetData, CFile::begin);
			uint32 written = 0;
			BYTE chunk[4096];
			uint32 lenChunk = 4096;
			while (written < lenToCopy)
			{
				lenChunk  = (lenToCopy - written);
				if (lenChunk > 4096)
					lenChunk = 4096;
				lenChunk = input->Read(chunk, lenChunk);
				if (lenChunk == 0)
					break;
				written += lenChunk;
				output->Write(chunk, lenChunk);
			}
		}
		output->Flush();
	}
	catch (CFileException* error){
		error->Delete();
		try { output->SetLength(offsetStart); } catch (...) {ASSERT(0);}
	}
	catch (...){
		ASSERT(0);
		try { output->SetLength(offsetStart); } catch (...) {ASSERT(0);}
	}
}

uint16 CArchiveRecovery::readUInt16(CFile *input)
{
	uint16 retVal = 0;
	BYTE b[2];
	if (input->Read(&b, 2) > 0)
		retVal = (b[1] << 8) + b[0];
	return retVal;
}

uint32 CArchiveRecovery::readUInt32(CFile *input)
{
	uint32 retVal = 0;
	BYTE b[4];
	if (input->Read(&b, 4) > 0)
		retVal = (b[3] << 24) + (b[2] << 16) + (b[1] << 8) + b[0];
	return retVal;
}

uint16 CArchiveRecovery::calcUInt16(BYTE *input)
{
	uint16 retVal = 0;
	try
	{
		retVal = (((uint16)input[1]) << 8) + ((uint16)input[0]);
	} catch (...) {ASSERT(0);}
	return retVal;
}

uint32 CArchiveRecovery::calcUInt32(BYTE *input)
{
	uint32 retVal = 0;
	try
	{
		retVal = (((uint32)input[3]) << 24) + (((uint32)input[2]) << 16) + (((uint32)input[1]) << 8) + ((uint32)input[0]);
	} catch (...) {ASSERT(0);}
	return retVal;
}

void CArchiveRecovery::writeUInt16(CFile *output, uint16 val)
{
	BYTE b[2];
	b[0] = (val & 0x000000ff);
	b[1] = (val & 0x0000ff00) >>  8;
	output->Write(&b, 2);
}

void CArchiveRecovery::writeUInt32(CFile *output, uint32 val)
{
	BYTE b[4];
	b[0] = (val & 0x000000ff);
	b[1] = (val & 0x0000ff00) >>  8;
	b[2] = (val & 0x00ff0000) >> 16;
	b[3] = (val & 0xff000000) >> 24;
	output->Write(&b, 4);
}