public bool VirtualToLogicalDriveOffset(ulong virtualOffset, out ulong logicalOffset)
{
logicalOffset = 0;
if (virtualOffset >= Header.DriveSize)
{
throw new InvalidOperationException(
$"Virtual offset 0x{virtualOffset:X} is outside drivedata length 0x{Header.DriveSize:X}");
}
if (Header.Type > XvdType.Dynamic)
{
throw new NotSupportedException($"Xvd type {Header.Type} is unhandled");
}
if (Header.Type == XvdType.Dynamic)
{
var dataStartOffset = virtualOffset + XvdMath.PageNumberToOffset(Header.NumberOfMetadataPages);
var pageNumber = XvdMath.OffsetToPageNumber(dataStartOffset);
var inBlockOffset = XvdMath.InBlockOffset(dataStartOffset);
var firstDynamicPage = XvdMath.QueryFirstDynamicPage(Header.NumberOfMetadataPages);
if (pageNumber >= firstDynamicPage)
{
var firstDynamicPageBytes = XvdMath.PageNumberToOffset(firstDynamicPage);
var blockNumber = XvdMath.OffsetToBlockNumber(dataStartOffset - firstDynamicPageBytes);
ulong allocatedBlock = ReadBat(blockNumber);
if (allocatedBlock == INVALID_SECTOR)
{
return(false);
}
dataStartOffset = XvdMath.PageNumberToOffset(allocatedBlock) + inBlockOffset;
pageNumber = XvdMath.OffsetToPageNumber(dataStartOffset);
}
var dataBackingBlockNum = XvdMath.ComputeDataBackingPageNumber(Header.Type,
HashTreeLevels,
HashTreePageCount,
pageNumber);
logicalOffset = XvdMath.PageNumberToOffset(dataBackingBlockNum);
logicalOffset += XvdMath.InPageOffset(dataStartOffset);
logicalOffset += XvdMath.PageNumberToOffset(Header.EmbeddedXvdPageCount);
logicalOffset += Header.MutableDataLength;
logicalOffset += XVD_HEADER_INCL_SIGNATURE_SIZE;
logicalOffset += PAGE_SIZE;
}
else
{ // Xvd type fixed
logicalOffset = virtualOffset;
logicalOffset += XvdMath.PageNumberToOffset(Header.EmbeddedXvdPageCount);
logicalOffset += Header.MutableDataLength;
logicalOffset += XvdMath.PageNumberToOffset(Header.NumberOfMetadataPages);
logicalOffset += XVD_HEADER_INCL_SIGNATURE_SIZE;
logicalOffset += PAGE_SIZE;
}
return(true);
}
byte[] ReadDynamic(int count)
{
int positionInBuffer = 0;
int bytesRemaining = count;
byte[] destBuffer = new byte[count];
while (positionInBuffer < count)
{
byte[] data = new byte[0];
if (Position < StaticDataLength)
{
// Read a chunk from non-dynamic area, next iteration will read dynamic data
int maxReadLength = (int)(StaticDataLength - Position);
int length = bytesRemaining > maxReadLength ? maxReadLength : bytesRemaining;
data = InternalRead(length);
}
else
{
// Lookup block allocation table for real data offset
var targetVirtualOffset = (ulong)(Position - StaticDataLength);
ulong blockNumber = XvdMath.OffsetToBlockNumber(targetVirtualOffset);
long inBlockOffset = (long)XvdMath.InBlockOffset(targetVirtualOffset);
int maxReadLength = (int)(XvdFile.BLOCK_SIZE - inBlockOffset);
int length = bytesRemaining > maxReadLength ? maxReadLength : bytesRemaining;
var targetPage = _xvdFile.ReadBat(blockNumber);
if (targetPage == XvdFile.INVALID_SECTOR)
{
data = new byte[length];
// Advance stream position cause we are not actually reading data
Position += length;
}
else
{
long targetPhysicalOffset = DynamicBaseOffset
+ (long)XvdMath.PageNumberToOffset(targetPage)
+ inBlockOffset;
data = InternalReadAbsolute(targetPhysicalOffset, length);
}
}
Array.Copy(data, 0, destBuffer, positionInBuffer, data.Length);
positionInBuffer += data.Length;
bytesRemaining -= data.Length;
}
return(destBuffer);
}
