unsafe void ReadHeap(IOFileStream source)
{
source.Position = 0;
source.Read(_heapBytes, 0, sizeof(DeviceHeap));
fixed(byte *src = _heapBytes)
_heap = Marshal.PtrToStructure <DeviceHeap>(new IntPtr(src));
}
unsafe void ReadHeapOrCreate(IOFileStream source, int chunkSize, int blockSize)
{
if (source.Length != 0)
{
ReadHeap(source);
return;
}
// fix up chunkSize to include fallocChunkHeader
chunkSize = (chunkSize + sizeof(ChunkHeader) + 15) & ~15;
// fix up blockSize to be a multiple of chunkSize
if (blockSize == 0 || (blockSize % chunkSize) != 0)
{
blockSize += chunkSize - (blockSize % chunkSize);
}
var chunksLength = blockSize;
var chunks = blockSize / chunkSize;
if (chunks == 0)
{
throw new InvalidOperationException();
}
// fix up blockSize to include DeviceHeap + freechunks
var chunkRefsLength = chunks * sizeof(ChunkRef);
_blockSize = (blockSize + chunkRefsLength + sizeof(DeviceHeap) + 15) & ~15;
// transfer to heap
var offset = sizeof(DeviceHeap);
_heap = new DeviceHeap
{
chunkSize = chunkSize,
chunksLength = chunksLength,
chunkRefsLength = chunkRefsLength,
chunkRefs = offset,
freeChunkPtr = offset,
retnChunkPtr = offset,
chunks = offset + chunkRefsLength,
};
WriteHeap(source);
}