private static void AllocateUncompressedBuffer(CompressedWorkItem compressedWorkItem)
{
Debug.Assert(compressedWorkItem.UncompressedSize != 0);
// remember, our goal is to reduce the # of allocations done for compressedWorkItem.UncompressedBuffer
// CompressedWorkItems are cached as a pool, and if our buffer size is large enough, we can
// avoid a re-allocation.
if (compressedWorkItem.UncompressedBuffer != null &&
compressedWorkItem.UncompressedBuffer.Length >= compressedWorkItem.UncompressedSize)
{
return;
}
// go a little more than we need to avoid
// re-use needing to re-allocate.
// works because our uncompressedsize shouldn't change much
const float unscientificMultiplierGuess = 1.2f;
var size = (int)(compressedWorkItem.UncompressedSize * unscientificMultiplierGuess);
compressedWorkItem.UncompressedBuffer = new byte[size];
}
public void FreeCompressedWorkItem(ref CompressedWorkItem compressedItem)
{
// don't kill the big buffers. main point of this pool is to hopefully re-use them later.
if (compressedItem == null)
{
return;
}
// keep the capacity, but kill the contents.
// also, go a little overkill and kill the references to WorkItem list heads inside the List.
if (compressedItem.ListHeads != null)
{
for (var i = 0; i < compressedItem.ListHeads.Count; ++i)
{
compressedItem.ListHeads[0] = null;
}
compressedItem.ListHeads.Clear();
}
poolCompressedWorkItems?.Return(ref compressedItem);
}
public void DecompressWorkItem(CompressedWorkItem compressedWorkItem)
{
Debug.Assert(!compressedWorkItem.WasDecompressed);
AllocateUncompressedBuffer(compressedWorkItem);
var decompressedLength = 0;
using (var memory = new MemoryStream(compressedWorkItem.CompressedBuffer))
{
using var inflater = new InflaterInputStream(memory);
decompressedLength = inflater.Read(compressedWorkItem.UncompressedBuffer, 0,
compressedWorkItem.UncompressedSize);
}
compressedWorkItem.WasDecompressed = true;
if (decompressedLength != compressedWorkItem.UncompressedSize)
{
throw new InvalidDataException("incorrect decompressed data size");
}
// after this function, compressedWorkItem.CompressedBuffer is no longer needed.
// but, leave it allocated so future runs can re-use that buffer.
}