public DecompressedLeafPage DecompressPage(TreePage p, DecompressionUsage usage = DecompressionUsage.Read, bool skipCache = false)
{
var input = new DecompressionInput(p.CompressionHeader, p);
DecompressedLeafPage decompressedPage;
DecompressedLeafPage cached = null;
if (skipCache == false && DecompressionsCache.TryGet(p.PageNumber, usage, out cached))
{
decompressedPage = ReuseCachedPage(cached, usage, ref input);
if (usage == DecompressionUsage.Read)
{
return(decompressedPage);
}
}
else
{
decompressedPage = DecompressFromBuffer(usage, ref input);
}
Debug.Assert(decompressedPage.NumberOfEntries > 0);
try
{
if (p.NumberOfEntries == 0)
{
return(decompressedPage);
}
HandleUncompressedNodes(decompressedPage, p, usage);
return(decompressedPage);
}
finally
{
decompressedPage.DebugValidate(this, State.RootPageNumber);
if (skipCache == false && decompressedPage != cached)
{
DecompressionsCache.Invalidate(p.PageNumber, usage);
DecompressionsCache.Add(decompressedPage);
}
}
}
private DecompressedLeafPage DecompressFromBuffer(DecompressionUsage usage, ref DecompressionInput input)
{
var result = _llt.Environment.DecompressionBuffers.GetPage(_llt, input.DecompressedPageSize, usage, input.Page);
var decompressedNodesOffset = (ushort)(result.PageSize - input.DecompressedSize);
LZ4.Decode64LongBuffers(
input.Data,
input.CompressedSize,
result.Base + decompressedNodesOffset,
input.DecompressedSize, true);
result.Lower += input.KeysOffsetsSize;
result.Upper = decompressedNodesOffset;
for (var i = 0; i < input.NumberOfEntries; i++)
{
result.KeysOffsets[i] = (ushort)(input.KeysOffsets[i] + result.Upper);
}
return(result);
}
private DecompressedLeafPage ReuseCachedPage(DecompressedLeafPage cached, DecompressionUsage usage, ref DecompressionInput input)
{
DecompressedLeafPage result;
var sizeDiff = input.DecompressedPageSize - cached.PageSize;
if (sizeDiff > 0)
{
result = _llt.Environment.DecompressionBuffers.GetPage(_llt, input.DecompressedPageSize, usage, input.Page);
Memory.Copy(result.Base, cached.Base, cached.Lower);
Memory.Copy(result.Base + cached.Upper + sizeDiff,
cached.Base + cached.Upper,
cached.PageSize - cached.Upper);
result.Upper += (ushort)sizeDiff;
for (var i = 0; i < result.NumberOfEntries; i++)
{
result.KeysOffsets[i] += (ushort)sizeDiff;
}
}
else
{
result = cached;
}
return(result);
}
