fixed size chunking for encrypted files (#410)

- Improvement: Use fixed size block chunking for know encrypted/compressed file types
- Improvement: Skip trying to compress chunks that are sourced from files that are known to be encrypted/compressed
- Improvement: Add global open file cache for written files increasing throughput during download by reducing overhead of open/close of file by 80%

1 files changed, 4 insertions, 0 deletions

diff --git a/src/zenutil/chunkedcontent.cpp b/src/zenutil/chunkedcontent.cpp
index ae129324e..4bec4901a 100644
--- a/src/zenutil/chunkedcontent.cpp
+++ b/src/zenutil/chunkedcontent.cpp
@@ -891,8 +891,12 @@ BuildChunkedContentLookup(const ChunkedFolderContent& Content)
 	}
 
 	Result.SequenceIndexFirstPathIndex.resize(Content.ChunkedContent.SequenceRawHashes.size(), (uint32_t)-1);
+	Result.PathExtensionHash.resize(Content.Paths.size());
 	for (uint32_t PathIndex = 0; PathIndex < Content.Paths.size(); PathIndex++)
 	{
+		std::string LowercaseExtension = Content.Paths[PathIndex].extension().string();
+		std::transform(LowercaseExtension.begin(), LowercaseExtension.end(), LowercaseExtension.begin(), ::tolower);
+		Result.PathExtensionHash[PathIndex] = HashStringDjb2(LowercaseExtension);
 		if (Content.RawSizes[PathIndex] > 0)
 		{
 			const IoHash& RawHash		  = Content.RawHashes[PathIndex];