added support for delta-encoding of main manifest

reduces size of test data to less than half of the non-delta version

after compression the delta version is less than 20% of the original representation

1 files changed, 33 insertions, 0 deletions

diff --git a/src/zenutil/include/zenutil/chunkedcontent.h b/src/zenutil/include/zenutil/chunkedcontent.h
index 309341550..533ec431f 100644
--- a/src/zenutil/include/zenutil/chunkedcontent.h
+++ b/src/zenutil/include/zenutil/chunkedcontent.h
@@ -195,6 +195,25 @@ namespace compactbinary_helpers {
 		WriteArray(std::span<const Type>(Values), ArrayName, Output);
 	}
 
+	inline void WriteDeltaArray(std::span<const uint32_t> Values, std::string_view ArrayName, CbWriter& Output)
+	{
+		Output.BeginArray(ArrayName);
+		uint32_t PreviousValue = 0;
+		for (const uint32_t Value : Values)
+		{
+			int64_t	 Delta		 = int64_t(Value) - PreviousValue;
+			uint64_t DeltaZigZag = (Delta >= 0) ? (Delta << 1) : (((-Delta - 1) << 1) | 1);
+			Output.AddInteger(DeltaZigZag);
+			PreviousValue = Value;
+		}
+		Output.EndArray();
+	}
+
+	inline void WriteDeltaArray(const std::vector<uint32_t>& Values, std::string_view ArrayName, CbWriter& Output)
+	{
+		WriteDeltaArray(std::span<const uint32_t>(Values), ArrayName, Output);
+	}
+
 	template<>
 	inline void WriteArray(std::span<const std::filesystem::path> Values, std::string_view ArrayName, CbWriter& Output)
 	{
@@ -237,6 +256,20 @@ namespace compactbinary_helpers {
 		}
 	}
 
+	inline void ReadDeltaArray(std::string_view ArrayName, CbObjectView Input, std::vector<uint32_t>& Result)
+	{
+		CbArrayView Array = Input[ArrayName].AsArrayView();
+		Result.reserve(Array.Num());
+		uint32_t PreviousValue = 0;
+		for (CbFieldView ItemView : Array)
+		{
+			uint64_t	  DeltaZigZag = ItemView.AsUInt64();
+			const int64_t Delta		  = (DeltaZigZag & 1) ? -int64_t((DeltaZigZag >> 1) + 1) : int64_t(DeltaZigZag >> 1);
+			PreviousValue			  = uint32_t(PreviousValue + Delta);
+			Result.push_back(PreviousValue);
+		}
+	}
+
 	inline void ReadArray(std::string_view ArrayName, CbObjectView Input, std::vector<uint64_t>& Result)
 	{
 		CbArrayView Array = Input[ArrayName].AsArrayView();