1 files changed, 282 insertions, 0 deletions
diff --git a/src/zenutil/cache/cachepolicy.cpp b/src/zenutil/cache/cachepolicy.cpp
new file mode 100644
index 000000000..3bca363bb
--- /dev/null
+++ b/src/zenutil/cache/cachepolicy.cpp
@@ -0,0 +1,282 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zenutil/cache/cachepolicy.h>
+
+#include <zencore/compactbinary.h>
+#include <zencore/compactbinarybuilder.h>
+#include <zencore/enumflags.h>
+#include <zencore/string.h>
+
+#include <algorithm>
+#include <unordered_map>
+
+namespace zen::Private {
+class CacheRecordPolicyShared;
+}
+
+namespace zen {
+
+using namespace std::literals;
+
+namespace DerivedData::Private {
+
+	constinit char CachePolicyDelimiter = ',';
+
+	struct CachePolicyToTextData
+	{
+		CachePolicy		 Policy;
+		std::string_view Text;
+	};
+
+	constinit CachePolicyToTextData CachePolicyToText[]{
+		// Flags with multiple bits are ordered by bit count to minimize token count in the text format.
+		{CachePolicy::Default, "Default"sv},
+		{CachePolicy::Remote, "Remote"sv},
+		{CachePolicy::Local, "Local"sv},
+		{CachePolicy::Store, "Store"sv},
+		{CachePolicy::Query, "Query"sv},
+		// Flags with only one bit can be in any order. Match the order in CachePolicy.
+		{CachePolicy::QueryLocal, "QueryLocal"sv},
+		{CachePolicy::QueryRemote, "QueryRemote"sv},
+		{CachePolicy::StoreLocal, "StoreLocal"sv},
+		{CachePolicy::StoreRemote, "StoreRemote"sv},
+		{CachePolicy::SkipMeta, "SkipMeta"sv},
+		{CachePolicy::SkipData, "SkipData"sv},
+		{CachePolicy::PartialRecord, "PartialRecord"sv},
+		{CachePolicy::KeepAlive, "KeepAlive"sv},
+		// None must be last because it matches every policy.
+		{CachePolicy::None, "None"sv},
+	};
+
+	constinit CachePolicy CachePolicyKnownFlags =
+		CachePolicy::Default | CachePolicy::SkipMeta | CachePolicy::SkipData | CachePolicy::PartialRecord | CachePolicy::KeepAlive;
+
+	StringBuilderBase& CachePolicyToString(StringBuilderBase& Builder, CachePolicy Policy)
+	{
+		// Mask out unknown flags. None will be written if no flags are known.
+		Policy &= CachePolicyKnownFlags;
+		for (const CachePolicyToTextData& Pair : CachePolicyToText)
+		{
+			if (EnumHasAllFlags(Policy, Pair.Policy))
+			{
+				EnumRemoveFlags(Policy, Pair.Policy);
+				Builder << Pair.Text << CachePolicyDelimiter;
+				if (Policy == CachePolicy::None)
+				{
+					break;
+				}
+			}
+		}
+		Builder.RemoveSuffix(1);
+		return Builder;
+	}
+
+	CachePolicy ParseCachePolicy(const std::string_view Text)
+	{
+		ZEN_ASSERT(!Text.empty());	// ParseCachePolicy requires a non-empty string
+		CachePolicy Policy = CachePolicy::None;
+		ForEachStrTok(Text, CachePolicyDelimiter, [&Policy, Index = int32_t(0)](const std::string_view& Token) mutable {
+			const int32_t EndIndex = Index;
+			for (; size_t(Index) < sizeof(CachePolicyToText) / sizeof(CachePolicyToText[0]); ++Index)
+			{
+				if (CachePolicyToText[Index].Text == Token)
+				{
+					Policy |= CachePolicyToText[Index].Policy;
+					++Index;
+					return true;
+				}
+			}
+			for (Index = 0; Index < EndIndex; ++Index)
+			{
+				if (CachePolicyToText[Index].Text == Token)
+				{
+					Policy |= CachePolicyToText[Index].Policy;
+					++Index;
+					return true;
+				}
+			}
+			return true;
+		});
+		return Policy;
+	}
+
+}  // namespace DerivedData::Private
+
+StringBuilderBase&
+operator<<(StringBuilderBase& Builder, CachePolicy Policy)
+{
+	return DerivedData::Private::CachePolicyToString(Builder, Policy);
+}
+
+CachePolicy
+ParseCachePolicy(std::string_view Text)
+{
+	return DerivedData::Private::ParseCachePolicy(Text);
+}
+
+CachePolicy
+ConvertToUpstream(CachePolicy Policy)
+{
+	// Set Local flags equal to downstream's Remote flags.
+	// Delete Skip flags if StoreLocal is true, otherwise use the downstream value.
+	// Use the downstream value for all other flags.
+
+	CachePolicy UpstreamPolicy = CachePolicy::None;
+
+	if (EnumHasAllFlags(Policy, CachePolicy::QueryRemote))
+	{
+		UpstreamPolicy |= CachePolicy::QueryLocal;
+	}
+
+	if (EnumHasAllFlags(Policy, CachePolicy::StoreRemote))
+	{
+		UpstreamPolicy |= CachePolicy::StoreLocal;
+	}
+
+	if (!EnumHasAllFlags(Policy, CachePolicy::StoreLocal))
+	{
+		UpstreamPolicy |= (Policy & (CachePolicy::SkipData | CachePolicy::SkipMeta));
+	}
+
+	UpstreamPolicy |= Policy & ~(CachePolicy::Local | CachePolicy::SkipData | CachePolicy::SkipMeta);
+
+	return UpstreamPolicy;
+}
+
+class Private::CacheRecordPolicyShared final : public Private::ICacheRecordPolicyShared
+{
+public:
+	inline void AddValuePolicy(const CacheValuePolicy& Value) final
+	{
+		ZEN_ASSERT(Value.Id);  // Failed to add value policy because the ID is null.
+		const auto Insert =
+			std::lower_bound(Values.begin(), Values.end(), Value, [](const CacheValuePolicy& Existing, const CacheValuePolicy& New) {
+				return Existing.Id < New.Id;
+			});
+		ZEN_ASSERT(
+			!(Insert < Values.end() &&
+			  Insert->Id == Value.Id));	 // Failed to add value policy with ID %s because it has an existing value policy with that ID. ")
+		Values.insert(Insert, Value);
+	}
+
+	inline std::span<const CacheValuePolicy> GetValuePolicies() const final { return Values; }
+
+private:
+	std::vector<CacheValuePolicy> Values;
+};
+
+CachePolicy
+CacheRecordPolicy::GetValuePolicy(const Oid& Id) const
+{
+	if (Shared)
+	{
+		const std::span<const CacheValuePolicy> Values = Shared->GetValuePolicies();
+		const auto								Iter =
+			std::lower_bound(Values.begin(), Values.end(), Id, [](const CacheValuePolicy& A, const Oid& B) { return A.Id < B; });
+		if (Iter != Values.end() && Iter->Id == Id)
+		{
+			return Iter->Policy;
+		}
+	}
+	return DefaultValuePolicy;
+}
+
+void
+CacheRecordPolicy::Save(CbWriter& Writer) const
+{
+	Writer.BeginObject();
+	// The RecordPolicy is calculated from the ValuePolicies and does not need to be saved separately.
+	Writer.AddString("BasePolicy"sv, WriteToString<128>(GetBasePolicy()));
+	if (!IsUniform())
+	{
+		Writer.BeginArray("ValuePolicies"sv);
+		for (const CacheValuePolicy& Value : GetValuePolicies())
+		{
+			Writer.BeginObject();
+			Writer.AddObjectId("Id"sv, Value.Id);
+			Writer.AddString("Policy"sv, WriteToString<128>(Value.Policy));
+			Writer.EndObject();
+		}
+		Writer.EndArray();
+	}
+	Writer.EndObject();
+}
+
+OptionalCacheRecordPolicy
+CacheRecordPolicy::Load(const CbObjectView Object)
+{
+	std::string_view BasePolicyText = Object["BasePolicy"sv].AsString();
+	if (BasePolicyText.empty())
+	{
+		return {};
+	}
+
+	CacheRecordPolicyBuilder Builder(ParseCachePolicy(BasePolicyText));
+	for (CbFieldView ValueField : Object["ValuePolicies"sv])
+	{
+		const CbObjectView	   Value	  = ValueField.AsObjectView();
+		const Oid			   Id		  = Value["Id"sv].AsObjectId();
+		const std::string_view PolicyText = Value["Policy"sv].AsString();
+		if (!Id || PolicyText.empty())
+		{
+			return {};
+		}
+		CachePolicy Policy = ParseCachePolicy(PolicyText);
+		if (EnumHasAnyFlags(Policy, ~CacheValuePolicy::PolicyMask))
+		{
+			return {};
+		}
+		Builder.AddValuePolicy(Id, Policy);
+	}
+
+	return Builder.Build();
+}
+
+CacheRecordPolicy
+CacheRecordPolicy::ConvertToUpstream() const
+{
+	CacheRecordPolicyBuilder Builder(zen::ConvertToUpstream(GetBasePolicy()));
+	for (const CacheValuePolicy& ValuePolicy : GetValuePolicies())
+	{
+		Builder.AddValuePolicy(ValuePolicy.Id, zen::ConvertToUpstream(ValuePolicy.Policy));
+	}
+	return Builder.Build();
+}
+
+void
+CacheRecordPolicyBuilder::AddValuePolicy(const CacheValuePolicy& Value)
+{
+	ZEN_ASSERT(!EnumHasAnyFlags(Value.Policy,
+								~Value.PolicyMask));  // Value policy contains flags that only make sense on the record policy. Policy: %s
+	if (Value.Policy == (BasePolicy & Value.PolicyMask))
+	{
+		return;
+	}
+	if (!Shared)
+	{
+		Shared = new Private::CacheRecordPolicyShared;
+	}
+	Shared->AddValuePolicy(Value);
+}
+
+CacheRecordPolicy
+CacheRecordPolicyBuilder::Build()
+{
+	CacheRecordPolicy Policy(BasePolicy);
+	if (Shared)
+	{
+		const auto Add = [](const CachePolicy A, const CachePolicy B) {
+			return ((A | B) & ~CachePolicy::SkipData) | ((A & B) & CachePolicy::SkipData);
+		};
+		const std::span<const CacheValuePolicy> Values = Shared->GetValuePolicies();
+		Policy.RecordPolicy							   = BasePolicy;
+		for (const CacheValuePolicy& ValuePolicy : Values)
+		{
+			Policy.RecordPolicy = Add(Policy.RecordPolicy, ValuePolicy.Policy);
+		}
+		Policy.Shared = std::move(Shared);
+	}
+	return Policy;
+}
+
+}  // namespace zen