param block cleanup

added Flag as value type
moved Batch to BatchBlock
renamed Choice to ChoiceBlock
made merging of parameters for ValueParams consistent (fillFrom and overwriteFrom are inverses of each other now)
made iteration over Multiple<T> type params easier
initial schema param blocks

1 files changed, 203 insertions, 249 deletions

diff --git a/indra/llxuixml/llinitparam.h b/indra/llxuixml/llinitparam.h
index 69dcd474f7..9a6ded47ff 100644
--- a/indra/llxuixml/llinitparam.h
+++ b/indra/llxuixml/llinitparam.h
@@ -38,6 +38,9 @@
 
 namespace LLInitParam
 {
+	// used to indicate no matching value to a given name when parsing
+	struct Flag{};
+
 	template<typename T> const T& defaultValue() { static T value; return value; }
 
 	template <typename T, bool IS_BOOST_FUNCTION = boost::is_convertible<T, boost::function_base>::value >
@@ -65,6 +68,12 @@ namespace LLInitParam
 		static bool equals(const LLSD &a, const LLSD &b) { return false; }
 	};
 
+	template<>
+	struct ParamCompare<Flag, false>
+	{
+		static bool equals(const Flag& a, const Flag& b) { return false; }
+	};
+
 	// helper functions and classes
 	typedef ptrdiff_t param_handle_t;
 
@@ -275,9 +284,6 @@ namespace LLInitParam
 		static S32					sNextParseGeneration;
 	};
 
-	// used to indicate no matching value to a given name when parsing
-	struct NoParamValue{};
-
 	class BaseBlock;
 
 	class Param
@@ -385,36 +391,36 @@ namespace LLInitParam
 		// "Multiple" constraint types, put here in root class to avoid ambiguity during use
 		struct AnyAmount
 		{
-			static U32 minCount() { return 0; }
-			static U32 maxCount() { return U32_MAX; }
+			enum { minCount = 0 };
+			enum { maxCount = U32_MAX };
 		};
 
 		template<U32 MIN_AMOUNT>
 		struct AtLeast
 		{
-			static U32 minCount() { return MIN_AMOUNT; }
-			static U32 maxCount() { return U32_MAX; }
+			enum { minCount = MIN_AMOUNT };
+			enum { maxCount = U32_MAX };
 		};
 
 		template<U32 MAX_AMOUNT>
 		struct AtMost
 		{
-			static U32 minCount() { return 0; }
-			static U32 maxCount() { return MAX_AMOUNT; }
+			enum { minCount = 0 };
+			enum { maxCount = MAX_AMOUNT };
 		};
 
 		template<U32 MIN_AMOUNT, U32 MAX_AMOUNT>
 		struct Between
 		{
-			static U32 minCount() { return MIN_AMOUNT; }
-			static U32 maxCount() { return MAX_AMOUNT; }
+			enum { minCount = MIN_AMOUNT };
+			enum { maxCount = MAX_AMOUNT };
 		};
 
 		template<U32 EXACT_COUNT>
 		struct Exactly
 		{
-			static U32 minCount() { return EXACT_COUNT; }
-			static U32 maxCount() { return EXACT_COUNT; }
+			enum { minCount = EXACT_COUNT };
+			enum { maxCount = EXACT_COUNT };
 		};
 
 		// this typedef identifies derived classes as being blocks
@@ -477,9 +483,9 @@ namespace LLInitParam
 		void init(BlockDescriptor& descriptor, BlockDescriptor& base_descriptor, size_t block_size);
 
 
-		bool mergeBlockParam(bool param_provided, BlockDescriptor& block_data, const BaseBlock& other, bool overwrite)
+		bool mergeBlockParam(bool source_provided, bool dst_provided, BlockDescriptor& block_data, const BaseBlock& source, bool overwrite)
 		{
-			return mergeBlock(block_data, other, overwrite);
+			return mergeBlock(block_data, source, overwrite);
 		}
 		// take all provided params from other and apply to self
 		bool mergeBlock(BlockDescriptor& block_data, const BaseBlock& other, bool overwrite);
@@ -497,92 +503,6 @@ namespace LLInitParam
 		const std::string& getParamName(const BlockDescriptor& block_data, const Param* paramp) const;
 	};
 
-	class BaseBlockWithFlags : public BaseBlock
-	{
-	public:
-		class FlagBase : public Param
-		{
-		public:
-			typedef FlagBase self_t;
-
-			FlagBase(const char* name, BaseBlock* enclosing_block) : Param(enclosing_block) 
-			{
-				if (LL_UNLIKELY(enclosing_block->mostDerivedBlockDescriptor().mInitializationState == BlockDescriptor::INITIALIZING))
-				{
-					ParamDescriptorPtr param_descriptor = ParamDescriptorPtr(new ParamDescriptor(
-						enclosing_block->getHandleFromParam(this),
-						&mergeWith,
-						&deserializeParam,
-						&serializeParam,
-						NULL,
-						&inspectParam,
-						0, 1));
-					BaseBlock::addParam(enclosing_block->mostDerivedBlockDescriptor(), param_descriptor, name);
-				}
-			}
-
-			bool isProvided() const { return anyProvided(); }
-
-		private:
-			static bool mergeWith(Param& dst, const Param& src, bool overwrite)
-			{
-				const self_t& src_typed_param = static_cast<const self_t&>(src);
-				self_t& dst_typed_param = static_cast<self_t&>(dst);
-
-				if (src_typed_param.isProvided()
-					&& (overwrite || !dst_typed_param.isProvided()))
-				{
-					dst.setProvided(true);
-					return true;
-				}
-				return false;
-			}
-
-			static bool deserializeParam(Param& param, Parser& parser, const Parser::name_stack_range_t& name_stack, S32 generation)
-			{
-				self_t& typed_param = static_cast<self_t&>(param);
-
-				// no further names in stack, parse value now
-				if (name_stack.first == name_stack.second)
-				{
-					typed_param.setProvided(true);
-					typed_param.enclosingBlock().paramChanged(param, true);
-					return true;
-				}
-
-				return false;
-			}
-
-			static void serializeParam(const Param& param, Parser& parser, Parser::name_stack_t& name_stack, const Param* diff_param)
-			{
-				const self_t& typed_param = static_cast<const self_t&>(param);
-				const self_t* typed_diff_param = static_cast<const self_t*>(diff_param);
-
-				if (!typed_param.isProvided()) return;
-
-				if (!name_stack.empty())
-				{
-					name_stack.back().second = parser.newParseGeneration();
-				}
-
-				// then try to serialize value directly
-				if (!typed_diff_param || !typed_diff_param->isProvided())
-				{
-					if (!parser.writeValue(NoParamValue(), name_stack)) 
-					{
-						return;
-					}
-				}
-			}
-
-			static void inspectParam(const Param& param, Parser& parser, Parser::name_stack_t& name_stack, S32 min_count, S32 max_count)
-			{
-				// tell parser about our actual type
-				parser.inspectValue<NoParamValue>(name_stack, min_count, max_count, NULL);
-			}
-		};
-	};
-
 	// these templates allow us to distinguish between template parameters
 	// that derive from BaseBlock and those that don't
 	template<typename T, typename Void = void>
@@ -604,7 +524,7 @@ namespace LLInitParam
 		typedef const T&							value_assignment_t;
 
 		ParamValue(): mValue() {}
-		ParamValue(const T& other) : mValue(other) {}
+		ParamValue(value_assignment_t other) : mValue(other) {}
 
 		void setValue(value_assignment_t val)
 		{
@@ -621,6 +541,17 @@ namespace LLInitParam
 			return mValue;
 		}
 
+		operator value_assignment_t() const
+		{
+			return mValue;
+		}
+
+		value_assignment_t operator()() const
+		{
+			return mValue;
+		}
+
+
 	private:
 		T mValue;
 	};
@@ -644,7 +575,7 @@ namespace LLInitParam
 			mValidated(false)
 		{}
 
-		ParamValue(const T& other)
+		ParamValue(value_assignment_t other)
 		:	T(other),
 			mKeyVersion(0),
 			mValidatedVersion(-1),
@@ -666,6 +597,16 @@ namespace LLInitParam
 		{
 			return *this;
 		}
+
+		operator value_assignment_t() const
+		{
+			return *this;
+		}
+		
+		value_assignment_t operator()() const
+		{
+			return *this;
+		}
 	};
 
 	template<typename T, typename NAME_VALUE_LOOKUP = TypeValues<T> >
@@ -801,11 +742,6 @@ namespace LLInitParam
 			Param::enclosingBlock().paramChanged(*this, flag_as_provided);
 		}
 
-		// implicit conversion
-		operator value_assignment_t() const { return param_value_t::getValue(); } 
-		// explicit conversion
-		value_assignment_t operator()() const { return param_value_t::getValue(); } 
-
 	protected:
 
 		static bool mergeWith(Param& dst, const Param& src, bool overwrite)
@@ -958,11 +894,6 @@ namespace LLInitParam
 			}
 		}
 
-		// implicit conversion
-		operator value_assignment_t() const { return param_value_t::getValue(); } 
-		// explicit conversion
-		value_assignment_t operator()() const { return param_value_t::getValue(); } 
-
 	protected:
 
 		static bool mergeWith(Param& dst, const Param& src, bool overwrite)
@@ -972,8 +903,7 @@ namespace LLInitParam
 
 			if (src_typed_param.anyProvided())
 			{
-				bool param_provided = src_typed_param.isProvided() && (overwrite || !dst_typed_param.isProvided());
-				if (dst_typed_param.mergeBlockParam(param_provided, param_value_t::selfBlockDescriptor(), src_typed_param, overwrite))
+				if (dst_typed_param.mergeBlockParam(src_typed_param.isProvided(), dst_typed_param.isProvided(), param_value_t::selfBlockDescriptor(), src_typed_param, overwrite))
 				{
 					dst_typed_param.clearValueName();
 					dst_typed_param.setProvided(true);
@@ -992,8 +922,8 @@ namespace LLInitParam
 	{
 	public:
 		typedef TypedParam<VALUE_TYPE, NAME_VALUE_LOOKUP, true, false>		self_t;
-		typedef ParamValue<VALUE_TYPE, NAME_VALUE_LOOKUP>			param_value_t;
-		typedef typename std::vector<param_value_t>							container_t;
+		typedef ParamValue<VALUE_TYPE, NAME_VALUE_LOOKUP>					param_value_t;
+		typedef typename std::vector<param_value_t>					container_t;
 		typedef const container_t&											value_assignment_t;
 
 		typedef VALUE_TYPE													value_t;
@@ -1118,6 +1048,8 @@ namespace LLInitParam
 
 		// implicit conversion
 		operator value_assignment_t() const { return mValues; } 
+		// explicit conversion		
+		value_assignment_t operator()() const { return mValues; }
 
 		typedef typename container_t::iterator iterator;
 		typedef typename container_t::const_iterator const_iterator;
@@ -1169,7 +1101,7 @@ namespace LLInitParam
 	public:
 		typedef TypedParam<VALUE_TYPE, NAME_VALUE_LOOKUP, true, true>	self_t;
 		typedef ParamValue<VALUE_TYPE, NAME_VALUE_LOOKUP>				param_value_t;
-		typedef typename std::vector<param_value_t>						container_t;
+		typedef typename std::vector<param_value_t>				container_t;
 		typedef const container_t&										value_assignment_t;
 		typedef VALUE_TYPE												value_t;
 		typedef NAME_VALUE_LOOKUP										name_value_lookup_t;
@@ -1308,6 +1240,8 @@ namespace LLInitParam
 
 		// implicit conversion
 		operator value_assignment_t() const { return mValues; } 
+		// explicit conversion
+		value_assignment_t operator()() const { return mValues; }
 
 		typedef typename container_t::iterator iterator;
 		typedef typename container_t::const_iterator const_iterator;
@@ -1363,10 +1297,10 @@ namespace LLInitParam
 	};
 
 	template <typename DERIVED_BLOCK>
-	class Choice : public BaseBlock
+	class ChoiceBlock : public BaseBlock
 	{
-		typedef Choice<DERIVED_BLOCK>	self_t;
-		typedef Choice<DERIVED_BLOCK>	enclosing_block_t;
+		typedef ChoiceBlock<DERIVED_BLOCK>	self_t;
+		typedef ChoiceBlock<DERIVED_BLOCK>	enclosing_block_t;
 		
 		LOG_CLASS(self_t);
 	public:
@@ -1382,11 +1316,13 @@ namespace LLInitParam
 			return mergeBlock(selfBlockDescriptor(), other, false);
 		}
 
-		bool mergeBlockParam(bool param_provided, BlockDescriptor& block_data, const self_t& other, bool overwrite)
+		bool mergeBlockParam(bool source_provided, bool dest_provided, BlockDescriptor& block_data, const self_t& source, bool overwrite)
 		{
-			if (param_provided)
+			bool source_override = source_provided && (overwrite || !dest_provided);
+
+			if (source_override || source.mCurChoice == mCurChoice)
 			{
-				return mergeBlock(block_data, other, overwrite);
+				return mergeBlock(block_data, source, overwrite);
 			}
 			return false;
 		}
@@ -1420,7 +1356,7 @@ namespace LLInitParam
 		virtual BlockDescriptor& mostDerivedBlockDescriptor() { return selfBlockDescriptor(); }
 
 	protected:
-		Choice()
+		ChoiceBlock()
 		:	mCurChoice(0)
 		{
 			BaseBlock::init(selfBlockDescriptor(), BaseBlock::selfBlockDescriptor(), sizeof(DERIVED_BLOCK));
@@ -1433,13 +1369,13 @@ namespace LLInitParam
 		class Alternative : public TypedParam<T, NAME_VALUE_LOOKUP, false>
 		{
 		public:
-			friend class Choice<DERIVED_BLOCK>;
+			friend class ChoiceBlock<DERIVED_BLOCK>;
 
 			typedef Alternative<T, NAME_VALUE_LOOKUP>									self_t;
 			typedef TypedParam<T, NAME_VALUE_LOOKUP, false, IsBlock<ParamValue<T, NAME_VALUE_LOOKUP> >::value>		super_t;
 			typedef typename super_t::value_assignment_t								value_assignment_t;
 
-			explicit Alternative(const char* name, value_assignment_t val = defaultValue<T>())
+			explicit Alternative(const char* name = "", value_assignment_t val = defaultValue<T>())
 			:	super_t(DERIVED_BLOCK::selfBlockDescriptor(), name, val, NULL, 0, 1),
 				mOriginalValue(val)
 			{
@@ -1454,10 +1390,19 @@ namespace LLInitParam
 				}
 			}
 
-			Alternative& operator=(value_assignment_t val)
+			void choose()
+			{
+				static_cast<enclosing_block_t&>(Param::enclosingBlock()).paramChanged(*this, true);
+			}
+
+			void chooseAs(value_assignment_t val)
+			{
+				super_t::set(val);
+			}
+
+			void operator=(value_assignment_t val)
 			{
 				super_t::set(val);
-				return *this;
 			}
 
 			void operator()(typename super_t::value_assignment_t val) 
@@ -1466,12 +1411,8 @@ namespace LLInitParam
 			}
 
 			operator value_assignment_t() const 
-			{ 
-				if (static_cast<enclosing_block_t&>(Param::enclosingBlock()).getCurrentChoice() == this)
-				{
-					return super_t::getValue(); 
-				}
-				return mOriginalValue;
+			{
+				return (*this)();
 			} 
 
 			value_assignment_t operator()() const 
@@ -1508,7 +1449,7 @@ namespace LLInitParam
 		}
 	};
 
-	template <typename DERIVED_BLOCK, typename BASE_BLOCK = BaseBlockWithFlags>
+	template <typename DERIVED_BLOCK, typename BASE_BLOCK = BaseBlock>
 	class Block 
 	:	public BASE_BLOCK
 	{
@@ -1604,13 +1545,6 @@ namespace LLInitParam
 
 		};
 
-		class Flag : public BaseBlockWithFlags::FlagBase
-		{
-		public:
-			Flag(const char* name) : FlagBase(name, DERIVED_BLOCK::selfBlockDescriptor().mCurrentBlockPtr)
-			{}
-		};
-
 		template <typename T, typename RANGE = BaseBlock::AnyAmount, typename NAME_VALUE_LOOKUP = TypeValues<T> >
 		class Multiple : public TypedParam<T, NAME_VALUE_LOOKUP, true>
 		{
@@ -1623,7 +1557,7 @@ namespace LLInitParam
 			typedef typename super_t::const_iterator								const_iterator;
 
 			explicit Multiple(const char* name = "")
-			:	super_t(DERIVED_BLOCK::selfBlockDescriptor(), name, container_t(), &validate, RANGE::minCount(), RANGE::maxCount())
+			:	super_t(DERIVED_BLOCK::selfBlockDescriptor(), name, container_t(), &validate, RANGE::minCount, RANGE::maxCount)
 			{}
 
 			Multiple& operator=(value_assignment_t val)
@@ -1641,100 +1575,10 @@ namespace LLInitParam
 			static bool validate(const Param* paramp) 
 			{
 				U32 num_valid = ((super_t*)paramp)->numValidElements();
-				return RANGE::minCount() <= num_valid && num_valid <= RANGE::maxCount();
+				return RANGE::minCount <= num_valid && num_valid <= RANGE::maxCount;
 			}
 		};
 
-		template <typename T, typename RANGE = BaseBlock::AnyAmount, typename NAME_VALUE_LOOKUP = TypeValues<T> >
-		class Batch : private TypedParam<T, NAME_VALUE_LOOKUP, false>
-		{
-		public:
-			typedef ParamValue<T, NAME_VALUE_LOOKUP>										param_value_t;
-			typedef TypedParam<T, NAME_VALUE_LOOKUP, false, IsBlock<param_value_t>::value>	super_t;
-			typedef Batch<T, RANGE, NAME_VALUE_LOOKUP>										self_t;
-			typedef typename super_t::value_assignment_t									value_assignment_t;
-			typedef typename super_t::value_t												value_t;
-
-			struct BatchDefaultValue : public ParamDescriptor::UserData
-			{
-				BatchDefaultValue(const T& value)
-				:	mValue(value)
-				{}
-
-				T mValue;
-			};
-
-			explicit Batch(const char* name, value_assignment_t val)
-			:	super_t(DERIVED_BLOCK::selfBlockDescriptor(), name, val, NULL, 0, 1),
-				mLastParseGeneration(-1)
-			{
-				BlockDescriptor& block_descriptor = DERIVED_BLOCK::selfBlockDescriptor();
-				if (LL_UNLIKELY(block_descriptor.mInitializationState == BlockDescriptor::INITIALIZING))
-				{
-					ParamDescriptorPtr param_descriptorp = block_descriptor.mCurrentBlockPtr->findParamDescriptor(*this);
-
-					if (param_descriptorp)
-					{
-						param_descriptorp->mDeserializeFunc = &deserializeParam;
-						param_descriptorp->mUserData = new BatchDefaultValue(new param_value_t(val));
-					}
-				}
-			}
-
-			explicit Batch(const char* name = "")
-			:	super_t(DERIVED_BLOCK::selfBlockDescriptor(), name, defaultValue<T>(), NULL, 0, 1),
-				mLastParseGeneration(-1)
-			{
-				BlockDescriptor& block_descriptor = DERIVED_BLOCK::selfBlockDescriptor();
-				if (LL_UNLIKELY(block_descriptor.mInitializationState == BlockDescriptor::INITIALIZING))
-				{
-					ParamDescriptorPtr param_descriptorp = block_descriptor.mCurrentBlockPtr->findParamDescriptor(*this);
-
-					if (param_descriptorp)
-					{
-						param_descriptorp->mDeserializeFunc = &deserializeParam;
-					}
-				}
-			}
-
-			Batch& operator=(value_assignment_t val)
-			{
-				set(val);
-				return *this;
-			}
-
-			DERIVED_BLOCK& operator()(value_assignment_t val)
-			{
-				super_t::set(val);
-				return static_cast<DERIVED_BLOCK&>(Param::enclosingBlock());
-			}
-
-			using super_t::operator();
-
-		private:
-			static bool deserializeParam(Param& param, Parser& parser, const Parser::name_stack_range_t& name_stack, S32 generation) 
-			{
-				self_t& typed_param = static_cast<self_t&>(param);
-
-				if (generation != typed_param.mLastParseGeneration)
-				{
-					ParamDescriptorPtr descriptor = typed_param.enclosingBlock().findParamDescriptor(param);
-					if (descriptor && static_cast<BatchDefaultValue*>(descriptor->mUserData))
-					{
-						static_cast<param_value_t&>(typed_param) = (static_cast<BatchDefaultValue*>(descriptor->mUserData))->mValue;
-					}
-					else
-					{
-						static_cast<param_value_t&>(typed_param) = param_value_t(value_t());
-					}
-					typed_param.mLastParseGeneration = generation;
-				}
-				return super_t::deserializeParam(param, parser, name_stack, generation);
-			}
-
-			S32 mLastParseGeneration;
-		};
-
 		class Deprecated : public Param
 		{
 		public:
@@ -1769,6 +1613,7 @@ namespace LLInitParam
 			}
 		};
 
+		// different semantics for documentation purposes, but functionally identical
 		typedef Deprecated Ignored;
 
 	protected:
@@ -1790,6 +1635,106 @@ namespace LLInitParam
 
 	};
 	
+	template <typename DERIVED_BLOCK, typename BASE_BLOCK = BaseBlock>
+	class BatchBlock
+	:	public Block<DERIVED_BLOCK, BASE_BLOCK>
+	{
+	public:
+		typedef BatchBlock<DERIVED_BLOCK, BASE_BLOCK> self_t;
+		typedef Block<DERIVED_BLOCK, BASE_BLOCK> super_t;
+
+		BatchBlock()
+		:	mLastParseGeneration(-1)
+		{}
+
+		bool deserializeBlock(Parser& p, Parser::name_stack_range_t name_stack, S32 generation)
+		{
+			if (generation != mLastParseGeneration)
+			{
+				// reset block
+				*static_cast<DERIVED_BLOCK*>(this) = defaultBatchValue();
+				mLastParseGeneration = generation;
+			}
+			return super_t::deserializeBlock(p, name_stack, generation);
+		}
+
+		bool mergeBlock(BlockDescriptor& block_data, const BaseBlock& other, bool overwrite)
+		{
+			if (overwrite)
+			{
+				*static_cast<DERIVED_BLOCK*>(this) = defaultBatchValue();
+				mLastParseGeneration = -1;
+				// merge individual parameters into destination
+				return super_t::mergeBlock(super_t::selfBlockDescriptor(), src_typed_param, overwrite);
+			}
+			return false;
+		}
+	protected:
+		static const DERIVED_BLOCK& defaultBatchValue()
+		{
+			static DERIVED_BLOCK default_value;
+			return default_value;
+		}
+
+		S32 mLastParseGeneration;
+	};
+
+	
+
+	template<typename DERIVED_BLOCK,
+			typename BASE_BLOCK,
+			typename NAME_VALUE_LOOKUP>
+	class ParamValue <BatchBlock<DERIVED_BLOCK, BASE_BLOCK>,
+					NAME_VALUE_LOOKUP,
+					true>
+	:	public Param,
+		protected BatchBlock<DERIVED_BLOCK, BASE_BLOCK>
+	{
+		typedef const BatchBlock<DERIVED_BLOCK, BASE_BLOCK>&	value_assignment_t;
+
+		ParamValue()
+		:	T(),
+			mKeyVersion(0),
+			mValidatedVersion(-1),
+			mValidated(false)
+		{}
+
+		ParamValue(value_assignment_t other)
+		:	T(other),
+			mKeyVersion(0),
+			mValidatedVersion(-1),
+			mValidated(false)
+		{
+		}
+
+		void setValue(value_assignment_t val)
+		{
+			*this = val;
+			mLastParseGeneration = -1;
+		}
+
+		value_assignment_t getValue() const
+		{
+			return *this;
+		}
+
+		BatchBlock<DERIVED_BLOCK, BASE_BLOCK>& getValue()
+		{
+			return *this;
+		}
+
+		operator value_assignment_t() const
+		{
+			return *this;
+		}
+
+		value_assignment_t operator()() const
+		{
+			return *this;
+		}
+
+	};
+
 	template<typename T>
 	class CustomParamValue
 	:	public Block<ParamValue<T, TypeValues<T> > >,
@@ -1955,6 +1900,16 @@ namespace LLInitParam
 			return mValue;
 		}
 
+		operator value_assignment_t() const
+		{
+			return getValue();
+		}
+
+		value_assignment_t operator()() const
+		{
+			return getValue();
+		}
+
 		S32 				mKeyVersion;
 
 	protected:
@@ -1965,30 +1920,29 @@ namespace LLInitParam
 			mValue = value;
 		}
 
-		bool mergeBlockParam(bool param_provided, BlockDescriptor& block_data, const BaseBlock& other, bool overwrite)
+		bool mergeBlockParam(bool source_provided, bool dst_provided, BlockDescriptor& block_data, const BaseBlock& source, bool overwrite)
 		{
-			if (param_provided)
-			{
-				return mergeBlock(block_data, other, overwrite);
-			}
-			return false;
-		}
+			bool source_override = source_provided && (overwrite || !dst_provided);
 
-		bool mergeBlock(BlockDescriptor& block_data, const BaseBlock& other, bool overwrite)
-		{
-			const derived_t& src_typed_param = static_cast<const derived_t&>(other);
+			const derived_t& src_typed_param = static_cast<const derived_t&>(source);
 
-			if (src_typed_param.mValueAge == VALUE_AUTHORITATIVE)
+			if (source_override && src_typed_param.mValueAge == VALUE_AUTHORITATIVE)
 			{
 				// copy value over
 				setValue(src_typed_param.getValue());
 				return true;
 			}
-			else
+			// merge individual parameters into destination
+			if (mValueAge == VALUE_AUTHORITATIVE)
 			{
-				// merge individual parameters into destination
-				return block_t::mergeBlock(block_t::selfBlockDescriptor(), src_typed_param, overwrite);
+				static_cast<derived_t*>(this)->updateBlockFromValue(dst_provided);
 			}
+			return mergeBlock(block_data, source, overwrite);
+		}
+
+		bool mergeBlock(BlockDescriptor& block_data, const BaseBlock& source, bool overwrite)
+		{
+			return block_t::mergeBlock(block_data, source, overwrite);
 		}
 
 		mutable S32			mValidatedVersion;