Implement copy ctor/assignment for xpath_variable_set

xpath_variable_set is essentially an associative container; it's about time it
became copyable.

Implementation is slightly tricky due to out of memory handling. Both copy ctor
and assignment operator have strong exception guarantee (even if exceptions are
disabled! which translates to "roll back on allocation errors").

2 files changed, 100 insertions, 7 deletions

diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index 078a39c..ce47fce 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -7758,6 +7758,28 @@ PUGI__NS_BEGIN
 		}
 	}
 
+	PUGI__FN bool copy_xpath_variable(xpath_variable* lhs, const xpath_variable* rhs)
+	{
+		switch (rhs->type())
+		{
+		case xpath_type_node_set:
+			return lhs->set(static_cast<const xpath_variable_node_set*>(rhs)->value);
+
+		case xpath_type_number:
+			return lhs->set(static_cast<const xpath_variable_number*>(rhs)->value);
+
+		case xpath_type_string:
+			return lhs->set(static_cast<const xpath_variable_string*>(rhs)->value);
+
+		case xpath_type_boolean:
+			return lhs->set(static_cast<const xpath_variable_boolean*>(rhs)->value);
+
+		default:
+			assert(!"Invalid variable type");
+			return false;
+		}
+	}
+
 	PUGI__FN bool get_variable_scratch(char_t (&buffer)[32], xpath_variable_set* set, const char_t* begin, const char_t* end, xpath_variable** out_result)
 	{
 		size_t length = static_cast<size_t>(end - begin);
@@ -11277,7 +11299,46 @@ namespace pugi
 		}
 	}
 
-	PUGI__FN xpath_variable* xpath_variable_set::find(const char_t* name) const
+	PUGI__FN xpath_variable_set::xpath_variable_set(const xpath_variable_set& rhs)
+	{
+		for (size_t i = 0; i < sizeof(_data) / sizeof(_data[0]); ++i)
+			_data[i] = 0;
+
+		_assign(rhs);
+	}
+
+	PUGI__FN xpath_variable_set& xpath_variable_set::operator=(const xpath_variable_set& rhs)
+	{
+		if (this == &rhs) return *this;
+
+		_assign(rhs);
+
+		return *this;
+	}
+
+	PUGI__FN void xpath_variable_set::_assign(const xpath_variable_set& rhs)
+	{
+		xpath_variable_set temp;
+
+		for (size_t i = 0; i < sizeof(_data) / sizeof(_data[0]); ++i)
+			if (rhs._data[i] && !_clone(rhs._data[i], &temp._data[i]))
+				return;
+
+		_swap(temp);
+	}
+
+	PUGI__FN void xpath_variable_set::_swap(xpath_variable_set& rhs)
+	{
+		for (size_t i = 0; i < sizeof(_data) / sizeof(_data[0]); ++i)
+		{
+			xpath_variable* chain = _data[i];
+
+			_data[i] = rhs._data[i];
+			rhs._data[i] = chain;
+		}
+	}
+
+	PUGI__FN xpath_variable* xpath_variable_set::_find(const char_t* name) const
 	{
 		const size_t hash_size = sizeof(_data) / sizeof(_data[0]);
 		size_t hash = impl::hash_string(name) % hash_size;
@@ -11290,6 +11351,33 @@ namespace pugi
 		return 0;
 	}
 
+	PUGI__FN bool xpath_variable_set::_clone(xpath_variable* var, xpath_variable** out_result)
+	{
+		xpath_variable* last = 0;
+
+		while (var)
+		{
+			// allocate storage for new variable
+			xpath_variable* nvar = impl::new_xpath_variable(var->_type, var->name());
+			if (!nvar) return false;
+
+			// link the variable to the result immediately to handle failures gracefully
+			if (last)
+				last->_next = nvar;
+			else
+				*out_result = nvar;
+
+			last = nvar;
+
+			// copy the value; this can fail due to out-of-memory conditions
+			if (!impl::copy_xpath_variable(nvar, var)) return false;
+
+			var = var->_next;
+		}
+
+		return true;
+	}
+
 	PUGI__FN xpath_variable* xpath_variable_set::add(const char_t* name, xpath_value_type type)
 	{
 		const size_t hash_size = sizeof(_data) / sizeof(_data[0]);
@@ -11339,12 +11427,12 @@ namespace pugi
 
 	PUGI__FN xpath_variable* xpath_variable_set::get(const char_t* name)
 	{
-		return find(name);
+		return _find(name);
 	}
 
 	PUGI__FN const xpath_variable* xpath_variable_set::get(const char_t* name) const
 	{
-		return find(name);
+		return _find(name);
 	}
 
 	PUGI__FN xpath_query::xpath_query(const char_t* query, xpath_variable_set* variables): _impl(0)
diff --git a/src/pugixml.hpp b/src/pugixml.hpp
index a7154f1..b8b8946 100644
--- a/src/pugixml.hpp
+++ b/src/pugixml.hpp
@@ -1075,17 +1075,22 @@ namespace pugi
 	private:
 		xpath_variable* _data[64];
 
-		// Non-copyable semantics
-		xpath_variable_set(const xpath_variable_set&);
-		xpath_variable_set& operator=(const xpath_variable_set&);
+		void _assign(const xpath_variable_set& rhs);
+		void _swap(xpath_variable_set& rhs);
+
+		xpath_variable* _find(const char_t* name) const;
 
-		xpath_variable* find(const char_t* name) const;
+		static bool _clone(xpath_variable* var, xpath_variable** out_result);
 
 	public:
 		// Default constructor/destructor
 		xpath_variable_set();
 		~xpath_variable_set();
 
+		// Copy constructor/assignment operator
+		xpath_variable_set(const xpath_variable_set& rhs);
+		xpath_variable_set& operator=(const xpath_variable_set& rhs);
+
 		// Add a new variable or get the existing one, if the types match
 		xpath_variable* add(const char_t* name, xpath_value_type type);