tagfile: Support mapped containers, similar to a sparse array

Note: This now treats vector<pair> as a mapped container as well – an ordered multimap, so to speak

src/fileio/tagfile.hpp

@@ -44,6 +44,12 @@ namespace detail {
 	
 	template<>
 	struct is_container<std::string> : std::false_type {};
+	
+	template<typename T>
+	struct is_pair : public std::false_type {};
+	
+	template<typename A, typename B>
+	struct is_pair<std::pair<A, B>> : public std::true_type {};
 }
 
 class cTagFile;
@@ -286,7 +292,8 @@ public:
 		}
 	}
 	template<typename Container>
-	void extractSparse(Container& values, typename Container::value_type def = typename Container::value_type()) const {
+	typename std::enable_if<!detail::is_pair<typename Container::value_type>::value>::type
+	extractSparse(Container& values, typename Container::value_type def = typename Container::value_type()) const {
 		using T = typename Container::value_type;
 		values.clear();
 		for(size_t n = 0; n < tags.size(); n++) {
@@ -298,7 +305,8 @@ public:
 		}
 	}
 	template<typename Container>
-	void encodeSparse(const Container& values, typename Container::value_type def = typename Container::value_type()) {
+	typename std::enable_if<!detail::is_pair<typename Container::value_type>::value>::type
+	encodeSparse(const Container& values, typename Container::value_type def = typename Container::value_type()) {
 		size_t i = 0;
 		for(const auto& value : values) {
 			if(value != def) {
@@ -307,6 +315,29 @@ public:
 			i++;
 		}
 	}
+	template<typename Container>
+	typename std::enable_if<detail::is_pair<typename Container::value_type>::value>::type
+	extractSparse(Container& values) const {
+		using T = std::pair<
+			typename std::remove_cv<typename Container::value_type::first_type>::type,
+			typename Container::value_type::second_type
+		>;
+		values.clear();
+		for(size_t n = 0; n < tags.size(); n++) {
+			T value;
+			*this >> value.first >> value.second;
+			values.insert(value);
+		}
+	}
+	template<typename Container>
+	typename std::enable_if<detail::is_pair<typename Container::value_type>::value>::type
+	encodeSparse(const Container& values, typename Container::value_type::second_type def = typename Container::value_type::second_type()) {
+		for(const auto& value : values) {
+			if(value.second != def) {
+				*this << value.first << value.second;
+			}
+		}
+	}
 	template<typename T>
 	void extract(vector2d<T>& values) const {
 		values.resize(0, tags.size());

test/tagfile.cpp

@@ -82,6 +82,10 @@ TEST_CASE("Complex tag file") {
 	"SDF 0 0 12\n"
 	"SDF 1 3 52\n"
 	"SDF 5 9 81\n"
+	"DICT 'a b' 'c d'\n"
+	"DICT abc def\n"
+	"DICT blah blah\n"
+	"DICT foo bar\n"
 	// Page 4 and onward, a series of identical pages
 	"\f"
 	"ID 12\n"
@@ -145,6 +149,13 @@ TEST_CASE("Complex tag file") {
 		sdf[1][3] = 52;
 		sdf[5][9] = 81;
 		p3["SDF"].encodeSparse(sdf);
+		std::map<std::string, std::string> dict{
+			{"foo", "bar"},
+			{"a b", "c d"},
+			{"abc", "def"},
+			{"blah", "blah"},
+		};
+		p3["DICT"].encodeSparse(dict);
 		auto& p4a = content.add();
 		p4a["ID"] << '\x0c';
 		p4a["VALUE"] << 400;
@@ -274,6 +285,17 @@ TEST_CASE("Complex tag file") {
 						CHECK(sdf[x][y] == 0);
 					}
 				}
+				std::map<std::string, std::string> dict;
+				page["DICT"].extractSparse(dict);
+				REQUIRE(dict.size() == 4);
+				CHECK(dict.count("foo") == 1);
+				CHECK(dict["foo"] == "bar");
+				CHECK(dict.count("a b") == 1);
+				CHECK(dict["a b"] == "c d");
+				CHECK(dict.count("abc") == 1);
+				CHECK(dict["abc"] == "def");
+				CHECK(dict.count("blah") == 1);
+				CHECK(dict["blah"] == "blah");
 			} else {
 				p4++;
 				char id;