Implement HSCAN Redis command.

src/backends/redis/command.cpp

@@ -129,4 +129,8 @@ namespace redis {
 	auto Command::scan() -> scan_range {
 		return scan_range(scan_iterator(this, false), scan_iterator(this, true));
 	}
+
+	auto Command::hscan (boost::string_ref parKey) -> hscan_range {
+		return hscan_range(hscan_iterator(this, parKey, false), hscan_iterator(this, parKey, true));
+	}
 } //namespace redis

src/backends/redis/command.hpp

@@ -30,6 +30,7 @@
 #include <vector>
 #include <utility>
 #include <boost/range/iterator_range_core.hpp>
+#include <boost/utility/string_ref.hpp>
 
 struct redisContext;
 
@@ -38,6 +39,8 @@ namespace redis {
 	public:
 		typedef ScanIterator<std::string, ScanSingleValues<std::string>> scan_iterator;
 		typedef boost::iterator_range<scan_iterator> scan_range;
+		typedef ScanIterator<std::pair<std::string, std::string>, ScanPairs<std::pair<std::string, std::string>>> hscan_iterator;
+		typedef boost::iterator_range<hscan_iterator> hscan_range;
 
 		Command ( std::string&& parAddress, uint16_t parPort );
 		~Command ( void ) noexcept;
@@ -52,6 +55,7 @@ namespace redis {
 
 		//Single Redis command wrappers
 		scan_range scan ( void );
+		hscan_range hscan ( boost::string_ref parKey );
 
 	private:
 		using RedisConnection = std::unique_ptr<redisContext, void(*)(redisContext*)>;

src/backends/redis/scan_iterator.cpp

@@ -39,7 +39,7 @@ namespace redis {
 			return m_command->run(parCommand, boost::lexical_cast<std::string>(parScanContext));
 		}
 
-		RedisReplyType ScanIteratorBaseClass::run (const char* parCommand, const std::string& parParameter, long long parScanContext) {
+		RedisReplyType ScanIteratorBaseClass::run (const char* parCommand, const boost::string_ref& parParameter, long long parScanContext) {
 			return m_command->run(parCommand, parParameter, boost::lexical_cast<std::string>(parScanContext));
 		}
 	} //namespace implem

src/backends/redis/scan_iterator.hpp

@@ -24,6 +24,7 @@
 #include <type_traits>
 #include <vector>
 #include <cstddef>
+#include <boost/utility/string_ref.hpp>
 
 namespace redis {
 	template <typename V, typename ValueFetch>
@@ -42,7 +43,7 @@ namespace redis {
 
 			bool is_connected ( void ) const;
 			RedisReplyType run ( const char* parCommand, long long parScanContext );
-			RedisReplyType run ( const char* parCommand, const std::string& parParameter, long long parScanContext );
+			RedisReplyType run ( const char* parCommand, const boost::string_ref& parParameter, long long parScanContext );
 
 			bool is_equal ( const ScanIteratorBaseClass& parOther ) const { return m_command == parOther.m_command; }
 
@@ -52,9 +53,10 @@ namespace redis {
 	} //namespace implem
 
 	template <typename V, typename ValueFetch>
-	class ScanIterator : private implem::ScanIteratorBaseClass, public implem::ScanIteratorBaseIterator<V, ValueFetch> {
+	class ScanIterator : private implem::ScanIteratorBaseClass, public implem::ScanIteratorBaseIterator<V, ValueFetch>, private ValueFetch {
 		friend class boost::iterator_core_access;
 		typedef implem::ScanIteratorBaseIterator<V, ValueFetch> base_iterator;
+		define_has_method(scan_target, ScanTarget);
 	public:
 		typedef typename base_iterator::difference_type difference_type;
 		typedef typename base_iterator::value_type value_type;
@@ -62,11 +64,12 @@ namespace redis {
 		typedef typename base_iterator::reference reference;
 		typedef typename base_iterator::iterator_category iterator_category;
 
+		template <typename Dummy=ValueFetch, typename=typename std::enable_if<not HasScanTargetMethod<Dummy>::value>::type>
 		ScanIterator ( Command* parCommand, bool parEnd );
+		template <typename Dummy=ValueFetch, typename=typename std::enable_if<HasScanTargetMethod<Dummy>::value>::type>
+		ScanIterator ( Command* parCommand, boost::string_ref parKey, bool parEnd );
 
 	private:
-		define_has_method(scan_target, ScanTarget);
-
 		template <typename T>
 		RedisReplyType forward_scan_command ( typename std::enable_if<HasScanTargetMethod<T>::value, int>::type parDummy );
 		template <typename T>
@@ -77,7 +80,7 @@ namespace redis {
 		bool equal ( const ScanIterator& parOther ) const;
 		const V& dereference ( void ) const;
 
-		std::vector<RedisReplyType> m_reply;
+		std::vector<value_type> m_reply;
 		long long m_scan_context;
 		std::size_t m_curr_index;
 	};
@@ -89,6 +92,22 @@ namespace redis {
 
 		static const T& make_value ( const RedisReplyType* parItem );
 	};
+
+	template <typename P, typename A=decltype(P().first), typename B=decltype(P().second)>
+	struct ScanPairs {
+		typedef P PairType;
+
+		explicit ScanPairs ( boost::string_ref parScanTarget ) : m_scan_target(parScanTarget) {}
+
+		static constexpr const char* command ( void ) { return "HSCAN"; }
+		static constexpr const std::size_t step = 2;
+
+		static PairType make_value ( const RedisReplyType* parItem );
+		boost::string_ref scan_target ( void );
+
+	private:
+		boost::string_ref m_scan_target;
+	};
 } //namespace redis
 
 #include "scan_iterator.inl"

src/backends/redis/scan_iterator.inl

@@ -24,8 +24,31 @@ namespace redis {
 	} //namespace implem
 
 	template <typename V, typename ValueFetch>
+	template <typename Dummy, typename>
 	ScanIterator<V, ValueFetch>::ScanIterator (Command* parCommand, bool parEnd) :
 		implem::ScanIteratorBaseClass(parCommand),
+		implem::ScanIteratorBaseIterator<V, ValueFetch>(),
+		ValueFetch(),
+		m_reply(),
+		m_scan_context(0),
+		m_curr_index(0)
+	{
+		if (not parEnd) {
+			m_curr_index = 1; //Some arbitrary value so is_end()==false
+			assert(not is_end());
+			this->increment();
+		}
+		else {
+			assert(is_end());
+		}
+	}
+
+	template <typename V, typename ValueFetch>
+	template <typename Dummy, typename>
+	ScanIterator<V, ValueFetch>::ScanIterator (Command* parCommand, boost::string_ref parKey, bool parEnd) :
+		implem::ScanIteratorBaseClass(parCommand),
+		implem::ScanIteratorBaseIterator<V, ValueFetch>(),
+		ValueFetch(parKey),
 		m_reply(),
 		m_scan_context(0),
 		m_curr_index(0)
@@ -50,10 +73,10 @@ namespace redis {
 		assert(not is_end());
 		static_assert(ValueFetch::step > 0, "Can't have an increase step of 0");
 
-		if (m_curr_index + ValueFetch::step < m_reply.size()) {
-			m_curr_index += ValueFetch::step;
+		if (m_curr_index + 1 < m_reply.size()) {
+			++m_curr_index;
 		}
-		else if (m_curr_index + ValueFetch::step == m_reply.size() and not m_scan_context)	{
+		else if (m_curr_index + 1 == m_reply.size() and not m_scan_context)	{
 			m_reply.clear();
 			m_curr_index = 0;
 		}
@@ -70,7 +93,15 @@ namespace redis {
 				new_context = get_integer_autoconv_if_str(array_reply[0]);
 			} while (new_context and array_reply.empty());
 
-			m_reply = get_array(array_reply[1]);
+			const auto variant_array = get_array(array_reply[1]);
+			assert(variant_array.size() % ValueFetch::step == 0);
+			const std::size_t expected_reply_count = variant_array.size() / ValueFetch::step;
+			m_reply.clear();
+			m_reply.reserve(expected_reply_count);
+			for (std::size_t z = 0; z < variant_array.size(); z += ValueFetch::step) {
+				m_reply.push_back(ValueFetch::make_value(variant_array.data() + z));
+			}
+			assert(expected_reply_count == m_reply.size());
 			m_scan_context = new_context;
 			m_curr_index = 0;
 		}
@@ -95,7 +126,7 @@ namespace redis {
 		assert(not m_reply.empty());
 		assert(m_curr_index < m_reply.size());
 
-		return ValueFetch::make_value(m_reply.data() + m_curr_index);
+		return m_reply[m_curr_index];
 	}
 
 	template <typename V, typename ValueFetch>
@@ -115,4 +146,15 @@ namespace redis {
 		assert(parItem);
 		return get<T>(*parItem);
 	}
+
+	template <typename P, typename A, typename B>
+	P ScanPairs<P, A, B>::make_value (const RedisReplyType* parItem) {
+		assert(parItem);
+		return PairType(get<A>(parItem[0]), get<B>(parItem[1]));
+	}
+
+	template <typename P, typename A, typename B>
+	boost::string_ref ScanPairs<P, A, B>::scan_target() {
+		return m_scan_target;
+	}
 } //namespace redis