Introduce HashQ<> and UnorderedMap<>

Invading into std:: is frowned upon, even though legitimate from the C++ standard perspective. Given that it's possible to pass a hash object to unordered_map, it only takes an alias for std::unordered_map to avoid having to specialize std::hash. And besides, a generic compatibility bridge between qHash and std::hash has been long needed.

std::hash<QString> in converters.h remains for now; it will be dropped separately when the API files get regenerated to use UnorderedMap.

6 files changed, 22 insertions, 24 deletions

diff --git a/lib/connection.cpp b/lib/connection.cpp
index 5ebdcf6c..c3e46356 100644
--- a/lib/connection.cpp
+++ b/lib/connection.cpp
@@ -98,7 +98,7 @@ public:
     // See https://github.com/quotient-im/libQuotient/wiki/Handling-direct-chat-events
     DirectChatsMap dcLocalAdditions;
     DirectChatsMap dcLocalRemovals;
-    std::unordered_map<QString, EventPtr> accountData;
+    UnorderedMap<QString, EventPtr> accountData;
     int syncLoopTimeout = -1;
 
     GetCapabilitiesJob* capabilitiesJob = nullptr;
diff --git a/lib/connection.h b/lib/connection.h
index 7e32e5c9..b4b16679 100644
--- a/lib/connection.h
+++ b/lib/connection.h
@@ -124,7 +124,7 @@ public:
     using IgnoredUsersList = IgnoredUsersEvent::content_type;
 
     using UsersToDevicesToEvents =
-        std::unordered_map<QString, std::unordered_map<QString, const Event&>>;
+        UnorderedMap<QString, UnorderedMap<QString, const Event&>>;
 
     enum RoomVisibility {
         PublishRoom,
diff --git a/lib/converters.h b/lib/converters.h
index 587e4544..b753a80b 100644
--- a/lib/converters.h
+++ b/lib/converters.h
@@ -28,16 +28,10 @@
 #include <QtCore/QUrlQuery>
 #include <QtCore/QVector>
 
-#include <unordered_map>
 #include <vector>
-#if 0 // Waiting for C++17
-#    include <experimental/optional>
-
-template <typename T>
-using optional = std::experimental::optional<T>;
-#endif
 
 // Enable std::unordered_map<QString, T>
+// REMOVEME in favor of UnorderedMap, once we regenerate API files
 namespace std {
 template <>
 struct hash<QString> {
@@ -296,9 +290,9 @@ struct HashMapFromJson {
     }
 };
 
-template <typename T>
-struct JsonObjectConverter<std::unordered_map<QString, T>>
-    : public HashMapFromJson<std::unordered_map<QString, T>> {};
+template <typename T, typename HashT>
+struct JsonObjectConverter<std::unordered_map<QString, T, HashT>>
+    : public HashMapFromJson<std::unordered_map<QString, T, HashT>> {};
 
 template <typename T>
 struct JsonObjectConverter<QHash<QString, T>>
diff --git a/lib/events/stateevent.h b/lib/events/stateevent.h
index 74e36e74..710b4271 100644
--- a/lib/events/stateevent.h
+++ b/lib/events/stateevent.h
@@ -129,13 +129,3 @@ private:
     std::unique_ptr<Prev<ContentT>> _prev;
 };
 } // namespace Quotient
-
-namespace std {
-template <>
-struct hash<Quotient::StateEventKey> {
-    size_t operator()(const Quotient::StateEventKey& k) const Q_DECL_NOEXCEPT
-    {
-        return qHash(k);
-    }
-};
-} // namespace std
diff --git a/lib/room.cpp b/lib/room.cpp
index 2c9fca63..2f697589 100644
--- a/lib/room.cpp
+++ b/lib/room.cpp
@@ -98,7 +98,7 @@ public:
     RoomSummary summary = { none, 0, none };
     /// The state of the room at timeline position before-0
     /// \sa timelineBase
-    std::unordered_map<StateEventKey, StateEventPtr> baseState;
+    UnorderedMap<StateEventKey, StateEventPtr> baseState;
     /// State event stubs - events without content, just type and state key
     static decltype(baseState) stubbedState;
     /// The state of the room at timeline position after-maxTimelineIndex()
@@ -131,7 +131,7 @@ public:
     QHash<const User*, QString> lastReadEventIds;
     QString serverReadMarker;
     TagsMap tags;
-    std::unordered_map<QString, EventPtr> accountData;
+    UnorderedMap<QString, EventPtr> accountData;
     QString prevBatch;
     QPointer<GetRoomEventsJob> eventsHistoryJob;
     QPointer<GetMembersByRoomJob> allMembersJob;
diff --git a/lib/util.h b/lib/util.h
index 7c79804b..788ce5bc 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -19,9 +19,11 @@
 #pragma once
 
 #include <QtCore/QLatin1String>
+#include <QtCore/QHashFunctions>
 
 #include <functional>
 #include <memory>
+#include <unordered_map>
 
 // Along the lines of Q_DISABLE_COPY - the upstream version comes in Qt 5.13
 #define DISABLE_MOVE(_ClassName)               \
@@ -29,6 +31,18 @@
     _ClassName& operator=(_ClassName&&) Q_DECL_EQ_DELETE;
 
 namespace Quotient {
+/// An equivalent of std::hash for QTypes to enable std::unordered_map<QType, ...>
+template <typename T>
+struct HashQ {
+    size_t operator()(const T& s) const Q_DECL_NOEXCEPT
+    {
+        return qHash(s, uint(qGlobalQHashSeed()));
+    }
+};
+/// A wrapper around std::unordered_map compatible with types that have qHash
+template <typename KeyT, typename ValT>
+using UnorderedMap = std::unordered_map<KeyT, ValT, HashQ<KeyT>>;
+
 struct NoneTag {};
 constexpr NoneTag none {};