net: introduce Sock::WaitMany()

It allows waiting concurrently on more than one socket. Being a
`virtual` `Sock` method it can be overriden by tests.

Will be used to replace `CConnman::SocketEvents()`.

1 files changed, 52 insertions, 0 deletions

diff --git a/src/util/sock.h b/src/util/sock.h
index e6419eb8ce..3245820995 100644
--- a/src/util/sock.h
+++ b/src/util/sock.h
@@ -12,6 +12,7 @@
 #include <chrono>
 #include <memory>
 #include <string>
+#include <unordered_map>
 
 /**
  * Maximum time to wait for I/O readiness.
@@ -157,6 +158,57 @@ public:
                                     Event requested,
                                     Event* occurred = nullptr) const;
 
+    /**
+     * Auxiliary requested/occurred events to wait for in `WaitMany()`.
+     */
+    struct Events {
+        explicit Events(Event req) : requested{req}, occurred{0} {}
+        Event requested;
+        Event occurred;
+    };
+
+    struct HashSharedPtrSock {
+        size_t operator()(const std::shared_ptr<const Sock>& s) const
+        {
+            return s ? s->m_socket : std::numeric_limits<SOCKET>::max();
+        }
+    };
+
+    struct EqualSharedPtrSock {
+        bool operator()(const std::shared_ptr<const Sock>& lhs,
+                        const std::shared_ptr<const Sock>& rhs) const
+        {
+            if (lhs && rhs) {
+                return lhs->m_socket == rhs->m_socket;
+            }
+            if (!lhs && !rhs) {
+                return true;
+            }
+            return false;
+        }
+    };
+
+    /**
+     * On which socket to wait for what events in `WaitMany()`.
+     * The `shared_ptr` is copied into the map to ensure that the `Sock` object
+     * is not destroyed (its destructor would close the underlying socket).
+     * If this happens shortly before or after we call `poll(2)` and a new
+     * socket gets created under the same file descriptor number then the report
+     * from `WaitMany()` will be bogus.
+     */
+    using EventsPerSock = std::unordered_map<std::shared_ptr<const Sock>, Events, HashSharedPtrSock, EqualSharedPtrSock>;
+
+    /**
+     * Same as `Wait()`, but wait on many sockets within the same timeout.
+     * @param[in] timeout Wait this long for at least one of the requested events to occur.
+     * @param[in,out] events_per_sock Wait for the requested events on these sockets and set
+     * `occurred` for the events that actually occurred.
+     * @return true on success (or timeout, if all `what[].occurred` are returned as 0),
+     * false otherwise
+     */
+    [[nodiscard]] virtual bool WaitMany(std::chrono::milliseconds timeout,
+                                        EventsPerSock& events_per_sock) const;
+
     /* Higher level, convenience, methods. These may throw. */
 
     /**