Make `RemoteStore::ConnectionHandle` part of class and expose

Will need to do subclass-specific implementations in the next commit.
This isn't because there will be multiple variations of the daemon
protocol (whew!) but because different clients pick and choose different
parts to use.

1 files changed, 31 insertions, 0 deletions

diff --git a/src/libstore/remote-store-connection.hh b/src/libstore/remote-store-connection.hh
index d32d91a60..ce4740a9c 100644
--- a/src/libstore/remote-store-connection.hh
+++ b/src/libstore/remote-store-connection.hh
@@ -1,5 +1,6 @@
 #include "remote-store.hh"
 #include "worker-protocol.hh"
+#include "pool.hh"
 
 namespace nix {
 
@@ -94,4 +95,34 @@ struct RemoteStore::Connection
     std::exception_ptr processStderr(Sink * sink = 0, Source * source = 0, bool flush = true);
 };
 
+/**
+ * A wrapper around Pool<RemoteStore::Connection>::Handle that marks
+ * the connection as bad (causing it to be closed) if a non-daemon
+ * exception is thrown before the handle is closed. Such an exception
+ * causes a deviation from the expected protocol and therefore a
+ * desynchronization between the client and daemon.
+ */
+struct RemoteStore::ConnectionHandle
+{
+    Pool<RemoteStore::Connection>::Handle handle;
+    bool daemonException = false;
+
+    ConnectionHandle(Pool<RemoteStore::Connection>::Handle && handle)
+        : handle(std::move(handle))
+    { }
+
+    ConnectionHandle(ConnectionHandle && h)
+        : handle(std::move(h.handle))
+    { }
+
+    ~ConnectionHandle();
+
+    RemoteStore::Connection & operator * () { return *handle; }
+    RemoteStore::Connection * operator -> () { return &*handle; }
+
+    void processStderr(Sink * sink = 0, Source * source = 0, bool flush = true);
+
+    void withFramedSink(std::function<void(Sink & sink)> fun);
+};
+
 }