From 473baa8d9a1ac81774a2c9157e03a2f4ecc299ad Mon Sep 17 00:00:00 2001
From: heck <heck@pep.foundation>
Date: Mon, 28 Feb 2022 23:34:36 +0100
Subject: [PATCH] Import: module 'pc_container' from libpEpAdapter

---
 src/pc_container.hh | 87 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)
 create mode 100644 src/pc_container.hh

diff --git a/src/pc_container.hh b/src/pc_container.hh
new file mode 100644
index 0000000..d41e176
--- /dev/null
+++ b/src/pc_container.hh
@@ -0,0 +1,87 @@
+// This file is under GNU General Public License 3.0
+// see LICENSE.txt
+
+#ifndef LIBPEPADAPTER_PC_CONTAINER_HH
+#define LIBPEPADAPTER_PC_CONTAINER_HH
+
+// Container adapter that contains a container and a producer/consume queue
+// that holds references to all changed elements
+
+#include <functional>
+#include <list>
+#include "locked_queue.hh"
+
+namespace pEp
+{
+
+enum class PC_State { Illegal = 0, Created = 1, Deleted = 2, Changed = 3 };
+
+
+// Producer/Consumer container.
+// 
+// The "Producer" works on a std::list: inserts, changes, erases elements and 
+// informs a "Consumer" via a queue about the changes.
+//
+// The "Consumer" can poll for changes and process them asynchronously.
+//
+// Pdata = data of the producer. May be read by the consumer.
+// Cdata = data of the consumer.
+template<class Pdata, class Cdata>
+class pc_container
+{
+public:
+    struct PC
+    {
+        Pdata* pdata; // data of the producer. Will be nullptr for erased elements
+        Cdata* cdata; // data of the consumer.
+        
+        PC_State state() const noexcept { return PC_State((pdata!=nullptr) + (cdata!=nullptr)*2); }
+    };
+    
+    typedef std::list<PC> Container;
+    
+    typename Container::const_iterator cbegin() const noexcept { return c.cbegin(); }
+    typename Container::const_iterator cend()   const noexcept { return c.cend();   }
+    typename Container::const_iterator begin()  const noexcept { return c.cbegin(); }
+    typename Container::const_iterator end()    const noexcept { return c.cend();   }
+    typename Container::iterator       begin()        noexcept { return c.begin(); }
+    typename Container::iterator       end()          noexcept { return c.end();   }
+    
+    std::size_t size()  const noexcept { return c.size();  }
+    bool        empty() const noexcept { return c.empty(); }
+
+
+    void insert(Pdata* pd)
+    {
+        c.push_back({ pd, nullptr });
+    }
+    
+    // Beware: does not delete *pdata nor *cdata! That's producer's and consumer's task!
+    typename Container::iterator erase(typename Container::const_iterator pos)
+    {
+        return c.erase(pos);
+    }
+    
+    // removes all elements with pdata==null && cdata==null
+    void compact()
+    {
+        c.remove_if( [](const PC& elem) { return elem.pdata==nullptr && elem.cdata==nullptr; } );
+    }
+    
+    // clear the container. Delete all *pdata via custom deleter functor.
+    void clear(std::function<void(Pdata*)> deleter = [](Pdata *e) { delete e; })
+    {
+        for(auto q=begin(); q!=end(); q=erase(q))
+        {
+            deleter(q->pdata);
+            q->pdata = nullptr;
+        }
+    }
+
+private:
+    Container c;
+};
+
+} // end of namespace pEp
+#endif // LIBPEPADAPTER_PC_CONTAINER_HH
+