BufferProvider: decision to use a free-standing pool with lock-free queue

After several fruitless attempts, I have decided now
to settle for self-contained ''memory pool'' component,
that can be operated **thread-locally** and employs a
**lock-free** message queue for the allotment of memory.

Seemingly the question of how this relates to `BufferMetadata`
must remain unresolved for the time being, until the entire
buffer memory subsystem is available for empirical investigation.

src/vault/mem/local-mem-pool.hpp

@@ -25,17 +25,25 @@
 #define VAULT_MEM_LOCAL_MEM_POOL_H
 
 
+#include "lib/error.hpp"
 //#include "vault/mem/buffer-provider-setup.hpp"
 //#include "vault/mem/engine-buffer-metadata.hpp"
 //#include "vault/mem/buffer-metadata.hpp"
 #include "vault/mem/buffhandle.hpp" //////////////TODO
 //#include "lib/local-slice.hpp"
 //#include "lib/depend.hpp"
+#include "lib/nocopy.hpp"
+
+#include <tuple>
 
 
 namespace vault {
 namespace mem   {
+  namespace err = lumiera::error;
   
+  using std::tuple;
+  
+  class PoolDiagnostic;
   
   
   /**
@@ -47,9 +55,71 @@ namespace mem   {
     public:
       LocalMemPool()
         { }
+      
+      
+      /* ===== Pool Access API ===== */
+      
+      bool empty()  const { return 0 == size(); }
+      size_t size() const { return 0; } ///////////////////////OOO
+      
+      bool
+      canServe (size_t sizRequest)
+        {
+          return false; ///////////////////////////////////////OOO
+        }
+      
+      void
+      add (Buff* mem, size_t siz)
+        {
+          TODO ("add new alloc to pool");
+        }
+      
+      void
+      reAdd (Buff* mem)
+        {
+          TODO ("return known alloc into pool");
+        }
+      
+      tuple<Buff*,size_t>
+      retrieve (size_t sizRequest)
+        {
+          return {nullptr, 0};
+        }
+      
+    private:
+      
+      friend class PoolDiagnostic;
     };
   
   
+  class PoolDiagnostic
+    : util::MoveOnly
+    {
+      LocalMemPool memPool_;
+    public:
+      PoolDiagnostic (LocalMemPool& lmp)
+        : memPool_{lmp}
+        { }
+      
+      bool
+      isEmpty()
+        {
+          return true;
+        } ///////////////////OOO
+      
+      size_t
+      cnt (size_t siz)
+        {
+          return 0; ////////////////////OOO
+        }
+    };
+  
+  
+  inline PoolDiagnostic
+  watch (LocalMemPool& lmp)
+  {
+    return PoolDiagnostic{lmp};
+  }
   
 }} // namespace vault::mem
 #endif /*VAULT_MEM_LOCAL_MEM_POOL_H*/

tests/vault/mem/local-mem-pool-test.cpp

@@ -38,13 +38,19 @@ namespace test  {
   
   namespace { // Test helper
     
-//    template<typename X>
-//    Buff*
-//    mark_as_Buffer(X& something)
-//      {
-//        return reinterpret_cast<Buff*> (std::addressof(something));
-//      }
-//    
+    inline constexpr Buff*
+    fake_Buffer(size_t id)
+      {
+        return reinterpret_cast<Buff*> (id);
+      }
+    
+    Buff* const MEM1 = fake_Buffer(1);
+    Buff* const MEM2 = fake_Buffer(2);
+    Buff* const MEM3 = fake_Buffer(3);
+    
+    const size_t SIZ10{10};
+    const size_t SIZ20{20};
+    const size_t SIZ30{30};
   }
   
   
@@ -63,15 +69,52 @@ namespace test  {
         {
           seedRand();
           
-          verify_blah();
-          verify_lolz();
+          simpleUse();
+          verify_matchAlloc();
+          verify_selectAlloc();
+          verify_pruneAlloc();
         }
       
       
       
-      /** @test  */
+      /** @test show how to place an allocation into the pool */
       void
-      verify_blah()
+      simpleUse()
+        {
+          LocalMemPool pool;
+          pool.add (MEM1, SIZ20);
+          CHECK (pool.canServe(SIZ20));
+          CHECK (pool.canServe(SIZ10));
+          
+          auto [mem,siz] = pool.retrieve (SIZ10); 
+          CHECK (MEM1 == mem);
+          CHECK (SIZ20 == siz);
+          CHECK (not pool.canServe(SIZ10));
+          
+          pool.reAdd (MEM1);
+          CHECK (pool.canServe(SIZ20));
+        }
+      
+      
+      
+      /** @test 
+       */
+      void
+      verify_matchAlloc()
+        {
+          LocalMemPool pool;
+          CHECK (watch(pool).isEmpty());
+          
+          pool.add (MEM1, SIZ10);
+          CHECK (watch(pool).cnt(SIZ10) == 1);
+        }
+      
+      
+      
+      /** @test 
+       */
+      void
+      verify_selectAlloc()
         {
         }
       
@@ -80,7 +123,7 @@ namespace test  {
       /** @test 
        */
       void
-      verify_lolz()
+      verify_pruneAlloc()
         {
         }
     };