From b577d476d3392ed1522fbcbe7760de2cd774e138 Mon Sep 17 00:00:00 2001
From: "kevin.larke" <kevin@larke.org>
Date: Sun, 19 Apr 2020 13:01:21 -0400
Subject: [PATCH] cwSpscQueueTmpl.h/cpp : Initial commit.

---
 cwSpScQueueTmpl.cpp | 14 ++++++++++++--
 cwSpScQueueTmpl.h   | 29 +++++++++++------------------
 2 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/cwSpScQueueTmpl.cpp b/cwSpScQueueTmpl.cpp
index 112c697..9c51e2f 100644
--- a/cwSpScQueueTmpl.cpp
+++ b/cwSpScQueueTmpl.cpp
@@ -34,6 +34,7 @@ namespace cw
     unsigned  iter;           // execution counter
     unsigned  msgN;           // count of msg's processed
     shared_t* share;          // shared variables
+    uint8_t   prevId; 
   } ctx_t;
 
 
@@ -57,7 +58,7 @@ namespace cw
         m->checksum += m->data[i];
       }
 
-      c->share->q->push(m);
+      c->share->q->publish();
 
       c->msgN++;
 
@@ -84,7 +85,16 @@ namespace cw
       
       if( curCheckSum != m->checksum )
         cwLogError(kOpFailRC,"Checksum mismatch.0x%x != 0x%x ",curCheckSum,m->checksum);
-      
+      else
+      {
+        uint8_t id = c->prevId + 1;
+        if( id != m->data[0] )
+          cwLogInfo("drop ");
+        
+        c->prevId = m->data[0];
+      }
+
+      c->msgN++;
     }
 
     c->iter++;
diff --git a/cwSpScQueueTmpl.h b/cwSpScQueueTmpl.h
index f555e38..418ed79 100644
--- a/cwSpScQueueTmpl.h
+++ b/cwSpScQueueTmpl.h
@@ -10,31 +10,27 @@ namespace cw
   public:
     spScQueueTmpl( unsigned eleN )
     {
-      _aV  = mem::allocZ<T*>(eleN);
-      _mem = mem::allocZ<T>(eleN);
-      _wi.load(std::memory_order_release);
-      _ri.load(std::memory_order_release);
-      
-      for(unsigned i=0; i<eleN; ++i)
-        _aV[i] = _mem + i;
+      _aN  = eleN;
+      _aV = mem::allocZ<T>(eleN);
+      _wi.store(0,std::memory_order_release);
+      _ri.store(0,std::memory_order_release);      
     }
 
     virtual ~spScQueueTmpl()
     {
       mem::release(_aV);
-      mem::release(_mem);
     }
 
     T* get()
     {
       unsigned wi = _wi.load( std::memory_order_relaxed );
-      return _aV[wi];
+      return _aV + wi;
     }
 
-    rc_t push( T* v )
+    rc_t publish()
     {
       unsigned ri = _ri.load( std::memory_order_acquire );
-      unsigned wi = _wi.load( std::memory_order_relaxed );
+      unsigned wi = _wi.load( std::memory_order_relaxed ); // _wi is written in this thread 
 
       // calc. the count of full elements
       unsigned n =  wi >= ri ? wi-ri : (_aN-ri) + wi;
@@ -44,11 +40,9 @@ namespace cw
       if( n >= _aN-1 )
         return kBufTooSmallRC;
 
-      // store the new element
-      _aV[wi] = v;
-
       wi = (wi+1) % _aN;
-    
+
+      // advance the write position
       _wi.store( wi, std::memory_order_release );
     
       return kOkRC;
@@ -64,7 +58,7 @@ namespace cw
       if( n == 0 )
         return nullptr;
 
-      T* v = _aV[ri];
+      T* v = _aV + ri;
 
       ri = (ri+1) % _aN;
 
@@ -78,8 +72,7 @@ namespace cw
     
   private:
     unsigned              _aN = 0;
-    T**                   _aV = nullptr;
-    T*                    _mem;
+    T*                    _aV = nullptr;
     std::atomic<unsigned> _wi;   
     std::atomic<unsigned> _ri;