From 839faf66c0cff75985ef16525f2e0dcead880d58 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Thu, 10 Sep 2015 12:26:05 -0400
Subject: [PATCH] AtomicValue use epicsAtomic if available

---
 src/remote/codec.h | 41 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/src/remote/codec.h b/src/remote/codec.h
index 988c982..edfd6f3 100644
--- a/src/remote/codec.h
+++ b/src/remote/codec.h
@@ -21,6 +21,11 @@
 #include <osiSock.h>
 #include <epicsTime.h>
 #include <epicsThread.h>
+#include <epicsVersion.h>
+
+#if defined(EPICS_VERSION_INT) && EPICS_VERSION_INT>=VERSION_INT(3,15,1,0)
+#include <epicsAtomic.h>
+#endif
 
 #include <pv/byteBuffer.h>
 #include <pv/pvType.h>
@@ -48,8 +53,39 @@ namespace epics {
   namespace pvAccess {
     namespace detail {
 
-    // TODO replace mutex with atomic (CAS) operations
-    template<typename T> 
+#if defined(EPICS_VERSION_INT) && EPICS_VERSION_INT>=VERSION_INT(3,15,1,0)
+    template<typename T>
+    class AtomicValue
+    {
+        T val;
+    public:
+        AtomicValue() :val(0) {}
+        inline T getAndSet(T newval)
+        {
+            int oldval;
+            // epicsAtomic doesn't have unconditional swap
+            do {
+                oldval = epics::atomic::get(val);
+            }while(epics::atomic::compareAndSwap(val, oldval, newval)!=oldval);
+            return oldval;
+        }
+        inline T get() { return epics::atomic::get(val); }
+    };
+    // treat bool as int
+    template<>
+    class AtomicValue<bool>
+    {
+        AtomicValue<int> realval;
+    public:
+        inline bool getAndSet(bool newval)
+        {
+            return this->realval.getAndSet(newval?1:0)!=0;
+        }
+        inline bool get() { return !!this->realval.get(); }
+    };
+
+#else
+    template<typename T>
     class AtomicValue
     {
     public:
@@ -69,6 +105,7 @@ namespace epics {
       T _value;
       epics::pvData::Mutex mutex;
     };
+#endif
 
 
     // TODO replace this queue with lock-free implementation