From 709b457e176263673dd54a67f74a60f23930667b Mon Sep 17 00:00:00 2001
From: Andrej Babic <andrej.babic@psi.ch>
Date: Wed, 29 Apr 2020 11:10:43 +0200
Subject: [PATCH] Fix FastQueue bugs

---
 core-buffer/include/FastQueue.hpp |  8 +++++---
 core-buffer/src/FastQueue.cpp     | 11 +++++++----
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/core-buffer/include/FastQueue.hpp b/core-buffer/include/FastQueue.hpp
index 84a9139..4103c55 100644
--- a/core-buffer/include/FastQueue.hpp
+++ b/core-buffer/include/FastQueue.hpp
@@ -17,9 +17,11 @@ class FastQueue {
 
 public:
 
-    int SLOT_EMPTY=0;
-    int SLOT_RESERVED=1;
-    int SLOT_READY=1;
+    enum SLOT_STATUS {
+        EMPTY=0,
+        RESERVED=1,
+        READY=2
+    };
 
     FastQueue(const size_t slot_data_n_bytes, const uint16_t n_slots);
     virtual ~FastQueue();
diff --git a/core-buffer/src/FastQueue.cpp b/core-buffer/src/FastQueue.cpp
index 4ce18b6..3e9765f 100644
--- a/core-buffer/src/FastQueue.cpp
+++ b/core-buffer/src/FastQueue.cpp
@@ -45,10 +45,11 @@ char* FastQueue<T>::get_data_buffer(const int slot_id)
 template<class T>
 int FastQueue<T>::reserve()
 {
+    int expected = SLOT_STATUS::EMPTY;
     // If (buffer_status==SLOT_EMPTY) buffer_status=SLOT_RESERVED.
     bool slot_reserved =
             buffer_status_[write_slot_id_].compare_exchange_strong(
-                SLOT_EMPTY, SLOT_RESERVED);
+                    expected, SLOT_STATUS::RESERVED);
 
     if (!slot_reserved) {
         return -1;
@@ -60,10 +61,11 @@ int FastQueue<T>::reserve()
 template<class T>
 void FastQueue<T>::commit()
 {
+    int expected = SLOT_STATUS::RESERVED;
     // If (buffer_status==SLOT_RESERVED) buffer_status=SLOT_READY.
     bool slot_ready =
             buffer_status_[write_slot_id_].compare_exchange_strong(
-                    SLOT_RESERVED, SLOT_READY);
+                    expected, SLOT_STATUS::READY);
 
     if (!slot_ready) {
         throw runtime_error("Slot should be reserved first.");
@@ -76,7 +78,7 @@ void FastQueue<T>::commit()
 template<class T>
 int FastQueue<T>::read()
 {
-    if (buffer_status_[read_slot_id_] != SLOT_READY) {
+    if (buffer_status_[read_slot_id_] != SLOT_STATUS::READY) {
         return -1;
     }
 
@@ -86,10 +88,11 @@ int FastQueue<T>::read()
 template<class T>
 void FastQueue<T>::release()
 {
+    int expected = SLOT_STATUS::READY;
     // If (buffer_status==SLOT_RESERVED) buffer_status=SLOT_READY.
     bool slot_empty =
             buffer_status_[read_slot_id_].compare_exchange_strong(
-                    SLOT_READY, SLOT_EMPTY);
+                    expected, SLOT_STATUS::EMPTY);
 
     if (!slot_empty) {
         throw runtime_error("Slot should be ready first.");