From bdb99f1d138398886d41f2fc74353ee2bdfdf4d1 Mon Sep 17 00:00:00 2001
From: Andrej Babic <andrej.babic@psi.ch>
Date: Mon, 6 Apr 2020 11:12:30 +0200
Subject: [PATCH] Improve RingBuffer initialization

Remove automatic initialization on slot reservation - the client will need to take care
of the initialization at the most appropriate time - also allows the calling code to define
the slot size.
---
 core-writer/include/RingBuffer.hpp |  4 ++-
 core-writer/src/RingBuffer.cpp     | 58 +++++++++++++++---------------
 2 files changed, 32 insertions(+), 30 deletions(-)

diff --git a/core-writer/include/RingBuffer.hpp b/core-writer/include/RingBuffer.hpp
index 03dc0bd..14c00b4 100644
--- a/core-writer/include/RingBuffer.hpp
+++ b/core-writer/include/RingBuffer.hpp
@@ -5,6 +5,7 @@
 #include <vector>
 #include <map>
 #include <mutex>
+#include <atomic>
 #include <memory>
 #include <string>
 #include <boost/any.hpp>
@@ -39,7 +40,7 @@ class RingBuffer
     char* frame_data_buffer_ = NULL;
     size_t write_index_ = 0;
     size_t buffer_used_slots_ = 0;
-    bool ring_buffer_initialized_ = false;
+    std::atomic_bool initialized_ = false;
 
     std::list< std::shared_ptr<FrameMetadata> > frame_metadata_queue_;
     std::mutex frame_metadata_queue_mutex_;
@@ -58,6 +59,7 @@ class RingBuffer
         void release(size_t buffer_slot_index);
 
         bool is_empty();
+        bool is_initialized();
         void clear();
         size_t get_slot_size();
 };
diff --git a/core-writer/src/RingBuffer.cpp b/core-writer/src/RingBuffer.cpp
index 11978b6..48d683b 100644
--- a/core-writer/src/RingBuffer.cpp
+++ b/core-writer/src/RingBuffer.cpp
@@ -30,53 +30,48 @@ RingBuffer::~RingBuffer()
 
 void RingBuffer::initialize(size_t slot_size)
 {
-    if (frame_data_buffer_) {
-        stringstream err_msg;
-
-        using namespace date;
-        using namespace chrono; 
-        err_msg << "[" << system_clock::now() << "]";
-        err_msg << "[RingBuffer::initialize]";
-        err_msg << " Ring buffer already initialized." << endl;
-
-        throw runtime_error(err_msg.str());
+    if (initialized_.load(memory_order_relaxed)) {
+        return;
+    }
+
+    lock_guard<mutex> lock(ringbuffer_slots_mutex_);
+
+    if (initialized_) {
+        return;
     }
 
-    #ifdef DEBUG_OUTPUT
-        using namespace date;
-        using namespace chrono; 
-        cout << "[" << system_clock::now() << "]";
-        cout << "[RingBuffer::initialize]";
-        cout << " Initializing ring buffer";
-        cout << " with slot_size " << slot_size << endl;
-    #endif
-    
     write_index_ = 0;
     slot_size_ = slot_size;
     buffer_size_ = slot_size * n_slots_;
     frame_data_buffer_ = new char[buffer_size_];
     buffer_used_slots_ = 0;
-    ring_buffer_initialized_ = true;
+
+    initialized_ = true;
 
     #ifdef DEBUG_OUTPUT
         using namespace date;
-        using namespace chrono; 
+        using namespace chrono;
         cout << "[" << system_clock::now() << "]";
         cout << "[RingBuffer::initialize]";
-        cout << " Total buffer_size " << buffer_size_ << endl;
+        cout << " Ringbuffer initialized";
+        cout << " with slot_size " << slot_size_;
+        cout << " with n_slots " << n_slots_;
+        cout << " and buffer_size " << buffer_size_;
     #endif
 }
 
 char* RingBuffer::reserve(shared_ptr<FrameMetadata> frame_metadata)
 {
-    if (!ring_buffer_initialized_) {
-        {
-            lock_guard<mutex> lock(ringbuffer_slots_mutex_);
+    if (!is_initialized()) {
+        stringstream err_msg;
 
-            if (!ring_buffer_initialized_) {
-                initialize(frame_metadata->frame_bytes_size);
-            }
-        }
+        using namespace date;
+        using namespace chrono;
+        err_msg << "[" << system_clock::now() << "]";
+        err_msg << "[RingBuffer::reserve]";
+        err_msg << " Ringbuffer not initialized.";
+
+        throw runtime_error(err_msg.str());
     }
 
     if (frame_metadata->frame_bytes_size > slot_size_) {
@@ -266,6 +261,11 @@ bool RingBuffer::is_empty()
     return buffer_used_slots_ == 0;
 }
 
+bool RingBuffer::is_initialized()
+{
+    return initialized_.load(memory_order_relaxed);
+}
+
 void RingBuffer::clear()
 {
     lock_guard<mutex> lock_slots(ringbuffer_slots_mutex_);