From c46f3d2227bd7b2c59061f9c6f9d84ad1a8d644e Mon Sep 17 00:00:00 2001
From: Babicaa <andrej.babic@psi.ch>
Date: Tue, 30 Apr 2019 15:46:48 +0200
Subject: [PATCH] Split ringbuffer write to reserve and commit

Since the introduction of compression, it is no longer practival to do a manual memcopy int he
ringbuffer write method. In order to save a memory copy, the ringbuffer does not copy the buffer
itself, but the compression is done directly to the ringbuffer slot.
---
 lib/src/RingBuffer.cpp | 30 ++++++++++--------------------
 lib/src/RingBuffer.hpp |  3 ++-
 2 files changed, 12 insertions(+), 21 deletions(-)

diff --git a/lib/src/RingBuffer.cpp b/lib/src/RingBuffer.cpp
index 1f2238b..3887870 100644
--- a/lib/src/RingBuffer.cpp
+++ b/lib/src/RingBuffer.cpp
@@ -64,7 +64,7 @@ void RingBuffer::initialize(size_t slot_size)
     #endif
 }
 
-void RingBuffer::write(shared_ptr<FrameMetadata> frame_metadata, const char* data)
+char* RingBuffer::reserve(shared_ptr<FrameMetadata> frame_metadata)
 {
     if (!ring_buffer_initialized) {
         initialize(frame_metadata->frame_bytes_size);
@@ -77,7 +77,7 @@ void RingBuffer::write(shared_ptr<FrameMetadata> frame_metadata, const char* dat
         using namespace date;
         using namespace chrono; 
         error_message << "[" << system_clock::now() << "]";
-        error_message << "[RingBuffer::write] Received frame index ";
+        error_message << "[RingBuffer::reserve] Received frame index ";
         error_message << frame_metadata->frame_index;
         error_message << " that is too large for ring buffer slot. ";
         error_message << "Slot size " << slot_size << ", but frame bytes size ";
@@ -99,7 +99,7 @@ void RingBuffer::write(shared_ptr<FrameMetadata> frame_metadata, const char* dat
                 using namespace date;
                 using namespace chrono; 
                 cout << "[" << system_clock::now() << "]";
-                cout << "[RingBuafer::write] Ring buffer slot ";
+                cout << "[RingBuafer::reserve] Ring buffer slot ";
                 cout << frame_metadata->buffer_slot_index;
                 cout << " reserved for frame_index ";
                 cout << frame_metadata->frame_index << endl;
@@ -114,7 +114,7 @@ void RingBuffer::write(shared_ptr<FrameMetadata> frame_metadata, const char* dat
             using namespace date;
             using namespace chrono; 
             error_message << "[" << system_clock::now() << "]";
-            error_message << "[RingBuffer::write] Ring buffer is full.";
+            error_message << "[RingBuffer::reserve] Ring buffer is full.";
             error_message << " Collision at write_index = " << write_index << endl;
 
             throw runtime_error(error_message.str());
@@ -122,24 +122,14 @@ void RingBuffer::write(shared_ptr<FrameMetadata> frame_metadata, const char* dat
     }
 
     // The slot is already reserved, no need for synchronization.
-    char* slot_memory_address = get_buffer_slot_address(frame_metadata->buffer_slot_index);
-    memcpy(slot_memory_address, data, frame_metadata->frame_bytes_size);
+    return get_buffer_slot_address(frame_metadata->buffer_slot_index);
+}
 
-    #ifdef DEBUG_OUTPUT
-        using namespace date;
-        using namespace chrono; 
-        cout << "[" << system_clock::now() << "]";
-        cout << "[RingBuffer::write] Copied " << frame_metadata->frame_bytes_size;
-        cout << " frame bytes to buffer_slot_index ";
-        cout << frame_metadata->buffer_slot_index << endl;
-    #endif
+void RingBuffer::commit(shared_ptr<FrameMetadata> frame_metadata)
+{
+    lock_guard<mutex> lock(frame_metadata_queue_mutex);
 
-    // Add metadata header to the inter-thread communication queue.
-    {
-        lock_guard<mutex> lock(frame_metadata_queue_mutex);
-
-        frame_metadata_queue.push_back(frame_metadata);
-    }
+    frame_metadata_queue.push_back(frame_metadata);
 
     #ifdef DEBUG_OUTPUT
         using namespace date;
diff --git a/lib/src/RingBuffer.hpp b/lib/src/RingBuffer.hpp
index dd50433..163744f 100644
--- a/lib/src/RingBuffer.hpp
+++ b/lib/src/RingBuffer.hpp
@@ -52,7 +52,8 @@ class RingBuffer
         virtual ~RingBuffer();
         void initialize(size_t slot_size);
         
-        void write(const std::shared_ptr<FrameMetadata> metadata, const char* data);
+        char* reserve(std::shared_ptr<FrameMetadata> metadata);
+        void commit(std::shared_ptr<FrameMetadata> metadata);
         std::pair<std::shared_ptr<FrameMetadata>, char*> read();
         void release(size_t buffer_slot_index);
         bool is_empty();