Lockguards in RingBuffer

src/RingBuffer.cpp

@@ -68,35 +68,35 @@ void RingBuffer::write(FrameMetadata &frame_metadata, const char* data)
     }
 
     // Check and reserve slot in the buffer.
-    ringbuffer_slots_mutex.lock();
+    {
+        lock_guard<mutex> lock(ringbuffer_slots_mutex);
 
-    if (!ringbuffer_slots[write_index]) {
-        ringbuffer_slots[write_index] = 1;
-        
-        // Set the write index in the FrameMetadata object.
-        frame_metadata.buffer_slot_index = write_index;
+        if (!ringbuffer_slots[write_index]) {
+            ringbuffer_slots[write_index] = 1;
+            
+            // Set the write index in the FrameMetadata object.
+            frame_metadata.buffer_slot_index = write_index;
 
-        #ifdef DEBUG_OUTPUT
-            cout << "[RingBuffer::write] Ring buffer slot " << frame_metadata.buffer_slot_index << " reserved for frame_index ";
-            cout << frame_metadata.frame_index << endl;
-        #endif
+            #ifdef DEBUG_OUTPUT
+                cout << "[RingBuffer::write] Ring buffer slot " << frame_metadata.buffer_slot_index << " reserved for frame_index ";
+                cout << frame_metadata.frame_index << endl;
+            #endif
 
-        // Increase and wrap the write index around if needed.
-        write_index = (write_index + 1) % n_slots;
+            // Increase and wrap the write index around if needed.
+            write_index = (write_index + 1) % n_slots;
 
-        // Keep track of the number of used slots.
-        buffer_used_slots++;
+            // Keep track of the number of used slots.
+            buffer_used_slots++;
 
-    } else {
-        stringstream error_message;
-        error_message << "[RingBuffer::write] Ring buffer is full. Collision at write_index = " << write_index << endl;
+        } else {
+            stringstream error_message;
+            error_message << "[RingBuffer::write] Ring buffer is full. Collision at write_index = " << write_index << endl;
 
-        throw runtime_error(error_message.str());
+            throw runtime_error(error_message.str());
+        }
     }
 
-    ringbuffer_slots_mutex.unlock();
-
-    // Write to the buffer. The slot is already reserved.
+    // 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);
 
@@ -104,13 +104,13 @@ void RingBuffer::write(FrameMetadata &frame_metadata, const char* data)
         cout << "[RingBuffer::write] Copied " << frame_metadata.frame_bytes_size << " frame bytes to buffer_slot_index ";
         cout << frame_metadata.buffer_slot_index << endl;
     #endif
-    
-    frame_metadata_queue_mutex.lock();
 
-    // Send the metadata header to writing process.
-    frame_metadata_queue.push_back(frame_metadata);
+    // Add metadata header to the inter-thread communication queue.
+    {
+        lock_guard<mutex> lock(frame_metadata_queue_mutex);
 
-    frame_metadata_queue_mutex.unlock();
+        frame_metadata_queue.push_back(frame_metadata);
+    }
 
     #ifdef DEBUG_OUTPUT
         cout << "[RingBuffer::write] Metadata for frame_index " << frame_metadata.frame_index << " added to metadata queue." << endl;
@@ -142,37 +142,37 @@ pair<FrameMetadata, char*> RingBuffer::read()
 {
     FrameMetadata frame_metadata;
 
-    frame_metadata_queue_mutex.lock();
+    // Read data from the metadata queue.
+    {
+        lock_guard<mutex> lock(frame_metadata_queue_mutex);
 
-    if (frame_metadata_queue.empty()) {
-        frame_metadata_queue_mutex.unlock();
+        // A NULL char* indicates that there are no available data in the ring buffer.
+        if (frame_metadata_queue.empty()) {
+            return {frame_metadata, NULL};
+        }
 
-        return {frame_metadata, NULL};
+        frame_metadata = frame_metadata_queue.front();
+        frame_metadata_queue.pop_front();
     }
 
-    frame_metadata = frame_metadata_queue.front();
-    frame_metadata_queue.pop_front();
-
-    frame_metadata_queue_mutex.unlock();
-
     #ifdef DEBUG_OUTPUT
         cout << "[RingBuffer::read] Received metadata for frame_index " << frame_metadata.frame_index << endl;
     #endif
 
     // Check if the references ring buffer slot is valid.
-    ringbuffer_slots_mutex.lock();
+    {
+        lock_guard<mutex> lock(ringbuffer_slots_mutex);
 
-    if (!ringbuffer_slots[frame_metadata.buffer_slot_index]) {
-        stringstream error_message;
-        error_message << "[RingBuffer::read] Ring buffer slot referenced in message header ";
-        error_message << frame_metadata.buffer_slot_index << " is empty." << endl;
+        if (!ringbuffer_slots[frame_metadata.buffer_slot_index]) {
+            stringstream error_message;
+            error_message << "[RingBuffer::read] Ring buffer slot referenced in message header ";
+            error_message << frame_metadata.buffer_slot_index << " is empty." << endl;
 
-        throw runtime_error(error_message.str());
+            throw runtime_error(error_message.str());
+        }
+        
     }
 
-    ringbuffer_slots_mutex.unlock();
-
-    // Memory address of frame in buffer.
     char* slot_memory_address = get_buffer_slot_address(frame_metadata.buffer_slot_index);
             
     return {frame_metadata, slot_memory_address};
@@ -210,10 +210,7 @@ void RingBuffer::release(size_t buffer_slot_index)
 
 bool RingBuffer::is_empty()
 {
-    ringbuffer_slots_mutex.lock();
-
-    bool is_empty = buffer_used_slots == 0;
-
-    ringbuffer_slots_mutex.unlock();
-    return is_empty;
+    lock_guard<mutex> lock(ringbuffer_slots_mutex);
+    
+    return buffer_used_slots == 0;
 }

src/RingBuffer.hpp

@@ -25,7 +25,7 @@ struct FrameMetadata
     
     // Image header data.
     uint64_t frame_index = 0;
-    std::string endianness = "";
+    std::string endianness;
     std::string type;
     size_t frame_shape[2];
 };
@@ -59,7 +59,6 @@ class RingBuffer
         std::pair<FrameMetadata, char*> read();
         void release(size_t buffer_slot_index);
         bool is_empty();
-        
 };
 
 #endif