pre allocate async q memory

include/spdlog/details/circular_q.h

+//
+// Copyright(c) 2018 Gabi Melman.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+//
+
+// cirucal q view of std::vector.
+#pragma once
+
+namespace spdlog {
+namespace details {
+template<typename T>
+class circular_q
+{
+public:
+    using item_type = T;
+
+    explicit circular_q(size_t max_items)
+        : max_items_(max_items + 1)
+        , v_(max_items_)
+    {
+    }
+
+    // push back, overrun last item if no room left
+    void push_back(T &&item)
+    {
+        v_[head_] = std::move(item);
+        head_ = (head_ + 1) % max_items_;
+
+        if (head_ == tail_)
+        {
+            tail_ = (tail_ + 1) % max_items_;
+        }
+    }
+
+    // Pop item from front.
+    // If there are no elements in the container, the behavior is undefined.
+    void pop_front(T &popped_item)
+    {
+        popped_item = std::move(v_[tail_]);
+        tail_ = (tail_ + 1) % max_items_;
+    }
+
+    bool empty()
+    {
+        return head_ == tail_;
+    }
+
+    bool full()
+    {
+        // tail is ahead of the head by 1
+        return ((head_ + 1) % max_items_) == tail_;
+    }
+
+private:
+    size_t max_items_;
+    typename std::vector<T>::size_type head_ = 0;
+    typename std::vector<T>::size_type tail_ = 0;
+    std::vector<T> v_;
+};
+} // namespace details
+} // namespace spdlog
\ No newline at end of file

include/spdlog/details/fmt_helper.h

@@ -24,9 +24,10 @@ inline void append_c_str(const char *c_str, fmt::memory_buffer &dest)
     }
 }
 
-inline void append_buf(const fmt::memory_buffer &buf, fmt::memory_buffer &dest)
+template<size_t N1, size_t N2>
+inline void append_buf(const fmt::basic_memory_buffer<char, N1> &buf, fmt::basic_memory_buffer<char, N2> &dest)
 {
-    const char *buf_ptr = buf.data();
+    auto *buf_ptr = buf.data();
     dest.append(buf_ptr, buf_ptr + buf.size());
 }
 

include/spdlog/details/mpmc_blocking_q.h

@@ -5,15 +5,15 @@
 // Distributed under the MIT License (http://opensource.org/licenses/MIT)
 //
 
-// async log helper :
-// multi producer-multi consumer blocking queue
-// enqueue(..) - will block until room found to put the new message
-// enqueue_nowait(..) - will return immediatly with false if no room left in the queue
-// dequeue_for(..) - will block until the queue is not empty or timeout passed
+// multi producer-multi consumer blocking queue.
+// enqueue(..) - will block until room found to put the new message.
+// enqueue_nowait(..) - will return immediately with false if no room left in the queue.
+// dequeue_for(..) - will block until the queue is not empty or timeout have passed.
+
+#include "spdlog/details/circular_q.h"
 
 #include <condition_variable>
 #include <mutex>
-#include <queue>
 
 namespace spdlog {
 namespace details {
@@ -24,7 +24,7 @@ class mpmc_blocking_queue
 public:
     using item_type = T;
     explicit mpmc_blocking_queue(size_t max_items)
-        : max_items_(max_items)
+        : q_(max_items)
     {
     }
 
@@ -33,22 +33,22 @@ public:
     {
         {
             std::unique_lock<std::mutex> lock(queue_mutex_);
-            pop_cv_.wait(lock, [this] { return this->q_.size() < this->max_items_; });
-            q_.push(std::move(item));
+            pop_cv_.wait(lock, [this] { return !this->q_.full(); });
+            q_.push_back(std::move(item));
         }
         push_cv_.notify_one();
     }
 
-    // try to enqueue and return immdeialty false if no room left
+    // try to enqueue and return immediately false if no room left
     bool enqueue_nowait(T &&item)
     {
         {
             std::unique_lock<std::mutex> lock(queue_mutex_);
-            if (q_.size() == this->max_items_)
+            if (q_.full())
             {
                 return false;
             }
-            q_.push(std::forward<T>(item));
+            q_.push_back(std::forward<T>(item));
         }
         push_cv_.notify_one();
         return true;
@@ -60,25 +60,23 @@ public:
     {
         {
             std::unique_lock<std::mutex> lock(queue_mutex_);
-            if (!push_cv_.wait_for(lock, wait_duration, [this] { return this->q_.size() > 0; }))
+            if (!push_cv_.wait_for(lock, wait_duration, [this] { return !this->q_.empty(); }))
             {
                 return false;
             }
 
-            popped_item = std::move(q_.front());
-            q_.pop();
+            q_.pop_front(popped_item);
         }
         pop_cv_.notify_one();
         return true;
     }
 
 private:
-    size_t max_items_;
     std::mutex queue_mutex_;
     std::condition_variable push_cv_;
     std::condition_variable pop_cv_;
 
-    std::queue<T> q_;
+    spdlog::details::circular_q<T> q_;
 };
 } // namespace details
 } // namespace spdlog

include/spdlog/formatter.h

@@ -8,7 +8,6 @@
 #include "fmt/fmt.h"
 #include "spdlog/details/log_msg.h"
 
-
 namespace spdlog {
 
 class formatter