buffer: use malloc/free to replace fixed array

Signed-off-by: Date Huang <[email protected]>

buffer_pool.cpp

@@ -15,37 +15,34 @@ void watermark_callback(std::vector<std::weak_ptr<libtorrent::disk_observer>> co
 
 buffer_pool::buffer_pool(libtorrent::io_context &ioc) :
 	m_ios(ioc),
+	m_size(0),
 	m_exceeded_max_size(false)
 {
-	m_buffer = new char[MAX_BUFFER_POOL_SIZE];
-
-	// put into deque
-	for (int i = 0; i < MAX_BUFFER_POOL_SIZE; i += DEFAULT_BLOCK_SIZE) {
-		m_deque.push_back(m_buffer + i);
-	}
 }
 
 buffer_pool::~buffer_pool()
 {
-	m_deque.clear();
-	delete m_buffer;
 }
 
 char *buffer_pool::allocate_buffer_impl(std::unique_lock<std::mutex> &l)
 {
 	// no memory
-	if (m_deque.empty()) {
+	if (m_size >= BUFFER_COUNT) {
 		m_exceeded_max_size = true;
 		return nullptr;
 	}
 
 	// reach high watermak, but still has some buffer to use
-	if (BUFFER_COUNT - m_deque.size() > HIGH_WATERMARK) {
+	if (m_size > HIGH_WATERMARK) {
 		m_exceeded_max_size = true;
 	}
 
-	char *buf = m_deque.front();
-	m_deque.pop_front();
+	char *buf = (char*)malloc(DEFAULT_BLOCK_SIZE);
+	if (!buf) {
+		m_exceeded_max_size = true;
+		return nullptr;
+	}
+	m_size++;
 	return buf;
 }
 
@@ -73,13 +70,14 @@ char *buffer_pool::allocate_buffer(bool &exceeded, std::shared_ptr<libtorrent::d
 void buffer_pool::free_disk_buffer(char *buf)
 {
 	std::unique_lock<std::mutex> l(m_pool_mutex);
-	m_deque.push_back(buf);
+	free(buf);
+	m_size--;
 	check_buffer_level(l);
 }
 
 void buffer_pool::check_buffer_level(std::unique_lock<std::mutex> &l)
 {
-	if (!m_exceeded_max_size || BUFFER_COUNT - m_deque.size() > LOW_WATERMARK) {
+	if (!m_exceeded_max_size || m_size > LOW_WATERMARK) {
 		// still high usgae
 		return;
 	}

buffer_pool.hpp

@@ -7,7 +7,7 @@
 #include <boost/core/noncopyable.hpp>
 #include <libtorrent/libtorrent.hpp>
 
-// 16 MB
+// 256 MB
 #define MAX_BUFFER_POOL_SIZE (16ULL * 1024 * 1024)
 // 16 KB
 #define DEFAULT_BLOCK_SIZE (16 * 1024)
@@ -36,8 +36,7 @@ class buffer_pool : public libtorrent::buffer_allocator_interface, boost::noncop
 private:
 	libtorrent::io_context &m_ios;
 	std::mutex m_pool_mutex;
-	char *m_buffer;
-	std::deque<char *> m_deque;
+	int m_size;
 	bool m_exceeded_max_size;
 	std::vector<std::weak_ptr<libtorrent::disk_observer>> m_observers;
 };