From 3dc21c0378e672f6df1f96da48e49ec845a8a211 Mon Sep 17 00:00:00 2001
From: John Zhao <johnzhao@slightech.com>
Date: Wed, 11 Jul 2018 15:04:14 +0800
Subject: [PATCH] Limit max data size for async callback

---
 src/device/device.cc               | 5 +++--
 src/internal/async_callback.h      | 5 +++--
 src/internal/async_callback_impl.h | 8 +++++---
 3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/src/device/device.cc b/src/device/device.cc
index a672ffc..cbfb64c 100644
--- a/src/device/device.cc
+++ b/src/device/device.cc
@@ -335,7 +335,7 @@ void Device::SetStreamCallback(
     if (async)
       stream_async_callbacks_[stream] =
           std::make_shared<stream_async_callback_t>(
-              to_string(stream), callback);
+              to_string(stream), callback);  // max_data_size = 1
   } else {
     stream_callbacks_.erase(stream);
     stream_async_callbacks_.erase(stream);
@@ -347,7 +347,8 @@ void Device::SetMotionCallback(motion_callback_t callback, bool async) {
   if (callback) {
     if (async)
       motion_async_callback_ =
-          std::make_shared<motion_async_callback_t>("motion", callback, true);
+          std::make_shared<motion_async_callback_t>("motion", callback, 1000);
+    // will drop old motion datas after callback cost > 2 s (1000 / 500 Hz)
   } else {
     motion_async_callback_ = nullptr;
   }
diff --git a/src/internal/async_callback.h b/src/internal/async_callback.h
index 43944d2..c00f4b4 100644
--- a/src/internal/async_callback.h
+++ b/src/internal/async_callback.h
@@ -31,7 +31,8 @@ class AsyncCallback {
  public:
   using callback_t = std::function<void(Data data)>;
 
-  AsyncCallback(std::string name, callback_t callback, bool concat = false);
+  AsyncCallback(
+      std::string name, callback_t callback, std::size_t max_data_size = 0);
   ~AsyncCallback();
 
   void PushData(Data data);
@@ -50,8 +51,8 @@ class AsyncCallback {
   std::thread thread_;
 
   std::uint32_t count_;
-  bool concat_;
   std::vector<Data> datas_;
+  std::size_t max_data_size_;
 };
 
 MYNTEYE_END_NAMESPACE
diff --git a/src/internal/async_callback_impl.h b/src/internal/async_callback_impl.h
index 23f8ead..3c502b3 100644
--- a/src/internal/async_callback_impl.h
+++ b/src/internal/async_callback_impl.h
@@ -24,11 +24,11 @@ MYNTEYE_BEGIN_NAMESPACE
 
 template <class Data>
 AsyncCallback<Data>::AsyncCallback(
-    std::string name, callback_t callback, bool concat)
+    std::string name, callback_t callback, std::size_t max_data_size)
     : name_(std::move(name)),
       callback_(std::move(callback)),
       count_(0),
-      concat_(concat) {
+      max_data_size_(max_data_size) {
   VLOG(2) << __func__;
   running_ = true;
   thread_ = std::thread(&AsyncCallback<Data>::Run, this);
@@ -51,8 +51,10 @@ AsyncCallback<Data>::~AsyncCallback() {
 template <class Data>
 void AsyncCallback<Data>::PushData(Data data) {
   std::lock_guard<std::mutex> _(mtx_);
-  if (!concat_) {
+  if (max_data_size_ <= 0) {
     datas_.clear();
+  } else if (max_data_size_ == datas_.size()) {  // >= 1
+    datas_.erase(datas_.begin());
   }
   datas_.push_back(data);
   ++count_;