Add pull_frame(timeout)

Instead of blocking until the library is destroyed, add ability
to block at most N milliseconds before returning.

The code returns early if a frame is received within the specified
timeframe but will block at most "timeout "milliseconds

include/media_stream.hh

@@ -84,8 +84,13 @@ namespace uvg_rtp {
              * NOTE: pull_frame() is a blocking operation and a separate thread should be
              * spawned for it!
              *
+             * You can specify for how long should pull_frame() block by giving "timeout"
+             * parameter that denotes how long pull_frame() will wait for an incoming frame
+             * in milliseconds
+             *
              * Return pointer to RTP frame on success */
             uvg_rtp::frame::rtp_frame *pull_frame();
+            uvg_rtp::frame::rtp_frame *pull_frame(size_t timeout);
 
             /* Alternative to pull_frame(). The provided hook is called when a frame is received.
              *

include/receiver.hh

@@ -28,6 +28,9 @@ namespace uvg_rtp {
             /* NOTE: this operation is blocking */
             uvg_rtp::frame::rtp_frame *pull_frame();
 
+            /* Block at most "timeout" milliseconds and return nullptr if nothing was received */
+            uvg_rtp::frame::rtp_frame *pull_frame(size_t timeout);
+
             /* Open socket, start frame receiver and RTCP
              *
              * Return RTP_OK on success

src/media_stream.cc

@@ -223,6 +223,17 @@ uvg_rtp::frame::rtp_frame *uvg_rtp::media_stream::pull_frame()
     return receiver_->pull_frame();
 }
 
+uvg_rtp::frame::rtp_frame *uvg_rtp::media_stream::pull_frame(size_t timeout)
+{
+    if (!initialized_) {
+        LOG_ERROR("RTP context has not been initialized fully, cannot continue!");
+        rtp_errno = RTP_NOT_INITIALIZED;
+        return nullptr;
+    }
+
+    return receiver_->pull_frame(timeout);
+}
+
 rtp_error_t uvg_rtp::media_stream::install_receive_hook(void *arg, void (*hook)(void *, uvg_rtp::frame::rtp_frame *))
 {
     if (!initialized_) {

src/receiver.cc

@@ -84,6 +84,27 @@ uvg_rtp::frame::rtp_frame *uvg_rtp::receiver::pull_frame()
     return frame;
 }
 
+uvg_rtp::frame::rtp_frame *uvg_rtp::receiver::pull_frame(size_t timeout)
+{
+    while (frames_.empty() && this->active() && timeout) {
+        std::this_thread::sleep_for(std::chrono::milliseconds(1));
+        --timeout;
+    }
+
+    if (!this->active())
+        return nullptr;
+
+    if (frames_.empty())
+        return nullptr;
+
+    frames_mtx_.lock();
+    auto frame = frames_.front();
+    frames_.erase(frames_.begin());
+    frames_mtx_.unlock();
+
+    return frame;
+}
+
 uint8_t *uvg_rtp::receiver::get_recv_buffer() const
 {
     return recv_buf_;