SinkImpl: Refactor GetDescription, add GetError, SetEnabled.

src/MJPEGServerImpl.cpp

@@ -332,20 +332,14 @@ void MJPEGServerImpl::SendJSON(llvm::raw_ostream& os, SourceImpl& source,
 MJPEGServerImpl::MJPEGServerImpl(llvm::StringRef name,
                                  llvm::StringRef description,
                                  std::unique_ptr<wpi::NetworkAcceptor> acceptor)
-    : SinkImpl{name},
-      m_description(description),
-      m_acceptor{std::move(acceptor)} {
+    : SinkImpl{name}, m_acceptor{std::move(acceptor)} {
   m_active = true;
+  SetDescription(description);
   m_serverThread = std::thread(&MJPEGServerImpl::ServerThreadMain, this);
 }
 
 MJPEGServerImpl::~MJPEGServerImpl() { Stop(); }
 
-llvm::StringRef MJPEGServerImpl::GetDescription(
-    llvm::SmallVectorImpl<char>& buf) const {
-  return m_description;
-}
-
 void MJPEGServerImpl::Stop() {
   m_active = false;
 

src/MJPEGServerImpl.h

@@ -9,9 +9,7 @@
 #define CAMERASERVER_MJPEGSERVERIMPL_H_
 
 #include <atomic>
-#include <condition_variable>
 #include <memory>
-#include <mutex>
 #include <thread>
 #include <vector>
 
@@ -35,9 +33,6 @@ class MJPEGServerImpl : public SinkImpl {
                   std::unique_ptr<wpi::NetworkAcceptor> acceptor);
   ~MJPEGServerImpl() override;
 
-  llvm::StringRef GetDescription(
-      llvm::SmallVectorImpl<char>& buf) const override;
-
   void Stop();
 
   static void SendHeader(llvm::raw_ostream& os, int code,
@@ -59,13 +54,10 @@ class MJPEGServerImpl : public SinkImpl {
   void ServerThreadMain();
   void ConnThreadMain(wpi::NetworkStream* stream);
 
-  std::string m_description;
-
   std::unique_ptr<wpi::NetworkAcceptor> m_acceptor;
   std::atomic_bool m_active;  // set to false to terminate threads
   std::thread m_serverThread;
 
-  std::mutex m_mutex;
   std::vector<std::thread> m_connThreads;
   std::vector<std::unique_ptr<wpi::NetworkStream>> m_connStreams;
 };

src/SinkImpl.cpp

@@ -20,6 +20,18 @@ SinkImpl::~SinkImpl() {
   }
 }
 
+void SinkImpl::SetDescription(llvm::StringRef description) {
+  std::lock_guard<std::mutex> lock(m_mutex);
+  m_description = description;
+}
+
+llvm::StringRef SinkImpl::GetDescription(
+    llvm::SmallVectorImpl<char>& buf) const {
+  std::lock_guard<std::mutex> lock(m_mutex);
+  buf.append(m_description.begin(), m_description.end());
+  return llvm::StringRef{buf.data(), buf.size()};
+}
+
 void SinkImpl::SetSource(std::shared_ptr<SourceImpl> source) {
   std::lock_guard<std::mutex> lock(m_mutex);
   if (m_source) {
@@ -30,3 +42,20 @@ void SinkImpl::SetSource(std::shared_ptr<SourceImpl> source) {
   m_source->AddSink();
   if (m_enabledCount > 0) m_source->EnableSink();
 }
+
+std::string SinkImpl::GetError() const {
+  std::lock_guard<std::mutex> lock(m_mutex);
+  if (!m_source) return "no source connected";
+  auto frame = m_source->GetCurFrame();
+  if (frame) return std::string{};  // no error
+  return llvm::StringRef{frame};
+}
+
+llvm::StringRef SinkImpl::GetError(llvm::SmallVectorImpl<char>& buf) const {
+  std::lock_guard<std::mutex> lock(m_mutex);
+  if (!m_source) return "no source connected";
+  auto frame = m_source->GetCurFrame();
+  if (frame) return llvm::StringRef{};  // no error
+  buf.append(frame.data(), frame.data() + frame.size());
+  return llvm::StringRef{buf.data(), buf.size()};
+}

src/SinkImpl.h

@@ -28,8 +28,9 @@ class SinkImpl {
   SinkImpl& operator=(const SinkImpl& queue) = delete;
 
   llvm::StringRef GetName() const { return m_name; }
-  virtual llvm::StringRef GetDescription(
-      llvm::SmallVectorImpl<char>& buf) const = 0;
+
+  void SetDescription(llvm::StringRef description);
+  llvm::StringRef GetDescription(llvm::SmallVectorImpl<char>& buf) const;
 
   void Enable() {
     std::lock_guard<std::mutex> lock(m_mutex);
@@ -43,6 +44,17 @@ class SinkImpl {
     if (m_enabledCount == 0 && m_source) m_source->DisableSink();
   }
 
+  void SetEnabled(bool enabled) {
+    std::lock_guard<std::mutex> lock(m_mutex);
+    if (enabled && m_enabledCount == 0) {
+      if (m_source) m_source->EnableSink();
+      m_enabledCount = 1;
+    } else if (!enabled && m_enabledCount > 0) {
+      if (m_source) m_source->DisableSink();
+      m_enabledCount = 0;
+    }
+  }
+
   void SetSource(std::shared_ptr<SourceImpl> source);
 
   std::shared_ptr<SourceImpl> GetSource() const {
@@ -50,9 +62,15 @@ class SinkImpl {
     return m_source;
   }
 
+  std::string GetError() const;
+  llvm::StringRef GetError(llvm::SmallVectorImpl<char>& buf) const;
+
+ protected:
+  mutable std::mutex m_mutex;
+
  private:
   std::string m_name;
-  mutable std::mutex m_mutex;
+  std::string m_description;
   std::shared_ptr<SourceImpl> m_source;
   int m_enabledCount{0};
 };