server: introduce supposedly lighterweight is_alive in httplib (yhirose/cpp-httplib#1956)

Author: ochafik

examples/server/httplib.h

@@ -457,6 +457,7 @@ class DataSink {
 
   std::function<bool(const char *data, size_t data_len)> write;
   std::function<bool()> is_writable;
+  std::function<bool()> is_alive;
   std::function<void()> done;
   std::function<void(const Headers &trailer)> done_with_trailer;
   std::ostream os;
@@ -639,6 +640,7 @@ class Stream {
 
   virtual bool is_readable() const = 0;
   virtual bool is_writable() const = 0;
+  virtual bool is_alive() const = 0;
 
   virtual ssize_t read(char *ptr, size_t size) = 0;
   virtual ssize_t write(const char *ptr, size_t size) = 0;
@@ -2135,6 +2137,7 @@ class BufferStream final : public Stream {
 
   bool is_readable() const override;
   bool is_writable() const override;
+  bool is_alive() const override;
   ssize_t read(char *ptr, size_t size) override;
   ssize_t write(const char *ptr, size_t size) override;
   void get_remote_ip_and_port(std::string &ip, int &port) const override;
@@ -2945,6 +2948,7 @@ class SocketStream final : public Stream {
 
   bool is_readable() const override;
   bool is_writable() const override;
+  bool is_alive() const override;
   ssize_t read(char *ptr, size_t size) override;
   ssize_t write(const char *ptr, size_t size) override;
   void get_remote_ip_and_port(std::string &ip, int &port) const override;
@@ -2975,6 +2979,7 @@ class SSLSocketStream final : public Stream {
 
   bool is_readable() const override;
   bool is_writable() const override;
+  bool is_alive() const override;
   ssize_t read(char *ptr, size_t size) override;
   ssize_t write(const char *ptr, size_t size) override;
   void get_remote_ip_and_port(std::string &ip, int &port) const override;
@@ -4088,6 +4093,7 @@ inline bool write_content(Stream &strm, const ContentProvider &content_provider,
   };
 
   data_sink.is_writable = [&]() -> bool { return strm.is_writable(); };
+  data_sink.is_alive = [&]() -> bool { return strm.is_alive(); };
 
   while (offset < end_offset && !is_shutting_down()) {
     if (!strm.is_writable()) {
@@ -4134,6 +4140,7 @@ write_content_without_length(Stream &strm,
   };
 
   data_sink.is_writable = [&]() -> bool { return strm.is_writable(); };
+  data_sink.is_alive = [&]() -> bool { return strm.is_alive(); };
 
   data_sink.done = [&](void) { data_available = false; };
 
@@ -4186,6 +4193,7 @@ write_content_chunked(Stream &strm, const ContentProvider &content_provider,
   };
 
   data_sink.is_writable = [&]() -> bool { return strm.is_writable(); };
+  data_sink.is_alive = [&]() -> bool { return strm.is_alive(); };
 
   auto done_with_trailer = [&](const Headers *trailer) {
     if (!ok) { return; }
@@ -5484,6 +5492,10 @@ inline bool SocketStream::is_writable() const {
          is_socket_alive(sock_);
 }
 
+inline bool SocketStream::is_alive() const {
+  return is_socket_alive(sock_);
+}
+
 inline ssize_t SocketStream::read(char *ptr, size_t size) {
 #ifdef _WIN32
   size =
@@ -5558,6 +5570,8 @@ inline bool BufferStream::is_readable() const { return true; }
 
 inline bool BufferStream::is_writable() const { return true; }
 
+inline bool BufferStream::is_alive() const { return true; }
+
 inline ssize_t BufferStream::read(char *ptr, size_t size) {
 #if defined(_MSC_VER) && _MSC_VER < 1910
   auto len_read = buffer._Copy_s(ptr, size, size, position);
@@ -8348,6 +8362,10 @@ inline bool SSLSocketStream::is_writable() const {
          is_socket_alive(sock_);
 }
 
+inline bool SSLSocketStream::is_alive() const {
+  return is_socket_alive(sock_);
+}
+
 inline ssize_t SSLSocketStream::read(char *ptr, size_t size) {
   if (SSL_pending(ssl_) > 0) {
     return SSL_read(ssl_, ptr, static_cast<int>(size));

examples/server/server.cpp

@@ -2445,15 +2445,15 @@ static void handle_tasks(
     };
     if (!stream) {
         res.set_content_provider(MIMETYPE_JSON, [create_tasks, payload, state, &ctx_server](size_t, httplib::DataSink & sink) {
-            auto is_alive = [&sink]() { return sink.is_writable(); };
+            auto is_alive = [&sink]() { return sink.is_alive(); };
             state->task_ids = create_tasks(is_alive);
             payload(state->task_ids, sink);
             ctx_server.queue_results.remove_waiting_task_ids(state->task_ids);
             return false;
         }, resource_releaser);
     } else {
         res.set_chunked_content_provider("text/event-stream", [create_tasks, payload, state, &ctx_server](size_t, httplib::DataSink & sink) {
-            auto is_alive = [&sink]() { return sink.is_writable(); };
+            auto is_alive = [&sink]() { return sink.is_alive(); };
             state->task_ids = create_tasks(is_alive);
             payload(state->task_ids, sink);
             ctx_server.queue_results.remove_waiting_task_ids(state->task_ids);