Only write to remote socket when we know they are writable

Buffer data (in an horribly innefficient way for now), and use the
event manager to watch for the socket being ready for a write.

Fixes #945

src/file.cc

@@ -143,6 +143,16 @@ bool fd_readable(int fd)
     return select(fd+1, &rfds, nullptr, nullptr, &tv) == 1;
 }
 
+bool fd_writable(int fd)
+{
+    fd_set  rfds;
+    FD_ZERO(&rfds);
+    FD_SET(fd, &rfds);
+
+    timeval tv{0,0};
+    return select(fd+1, nullptr, &rfds, nullptr, &tv) == 1;
+}
+
 String read_fd(int fd, bool text)
 {
     String content;

src/file.hh

@@ -30,6 +30,7 @@ std::pair<StringView, StringView> split_path(StringView path);
 String get_kak_binary_path();
 
 bool fd_readable(int fd);
+bool fd_writable(int fd);
 String read_fd(int fd, bool text = false);
 String read_file(StringView filename, bool text = false);
 void write(int fd, StringView data);

src/remote.cc

@@ -42,7 +42,8 @@ enum class MessageType : char
 class MsgWriter
 {
 public:
-    MsgWriter(int sock, MessageType type) : m_socket(sock)
+    MsgWriter(RemoteBuffer& buffer, MessageType type)
+        : m_buffer{buffer}, m_start{(uint32_t)buffer.size()}
     {
         write(type);
         write((uint32_t)0); // message size, to be patched on write
@@ -50,23 +51,13 @@ public:
 
     ~MsgWriter() noexcept(false)
     {
-        uint32_t count = (uint32_t)m_stream.size();
+        uint32_t count = (uint32_t)m_buffer.size() - m_start;
-        char* data = m_stream.data();
+        *reinterpret_cast<uint32_t*>(m_buffer.data() + m_start + 1) = count;
-        *reinterpret_cast<uint32_t*>(data+1) = count;
-        while (count > 0)
-        {
-            int res = ::write(m_socket, data, count);
-            if (res <= 0)
-                throw remote_error{res ? "peer disconnected"
-                                       : format("socket write failed: {}", strerror(errno))};
-            data += res;
-            count -= res;
-        }
     }
 
     void write(const char* val, size_t size)
     {
-        m_stream.insert(m_stream.end(), val, val + size);
+        m_buffer.insert(m_buffer.end(), val, val + size);
     }
 
     template<typename T>
@@ -139,8 +130,8 @@ public:
     }
 
 private:
-    Vector<char, MemoryDomain::Remote> m_stream;
+    RemoteBuffer& m_buffer;
-    int m_socket;
+    uint32_t m_start;
 };
 
 class MsgReader
@@ -344,18 +335,34 @@ private:
     MsgReader     m_reader;
     DisplayCoord  m_dimensions;
     OnKeyCallback m_on_key;
+    RemoteBuffer  m_send_buffer;
 
     SafePtr<Client> m_client;
 };
 
+static bool send_data(int fd, RemoteBuffer& buffer)
+{
+    while (buffer.size() > 0 and fd_writable(fd))
+    {
+      int res = ::write(fd, buffer.data(), buffer.size());
+      if (res <= 0)
+          throw remote_error{res ? "peer disconnected"
+                                 : format("socket write failed: {}", strerror(errno))};
+      buffer.erase(buffer.begin(), buffer.begin() + res);
+    }
+    return buffer.empty();
+}
 
 RemoteUI::RemoteUI(int socket, DisplayCoord dimensions)
-    : m_socket_watcher(socket,  FdEvents::Read,
+    : m_socket_watcher(socket,  FdEvents::Read | FdEvents::Write,
-                       [this](FDWatcher& watcher, FdEvents, EventMode mode) {
+                       [this](FDWatcher& watcher, FdEvents events, EventMode mode) {
           const int sock = watcher.fd();
           try
           {
-              while (fd_readable(sock))
+              if (events & FdEvents::Write and send_data(sock, m_send_buffer))
+                  m_socket_watcher.events() &= ~FdEvents::Write;
+
+              while (events & FdEvents::Read and fd_readable(sock))
               {
                   m_reader.read_available(sock);
 
@@ -377,7 +384,7 @@ RemoteUI::RemoteUI(int socket, DisplayCoord dimensions)
           }
           catch (const remote_error& err)
           {
-              write_to_debug_buffer(format("Error while reading remote message: {}", err.what()));
+              write_to_debug_buffer(format("Error while transfering remote messages: {}", err.what()));
               ClientManager::instance().remove_client(*m_client, false);
           }
       }),
@@ -396,72 +403,81 @@ void RemoteUI::menu_show(ConstArrayView<DisplayLine> choices,
                          DisplayCoord anchor, Face fg, Face bg,
                          MenuStyle style)
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::MenuShow};
+    MsgWriter msg{m_send_buffer, MessageType::MenuShow};
     msg.write(choices);
     msg.write(anchor);
     msg.write(fg);
     msg.write(bg);
     msg.write(style);
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 void RemoteUI::menu_select(int selected)
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::MenuSelect};
+    MsgWriter msg{m_send_buffer, MessageType::MenuSelect};
     msg.write(selected);
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 void RemoteUI::menu_hide()
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::MenuHide};
+    MsgWriter msg{m_send_buffer, MessageType::MenuHide};
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 void RemoteUI::info_show(StringView title, StringView content,
                          DisplayCoord anchor, Face face,
                          InfoStyle style)
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::InfoShow};
+    MsgWriter msg{m_send_buffer, MessageType::InfoShow};
     msg.write(title);
     msg.write(content);
     msg.write(anchor);
     msg.write(face);
     msg.write(style);
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 void RemoteUI::info_hide()
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::InfoHide};
+    MsgWriter msg{m_send_buffer, MessageType::InfoHide};
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 void RemoteUI::draw(const DisplayBuffer& display_buffer,
                     const Face& default_face,
                     const Face& padding_face)
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::Draw};
+    MsgWriter msg{m_send_buffer, MessageType::Draw};
     msg.write(display_buffer);
     msg.write(default_face);
     msg.write(padding_face);
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 void RemoteUI::draw_status(const DisplayLine& status_line,
                            const DisplayLine& mode_line,
                            const Face& default_face)
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::DrawStatus};
+    MsgWriter msg{m_send_buffer, MessageType::DrawStatus};
     msg.write(status_line);
     msg.write(mode_line);
     msg.write(default_face);
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 void RemoteUI::refresh(bool force)
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::Refresh};
+    MsgWriter msg{m_send_buffer, MessageType::Refresh};
     msg.write(force);
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 void RemoteUI::set_ui_options(const Options& options)
 {
-    MsgWriter msg{m_socket_watcher.fd(), MessageType::SetOptions};
+    MsgWriter msg{m_send_buffer, MessageType::SetOptions};
     msg.write(options);
+    m_socket_watcher.events() |= FdEvents::Write;
 }
 
 static sockaddr_un session_addr(StringView session)
@@ -500,26 +516,32 @@ RemoteClient::RemoteClient(StringView session, std::unique_ptr<UserInterface>&&
     int sock = connect_to(session);
 
     {
-        MsgWriter msg{sock, MessageType::Connect};
+        MsgWriter msg{m_send_buffer, MessageType::Connect};
         msg.write(init_command);
         msg.write(m_ui->dimensions());
         msg.write(env_vars);
     }
 
     m_ui->set_on_key([this](Key key){
-        MsgWriter msg(m_socket_watcher->fd(), MessageType::Key);
+        MsgWriter msg(m_send_buffer, MessageType::Key);
         msg.write(key);
+        m_socket_watcher->events() |= FdEvents::Write;
      });
 
     MsgReader reader;
-    m_socket_watcher.reset(new FDWatcher{sock, FdEvents::Read,
+    m_socket_watcher.reset(new FDWatcher{sock, FdEvents::Read | FdEvents::Write,
-                           [this, reader](FDWatcher& watcher, FdEvents, EventMode) mutable {
+                           [this, reader](FDWatcher& watcher, FdEvents events, EventMode) mutable {
         const int sock = watcher.fd();
-        while (fd_readable(sock) and not reader.ready())
+        if (events & FdEvents::Write and send_data(sock, m_send_buffer))
+            m_socket_watcher->events() &= ~FdEvents::Write;
+
+        while (events & FdEvents::Read and
+               not reader.ready() and fd_readable(sock))
+        {
             reader.read_available(sock);
 
             if (not reader.ready())
-            return;
+                continue;
 
             auto clear_reader = on_scope_end([&reader] { reader.reset(); });
             switch (reader.type())
@@ -578,6 +600,7 @@ RemoteClient::RemoteClient(StringView session, std::unique_ptr<UserInterface>&&
             default:
                 kak_assert(false);
             }
+        }
     }});
 }
 
@@ -585,8 +608,12 @@ void send_command(StringView session, StringView command)
 {
     int sock = connect_to(session);
     auto close_sock = on_scope_end([sock]{ close(sock); });
-    MsgWriter msg{sock, MessageType::Command};
+    RemoteBuffer buffer;
+    {
+        MsgWriter msg{buffer, MessageType::Command};
         msg.write(command);
+    }
+    write(sock, {buffer.data(), buffer.data() + buffer.size()});
 }
 
 
@@ -613,11 +640,8 @@ private:
         const int sock = m_socket_watcher.fd();
         try
         {
-            do
+            while (not m_reader.ready() and fd_readable(sock))
-            {
                 m_reader.read_available(sock);
-            }
-            while (fd_readable(sock) and not m_reader.ready());
 
             if (not m_reader.ready())
                 return;

src/remote.hh

@@ -4,6 +4,7 @@
 #include "env_vars.hh"
 #include "exception.hh"
 #include "utils.hh"
+#include "vector.hh"
 
 #include <memory>
 
@@ -12,14 +13,13 @@ namespace Kakoune
 
 struct remote_error : runtime_error
 {
-    remote_error(String error)
+    using runtime_error::runtime_error;
-        : runtime_error{std::move(error)}
-    {}
 };
 
 class FDWatcher;
 class UserInterface;
-struct Key;
+
+using RemoteBuffer = Vector<char, MemoryDomain::Remote>;
 
 // A remote client handle communication between a client running on the server
 // and a user interface running on the local process.
@@ -32,6 +32,7 @@ public:
 private:
     std::unique_ptr<UserInterface> m_ui;
     std::unique_ptr<FDWatcher>     m_socket_watcher;
+    RemoteBuffer                   m_send_buffer;
 };
 
 void send_command(StringView session, StringView command);