Use libevent, second try. Changes this time:...

net/base/tcp_client_socket.h

Index: net/base/tcp_client_socket.h
===================================================================
--- net/base/tcp_client_socket.h	(revision 2361)
+++ net/base/tcp_client_socket.h	(working copy)
@@ -5,11 +5,21 @@
 #ifndef NET_BASE_TCP_CLIENT_SOCKET_H_
 #define NET_BASE_TCP_CLIENT_SOCKET_H_
 
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
 #include <ws2tcpip.h>
+#include "base/object_watcher.h"
+#elif defined(OS_POSIX)
+struct event;  // From libevent
+#define SOCKET int
+#include "base/message_pump_libevent.h"
+#endif
 
-#include "base/object_watcher.h"
+#include "base/scoped_ptr.h"
 #include "net/base/address_list.h"
 #include "net/base/client_socket.h"
+#include "net/base/completion_callback.h"
 
 namespace net {
 
@@ -18,7 +28,12 @@
 // NOTE: The implementation supports half duplex only.  Read and Write calls
 // must not be in progress at the same time.
 class TCPClientSocket : public ClientSocket,
-                        public base::ObjectWatcher::Delegate {
+#if defined(OS_WIN)
+                        public base::ObjectWatcher::Delegate 
+#elif defined(OS_POSIX)
+                        public base::MessagePumpLibevent::Watcher
+#endif
+{
  public:
   // The IP address(es) and port number to connect to.  The TCP socket will try
   // each IP address in the list until it succeeds in establishing a
@@ -34,31 +49,23 @@
   virtual bool IsConnected() const;
 
   // Socket methods:
+  // Try to transfer buf_len bytes to/from socket.
+  // If a result is available now, return it; else call back later with one.
+  // Do not call again until a result is returned!
+  // If any bytes were transferred, the result is the byte count.
+  // On error, result is a negative error code; see net/base/net_error_list.h 
+  // TODO: what would a zero return value indicate?
+  // TODO: support multiple outstanding requests?
   virtual int Read(char* buf, int buf_len, CompletionCallback* callback);
   virtual int Write(const char* buf, int buf_len, CompletionCallback* callback);
 
  private:
-  int CreateSocket(const struct addrinfo* ai);
-  void DoCallback(int rv);
-  void DidCompleteConnect();
-  void DidCompleteIO();
-
-  // base::ObjectWatcher::Delegate methods:
-  virtual void OnObjectSignaled(HANDLE object);
-
   SOCKET socket_;
-  OVERLAPPED overlapped_;
-  WSABUF buffer_;
 
-  base::ObjectWatcher watcher_;
-
-  CompletionCallback* callback_;
-
   // The list of addresses we should try in order to establish a connection.
   AddressList addresses_;
 
-  // The addrinfo that we are attempting to use or NULL if all addrinfos have
-  // been tried.
+  // Where we are in above list, or NULL if all addrinfos have been tried.
   const struct addrinfo* current_ai_;
 
   enum WaitState {
@@ -68,6 +75,34 @@
     WAITING_WRITE
   };
   WaitState wait_state_;
+
+#if defined(OS_WIN)
+  // base::ObjectWatcher::Delegate methods:
+  virtual void OnObjectSignaled(HANDLE object);
+
+  OVERLAPPED overlapped_;
+  WSABUF buffer_;
+
+  base::ObjectWatcher watcher_;
+#elif defined(OS_POSIX)
+  // The socket's libevent wrapper
+  scoped_ptr<event> event_;
+
+  // Called by MessagePumpLibevent when the socket is ready to do I/O
+  void OnSocketReady(short flags);
+
+  // The buffer used by OnSocketReady to retry Read and Write requests
+  char* buf_;
+  int buf_len_;
+#endif
+
+  // External callback; called when read or write is complete.
+  CompletionCallback* callback_;
+
+  int CreateSocket(const struct addrinfo* ai);
+  void DoCallback(int rv);
+  void DidCompleteConnect();
+  void DidCompleteIO();
 };
 
 }  // namespace net