[NaCl SDK] nacl_io: Add flow control the JavaScript pipes.

native_client_sdk/src/libraries/nacl_io/pipe/pipe_node.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "nacl_io/pipe/pipe_node.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <pthread.h>
 #include <string.h>
 
 #include "nacl_io/ioctl.h"
 #include "nacl_io/kernel_handle.h"
 #include "nacl_io/pipe/pipe_event_emitter.h"
 
 namespace {
 const size_t kDefaultPipeSize = 512 * 1024;
 }
 
 namespace nacl_io {
 
 PipeNode::PipeNode(Filesystem* fs)
-    : StreamNode(fs), pipe_(new PipeEventEmitter(kDefaultPipeSize)) {}
+    : StreamNode(fs), pipe_(new PipeEventEmitter(kDefaultPipeSize)) {
+}
 
-EventEmitter* PipeNode::GetEventEmitter() { return pipe_.get(); }
+PipeEventEmitter* PipeNode::GetEventEmitter() {
+  return pipe_.get();
+}
 
 Error PipeNode::Read(const HandleAttr& attr,
                      void* buf,
                      size_t count,
                      int* out_bytes) {
   int ms = attr.IsBlocking() ? read_timeout_ : 0;
 
   EventListenerLock wait(GetEventEmitter());
   Error err = wait.WaitOnEvent(POLLIN, ms);
+  if (err == ETIMEDOUT)
+    err = EWOULDBLOCK;
   if (err)
     return err;
 
-  *out_bytes = pipe_->Read_Locked(static_cast<char*>(buf), count);
-  return 0;
+  return GetEventEmitter()->Read_Locked(static_cast<char*>(buf), count,
+                                        out_bytes);
 }
 
 Error PipeNode::Write(const HandleAttr& attr,
                       const void* buf,
                       size_t count,
                       int* out_bytes) {
   int ms = attr.IsBlocking() ? write_timeout_ : 0;
 
   EventListenerLock wait(GetEventEmitter());
   Error err = wait.WaitOnEvent(POLLOUT, ms);
+  if (err == ETIMEDOUT)
+    err = EWOULDBLOCK;
   if (err)
     return err;
 
-  *out_bytes = pipe_->Write_Locked(static_cast<const char*>(buf), count);
-  return 0;
+  return GetEventEmitter()->Write_Locked(static_cast<const char*>(buf),
+                                         count, out_bytes);
 }
 
 }  // namespace nacl_io