[NaCl SDK] nacl_io: Add support for basic socketpairs.

native_client_sdk/src/libraries/nacl_io/socket/unix_event_emitter.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.

[binji, 2015/09/17 01:03:57]

Fix year
remove (c)

[avallee, 2015/09/17 19:00:31]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "nacl_io/socket/unix_event_emitter.h"
+
+#include <stdlib.h>
+
+#include "nacl_io/fifo_char.h"
+#include "sdk_util/scoped_ref.h"
+
+namespace nacl_io {
+
+class UnixChildEventEmitter;
+class UnixMasterEventEmitter;
+
+typedef sdk_util::ScopedRef<UnixMasterEventEmitter>
+    ScopedUnixMasterEventEmitter;
+
+class UnixMasterEventEmitter : public UnixEventEmitter {
+ public:
+  UnixMasterEventEmitter(size_t size)

[binji, 2015/09/17 01:03:57]

explicit

[avallee, 2015/09/17 19:00:31]

Done.

+      : in_fifo_(size),
+        out_fifo_(size),
+        child_emitter_created_(false),
+        child_emitter_(NULL) {
+    UpdateStatus_Locked();
+  }
+
+  virtual ScopedUnixEventEmitter GetPeerEmitter();
+
+ protected:
+  virtual FIFOChar* in_fifoc() { return &in_fifo_; }
+  virtual FIFOChar* out_fifoc() { return &out_fifo_; }
+  virtual const sdk_util::SimpleLock& GetFifoLock() { return fifo_lock_; }
+
+ private:
+  FIFOChar in_fifo_;
+  FIFOChar out_fifo_;
+  sdk_util::SimpleLock fifo_lock_;
+  bool child_emitter_created_;
+  UnixChildEventEmitter* child_emitter_;
+
+  friend class UnixChildEventEmitter;
+};
+
+class UnixChildEventEmitter : public UnixEventEmitter {
+ public:
+  UnixChildEventEmitter(UnixMasterEventEmitter* parent)

[binji, 2015/09/17 01:03:58]

explicit

[avallee, 2015/09/17 19:00:31]

Done.

+      : parent_emitter_(parent) {
+    UpdateStatus_Locked();
+  }
+  virtual ScopedUnixEventEmitter GetPeerEmitter() { return parent_emitter_; }
+
+ protected:
+  virtual void Destroy() { parent_emitter_->child_emitter_ = NULL; }
+
+  virtual FIFOChar* in_fifoc() { return parent_emitter_->out_fifoc(); }
+  virtual FIFOChar* out_fifoc() { return parent_emitter_->in_fifoc(); }
+  virtual const sdk_util::SimpleLock& GetFifoLock() {
+    return parent_emitter_->GetFifoLock();
+  }
+
+ private:
+  ScopedUnixMasterEventEmitter parent_emitter_;
+};
+
+ScopedUnixEventEmitter UnixMasterEventEmitter::GetPeerEmitter() {
+  if (!child_emitter_created_) {
+    child_emitter_created_ = true;
+    child_emitter_ = new UnixChildEventEmitter(this);
+  }
+  return sdk_util::ScopedRef<UnixChildEventEmitter>(child_emitter_);
+}
+
+uint32_t UnixEventEmitter::ReadIn_Locked(char* data, uint32_t len) {
+  AUTO_LOCK(GetFifoLock());
+  uint32_t count = in_fifoc()->Read(data, len);
+  UpdateStatus_Locked();
+  ScopedUnixEventEmitter peer = GetPeerEmitter();
+  if (peer) {

[binji, 2015/09/17 01:03:57]

when would this be NULL?

[avallee, 2015/09/17 16:18:01]

It could be NULL if we never create a child emitter (if we reused the node code
and did not create a socketpair). This can also happen once the child node
reference count drops to 0, in which case it will set the child pointer to NULL
in its parent (line 56).

+    peer->UpdateStatus_Locked();
+  }
+  return count;
+}
+
+uint32_t UnixEventEmitter::WriteOut_Locked(const char* data, uint32_t len) {
+  AUTO_LOCK(GetFifoLock());
+  uint32_t count = out_fifoc()->Write(data, len);
+  ScopedUnixEventEmitter peer = GetPeerEmitter();
+  if (peer) {

[binji, 2015/09/17 01:03:58]

It looks like the order of updating status of this vs. peer matters here. Could
you elaborate why?

[avallee, 2015/09/17 16:18:00]

I don't *think* the order matters. However my initial intuition is that both
nodes would initially block on read and we may want to unblock them as early as
possible.

I would think Read should also update the peer first, to allow a write to
continue writing before returning to caller.

+    peer->UpdateStatus_Locked();
+  }
+  UpdateStatus_Locked();
+  return count;
+}
+
+ScopedUnixEventEmitter UnixEventEmitter::MakeUnixEventEmitter(size_t size) {
+  return ScopedUnixEventEmitter(new UnixMasterEventEmitter(size));
+}
+
+}  // namespace nacl_io