Provide an iOS message pump for IO implementation.

base/mac/scoped_cffiledescriptorref.h

+// Copyright 2012 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.
+
+#ifndef BASE_MAC_SCOPED_CFFILEDESCRIPTORREF_H_
+#define BASE_MAC_SCOPED_CFFILEDESCRIPTORREF_H_
+
+#include <CoreFoundation/CoreFoundation.h>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+
+namespace base {
+namespace mac {
+
+// ScopedCFFileDescriptorRef is designed after ScopedCFTypeRef<>. On
+// destruction, it will invalidate the file descriptor.

[droger, 2012/11/20 14:41:28]

It seems that ScopedCFTypeRef has evolved since this has been written.
We may want to change that comment or (even better) make it true by merging the
changes.

[blundell, 2012/11/20 20:38:54]

After discussion, droger and I realized that ScopedCFTypeRef has actually
evolved *away* from ScopedCFFileDescriptorRef. ScopedCFTypeRef has evolved to
support RETAIN semantics and copying, but it only makes sense for a file
descriptor to have one owner, as the file descriptor will be invalidated on the
destruction/reset of the first owner.

+class ScopedCFFileDescriptorRef {

[Mark Mentovai, 2012/11/20 14:47:58]

Can this just extend ScopedCFTypeRef<CFFileDescriptorRef> and thus be simpler?

[blundell, 2012/11/20 20:38:54]

See the above comment; I could have this extend
ScopedCFTypeRef<CFFileDescriptorRef>, but then would have to go to pains to
ensure that RETAIN semantics, copying, etc. is never invoked. I don't think the
end result would look simpler and this approach seems safer to me (less chance
of the object mistakenly being used in a way it's not intended to be). What do
you think?

On 2012/11/20 14:47:58, Mark Mentovai wrote:

+ public:
+  explicit ScopedCFFileDescriptorRef(CFFileDescriptorRef fdref = NULL)
+      : fdref_(fdref) {
+  }
+
+  ~ScopedCFFileDescriptorRef() {
+    if (fdref_) {
+      CFFileDescriptorInvalidate(fdref_);
+      CFRelease(fdref_);
+    }
+  }
+
+  void reset(CFFileDescriptorRef fdref = NULL) {
+    if (fdref_) {

[droger, 2012/11/20 14:41:28]

Do we want to handle the case where fdref == fdref_?
ScopedCFTypeRef does it.

Or maybe simply DCHECK_NE(fdref, fdref_).

[blundell, 2012/11/20 20:38:54]

Done.

+      CFFileDescriptorInvalidate(fdref_);
+      CFRelease(fdref_);
+    }
+    fdref_ = fdref;
+  }
+
+  bool operator==(CFFileDescriptorRef that) const {
+    return fdref_ == that;
+  }
+
+  bool operator!=(CFFileDescriptorRef that) const {
+    return fdref_ != that;
+  }
+
+  operator CFFileDescriptorRef() const {
+    return fdref_;
+  }
+
+  CFFileDescriptorRef get() const {
+    return fdref_;
+  }
+
+  CFFileDescriptorRef release() WARN_UNUSED_RESULT {
+    CFFileDescriptorRef temp = fdref_;
+    fdref_ = NULL;
+    return temp;
+  }
+
+ private:
+  CFFileDescriptorRef fdref_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedCFFileDescriptorRef);
+};
+
+}  // namespace mac
+}  // namespace base
+
+#endif  // BASE_MAC_SCOPED_CFFILEDESCRIPTORREF_H_