Broker out PPAPI handle duplication

content/public/common/sandbox_init.cc

+// Copyright (c) 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.
+
+#include "content/public/common/sandbox_init.h"
+
+namespace content {
+
+IPC::PlatformFileForTransit BrokerGetFileHandleForProcess(

[jschuh, 2012/05/10 00:10:57]

Cross platform function to make an exact copy of the handle.

+    base::PlatformFile handle,
+    base::ProcessId target_process_id,
+    bool should_close_source) {
+  IPC::PlatformFileForTransit out_handle;
+#if defined(OS_WIN)
+  DWORD options = DUPLICATE_SAME_ACCESS;
+  if (should_close_source)
+    options |= DUPLICATE_CLOSE_SOURCE;
+  if (!content::BrokerDuplicateHandle(handle, target_process_id, &out_handle,
+                                      0, options)) {
+    out_handle = IPC::InvalidPlatformFileForTransit();
+  }
+#elif defined(OS_POSIX)
+  // If asked to close the source, we can simply re-use the source fd instead of
+  // dup()ing and close()ing.
+  // When we're not closing the source, we need to duplicate the handle and take
+  // ownership of that. The reason is that this function is often used to
+  // generate IPC messages, and the handle must remain valid until it's sent to
+  // the other process from the I/O thread. Without the dup, calling code might
+  // close the source handle before the message is sent, creating a race
+  // condition.
+  int fd = should_close_source ? handle : ::dup(handle);
+  out_handle = base::FileDescriptor(fd, true);
+#else
+  #error Not implemented.
+#endif
+  return out_handle;
+}
+
+}  // namespace content
+