Move FileDescriptorShuffle to base/posix. This file is very posix-specific.

base/file_descriptor_shuffle.h

-// Copyright (c) 2011 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_FILE_DESCRIPTOR_SHUFFLE_H_
-#define BASE_FILE_DESCRIPTOR_SHUFFLE_H_
-
-// This code exists to perform the shuffling of file descriptors which is
-// commonly needed when forking subprocesses. The naive approve is very simple,
-// just call dup2 to setup the desired descriptors, but wrong. It's tough to
-// handle the edge cases (like mapping 0 -> 1, 1 -> 0) correctly.
-//
-// In order to unittest this code, it's broken into the abstract action (an
-// injective multimap) and the concrete code for dealing with file descriptors.
-// Users should use the code like this:
-//   base::InjectiveMultimap file_descriptor_map;
-//   file_descriptor_map.push_back(base::InjectionArc(devnull, 0, true));
-//   file_descriptor_map.push_back(base::InjectionArc(devnull, 2, true));
-//   file_descriptor_map.push_back(base::InjectionArc(pipe[1], 1, true));
-//   base::ShuffleFileDescriptors(file_descriptor_map);
-//
-// and trust the the Right Thing will get done.
-
-#include <vector>
-
-#include "base/base_export.h"
-#include "base/compiler_specific.h"
-
-namespace base {
-
-// A Delegate which performs the actions required to perform an injective
-// multimapping in place.
-class InjectionDelegate {
- public:
-  // Duplicate |fd|, an element of the domain, and write a fresh element of the
-  // domain into |result|. Returns true iff successful.
-  virtual bool Duplicate(int* result, int fd) = 0;
-  // Destructively move |src| to |dest|, overwriting |dest|. Returns true iff
-  // successful.
-  virtual bool Move(int src, int dest) = 0;
-  // Delete an element of the domain.
-  virtual void Close(int fd) = 0;
-
- protected:
-  virtual ~InjectionDelegate() {}
-};
-
-// An implementation of the InjectionDelegate interface using the file
-// descriptor table of the current process as the domain.
-class FileDescriptorTableInjection : public InjectionDelegate {
-  virtual bool Duplicate(int* result, int fd) OVERRIDE;
-  virtual bool Move(int src, int dest) OVERRIDE;
-  virtual void Close(int fd) OVERRIDE;
-};
-
-// A single arc of the directed graph which describes an injective multimapping.
-struct InjectionArc {
-  InjectionArc(int in_source, int in_dest, bool in_close)
-      : source(in_source),
-        dest(in_dest),
-        close(in_close) {
-  }
-
-  int source;
-  int dest;
-  bool close;  // if true, delete the source element after performing the
-               // mapping.
-};
-
-typedef std::vector<InjectionArc> InjectiveMultimap;
-
-BASE_EXPORT bool PerformInjectiveMultimap(const InjectiveMultimap& map,
-                                          InjectionDelegate* delegate);
-
-BASE_EXPORT bool PerformInjectiveMultimapDestructive(
-    InjectiveMultimap* map,
-    InjectionDelegate* delegate);
-
-// This function will not call malloc but will mutate |map|
-static inline bool ShuffleFileDescriptors(InjectiveMultimap* map) {
-  FileDescriptorTableInjection delegate;
-  return PerformInjectiveMultimapDestructive(map, &delegate);
-}
-
-}  // namespace base
-
-#endif  // BASE_FILE_DESCRIPTOR_SHUFFLE_H_