1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/ipc/chromium/src/base/file_descriptor_shuffle.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,79 @@
1.4 +// Copyright (c) 2009 The Chromium Authors. All rights reserved.
1.5 +// Use of this source code is governed by a BSD-style license that can be
1.6 +// found in the LICENSE file.
1.7 +
1.8 +#ifndef BASE_FILE_DESCRIPTOR_SHUFFLE_H_
1.9 +#define BASE_FILE_DESCRIPTOR_SHUFFLE_H_
1.10 +
1.11 +// This code exists to perform the shuffling of file descriptors which is
1.12 +// commonly needed when forking subprocesses. The naive approve is very simple,
1.13 +// just call dup2 to setup the desired descriptors, but wrong. It's tough to
1.14 +// handle the edge cases (like mapping 0 -> 1, 1 -> 0) correctly.
1.15 +//
1.16 +// In order to unittest this code, it's broken into the abstract action (an
1.17 +// injective multimap) and the concrete code for dealing with file descriptors.
1.18 +// Users should use the code like this:
1.19 +// base::InjectiveMultimap file_descriptor_map;
1.20 +// file_descriptor_map.push_back(base::InjectionArc(devnull, 0, true));
1.21 +// file_descriptor_map.push_back(base::InjectionArc(devnull, 2, true));
1.22 +// file_descriptor_map.push_back(base::InjectionArc(pipe[1], 1, true));
1.23 +// base::ShuffleFileDescriptors(file_descriptor_map);
1.24 +//
1.25 +// and trust the the Right Thing will get done.
1.26 +
1.27 +#include <vector>
1.28 +
1.29 +namespace base {
1.30 +
1.31 +// A Delegate which performs the actions required to perform an injective
1.32 +// multimapping in place.
1.33 +class InjectionDelegate {
1.34 + public:
1.35 + // Duplicate |fd|, an element of the domain, and write a fresh element of the
1.36 + // domain into |result|. Returns true iff successful.
1.37 + virtual bool Duplicate(int* result, int fd) = 0;
1.38 + // Destructively move |src| to |dest|, overwriting |dest|. Returns true iff
1.39 + // successful.
1.40 + virtual bool Move(int src, int dest) = 0;
1.41 + // Delete an element of the domain.
1.42 + virtual void Close(int fd) = 0;
1.43 +};
1.44 +
1.45 +// An implementation of the InjectionDelegate interface using the file
1.46 +// descriptor table of the current process as the domain.
1.47 +class FileDescriptorTableInjection : public InjectionDelegate {
1.48 + bool Duplicate(int* result, int fd);
1.49 + bool Move(int src, int dest);
1.50 + void Close(int fd);
1.51 +};
1.52 +
1.53 +// A single arc of the directed graph which describes an injective multimapping.
1.54 +struct InjectionArc {
1.55 + InjectionArc(int in_source, int in_dest, bool in_close)
1.56 + : source(in_source),
1.57 + dest(in_dest),
1.58 + close(in_close) {
1.59 + }
1.60 +
1.61 + int source;
1.62 + int dest;
1.63 + bool close; // if true, delete the source element after performing the
1.64 + // mapping.
1.65 +};
1.66 +
1.67 +typedef std::vector<InjectionArc> InjectiveMultimap;
1.68 +
1.69 +bool PerformInjectiveMultimap(const InjectiveMultimap& map,
1.70 + InjectionDelegate* delegate);
1.71 +bool PerformInjectiveMultimapDestructive(InjectiveMultimap* map,
1.72 + InjectionDelegate* delegate);
1.73 +
1.74 +// This function will not call malloc but will mutate |map|
1.75 +static inline bool ShuffleFileDescriptors(InjectiveMultimap *map) {
1.76 + FileDescriptorTableInjection delegate;
1.77 + return PerformInjectiveMultimapDestructive(map, &delegate);
1.78 +}
1.79 +
1.80 +} // namespace base
1.81 +
1.82 +#endif // !BASE_FILE_DESCRIPTOR_SHUFFLE_H_
