ipc/chromium/src/base/file_descriptor_shuffle.h@6474c204b198
ipc/chromium/src/base/file_descriptor_shuffle.h
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #ifndef BASE_FILE_DESCRIPTOR_SHUFFLE_H_
6 #define BASE_FILE_DESCRIPTOR_SHUFFLE_H_
8 // This code exists to perform the shuffling of file descriptors which is
9 // commonly needed when forking subprocesses. The naive approve is very simple,
10 // just call dup2 to setup the desired descriptors, but wrong. It's tough to
11 // handle the edge cases (like mapping 0 -> 1, 1 -> 0) correctly.
12 //
13 // In order to unittest this code, it's broken into the abstract action (an
14 // injective multimap) and the concrete code for dealing with file descriptors.
15 // Users should use the code like this:
16 // base::InjectiveMultimap file_descriptor_map;
17 // file_descriptor_map.push_back(base::InjectionArc(devnull, 0, true));
18 // file_descriptor_map.push_back(base::InjectionArc(devnull, 2, true));
19 // file_descriptor_map.push_back(base::InjectionArc(pipe[1], 1, true));
20 // base::ShuffleFileDescriptors(file_descriptor_map);
21 //
22 // and trust the the Right Thing will get done.
24 #include <vector>
26 namespace base {
28 // A Delegate which performs the actions required to perform an injective
29 // multimapping in place.
30 class InjectionDelegate {
31 public:
32 // Duplicate |fd|, an element of the domain, and write a fresh element of the
33 // domain into |result|. Returns true iff successful.
34 virtual bool Duplicate(int* result, int fd) = 0;
35 // Destructively move |src| to |dest|, overwriting |dest|. Returns true iff
36 // successful.
37 virtual bool Move(int src, int dest) = 0;
38 // Delete an element of the domain.
39 virtual void Close(int fd) = 0;
40 };
42 // An implementation of the InjectionDelegate interface using the file
43 // descriptor table of the current process as the domain.
44 class FileDescriptorTableInjection : public InjectionDelegate {
45 bool Duplicate(int* result, int fd);
46 bool Move(int src, int dest);
47 void Close(int fd);
48 };
50 // A single arc of the directed graph which describes an injective multimapping.
51 struct InjectionArc {
52 InjectionArc(int in_source, int in_dest, bool in_close)
53 : source(in_source),
54 dest(in_dest),
55 close(in_close) {
56 }
58 int source;
59 int dest;
60 bool close; // if true, delete the source element after performing the
61 // mapping.
62 };
64 typedef std::vector<InjectionArc> InjectiveMultimap;
66 bool PerformInjectiveMultimap(const InjectiveMultimap& map,
67 InjectionDelegate* delegate);
68 bool PerformInjectiveMultimapDestructive(InjectiveMultimap* map,
69 InjectionDelegate* delegate);
71 // This function will not call malloc but will mutate |map|
72 static inline bool ShuffleFileDescriptors(InjectiveMultimap *map) {
73 FileDescriptorTableInjection delegate;
74 return PerformInjectiveMultimapDestructive(map, &delegate);
75 }
77 } // namespace base
79 #endif // !BASE_FILE_DESCRIPTOR_SHUFFLE_H_
