1// Copyright (c) 2011 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.
4
5#ifndef IPC_FILE_DESCRIPTOR_SET_POSIX_H_
6#define IPC_FILE_DESCRIPTOR_SET_POSIX_H_
7
8#include <vector>
9
10#include "base/basictypes.h"
11#include "base/files/file.h"
12#include "base/memory/ref_counted.h"
13#include "base/memory/scoped_vector.h"
14#include "ipc/ipc_export.h"
15
16// -----------------------------------------------------------------------------
17// A FileDescriptorSet is an ordered set of POSIX file descriptors. These are
18// associated with IPC messages so that descriptors can be transmitted over a
19// UNIX domain socket.
20// -----------------------------------------------------------------------------
21class IPC_EXPORT FileDescriptorSet
22    : public base::RefCountedThreadSafe<FileDescriptorSet> {
23 public:
24  FileDescriptorSet();
25
26  // This is the maximum number of descriptors per message. We need to know this
27  // because the control message kernel interface has to be given a buffer which
28  // is large enough to store all the descriptor numbers. Otherwise the kernel
29  // tells us that it truncated the control data and the extra descriptors are
30  // lost.
31  //
32  // In debugging mode, it's a fatal error to try and add more than this number
33  // of descriptors to a FileDescriptorSet.
34  static const size_t kMaxDescriptorsPerMessage = 7;
35
36  // ---------------------------------------------------------------------------
37  // Interfaces for building during message serialisation...
38
39  // Add a descriptor to the end of the set. Returns false iff the set is full.
40  bool AddToBorrow(base::PlatformFile fd);
41  // Add a descriptor to the end of the set and automatically close it after
42  // transmission. Returns false iff the set is full.
43  bool AddToOwn(base::ScopedFD fd);
44
45  // ---------------------------------------------------------------------------
46
47
48  // ---------------------------------------------------------------------------
49  // Interfaces for accessing during message deserialisation...
50
51  // Return the number of descriptors
52  unsigned size() const { return descriptors_.size(); }
53  // Return true if no unconsumed descriptors remain
54  bool empty() const { return 0 == size(); }
55  // Take the nth descriptor from the beginning of the set,
56  // transferring the ownership of the descriptor taken. Code using this
57  // /must/ access the descriptors in order, and must do it at most once.
58  //
59  // This interface is designed for the deserialising code as it doesn't
60  // support close flags.
61  //   returns: file descriptor, or -1 on error
62  base::PlatformFile TakeDescriptorAt(unsigned n);
63
64  // ---------------------------------------------------------------------------
65
66
67  // ---------------------------------------------------------------------------
68  // Interfaces for transmission...
69
70  // Fill an array with file descriptors without 'consuming' them. CommitAll
71  // must be called after these descriptors have been transmitted.
72  //   buffer: (output) a buffer of, at least, size() integers.
73  void PeekDescriptors(base::PlatformFile* buffer) const;
74  // This must be called after transmitting the descriptors returned by
75  // PeekDescriptors. It marks all the descriptors as consumed and closes those
76  // which are auto-close.
77  void CommitAll();
78  // Returns true if any contained file descriptors appear to be handles to a
79  // directory.
80  bool ContainsDirectoryDescriptor() const;
81  // Fetch all filedescriptors with the "auto close" property.
82  // Used instead of CommitAll() when closing must be handled manually.
83  void ReleaseFDsToClose(std::vector<base::PlatformFile>* fds);
84
85  // ---------------------------------------------------------------------------
86
87
88  // ---------------------------------------------------------------------------
89  // Interfaces for receiving...
90
91  // Set the contents of the set from the given buffer. This set must be empty
92  // before calling. The auto-close flag is set on all the descriptors so that
93  // unconsumed descriptors are closed on destruction.
94  void AddDescriptorsToOwn(const base::PlatformFile* buffer, unsigned count);
95
96  // ---------------------------------------------------------------------------
97
98 private:
99  friend class base::RefCountedThreadSafe<FileDescriptorSet>;
100
101  ~FileDescriptorSet();
102
103  // A vector of descriptors and close flags. If this message is sent, then
104  // these descriptors are sent as control data. After sending, any descriptors
105  // with a true flag are closed. If this message has been received, then these
106  // are the descriptors which were received and all close flags are true.
107  std::vector<base::PlatformFile> descriptors_;
108  ScopedVector<base::ScopedFD> owned_descriptors_;
109
110  // This contains the index of the next descriptor which should be consumed.
111  // It's used in a couple of ways. Firstly, at destruction we can check that
112  // all the descriptors have been read (with GetNthDescriptor). Secondly, we
113  // can check that they are read in order.
114  mutable unsigned consumed_descriptor_highwater_;
115
116  DISALLOW_COPY_AND_ASSIGN(FileDescriptorSet);
117};
118
119#endif  // IPC_FILE_DESCRIPTOR_SET_POSIX_H_
120