1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
|
// Copyright (c) 2006-2009 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 CHROME_COMMON_FILE_DESCRIPTOR_POSIX_H_
#define CHROME_COMMON_FILE_DESCRIPTOR_POSIX_H_
#include <vector>
// -----------------------------------------------------------------------------
// A FileDescriptor is a structure for use in IPC messages. It allows one to
// send descriptors over an IPC channel.
//
// In the Windows world, processes can peek and poke the HANDLE table of other
// processes. On POSIX, in order to transmit descriptors we need to include
// them in a control-message (a side-channel on the UNIX domain socket).
// Serialising this type adds descriptors to a vector in the IPC Message, from
// which the IPC channel can package them up for the kernel.
// -----------------------------------------------------------------------------
struct FileDescriptor {
FileDescriptor()
: fd(-1),
auto_close(false) { }
int fd;
// If true, close this descriptor after it has been sent.
bool auto_close;
};
// -----------------------------------------------------------------------------
// A DescriptorSet is an ordered set of POSIX file descriptors. These are
// associated with IPC messages so that descriptors can be transmitted over a
// UNIX domain socket.
// -----------------------------------------------------------------------------
class DescriptorSet {
public:
DescriptorSet();
~DescriptorSet();
// This is the maximum number of descriptors per message. We need to know this
// because the control message kernel interface has to be given a buffer which
// is large enough to store all the descriptor numbers. Otherwise the kernel
// tells us that it truncated the control data and the extra descriptors are
// lost.
//
// In debugging mode, it's a fatal error to try and add more than this number
// of descriptors to a DescriptorSet.
enum {
MAX_DESCRIPTORS_PER_MESSAGE = 4,
};
// ---------------------------------------------------------------------------
// Interfaces for building during message serialisation...
// Add a descriptor to the end of the set
void Add(int fd);
// Add a descriptor to the end of the set and automatically close it after
// transmission.
void AddAndAutoClose(int fd);
// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------
// Interfaces for accessing during message deserialisation...
// Return the number of descriptors remaining
unsigned size() const { return descriptors_.size() - next_descriptor_; }
// Return true if no unconsumed descriptors remain
bool empty() const { return descriptors_.size() == next_descriptor_; }
// Fetch the next descriptor from the beginning of the set. This interface is
// designed for the deserialising code as it doesn't support close flags.
// returns: file descriptor, or -1 on error
int NextDescriptor();
// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------
// Interfaces for transmission...
// Fill an array with file descriptors without 'consuming' them. CommitAll
// must be called after these descriptors have been transmitted.
// buffer: (output) a buffer of, at least, size() integers.
void GetDescriptors(int* buffer) const;
// This must be called after transmitting the descriptors returned by
// GetDescriptors. It marks all the descriptors as consumed and closes those
// which are auto-close.
void CommitAll();
// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------
// Interfaces for receiving...
// Set the contents of the set from the given buffer. This set must be empty
// before calling. The auto-close flag is set on all the descriptors so that
// unconsumed descriptors are closed on destruction.
void SetDescriptors(const int* buffer, unsigned count);
// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------
// Interfaces for IPC::Message...
// Take all the FileDescriptors from another set. Just like a copy
// constructor, except that the source is emptied.
void TakeFrom(DescriptorSet* other);
// ---------------------------------------------------------------------------
private:
// A vector of descriptors and close flags. If this message is sent, then
// these descriptors are sent as control data. After sending, any descriptors
// with a true flag are closed. If this message has been received, then these
// are the descriptors which were received and all close flags are true.
std::vector<FileDescriptor> descriptors_;
// When deserialising the message, the descriptors will be extracted
// one-by-one. This contains the index of the next unused descriptor.
unsigned next_descriptor_;
};
#endif // CHROME_COMMON_FILE_DESCRIPTOR_POSIX_H_
|
