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