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