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 // ----------------------------------------------------------------------------- 21 class 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 size()52 unsigned size() const { return descriptors_.size(); } 53 // Return true if no unconsumed descriptors remain empty()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