ipc/file_descriptor_set_posix.h

   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 #pragma once
   8
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/file_descriptor_posix.h"
  13 #include "base/memory/ref_counted.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 FileDescriptorSet : public base::RefCountedThreadSafe<FileDescriptorSet> {
  21  public:
  22   FileDescriptorSet();
  23
  24   // This is the maximum number of descriptors per message. We need to know this
  25   // because the control message kernel interface has to be given a buffer which
  26   // is large enough to store all the descriptor numbers. Otherwise the kernel
  27   // tells us that it truncated the control data and the extra descriptors are
  28   // lost.
  29   //
  30   // In debugging mode, it's a fatal error to try and add more than this number
  31   // of descriptors to a FileDescriptorSet.
  32   enum {
  33     MAX_DESCRIPTORS_PER_MESSAGE = 5,
  34   };
  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 Add(int 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 AddAndAutoClose(int 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 descriptors_.empty(); }
  55   // Fetch the nth descriptor from the beginning of the set. Code using this
  56   // /must/ access the descriptors in order, except that it may wrap from the
  57   // end to index 0 again.
  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   int GetDescriptorAt(unsigned n) const;
  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 GetDescriptors(int* buffer) const;
  74   // This must be called after transmitting the descriptors returned by
  75   // GetDescriptors. 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
  82   // ---------------------------------------------------------------------------
  83
  84
  85   // ---------------------------------------------------------------------------
  86   // Interfaces for receiving...
  87
  88   // Set the contents of the set from the given buffer. This set must be empty
  89   // before calling. The auto-close flag is set on all the descriptors so that
  90   // unconsumed descriptors are closed on destruction.
  91   void SetDescriptors(const int* buffer, unsigned count);
  92
  93   // ---------------------------------------------------------------------------
  94
  95  private:
  96   friend class base::RefCountedThreadSafe<FileDescriptorSet>;
  97
  98   ~FileDescriptorSet();
  99
 100   // A vector of descriptors and close flags. If this message is sent, then
 101   // these descriptors are sent as control data. After sending, any descriptors
 102   // with a true flag are closed. If this message has been received, then these
 103   // are the descriptors which were received and all close flags are true.
 104   std::vector<base::FileDescriptor> descriptors_;
 105
 106   // This contains the index of the next descriptor which should be consumed.
 107   // It's used in a couple of ways. Firstly, at destruction we can check that
 108   // all the descriptors have been read (with GetNthDescriptor). Secondly, we
 109   // can check that they are read in order.
 110   mutable unsigned consumed_descriptor_highwater_;
 111
 112   DISALLOW_COPY_AND_ASSIGN(FileDescriptorSet);
 113 };
 114
 115 #endif  // IPC_FILE_DESCRIPTOR_SET_POSIX_H_