ipc/ipc_message_attachment_set.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_IPC_MESSAGE_ATTACHMENT_SET_H_
   6 #define IPC_IPC_MESSAGE_ATTACHMENT_SET_H_
   7
   8 #include <vector>
   9
  10 #include "base/basictypes.h"
  11 #include "base/memory/ref_counted.h"
  12 #include "ipc/ipc_export.h"
  13
  14 #if defined(OS_POSIX)
  15 #include "base/files/file.h"
  16 #endif
  17
  18 namespace IPC {
  19
  20 class BrokerableAttachment;
  21 class MessageAttachment;
  22
  23 // -----------------------------------------------------------------------------
  24 // A MessageAttachmentSet is an ordered set of MessageAttachment objects. These
  25 // are associated with IPC messages so that attachments, each of which is either
  26 // a platform file or a mojo handle, can be transmitted over the underlying UNIX
  27 // domain socket (for ChannelPosix) or Mojo MessagePipe (for ChannelMojo).
  28 // -----------------------------------------------------------------------------
  29 class IPC_EXPORT MessageAttachmentSet
  30     : public base::RefCountedThreadSafe<MessageAttachmentSet> {
  31  public:
  32   MessageAttachmentSet();
  33
  34   // Return the number of attachments
  35   unsigned size() const;
  36   // Return the number of file descriptors
  37   unsigned num_descriptors() const;
  38   // Return the number of mojo handles in the attachment set
  39   unsigned num_mojo_handles() const;
  40   // Return the number of brokerable attachments in the attachment set.
  41   unsigned num_brokerable_attachments() const;
  42
  43   // Return true if no unconsumed descriptors remain
  44   bool empty() const { return 0 == size(); }
  45
  46   bool AddAttachment(scoped_refptr<MessageAttachment> attachment);
  47
  48   // Take the nth attachment from the beginning of the set, Code using this
  49   // /must/ access the attachments in order, and must do it at most once.
  50   //
  51   // This interface is designed for the deserialising code as it doesn't
  52   // support close flags.
  53   //   returns: an attachment, or nullptr on error
  54   scoped_refptr<MessageAttachment> GetAttachmentAt(unsigned index);
  55
  56   // This must be called after transmitting the descriptors returned by
  57   // PeekDescriptors. It marks all the descriptors as consumed and closes those
  58   // which are auto-close.
  59   void CommitAll();
  60
  61   // Returns a vector of all brokerable attachments.
  62   std::vector<const BrokerableAttachment*> PeekBrokerableAttachments() const;
  63   std::vector<scoped_refptr<BrokerableAttachment>>
  64   GetBrokerableAttachmentsForUpdating();
  65
  66 #if defined(OS_POSIX)
  67   // This is the maximum number of descriptors per message. We need to know this
  68   // because the control message kernel interface has to be given a buffer which
  69   // is large enough to store all the descriptor numbers. Otherwise the kernel
  70   // tells us that it truncated the control data and the extra descriptors are
  71   // lost.
  72   //
  73   // In debugging mode, it's a fatal error to try and add more than this number
  74   // of descriptors to a MessageAttachmentSet.
  75   static const size_t kMaxDescriptorsPerMessage = 7;
  76
  77   // ---------------------------------------------------------------------------
  78   // Interfaces for transmission...
  79
  80   // Fill an array with file descriptors without 'consuming' them. CommitAll
  81   // must be called after these descriptors have been transmitted.
  82   //   buffer: (output) a buffer of, at least, size() integers.
  83   void PeekDescriptors(base::PlatformFile* buffer) const;
  84   // Returns true if any contained file descriptors appear to be handles to a
  85   // directory.
  86   bool ContainsDirectoryDescriptor() const;
  87   // Fetch all filedescriptors with the "auto close" property.
  88   // Used instead of CommitAll() when closing must be handled manually.
  89   void ReleaseFDsToClose(std::vector<base::PlatformFile>* fds);
  90
  91   // ---------------------------------------------------------------------------
  92
  93   // ---------------------------------------------------------------------------
  94   // Interfaces for receiving...
  95
  96   // Set the contents of the set from the given buffer. This set must be empty
  97   // before calling. The auto-close flag is set on all the descriptors so that
  98   // unconsumed descriptors are closed on destruction.
  99   void AddDescriptorsToOwn(const base::PlatformFile* buffer, unsigned count);
 100
 101 #endif  // OS_POSIX
 102
 103   // ---------------------------------------------------------------------------
 104
 105  private:
 106   friend class base::RefCountedThreadSafe<MessageAttachmentSet>;
 107
 108   ~MessageAttachmentSet();
 109
 110   // A vector of attachments of the message, which might be |PlatformFile| or
 111   // |MessagePipe|.
 112   std::vector<scoped_refptr<MessageAttachment>> attachments_;
 113
 114   // This contains the index of the next descriptor which should be consumed.
 115   // It's used in a couple of ways. Firstly, at destruction we can check that
 116   // all the descriptors have been read (with GetNthDescriptor). Secondly, we
 117   // can check that they are read in order.
 118   mutable unsigned consumed_descriptor_highwater_;
 119
 120   DISALLOW_COPY_AND_ASSIGN(MessageAttachmentSet);
 121 };
 122
 123 }  // namespace IPC
 124
 125 #endif  // IPC_IPC_MESSAGE_ATTACHMENT_SET_H_