163 lines
6.6 KiB
C++
163 lines
6.6 KiB
C++
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef IPC_IPC_MESSAGE_ATTACHMENT_SET_H_
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#define IPC_IPC_MESSAGE_ATTACHMENT_SET_H_
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#include <stddef.h>
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#include <vector>
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#include "base/macros.h"
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#include "base/memory/ref_counted.h"
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#include "build/build_config.h"
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#include "ipc/ipc_export.h"
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#if defined(OS_POSIX)
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#include "base/files/file.h"
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#endif
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namespace IPC {
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class BrokerableAttachment;
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class MessageAttachment;
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// -----------------------------------------------------------------------------
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// A MessageAttachmentSet is an ordered set of MessageAttachment objects
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// associated with an IPC message. There are three types of MessageAttachments:
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// 1) TYPE_PLATFORM_FILE is transmitted over the Channel's underlying
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// UNIX domain socket
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// 2) TYPE_MOJO_HANDLE is transmitted over the Mojo MessagePipe.
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// 3) TYPE_BROKERABLE_ATTACHMENT is transmitted by the Attachment Broker.
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// Any given IPC Message can have attachments of type (1) or (2), but not both.
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// These are stored in |attachments_|. Attachments of type (3) are stored in
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// |brokerable_attachments_|.
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//
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// To produce a deterministic ordering, all attachments in |attachments_| are
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// considered to come before those in |brokerable_attachments_|. These
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// attachments are transmitted across different communication channels, and
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// multiplexed by the receiver, so ordering between them cannot be guaranteed.
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//
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// -----------------------------------------------------------------------------
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class IPC_EXPORT MessageAttachmentSet
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: public base::RefCountedThreadSafe<MessageAttachmentSet> {
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public:
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MessageAttachmentSet();
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// Return the number of attachments
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unsigned size() const;
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// Return the number of file descriptors
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unsigned num_descriptors() const;
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// Return the number of mojo handles in the attachment set
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unsigned num_mojo_handles() const;
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// Return the number of brokerable attachments in the attachment set.
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unsigned num_brokerable_attachments() const;
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// Return the number of non-brokerable attachments in the attachment set.
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unsigned num_non_brokerable_attachments() const;
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// Return true if no unconsumed descriptors remain
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bool empty() const { return 0 == size(); }
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// Returns whether the attachment was successfully added.
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// |index| is an output variable. On success, it contains the index of the
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// newly added attachment.
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// |brokerable| is an output variable. On success, it describes which vector
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// the attachment was added to.
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bool AddAttachment(scoped_refptr<MessageAttachment> attachment,
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size_t* index,
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bool* brokerable);
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// Similar to the above method, but without output variables.
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bool AddAttachment(scoped_refptr<MessageAttachment> attachment);
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// Take the nth non-brokerable attachment from the beginning of the vector,
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// Code using this /must/ access the attachments in order, and must do it at
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// most once.
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//
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// This interface is designed for the deserialising code as it doesn't
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// support close flags.
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// returns: an attachment, or nullptr on error
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scoped_refptr<MessageAttachment> GetNonBrokerableAttachmentAt(unsigned index);
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// Similar to GetNonBrokerableAttachmentAt, but there are no ordering
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// requirements.
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scoped_refptr<MessageAttachment> GetBrokerableAttachmentAt(unsigned index);
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// This must be called after transmitting the descriptors returned by
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// PeekDescriptors. It marks all the non-brokerable descriptors as consumed
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// and closes those which are auto-close.
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void CommitAllDescriptors();
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// Returns a vector of all brokerable attachments.
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std::vector<scoped_refptr<IPC::BrokerableAttachment>>
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GetBrokerableAttachments() const;
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// Replaces a placeholder brokerable attachment with |attachment|, matching
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// them by their id.
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void ReplacePlaceholderWithAttachment(
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const scoped_refptr<BrokerableAttachment>& attachment);
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#if defined(OS_POSIX)
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// This is the maximum number of descriptors per message. We need to know this
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// because the control message kernel interface has to be given a buffer which
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// is large enough to store all the descriptor numbers. Otherwise the kernel
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// tells us that it truncated the control data and the extra descriptors are
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// lost.
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//
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// In debugging mode, it's a fatal error to try and add more than this number
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// of descriptors to a MessageAttachmentSet.
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static const size_t kMaxDescriptorsPerMessage = 7;
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// ---------------------------------------------------------------------------
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// Interfaces for transmission...
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// Fill an array with file descriptors without 'consuming' them.
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// CommitAllDescriptors must be called after these descriptors have been
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// transmitted.
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// buffer: (output) a buffer of, at least, size() integers.
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void PeekDescriptors(base::PlatformFile* buffer) const;
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// Returns true if any contained file descriptors appear to be handles to a
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// directory.
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bool ContainsDirectoryDescriptor() const;
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// Fetch all filedescriptors with the "auto close" property. Used instead of
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// CommitAllDescriptors() when closing must be handled manually.
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void ReleaseFDsToClose(std::vector<base::PlatformFile>* fds);
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// ---------------------------------------------------------------------------
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// ---------------------------------------------------------------------------
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// Interfaces for receiving...
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// Set the contents of the set from the given buffer. This set must be empty
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// before calling. The auto-close flag is set on all the descriptors so that
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// unconsumed descriptors are closed on destruction.
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void AddDescriptorsToOwn(const base::PlatformFile* buffer, unsigned count);
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#endif // OS_POSIX
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// ---------------------------------------------------------------------------
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private:
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friend class base::RefCountedThreadSafe<MessageAttachmentSet>;
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~MessageAttachmentSet();
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// All elements either have type TYPE_PLATFORM_FILE or TYPE_MOJO_HANDLE.
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std::vector<scoped_refptr<MessageAttachment>> attachments_;
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// All elements have type TYPE_BROKERABLE_ATTACHMENT.
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std::vector<scoped_refptr<BrokerableAttachment>> brokerable_attachments_;
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// This contains the index of the next descriptor which should be consumed.
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// It's used in a couple of ways. Firstly, at destruction we can check that
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// all the descriptors have been read (with GetNthDescriptor). Secondly, we
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// can check that they are read in order.
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mutable unsigned consumed_descriptor_highwater_;
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DISALLOW_COPY_AND_ASSIGN(MessageAttachmentSet);
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};
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} // namespace IPC
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#endif // IPC_IPC_MESSAGE_ATTACHMENT_SET_H_
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