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