Move //mojo/{public, edk} underneath //third_party

mojo/edk/system/message_in_transit.h

-// Copyright 2013 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.
-
-#ifndef MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_
-#define MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_
-
-#include <stddef.h>
-#include <stdint.h>
-
-#include <vector>
-
-#include "base/macros.h"
-#include "base/memory/aligned_memory.h"
-#include "base/memory/scoped_ptr.h"
-#include "mojo/edk/system/channel_endpoint_id.h"
-#include "mojo/edk/system/dispatcher.h"
-#include "mojo/edk/system/memory.h"
-#include "mojo/edk/system/system_impl_export.h"
-
-namespace mojo {
-namespace system {
-
-class Channel;
-class TransportData;
-
-// This class is used to represent data in transit. It is thread-unsafe.
-//
-// |MessageInTransit| buffers:
-//
-// A |MessageInTransit| can be serialized by writing the main buffer and then,
-// if it has one, the transport data buffer. Both buffers are
-// |kMessageAlignment|-byte aligned and a multiple of |kMessageAlignment| bytes
-// in size.
-//
-// The main buffer consists of the header (of type |Header|, which is an
-// internal detail of this class) followed immediately by the message data
-// (accessed by |bytes()| and of size |num_bytes()|, and also
-// |kMessageAlignment|-byte aligned), and then any padding needed to make the
-// main buffer a multiple of |kMessageAlignment| bytes in size.
-//
-// See |TransportData| for a description of the (serialized) transport data
-// buffer.
-class MOJO_SYSTEM_IMPL_EXPORT MessageInTransit {
- public:
-  typedef uint16_t Type;
-  // Messages that are forwarded to endpoints.
-  static const Type kTypeEndpoint = 0;
-  // Messages that are consumed by the |Channel|.
-  static const Type kTypeChannel = 1;
-  // Messages that are consumed by the |RawChannel| (implementation).
-  static const Type kTypeRawChannel = 2;
-
-  typedef uint16_t Subtype;
-  // Subtypes for type |kTypeEndpoint|:
-  static const Subtype kSubtypeEndpointData = 0;
-  // Subtypes for type |kTypeChannel|:
-  static const Subtype kSubtypeChannelAttachAndRunEndpoint = 0;
-  static const Subtype kSubtypeChannelRemoveEndpoint = 1;
-  static const Subtype kSubtypeChannelRemoveEndpointAck = 2;
-
-  // Subtypes for type |kTypeRawChannel|:
-  static const Subtype kSubtypeRawChannelPosixExtraPlatformHandles = 0;
-
-  // Messages (the header and data) must always be aligned to a multiple of this
-  // quantity (which must be a power of 2).
-  static const size_t kMessageAlignment = 8;
-
-  // Forward-declare |Header| so that |View| can use it:
- private:
-  struct Header;
-
- public:
-  // This represents a view of serialized message data in a raw buffer.
-  class MOJO_SYSTEM_IMPL_EXPORT View {
-   public:
-    // Constructs a view from the given buffer of the given size. (The size must
-    // be as provided by |MessageInTransit::GetNextMessageSize()|.) The buffer
-    // must remain alive/unmodified through the lifetime of this object.
-    // |buffer| should be |kMessageAlignment|-byte aligned.
-    View(size_t message_size, const void* buffer);
-
-    // Checks that the given |View| appears to be for a valid message, within
-    // predetermined limits (e.g., |num_bytes()| and |main_buffer_size()|, that
-    // |transport_data_buffer()|/|transport_data_buffer_size()| is for valid
-    // transport data -- see |TransportData::ValidateBuffer()|).
-    //
-    // It returns true (and leaves |error_message| alone) if this object appears
-    // to be a valid message (according to the above) and false, pointing
-    // |*error_message| to a suitable error message, if not.
-    bool IsValid(size_t serialized_platform_handle_size,
-                 const char** error_message) const;
-
-    // API parallel to that for |MessageInTransit| itself (mostly getters for
-    // header data).
-    const void* main_buffer() const { return buffer_; }
-    size_t main_buffer_size() const {
-      return RoundUpMessageAlignment(sizeof(Header) + header()->num_bytes);
-    }
-    const void* transport_data_buffer() const {
-      return (total_size() > main_buffer_size())
-                 ? static_cast<const char*>(buffer_) + main_buffer_size()
-                 : nullptr;
-    }
-    size_t transport_data_buffer_size() const {
-      return total_size() - main_buffer_size();
-    }
-    size_t total_size() const { return header()->total_size; }
-    uint32_t num_bytes() const { return header()->num_bytes; }
-    const void* bytes() const {
-      return static_cast<const char*>(buffer_) + sizeof(Header);
-    }
-    Type type() const { return header()->type; }
-    Subtype subtype() const { return header()->subtype; }
-    ChannelEndpointId source_id() const { return header()->source_id; }
-    ChannelEndpointId destination_id() const {
-      return header()->destination_id;
-    }
-
-   private:
-    const Header* header() const { return static_cast<const Header*>(buffer_); }
-
-    const void* const buffer_;
-
-    // Though this struct is trivial, disallow copy and assign, since it doesn't
-    // own its data. (If you're copying/assigning this, you're probably doing
-    // something wrong.)
-    DISALLOW_COPY_AND_ASSIGN(View);
-  };
-
-  // |bytes| is optional; if null, the message data will be zero-initialized.
-  MessageInTransit(Type type,
-                   Subtype subtype,
-                   uint32_t num_bytes,
-                   const void* bytes);
-  // |bytes| should be valid (and non-null), unless |num_bytes| is zero.
-  MessageInTransit(Type type,
-                   Subtype subtype,
-                   uint32_t num_bytes,
-                   UserPointer<const void> bytes);
-  // Constructs a |MessageInTransit| from a |View|.
-  explicit MessageInTransit(const View& message_view);
-
-  ~MessageInTransit();
-
-  // Gets the size of the next message from |buffer|, which has |buffer_size|
-  // bytes currently available, returning true and setting |*next_message_size|
-  // on success. |buffer| should be aligned on a |kMessageAlignment| boundary
-  // (and on success, |*next_message_size| will be a multiple of
-  // |kMessageAlignment|).
-  // TODO(vtl): In |RawChannelPosix|, the alignment requirements are currently
-  // satisified on a faith-based basis.
-  static bool GetNextMessageSize(const void* buffer,
-                                 size_t buffer_size,
-                                 size_t* next_message_size);
-
-  // Makes this message "own" the given set of dispatchers. The dispatchers must
-  // not be referenced from anywhere else (in particular, not from the handle
-  // table), i.e., each dispatcher must have a reference count of 1. This
-  // message must not already have dispatchers.
-  void SetDispatchers(scoped_ptr<DispatcherVector> dispatchers);
-
-  // Sets the |TransportData| for this message. This should only be done when
-  // there are no dispatchers and no existing |TransportData|.
-  void SetTransportData(scoped_ptr<TransportData> transport_data);
-
-  // Serializes any dispatchers to the secondary buffer. This message must not
-  // already have a secondary buffer (so this must only be called once). The
-  // caller must ensure (e.g., by holding on to a reference) that |channel|
-  // stays alive through the call.
-  void SerializeAndCloseDispatchers(Channel* channel);
-
-  // Gets the main buffer and its size (in number of bytes), respectively.
-  const void* main_buffer() const { return main_buffer_.get(); }
-  size_t main_buffer_size() const { return main_buffer_size_; }
-
-  // Gets the transport data buffer (if any).
-  const TransportData* transport_data() const { return transport_data_.get(); }
-  TransportData* transport_data() { return transport_data_.get(); }
-
-  // Gets the total size of the message (see comment in |Header|, below).
-  size_t total_size() const { return header()->total_size; }
-
-  // Gets the size of the message data.
-  uint32_t num_bytes() const { return header()->num_bytes; }
-
-  // Gets the message data (of size |num_bytes()| bytes).
-  const void* bytes() const { return main_buffer_.get() + sizeof(Header); }
-  void* bytes() { return main_buffer_.get() + sizeof(Header); }
-
-  Type type() const { return header()->type; }
-  Subtype subtype() const { return header()->subtype; }
-  ChannelEndpointId source_id() const { return header()->source_id; }
-  ChannelEndpointId destination_id() const { return header()->destination_id; }
-
-  void set_source_id(ChannelEndpointId source_id) {
-    header()->source_id = source_id;
-  }
-  void set_destination_id(ChannelEndpointId destination_id) {
-    header()->destination_id = destination_id;
-  }
-
-  // Gets the dispatchers attached to this message; this may return null if
-  // there are none. Note that the caller may mutate the set of dispatchers
-  // (e.g., take ownership of all the dispatchers, leaving the vector empty).
-  DispatcherVector* dispatchers() { return dispatchers_.get(); }
-
-  // Returns true if this message has dispatchers attached.
-  bool has_dispatchers() const {
-    return dispatchers_ && !dispatchers_->empty();
-  }
-
-  // Rounds |n| up to a multiple of |kMessageAlignment|.
-  static inline size_t RoundUpMessageAlignment(size_t n) {
-    return (n + kMessageAlignment - 1) & ~(kMessageAlignment - 1);
-  }
-
- private:
-  // To allow us to make compile-assertions about |Header| in the .cc file.
-  struct PrivateStructForCompileAsserts;
-
-  // Header for the data (main buffer). Must be a multiple of
-  // |kMessageAlignment| bytes in size. Must be POD.
-  struct Header {
-    // Total size of the message, including the header, the message data
-    // ("bytes") including padding (to make it a multiple of |kMessageAlignment|
-    // bytes), and serialized handle information. Note that this may not be the
-    // correct value if dispatchers are attached but
-    // |SerializeAndCloseDispatchers()| has not been called.
-    uint32_t total_size;
-    Type type;                         // 2 bytes.
-    Subtype subtype;                   // 2 bytes.
-    ChannelEndpointId source_id;       // 4 bytes.
-    ChannelEndpointId destination_id;  // 4 bytes.
-    // Size of actual message data.
-    uint32_t num_bytes;
-    uint32_t unused;
-  };
-
-  const Header* header() const {
-    return reinterpret_cast<const Header*>(main_buffer_.get());
-  }
-  Header* header() { return reinterpret_cast<Header*>(main_buffer_.get()); }
-
-  void ConstructorHelper(Type type, Subtype subtype, uint32_t num_bytes);
-  void UpdateTotalSize();
-
-  const size_t main_buffer_size_;
-  const scoped_ptr<char, base::AlignedFreeDeleter> main_buffer_;  // Never null.
-
-  scoped_ptr<TransportData> transport_data_;  // May be null.
-
-  // Any dispatchers that may be attached to this message. These dispatchers
-  // should be "owned" by this message, i.e., have a ref count of exactly 1. (We
-  // allow a dispatcher entry to be null, in case it couldn't be duplicated for
-  // some reason.)
-  scoped_ptr<DispatcherVector> dispatchers_;
-
-  DISALLOW_COPY_AND_ASSIGN(MessageInTransit);
-};
-
-}  // namespace system
-}  // namespace mojo
-
-#endif  // MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_