1 // Copyright 2013 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.
5 #ifndef MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_
6 #define MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_
13 #include "base/macros.h"
14 #include "base/memory/aligned_memory.h"
15 #include "base/memory/scoped_ptr.h"
16 #include "mojo/edk/system/channel_endpoint_id.h"
17 #include "mojo/edk/system/dispatcher.h"
18 #include "mojo/edk/system/memory.h"
19 #include "mojo/edk/system/system_impl_export.h"
27 // This class is used to represent data in transit. It is thread-unsafe.
29 // |MessageInTransit| buffers:
31 // A |MessageInTransit| can be serialized by writing the main buffer and then,
32 // if it has one, the transport data buffer. Both buffers are
33 // |kMessageAlignment|-byte aligned and a multiple of |kMessageAlignment| bytes
36 // The main buffer consists of the header (of type |Header|, which is an
37 // internal detail of this class) followed immediately by the message data
38 // (accessed by |bytes()| and of size |num_bytes()|, and also
39 // |kMessageAlignment|-byte aligned), and then any padding needed to make the
40 // main buffer a multiple of |kMessageAlignment| bytes in size.
42 // See |TransportData| for a description of the (serialized) transport data
44 class MOJO_SYSTEM_IMPL_EXPORT MessageInTransit {
46 typedef uint16_t Type;
47 // Messages that are forwarded to |MessagePipeEndpoint|s.
48 static const Type kTypeMessagePipeEndpoint = 0;
49 // Messages that are forwarded to |MessagePipe|s.
50 static const Type kTypeMessagePipe = 1;
51 // Messages that are consumed by the |Channel|.
52 static const Type kTypeChannel = 2;
53 // Messages that are consumed by the |RawChannel| (implementation).
54 static const Type kTypeRawChannel = 3;
56 typedef uint16_t Subtype;
57 // Subtypes for type |kTypeMessagePipeEndpoint|:
58 static const Subtype kSubtypeMessagePipeEndpointData = 0;
59 // Subtypes for type |kTypeMessagePipe|:
61 // Subtypes for type |kTypeChannel|:
62 static const Subtype kSubtypeChannelAttachAndRunEndpoint = 0;
63 static const Subtype kSubtypeChannelRemoveMessagePipeEndpoint = 1;
64 static const Subtype kSubtypeChannelRemoveMessagePipeEndpointAck = 2;
66 // Subtypes for type |kTypeRawChannel|:
67 static const Subtype kSubtypeRawChannelPosixExtraPlatformHandles = 0;
69 // Messages (the header and data) must always be aligned to a multiple of this
70 // quantity (which must be a power of 2).
71 static const size_t kMessageAlignment = 8;
73 // Forward-declare |Header| so that |View| can use it:
78 // This represents a view of serialized message data in a raw buffer.
79 class MOJO_SYSTEM_IMPL_EXPORT View {
81 // Constructs a view from the given buffer of the given size. (The size must
82 // be as provided by |MessageInTransit::GetNextMessageSize()|.) The buffer
83 // must remain alive/unmodified through the lifetime of this object.
84 // |buffer| should be |kMessageAlignment|-byte aligned.
85 View(size_t message_size, const void* buffer);
87 // Checks that the given |View| appears to be for a valid message, within
88 // predetermined limits (e.g., |num_bytes()| and |main_buffer_size()|, that
89 // |transport_data_buffer()|/|transport_data_buffer_size()| is for valid
90 // transport data -- see |TransportData::ValidateBuffer()|).
92 // It returns true (and leaves |error_message| alone) if this object appears
93 // to be a valid message (according to the above) and false, pointing
94 // |*error_message| to a suitable error message, if not.
95 bool IsValid(size_t serialized_platform_handle_size,
96 const char** error_message) const;
98 // API parallel to that for |MessageInTransit| itself (mostly getters for
100 const void* main_buffer() const { return buffer_; }
101 size_t main_buffer_size() const {
102 return RoundUpMessageAlignment(sizeof(Header) + header()->num_bytes);
104 const void* transport_data_buffer() const {
105 return (total_size() > main_buffer_size())
106 ? static_cast<const char*>(buffer_) + main_buffer_size()
109 size_t transport_data_buffer_size() const {
110 return total_size() - main_buffer_size();
112 size_t total_size() const { return header()->total_size; }
113 uint32_t num_bytes() const { return header()->num_bytes; }
114 const void* bytes() const {
115 return static_cast<const char*>(buffer_) + sizeof(Header);
117 Type type() const { return header()->type; }
118 Subtype subtype() const { return header()->subtype; }
119 ChannelEndpointId source_id() const { return header()->source_id; }
120 ChannelEndpointId destination_id() const {
121 return header()->destination_id;
125 const Header* header() const { return static_cast<const Header*>(buffer_); }
127 const void* const buffer_;
129 // Though this struct is trivial, disallow copy and assign, since it doesn't
130 // own its data. (If you're copying/assigning this, you're probably doing
132 DISALLOW_COPY_AND_ASSIGN(View);
135 // |bytes| is optional; if null, the message data will be zero-initialized.
136 MessageInTransit(Type type,
140 // |bytes| should be valid (and non-null), unless |num_bytes| is zero.
141 MessageInTransit(Type type,
144 UserPointer<const void> bytes);
145 // Constructs a |MessageInTransit| from a |View|.
146 explicit MessageInTransit(const View& message_view);
150 // Gets the size of the next message from |buffer|, which has |buffer_size|
151 // bytes currently available, returning true and setting |*next_message_size|
152 // on success. |buffer| should be aligned on a |kMessageAlignment| boundary
153 // (and on success, |*next_message_size| will be a multiple of
154 // |kMessageAlignment|).
155 // TODO(vtl): In |RawChannelPosix|, the alignment requirements are currently
156 // satisified on a faith-based basis.
157 static bool GetNextMessageSize(const void* buffer,
159 size_t* next_message_size);
161 // Makes this message "own" the given set of dispatchers. The dispatchers must
162 // not be referenced from anywhere else (in particular, not from the handle
163 // table), i.e., each dispatcher must have a reference count of 1. This
164 // message must not already have dispatchers.
165 void SetDispatchers(scoped_ptr<DispatcherVector> dispatchers);
167 // Sets the |TransportData| for this message. This should only be done when
168 // there are no dispatchers and no existing |TransportData|.
169 void SetTransportData(scoped_ptr<TransportData> transport_data);
171 // Serializes any dispatchers to the secondary buffer. This message must not
172 // already have a secondary buffer (so this must only be called once). The
173 // caller must ensure (e.g., by holding on to a reference) that |channel|
174 // stays alive through the call.
175 void SerializeAndCloseDispatchers(Channel* channel);
177 // Gets the main buffer and its size (in number of bytes), respectively.
178 const void* main_buffer() const { return main_buffer_.get(); }
179 size_t main_buffer_size() const { return main_buffer_size_; }
181 // Gets the transport data buffer (if any).
182 const TransportData* transport_data() const { return transport_data_.get(); }
183 TransportData* transport_data() { return transport_data_.get(); }
185 // Gets the total size of the message (see comment in |Header|, below).
186 size_t total_size() const { return header()->total_size; }
188 // Gets the size of the message data.
189 uint32_t num_bytes() const { return header()->num_bytes; }
191 // Gets the message data (of size |num_bytes()| bytes).
192 const void* bytes() const { return main_buffer_.get() + sizeof(Header); }
193 void* bytes() { return main_buffer_.get() + sizeof(Header); }
195 Type type() const { return header()->type; }
196 Subtype subtype() const { return header()->subtype; }
197 ChannelEndpointId source_id() const { return header()->source_id; }
198 ChannelEndpointId destination_id() const { return header()->destination_id; }
200 void set_source_id(ChannelEndpointId source_id) {
201 header()->source_id = source_id;
203 void set_destination_id(ChannelEndpointId destination_id) {
204 header()->destination_id = destination_id;
207 // Gets the dispatchers attached to this message; this may return null if
208 // there are none. Note that the caller may mutate the set of dispatchers
209 // (e.g., take ownership of all the dispatchers, leaving the vector empty).
210 DispatcherVector* dispatchers() { return dispatchers_.get(); }
212 // Returns true if this message has dispatchers attached.
213 bool has_dispatchers() const {
214 return dispatchers_ && !dispatchers_->empty();
217 // Rounds |n| up to a multiple of |kMessageAlignment|.
218 static inline size_t RoundUpMessageAlignment(size_t n) {
219 return (n + kMessageAlignment - 1) & ~(kMessageAlignment - 1);
223 // To allow us to make compile-assertions about |Header| in the .cc file.
224 struct PrivateStructForCompileAsserts;
226 // Header for the data (main buffer). Must be a multiple of
227 // |kMessageAlignment| bytes in size. Must be POD.
229 // Total size of the message, including the header, the message data
230 // ("bytes") including padding (to make it a multiple of |kMessageAlignment|
231 // bytes), and serialized handle information. Note that this may not be the
232 // correct value if dispatchers are attached but
233 // |SerializeAndCloseDispatchers()| has not been called.
235 Type type; // 2 bytes.
236 Subtype subtype; // 2 bytes.
237 ChannelEndpointId source_id; // 4 bytes.
238 ChannelEndpointId destination_id; // 4 bytes.
239 // Size of actual message data.
244 const Header* header() const {
245 return reinterpret_cast<const Header*>(main_buffer_.get());
247 Header* header() { return reinterpret_cast<Header*>(main_buffer_.get()); }
249 void ConstructorHelper(Type type, Subtype subtype, uint32_t num_bytes);
250 void UpdateTotalSize();
252 const size_t main_buffer_size_;
253 const scoped_ptr<char, base::AlignedFreeDeleter> main_buffer_; // Never null.
255 scoped_ptr<TransportData> transport_data_; // May be null.
257 // Any dispatchers that may be attached to this message. These dispatchers
258 // should be "owned" by this message, i.e., have a ref count of exactly 1. (We
259 // allow a dispatcher entry to be null, in case it couldn't be duplicated for
261 scoped_ptr<DispatcherVector> dispatchers_;
263 DISALLOW_COPY_AND_ASSIGN(MessageInTransit);
266 } // namespace system
269 #endif // MOJO_EDK_SYSTEM_MESSAGE_IN_TRANSIT_H_