chromecast/media/cma/ipc/media_message.h

   1 // Copyright 2014 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 CHROMECAST_MEDIA_CMA_IPC_MEDIA_MESSAGE_H_
   6 #define CHROMECAST_MEDIA_CMA_IPC_MEDIA_MESSAGE_H_
   7
   8 #include <stddef.h>
   9
  10 #include "base/basictypes.h"
  11 #include "base/callback.h"
  12 #include "base/macros.h"
  13 #include "base/memory/scoped_ptr.h"
  14
  15 namespace chromecast {
  16 namespace media {
  17 class MediaMemoryChunk;
  18
  19 // MediaMessage -
  20 // Represents a media message, including:
  21 // - a message header that gives for example the message size or its type,
  22 // - the content of the message,
  23 // - and some possible padding if the content does not occupy the whole
  24 //   reserved space.
  25 //
  26 class MediaMessage {
  27  public:
  28   // Memory allocator: given a number of bytes to allocate,
  29   // return the pointer to the allocated block if successful
  30   // or NULL if allocation failed.
  31   typedef base::Callback<scoped_ptr<MediaMemoryChunk>(size_t)>
  32       MemoryAllocatorCB;
  33
  34   // Creates a message with no associated memory for its content, i.e.
  35   // each write on this message is a dummy operation.
  36   // This type of message can be useful to calculate first the size of the
  37   // message, before allocating the real message.
  38   static scoped_ptr<MediaMessage> CreateDummyMessage(uint32 type);
  39
  40   // Creates a message with a capacity of at least |msg_content_capacity|
  41   // bytes. The actual content size can be smaller than its capacity.
  42   // The message can be populated with some Write functions.
  43   static scoped_ptr<MediaMessage> CreateMessage(
  44       uint32 type,
  45       const MemoryAllocatorCB& memory_allocator,
  46       size_t msg_content_capacity);
  47
  48   // Creates a message of type |type| whose serialized structure is stored
  49   // in |mem|.
  50   static scoped_ptr<MediaMessage> CreateMessage(
  51       uint32 type,
  52       scoped_ptr<MediaMemoryChunk> mem);
  53
  54   // Creates a message from a memory area which already contains
  55   // the serialized structure of the message.
  56   // Only Read functions can be invoked on this type of message.
  57   static scoped_ptr<MediaMessage> MapMessage(
  58       scoped_ptr<MediaMemoryChunk> mem);
  59
  60   // Return the minimum size of a message.
  61   static size_t minimum_msg_size() {
  62     return offsetof(SerializedMsg, content);
  63   }
  64
  65   ~MediaMessage();
  66
  67   // Indicate whether the underlying serialized structure of the message is
  68   // available.
  69   // Note: the serialized structure might be unavailable in case of a dummy
  70   // message or if the underlying memory has been invalidated.
  71   bool IsSerializedMsgAvailable() const;
  72
  73   // Return the message and the total size of the message
  74   // incuding the header, the content and the possible padding.
  75   const void* msg() const { return msg_read_only_; }
  76   size_t size() const { return cached_msg_.header.size; }
  77
  78   // Return the size of the message without padding.
  79   size_t actual_size() const {
  80     return minimum_msg_size() + cached_msg_.header.content_size;
  81   }
  82
  83   // Return the size of the content of the message.
  84   size_t content_size() const { return cached_msg_.header.content_size; }
  85
  86   // Return the type of the message.
  87   uint32 type() const { return cached_msg_.header.type; }
  88
  89   // Append a POD to the message.
  90   // Return true if the POD has been succesfully written.
  91   template<typename T> bool WritePod(T* const& pod);
  92   template<typename T> bool WritePod(const T& pod) {
  93     return WriteBuffer(&pod, sizeof(T));
  94   }
  95
  96   // Append a raw buffer to the message.
  97   bool WriteBuffer(const void* src, size_t size);
  98
  99   // Read a POD from the message.
 100   template<typename T> bool ReadPod(T* pod) {
 101     return ReadBuffer(pod, sizeof(T));
 102   }
 103
 104   // Read |size| bytes from the message from the last read position
 105   // and write it to |dst|.
 106   bool ReadBuffer(void* dst, size_t size);
 107
 108   // Return a pointer to a buffer of size |size|.
 109   // Return NULL if not successful.
 110   const void* GetBuffer(size_t size);
 111   void* GetWritableBuffer(size_t size);
 112
 113  private:
 114   MediaMessage(uint32 type, size_t msg_size);
 115   MediaMessage(uint32 type, scoped_ptr<MediaMemoryChunk> memory);
 116   MediaMessage(scoped_ptr<MediaMemoryChunk> memory);
 117
 118   struct Header {
 119     // Total size of the message (including both header & content).
 120     uint32 size;
 121     // Indicate the message type.
 122     uint32 type;
 123     // Actual size of the content in the message.
 124     uint32 content_size;
 125   };
 126
 127   struct SerializedMsg {
 128     // Message header.
 129     Header header;
 130
 131     // Start of the content of the message.
 132     // Use uint8_t since no special alignment is needed.
 133     uint8 content;
 134   };
 135
 136   // Indicate whether the message is a dummy message, i.e. a message without
 137   // a complete underlying serialized structure: only the message header is
 138   // available.
 139   bool is_dummy_msg_;
 140
 141   // |cached_msg_| is used for 2 purposes:
 142   // - to create a dummy message
 143   // - for security purpose: cache the msg header to avoid browser security
 144   // issues.
 145   SerializedMsg cached_msg_;
 146   Header* const cached_header_;
 147
 148   SerializedMsg* msg_;
 149   SerializedMsg* msg_read_only_;
 150
 151   // Memory allocated to store the underlying serialized structure into memory.
 152   // Note: a dummy message has no underlying serialized structure:
 153   // |mem_| is a null pointer in that case.
 154   scoped_ptr<MediaMemoryChunk> mem_;
 155
 156   // Read iterator into the message.
 157   size_t rd_offset_;
 158
 159   DISALLOW_COPY_AND_ASSIGN(MediaMessage);
 160 };
 161
 162 }  // namespace media
 163 }  // namespace chromecast
 164
 165 #endif