Introduce RawVarData and associated classes for serializing PP_Vars

ppapi/proxy/raw_var_data.h

+// Copyright (c) 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 PPAPI_PROXY_RAW_VAR_DATA_H_
+#define PPAPI_PROXY_RAW_VAR_DATA_H_
+
+#include <vector>
+
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+#include "ppapi/c/pp_instance.h"
+#include "ppapi/c/pp_var.h"
+#include "ppapi/proxy/ppapi_param_traits.h"
+#include "ppapi/proxy/ppapi_proxy_export.h"
+#include "ppapi/proxy/serialized_handle.h"
+
+class PickleIterator;
+
+namespace IPC {
+class Message;
+}
+
+namespace ppapi {
+namespace proxy {
+
+class RawVarData;
+
+typedef base::Callback<void(IPC::Message*, const SerializedHandle&)>
+    HandleWriter;
+
+// Contains the data associated with a graph of connected PP_Vars. Useful for
+// serializing/deserializing a graph of PP_Vars. First we compute the transitive
+// closure of the given PP_Var to find all PP_Vars which are referenced by that
+// var. A RawVarData object is created for each of these vars. We then write
+// data contained in each RawVarData to the message. The format looks like this:
+//    idx | size     | (number of vars in the graph)
+//     0  | var type |
+//        | var data |
+//     1  | var type |
+//        | var data |
+//     2  | var type |
+//        | var data |
+//        |   ....   |
+//
+// Vars that reference other vars (such as Arrays or Dictionaries) use indices
+// into the message to denote which PP_Var is pointed to.
+class PPAPI_PROXY_EXPORT RawVarDataGraph {
+ public:
+  // Construct a RawVarDataGraph from a given root PP_Var. A null pointer
+  // is returned upon failure.
+  static scoped_ptr<RawVarDataGraph> Create(const PP_Var& var,
+                                            PP_Instance instance);
+
+  // Constructs an empty RawVarDataGraph.
+  RawVarDataGraph();
+  ~RawVarDataGraph();
+
+  // Construct a new PP_Var from the graph. All of the PP_Vars referenced by
+  // the returned PP_Var are also constructed. Each PP_Var created has a
+  // ref-count equal to the number of references it has in the graph of vars.
+  // The returned var (the "root") has one additional reference.
+  PP_Var CreatePPVar(PP_Instance instance);
+
+  // Write the graph to a message using the given HandleWriter.
+  void Write(IPC::Message* m, const HandleWriter& handle_writer);
+  // Write the graph to a message using the default handle writer.
+  void Write(IPC::Message* m);
+
+  // Create a RawVarDataGraph from the given message.
+  static scoped_ptr<RawVarDataGraph> Read(const IPC::Message* m,
+                                          PickleIterator* iter);
+
+  // A list of the nodes in the graph.
+  ScopedVector<RawVarData> data_;
+};
+
+// Abstract base class for the data contained in a PP_Var.
+class RawVarData {
+ public:
+  // Create a new, empty RawVarData for the given type.
+  static RawVarData* Create(PP_VarType type);
+  RawVarData();
+  virtual ~RawVarData();
+
+  // Returns the type of the PP_Var represented by the RawVarData.
+  virtual PP_VarType Type() = 0;
+
+  // Initializes a RawVarData from a PP_Var. Returns true on success.
+  virtual bool Init(const PP_Var& var, PP_Instance instance) = 0;
+
+  // Create a PP_Var from the raw data contained in this object.
+  virtual PP_Var CreatePPVar(PP_Instance instance) = 0;
+  // Some PP_Vars may require 2-step initialization. For example, they may
+  // reference other PP_Vars which had not yet been created when |CreatePPVar|
+  // was called. The original var created with |CreatePPVar| is passed back in,
+  // along with the graph it is a part of to be initialized.
+  virtual void PopulatePPVar(const PP_Var& var,
+                             const std::vector<PP_Var>& graph) = 0;
+
+  // Writes the RawVarData to a message.
+  virtual void Write(IPC::Message* m,
+                     const HandleWriter& handle_writer) = 0;
+  // Reads the RawVarData from a message. Returns true on success.
+  virtual bool Read(PP_VarType type,
+                    const IPC::Message* m,
+                    PickleIterator* iter) = 0;
+
+  bool initialized() { return initialized_; }
+
+ protected:
+  bool initialized_;
+};
+
+// A RawVarData class for PP_Vars which are value types.
+class BasicRawVarData : public RawVarData {
+ public:
+  BasicRawVarData();
+  virtual ~BasicRawVarData();
+
+  // RawVarData implementation.
+  virtual PP_VarType Type() OVERRIDE;
+  virtual bool Init(const PP_Var& var, PP_Instance instance) OVERRIDE;
+  virtual PP_Var CreatePPVar(PP_Instance instance) OVERRIDE;
+  virtual void PopulatePPVar(const PP_Var& var,
+                             const std::vector<PP_Var>& graph) OVERRIDE;
+  virtual void Write(IPC::Message* m,
+                     const HandleWriter& handle_writer) OVERRIDE;
+  virtual bool Read(PP_VarType type,
+                    const IPC::Message* m,
+                    PickleIterator* iter) OVERRIDE;
+
+ private:
+  PP_Var var_;
+};
+
+// A RawVarData class for string PP_Vars.
+class StringRawVarData : public RawVarData {
+ public:
+  StringRawVarData();
+  virtual ~StringRawVarData();
+
+  // RawVarData implementation.
+  virtual PP_VarType Type() OVERRIDE;
+  virtual bool Init(const PP_Var& var, PP_Instance instance) OVERRIDE;
+  virtual PP_Var CreatePPVar(PP_Instance instance) OVERRIDE;
+  virtual void PopulatePPVar(const PP_Var& var,
+                             const std::vector<PP_Var>& graph) OVERRIDE;
+  virtual void Write(IPC::Message* m,
+                     const HandleWriter& handle_writer) OVERRIDE;
+  virtual bool Read(PP_VarType type,
+                    const IPC::Message* m,
+                    PickleIterator* iter) OVERRIDE;
+
+ private:
+  // The data in the string.
+  std::string data_;
+};
+
+// A RawVarData class for array buffer PP_Vars.
+class ArrayBufferRawVarData : public RawVarData {
+ public:
+  // Enum for array buffer message types.
+  enum ShmemType {
+    ARRAY_BUFFER_NO_SHMEM,
+    ARRAY_BUFFER_SHMEM_HOST,
+    ARRAY_BUFFER_SHMEM_PLUGIN,
+  };
+
+  ArrayBufferRawVarData();
+  virtual ~ArrayBufferRawVarData();
+
+  // RawVarData implementation.
+  virtual PP_VarType Type() OVERRIDE;
+  virtual bool Init(const PP_Var& var, PP_Instance instance) OVERRIDE;
+  virtual PP_Var CreatePPVar(PP_Instance instance) OVERRIDE;
+  virtual void PopulatePPVar(const PP_Var& var,
+                             const std::vector<PP_Var>& graph) OVERRIDE;
+  virtual void Write(IPC::Message* m,
+                     const HandleWriter& handle_writer) OVERRIDE;
+  virtual bool Read(PP_VarType type,
+                    const IPC::Message* m,
+                    PickleIterator* iter) OVERRIDE;
+
+ private:
+  // The type of the storage underlying the array buffer.
+  ShmemType type_;
+  // The data in the buffer. Valid for |type_| == ARRAY_BUFFER_NO_SHMEM.
+  std::string data_;
+  // Host shmem handle. Valid for |type_| == ARRAY_BUFFER_SHMEM_HOST.
+  int host_shm_handle_id_;
+  // Plugin shmem handle. Valid for |type_| == ARRAY_BUFFER_SHMEM_PLUGIN.
+  SerializedHandle plugin_shm_handle_;
+};
+
+// A RawVarData class for array PP_Vars.
+class ArrayRawVarData : public RawVarData {
+ public:
+  ArrayRawVarData();
+  virtual ~ArrayRawVarData();
+
+  void AddChild(size_t element);
+
+  // RawVarData implementation.
+  virtual PP_VarType Type() OVERRIDE;
+  virtual bool Init(const PP_Var& var, PP_Instance instance) OVERRIDE;
+  virtual PP_Var CreatePPVar(PP_Instance instance) OVERRIDE;
+  virtual void PopulatePPVar(const PP_Var& var,
+                             const std::vector<PP_Var>& graph) OVERRIDE;
+  virtual void Write(IPC::Message* m,
+                     const HandleWriter& handle_writer) OVERRIDE;
+  virtual bool Read(PP_VarType type,
+                    const IPC::Message* m,
+                    PickleIterator* iter) OVERRIDE;
+
+ private:
+  std::vector<size_t> children_;
+};
+
+// A RawVarData class for dictionary PP_Vars.
+class DictionaryRawVarData : public RawVarData {
+ public:
+  DictionaryRawVarData();
+  virtual ~DictionaryRawVarData();
+
+  void AddChild(const std::string& key, size_t value);
+
+  // RawVarData implementation.
+  virtual PP_VarType Type() OVERRIDE;
+  virtual bool Init(const PP_Var& var, PP_Instance instance) OVERRIDE;
+  virtual PP_Var CreatePPVar(PP_Instance instance) OVERRIDE;
+  virtual void PopulatePPVar(const PP_Var& var,
+                             const std::vector<PP_Var>& graph) OVERRIDE;
+  virtual void Write(IPC::Message* m,
+                     const HandleWriter& handle_writer) OVERRIDE;
+  virtual bool Read(PP_VarType type,
+                    const IPC::Message* m,
+                    PickleIterator* iter) OVERRIDE;
+
+ private:
+  std::vector<std::pair<std::string, size_t> > children_;
+};
+
+}  // namespace proxy
+}  // namespace ppapi
+
+#endif  // PPAPI_PROXY_RAW_VAR_DATA_H_