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// Copyright (c) 2012 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 <string>
#include <vector>
#include "base/basictypes.h"
#include "base/memory/ref_counted.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/shared_memory.h"
#include "ppapi/c/pp_instance.h"
#include "ppapi/c/pp_var.h"
#include "ppapi/proxy/ppapi_proxy_export.h"
#include "ppapi/proxy/raw_var_data.h"
#include "ppapi/proxy/serialized_handle.h"
#include "ppapi/proxy/serialized_structs.h"
#include "ppapi/proxy/var_serialization_rules.h"
namespace base {
class PickleIterator;
namespace IPC {
class Message;
namespace ppapi {
namespace proxy {
class Dispatcher;
class VarSerializationRules;
// This class encapsulates a var so that we can serialize and deserialize it.
// The problem is that for strings, serialization and deserialization requires
// knowledge from outside about how to get at or create a string. So this
// object groups the var with a dispatcher so that string values can be set or
// gotten.
// Declare IPC messages as using this type, but don't use it directly (it has
// no useful public methods). Instead, instantiate one of the helper classes
// below which are conveniently named for each use case to prevent screwups.
// Design background
// -----------------
// This is sadly super complicated. The IPC system needs a consistent type to
// use for sending and receiving vars (this is a SerializedVar). But there are
// different combinations of reference counting for sending and receiving
// objects and for dealing with strings
// This makes SerializedVar complicated and easy to mess up. To make it
// reasonable to use, all functions are protected and there are use-specific
// classes that each encapsulate exactly one type of use in a way that typically
// won't compile if you do the wrong thing.
// The IPC system is designed to pass things around and will make copies in
// some cases, so our system must be designed so that this stuff will work.
// This is challenging when the SerializedVar must do some cleanup after the
// message is sent. To work around this, we create an inner class using a
// linked_ptr so all copies of a SerializedVar can share and we can guarantee
// that the actual data will get cleaned up on shutdown.
// Constness
// ---------
// SerializedVar basically doesn't support const. Everything is mutable and
// most functions are declared const. This unfortunateness is because of the
// way the IPC system works. When deserializing, it will have a const
// SerializedVar in a Tuple and this will be given to the function. We kind of
// want to modify that to convert strings and do refcounting.
// The helper classes used for accessing the SerializedVar have more reasonable
// behavior and will enforce that you don't do stupid things.
class PPAPI_PROXY_EXPORT SerializedVar {
// Backend implementation for IPC::ParamTraits<SerializedVar>.
void WriteToMessage(IPC::Message* m) const {
// If ReadFromMessage has been called, WriteDataToMessage will write the var
// that has been read from ReadFromMessage back to a message. This is used
// when converting handles for use in NaCl.
void WriteDataToMessage(IPC::Message* m,
const HandleWriter& handle_writer) const {
inner_->WriteDataToMessage(m, handle_writer);
bool ReadFromMessage(const IPC::Message* m, base::PickleIterator* iter) {
return inner_->ReadFromMessage(m, iter);
bool is_valid_var() const {
return inner_->is_valid_var();
// Returns the shared memory handles associated with this SerializedVar.
std::vector<SerializedHandle*> GetHandles() const {
return inner_->GetHandles();
friend class SerializedVarReceiveInput;
friend class SerializedVarReturnValue;
friend class SerializedVarOutParam;
friend class SerializedVarSendInput;
friend class SerializedVarSendInputShmem;
friend class SerializedVarTestConstructor;
friend class SerializedVarVectorReceiveInput;
class PPAPI_PROXY_EXPORT Inner : public base::RefCounted<Inner> {
Inner(VarSerializationRules* serialization_rules);
VarSerializationRules* serialization_rules() {
return serialization_rules_.get();
void set_serialization_rules(VarSerializationRules* serialization_rules) {
serialization_rules_ = serialization_rules;
bool is_valid_var() const {
return is_valid_var_;
std::vector<SerializedHandle*> GetHandles() {
return (raw_var_data_ ? raw_var_data_->GetHandles() :
// See outer class's declarations above.
PP_Var GetVar();
void SetVar(PP_Var var);
void SetInstance(PP_Instance instance);
// For the SerializedVarTestConstructor, this writes the Var value as if
// it was just received off the wire, without any serialization rules.
void ForceSetVarValueForTest(PP_Var value);
void WriteToMessage(IPC::Message* m) const;
void WriteDataToMessage(IPC::Message* m,
const HandleWriter& handle_writer) const;
bool ReadFromMessage(const IPC::Message* m, base::PickleIterator* iter);
// Sets the cleanup mode. See the CleanupMode enum below.
void SetCleanupModeToEndSendPassRef();
void SetCleanupModeToEndReceiveCallerOwned();
enum CleanupMode {
// The serialized var won't do anything special in the destructor
// (default).
// The serialized var will call EndSendPassRef in the destructor.
// The serialized var will call EndReceiveCallerOwned in the destructor.
// Rules for serializing and deserializing vars for this process type.
// This may be NULL, but must be set before trying to serialize to IPC when
// sending, or before converting back to a PP_Var when receiving.
scoped_refptr<VarSerializationRules> serialization_rules_;
// If this is set to VARTYPE_STRING and the '' is 0, then the
// string_from_ipc_ holds the string. This means that the caller hasn't
// called Deserialize with a valid Dispatcher yet, which is how we can
// convert the serialized string value to a PP_Var string ID.
// This var may not be complete until the serialization rules are set when
// reading from IPC since we'll need that to convert the string_value to
// a string ID. Before this, the as_id will be 0 for VARTYPE_STRING.
PP_Var var_;
PP_Instance instance_;
CleanupMode cleanup_mode_;
// If the var is not properly serialized, this will be false.
bool is_valid_var_;
#ifndef NDEBUG
// When being sent or received over IPC, we should only be serialized or
// deserialized once. These flags help us assert this is true.
mutable bool has_been_serialized_;
mutable bool has_been_deserialized_;
// ReadFromMessage() may be called on the I/O thread, e.g., when reading the
// reply to a sync message. We cannot use the var tracker on the I/O thread,
// which means we cannot create some types of PP_Var
// (e.g. PP_VARTYPE_STRING). The data is stored in |raw_var_data_| and the
// PP_Var is constructed when |GetVar()| is called.
scoped_ptr<RawVarDataGraph> raw_var_data_;
SerializedVar(VarSerializationRules* serialization_rules);
mutable scoped_refptr<Inner> inner_;
// Helpers for message sending side --------------------------------------------
// For sending a value to the remote side.
// Example for API:
// void MyFunction(PP_Var)
// IPC message:
// IPC_MESSAGE_ROUTED1(MyFunction, SerializedVar);
// Sender would be:
// void MyFunctionProxy(PP_Var param) {
// Send(new MyFunctionMsg(SerializedVarSendInput(dispatcher, param));
// }
class PPAPI_PROXY_EXPORT SerializedVarSendInput : public SerializedVar {
SerializedVarSendInput(Dispatcher* dispatcher, const PP_Var& var);
// Helper function for serializing a vector of input vars for serialization.
static void ConvertVector(Dispatcher* dispatcher,
const PP_Var* input,
size_t input_count,
std::vector<SerializedVar>* output);
// Disallow the empty constructor, but keep the default copy constructor
// which is required to send the object to the IPC system.
// Specialization for optionally sending over shared memory.
class PPAPI_PROXY_EXPORT SerializedVarSendInputShmem : public SerializedVar {
SerializedVarSendInputShmem(Dispatcher* dispatcher, const PP_Var& var,
const PP_Instance& instance);
// Disallow the empty constructor, but keep the default copy constructor
// which is required to send the object to the IPC system.
// For the calling side of a function returning a var. The sending side uses
// SerializedVarReturnValue.
// Example for API:
// PP_Var MyFunction()
// IPC message:
// IPC_SYNC_MESSAGE_ROUTED0_1(MyFunction, SerializedVar);
// Message handler would be:
// PP_Var MyFunctionProxy() {
// ReceiveSerializedVarReturnValue result;
// Send(new MyFunctionMsg(&result));
// return result.Return(dispatcher());
// }
// TODO(yzshen): Move the dispatcher parameter to the constructor and store a
// VarSerializationRules reference instead, in case the dispatcher is destroyed
// while waiting for reply to the sync message.
class PPAPI_PROXY_EXPORT ReceiveSerializedVarReturnValue
: public SerializedVar {
// Note that we can't set the dispatcher in the constructor because the
// data will be overridden when the return value is set. This constructor is
// normally used in the pattern above (operator= will be implicitly invoked
// when the sync message writes the output values).
// This constructor can be used when deserializing manually. This is useful
// when you're getting strings "returned" via a struct and need to manually
// get the PP_Vars out. In this case just do:
// ReceiveSerializedVarReturnValue(serialized).Return(dispatcher);
explicit ReceiveSerializedVarReturnValue(const SerializedVar& serialized);
PP_Var Return(Dispatcher* dispatcher);
// Example for API:
// "void MyFunction(PP_Var* exception);"
// IPC message:
// IPC_SYNC_MESSAGE_ROUTED0_1(MyFunction, SerializedVar);
// Message handler would be:
// void OnMsgMyFunction(PP_Var* exception) {
// ReceiveSerializedException se(dispatcher(), exception)
// Send(new PpapiHostMsg_Foo(&se));
// }
class PPAPI_PROXY_EXPORT ReceiveSerializedException : public SerializedVar {
ReceiveSerializedException(Dispatcher* dispatcher, PP_Var* exception);
// Returns true if the exception passed in the constructor is set. Check
// this before actually issuing the IPC.
bool IsThrown() const;
// The input/output exception we're wrapping. May be NULL.
PP_Var* exception_;
// Helper class for when we're returning a vector of Vars. When it goes out
// of scope it will automatically convert the vector filled by the IPC layer
// into the array specified by the constructor params.
// Example for API:
// "void MyFunction(uint32_t* count, PP_Var** vars);"
// IPC message:
// IPC_SYNC_MESSAGE_ROUTED0_1(MyFunction, std::vector<SerializedVar>);
// Proxy function:
// void MyFunction(uint32_t* count, PP_Var** vars) {
// ReceiveSerializedVarVectorOutParam vect(dispatcher, count, vars);
// Send(new MyMsg(vect.OutParam()));
// }
class PPAPI_PROXY_EXPORT ReceiveSerializedVarVectorOutParam {
ReceiveSerializedVarVectorOutParam(Dispatcher* dispatcher,
uint32_t* output_count,
PP_Var** output);
std::vector<SerializedVar>* OutParam();
Dispatcher* dispatcher_;
uint32_t* output_count_;
PP_Var** output_;
std::vector<SerializedVar> vector_;
// Helpers for message receiving side ------------------------------------------
// For receiving a value from the remote side.
// Example for API:
// void MyFunction(PP_Var)
// IPC message:
// IPC_MESSAGE_ROUTED1(MyFunction, SerializedVar);
// Message handler would be:
// void OnMsgMyFunction(SerializedVarReceiveInput param) {
// MyFunction(param.Get());
// }
class PPAPI_PROXY_EXPORT SerializedVarReceiveInput {
// We rely on the implicit constructor here since the IPC layer will call
// us with a SerializedVar. Pass this object by value, the copy constructor
// will pass along the pointer (as cheap as passing a pointer arg).
SerializedVarReceiveInput(const SerializedVar& serialized);
PP_Var Get(Dispatcher* dispatcher);
PP_Var GetForInstance(Dispatcher* dispatcher, PP_Instance instance);
bool is_valid_var() { return serialized_.is_valid_var(); }
const SerializedVar& serialized_;
// For receiving an input vector of vars from the remote side.
// Example:
// OnMsgMyFunction(SerializedVarVectorReceiveInput vector) {
// uint32_t size;
// PP_Var* array = vector.Get(dispatcher, &size);
// MyFunction(size, array);
// }
class PPAPI_PROXY_EXPORT SerializedVarVectorReceiveInput {
SerializedVarVectorReceiveInput(const std::vector<SerializedVar>& serialized);
// Only call Get() once. It will return a pointer to the converted array and
// place the array size in the out param. Will return NULL when the array is
// empty.
PP_Var* Get(Dispatcher* dispatcher, uint32_t* array_size);
const std::vector<SerializedVar>& serialized_;
// Filled by Get().
std::vector<PP_Var> deserialized_;
// For the receiving side of a function returning a var. The calling side uses
// ReceiveSerializedVarReturnValue.
// Example for API:
// PP_Var MyFunction()
// IPC message:
// IPC_SYNC_MESSAGE_ROUTED0_1(MyFunction, SerializedVar);
// Message handler would be:
// void OnMsgMyFunction(SerializedVarReturnValue result) {
// result.Return(dispatcher(), MyFunction());
// }
class PPAPI_PROXY_EXPORT SerializedVarReturnValue {
// We rely on the implicit constructor here since the IPC layer will call
// us with a SerializedVar*. Pass this object by value, the copy constructor
// will pass along the pointer (as cheap as passing a pointer arg).
SerializedVarReturnValue(SerializedVar* serialized);
void Return(Dispatcher* dispatcher, const PP_Var& var);
// Helper function for code that doesn't use the pattern above, but gets
// a return value from the remote side via a struct. You can pass in the
// SerializedVar and a PP_Var will be created with return value semantics.
static SerializedVar Convert(Dispatcher* dispatcher, const PP_Var& var);
SerializedVar* serialized_;
// For writing an out param to the remote side.
// Example for API:
// "void MyFunction(PP_Var* out);"
// IPC message:
// IPC_SYNC_MESSAGE_ROUTED0_1(MyFunction, SerializedVar);
// Message handler would be:
// void OnMsgMyFunction(SerializedVarOutParam out_param) {
// MyFunction(out_param.OutParam(dispatcher()));
// }
class PPAPI_PROXY_EXPORT SerializedVarOutParam {
// We rely on the implicit constructor here since the IPC layer will call
// us with a SerializedVar*. Pass this object by value, the copy constructor
// will pass along the pointer (as cheap as passing a pointer arg).
SerializedVarOutParam(SerializedVar* serialized);
// Call this function only once. The caller should write its result to the
// returned var pointer before this class goes out of scope. The var's
// initial value will be VARTYPE_UNDEFINED.
PP_Var* OutParam(Dispatcher* dispatcher);
SerializedVar* serialized_;
// This is the value actually written by the code and returned by OutParam.
// We'll write this into serialized_ in our destructor.
PP_Var writable_var_;
Dispatcher* dispatcher_;
// For returning an array of PP_Vars to the other side and transferring
// ownership.
class PPAPI_PROXY_EXPORT SerializedVarVectorOutParam {
SerializedVarVectorOutParam(std::vector<SerializedVar>* serialized);
uint32_t* CountOutParam() { return &count_; }
PP_Var** ArrayOutParam(Dispatcher* dispatcher);
Dispatcher* dispatcher_;
std::vector<SerializedVar>* serialized_;
uint32_t count_;
PP_Var* array_;
// For tests that just want to construct a SerializedVar for giving it to one
// of the other classes. This emulates a SerializedVar just received over the
// wire from another process.
class PPAPI_PROXY_EXPORT SerializedVarTestConstructor : public SerializedVar {
// For POD-types and objects.
explicit SerializedVarTestConstructor(const PP_Var& pod_var);
// For strings.
explicit SerializedVarTestConstructor(const std::string& str);
// For tests that want to read what's in a SerializedVar.
class PPAPI_PROXY_EXPORT SerializedVarTestReader : public SerializedVar {
explicit SerializedVarTestReader(const SerializedVar& var);
PP_Var GetVar() const { return inner_->GetVar(); }
} // namespace proxy
} // namespace ppapi