ipc_message_utils.h

// Copyright (c) 2010 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 IPC_IPC_MESSAGE_UTILS_H_
#define IPC_IPC_MESSAGE_UTILS_H_
#pragma once

#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <set>

#include "base/format_macros.h"
#include "base/string16.h"
#include "base/string_util.h"
#include "base/tuple.h"
#include "ipc/ipc_param_traits.h"
#include "ipc/ipc_sync_message.h"

#if defined(COMPILER_GCC)
// GCC "helpfully" tries to inline template methods in release mode. Except we
// want the majority of the template junk being expanded once in the
// implementation file (and only provide the definitions in
// ipc_message_utils_impl.h in those files) and exported, instead of expanded
// at every call site. Special note: GCC happily accepts the attribute before
// the method declaration, but only acts on it if it is after.
#if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100) >= 40500
// Starting in gcc 4.5, the noinline no longer implies the concept covered by
// the introduced noclone attribute, which will create specialized versions of
// functions/methods when certain types are constant.
// www.gnu.org/software/gcc/gcc-4.5/changes.html
#define IPC_MSG_NOINLINE  __attribute__((noinline, noclone));
#else
#define IPC_MSG_NOINLINE  __attribute__((noinline));
#endif
#elif defined(COMPILER_MSVC)
// MSVC++ doesn't do this.
#define IPC_MSG_NOINLINE
#else
#error "Please add the noinline property for your new compiler here."
#endif

// Used by IPC_BEGIN_MESSAGES so that each message class starts from a unique
// base.  Messages have unique IDs across channels in order for the IPC logging
// code to figure out the message class from its ID.
enum IPCMessageStart {
  // By using a start value of 0 for automation messages, we keep backward
  // compatibility with old builds.
  AutomationMsgStart = 0,
  ViewMsgStart,
  ViewHostMsgStart,
  PluginProcessMsgStart,
  PluginProcessHostMsgStart,
  PluginMsgStart,
  PluginHostMsgStart,
  ProfileImportProcessMsgStart,
  ProfileImportProcessHostMsgStart,
  NPObjectMsgStart,
  TestMsgStart,
  DevToolsAgentMsgStart,
  DevToolsClientMsgStart,
  WorkerProcessMsgStart,
  WorkerProcessHostMsgStart,
  WorkerMsgStart,
  WorkerHostMsgStart,
  NaClProcessMsgStart,
  GpuCommandBufferMsgStart,
  UtilityMsgStart,
  UtilityHostMsgStart,
  GpuMsgStart,
  GpuHostMsgStart,
  GpuChannelMsgStart,
  GpuVideoDecoderHostMsgStart,
  GpuVideoDecoderMsgStart,
  ServiceMsgStart,
  ServiceHostMsgStart,
  PpapiMsgStart,
  PpapiHostMsgStart,
  // NOTE: When you add a new message class, also update
  // IPCStatusView::IPCStatusView to ensure logging works.
  LastMsgIndex
};

class DictionaryValue;
class FilePath;
class ListValue;
class NullableString16;

namespace base {
class Time;
class TimeDelta;
struct FileDescriptor;
}

namespace IPC {

struct ChannelHandle;

//-----------------------------------------------------------------------------
// An iterator class for reading the fields contained within a Message.

class MessageIterator {
 public:
  explicit MessageIterator(const Message& m) : msg_(m), iter_(NULL) {
  }
  int NextInt() const {
    int val = -1;
    if (!msg_.ReadInt(&iter_, &val))
      NOTREACHED();
    return val;
  }
  const std::string NextString() const {
    std::string val;
    if (!msg_.ReadString(&iter_, &val))
      NOTREACHED();
    return val;
  }
  const std::wstring NextWString() const {
    std::wstring val;
    if (!msg_.ReadWString(&iter_, &val))
      NOTREACHED();
    return val;
  }
  void NextData(const char** data, int* length) const {
    if (!msg_.ReadData(&iter_, data, length)) {
      NOTREACHED();
    }
  }
 private:
  const Message& msg_;
  mutable void* iter_;
};

//-----------------------------------------------------------------------------
// ParamTraits specializations, etc.

template <class P>
static inline void WriteParam(Message* m, const P& p) {
  typedef typename SimilarTypeTraits<P>::Type Type;
  ParamTraits<Type>::Write(m, static_cast<const Type& >(p));
}

template <class P>
static inline bool WARN_UNUSED_RESULT ReadParam(const Message* m, void** iter,
                                                P* p) {
  typedef typename SimilarTypeTraits<P>::Type Type;
  return ParamTraits<Type>::Read(m, iter, reinterpret_cast<Type* >(p));
}

template <class P>
static inline void LogParam(const P& p, std::string* l) {
  typedef typename SimilarTypeTraits<P>::Type Type;
  ParamTraits<Type>::Log(static_cast<const Type& >(p), l);
}

template <>
struct ParamTraits<bool> {
  typedef bool param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteBool(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadBool(iter, r);
  }
  static void Log(const param_type& p, std::string* l) {
    l->append(p ? "true" : "false");
  }
};

template <>
struct ParamTraits<int> {
  typedef int param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteInt(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadInt(iter, r);
  }
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<unsigned int> {
  typedef unsigned int param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteInt(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadInt(iter, reinterpret_cast<int*>(r));
  }
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<long> {
  typedef long param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteLong(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadLong(iter, r);
  }
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<unsigned long> {
  typedef unsigned long param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteLong(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadLong(iter, reinterpret_cast<long*>(r));
  }
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<long long> {
  typedef long long param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteInt64(static_cast<int64>(p));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadInt64(iter, reinterpret_cast<int64*>(r));
  }
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<unsigned long long> {
  typedef unsigned long long param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteInt64(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadInt64(iter, reinterpret_cast<int64*>(r));
  }
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<unsigned short> {
  typedef unsigned short param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};

// Note that the IPC layer doesn't sanitize NaNs and +/- INF values.  Clients
// should be sure to check the sanity of these values after receiving them over
// IPC.
template <>
struct ParamTraits<float> {
  typedef float param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteData(reinterpret_cast<const char*>(&p), sizeof(param_type));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    const char *data;
    int data_size;
    if (!m->ReadData(iter, &data, &data_size) ||
        data_size != sizeof(param_type)) {
      NOTREACHED();
      return false;
    }
    memcpy(r, data, sizeof(param_type));
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
    l->append(StringPrintf("%e", p));
  }
};

template <>
struct ParamTraits<double> {
  typedef double param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteData(reinterpret_cast<const char*>(&p), sizeof(param_type));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    const char *data;
    int data_size;
    if (!m->ReadData(iter, &data, &data_size) ||
        data_size != sizeof(param_type)) {
      NOTREACHED();
      return false;
    }
    memcpy(r, data, sizeof(param_type));
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
    l->append(StringPrintf("%e", p));
  }
};

template <>
struct ParamTraits<base::Time> {
  typedef base::Time param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<base::TimeDelta> {
  typedef base::TimeDelta param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};

#if defined(OS_WIN)
template <>
struct ParamTraits<LOGFONT> {
  typedef LOGFONT param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteData(reinterpret_cast<const char*>(&p), sizeof(LOGFONT));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    const char *data;
    int data_size = 0;
    bool result = m->ReadData(iter, &data, &data_size);
    if (result && data_size == sizeof(LOGFONT)) {
      memcpy(r, data, sizeof(LOGFONT));
    } else {
      result = false;
      NOTREACHED();
    }

    return result;
  }
  static void Log(const param_type& p, std::string* l) {
    l->append(StringPrintf("<LOGFONT>"));
  }
};

template <>
struct ParamTraits<MSG> {
  typedef MSG param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteData(reinterpret_cast<const char*>(&p), sizeof(MSG));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    const char *data;
    int data_size = 0;
    bool result = m->ReadData(iter, &data, &data_size);
    if (result && data_size == sizeof(MSG)) {
      memcpy(r, data, sizeof(MSG));
    } else {
      result = false;
      NOTREACHED();
    }

    return result;
  }
  static void Log(const param_type& p, std::string* l) {
    l->append("<MSG>");
  }
};
#endif  // defined(OS_WIN)

template <>
struct ParamTraits<DictionaryValue> {
  typedef DictionaryValue param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<ListValue> {
  typedef ListValue param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};

template <>
struct ParamTraits<std::string> {
  typedef std::string param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteString(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadString(iter, r);
  }
  static void Log(const param_type& p, std::string* l) {
    l->append(p);
  }
};

template<typename CharType>
static void LogBytes(const std::vector<CharType>& data, std::string* out) {
#if defined(OS_WIN)
  // Windows has a GUI for logging, which can handle arbitrary binary data.
  for (size_t i = 0; i < data.size(); ++i)
    out->push_back(data[i]);
#else
  // On POSIX, we log to stdout, which we assume can display ASCII.
  static const size_t kMaxBytesToLog = 100;
  for (size_t i = 0; i < std::min(data.size(), kMaxBytesToLog); ++i) {
    if (isprint(data[i]))
      out->push_back(data[i]);
    else
      out->append(StringPrintf("[%02X]", static_cast<unsigned char>(data[i])));
  }
  if (data.size() > kMaxBytesToLog) {
    out->append(
        StringPrintf(" and %u more bytes",
                     static_cast<unsigned>(data.size() - kMaxBytesToLog)));
  }
#endif
}

template <>
struct ParamTraits<std::vector<unsigned char> > {
  typedef std::vector<unsigned char> param_type;
  static void Write(Message* m, const param_type& p) {
    if (p.size() == 0) {
      m->WriteData(NULL, 0);
    } else {
      m->WriteData(reinterpret_cast<const char*>(&p.front()),
                   static_cast<int>(p.size()));
    }
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    const char *data;
    int data_size = 0;
    if (!m->ReadData(iter, &data, &data_size) || data_size < 0)
      return false;
    r->resize(data_size);
    if (data_size)
      memcpy(&r->front(), data, data_size);
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
    LogBytes(p, l);
  }
};

template <>
struct ParamTraits<std::vector<char> > {
  typedef std::vector<char> param_type;
  static void Write(Message* m, const param_type& p) {
    if (p.size() == 0) {
      m->WriteData(NULL, 0);
    } else {
      m->WriteData(&p.front(), static_cast<int>(p.size()));
    }
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    const char *data;
    int data_size = 0;
    if (!m->ReadData(iter, &data, &data_size) || data_size < 0)
      return false;
    r->resize(data_size);
    if (data_size)
      memcpy(&r->front(), data, data_size);
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
    LogBytes(p, l);
  }
};

template <class P>
struct ParamTraits<std::vector<P> > {
  typedef std::vector<P> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, static_cast<int>(p.size()));
    for (size_t i = 0; i < p.size(); i++)
      WriteParam(m, p[i]);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    int size;
    // ReadLength() checks for < 0 itself.
    if (!m->ReadLength(iter, &size))
      return false;
    // Resizing beforehand is not safe, see BUG 1006367 for details.
    if (INT_MAX / sizeof(P) <= static_cast<size_t>(size))
      return false;
    r->resize(size);
    for (int i = 0; i < size; i++) {
      if (!ReadParam(m, iter, &(*r)[i]))
        return false;
    }
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
    for (size_t i = 0; i < p.size(); ++i) {
      if (i != 0)
        l->append(" ");
      LogParam((p[i]), l);
    }
  }
};

template <class P>
struct ParamTraits<std::set<P> > {
  typedef std::set<P> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, static_cast<int>(p.size()));
    typename param_type::const_iterator iter;
    for (iter = p.begin(); iter != p.end(); ++iter)
      WriteParam(m, *iter);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    int size;
    if (!m->ReadLength(iter, &size))
      return false;
    for (int i = 0; i < size; ++i) {
      P item;
      if (!ReadParam(m, iter, &item))
        return false;
      r->insert(item);
    }
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
    l->append("<std::set>");
  }
};


template <class K, class V>
struct ParamTraits<std::map<K, V> > {
  typedef std::map<K, V> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, static_cast<int>(p.size()));
    typename param_type::const_iterator iter;
    for (iter = p.begin(); iter != p.end(); ++iter) {
      WriteParam(m, iter->first);
      WriteParam(m, iter->second);
    }
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    int size;
    if (!ReadParam(m, iter, &size) || size < 0)
      return false;
    for (int i = 0; i < size; ++i) {
      K k;
      if (!ReadParam(m, iter, &k))
        return false;
      V& value = (*r)[k];
      if (!ReadParam(m, iter, &value))
        return false;
    }
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
    l->append("<std::map>");
  }
};


template <>
struct ParamTraits<std::wstring> {
  typedef std::wstring param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteWString(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadWString(iter, r);
  }
  static void Log(const param_type& p, std::string* l);
};

template <class A, class B>
struct ParamTraits<std::pair<A, B> > {
  typedef std::pair<A, B> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, p.first);
    WriteParam(m, p.second);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return ReadParam(m, iter, &r->first) && ReadParam(m, iter, &r->second);
  }
  static void Log(const param_type& p, std::string* l) {
    l->append("(");
    LogParam(p.first, l);
    l->append(", ");
    LogParam(p.second, l);
    l->append(")");
  }
};

template <>
struct ParamTraits<NullableString16> {
  typedef NullableString16 param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};

// If WCHAR_T_IS_UTF16 is defined, then string16 is a std::wstring so we don't
// need this trait.
#if !defined(WCHAR_T_IS_UTF16)
template <>
struct ParamTraits<string16> {
  typedef string16 param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteString16(p);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return m->ReadString16(iter, r);
  }
  static void Log(const param_type& p, std::string* l);
};
#endif

// and, a few more useful types...
#if defined(OS_WIN)
template <>
struct ParamTraits<HANDLE> {
  typedef HANDLE param_type;
  static void Write(Message* m, const param_type& p) {
    // Note that HWNDs/HANDLE/HCURSOR/HACCEL etc are always 32 bits, even on 64
    // bit systems.
    m->WriteUInt32(reinterpret_cast<uint32>(p));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    DCHECK_EQ(sizeof(param_type), sizeof(uint32));
    return m->ReadUInt32(iter, reinterpret_cast<uint32*>(r));
  }
  static void Log(const param_type& p, std::string* l) {
    l->append(StringPrintf("0x%X", p));
  }
};

template <>
struct ParamTraits<HCURSOR> {
  typedef HCURSOR param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteUInt32(reinterpret_cast<uint32>(p));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    DCHECK_EQ(sizeof(param_type), sizeof(uint32));
    return m->ReadUInt32(iter, reinterpret_cast<uint32*>(r));
  }
  static void Log(const param_type& p, std::string* l) {
    l->append(StringPrintf("0x%X", p));
  }
};

template <>
struct ParamTraits<HACCEL> {
  typedef HACCEL param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteUInt32(reinterpret_cast<uint32>(p));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    DCHECK_EQ(sizeof(param_type), sizeof(uint32));
    return m->ReadUInt32(iter, reinterpret_cast<uint32*>(r));
  }
};

template <>
struct ParamTraits<POINT> {
  typedef POINT param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteInt(p.x);
    m->WriteInt(p.y);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    int x, y;
    if (!m->ReadInt(iter, &x) || !m->ReadInt(iter, &y))
      return false;
    r->x = x;
    r->y = y;
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
    l->append(StringPrintf("(%d, %d)", p.x, p.y));
  }
};
#endif  // defined(OS_WIN)

template <>
struct ParamTraits<FilePath> {
  typedef FilePath param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};

#if defined(OS_POSIX)
// FileDescriptors may be serialised over IPC channels on POSIX. On the
// receiving side, the FileDescriptor is a valid duplicate of the file
// descriptor which was transmitted: *it is not just a copy of the integer like
// HANDLEs on Windows*. The only exception is if the file descriptor is < 0. In
// this case, the receiving end will see a value of -1. *Zero is a valid file
// descriptor*.
//
// The received file descriptor will have the |auto_close| flag set to true. The
// code which handles the message is responsible for taking ownership of it.
// File descriptors are OS resources and must be closed when no longer needed.
//
// When sending a file descriptor, the file descriptor must be valid at the time
// of transmission. Since transmission is not synchronous, one should consider
// dup()ing any file descriptors to be transmitted and setting the |auto_close|
// flag, which causes the file descriptor to be closed after writing.
template<>
struct ParamTraits<base::FileDescriptor> {
  typedef base::FileDescriptor param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};
#endif  // defined(OS_POSIX)

// A ChannelHandle is basically a platform-inspecific wrapper around the
// fact that IPC endpoints are handled specially on POSIX.  See above comments
// on FileDescriptor for more background.
template<>
struct ParamTraits<IPC::ChannelHandle> {
  typedef ChannelHandle param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l);
};

#if defined(OS_WIN)
template <>
struct ParamTraits<XFORM> {
  typedef XFORM param_type;
  static void Write(Message* m, const param_type& p) {
    m->WriteData(reinterpret_cast<const char*>(&p), sizeof(XFORM));
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    const char *data;
    int data_size = 0;
    bool result = m->ReadData(iter, &data, &data_size);
    if (result && data_size == sizeof(XFORM)) {
      memcpy(r, data, sizeof(XFORM));
    } else {
      result = false;
      NOTREACHED();
    }

    return result;
  }
  static void Log(const param_type& p, std::string* l) {
    l->append("<XFORM>");
  }
};
#endif  // defined(OS_WIN)

struct LogData {
  LogData();
  ~LogData();

  std::string channel;
  int32 routing_id;
  uint32 type;  // "User-defined" message type, from ipc_message.h.
  std::string flags;
  int64 sent;  // Time that the message was sent (i.e. at Send()).
  int64 receive;  // Time before it was dispatched (i.e. before calling
                  // OnMessageReceived).
  int64 dispatch;  // Time after it was dispatched (i.e. after calling
                   // OnMessageReceived).
  std::string message_name;
  std::string params;
};

template <>
struct ParamTraits<LogData> {
  typedef LogData param_type;
  static void Write(Message* m, const param_type& p);
  static bool Read(const Message* m, void** iter, param_type* r);
  static void Log(const param_type& p, std::string* l) {
    // Doesn't make sense to implement this!
  }
};

template <>
struct ParamTraits<Message> {
  static void Write(Message* m, const Message& p) {
    m->WriteInt(p.size());
    m->WriteData(reinterpret_cast<const char*>(p.data()), p.size());
  }
  static bool Read(const Message* m, void** iter, Message* r) {
    int size;
    if (!m->ReadInt(iter, &size))
      return false;
    const char* data;
    if (!m->ReadData(iter, &data, &size))
      return false;
    *r = Message(data, size);
    return true;
  }
  static void Log(const Message& p, std::string* l) {
    l->append("<IPC::Message>");
  }
};

template <>
struct ParamTraits<Tuple0> {
  typedef Tuple0 param_type;
  static void Write(Message* m, const param_type& p) {
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return true;
  }
  static void Log(const param_type& p, std::string* l) {
  }
};

template <class A>
struct ParamTraits< Tuple1<A> > {
  typedef Tuple1<A> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, p.a);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return ReadParam(m, iter, &r->a);
  }
  static void Log(const param_type& p, std::string* l) {
    LogParam(p.a, l);
  }
};

template <class A, class B>
struct ParamTraits< Tuple2<A, B> > {
  typedef Tuple2<A, B> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, p.a);
    WriteParam(m, p.b);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return (ReadParam(m, iter, &r->a) &&
            ReadParam(m, iter, &r->b));
  }
  static void Log(const param_type& p, std::string* l) {
    LogParam(p.a, l);
    l->append(", ");
    LogParam(p.b, l);
  }
};

template <class A, class B, class C>
struct ParamTraits< Tuple3<A, B, C> > {
  typedef Tuple3<A, B, C> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, p.a);
    WriteParam(m, p.b);
    WriteParam(m, p.c);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return (ReadParam(m, iter, &r->a) &&
            ReadParam(m, iter, &r->b) &&
            ReadParam(m, iter, &r->c));
  }
  static void Log(const param_type& p, std::string* l) {
    LogParam(p.a, l);
    l->append(", ");
    LogParam(p.b, l);
    l->append(", ");
    LogParam(p.c, l);
  }
};

template <class A, class B, class C, class D>
struct ParamTraits< Tuple4<A, B, C, D> > {
  typedef Tuple4<A, B, C, D> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, p.a);
    WriteParam(m, p.b);
    WriteParam(m, p.c);
    WriteParam(m, p.d);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return (ReadParam(m, iter, &r->a) &&
            ReadParam(m, iter, &r->b) &&
            ReadParam(m, iter, &r->c) &&
            ReadParam(m, iter, &r->d));
  }
  static void Log(const param_type& p, std::string* l) {
    LogParam(p.a, l);
    l->append(", ");
    LogParam(p.b, l);
    l->append(", ");
    LogParam(p.c, l);
    l->append(", ");
    LogParam(p.d, l);
  }
};

template <class A, class B, class C, class D, class E>
struct ParamTraits< Tuple5<A, B, C, D, E> > {
  typedef Tuple5<A, B, C, D, E> param_type;
  static void Write(Message* m, const param_type& p) {
    WriteParam(m, p.a);
    WriteParam(m, p.b);
    WriteParam(m, p.c);
    WriteParam(m, p.d);
    WriteParam(m, p.e);
  }
  static bool Read(const Message* m, void** iter, param_type* r) {
    return (ReadParam(m, iter, &r->a) &&
            ReadParam(m, iter, &r->b) &&
            ReadParam(m, iter, &r->c) &&
            ReadParam(m, iter, &r->d) &&
            ReadParam(m, iter, &r->e));
  }
  static void Log(const param_type& p, std::string* l) {
    LogParam(p.a, l);
    l->append(", ");
    LogParam(p.b, l);
    l->append(", ");
    LogParam(p.c, l);
    l->append(", ");
    LogParam(p.d, l);
    l->append(", ");
    LogParam(p.e, l);
  }
};

//-----------------------------------------------------------------------------
// Generic message subclasses

// Used for asynchronous messages.
template <class ParamType>
class MessageWithTuple : public Message {
 public:
  typedef ParamType Param;
  typedef typename TupleTypes<ParamType>::ParamTuple RefParam;

  // The constructor and the Read() method's templated implementations are in
  // ipc_message_utils_impl.h. The subclass constructor and Log() methods call
  // the templated versions of these and make sure there are instantiations in
  // those translation units.
  MessageWithTuple(int32 routing_id, uint32 type, const RefParam& p);

  static bool Read(const Message* msg, Param* p) IPC_MSG_NOINLINE;

  // Generic dispatcher.  Should cover most cases.
  template<class T, class Method>
  static bool Dispatch(const Message* msg, T* obj, Method func) {
    Param p;
    if (Read(msg, &p)) {
      DispatchToMethod(obj, func, p);
      return true;
    }
    return false;
  }

  // The following dispatchers exist for the case where the callback function
  // needs the message as well.  They assume that "Param" is a type of Tuple
  // (except the one arg case, as there is no Tuple1).
  template<class T, typename TA>
  static bool Dispatch(const Message* msg, T* obj,
                       void (T::*func)(const Message&, TA)) {
    Param p;
    if (Read(msg, &p)) {
      (obj->*func)(*msg, p.a);
      return true;
    }
    return false;
  }

  template<class T, typename TA, typename TB>
  static bool Dispatch(const Message* msg, T* obj,
                       void (T::*func)(const Message&, TA, TB)) {
    Param p;
    if (Read(msg, &p)) {
      (obj->*func)(*msg, p.a, p.b);
      return true;
    }
    return false;
  }

  template<class T, typename TA, typename TB, typename TC>
  static bool Dispatch(const Message* msg, T* obj,
                       void (T::*func)(const Message&, TA, TB, TC)) {
    Param p;
    if (Read(msg, &p)) {
      (obj->*func)(*msg, p.a, p.b, p.c);
      return true;
    }
    return false;
  }

  template<class T, typename TA, typename TB, typename TC, typename TD>
  static bool Dispatch(const Message* msg, T* obj,
                       void (T::*func)(const Message&, TA, TB, TC, TD)) {
    Param p;
    if (Read(msg, &p)) {
      (obj->*func)(*msg, p.a, p.b, p.c, p.d);
      return true;
    }
    return false;
  }

  template<class T, typename TA, typename TB, typename TC, typename TD,
           typename TE>
  static bool Dispatch(const Message* msg, T* obj,
                       void (T::*func)(const Message&, TA, TB, TC, TD, TE)) {
    Param p;
    if (Read(msg, &p)) {
      (obj->*func)(*msg, p.a, p.b, p.c, p.d, p.e);
      return true;
    }
    return false;
  }

  // Functions used to do manual unpacking.  Only used by the automation code,
  // these should go away once that code uses SyncChannel.
  template<typename TA, typename TB>
  static bool Read(const IPC::Message* msg, TA* a, TB* b) {
    ParamType params;
    if (!Read(msg, &params))
      return false;
    *a = params.a;
    *b = params.b;
    return true;
  }

  template<typename TA, typename TB, typename TC>
  static bool Read(const IPC::Message* msg, TA* a, TB* b, TC* c) {
    ParamType params;
    if (!Read(msg, &params))
      return false;
    *a = params.a;
    *b = params.b;
    *c = params.c;
    return true;
  }

  template<typename TA, typename TB, typename TC, typename TD>
  static bool Read(const IPC::Message* msg, TA* a, TB* b, TC* c, TD* d) {
    ParamType params;
    if (!Read(msg, &params))
      return false;
    *a = params.a;
    *b = params.b;
    *c = params.c;
    *d = params.d;
    return true;
  }

  template<typename TA, typename TB, typename TC, typename TD, typename TE>
  static bool Read(const IPC::Message* msg, TA* a, TB* b, TC* c, TD* d, TE* e) {
    ParamType params;
    if (!Read(msg, &params))
      return false;
    *a = params.a;
    *b = params.b;
    *c = params.c;
    *d = params.d;
    *e = params.e;
    return true;
  }
};

// defined in ipc_logging.cc
void GenerateLogData(const std::string& channel, const Message& message,
                     LogData* data);


#if defined(IPC_MESSAGE_LOG_ENABLED)
inline void AddOutputParamsToLog(const Message* msg, std::string* l) {
  const std::string& output_params = msg->output_params();
  if (!l->empty() && !output_params.empty())
    l->append(", ");

  l->append(output_params);
}

template <class ReplyParamType>
inline void LogReplyParamsToMessage(const ReplyParamType& reply_params,
                                    const Message* msg) {
  if (msg->received_time() != 0) {
    std::string output_params;
    LogParam(reply_params, &output_params);
    msg->set_output_params(output_params);
  }
}

inline void ConnectMessageAndReply(const Message* msg, Message* reply) {
  if (msg->sent_time()) {
    // Don't log the sync message after dispatch, as we don't have the
    // output parameters at that point.  Instead, save its data and log it
    // with the outgoing reply message when it's sent.
    LogData* data = new LogData;
    GenerateLogData("", *msg, data);
    msg->set_dont_log();
    reply->set_sync_log_data(data);
  }
}
#else
inline void AddOutputParamsToLog(const Message* msg, std::string* l) {}

template <class ReplyParamType>
inline void LogReplyParamsToMessage(const ReplyParamType& reply_params,
                                    const Message* msg) {}

inline void ConnectMessageAndReply(const Message* msg, Message* reply) {}
#endif

// This class assumes that its template argument is a RefTuple (a Tuple with
// reference elements). This would go into ipc_message_utils_impl.h, but it is
// also used by chrome_frame.
template <class RefTuple>
class ParamDeserializer : public MessageReplyDeserializer {
 public:
  explicit ParamDeserializer(const RefTuple& out) : out_(out) { }

  bool SerializeOutputParameters(const IPC::Message& msg, void* iter) {
    return ReadParam(&msg, &iter, &out_);
  }

  RefTuple out_;
};

// Used for synchronous messages.
template <class SendParamType, class ReplyParamType>
class MessageWithReply : public SyncMessage {
 public:
  typedef SendParamType SendParam;
  typedef typename TupleTypes<SendParam>::ParamTuple RefSendParam;
  typedef ReplyParamType ReplyParam;

  MessageWithReply(int32 routing_id, uint32 type,
                   const RefSendParam& send, const ReplyParam& reply);
  static bool ReadSendParam(const Message* msg, SendParam* p) IPC_MSG_NOINLINE;
  static bool ReadReplyParam(
      const Message* msg,
      typename TupleTypes<ReplyParam>::ValueTuple* p) IPC_MSG_NOINLINE;

  template<class T, class Method>
  static bool Dispatch(const Message* msg, T* obj, Method func) {
    SendParam send_params;
    Message* reply = GenerateReply(msg);
    bool error;
    if (ReadSendParam(msg, &send_params)) {
      typename TupleTypes<ReplyParam>::ValueTuple reply_params;
      DispatchToMethod(obj, func, send_params, &reply_params);
      WriteParam(reply, reply_params);
      error = false;
      LogReplyParamsToMessage(reply_params, msg);
    } else {
      NOTREACHED() << "Error deserializing message " << msg->type();
      reply->set_reply_error();
      error = true;
    }

    obj->Send(reply);
    return !error;
  }

  template<class T, class Method>
  static bool DispatchDelayReply(const Message* msg, T* obj, Method func) {
    SendParam send_params;
    Message* reply = GenerateReply(msg);
    bool error;
    if (ReadSendParam(msg, &send_params)) {
      Tuple1<Message&> t = MakeRefTuple(*reply);
      ConnectMessageAndReply(msg, reply);
      DispatchToMethod(obj, func, send_params, &t);
      error = false;
    } else {
      NOTREACHED() << "Error deserializing message " << msg->type();
      reply->set_reply_error();
      obj->Send(reply);
      error = true;
    }
    return !error;
  }

  template<typename TA>
  static void WriteReplyParams(Message* reply, TA a) {
    ReplyParam p(a);
    WriteParam(reply, p);
  }

  template<typename TA, typename TB>
  static void WriteReplyParams(Message* reply, TA a, TB b) {
    ReplyParam p(a, b);
    WriteParam(reply, p);
  }

  template<typename TA, typename TB, typename TC>
  static void WriteReplyParams(Message* reply, TA a, TB b, TC c) {
    ReplyParam p(a, b, c);
    WriteParam(reply, p);
  }

  template<typename TA, typename TB, typename TC, typename TD>
  static void WriteReplyParams(Message* reply, TA a, TB b, TC c, TD d) {
    ReplyParam p(a, b, c, d);
    WriteParam(reply, p);
  }

  template<typename TA, typename TB, typename TC, typename TD, typename TE>
  static void WriteReplyParams(Message* reply, TA a, TB b, TC c, TD d, TE e) {
    ReplyParam p(a, b, c, d, e);
    WriteParam(reply, p);
  }
};

//-----------------------------------------------------------------------------

}  // namespace IPC

#endif  // IPC_IPC_MESSAGE_UTILS_H_