tor-browser

ipc_message_utils.h (37619B)

---

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2006-2008 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 CHROME_COMMON_IPC_MESSAGE_UTILS_H_
#define CHROME_COMMON_IPC_MESSAGE_UTILS_H_

#include <cstdint>
#include <iterator>
#include <map>
#include <string>
#include <type_traits>
#include <utility>
#include <variant>
#include "ErrorList.h"
#include "base/logging.h"
#include "base/pickle.h"
#include "chrome/common/ipc_message.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/ipc/SharedMemoryMapping.h"

#if defined(XP_WIN)
#  include <windows.h>
#endif

template <typename T>
class RefPtr;
template <typename T>
class nsCOMPtr;

namespace mozilla::ipc {
class IProtocol;
namespace shared_memory {
class Cursor;
}

// Implemented in ProtocolUtils.cpp
MOZ_NEVER_INLINE void PickleFatalError(const char* aMsg, IProtocol* aActor);
}  // namespace mozilla::ipc

namespace IPC {

/**
* This constant determines the threshold size (in bytes) for deciding whether
* shared memory should be used during serialization/deserialization handled
* by the MessageBufferWriter class.
*
* NOTE: Even above this threshold, if MessageBufferWriter fails to allocate a
* shared memory region, it may still fall-back to sending the message inline.
*/
constexpr uint32_t kMessageBufferShmemThreshold = 64 * 1024;  // 64 KB

/**
* Context used to serialize into an IPC::Message. Provides relevant context
* used when serializing.
*/
class MOZ_STACK_CLASS MessageWriter final {
public:
 explicit MessageWriter(Message& message,
                        mozilla::ipc::IProtocol* actor = nullptr)
     : message_(message), actor_(actor) {}

 MessageWriter(const MessageWriter&) = delete;
 MessageWriter& operator=(const MessageWriter&) = delete;

 mozilla::ipc::IProtocol* GetActor() const { return actor_; }

#define FORWARD_WRITE(name, type) \
 bool Write##name(const type& result) { return message_.Write##name(result); }

 FORWARD_WRITE(Bool, bool)
 FORWARD_WRITE(Int16, int16_t)
 FORWARD_WRITE(UInt16, uint16_t)
 FORWARD_WRITE(Int, int)
 FORWARD_WRITE(Long, long)
 FORWARD_WRITE(ULong, unsigned long)
 FORWARD_WRITE(Int32, int32_t)
 FORWARD_WRITE(UInt32, uint32_t)
 FORWARD_WRITE(Int64, int64_t)
 FORWARD_WRITE(UInt64, uint64_t)
 FORWARD_WRITE(Double, double)
 FORWARD_WRITE(IntPtr, intptr_t)
 FORWARD_WRITE(UnsignedChar, unsigned char)
 FORWARD_WRITE(String, std::string)
 FORWARD_WRITE(WString, std::wstring)

#undef FORWARD_WRITE

 template <class T>
 bool WriteScalar(const T& result) {
   return message_.WriteScalar(result);
 }

 bool WriteData(const char* data, uint32_t length) {
   return message_.WriteData(data, length);
 }

 bool WriteBytes(const void* data, uint32_t data_len) {
   return message_.WriteBytes(data, data_len);
 }

 bool WriteBytesZeroCopy(void* data, uint32_t data_len, uint32_t capacity) {
   return message_.WriteBytesZeroCopy(data, data_len, capacity);
 }

 bool WriteSentinel(uint32_t sentinel) {
   return message_.WriteSentinel(sentinel);
 }

 bool WriteFileHandle(mozilla::UniqueFileHandle handle) {
   return message_.WriteFileHandle(std::move(handle));
 }

 void WritePort(mozilla::ipc::ScopedPort port) {
   message_.WritePort(std::move(port));
 }

#if defined(XP_DARWIN)
 bool WriteMachSendRight(mozilla::UniqueMachSendRight port) {
   return message_.WriteMachSendRight(std::move(port));
 }

 bool WriteMachReceiveRight(mozilla::UniqueMachReceiveRight port) {
   return message_.WriteMachReceiveRight(std::move(port));
 }
#endif

 void FatalError(const char* aErrorMsg) const {
   mozilla::ipc::PickleFatalError(aErrorMsg, actor_);
 }

 void NoteLargeBufferShmemFailure(uint32_t aLargeBufferSize) {
   message_.NoteLargeBufferShmemFailure(aLargeBufferSize);
 }

private:
 Message& message_;
 mozilla::ipc::IProtocol* actor_;
};

/**
* Context used to read data from an IPC::Message. Provides relevant context
* used when deserializing and tracks iteration.
*/
class MOZ_STACK_CLASS MessageReader final {
public:
 explicit MessageReader(const Message& message,
                        mozilla::ipc::IProtocol* actor = nullptr)
     : message_(message), iter_(message), actor_(actor) {}

 MessageReader(const MessageReader&) = delete;
 MessageReader& operator=(const MessageReader&) = delete;

 mozilla::ipc::IProtocol* GetActor() const { return actor_; }

#define FORWARD_READ(name, type)                \
 [[nodiscard]] bool Read##name(type* result) { \
   return message_.Read##name(&iter_, result); \
 }

 FORWARD_READ(Bool, bool)
 FORWARD_READ(Int16, int16_t)
 FORWARD_READ(UInt16, uint16_t)
 FORWARD_READ(Short, short)
 FORWARD_READ(Int, int)
 FORWARD_READ(Long, long)
 FORWARD_READ(ULong, unsigned long)
 FORWARD_READ(Int32, int32_t)
 FORWARD_READ(UInt32, uint32_t)
 FORWARD_READ(Int64, int64_t)
 FORWARD_READ(UInt64, uint64_t)
 FORWARD_READ(Double, double)
 FORWARD_READ(IntPtr, intptr_t)
 FORWARD_READ(UnsignedChar, unsigned char)
 FORWARD_READ(String, std::string)
 FORWARD_READ(WString, std::wstring)

 // Special version of ReadInt() which rejects negative values
 FORWARD_READ(Length, int);

#undef FORWARD_READ

 template <class T>
 [[nodiscard]] bool ReadScalar(T* const result) {
   return message_.ReadScalar(&iter_, result);
 }

 [[nodiscard]] bool ReadBytesInto(void* data, uint32_t length) {
   return message_.ReadBytesInto(&iter_, data, length);
 }

 [[nodiscard]] bool IgnoreBytes(uint32_t length) {
   return message_.IgnoreBytes(&iter_, length);
 }

 [[nodiscard]] bool ReadSentinel(uint32_t sentinel) {
   return message_.ReadSentinel(&iter_, sentinel);
 }

 bool IgnoreSentinel() { return message_.IgnoreSentinel(&iter_); }

 bool HasBytesAvailable(uint32_t len) {
   return message_.HasBytesAvailable(&iter_, len);
 }

 void EndRead() { message_.EndRead(iter_, message_.type()); }

 [[nodiscard]] bool ConsumeFileHandle(mozilla::UniqueFileHandle* handle) {
   return message_.ConsumeFileHandle(&iter_, handle);
 }

 [[nodiscard]] bool ConsumePort(mozilla::ipc::ScopedPort* port) {
   return message_.ConsumePort(&iter_, port);
 }

#if defined(XP_DARWIN)
 [[nodiscard]] bool ConsumeMachSendRight(mozilla::UniqueMachSendRight* port) {
   return message_.ConsumeMachSendRight(&iter_, port);
 }

 [[nodiscard]] bool ConsumeMachReceiveRight(
     mozilla::UniqueMachReceiveRight* port) {
   return message_.ConsumeMachReceiveRight(&iter_, port);
 }
#endif

 void FatalError(const char* aErrorMsg) const {
   mozilla::ipc::PickleFatalError(aErrorMsg, actor_);
 }

private:
 const Message& message_;
 PickleIterator iter_;
 mozilla::ipc::IProtocol* actor_;
};

namespace detail {

// Helper for checking `T::kHasDeprecatedReadParamPrivateConstructor` using a
// fallback when the member isn't defined.
template <typename T>
inline constexpr auto HasDeprecatedReadParamPrivateConstructor(int)
   -> decltype(T::kHasDeprecatedReadParamPrivateConstructor) {
 return T::kHasDeprecatedReadParamPrivateConstructor;
}

template <typename T>
inline constexpr bool HasDeprecatedReadParamPrivateConstructor(...) {
 return false;
}

}  // namespace detail

/**
* Result type returned from some `ParamTraits<T>::Read` implementations, and
* from `IPC::ReadParam<T>(MessageReader*)`. Either contains the value or
* indicates a failure to deserialize.
*
* This type can be thought of as a variant on `Maybe<T>`, except that it
* unconditionally constructs the underlying value if it is default
* constructible. This helps keep code size down, especially when calling
* outparameter-based ReadParam implementations (bug 1815177).
*/
template <typename T,
         bool = std::is_default_constructible_v<T> ||
                detail::HasDeprecatedReadParamPrivateConstructor<T>(0)>
class ReadResult {
public:
 ReadResult() = default;

 template <typename U, std::enable_if_t<std::is_convertible_v<U, T>, int> = 0>
 MOZ_IMPLICIT ReadResult(U&& aData)
     : mIsOk(true), mData(std::forward<U>(aData)) {}

 template <typename... Args>
 explicit ReadResult(std::in_place_t, Args&&... aArgs)
     : mIsOk(true), mData(std::forward<Args>(aArgs)...) {}

 ReadResult(const ReadResult&) = default;
 ReadResult(ReadResult&&) = default;

 template <typename U, std::enable_if_t<std::is_convertible_v<U, T>, int> = 0>
 MOZ_IMPLICIT ReadResult& operator=(U&& aData) {
   mIsOk = true;
   mData = std::forward<U>(aData);
   return *this;
 }

 ReadResult& operator=(const ReadResult&) = default;
 ReadResult& operator=(ReadResult&&) noexcept = default;

 // Check if the ReadResult contains a valid value.
 explicit operator bool() const { return isOk(); }
 bool isOk() const { return mIsOk; }

 // Get the data from this ReadResult.
 T& get() {
   MOZ_ASSERT(mIsOk);
   return mData;
 }
 const T& get() const {
   MOZ_ASSERT(mIsOk);
   return mData;
 }

 T& operator*() { return get(); }
 const T& operator*() const { return get(); }

 T* operator->() { return &get(); }
 const T* operator->() const { return &get(); }

 // Try to extract a `Maybe<T>` from this ReadResult.
 mozilla::Maybe<T> TakeMaybe() {
   if (mIsOk) {
     mIsOk = false;
     return mozilla::Some(std::move(mData));
   }
   return mozilla::Nothing();
 }

 // Get the underlying data from this ReadResult, even if not OK.
 //
 // This is only available for types which are default constructible, and is
 // used to optimize old-style `ReadParam` calls.
 T& GetStorage() { return mData; }

 // Compliment to `GetStorage` used to set the ReadResult into an OK state
 // without constructing the underlying value.
 void SetOk(bool aIsOk) { mIsOk = aIsOk; }

private:
 bool mIsOk = false;
 T mData{};
};

template <typename T>
class ReadResult<T, false> {
public:
 ReadResult() = default;

 template <typename U, std::enable_if_t<std::is_convertible_v<U, T>, int> = 0>
 MOZ_IMPLICIT ReadResult(U&& aData)
     : mData(std::in_place, std::forward<U>(aData)) {}

 template <typename... Args>
 explicit ReadResult(std::in_place_t, Args&&... aArgs)
     : mData(std::in_place, std::forward<Args>(aArgs)...) {}

 ReadResult(const ReadResult&) = default;
 ReadResult(ReadResult&&) = default;

 template <typename U, std::enable_if_t<std::is_convertible_v<U, T>, int> = 0>
 MOZ_IMPLICIT ReadResult& operator=(U&& aData) {
   mData.reset();
   mData.emplace(std::forward<U>(aData));
   return *this;
 }

 ReadResult& operator=(const ReadResult&) = default;
 ReadResult& operator=(ReadResult&&) noexcept = default;

 // Check if the ReadResult contains a valid value.
 explicit operator bool() const { return isOk(); }
 bool isOk() const { return mData.isSome(); }

 // Get the data from this ReadResult.
 T& get() { return mData.ref(); }
 const T& get() const { return mData.ref(); }

 T& operator*() { return get(); }
 const T& operator*() const { return get(); }

 T* operator->() { return &get(); }
 const T* operator->() const { return &get(); }

 // Try to extract a `Maybe<T>` from this ReadResult.
 mozilla::Maybe<T> TakeMaybe() { return std::move(mData); }

 // These methods are only available if the type is default constructible.
 T& GetStorage() = delete;
 void SetOk(bool aIsOk) = delete;

private:
 mozilla::Maybe<T> mData;
};

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

class MessageIterator {
public:
 explicit MessageIterator(const Message& m) : msg_(m), iter_(m) {}
 int NextInt() const {
   int val;
   if (!msg_.ReadInt(&iter_, &val)) NOTREACHED();
   return val;
 }
 intptr_t NextIntPtr() const {
   intptr_t val;
   if (!msg_.ReadIntPtr(&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;
 }

private:
 const Message& msg_;
 mutable PickleIterator iter_;
};

//-----------------------------------------------------------------------------
// ParamTraits specializations, etc.
//
// The full set of types ParamTraits is specialized upon contains *possibly*
// repeated types: unsigned long may be uint32_t or size_t, unsigned long long
// may be uint64_t or size_t, nsresult may be uint32_t, and so on.  You can't
// have ParamTraits<unsigned int> *and* ParamTraits<uint32_t> if unsigned int
// is uint32_t -- that's multiple definitions, and you can only have one.
//
// You could use #ifs and macro conditions to avoid duplicates, but they'd be
// hairy: heavily dependent upon OS and compiler author choices, forced to
// address all conflicts by hand.  Happily there's a better way.  The basic
// idea looks like this, where T -> U represents T inheriting from U:
//
// class ParamTraits<P>
// |
// --> class ParamTraits1<P>
//     |
//     --> class ParamTraits2<P>
//         |
//         --> class ParamTraitsN<P> // or however many levels
//
// The default specialization of ParamTraits{M}<P> is an empty class that
// inherits from ParamTraits{M + 1}<P> (or nothing in the base case).
//
// Now partition the set of parameter types into sets without duplicates.
// Assign each set of types to a level M.  Then specialize ParamTraitsM for
// each of those types.  A reference to ParamTraits<P> will consist of some
// number of empty classes inheriting in sequence, ending in a non-empty
// ParamTraits{N}<P>.  It's okay for the parameter types to be duplicative:
// either name of a type will resolve to the same ParamTraits{N}<P>.
//
// The nice thing is that because templates are instantiated lazily, if we
// indeed have uint32_t == unsigned int, say, with the former in level N and
// the latter in M > N, ParamTraitsM<unsigned int> won't be created (as long as
// nobody uses ParamTraitsM<unsigned int>, but why would you), and no duplicate
// code will be compiled or extra symbols generated.  It's as efficient at
// runtime as manually figuring out and avoiding conflicts by #ifs.
//
// The scheme we follow below names the various classes according to the types
// in them, and the number of ParamTraits levels is larger, but otherwise it's
// exactly the above idea.
//

template <class P>
struct ParamTraits;

template <typename P>
inline void WriteParam(MessageWriter* writer, P&& p) {
 ParamTraits<std::decay_t<P>>::Write(writer, std::forward<P>(p));
}

namespace detail {

template <typename P>
inline constexpr auto ParamTraitsReadUsesOutParam()
   -> decltype(ParamTraits<P>::Read(std::declval<MessageReader*>(),
                                    std::declval<P*>())) {
 return true;
}

template <typename P>
inline constexpr auto ParamTraitsReadUsesOutParam()
   -> decltype(ParamTraits<P>::Read(std::declval<MessageReader*>()), bool{}) {
 return false;
}

}  // namespace detail

template <typename P>
[[nodiscard]] inline bool ReadParam(MessageReader* reader, P* p) {
 if constexpr (!detail::ParamTraitsReadUsesOutParam<P>()) {
   auto maybe = ParamTraits<P>::Read(reader);
   if (maybe) {
     *p = std::move(*maybe);
     return true;
   }
   return false;
 } else {
   return ParamTraits<P>::Read(reader, p);
 }
}

template <typename P>
[[nodiscard]] inline ReadResult<P> ReadParam(MessageReader* reader) {
 if constexpr (!detail::ParamTraitsReadUsesOutParam<P>()) {
   return ParamTraits<P>::Read(reader);
 } else {
   ReadResult<P> p;
   p.SetOk(ParamTraits<P>::Read(reader, &p.GetStorage()));
   return p;
 }
}

class MOZ_STACK_CLASS MessageBufferWriter {
public:
 // Create a MessageBufferWriter to write `full_len` bytes into `writer`.
 // If the length exceeds a threshold, a shared memory region may be used
 // instead of including the data inline.
 //
 // NOTE: This does _NOT_ write out the length of the buffer.
 // NOTE: Data written this way _MUST_ be read using `MessageBufferReader`.
 MessageBufferWriter(MessageWriter* writer, uint32_t full_len);
 ~MessageBufferWriter();

 MessageBufferWriter(const MessageBufferWriter&) = delete;
 MessageBufferWriter& operator=(const MessageBufferWriter&) = delete;

 // Write `len` bytes from `data` into the message.
 //
 // Exactly `full_len` bytes should be written across multiple calls before the
 // `MessageBufferWriter` is destroyed.
 //
 // WARNING: all writes (other than the last write) must be multiples of 4
 // bytes in length. Not doing this will lead to padding being introduced into
 // the payload and break things. This can probably be improved in the future
 // with deeper integration between `MessageBufferWriter` and `Pickle`.
 bool WriteBytes(const void* data, uint32_t len);

private:
 MessageWriter* writer_;
 mozilla::UniquePtr<mozilla::ipc::shared_memory::Cursor> shmem_cursor_;
 uint32_t remaining_ = 0;
};

class MOZ_STACK_CLASS MessageBufferReader {
public:
 // Create a MessageBufferReader to read `full_len` bytes from `reader` which
 // were written using `MessageBufferWriter`.
 //
 // NOTE: This may consume a shared memory region from the message, meaning
 // that the same data cannot be read multiple times.
 // NOTE: Data read this way _MUST_ be written using `MessageBufferWriter`.
 MessageBufferReader(MessageReader* reader, uint32_t full_len);
 ~MessageBufferReader();

 MessageBufferReader(const MessageBufferReader&) = delete;
 MessageBufferReader& operator=(const MessageBufferReader&) = delete;

 // Read `count` bytes from the message into `data`.
 //
 // Exactly `full_len` bytes should be read across multiple calls before the
 // `MessageBufferReader` is destroyed.
 //
 // WARNING: all reads (other than the last read) must be multiples of 4 bytes
 // in length. Not doing this will lead to bytes being skipped in the payload
 // and break things. This can probably be improved in the future with deeper
 // integration between `MessageBufferReader` and `Pickle`.
 [[nodiscard]] bool ReadBytesInto(void* data, uint32_t len);

private:
 MessageReader* reader_;
 mozilla::UniquePtr<mozilla::ipc::shared_memory::Cursor> shmem_cursor_;
 uint32_t remaining_ = 0;
};

// Whether or not it is safe to serialize the given type using
// `WriteBytesOrShmem`.
template <typename P>
constexpr bool kUseWriteBytes =
   !std::is_same_v<std::remove_const_t<std::remove_reference_t<P>>, bool> &&
   (std::is_integral_v<std::remove_const_t<std::remove_reference_t<P>>> ||
    std::is_floating_point_v<std::remove_const_t<std::remove_reference_t<P>>>);

/**
* Helper for writing a contiguous sequence (such as for a string or array) into
* a message, with optimizations for basic integral and floating point types.
*
* Integral types will be copied into shared memory if the sequence exceeds 64k
* bytes in size.
*
* Values written with this method must be read with `ReadSequenceParam`.
*
* The type parameter specifies the semantics to use, and should generally
* either be `P&&` or `const P&`. The constness of the `data` argument should
* match this parameter.
*/
template <typename P>
void WriteSequenceParam(MessageWriter* writer, std::remove_reference_t<P>* data,
                       size_t length) {
 mozilla::CheckedUint32 ipc_length(length);
 if (!ipc_length.isValid()) {
   writer->FatalError("invalid length passed to WriteSequenceParam");
   return;
 }
 writer->WriteUInt32(ipc_length.value());

 if constexpr (kUseWriteBytes<P>) {
   mozilla::CheckedUint32 byte_length =
       ipc_length * sizeof(std::remove_reference_t<P>);
   if (!byte_length.isValid()) {
     writer->FatalError("invalid byte length in WriteSequenceParam");
     return;
   }
   MessageBufferWriter buf_writer(writer, byte_length.value());
   buf_writer.WriteBytes(data, byte_length.value());
 } else {
   auto* end = data + length;
   for (auto* it = data; it != end; ++it) {
     WriteParam(writer, std::forward<P>(*it));
   }
 }
}

template <typename P>
bool ReadSequenceParamImpl(MessageReader* reader, P* data, uint32_t length) {
 if (length == 0) {
   return true;
 }
 if (!data) {
   reader->FatalError("allocation failed in ReadSequenceParam");
   return false;
 }

 if constexpr (kUseWriteBytes<P>) {
   mozilla::CheckedUint32 byte_length(length);
   byte_length *= sizeof(P);
   if (!byte_length.isValid()) {
     reader->FatalError("invalid byte length in ReadSequenceParam");
     return false;
   }
   MessageBufferReader buf_reader(reader, byte_length.value());
   return buf_reader.ReadBytesInto(data, byte_length.value());
 } else {
   P* end = data + length;
   for (auto* it = data; it != end; ++it) {
     if (!ReadParam(reader, it)) {
       return false;
     }
   }
   return true;
 }
}

template <typename P, typename I>
bool ReadSequenceParamImpl(MessageReader* reader, mozilla::Maybe<I>&& data,
                          uint32_t length) {
 static_assert(!kUseWriteBytes<P>,
               "Cannot return an output iterator if !kUseWriteBytes<P>");
 static_assert(
     std::is_base_of_v<std::output_iterator_tag,
                       typename std::iterator_traits<I>::iterator_category>,
     "must be Maybe<output iterator>");
 if (length == 0) {
   return true;
 }
 if (!data) {
   reader->FatalError("allocation failed in ReadSequenceParam");
   return false;
 }

 for (uint32_t i = 0; i < length; ++i) {
   auto elt = ReadParam<P>(reader);
   if (!elt) {
     return false;
   }
   *data.ref() = std::move(*elt);
   ++data.ref();
 }
 return true;
}

/**
* Helper for reading a contiguous sequence (such as a string or array) into a
* message which was previously written using `WriteSequenceParam`.
*
* The function argument `allocator` will be called with the length of the
* sequence, and must return either a pointer to the memory region which the
* sequence should be read into, or a Maybe of a C++ output iterator which will
* infallibly accept length elements, and append them to the output sequence.
*
* If the type satisfies kUseWriteBytes, output iterators are not supported.
*/
template <typename P, typename F>
[[nodiscard]] bool ReadSequenceParam(MessageReader* reader, F&& allocator) {
 uint32_t length = 0;
 if (!reader->ReadUInt32(&length)) {
   reader->FatalError("failed to read byte length in ReadSequenceParam");
   return false;
 }

 return ReadSequenceParamImpl<P>(reader, allocator(length), length);
}

// Fundamental types.

template <class P>
struct ParamTraitsFundamental;

template <>
struct ParamTraitsFundamental<bool> {
 typedef bool param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteBool(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadBool(r);
 }
};

template <>
struct ParamTraitsFundamental<char> {
 typedef char param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteScalar(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadScalar(r);
 }
};

template <>
struct ParamTraitsFundamental<int> {
 typedef int param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteInt(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadInt(r);
 }
};

template <>
struct ParamTraitsFundamental<long> {
 typedef long param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteLong(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadLong(r);
 }
};

template <>
struct ParamTraitsFundamental<unsigned long> {
 typedef unsigned long param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteULong(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadULong(r);
 }
};

template <>
struct ParamTraitsFundamental<long long> {
 typedef long long param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteBytes(&p, sizeof(param_type));
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadBytesInto(r, sizeof(*r));
 }
};

template <>
struct ParamTraitsFundamental<unsigned long long> {
 typedef unsigned long long param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteBytes(&p, sizeof(param_type));
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadBytesInto(r, sizeof(*r));
 }
};

template <>
struct ParamTraitsFundamental<double> {
 typedef double param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteDouble(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadDouble(r);
 }
};

// Fixed-size <stdint.h> types.

template <class P>
struct ParamTraitsFixed : ParamTraitsFundamental<P> {};

template <>
struct ParamTraitsFixed<int8_t> {
 typedef int8_t param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteScalar(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadScalar(r);
 }
};

template <>
struct ParamTraitsFixed<uint8_t> {
 typedef uint8_t param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteScalar(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadScalar(r);
 }
};

template <>
struct ParamTraitsFixed<int16_t> {
 typedef int16_t param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteInt16(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadInt16(r);
 }
};

template <>
struct ParamTraitsFixed<uint16_t> {
 typedef uint16_t param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteUInt16(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadUInt16(r);
 }
};

template <>
struct ParamTraitsFixed<uint32_t> {
 typedef uint32_t param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteUInt32(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadUInt32(r);
 }
};

template <>
struct ParamTraitsFixed<int64_t> {
 typedef int64_t param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteInt64(p);
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadInt64(r);
 }
};

template <>
struct ParamTraitsFixed<uint64_t> {
 typedef uint64_t param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteInt64(static_cast<int64_t>(p));
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadInt64(reinterpret_cast<int64_t*>(r));
 }
};

// std::* types.

template <class P>
struct ParamTraitsStd : ParamTraitsFixed<P> {};

template <class T>
struct ParamTraitsStd<std::basic_string<T>> {
 typedef std::basic_string<T> param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   WriteSequenceParam<const T&>(writer, p.data(), p.size());
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return ReadSequenceParam<T>(reader, [&](uint32_t length) -> T* {
     r->resize(length);
     return r->data();
   });
 }
};

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

template <>
struct ParamTraitsStd<std::monostate> {
 using param_type = std::monostate;
 static void Write(MessageWriter*, const param_type&) {}
 static bool Read(MessageReader*, param_type*) { return true; }
};

template <class... Ts>
struct ParamTraitsStd<std::variant<Ts...>> {
 using param_type = std::variant<Ts...>;

 template <class U>
 static void Write(MessageWriter* writer, U&& p) {
   WriteParam(writer, static_cast<uint64_t>(p.index()));
   std::visit(
       [&](auto&& param) {
         WriteParam(writer, std::forward<decltype(param)>(param));
       },
       std::forward<U>(p));
 }

 static ReadResult<param_type> Read(MessageReader* reader) {
   uint64_t index;
   if (!ReadParam(reader, &index)) {
     return {};
   }
   return ReadI<0>(reader, static_cast<size_t>(index));
 }

private:
 template <size_t I>
 static ReadResult<param_type> ReadI(MessageReader* reader, size_t index) {
   if constexpr (I >= std::variant_size_v<param_type>) {
     return {};  // No matching variant index
   } else {
     if (index == I) {
       using alt_type = std::variant_alternative_t<I, param_type>;
       ReadResult<alt_type> alt = ReadParam<alt_type>(reader);
       if (!alt) {
         return {};
       }
       return ReadResult<param_type>{std::in_place, std::in_place_index<I>,
                                     std::move(alt.get())};
     }
     return ReadI<I + 1>(reader, index);
   }
 }
};

// Windows-specific types.

template <class P>
struct ParamTraitsWindows : ParamTraitsStd<P> {};

#if defined(XP_WIN)
template <>
struct ParamTraitsWindows<HANDLE> {
 static_assert(sizeof(HANDLE) == sizeof(intptr_t), "Wrong size for HANDLE?");

 static void Write(MessageWriter* writer, HANDLE p) {
   writer->WriteIntPtr(reinterpret_cast<intptr_t>(p));
 }
 static bool Read(MessageReader* reader, HANDLE* r) {
   return reader->ReadIntPtr(reinterpret_cast<intptr_t*>(r));
 }
};

template <>
struct ParamTraitsWindows<HWND> {
 static_assert(sizeof(HWND) == sizeof(intptr_t), "Wrong size for HWND?");

 static void Write(MessageWriter* writer, HWND p) {
   writer->WriteIntPtr(reinterpret_cast<intptr_t>(p));
 }
 static bool Read(MessageReader* reader, HWND* r) {
   return reader->ReadIntPtr(reinterpret_cast<intptr_t*>(r));
 }
};
#endif  // defined(XP_WIN)

// Various ipc/chromium types.

template <class P>
struct ParamTraitsIPC : ParamTraitsWindows<P> {};

// `UniqueFileHandle` may be serialized over IPC channels. On the receiving
// side, the UniqueFileHandle is a valid duplicate of the handle which was
// transmitted.
//
// When sending a UniqueFileHandle, the handle must be valid at the time of
// transmission. As transmission is asynchronous, this requires passing
// ownership of the handle to IPC.
//
// A UniqueFileHandle may only be read once. After it has been read once, it
// will be consumed, and future reads will return an invalid handle.
template <>
struct ParamTraitsIPC<mozilla::UniqueFileHandle> {
 typedef mozilla::UniqueFileHandle param_type;
 static void Write(MessageWriter* writer, param_type&& p) {
   const bool valid = p != nullptr;
   WriteParam(writer, valid);
   if (valid) {
     if (!writer->WriteFileHandle(std::move(p))) {
       writer->FatalError("Too many file handles for one message!");
       NOTREACHED() << "Too many file handles for one message!";
     }
   }
 }
 static bool Read(MessageReader* reader, param_type* r) {
   bool valid;
   if (!ReadParam(reader, &valid)) {
     reader->FatalError("Error reading file handle validity");
     return false;
   }

   if (!valid) {
     *r = nullptr;
     return true;
   }

   if (!reader->ConsumeFileHandle(r)) {
     reader->FatalError("File handle not found in message!");
     return false;
   }
   return true;
 }
};

#if defined(XP_DARWIN)
// `UniqueMachSendRight` may be serialized over IPC channels. On the receiving
// side, the UniqueMachSendRight is the local name of the right which was
// transmitted.
//
// When sending a UniqueMachSendRight, the right must be valid at the time of
// transmission. As transmission is asynchronous, this requires passing
// ownership of the handle to IPC.
//
// A UniqueMachSendRight may only be read once. After it has been read once, it
// will be consumed, and future reads will return an invalid right.
template <>
struct ParamTraitsIPC<mozilla::UniqueMachSendRight> {
 typedef mozilla::UniqueMachSendRight param_type;
 static void Write(MessageWriter* writer, param_type&& p) {
   const bool valid = p != nullptr;
   WriteParam(writer, valid);
   if (valid) {
     if (!writer->WriteMachSendRight(std::move(p))) {
       writer->FatalError("Too many mach send rights for one message!");
       NOTREACHED() << "Too many mach send rights for one message!";
     }
   }
 }
 static bool Read(MessageReader* reader, param_type* r) {
   bool valid;
   if (!ReadParam(reader, &valid)) {
     reader->FatalError("Error reading mach send right validity");
     return false;
   }

   if (!valid) {
     *r = nullptr;
     return true;
   }

   if (!reader->ConsumeMachSendRight(r)) {
     reader->FatalError("Mach send right not found in message!");
     return false;
   }
   return true;
 }
};

// `UniqueMachReceiveRight` may be serialized over IPC channels. On the
// receiving side, the UniqueMachReceiveRight is the local name of the right
// which was transmitted.
//
// When sending a UniqueMachReceiveRight, the right must be valid at the time of
// transmission. As transmission is asynchronous, this requires passing
// ownership of the handle to IPC.
//
// A UniqueMachReceiveRight may only be read once. After it has been read once,
// it will be consumed, and future reads will return an invalid right.
template <>
struct ParamTraitsIPC<mozilla::UniqueMachReceiveRight> {
 typedef mozilla::UniqueMachReceiveRight param_type;
 static void Write(MessageWriter* writer, param_type&& p) {
   const bool valid = p != nullptr;
   WriteParam(writer, valid);
   if (valid) {
     if (!writer->WriteMachReceiveRight(std::move(p))) {
       writer->FatalError("Too many mach receive rights for one message!");
       NOTREACHED() << "Too many mach receive rights for one message!";
     }
   }
 }
 static bool Read(MessageReader* reader, param_type* r) {
   bool valid;
   if (!ReadParam(reader, &valid)) {
     reader->FatalError("Error reading mach receive right validity");
     return false;
   }

   if (!valid) {
     *r = nullptr;
     return true;
   }

   if (!reader->ConsumeMachReceiveRight(r)) {
     reader->FatalError("Mach receive right not found in message!");
     return false;
   }
   return true;
 }
};
#endif

// Mozilla-specific types.

template <class P>
struct ParamTraitsMozilla : ParamTraitsIPC<P> {};

// Sending-only specialization for mozilla::Span<T const>. Uses an identical
// serialization format as `const nsTArray<T>&`.
template <class T>
struct ParamTraitsMozilla<mozilla::Span<const T>> {
 static void Write(MessageWriter* writer, mozilla::Span<const T> p) {
   WriteSequenceParam<const T>(writer, p.Elements(), p.Length());
 }
};

template <>
struct ParamTraitsMozilla<nsresult> {
 typedef nsresult param_type;
 static void Write(MessageWriter* writer, const param_type& p) {
   writer->WriteUInt32(static_cast<uint32_t>(p));
 }
 static bool Read(MessageReader* reader, param_type* r) {
   return reader->ReadUInt32(reinterpret_cast<uint32_t*>(r));
 }
};

// When being passed `RefPtr<T>` or `nsCOMPtr<T>`, forward to a specialization
// for the underlying target type. The parameter type will be passed as `T*`,
// and result as `RefPtr<T>*`.
//
// This is done explicitly to ensure that the deleted `&&` overload for
// `operator T*` is not selected in generic contexts, and to support
// deserializing into `nsCOMPtr<T>`.
template <class T>
struct ParamTraitsMozilla<RefPtr<T>> {
 static void Write(MessageWriter* writer, const RefPtr<T>& p) {
   ParamTraits<T*>::Write(writer, p.get());
 }

 static bool Read(MessageReader* reader, RefPtr<T>* r) {
   return ParamTraits<T*>::Read(reader, r);
 }
};

template <class T>
struct ParamTraitsMozilla<nsCOMPtr<T>> {
 static void Write(MessageWriter* writer, const nsCOMPtr<T>& p) {
   ParamTraits<T*>::Write(writer, p.get());
 }

 static bool Read(MessageReader* reader, nsCOMPtr<T>* r) {
   RefPtr<T> refptr;
   if (!ParamTraits<T*>::Read(reader, &refptr)) {
     return false;
   }
   *r = std::move(refptr);
   return true;
 }
};

template <class T>
struct ParamTraitsMozilla<mozilla::NotNull<T>> {
 static void Write(MessageWriter* writer, const mozilla::NotNull<T>& p) {
   ParamTraits<T>::Write(writer, p.get());
 }

 static ReadResult<mozilla::NotNull<T>> Read(MessageReader* reader) {
   auto ptr = ReadParam<T>(reader);
   if (!ptr) {
     return {};
   }
   if (!*ptr) {
     reader->FatalError("unexpected null value");
     return {};
   }
   return mozilla::WrapNotNull(std::move(*ptr));
 }
};

// Finally, ParamTraits itself.

template <class P>
struct ParamTraits : ParamTraitsMozilla<P> {};

}  // namespace IPC

#endif  // CHROME_COMMON_IPC_MESSAGE_UTILS_H_