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//===---- SimplePackedSerialization.h - simple serialization ----*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// The behavior of the utilities in this header must be synchronized with the

// behavior of the utilities in

// compiler-rt/lib/orc/simple_packed_serialization.h.

//

// The Simple Packed Serialization (SPS) utilities are used to generate

// argument and return buffers for wrapper functions using the following

// serialization scheme:

//

// Primitives (signed types should be two's complement):

//   bool, char, int8_t, uint8_t -- 8-bit (0=false, 1=true)

//   int16_t, uint16_t           -- 16-bit little endian

//   int32_t, uint32_t           -- 32-bit little endian

//   int64_t, int64_t            -- 64-bit little endian

//

// Sequence<T>:

//   Serialized as the sequence length (as a uint64_t) followed by the

//   serialization of each of the elements without padding.

//

// Tuple<T1, ..., TN>:

//   Serialized as each of the element types from T1 to TN without padding.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_EXECUTIONENGINE_ORC_SHARED_SIMPLEPACKEDSERIALIZATION_H

#define LLVM_EXECUTIONENGINE_ORC_SHARED_SIMPLEPACKEDSERIALIZATION_H

#include "llvm/ADT/STLExtras.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/StringMap.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/Support/Error.h"

#include "llvm/Support/SwapByteOrder.h"

#include <limits>

#include <optional>

#include <string>

#include <tuple>

#include <type_traits>

#include <utility>

#include <vector>

namespace llvm {

namespace orc {

namespace shared {

/// Output char buffer with overflow check.

class SPSOutputBuffer {

public:

  SPSOutputBuffer(char *Buffer, size_t Remaining)

      : Buffer(Buffer), Remaining(Remaining) {}

  bool write(const char *Data, size_t Size) {

    assert(Data && "Data must not be null");

    if (Size > Remaining)

      return false;

    memcpy(Buffer, Data, Size);

    Buffer += Size;

    Remaining -= Size;

    return true;

  }

private:

  char *Buffer = nullptr;

  size_t Remaining = 0;

};

/// Input char buffer with underflow check.

class SPSInputBuffer {

public:

  SPSInputBuffer() = default;

  SPSInputBuffer(const char *Buffer, size_t Remaining)

      : Buffer(Buffer), Remaining(Remaining) {}

  bool read(char *Data, size_t Size) {

    if (Size > Remaining)

      return false;

    memcpy(Data, Buffer, Size);

    Buffer += Size;

    Remaining -= Size;

    return true;

  }

  const char *data() const { return Buffer; }

  bool skip(size_t Size) {

    if (Size > Remaining)

      return false;

    Buffer += Size;

    Remaining -= Size;

    return true;

  }

private:

  const char *Buffer = nullptr;

  size_t Remaining = 0;

};

/// Specialize to describe how to serialize/deserialize to/from the given

/// concrete type.

template <typename SPSTagT, typename ConcreteT, typename _ = void>

class SPSSerializationTraits;

/// A utility class for serializing to a blob from a variadic list.

template <typename... ArgTs> class SPSArgList;

// Empty list specialization for SPSArgList.

template <> class SPSArgList<> {

public:

  static size_t size() { return 0; }

  static bool serialize(SPSOutputBuffer &OB) { return true; }

  static bool deserialize(SPSInputBuffer &IB) { return true; }

  static bool serializeToSmallVector(SmallVectorImpl<char> &V) { return true; }

  static bool deserializeFromSmallVector(const SmallVectorImpl<char> &V) {

    return true;

  }

};

// Non-empty list specialization for SPSArgList.

template <typename SPSTagT, typename... SPSTagTs>

class SPSArgList<SPSTagT, SPSTagTs...> {

public:

  // FIXME: This typedef is here to enable SPS arg serialization from

  // JITLink. It can be removed once JITLink can access SPS directly.

  using OutputBuffer = SPSOutputBuffer;

  template <typename ArgT, typename... ArgTs>

  static size_t size(const ArgT &Arg, const ArgTs &...Args) {

    return SPSSerializationTraits<SPSTagT, ArgT>::size(Arg) +

           SPSArgList<SPSTagTs...>::size(Args...);

  }

  template <typename ArgT, typename... ArgTs>

  static bool serialize(SPSOutputBuffer &OB, const ArgT &Arg,

                        const ArgTs &...Args) {

    return SPSSerializationTraits<SPSTagT, ArgT>::serialize(OB, Arg) &&

           SPSArgList<SPSTagTs...>::serialize(OB, Args...);

  }

  template <typename ArgT, typename... ArgTs>

  static bool deserialize(SPSInputBuffer &IB, ArgT &Arg, ArgTs &...Args) {

    return SPSSerializationTraits<SPSTagT, ArgT>::deserialize(IB, Arg) &&

           SPSArgList<SPSTagTs...>::deserialize(IB, Args...);

  }

};

/// SPS serialization for integral types, bool, and char.

template <typename SPSTagT>

class SPSSerializationTraits<

    SPSTagT, SPSTagT,

    std::enable_if_t<std::is_same<SPSTagT, bool>::value ||

                     std::is_same<SPSTagT, char>::value ||

                     std::is_same<SPSTagT, int8_t>::value ||

                     std::is_same<SPSTagT, int16_t>::value ||

                     std::is_same<SPSTagT, int32_t>::value ||

                     std::is_same<SPSTagT, int64_t>::value ||

                     std::is_same<SPSTagT, uint8_t>::value ||

                     std::is_same<SPSTagT, uint16_t>::value ||

                     std::is_same<SPSTagT, uint32_t>::value ||

                     std::is_same<SPSTagT, uint64_t>::value>> {

public:

  static size_t size(const SPSTagT &Value) { return sizeof(SPSTagT); }

  static bool serialize(SPSOutputBuffer &OB, const SPSTagT &Value) {

    SPSTagT Tmp = Value;

    if (sys::IsBigEndianHost)

      sys::swapByteOrder(Tmp);

    return OB.write(reinterpret_cast<const char *>(&Tmp), sizeof(Tmp));

  }

  static bool deserialize(SPSInputBuffer &IB, SPSTagT &Value) {

    SPSTagT Tmp;

    if (!IB.read(reinterpret_cast<char *>(&Tmp), sizeof(Tmp)))

      return false;

    if (sys::IsBigEndianHost)

      sys::swapByteOrder(Tmp);

    Value = Tmp;

    return true;

  }

};

// Any empty placeholder suitable as a substitute for void when deserializing

class SPSEmpty {};

/// SPS tag type for tuples.

///

/// A blob tuple should be serialized by serializing each of the elements in

/// sequence.

template <typename... SPSTagTs> class SPSTuple {

public:

  /// Convenience typedef of the corresponding arg list.

  typedef SPSArgList<SPSTagTs...> AsArgList;

};

/// SPS tag type for optionals.

///

/// SPSOptionals should be serialized as a bool with true indicating that an

/// SPSTagT value is present, and false indicating that there is no value.

/// If the boolean is true then the serialized SPSTagT will follow immediately

/// after it.

template <typename SPSTagT> class SPSOptional {};

/// SPS tag type for sequences.

///

/// SPSSequences should be serialized as a uint64_t sequence length,

/// followed by the serialization of each of the elements.

template <typename SPSElementTagT> class SPSSequence;

/// SPS tag type for strings, which are equivalent to sequences of chars.

using SPSString = SPSSequence<char>;

/// SPS tag type for maps.

///

/// SPS maps are just sequences of (Key, Value) tuples.

template <typename SPSTagT1, typename SPSTagT2>

using SPSMap = SPSSequence<SPSTuple<SPSTagT1, SPSTagT2>>;

/// Serialization for SPSEmpty type.

template <> class SPSSerializationTraits<SPSEmpty, SPSEmpty> {

public:

  static size_t size(const SPSEmpty &EP) { return 0; }

  static bool serialize(SPSOutputBuffer &OB, const SPSEmpty &BE) {

    return true;

  }

  static bool deserialize(SPSInputBuffer &IB, SPSEmpty &BE) { return true; }

};

/// Specialize this to implement 'trivial' sequence serialization for

/// a concrete sequence type.

///

/// Trivial sequence serialization uses the sequence's 'size' member to get the

/// length of the sequence, and uses a range-based for loop to iterate over the

/// elements.

///

/// Specializing this template class means that you do not need to provide a

/// specialization of SPSSerializationTraits for your type.

template <typename SPSElementTagT, typename ConcreteSequenceT>

class TrivialSPSSequenceSerialization {

public:

  static constexpr bool available = false;

};

/// Specialize this to implement 'trivial' sequence deserialization for

/// a concrete sequence type.

///

/// Trivial deserialization calls a static 'reserve(SequenceT&)' method on your

/// specialization (you must implement this) to reserve space, and then calls

/// a static 'append(SequenceT&, ElementT&) method to append each of the

/// deserialized elements.

///

/// Specializing this template class means that you do not need to provide a

/// specialization of SPSSerializationTraits for your type.

template <typename SPSElementTagT, typename ConcreteSequenceT>

class TrivialSPSSequenceDeserialization {

public:

  static constexpr bool available = false;

};

/// Trivial std::string -> SPSSequence<char> serialization.

template <> class TrivialSPSSequenceSerialization<char, std::string> {

public:

  static constexpr bool available = true;

};

/// Trivial SPSSequence<char> -> std::string deserialization.

template <> class TrivialSPSSequenceDeserialization<char, std::string> {

public:

  static constexpr bool available = true;

  using element_type = char;

  static void reserve(std::string &S, uint64_t Size) { S.reserve(Size); }

  static bool append(std::string &S, char C) {

    S.push_back(C);

    return true;

  }

};

/// Trivial std::vector<T> -> SPSSequence<SPSElementTagT> serialization.

template <typename SPSElementTagT, typename T>

class TrivialSPSSequenceSerialization<SPSElementTagT, std::vector<T>> {

public:

  static constexpr bool available = true;

};

/// Trivial SPSSequence<SPSElementTagT> -> std::vector<T> deserialization.

template <typename SPSElementTagT, typename T>

class TrivialSPSSequenceDeserialization<SPSElementTagT, std::vector<T>> {

public:

  static constexpr bool available = true;

  using element_type = typename std::vector<T>::value_type;

  static void reserve(std::vector<T> &V, uint64_t Size) { V.reserve(Size); }

  static bool append(std::vector<T> &V, T E) {

    V.push_back(std::move(E));

    return true;

  }

};

/// Trivial SmallVectorImpl<T> -> SPSSequence<char> serialization.

template <typename SPSElementTagT, typename T>

class TrivialSPSSequenceSerialization<SPSElementTagT, SmallVectorImpl<T>> {

public:

  static constexpr bool available = true;

};

/// Trivial SPSSequence<SPSElementTagT> -> SmallVectorImpl<T> deserialization.

template <typename SPSElementTagT, typename T>

class TrivialSPSSequenceDeserialization<SPSElementTagT, SmallVectorImpl<T>> {

public:

  static constexpr bool available = true;

  using element_type = typename SmallVectorImpl<T>::value_type;

  static void reserve(SmallVectorImpl<T> &V, uint64_t Size) { V.reserve(Size); }

  static bool append(SmallVectorImpl<T> &V, T E) {

    V.push_back(std::move(E));

    return true;

  }

};

/// Trivial SmallVectorImpl<T> -> SPSSequence<char> serialization.

template <typename SPSElementTagT, typename T, unsigned N>

class TrivialSPSSequenceSerialization<SPSElementTagT, SmallVector<T, N>>

    : public TrivialSPSSequenceSerialization<SPSElementTagT,

                                             SmallVectorImpl<T>> {};

/// Trivial SPSSequence<SPSElementTagT> -> SmallVectorImpl<T> deserialization.

template <typename SPSElementTagT, typename T, unsigned N>

class TrivialSPSSequenceDeserialization<SPSElementTagT, SmallVector<T, N>>

    : public TrivialSPSSequenceDeserialization<SPSElementTagT,

                                               SmallVectorImpl<T>> {};

/// Trivial ArrayRef<T> -> SPSSequence<SPSElementTagT> serialization.

template <typename SPSElementTagT, typename T>

class TrivialSPSSequenceSerialization<SPSElementTagT, ArrayRef<T>> {

public:

  static constexpr bool available = true;

};

/// Specialized SPSSequence<char> -> ArrayRef<char> serialization.

///

/// On deserialize, points directly into the input buffer.

template <> class SPSSerializationTraits<SPSSequence<char>, ArrayRef<char>> {

public:

  static size_t size(const ArrayRef<char> &A) {

    return SPSArgList<uint64_t>::size(static_cast<uint64_t>(A.size())) +

           A.size();

  }

  static bool serialize(SPSOutputBuffer &OB, const ArrayRef<char> &A) {

    if (!SPSArgList<uint64_t>::serialize(OB, static_cast<uint64_t>(A.size())))

      return false;

    if (A.empty()) // Empty ArrayRef may have null data, so bail out early.

      return true;

    return OB.write(A.data(), A.size());

  }

  static bool deserialize(SPSInputBuffer &IB, ArrayRef<char> &A) {

    uint64_t Size;

    if (!SPSArgList<uint64_t>::deserialize(IB, Size))

      return false;

    if (Size > std::numeric_limits<size_t>::max())

      return false;

    A = {Size ? IB.data() : nullptr, static_cast<size_t>(Size)};

    return IB.skip(Size);

  }

};

/// 'Trivial' sequence serialization: Sequence is serialized as a uint64_t size

/// followed by a for-earch loop over the elements of the sequence to serialize

/// each of them.

template <typename SPSElementTagT, typename SequenceT>

class SPSSerializationTraits<SPSSequence<SPSElementTagT>, SequenceT,

                             std::enable_if_t<TrivialSPSSequenceSerialization<

                                 SPSElementTagT, SequenceT>::available>> {

public:

  static size_t size(const SequenceT &S) {

    size_t Size = SPSArgList<uint64_t>::size(static_cast<uint64_t>(S.size()));

    for (const auto &E : S)

      Size += SPSArgList<SPSElementTagT>::size(E);

    return Size;

  }

  static bool serialize(SPSOutputBuffer &OB, const SequenceT &S) {

    if (!SPSArgList<uint64_t>::serialize(OB, static_cast<uint64_t>(S.size())))

      return false;

    for (const auto &E : S)

      if (!SPSArgList<SPSElementTagT>::serialize(OB, E))

        return false;

    return true;

  }

  static bool deserialize(SPSInputBuffer &IB, SequenceT &S) {

    using TBSD = TrivialSPSSequenceDeserialization<SPSElementTagT, SequenceT>;

    uint64_t Size;

    if (!SPSArgList<uint64_t>::deserialize(IB, Size))

      return false;

    TBSD::reserve(S, Size);

    for (size_t I = 0; I != Size; ++I) {

      typename TBSD::element_type E;

      if (!SPSArgList<SPSElementTagT>::deserialize(IB, E))

        return false;

      if (!TBSD::append(S, std::move(E)))

        return false;

    }

    return true;

  }

};

/// SPSTuple serialization for std::tuple.

template <typename... SPSTagTs, typename... Ts>

class SPSSerializationTraits<SPSTuple<SPSTagTs...>, std::tuple<Ts...>> {

private:

  using TupleArgList = typename SPSTuple<SPSTagTs...>::AsArgList;

  using ArgIndices = std::make_index_sequence<sizeof...(Ts)>;

  template <std::size_t... I>

  static size_t size(const std::tuple<Ts...> &T, std::index_sequence<I...>) {

    return TupleArgList::size(std::get<I>(T)...);

  }

  template <std::size_t... I>

  static bool serialize(SPSOutputBuffer &OB, const std::tuple<Ts...> &T,

                        std::index_sequence<I...>) {

    return TupleArgList::serialize(OB, std::get<I>(T)...);

  }

  template <std::size_t... I>

  static bool deserialize(SPSInputBuffer &IB, std::tuple<Ts...> &T,

                          std::index_sequence<I...>) {

    return TupleArgList::deserialize(IB, std::get<I>(T)...);

  }

public:

  static size_t size(const std::tuple<Ts...> &T) {

    return size(T, ArgIndices{});

  }

  static bool serialize(SPSOutputBuffer &OB, const std::tuple<Ts...> &T) {

    return serialize(OB, T, ArgIndices{});

  }

  static bool deserialize(SPSInputBuffer &IB, std::tuple<Ts...> &T) {

    return deserialize(IB, T, ArgIndices{});

  }

};

/// SPSTuple serialization for std::pair.

template <typename SPSTagT1, typename SPSTagT2, typename T1, typename T2>

class SPSSerializationTraits<SPSTuple<SPSTagT1, SPSTagT2>, std::pair<T1, T2>> {

public:

  static size_t size(const std::pair<T1, T2> &P) {

    return SPSArgList<SPSTagT1>::size(P.first) +

           SPSArgList<SPSTagT2>::size(P.second);

  }

  static bool serialize(SPSOutputBuffer &OB, const std::pair<T1, T2> &P) {

    return SPSArgList<SPSTagT1>::serialize(OB, P.first) &&

           SPSArgList<SPSTagT2>::serialize(OB, P.second);

  }

  static bool deserialize(SPSInputBuffer &IB, std::pair<T1, T2> &P) {

    return SPSArgList<SPSTagT1>::deserialize(IB, P.first) &&

           SPSArgList<SPSTagT2>::deserialize(IB, P.second);

  }

};

/// SPSOptional serialization for std::optional.

template <typename SPSTagT, typename T>

class SPSSerializationTraits<SPSOptional<SPSTagT>, std::optional<T>> {

public:

  static size_t size(const std::optional<T> &Value) {

    size_t Size = SPSArgList<bool>::size(!!Value);

    if (Value)

      Size += SPSArgList<SPSTagT>::size(*Value);

    return Size;

  }

  static bool serialize(SPSOutputBuffer &OB, const std::optional<T> &Value) {

    if (!SPSArgList<bool>::serialize(OB, !!Value))

      return false;

    if (Value)

      return SPSArgList<SPSTagT>::serialize(OB, *Value);

    return true;

  }

  static bool deserialize(SPSInputBuffer &IB, std::optional<T> &Value) {

    bool HasValue;

    if (!SPSArgList<bool>::deserialize(IB, HasValue))

      return false;

    if (HasValue) {

      Value = T();

      return SPSArgList<SPSTagT>::deserialize(IB, *Value);

    } else

      Value = std::optional<T>();

    return true;

  }

};

/// Serialization for StringRefs.

///

/// Serialization is as for regular strings. Deserialization points directly

/// into the blob.

template <> class SPSSerializationTraits<SPSString, StringRef> {

public:

  static size_t size(const StringRef &S) {

    return SPSArgList<uint64_t>::size(static_cast<uint64_t>(S.size())) +

           S.size();

  }

  static bool serialize(SPSOutputBuffer &OB, StringRef S) {

    if (!SPSArgList<uint64_t>::serialize(OB, static_cast<uint64_t>(S.size())))

      return false;

    if (S.empty()) // Empty StringRef may have null data, so bail out early.

      return true;

    return OB.write(S.data(), S.size());

  }

  static bool deserialize(SPSInputBuffer &IB, StringRef &S) {

    const char *Data = nullptr;

    uint64_t Size;

    if (!SPSArgList<uint64_t>::deserialize(IB, Size))

      return false;

    Data = IB.data();

    if (!IB.skip(Size))

      return false;

    S = StringRef(Size ? Data : nullptr, Size);

    return true;

  }

};

/// Serialization for StringMap<ValueT>s.

template <typename SPSValueT, typename ValueT>

class SPSSerializationTraits<SPSSequence<SPSTuple<SPSString, SPSValueT>>,

                             StringMap<ValueT>> {

public:

  static size_t size(const StringMap<ValueT> &M) {

    size_t Sz = SPSArgList<uint64_t>::size(static_cast<uint64_t>(M.size()));

    for (auto &E : M)

      Sz += SPSArgList<SPSString, SPSValueT>::size(E.first(), E.second);

    return Sz;

  }

  static bool serialize(SPSOutputBuffer &OB, const StringMap<ValueT> &M) {

    if (!SPSArgList<uint64_t>::serialize(OB, static_cast<uint64_t>(M.size())))

      return false;

    for (auto &E : M)

      if (!SPSArgList<SPSString, SPSValueT>::serialize(OB, E.first(), E.second))

        return false;

    return true;

  }

  static bool deserialize(SPSInputBuffer &IB, StringMap<ValueT> &M) {

    uint64_t Size;

    assert(M.empty() && "M already contains elements");

    if (!SPSArgList<uint64_t>::deserialize(IB, Size))

      return false;

    while (Size--) {

      StringRef S;

      ValueT V;

      if (!SPSArgList<SPSString, SPSValueT>::deserialize(IB, S, V))

        return false;

      if (!M.insert(std::make_pair(S, V)).second)

        return false;

    }

    return true;

  }

};

/// SPS tag type for errors.

class SPSError;

/// SPS tag type for expecteds, which are either a T or a string representing

/// an error.

template <typename SPSTagT> class SPSExpected;

namespace detail {

/// Helper type for serializing Errors.

///

/// llvm::Errors are move-only, and not inspectable except by consuming them.

/// This makes them unsuitable for direct serialization via

/// SPSSerializationTraits, which needs to inspect values twice (once to

/// determine the amount of space to reserve, and then again to serialize).

///

/// The SPSSerializableError type is a helper that can be

/// constructed from an llvm::Error, but inspected more than once.

struct SPSSerializableError {

  bool HasError = false;

  std::string ErrMsg;

};

/// Helper type for serializing Expected<T>s.

///

/// See SPSSerializableError for more details.

///

// FIXME: Use std::variant for storage once we have c++17.

template <typename T> struct SPSSerializableExpected {

  bool HasValue = false;

  T Value{};

  std::string ErrMsg;

};

inline SPSSerializableError toSPSSerializable(Error Err) {

  if (Err)

    return {true, toString(std::move(Err))};

  return {false, {}};

}

inline Error fromSPSSerializable(SPSSerializableError BSE) {

  if (BSE.HasError)

    return make_error<StringError>(BSE.ErrMsg, inconvertibleErrorCode());

  return Error::success();

}

template <typename T>

SPSSerializableExpected<T> toSPSSerializable(Expected<T> E) {

  if (E)

    return {true, std::move(*E), {}};

  else

    return {false, T(), toString(E.takeError())};

}

template <typename T>

Expected<T> fromSPSSerializable(SPSSerializableExpected<T> BSE) {

  if (BSE.HasValue)

    return std::move(BSE.Value);

  else

    return make_error<StringError>(BSE.ErrMsg, inconvertibleErrorCode());

}

} // end namespace detail

/// Serialize to a SPSError from a detail::SPSSerializableError.

template <>

class SPSSerializationTraits<SPSError, detail::SPSSerializableError> {

public:

  static size_t size(const detail::SPSSerializableError &BSE) {

    size_t Size = SPSArgList<bool>::size(BSE.HasError);

    if (BSE.HasError)

      Size += SPSArgList<SPSString>::size(BSE.ErrMsg);

    return Size;

  }

  static bool serialize(SPSOutputBuffer &OB,

                        const detail::SPSSerializableError &BSE) {

    if (!SPSArgList<bool>::serialize(OB, BSE.HasError))

      return false;

    if (BSE.HasError)

      if (!SPSArgList<SPSString>::serialize(OB, BSE.ErrMsg))

        return false;

    return true;

  }

  static bool deserialize(SPSInputBuffer &IB,

                          detail::SPSSerializableError &BSE) {

    if (!SPSArgList<bool>::deserialize(IB, BSE.HasError))

      return false;

    if (!BSE.HasError)

      return true;

    return SPSArgList<SPSString>::deserialize(IB, BSE.ErrMsg);

  }

};

/// Serialize to a SPSExpected<SPSTagT> from a

/// detail::SPSSerializableExpected<T>.

template <typename SPSTagT, typename T>

class SPSSerializationTraits<SPSExpected<SPSTagT>,

                             detail::SPSSerializableExpected<T>> {

public:

  static size_t size(const detail::SPSSerializableExpected<T> &BSE) {

    size_t Size = SPSArgList<bool>::size(BSE.HasValue);

    if (BSE.HasValue)

      Size += SPSArgList<SPSTagT>::size(BSE.Value);

    else

      Size += SPSArgList<SPSString>::size(BSE.ErrMsg);

    return Size;

  }

  static bool serialize(SPSOutputBuffer &OB,

                        const detail::SPSSerializableExpected<T> &BSE) {

    if (!SPSArgList<bool>::serialize(OB, BSE.HasValue))

      return false;

    if (BSE.HasValue)

      return SPSArgList<SPSTagT>::serialize(OB, BSE.Value);

    return SPSArgList<SPSString>::serialize(OB, BSE.ErrMsg);

  }

  static bool deserialize(SPSInputBuffer &IB,

                          detail::SPSSerializableExpected<T> &BSE) {

    if (!SPSArgList<bool>::deserialize(IB, BSE.HasValue))

      return false;

    if (BSE.HasValue)

      return SPSArgList<SPSTagT>::deserialize(IB, BSE.Value);

    return SPSArgList<SPSString>::deserialize(IB, BSE.ErrMsg);

  }

};

/// Serialize to a SPSExpected<SPSTagT> from a detail::SPSSerializableError.

template <typename SPSTagT>

class SPSSerializationTraits<SPSExpected<SPSTagT>,

                             detail::SPSSerializableError> {

public:

  static size_t size(const detail::SPSSerializableError &BSE) {

    assert(BSE.HasError && "Cannot serialize expected from a success value");

    return SPSArgList<bool>::size(false) +

           SPSArgList<SPSString>::size(BSE.ErrMsg);