compiler-rt/lib/orc/simple_packed_serialization.h

   1 //===--- simple_packed_serialization.h - simple serialization ---*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file is a part of the ORC runtime support library.
  10 //
  11 // The behavior of the utilities in this header must be synchronized with the
  12 // behavior of the utilities in
  13 // llvm/ExecutionEngine/Orc/Shared/WrapperFunctionUtils.h.
  14 //
  15 // The Simple Packed Serialization (SPS) utilities are used to generate
  16 // argument and return buffers for wrapper functions using the following
  17 // serialization scheme:
  18 //
  19 // Primitives:
  20 //   bool, char, int8_t, uint8_t -- Two's complement 8-bit (0=false, 1=true)
  21 //   int16_t, uint16_t           -- Two's complement 16-bit little endian
  22 //   int32_t, uint32_t           -- Two's complement 32-bit little endian
  23 //   int64_t, int64_t            -- Two's complement 64-bit little endian
  24 //
  25 // Sequence<T>:
  26 //   Serialized as the sequence length (as a uint64_t) followed by the
  27 //   serialization of each of the elements without padding.
  28 //
  29 // Tuple<T1, ..., TN>:
  30 //   Serialized as each of the element types from T1 to TN without padding.
  31 //
  32 //===----------------------------------------------------------------------===//
  33
  34 #ifndef ORC_RT_SIMPLE_PACKED_SERIALIZATION_H
  35 #define ORC_RT_SIMPLE_PACKED_SERIALIZATION_H
  36
  37 #include "adt.h"
  38 #include "endianness.h"
  39 #include "error.h"
  40 #include "stl_extras.h"
  41
  42 #include <optional>
  43 #include <string>
  44 #include <string_view>
  45 #include <tuple>
  46 #include <type_traits>
  47 #include <unordered_map>
  48 #include <utility>
  49 #include <vector>
  50
  51 namespace __orc_rt {
  52
  53 /// Output char buffer with overflow check.
  54 class SPSOutputBuffer {
  55 public:
  56   SPSOutputBuffer(char *Buffer, size_t Remaining)
  57       : Buffer(Buffer), Remaining(Remaining) {}
  58   bool write(const char *Data, size_t Size) {
  59     if (Size > Remaining)
  60       return false;
  61     memcpy(Buffer, Data, Size);
  62     Buffer += Size;
  63     Remaining -= Size;
  64     return true;
  65   }
  66
  67 private:
  68   char *Buffer = nullptr;
  69   size_t Remaining = 0;
  70 };
  71
  72 /// Input char buffer with underflow check.
  73 class SPSInputBuffer {
  74 public:
  75   SPSInputBuffer() = default;
  76   SPSInputBuffer(const char *Buffer, size_t Remaining)
  77       : Buffer(Buffer), Remaining(Remaining) {}
  78   bool read(char *Data, size_t Size) {
  79     if (Size > Remaining)
  80       return false;
  81     memcpy(Data, Buffer, Size);
  82     Buffer += Size;
  83     Remaining -= Size;
  84     return true;
  85   }
  86
  87   const char *data() const { return Buffer; }
  88   bool skip(size_t Size) {
  89     if (Size > Remaining)
  90       return false;
  91     Buffer += Size;
  92     Remaining -= Size;
  93     return true;
  94   }
  95
  96 private:
  97   const char *Buffer = nullptr;
  98   size_t Remaining = 0;
  99 };
 100
 101 /// Specialize to describe how to serialize/deserialize to/from the given
 102 /// concrete type.
 103 template <typename SPSTagT, typename ConcreteT, typename _ = void>
 104 class SPSSerializationTraits;
 105
 106 /// A utility class for serializing to a blob from a variadic list.
 107 template <typename... ArgTs> class SPSArgList;
 108
 109 // Empty list specialization for SPSArgList.
 110 template <> class SPSArgList<> {
 111 public:
 112   static size_t size() { return 0; }
 113
 114   static bool serialize(SPSOutputBuffer &OB) { return true; }
 115   static bool deserialize(SPSInputBuffer &IB) { return true; }
 116 };
 117
 118 // Non-empty list specialization for SPSArgList.
 119 template <typename SPSTagT, typename... SPSTagTs>
 120 class SPSArgList<SPSTagT, SPSTagTs...> {
 121 public:
 122   template <typename ArgT, typename... ArgTs>
 123   static size_t size(const ArgT &Arg, const ArgTs &...Args) {
 124     return SPSSerializationTraits<SPSTagT, ArgT>::size(Arg) +
 125            SPSArgList<SPSTagTs...>::size(Args...);
 126   }
 127
 128   template <typename ArgT, typename... ArgTs>
 129   static bool serialize(SPSOutputBuffer &OB, const ArgT &Arg,
 130                         const ArgTs &...Args) {
 131     return SPSSerializationTraits<SPSTagT, ArgT>::serialize(OB, Arg) &&
 132            SPSArgList<SPSTagTs...>::serialize(OB, Args...);
 133   }
 134
 135   template <typename ArgT, typename... ArgTs>
 136   static bool deserialize(SPSInputBuffer &IB, ArgT &Arg, ArgTs &...Args) {
 137     return SPSSerializationTraits<SPSTagT, ArgT>::deserialize(IB, Arg) &&
 138            SPSArgList<SPSTagTs...>::deserialize(IB, Args...);
 139   }
 140 };
 141
 142 /// SPS serialization for integral types, bool, and char.
 143 template <typename SPSTagT>
 144 class SPSSerializationTraits<
 145     SPSTagT, SPSTagT,
 146     std::enable_if_t<std::is_same<SPSTagT, bool>::value ||
 147                      std::is_same<SPSTagT, char>::value ||
 148                      std::is_same<SPSTagT, int8_t>::value ||
 149                      std::is_same<SPSTagT, int16_t>::value ||
 150                      std::is_same<SPSTagT, int32_t>::value ||
 151                      std::is_same<SPSTagT, int64_t>::value ||
 152                      std::is_same<SPSTagT, uint8_t>::value ||
 153                      std::is_same<SPSTagT, uint16_t>::value ||
 154                      std::is_same<SPSTagT, uint32_t>::value ||
 155                      std::is_same<SPSTagT, uint64_t>::value>> {
 156 public:
 157   static size_t size(const SPSTagT &Value) { return sizeof(SPSTagT); }
 158
 159   static bool serialize(SPSOutputBuffer &OB, const SPSTagT &Value) {
 160     SPSTagT Tmp = Value;
 161     if (IsBigEndianHost)
 162       swapByteOrder(Tmp);
 163     return OB.write(reinterpret_cast<const char *>(&Tmp), sizeof(Tmp));
 164   }
 165
 166   static bool deserialize(SPSInputBuffer &IB, SPSTagT &Value) {
 167     SPSTagT Tmp;
 168     if (!IB.read(reinterpret_cast<char *>(&Tmp), sizeof(Tmp)))
 169       return false;
 170     if (IsBigEndianHost)
 171       swapByteOrder(Tmp);
 172     Value = Tmp;
 173     return true;
 174   }
 175 };
 176
 177 /// Any empty placeholder suitable as a substitute for void when deserializing
 178 class SPSEmpty {};
 179
 180 /// Represents an address in the executor.
 181 class SPSExecutorAddr {};
 182
 183 /// SPS tag type for tuples.
 184 ///
 185 /// A blob tuple should be serialized by serializing each of the elements in
 186 /// sequence.
 187 template <typename... SPSTagTs> class SPSTuple {
 188 public:
 189   /// Convenience typedef of the corresponding arg list.
 190   typedef SPSArgList<SPSTagTs...> AsArgList;
 191 };
 192
 193 /// SPS tag type for optionals.
 194 ///
 195 /// SPSOptionals should be serialized as a bool with true indicating that an
 196 /// SPSTagT value is present, and false indicating that there is no value.
 197 /// If the boolean is true then the serialized SPSTagT will follow immediately
 198 /// after it.
 199 template <typename SPSTagT> class SPSOptional {};
 200
 201 /// SPS tag type for sequences.
 202 ///
 203 /// SPSSequences should be serialized as a uint64_t sequence length,
 204 /// followed by the serialization of each of the elements.
 205 template <typename SPSElementTagT> class SPSSequence;
 206
 207 /// SPS tag type for strings, which are equivalent to sequences of chars.
 208 using SPSString = SPSSequence<char>;
 209
 210 /// SPS tag type for maps.
 211 ///
 212 /// SPS maps are just sequences of (Key, Value) tuples.
 213 template <typename SPSTagT1, typename SPSTagT2>
 214 using SPSMap = SPSSequence<SPSTuple<SPSTagT1, SPSTagT2>>;
 215
 216 /// Serialization for SPSEmpty type.
 217 template <> class SPSSerializationTraits<SPSEmpty, SPSEmpty> {
 218 public:
 219   static size_t size(const SPSEmpty &EP) { return 0; }
 220   static bool serialize(SPSOutputBuffer &OB, const SPSEmpty &BE) {
 221     return true;
 222   }
 223   static bool deserialize(SPSInputBuffer &IB, SPSEmpty &BE) { return true; }
 224 };
 225
 226 /// Specialize this to implement 'trivial' sequence serialization for
 227 /// a concrete sequence type.
 228 ///
 229 /// Trivial sequence serialization uses the sequence's 'size' member to get the
 230 /// length of the sequence, and uses a range-based for loop to iterate over the
 231 /// elements.
 232 ///
 233 /// Specializing this template class means that you do not need to provide a
 234 /// specialization of SPSSerializationTraits for your type.
 235 template <typename SPSElementTagT, typename ConcreteSequenceT>
 236 class TrivialSPSSequenceSerialization {
 237 public:
 238   static constexpr bool available = false;
 239 };
 240
 241 /// Specialize this to implement 'trivial' sequence deserialization for
 242 /// a concrete sequence type.
 243 ///
 244 /// Trivial deserialization calls a static 'reserve(SequenceT&)' method on your
 245 /// specialization (you must implement this) to reserve space, and then calls
 246 /// a static 'append(SequenceT&, ElementT&) method to append each of the
 247 /// deserialized elements.
 248 ///
 249 /// Specializing this template class means that you do not need to provide a
 250 /// specialization of SPSSerializationTraits for your type.
 251 template <typename SPSElementTagT, typename ConcreteSequenceT>
 252 class TrivialSPSSequenceDeserialization {
 253 public:
 254   static constexpr bool available = false;
 255 };
 256
 257 /// Trivial std::string -> SPSSequence<char> serialization.
 258 template <> class TrivialSPSSequenceSerialization<char, std::string> {
 259 public:
 260   static constexpr bool available = true;
 261 };
 262
 263 /// Trivial SPSSequence<char> -> std::string deserialization.
 264 template <> class TrivialSPSSequenceDeserialization<char, std::string> {
 265 public:
 266   static constexpr bool available = true;
 267
 268   using element_type = char;
 269
 270   static void reserve(std::string &S, uint64_t Size) { S.reserve(Size); }
 271   static bool append(std::string &S, char C) {
 272     S.push_back(C);
 273     return true;
 274   }
 275 };
 276
 277 /// Trivial std::vector<T> -> SPSSequence<SPSElementTagT> serialization.
 278 template <typename SPSElementTagT, typename T>
 279 class TrivialSPSSequenceSerialization<SPSElementTagT, std::vector<T>> {
 280 public:
 281   static constexpr bool available = true;
 282 };
 283
 284 /// Trivial SPSSequence<SPSElementTagT> -> std::vector<T> deserialization.
 285 template <typename SPSElementTagT, typename T>
 286 class TrivialSPSSequenceDeserialization<SPSElementTagT, std::vector<T>> {
 287 public:
 288   static constexpr bool available = true;
 289
 290   using element_type = typename std::vector<T>::value_type;
 291
 292   static void reserve(std::vector<T> &V, uint64_t Size) { V.reserve(Size); }
 293   static bool append(std::vector<T> &V, T E) {
 294     V.push_back(std::move(E));
 295     return true;
 296   }
 297 };
 298
 299 /// Trivial std::unordered_map<K, V> -> SPSSequence<SPSTuple<SPSKey, SPSValue>>
 300 /// serialization.
 301 template <typename SPSKeyTagT, typename SPSValueTagT, typename K, typename V>
 302 class TrivialSPSSequenceSerialization<SPSTuple<SPSKeyTagT, SPSValueTagT>,
 303                                       std::unordered_map<K, V>> {
 304 public:
 305   static constexpr bool available = true;
 306 };
 307
 308 /// Trivial SPSSequence<SPSTuple<SPSKey, SPSValue>> -> std::unordered_map<K, V>
 309 /// deserialization.
 310 template <typename SPSKeyTagT, typename SPSValueTagT, typename K, typename V>
 311 class TrivialSPSSequenceDeserialization<SPSTuple<SPSKeyTagT, SPSValueTagT>,
 312                                         std::unordered_map<K, V>> {
 313 public:
 314   static constexpr bool available = true;
 315
 316   using element_type = std::pair<K, V>;
 317
 318   static void reserve(std::unordered_map<K, V> &M, uint64_t Size) {
 319     M.reserve(Size);
 320   }
 321   static bool append(std::unordered_map<K, V> &M, element_type E) {
 322     return M.insert(std::move(E)).second;
 323   }
 324 };
 325
 326 /// 'Trivial' sequence serialization: Sequence is serialized as a uint64_t size
 327 /// followed by a for-earch loop over the elements of the sequence to serialize
 328 /// each of them.
 329 template <typename SPSElementTagT, typename SequenceT>
 330 class SPSSerializationTraits<SPSSequence<SPSElementTagT>, SequenceT,
 331                              std::enable_if_t<TrivialSPSSequenceSerialization<
 332                                  SPSElementTagT, SequenceT>::available>> {
 333 public:
 334   static size_t size(const SequenceT &S) {
 335     size_t Size = SPSArgList<uint64_t>::size(static_cast<uint64_t>(S.size()));
 336     for (const auto &E : S)
 337       Size += SPSArgList<SPSElementTagT>::size(E);
 338     return Size;
 339   }
 340
 341   static bool serialize(SPSOutputBuffer &OB, const SequenceT &S) {
 342     if (!SPSArgList<uint64_t>::serialize(OB, static_cast<uint64_t>(S.size())))
 343       return false;
 344     for (const auto &E : S)
 345       if (!SPSArgList<SPSElementTagT>::serialize(OB, E))
 346         return false;
 347     return true;
 348   }
 349
 350   static bool deserialize(SPSInputBuffer &IB, SequenceT &S) {
 351     using TBSD = TrivialSPSSequenceDeserialization<SPSElementTagT, SequenceT>;
 352     uint64_t Size;
 353     if (!SPSArgList<uint64_t>::deserialize(IB, Size))
 354       return false;
 355     TBSD::reserve(S, Size);
 356     for (size_t I = 0; I != Size; ++I) {
 357       typename TBSD::element_type E;
 358       if (!SPSArgList<SPSElementTagT>::deserialize(IB, E))
 359         return false;
 360       if (!TBSD::append(S, std::move(E)))
 361         return false;
 362     }
 363     return true;
 364   }
 365 };
 366
 367 /// Trivial serialization / deserialization for span<char>
 368 template <> class SPSSerializationTraits<SPSSequence<char>, span<const char>> {
 369 public:
 370   static size_t size(const span<const char> &S) {
 371     return SPSArgList<uint64_t>::size(static_cast<uint64_t>(S.size())) +
 372            S.size();
 373   }
 374   static bool serialize(SPSOutputBuffer &OB, const span<const char> &S) {
 375     if (!SPSArgList<uint64_t>::serialize(OB, static_cast<uint64_t>(S.size())))
 376       return false;
 377     return OB.write(S.data(), S.size());
 378   }
 379   static bool deserialize(SPSInputBuffer &IB, span<const char> &S) {
 380     uint64_t Size;
 381     if (!SPSArgList<uint64_t>::deserialize(IB, Size))
 382       return false;
 383     S = span<const char>(IB.data(), Size);
 384     return IB.skip(Size);
 385   }
 386 };
 387
 388 /// SPSTuple serialization for std::pair.
 389 template <typename SPSTagT1, typename SPSTagT2, typename T1, typename T2>
 390 class SPSSerializationTraits<SPSTuple<SPSTagT1, SPSTagT2>, std::pair<T1, T2>> {
 391 public:
 392   static size_t size(const std::pair<T1, T2> &P) {
 393     return SPSArgList<SPSTagT1>::size(P.first) +
 394            SPSArgList<SPSTagT2>::size(P.second);
 395   }
 396
 397   static bool serialize(SPSOutputBuffer &OB, const std::pair<T1, T2> &P) {
 398     return SPSArgList<SPSTagT1>::serialize(OB, P.first) &&
 399            SPSArgList<SPSTagT2>::serialize(OB, P.second);
 400   }
 401
 402   static bool deserialize(SPSInputBuffer &IB, std::pair<T1, T2> &P) {
 403     return SPSArgList<SPSTagT1>::deserialize(IB, P.first) &&
 404            SPSArgList<SPSTagT2>::deserialize(IB, P.second);
 405   }
 406 };
 407
 408 /// SPSOptional serialization for std::optional.
 409 template <typename SPSTagT, typename T>
 410 class SPSSerializationTraits<SPSOptional<SPSTagT>, std::optional<T>> {
 411 public:
 412   static size_t size(const std::optional<T> &Value) {
 413     size_t Size = SPSArgList<bool>::size(!!Value);
 414     if (Value)
 415       Size += SPSArgList<SPSTagT>::size(*Value);
 416     return Size;
 417   }
 418
 419   static bool serialize(SPSOutputBuffer &OB, const std::optional<T> &Value) {
 420     if (!SPSArgList<bool>::serialize(OB, !!Value))
 421       return false;
 422     if (Value)
 423       return SPSArgList<SPSTagT>::serialize(OB, *Value);
 424     return true;
 425   }
 426
 427   static bool deserialize(SPSInputBuffer &IB, std::optional<T> &Value) {
 428     bool HasValue;
 429     if (!SPSArgList<bool>::deserialize(IB, HasValue))
 430       return false;
 431     if (HasValue) {
 432       Value = T();
 433       return SPSArgList<SPSTagT>::deserialize(IB, *Value);
 434     } else
 435       Value = std::optional<T>();
 436     return true;
 437   }
 438 };
 439
 440 /// Serialization for string_views.
 441 ///
 442 /// Serialization is as for regular strings. Deserialization points directly
 443 /// into the blob.
 444 template <> class SPSSerializationTraits<SPSString, std::string_view> {
 445 public:
 446   static size_t size(const std::string_view &S) {
 447     return SPSArgList<uint64_t>::size(static_cast<uint64_t>(S.size())) +
 448            S.size();
 449   }
 450
 451   static bool serialize(SPSOutputBuffer &OB, const std::string_view &S) {
 452     if (!SPSArgList<uint64_t>::serialize(OB, static_cast<uint64_t>(S.size())))
 453       return false;
 454     return OB.write(S.data(), S.size());
 455   }
 456
 457   static bool deserialize(SPSInputBuffer &IB, std::string_view &S) {
 458     const char *Data = nullptr;
 459     uint64_t Size;
 460     if (!SPSArgList<uint64_t>::deserialize(IB, Size))
 461       return false;
 462     if (Size > std::numeric_limits<size_t>::max())
 463       return false;
 464     Data = IB.data();
 465     if (!IB.skip(Size))
 466       return false;
 467     S = {Data, static_cast<size_t>(Size)};
 468     return true;
 469   }
 470 };
 471
 472 /// SPS tag type for errors.
 473 class SPSError;
 474
 475 /// SPS tag type for expecteds, which are either a T or a string representing
 476 /// an error.
 477 template <typename SPSTagT> class SPSExpected;
 478
 479 namespace detail {
 480
 481 /// Helper type for serializing Errors.
 482 ///
 483 /// llvm::Errors are move-only, and not inspectable except by consuming them.
 484 /// This makes them unsuitable for direct serialization via
 485 /// SPSSerializationTraits, which needs to inspect values twice (once to
 486 /// determine the amount of space to reserve, and then again to serialize).
 487 ///
 488 /// The SPSSerializableError type is a helper that can be
 489 /// constructed from an llvm::Error, but inspected more than once.
 490 struct SPSSerializableError {
 491   bool HasError = false;
 492   std::string ErrMsg;
 493 };
 494
 495 /// Helper type for serializing Expected<T>s.
 496 ///
 497 /// See SPSSerializableError for more details.
 498 ///
 499 // FIXME: Use std::variant for storage once we have c++17.
 500 template <typename T> struct SPSSerializableExpected {
 501   bool HasValue = false;
 502   T Value{};
 503   std::string ErrMsg;
 504 };
 505
 506 inline SPSSerializableError toSPSSerializable(Error Err) {
 507   if (Err)
 508     return {true, toString(std::move(Err))};
 509   return {false, {}};
 510 }
 511
 512 inline Error fromSPSSerializable(SPSSerializableError BSE) {
 513   if (BSE.HasError)
 514     return make_error<StringError>(BSE.ErrMsg);
 515   return Error::success();
 516 }
 517
 518 template <typename T>
 519 SPSSerializableExpected<T> toSPSSerializable(Expected<T> E) {
 520   if (E)
 521     return {true, std::move(*E), {}};
 522   else
 523     return {false, {}, toString(E.takeError())};
 524 }
 525
 526 template <typename T>
 527 Expected<T> fromSPSSerializable(SPSSerializableExpected<T> BSE) {
 528   if (BSE.HasValue)
 529     return std::move(BSE.Value);
 530   else
 531     return make_error<StringError>(BSE.ErrMsg);
 532 }
 533
 534 } // end namespace detail
 535
 536 /// Serialize to a SPSError from a detail::SPSSerializableError.
 537 template <>
 538 class SPSSerializationTraits<SPSError, detail::SPSSerializableError> {
 539 public:
 540   static size_t size(const detail::SPSSerializableError &BSE) {
 541     size_t Size = SPSArgList<bool>::size(BSE.HasError);
 542     if (BSE.HasError)
 543       Size += SPSArgList<SPSString>::size(BSE.ErrMsg);
 544     return Size;
 545   }
 546
 547   static bool serialize(SPSOutputBuffer &OB,
 548                         const detail::SPSSerializableError &BSE) {
 549     if (!SPSArgList<bool>::serialize(OB, BSE.HasError))
 550       return false;
 551     if (BSE.HasError)
 552       if (!SPSArgList<SPSString>::serialize(OB, BSE.ErrMsg))
 553         return false;
 554     return true;
 555   }
 556
 557   static bool deserialize(SPSInputBuffer &IB,
 558                           detail::SPSSerializableError &BSE) {
 559     if (!SPSArgList<bool>::deserialize(IB, BSE.HasError))
 560       return false;
 561
 562     if (!BSE.HasError)
 563       return true;
 564
 565     return SPSArgList<SPSString>::deserialize(IB, BSE.ErrMsg);
 566   }
 567 };
 568
 569 /// Serialize to a SPSExpected<SPSTagT> from a
 570 /// detail::SPSSerializableExpected<T>.
 571 template <typename SPSTagT, typename T>
 572 class SPSSerializationTraits<SPSExpected<SPSTagT>,
 573                              detail::SPSSerializableExpected<T>> {
 574 public:
 575   static size_t size(const detail::SPSSerializableExpected<T> &BSE) {
 576     size_t Size = SPSArgList<bool>::size(BSE.HasValue);
 577     if (BSE.HasValue)
 578       Size += SPSArgList<SPSTagT>::size(BSE.Value);
 579     else
 580       Size += SPSArgList<SPSString>::size(BSE.ErrMsg);
 581     return Size;
 582   }
 583
 584   static bool serialize(SPSOutputBuffer &OB,
 585                         const detail::SPSSerializableExpected<T> &BSE) {
 586     if (!SPSArgList<bool>::serialize(OB, BSE.HasValue))
 587       return false;
 588
 589     if (BSE.HasValue)
 590       return SPSArgList<SPSTagT>::serialize(OB, BSE.Value);
 591
 592     return SPSArgList<SPSString>::serialize(OB, BSE.ErrMsg);
 593   }
 594
 595   static bool deserialize(SPSInputBuffer &IB,
 596                           detail::SPSSerializableExpected<T> &BSE) {
 597     if (!SPSArgList<bool>::deserialize(IB, BSE.HasValue))
 598       return false;
 599
 600     if (BSE.HasValue)
 601       return SPSArgList<SPSTagT>::deserialize(IB, BSE.Value);
 602
 603     return SPSArgList<SPSString>::deserialize(IB, BSE.ErrMsg);
 604   }
 605 };
 606
 607 /// Serialize to a SPSExpected<SPSTagT> from a detail::SPSSerializableError.
 608 template <typename SPSTagT>
 609 class SPSSerializationTraits<SPSExpected<SPSTagT>,
 610                              detail::SPSSerializableError> {
 611 public:
 612   static size_t size(const detail::SPSSerializableError &BSE) {
 613     assert(BSE.HasError && "Cannot serialize expected from a success value");
 614     return SPSArgList<bool>::size(false) +
 615            SPSArgList<SPSString>::size(BSE.ErrMsg);
 616   }
 617
 618   static bool serialize(SPSOutputBuffer &OB,
 619                         const detail::SPSSerializableError &BSE) {
 620     assert(BSE.HasError && "Cannot serialize expected from a success value");
 621     if (!SPSArgList<bool>::serialize(OB, false))
 622       return false;
 623     return SPSArgList<SPSString>::serialize(OB, BSE.ErrMsg);
 624   }
 625 };
 626
 627 /// Serialize to a SPSExpected<SPSTagT> from a T.
 628 template <typename SPSTagT, typename T>
 629 class SPSSerializationTraits<SPSExpected<SPSTagT>, T> {
 630 public:
 631   static size_t size(const T &Value) {
 632     return SPSArgList<bool>::size(true) + SPSArgList<SPSTagT>::size(Value);
 633   }
 634
 635   static bool serialize(SPSOutputBuffer &OB, const T &Value) {
 636     if (!SPSArgList<bool>::serialize(OB, true))
 637       return false;
 638     return SPSArgList<SPSTagT>::serialize(Value);
 639   }
 640 };
 641
 642 } // end namespace __orc_rt
 643
 644 #endif // ORC_RT_SIMPLE_PACKED_SERIALIZATION_H