schema-loader.c++ 46.5 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
// Copyright (c) 2013, Kenton Varda <temporal@gmail.com>
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Kenton Varda's avatar
Kenton Varda committed
24
#define CAPNP_PRIVATE
25 26 27 28 29
#include "schema-loader.h"
#include <unordered_map>
#include <map>
#include "message.h"
#include "arena.h"
Kenton Varda's avatar
Kenton Varda committed
30
#include <kj/debug.h>
31
#include <kj/exception.h>
32
#include <kj/arena.h>
33

34
namespace capnp {
35

36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
class SchemaLoader::InitializerImpl: public _::RawSchema::Initializer {
public:
  inline explicit InitializerImpl(const SchemaLoader& loader): loader(loader), callback(nullptr) {}
  inline InitializerImpl(const SchemaLoader& loader, const LazyLoadCallback& callback)
      : loader(loader), callback(callback) {}

  inline kj::Maybe<const LazyLoadCallback&> getCallback() const { return callback; }

  void init(const _::RawSchema* schema) const override;

  inline bool operator==(decltype(nullptr)) const { return callback == nullptr; }

private:
  const SchemaLoader& loader;
  kj::Maybe<const LazyLoadCallback&> callback;
};

53 54
class SchemaLoader::Impl {
public:
55 56 57 58 59
  inline explicit Impl(const SchemaLoader& loader): initializer(loader) {}
  inline Impl(const SchemaLoader& loader, const LazyLoadCallback& callback)
      : initializer(loader, callback) {}

  _::RawSchema* load(const schema::Node::Reader& reader, bool isPlaceholder);
60

61
  _::RawSchema* loadNative(const _::RawSchema* nativeSchema);
62

63
  _::RawSchema* loadEmpty(uint64_t id, kj::StringPtr name, schema::Node::Body::Which kind);
64 65
  // Create a dummy empty schema of the given kind for the given id and load it.

66 67 68 69 70 71
  struct TryGetResult {
    _::RawSchema* schema;
    kj::Maybe<const LazyLoadCallback&> callback;
  };

  TryGetResult tryGet(uint64_t typeId) const;
72
  kj::Array<Schema> getAllLoaded() const;
73

74
  kj::Arena arena;
75 76

private:
77
  std::unordered_map<uint64_t, _::RawSchema*> schemas;
78 79

  InitializerImpl initializer;
80 81 82 83 84 85 86 87
};

// =======================================================================================

class SchemaLoader::Validator {
public:
  Validator(SchemaLoader::Impl& loader): loader(loader) {}

88
  bool validate(const schema::Node::Reader& node) {
89 90 91 92
    isValid = true;
    nodeName = node.getDisplayName();
    dependencies.clear();

93
    KJ_CONTEXT("validating schema node", nodeName, (uint)node.getBody().which());
94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119

    switch (node.getBody().which()) {
      case schema::Node::Body::FILE_NODE:
        validate(node.getBody().getFileNode());
        break;
      case schema::Node::Body::STRUCT_NODE:
        validate(node.getBody().getStructNode());
        break;
      case schema::Node::Body::ENUM_NODE:
        validate(node.getBody().getEnumNode());
        break;
      case schema::Node::Body::INTERFACE_NODE:
        validate(node.getBody().getInterfaceNode());
        break;
      case schema::Node::Body::CONST_NODE:
        validate(node.getBody().getConstNode());
        break;
      case schema::Node::Body::ANNOTATION_NODE:
        validate(node.getBody().getAnnotationNode());
        break;
    }

    // We accept and pass through node types we don't recognize.
    return isValid;
  }

120
  const _::RawSchema** makeDependencyArray(uint32_t* count) {
121
    *count = dependencies.size();
122 123
    kj::ArrayPtr<const _::RawSchema*> result =
        loader.arena.allocateArray<const _::RawSchema*>(*count);
124 125 126 127
    uint pos = 0;
    for (auto& dep: dependencies) {
      result[pos++] = dep.second;
    }
128
    KJ_DASSERT(pos == *count);
129
    return result.begin();
130 131
  }

132
  const _::RawSchema::MemberInfo* makeMemberInfoArray(uint32_t* count) {
133
    *count = members.size();
134 135
    kj::ArrayPtr<_::RawSchema::MemberInfo> result =
        loader.arena.allocateArray<_::RawSchema::MemberInfo>(*count);
136 137
    uint pos = 0;
    for (auto& member: members) {
138 139
      result[pos++] = {kj::implicitCast<uint16_t>(member.first.first),
                       kj::implicitCast<uint16_t>(member.second)};
140
    }
141
    KJ_DASSERT(pos == *count);
142
    return result.begin();
143 144 145 146 147 148
  }

private:
  SchemaLoader::Impl& loader;
  Text::Reader nodeName;
  bool isValid;
149
  std::map<uint64_t, _::RawSchema*> dependencies;
150 151 152 153 154

  // Maps (unionIndex, name) -> index for each member.
  std::map<std::pair<uint, Text::Reader>, uint> members;

#define VALIDATE_SCHEMA(condition, ...) \
155
  KJ_REQUIRE(condition, ##__VA_ARGS__) { isValid = false; return; }
156
#define FAIL_VALIDATE_SCHEMA(...) \
157
  KJ_FAIL_REQUIRE(__VA_ARGS__) { isValid = false; return; }
158

159
  void validate(const schema::FileNode::Reader& fileNode) {
160 161 162
    // Nothing needs validation.
  }

163
  void validate(const schema::StructNode::Reader& structNode) {
164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
    uint dataSizeInBits;
    uint pointerCount;

    switch (structNode.getPreferredListEncoding()) {
      case schema::ElementSize::EMPTY:
        dataSizeInBits = 0;
        pointerCount = 0;
        break;
      case schema::ElementSize::BIT:
        dataSizeInBits = 1;
        pointerCount = 0;
        break;
      case schema::ElementSize::BYTE:
        dataSizeInBits = 8;
        pointerCount = 0;
        break;
      case schema::ElementSize::TWO_BYTES:
        dataSizeInBits = 16;
        pointerCount = 0;
        break;
      case schema::ElementSize::FOUR_BYTES:
        dataSizeInBits = 32;
        pointerCount = 0;
        break;
      case schema::ElementSize::EIGHT_BYTES:
        dataSizeInBits = 64;
        pointerCount = 0;
        break;
      case schema::ElementSize::POINTER:
        dataSizeInBits = 0;
        pointerCount = 1;
        break;
      case schema::ElementSize::INLINE_COMPOSITE:
        dataSizeInBits = structNode.getDataSectionWordSize() * 64;
        pointerCount = structNode.getPointerSectionSize();
        break;
      default:
        FAIL_VALIDATE_SCHEMA("Invalid preferredListEncoding.");
        dataSizeInBits = 0;
        pointerCount = 0;
        break;
    }

    VALIDATE_SCHEMA(structNode.getDataSectionWordSize() == (dataSizeInBits + 63) / 64 &&
                    structNode.getPointerSectionSize() == pointerCount,
                    "Struct size does not match preferredListEncoding.");

    uint ordinalCount = 0;

    auto members = structNode.getMembers();
    for (auto member: members) {
      ++ordinalCount;
      if (member.getBody().which() == schema::StructNode::Member::Body::UNION_MEMBER) {
        ordinalCount += member.getBody().getUnionMember().getMembers().size();
      }
    }

221
    KJ_STACK_ARRAY(bool, sawCodeOrder, members.size(), 32, 256);
222
    memset(sawCodeOrder.begin(), 0, sawCodeOrder.size() * sizeof(sawCodeOrder[0]));
223
    KJ_STACK_ARRAY(bool, sawOrdinal, ordinalCount, 32, 256);
224 225 226 227
    memset(sawOrdinal.begin(), 0, sawOrdinal.size() * sizeof(sawOrdinal[0]));

    uint index = 0;
    for (auto member: members) {
228
      KJ_CONTEXT("validating struct member", member.getName());
229 230 231 232
      validate(member, sawCodeOrder, sawOrdinal, dataSizeInBits, pointerCount, 0, index++);
    }
  }

233
  void validateMemberName(kj::StringPtr name, uint unionIndex, uint index) {
234 235 236 237 238
    bool isNewName = members.insert(std::make_pair(
        std::pair<uint, Text::Reader>(unionIndex, name), index)).second;
    VALIDATE_SCHEMA(isNewName, "duplicate name", name);
  }

239
  void validate(const schema::StructNode::Member::Reader& member,
240
                kj::ArrayPtr<bool> sawCodeOrder, kj::ArrayPtr<bool> sawOrdinal,
241 242 243 244 245 246 247 248 249 250
                uint dataSizeInBits, uint pointerCount,
                uint unionIndex, uint index) {
    validateMemberName(member.getName(), unionIndex, index);
    VALIDATE_SCHEMA(member.getCodeOrder() < sawCodeOrder.size() &&
                    !sawCodeOrder[member.getCodeOrder()],
                    "Invalid codeOrder.");
    sawCodeOrder[member.getCodeOrder()] = true;

    switch (member.getBody().which()) {
      case schema::StructNode::Member::Body::FIELD_MEMBER: {
251 252 253 254 255
        VALIDATE_SCHEMA(member.getOrdinal() < sawOrdinal.size() &&
                        !sawOrdinal[member.getOrdinal()],
                        "Invalid ordinal.", member.getOrdinal());
        sawOrdinal[member.getOrdinal()] = true;

256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274
        auto field = member.getBody().getFieldMember();

        uint fieldBits;
        bool fieldIsPointer;
        validate(field.getType(), field.getDefaultValue(), &fieldBits, &fieldIsPointer);
        VALIDATE_SCHEMA(fieldBits * (field.getOffset() + 1) <= dataSizeInBits &&
                        fieldIsPointer * (field.getOffset() + 1) <= pointerCount,
                        "field offset out-of-bounds",
                        field.getOffset(), dataSizeInBits, pointerCount);
        break;
      }

      case schema::StructNode::Member::Body::UNION_MEMBER: {
        auto u = member.getBody().getUnionMember();

        VALIDATE_SCHEMA((u.getDiscriminantOffset() + 1) * 16 <= dataSizeInBits,
                        "Schema invalid: Union discriminant out-of-bounds.");

        auto uMembers = u.getMembers();
275 276
        VALIDATE_SCHEMA(uMembers.size() >= 2, "Union must have at least two members.");

277
        KJ_STACK_ARRAY(bool, uSawCodeOrder, uMembers.size(), 32, 256);
278 279 280 281
        memset(uSawCodeOrder.begin(), 0, uSawCodeOrder.size() * sizeof(uSawCodeOrder[0]));

        uint subIndex = 0;
        for (auto uMember: uMembers) {
282
          KJ_CONTEXT("validating union member", uMember.getName());
283 284 285
          VALIDATE_SCHEMA(
              uMember.getBody().which() == schema::StructNode::Member::Body::FIELD_MEMBER,
              "Union members must be fields.");
286 287 288 289 290 291 292

          uint subUnionIndex;
          if (member.getName().size() == 0) {
            subUnionIndex = unionIndex;
          } else {
            subUnionIndex = index + 1;
          }
293
          validate(uMember, uSawCodeOrder, sawOrdinal, dataSizeInBits, pointerCount,
294 295 296 297 298 299 300 301 302 303
                   subUnionIndex, subIndex++);
        }

        // Union ordinal may match the ordinal of its first member, meaning it was unspecified in
        // the schema file.  Otherwise, it must be unique.
        if (member.getOrdinal() != uMembers[0].getOrdinal()) {
          VALIDATE_SCHEMA(member.getOrdinal() < sawOrdinal.size() &&
                          !sawOrdinal[member.getOrdinal()],
                          "Invalid ordinal.", member.getOrdinal());
          sawOrdinal[member.getOrdinal()] = true;
304 305 306 307 308 309
        }
        break;
      }
    }
  }

310
  void validate(const schema::EnumNode::Reader& enumNode) {
311 312
    auto enumerants = enumNode.getEnumerants();

313
    KJ_STACK_ARRAY(bool, sawCodeOrder, enumerants.size(), 32, 256);
314 315 316 317 318 319 320 321 322 323 324 325 326
    memset(sawCodeOrder.begin(), 0, sawCodeOrder.size() * sizeof(sawCodeOrder[0]));

    uint index = 0;
    for (auto enumerant: enumerants) {
      validateMemberName(enumerant.getName(), 0, index++);

      VALIDATE_SCHEMA(enumerant.getCodeOrder() < enumerants.size() &&
                      !sawCodeOrder[enumerant.getCodeOrder()],
                      "invalid codeOrder", enumerant.getName());
      sawCodeOrder[enumerant.getCodeOrder()] = true;
    }
  }

327
  void validate(const schema::InterfaceNode::Reader& interfaceNode) {
328 329
    auto methods = interfaceNode.getMethods();

330
    KJ_STACK_ARRAY(bool, sawCodeOrder, methods.size(), 32, 256);
331 332 333 334
    memset(sawCodeOrder.begin(), 0, sawCodeOrder.size() * sizeof(sawCodeOrder[0]));

    uint index = 0;
    for (auto method: methods) {
335
      KJ_CONTEXT("validating method", method.getName());
336 337 338 339 340 341 342 343 344
      validateMemberName(method.getName(), 0, index++);

      VALIDATE_SCHEMA(method.getCodeOrder() < methods.size() &&
                      !sawCodeOrder[method.getCodeOrder()],
                      "invalid codeOrder");
      sawCodeOrder[method.getCodeOrder()] = true;

      auto params = method.getParams();
      for (auto param: params) {
345
        KJ_CONTEXT("validating parameter", param.getName());
346 347 348 349 350 351 352 353 354 355 356
        uint dummy1;
        bool dummy2;
        validate(param.getType(), param.getDefaultValue(), &dummy1, &dummy2);
      }

      VALIDATE_SCHEMA(method.getRequiredParamCount() <= params.size(),
                      "invalid requiredParamCount");
      validate(method.getReturnType());
    }
  }

357
  void validate(const schema::ConstNode::Reader& constNode) {
358 359 360 361 362
    uint dummy1;
    bool dummy2;
    validate(constNode.getType(), constNode.getValue(), &dummy1, &dummy2);
  }

363
  void validate(const schema::AnnotationNode::Reader& annotationNode) {
364 365 366
    validate(annotationNode.getType());
  }

367
  void validate(const schema::Type::Reader& type, const schema::Value::Reader& value,
368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406
                uint* dataSizeInBits, bool* isPointer) {
    validate(type);

    schema::Value::Body::Which expectedValueType = schema::Value::Body::VOID_VALUE;
    bool hadCase = false;
    switch (type.getBody().which()) {
#define HANDLE_TYPE(name, bits, ptr) \
      case schema::Type::Body::name##_TYPE: \
        expectedValueType = schema::Value::Body::name##_VALUE; \
        *dataSizeInBits = bits; *isPointer = ptr; \
        hadCase = true; \
        break;
      HANDLE_TYPE(VOID, 0, false)
      HANDLE_TYPE(BOOL, 1, false)
      HANDLE_TYPE(INT8, 8, false)
      HANDLE_TYPE(INT16, 16, false)
      HANDLE_TYPE(INT32, 32, false)
      HANDLE_TYPE(INT64, 64, false)
      HANDLE_TYPE(UINT8, 8, false)
      HANDLE_TYPE(UINT16, 16, false)
      HANDLE_TYPE(UINT32, 32, false)
      HANDLE_TYPE(UINT64, 64, false)
      HANDLE_TYPE(FLOAT32, 32, false)
      HANDLE_TYPE(FLOAT64, 64, false)
      HANDLE_TYPE(TEXT, 0, true)
      HANDLE_TYPE(DATA, 0, true)
      HANDLE_TYPE(LIST, 0, true)
      HANDLE_TYPE(ENUM, 16, false)
      HANDLE_TYPE(STRUCT, 0, true)
      HANDLE_TYPE(INTERFACE, 0, true)
      HANDLE_TYPE(OBJECT, 0, true)
#undef HANDLE_TYPE
    }

    if (hadCase) {
      VALIDATE_SCHEMA(value.getBody().which() == expectedValueType, "Value did not match type.");
    }
  }

407
  void validate(const schema::Type::Reader& type) {
408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444
    switch (type.getBody().which()) {
      case schema::Type::Body::VOID_TYPE:
      case schema::Type::Body::BOOL_TYPE:
      case schema::Type::Body::INT8_TYPE:
      case schema::Type::Body::INT16_TYPE:
      case schema::Type::Body::INT32_TYPE:
      case schema::Type::Body::INT64_TYPE:
      case schema::Type::Body::UINT8_TYPE:
      case schema::Type::Body::UINT16_TYPE:
      case schema::Type::Body::UINT32_TYPE:
      case schema::Type::Body::UINT64_TYPE:
      case schema::Type::Body::FLOAT32_TYPE:
      case schema::Type::Body::FLOAT64_TYPE:
      case schema::Type::Body::TEXT_TYPE:
      case schema::Type::Body::DATA_TYPE:
      case schema::Type::Body::OBJECT_TYPE:
        break;

      case schema::Type::Body::STRUCT_TYPE:
        validateTypeId(type.getBody().getStructType(), schema::Node::Body::STRUCT_NODE);
        break;
      case schema::Type::Body::ENUM_TYPE:
        validateTypeId(type.getBody().getEnumType(), schema::Node::Body::ENUM_NODE);
        break;
      case schema::Type::Body::INTERFACE_TYPE:
        validateTypeId(type.getBody().getInterfaceType(), schema::Node::Body::INTERFACE_NODE);
        break;

      case schema::Type::Body::LIST_TYPE:
        validate(type.getBody().getListType());
        break;
    }

    // We intentionally allow unknown types.
  }

  void validateTypeId(uint64_t id, schema::Node::Body::Which expectedKind) {
445
    _::RawSchema* existing = loader.tryGet(id).schema;
446 447 448 449
    if (existing != nullptr) {
      auto node = readMessageUnchecked<schema::Node>(existing->encodedNode);
      VALIDATE_SCHEMA(node.getBody().which() == expectedKind,
          "expected a different kind of node for this ID",
Kenton Varda's avatar
Kenton Varda committed
450
          id, (uint)expectedKind, (uint)node.getBody().which(), node.getDisplayName());
451 452 453 454 455
      dependencies.insert(std::make_pair(id, existing));
      return;
    }

    dependencies.insert(std::make_pair(id, loader.loadEmpty(
456
        id, kj::str("(unknown type used by ", nodeName , ")"), expectedKind)));
457 458 459 460 461 462 463 464 465 466 467 468
  }

#undef VALIDATE_SCHEMA
#undef FAIL_VALIDATE_SCHEMA
};

// =======================================================================================

class SchemaLoader::CompatibilityChecker {
public:
  CompatibilityChecker(SchemaLoader::Impl& loader): loader(loader) {}

469 470
  bool shouldReplace(const schema::Node::Reader& existingNode,
                     const schema::Node::Reader& replacement,
471
                     bool preferReplacementIfEquivalent) {
472 473
    KJ_CONTEXT("checking compatibility with previously-loaded node of the same id",
               existingNode.getDisplayName());
474

475
    KJ_DREQUIRE(existingNode.getId() == replacement.getId());
476 477 478 479 480 481

    nodeName = existingNode.getDisplayName();
    compatibility = EQUIVALENT;

    checkCompatibility(existingNode, replacement);

482 483
    // Prefer the newer schema.
    return preferReplacementIfEquivalent ? compatibility != OLDER : compatibility == NEWER;
484 485 486 487 488 489 490 491 492 493 494 495 496 497 498
  }

private:
  SchemaLoader::Impl& loader;
  Text::Reader nodeName;

  enum Compatibility {
    EQUIVALENT,
    OLDER,
    NEWER,
    INCOMPATIBLE
  };
  Compatibility compatibility;

#define VALIDATE_SCHEMA(condition, ...) \
499
  KJ_REQUIRE(condition, ##__VA_ARGS__) { compatibility = INCOMPATIBLE; return; }
500
#define FAIL_VALIDATE_SCHEMA(...) \
501
  KJ_FAIL_REQUIRE(__VA_ARGS__) { compatibility = INCOMPATIBLE; return; }
502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534

  void replacementIsNewer() {
    switch (compatibility) {
      case EQUIVALENT:
        compatibility = NEWER;
        break;
      case OLDER:
        FAIL_VALIDATE_SCHEMA("Schema node contains some changes that are upgrades and some "
            "that are downgrades.  All changes must be in the same direction for compatibility.");
        break;
      case NEWER:
        break;
      case INCOMPATIBLE:
        break;
    }
  }

  void replacementIsOlder() {
    switch (compatibility) {
      case EQUIVALENT:
        compatibility = OLDER;
        break;
      case OLDER:
        break;
      case NEWER:
        FAIL_VALIDATE_SCHEMA("Schema node contains some changes that are upgrades and some "
            "that are downgrades.  All changes must be in the same direction for compatibility.");
        break;
      case INCOMPATIBLE:
        break;
    }
  }

535 536
  void checkCompatibility(const schema::Node::Reader& node,
                          const schema::Node::Reader& replacement) {
537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574
    // Returns whether `replacement` is equivalent, older than, newer than, or incompatible with
    // `node`.  If exceptions are enabled, this will throw an exception on INCOMPATIBLE.

    VALIDATE_SCHEMA(node.getBody().which() == replacement.getBody().which(),
                    "kind of declaration changed");

    // No need to check compatibility of the non-body parts of the node:
    // - Arbitrary renaming and moving between scopes is allowed.
    // - Annotations are ignored for compatibility purposes.

    switch (node.getBody().which()) {
      case schema::Node::Body::FILE_NODE:
        checkCompatibility(node.getBody().getFileNode(),
                           replacement.getBody().getFileNode());
        break;
      case schema::Node::Body::STRUCT_NODE:
        checkCompatibility(node.getBody().getStructNode(),
                           replacement.getBody().getStructNode());
        break;
      case schema::Node::Body::ENUM_NODE:
        checkCompatibility(node.getBody().getEnumNode(),
                           replacement.getBody().getEnumNode());
        break;
      case schema::Node::Body::INTERFACE_NODE:
        checkCompatibility(node.getBody().getInterfaceNode(),
                           replacement.getBody().getInterfaceNode());
        break;
      case schema::Node::Body::CONST_NODE:
        checkCompatibility(node.getBody().getConstNode(),
                           replacement.getBody().getConstNode());
        break;
      case schema::Node::Body::ANNOTATION_NODE:
        checkCompatibility(node.getBody().getAnnotationNode(),
                           replacement.getBody().getAnnotationNode());
        break;
    }
  }

575 576
  void checkCompatibility(const schema::FileNode::Reader& file,
                          const schema::FileNode::Reader& replacement) {
577 578 579
    // Nothing to compare.
  }

580 581
  void checkCompatibility(const schema::StructNode::Reader& structNode,
                          const schema::StructNode::Reader& replacement) {
582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619
    if (replacement.getDataSectionWordSize() > structNode.getDataSectionWordSize()) {
      replacementIsNewer();
    } else if (replacement.getDataSectionWordSize() < structNode.getDataSectionWordSize()) {
      replacementIsOlder();
    }
    if (replacement.getPointerSectionSize() > structNode.getPointerSectionSize()) {
      replacementIsNewer();
    } else if (replacement.getPointerSectionSize() < structNode.getPointerSectionSize()) {
      replacementIsOlder();
    }

    // We can do a simple comparison of preferredListEncoding here because the only case where it
    // isn't correct to compare this way is when one side is BIT/BYTE/*_BYTES while the other side
    // is POINTER, and if that were the case then the above comparisons would already have failed
    // or one of the nodes would have failed validation.
    if (replacement.getPreferredListEncoding() > structNode.getPreferredListEncoding()) {
      replacementIsNewer();
    } else if (replacement.getPreferredListEncoding() < structNode.getPreferredListEncoding()) {
      replacementIsOlder();
    }

    // The shared members should occupy corresponding positions in the member lists, since the
    // lists are sorted by ordinal.
    auto members = structNode.getMembers();
    auto replacementMembers = replacement.getMembers();
    uint count = std::min(members.size(), replacementMembers.size());

    if (replacementMembers.size() > members.size()) {
      replacementIsNewer();
    } else if (replacementMembers.size() < members.size()) {
      replacementIsOlder();
    }

    for (uint i = 0; i < count; i++) {
      checkCompatibility(members[i], replacementMembers[i]);
    }
  }

620 621
  void checkCompatibility(const schema::StructNode::Member::Reader& member,
                          const schema::StructNode::Member::Reader& replacement) {
622
    KJ_CONTEXT("comparing struct member", member.getName());
623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662

    switch (member.getBody().which()) {
      case schema::StructNode::Member::Body::FIELD_MEMBER: {
        auto field = member.getBody().getFieldMember();
        auto replacementField = replacement.getBody().getFieldMember();

        checkCompatibility(field.getType(), replacementField.getType(),
                           NO_UPGRADE_TO_STRUCT);
        checkDefaultCompatibility(field.getDefaultValue(), replacementField.getDefaultValue());

        VALIDATE_SCHEMA(field.getOffset() == replacementField.getOffset(),
                        "field position changed");
        break;
      }
      case schema::StructNode::Member::Body::UNION_MEMBER: {
        auto existingUnion = member.getBody().getUnionMember();
        auto replacementUnion = replacement.getBody().getUnionMember();

        VALIDATE_SCHEMA(
            existingUnion.getDiscriminantOffset() == replacementUnion.getDiscriminantOffset(),
            "union discriminant position changed");

        auto members = existingUnion.getMembers();
        auto replacementMembers = replacementUnion.getMembers();
        uint count = std::min(members.size(), replacementMembers.size());

        if (replacementMembers.size() > members.size()) {
          replacementIsNewer();
        } else if (replacementMembers.size() < members.size()) {
          replacementIsOlder();
        }

        for (uint i = 0; i < count; i++) {
          checkCompatibility(members[i], replacementMembers[i]);
        }
        break;
      }
    }
  }

663 664
  void checkCompatibility(const schema::EnumNode::Reader& enumNode,
                          const schema::EnumNode::Reader& replacement) {
665 666 667 668 669 670 671 672 673
    uint size = enumNode.getEnumerants().size();
    uint replacementSize = replacement.getEnumerants().size();
    if (replacementSize > size) {
      replacementIsNewer();
    } else if (replacementSize < size) {
      replacementIsOlder();
    }
  }

674 675
  void checkCompatibility(const schema::InterfaceNode::Reader& interfaceNode,
                          const schema::InterfaceNode::Reader& replacement) {
676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691
    auto methods = interfaceNode.getMethods();
    auto replacementMethods = replacement.getMethods();

    if (replacementMethods.size() > methods.size()) {
      replacementIsNewer();
    } else if (replacementMethods.size() < methods.size()) {
      replacementIsOlder();
    }

    uint count = std::min(methods.size(), replacementMethods.size());

    for (uint i = 0; i < count; i++) {
      checkCompatibility(methods[i], replacementMethods[i]);
    }
  }

692 693
  void checkCompatibility(const schema::InterfaceNode::Method::Reader& method,
                          const schema::InterfaceNode::Method::Reader& replacement) {
694
    KJ_CONTEXT("comparing method", method.getName());
695 696 697 698 699 700 701 702 703 704 705 706 707 708 709

    auto params = method.getParams();
    auto replacementParams = replacement.getParams();

    if (replacementParams.size() > params.size()) {
      replacementIsNewer();
    } else if (replacementParams.size() < params.size()) {
      replacementIsOlder();
    }

    uint count = std::min(params.size(), replacementParams.size());
    for (uint i = 0; i < count; i++) {
      auto param = params[i];
      auto replacementParam = replacementParams[i];

710
      KJ_CONTEXT("comparing parameter", param.getName());
711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731

      checkCompatibility(param.getType(), replacementParam.getType(),
                         NO_UPGRADE_TO_STRUCT);
      checkDefaultCompatibility(param.getDefaultValue(), replacementParam.getDefaultValue());
    }

    // Before checking that the required parameter counts are equal, check if the user added new
    // parameters without defaulting them, as this is the most common reason for this error and we
    // can provide a nicer error message.
    VALIDATE_SCHEMA(replacement.getRequiredParamCount() <= count &&
                    method.getRequiredParamCount() <= count,
        "Updated method signature contains additional parameters that lack default values");

    VALIDATE_SCHEMA(replacement.getRequiredParamCount() == method.getRequiredParamCount(),
        "Updated method signature has different number of required parameters (parameters without "
        "default values)");

    checkCompatibility(method.getReturnType(), replacement.getReturnType(),
                       ALLOW_UPGRADE_TO_STRUCT);
  }

732 733
  void checkCompatibility(const schema::ConstNode::Reader& constNode,
                          const schema::ConstNode::Reader& replacement) {
734 735 736
    // Who cares?  These don't appear on the wire.
  }

737 738
  void checkCompatibility(const schema::AnnotationNode::Reader& annotationNode,
                          const schema::AnnotationNode::Reader& replacement) {
739 740 741 742 743 744 745 746
    // Who cares?  These don't appear on the wire.
  }

  enum UpgradeToStructMode {
    ALLOW_UPGRADE_TO_STRUCT,
    NO_UPGRADE_TO_STRUCT
  };

747 748
  void checkCompatibility(const schema::Type::Reader& type,
                          const schema::Type::Reader& replacement,
749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801
                          UpgradeToStructMode upgradeToStructMode) {
    if (replacement.getBody().which() != type.getBody().which()) {
      // Check for allowed "upgrade" to Data or Object.
      if (replacement.getBody().which() == schema::Type::Body::DATA_TYPE &&
          canUpgradeToData(type)) {
        replacementIsNewer();
        return;
      } else if (type.getBody().which() == schema::Type::Body::DATA_TYPE &&
                 canUpgradeToData(replacement)) {
        replacementIsOlder();
        return;
      } else if (replacement.getBody().which() == schema::Type::Body::OBJECT_TYPE &&
                 canUpgradeToObject(type)) {
        replacementIsNewer();
        return;
      } else if (type.getBody().which() == schema::Type::Body::OBJECT_TYPE &&
                 canUpgradeToObject(replacement)) {
        replacementIsOlder();
        return;
      }

      if (upgradeToStructMode == ALLOW_UPGRADE_TO_STRUCT) {
        if (type.getBody().which() == schema::Type::Body::STRUCT_TYPE) {
          checkUpgradeToStruct(replacement, type.getBody().getStructType());
          return;
        } else if (replacement.getBody().which() == schema::Type::Body::STRUCT_TYPE) {
          checkUpgradeToStruct(type, replacement.getBody().getStructType());
          return;
        }
      }

      FAIL_VALIDATE_SCHEMA("a type was changed");
    }

    switch (type.getBody().which()) {
      case schema::Type::Body::VOID_TYPE:
      case schema::Type::Body::BOOL_TYPE:
      case schema::Type::Body::INT8_TYPE:
      case schema::Type::Body::INT16_TYPE:
      case schema::Type::Body::INT32_TYPE:
      case schema::Type::Body::INT64_TYPE:
      case schema::Type::Body::UINT8_TYPE:
      case schema::Type::Body::UINT16_TYPE:
      case schema::Type::Body::UINT32_TYPE:
      case schema::Type::Body::UINT64_TYPE:
      case schema::Type::Body::FLOAT32_TYPE:
      case schema::Type::Body::FLOAT64_TYPE:
      case schema::Type::Body::TEXT_TYPE:
      case schema::Type::Body::DATA_TYPE:
      case schema::Type::Body::OBJECT_TYPE:
        return;

      case schema::Type::Body::LIST_TYPE:
802 803 804 805
        checkCompatibility(type.getBody().getListType(),
                           replacement.getBody().getListType(),
                           ALLOW_UPGRADE_TO_STRUCT);
        return;
806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833

      case schema::Type::Body::ENUM_TYPE:
        VALIDATE_SCHEMA(replacement.getBody().getEnumType() == type.getBody().getEnumType(),
                        "type changed enum type");
        return;

      case schema::Type::Body::STRUCT_TYPE:
        // TODO(someday):  If the IDs don't match, we should compare the two structs for
        //   compatibility.  This is tricky, though, because the new type's target may not yet be
        //   loaded.  In that case we could take the old type, make a copy of it, assign the new
        //   ID to the copy, and load() that.  That forces any struct type loaded for that ID to
        //   be compatible.  However, that has another problem, which is that it could be that the
        //   whole reason the type was replaced was to fork that type, and so an incompatibility
        //   could be very much expected.  This could be a rat hole...
        VALIDATE_SCHEMA(replacement.getBody().getStructType() == type.getBody().getStructType(),
                        "type changed to incompatible struct type");
        return;

      case schema::Type::Body::INTERFACE_TYPE:
        VALIDATE_SCHEMA(
            replacement.getBody().getInterfaceType() == type.getBody().getInterfaceType(),
            "type changed to incompatible interface type");
        return;
    }

    // We assume unknown types (from newer versions of Cap'n Proto?) are equivalent.
  }

834
  void checkUpgradeToStruct(const schema::Type::Reader& type, uint64_t structTypeId) {
835 836 837 838 839 840 841
    // We can't just look up the target struct and check it because it may not have been loaded
    // yet.  Instead, we contrive a struct that looks like what we want and load() that, which
    // guarantees that any incompatibility will be caught either now or when the real version of
    // that struct is loaded.

    word scratch[32];
    memset(scratch, 0, sizeof(scratch));
842
    MallocMessageBuilder builder(kj::arrayPtr(scratch, sizeof(scratch)));
843 844
    auto node = builder.initRoot<schema::Node>();
    node.setId(structTypeId);
845
    node.setDisplayName(kj::str("(unknown type used in ", nodeName, ")"));
846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909
    auto structNode = node.getBody().initStructNode();

    switch (type.getBody().which()) {
      case schema::Type::Body::VOID_TYPE:
        structNode.setDataSectionWordSize(0);
        structNode.setPointerSectionSize(0);
        structNode.setPreferredListEncoding(schema::ElementSize::EMPTY);
        break;

      case schema::Type::Body::BOOL_TYPE:
        structNode.setDataSectionWordSize(1);
        structNode.setPointerSectionSize(0);
        structNode.setPreferredListEncoding(schema::ElementSize::BIT);
        break;

      case schema::Type::Body::INT8_TYPE:
      case schema::Type::Body::UINT8_TYPE:
        structNode.setDataSectionWordSize(1);
        structNode.setPointerSectionSize(0);
        structNode.setPreferredListEncoding(schema::ElementSize::BYTE);
        break;

      case schema::Type::Body::INT16_TYPE:
      case schema::Type::Body::UINT16_TYPE:
      case schema::Type::Body::ENUM_TYPE:
        structNode.setDataSectionWordSize(1);
        structNode.setPointerSectionSize(0);
        structNode.setPreferredListEncoding(schema::ElementSize::TWO_BYTES);
        break;

      case schema::Type::Body::INT32_TYPE:
      case schema::Type::Body::UINT32_TYPE:
      case schema::Type::Body::FLOAT32_TYPE:
        structNode.setDataSectionWordSize(1);
        structNode.setPointerSectionSize(0);
        structNode.setPreferredListEncoding(schema::ElementSize::FOUR_BYTES);
        break;

      case schema::Type::Body::INT64_TYPE:
      case schema::Type::Body::UINT64_TYPE:
      case schema::Type::Body::FLOAT64_TYPE:
        structNode.setDataSectionWordSize(1);
        structNode.setPointerSectionSize(0);
        structNode.setPreferredListEncoding(schema::ElementSize::EIGHT_BYTES);
        break;

      case schema::Type::Body::TEXT_TYPE:
      case schema::Type::Body::DATA_TYPE:
      case schema::Type::Body::LIST_TYPE:
      case schema::Type::Body::STRUCT_TYPE:
      case schema::Type::Body::INTERFACE_TYPE:
      case schema::Type::Body::OBJECT_TYPE:
        structNode.setDataSectionWordSize(0);
        structNode.setPointerSectionSize(1);
        structNode.setPreferredListEncoding(schema::ElementSize::POINTER);
        break;
    }

    auto member = structNode.initMembers(1)[0];
    member.setName("member0");
    member.setOrdinal(0);
    member.setCodeOrder(0);
    member.getBody().initFieldMember().setType(type);

910
    loader.load(node, true);
911 912
  }

913
  bool canUpgradeToData(const schema::Type::Reader& type) {
914 915 916 917 918 919 920 921 922 923 924 925 926 927 928
    if (type.getBody().which() == schema::Type::Body::TEXT_TYPE) {
      return true;
    } else if (type.getBody().which() == schema::Type::Body::LIST_TYPE) {
      switch (type.getBody().getListType().getBody().which()) {
        case schema::Type::Body::INT8_TYPE:
        case schema::Type::Body::UINT8_TYPE:
          return true;
        default:
          return false;
      }
    } else {
      return false;
    }
  }

929
  bool canUpgradeToObject(const schema::Type::Reader& type) {
930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958
    switch (type.getBody().which()) {
      case schema::Type::Body::VOID_TYPE:
      case schema::Type::Body::BOOL_TYPE:
      case schema::Type::Body::INT8_TYPE:
      case schema::Type::Body::INT16_TYPE:
      case schema::Type::Body::INT32_TYPE:
      case schema::Type::Body::INT64_TYPE:
      case schema::Type::Body::UINT8_TYPE:
      case schema::Type::Body::UINT16_TYPE:
      case schema::Type::Body::UINT32_TYPE:
      case schema::Type::Body::UINT64_TYPE:
      case schema::Type::Body::FLOAT32_TYPE:
      case schema::Type::Body::FLOAT64_TYPE:
      case schema::Type::Body::ENUM_TYPE:
        return false;

      case schema::Type::Body::TEXT_TYPE:
      case schema::Type::Body::DATA_TYPE:
      case schema::Type::Body::LIST_TYPE:
      case schema::Type::Body::STRUCT_TYPE:
      case schema::Type::Body::INTERFACE_TYPE:
      case schema::Type::Body::OBJECT_TYPE:
        return true;
    }

    // Be lenient with unknown types.
    return true;
  }

959 960
  void checkDefaultCompatibility(const schema::Value::Reader& value,
                                 const schema::Value::Reader& replacement) {
961 962
    // Note that we test default compatibility only after testing type compatibility, and default
    // values have already been validated as matching their types, so this should pass.
963
    KJ_ASSERT(value.getBody().which() == replacement.getBody().which()) {
964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004
      compatibility = INCOMPATIBLE;
      return;
    }

    switch (value.getBody().which()) {
#define HANDLE_TYPE(discrim, name) \
      case schema::Value::Body::discrim##_VALUE: \
        VALIDATE_SCHEMA(value.getBody().get##name##Value() == \
                        replacement.getBody().get##name##Value(), \
                        "default value changed"); \
        break;
      HANDLE_TYPE(VOID, Void);
      HANDLE_TYPE(BOOL, Bool);
      HANDLE_TYPE(INT8, Int8);
      HANDLE_TYPE(INT16, Int16);
      HANDLE_TYPE(INT32, Int32);
      HANDLE_TYPE(INT64, Int64);
      HANDLE_TYPE(UINT8, Uint8);
      HANDLE_TYPE(UINT16, Uint16);
      HANDLE_TYPE(UINT32, Uint32);
      HANDLE_TYPE(UINT64, Uint64);
      HANDLE_TYPE(FLOAT32, Float32);
      HANDLE_TYPE(FLOAT64, Float64);
      HANDLE_TYPE(ENUM, Enum);
#undef HANDLE_TYPE

      case schema::Value::Body::TEXT_VALUE:
      case schema::Value::Body::DATA_VALUE:
      case schema::Value::Body::LIST_VALUE:
      case schema::Value::Body::STRUCT_VALUE:
      case schema::Value::Body::INTERFACE_VALUE:
      case schema::Value::Body::OBJECT_VALUE:
        // It's not a big deal if default values for pointers change, and it would be difficult for
        // us to compare these defaults here, so just let it slide.
        break;
    }
  }
};

// =======================================================================================

1005
_::RawSchema* SchemaLoader::Impl::load(const schema::Node::Reader& reader, bool isPlaceholder) {
1006 1007
  // Make a copy of the node which can be used unchecked.
  size_t size = reader.totalSizeInWords() + 1;
1008 1009 1010
  kj::ArrayPtr<word> validated = arena.allocateArray<word>(size);
  memset(validated.begin(), 0, size * sizeof(word));
  copyToUnchecked(reader, validated);
1011 1012 1013

  // Validate the copy.
  Validator validator(*this);
1014
  auto validatedReader = readMessageUnchecked<schema::Node>(validated.begin());
1015 1016 1017 1018 1019 1020 1021 1022 1023

  if (!validator.validate(validatedReader)) {
    // Not valid.  Construct an empty schema of the same type and return that.
    return loadEmpty(validatedReader.getId(),
                     validatedReader.getDisplayName(),
                     validatedReader.getBody().which());
  }

  // Check if we already have a schema for this ID.
1024
  _::RawSchema*& slot = schemas[validatedReader.getId()];
1025
  bool shouldReplace;
1026 1027
  if (slot == nullptr) {
    // Nope, allocate a new RawSchema.
1028
    slot = &arena.allocate<_::RawSchema>();
1029 1030 1031
    slot->id = validatedReader.getId();
    slot->canCastTo = nullptr;
    shouldReplace = true;
1032 1033
  } else {
    // Yes, check if it is compatible and figure out which schema is newer.
1034 1035 1036 1037 1038 1039 1040

    if (slot->lazyInitializer == nullptr) {
      // The existing slot is not a placeholder, so whether we overwrite it or not, we cannot
      // end up with a placeholder.
      isPlaceholder = false;
    }

1041 1042
    auto existing = readMessageUnchecked<schema::Node>(slot->encodedNode);
    CompatibilityChecker checker(*this);
1043 1044 1045 1046 1047

    // Prefer to replace the existing schema if the existing schema is a placeholder.  Otherwise,
    // prefer to keep the existing schema.
    shouldReplace = checker.shouldReplace(
        existing, validatedReader, slot->lazyInitializer != nullptr);
1048 1049
  }

1050 1051 1052
  if (shouldReplace) {
    // Initialize the RawSchema.
    slot->encodedNode = validated.begin();
Kenton Varda's avatar
Kenton Varda committed
1053
    slot->encodedSize = validated.size();
1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065
    slot->dependencies = validator.makeDependencyArray(&slot->dependencyCount);
    slot->membersByName = validator.makeMemberInfoArray(&slot->memberCount);
  }

  if (isPlaceholder) {
    slot->lazyInitializer = &initializer;
  } else {
    // If this schema is not newly-allocated, it may already be in the wild, specifically in the
    // dependency list of other schemas.  Once the initializer is null, it is live, so we must do
    // a release-store here.
    __atomic_store_n(&slot->lazyInitializer, nullptr, __ATOMIC_RELEASE);
  }
1066 1067 1068 1069

  return slot;
}

1070
_::RawSchema* SchemaLoader::Impl::loadNative(const _::RawSchema* nativeSchema) {
1071 1072
  _::RawSchema*& slot = schemas[nativeSchema->id];
  bool shouldReplace;
1073
  if (slot == nullptr) {
1074
    slot = &arena.allocate<_::RawSchema>();
1075
    shouldReplace = true;
1076
  } else if (slot->canCastTo != nullptr) {
1077 1078
    // Already loaded natively, or we're currently in the process of loading natively and there
    // was a dependency cycle.
1079
    KJ_REQUIRE(slot->canCastTo == nativeSchema,
1080
        "two different compiled-in type have the same type ID",
1081 1082
        nativeSchema->id,
        readMessageUnchecked<schema::Node>(nativeSchema->encodedNode).getDisplayName(),
1083 1084 1085 1086 1087 1088
        readMessageUnchecked<schema::Node>(slot->canCastTo->encodedNode).getDisplayName());
    return slot;
  } else {
    auto existing = readMessageUnchecked<schema::Node>(slot->encodedNode);
    auto native = readMessageUnchecked<schema::Node>(nativeSchema->encodedNode);
    CompatibilityChecker checker(*this);
1089
    shouldReplace = checker.shouldReplace(existing, native, true);
1090 1091
  }

1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112
  // Since we recurse below, the slot in the hash map could move around.  Copy out the pointer
  // for subsequent use.
  _::RawSchema* result = slot;

  if (shouldReplace) {
    // Set the schema to a copy of the native schema.
    *kj::implicitCast<_::RawSchema*>(result) = *nativeSchema;

    // Indicate that casting is safe.  Note that it's important to set this before recursively
    // loading dependencies, so that cycles don't cause infinite loops!
    result->canCastTo = nativeSchema;

    // Except that we need to set the dependency list to point at other loader-owned RawSchemas.
    kj::ArrayPtr<const _::RawSchema*> dependencies =
        arena.allocateArray<const _::RawSchema*>(result->dependencyCount);
    for (uint i = 0; i < nativeSchema->dependencyCount; i++) {
      dependencies[i] = loadNative(nativeSchema->dependencies[i]);
    }
    result->dependencies = dependencies.begin();
  } else {
    // The existing schema is newer.
1113

1114 1115 1116
    // Indicate that casting is safe.  Note that it's important to set this before recursively
    // loading dependencies, so that cycles don't cause infinite loops!
    result->canCastTo = nativeSchema;
1117

1118 1119 1120 1121
    // Make sure the dependencies are loaded and compatible.
    for (uint i = 0; i < nativeSchema->dependencyCount; i++) {
      loadNative(nativeSchema->dependencies[i]);
    }
1122 1123
  }

1124 1125 1126 1127 1128 1129
  // If this schema is not newly-allocated, it may already be in the wild, specifically in the
  // dependency list of other schemas.  Once the initializer is null, it is live, so we must do
  // a release-store here.
  __atomic_store_n(&result->lazyInitializer, nullptr, __ATOMIC_RELEASE);

  return result;
1130 1131
}

1132
_::RawSchema* SchemaLoader::Impl::loadEmpty(
1133
    uint64_t id, kj::StringPtr name, schema::Node::Body::Which kind) {
1134 1135
  word scratch[32];
  memset(scratch, 0, sizeof(scratch));
1136
  MallocMessageBuilder builder(kj::arrayPtr(scratch, sizeof(scratch)));
1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147
  auto node = builder.initRoot<schema::Node>();
  node.setId(id);
  node.setDisplayName(name);
  switch (kind) {
    case schema::Node::Body::STRUCT_NODE: node.getBody().initStructNode(); break;
    case schema::Node::Body::ENUM_NODE: node.getBody().initEnumNode(); break;
    case schema::Node::Body::INTERFACE_NODE: node.getBody().initInterfaceNode(); break;

    case schema::Node::Body::FILE_NODE:
    case schema::Node::Body::CONST_NODE:
    case schema::Node::Body::ANNOTATION_NODE:
1148
      KJ_FAIL_REQUIRE("Not a type.");
1149 1150 1151
      break;
  }

1152
  return load(node, true);
1153 1154
}

1155
SchemaLoader::Impl::TryGetResult SchemaLoader::Impl::tryGet(uint64_t typeId) const {
1156 1157
  auto iter = schemas.find(typeId);
  if (iter == schemas.end()) {
1158
    return {nullptr, initializer.getCallback()};
1159
  } else {
1160
    return {iter->second, initializer.getCallback()};
1161 1162 1163
  }
}

1164
kj::Array<Schema> SchemaLoader::Impl::getAllLoaded() const {
1165 1166 1167 1168 1169 1170
  size_t count = 0;
  for (auto& schema: schemas) {
    if (schema.second->lazyInitializer == nullptr) ++count;
  }

  kj::Array<Schema> result = kj::heapArray<Schema>(count);
1171 1172
  size_t i = 0;
  for (auto& schema: schemas) {
1173
    if (schema.second->lazyInitializer == nullptr) result[i++] = Schema(schema.second);
1174 1175 1176 1177
  }
  return result;
}

1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188
void SchemaLoader::InitializerImpl::init(const _::RawSchema* schema) const {
  KJ_IF_MAYBE(c, callback) {
    c->load(loader, schema->id);
  }

  if (schema->lazyInitializer != nullptr) {
    // The callback declined to load a schema.  We need to disable the initializer so that it
    // doesn't get invoked again later, as we can no longer modify this schema once it is in use.

    // Lock the loader for read to make sure no one is concurrently loading a replacement for this
    // schema node.
1189
    auto lock = loader.impl.lockShared();
1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200

    // Get the mutable version of the schema.
    _::RawSchema* mutableSchema = lock->get()->tryGet(schema->id).schema;
    KJ_ASSERT(mutableSchema == schema,
              "A schema not belonging to this loader used its initializer.");

    // Disable the initializer.
    __atomic_store_n(&mutableSchema->lazyInitializer, nullptr, __ATOMIC_RELEASE);
  }
}

1201 1202
// =======================================================================================

1203 1204 1205
SchemaLoader::SchemaLoader(): impl(kj::heap<Impl>(*this)) {}
SchemaLoader::SchemaLoader(const LazyLoadCallback& callback)
    : impl(kj::heap<Impl>(*this, callback)) {}
1206
SchemaLoader::~SchemaLoader() noexcept(false) {}
1207 1208

Schema SchemaLoader::get(uint64_t id) const {
1209 1210 1211 1212 1213
  KJ_IF_MAYBE(result, tryGet(id)) {
    return *result;
  } else {
    KJ_FAIL_REQUIRE("no schema node loaded for id", id);
  }
1214 1215
}

1216
kj::Maybe<Schema> SchemaLoader::tryGet(uint64_t id) const {
1217
  auto getResult = impl.lockShared()->get()->tryGet(id);
1218 1219 1220 1221
  if (getResult.schema == nullptr || getResult.schema->lazyInitializer != nullptr) {
    KJ_IF_MAYBE(c, getResult.callback) {
      c->load(*this, id);
    }
1222
    getResult = impl.lockShared()->get()->tryGet(id);
1223 1224 1225
  }
  if (getResult.schema != nullptr && getResult.schema->lazyInitializer == nullptr) {
    return Schema(getResult.schema);
1226
  } else {
1227
    return nullptr;
1228 1229 1230
  }
}

1231
Schema SchemaLoader::load(const schema::Node::Reader& reader) {
1232
  return Schema(impl.lockExclusive()->get()->load(reader, false));
1233 1234
}

Kenton Varda's avatar
Kenton Varda committed
1235
Schema SchemaLoader::loadOnce(const schema::Node::Reader& reader) const {
1236
  auto locked = impl.lockExclusive();
1237 1238 1239 1240 1241 1242 1243 1244
  auto getResult = locked->get()->tryGet(reader.getId());
  if (getResult.schema == nullptr || getResult.schema->lazyInitializer != nullptr) {
    // Doesn't exist yet, or the existing schema is a placeholder and therefore has not yet been
    // seen publicly.  Go ahead and load the incoming reader.
    return Schema(locked->get()->load(reader, false));
  } else {
    return Schema(getResult.schema);
  }
1245 1246
}

1247
kj::Array<Schema> SchemaLoader::getAllLoaded() const {
1248
  return impl.lockShared()->get()->getAllLoaded();
1249 1250
}

1251
void SchemaLoader::loadNative(const _::RawSchema* nativeSchema) {
1252
  impl.lockExclusive()->get()->loadNative(nativeSchema);
1253 1254
}

1255
}  // namespace capnp