Chris@64: // Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors Chris@64: // Licensed under the MIT License: Chris@64: // Chris@64: // Permission is hereby granted, free of charge, to any person obtaining a copy Chris@64: // of this software and associated documentation files (the "Software"), to deal Chris@64: // in the Software without restriction, including without limitation the rights Chris@64: // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell Chris@64: // copies of the Software, and to permit persons to whom the Software is Chris@64: // furnished to do so, subject to the following conditions: Chris@64: // Chris@64: // The above copyright notice and this permission notice shall be included in Chris@64: // all copies or substantial portions of the Software. Chris@64: // Chris@64: // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR Chris@64: // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, Chris@64: // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE Chris@64: // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER Chris@64: // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, Chris@64: // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN Chris@64: // THE SOFTWARE. Chris@64: Chris@64: #ifndef CAPNP_SCHEMA_LOADER_H_ Chris@64: #define CAPNP_SCHEMA_LOADER_H_ Chris@64: Chris@64: #if defined(__GNUC__) && !defined(CAPNP_HEADER_WARNINGS) Chris@64: #pragma GCC system_header Chris@64: #endif Chris@64: Chris@64: #include "schema.h" Chris@64: #include Chris@64: #include Chris@64: Chris@64: namespace capnp { Chris@64: Chris@64: class SchemaLoader { Chris@64: // Class which can be used to construct Schema objects from schema::Nodes as defined in Chris@64: // schema.capnp. Chris@64: // Chris@64: // It is a bad idea to use this class on untrusted input with exceptions disabled -- you may Chris@64: // be exposing yourself to denial-of-service attacks, as attackers can easily construct schemas Chris@64: // that are subtly inconsistent in a way that causes exceptions to be thrown either by Chris@64: // SchemaLoader or by the dynamic API when the schemas are subsequently used. If you enable and Chris@64: // properly catch exceptions, you should be OK -- assuming no bugs in the Cap'n Proto Chris@64: // implementation, of course. Chris@64: Chris@64: public: Chris@64: class LazyLoadCallback { Chris@64: public: Chris@64: virtual void load(const SchemaLoader& loader, uint64_t id) const = 0; Chris@64: // Request that the schema node with the given ID be loaded into the given SchemaLoader. If Chris@64: // the callback is able to find a schema for this ID, it should invoke `loadOnce()` on Chris@64: // `loader` to load it. If no such node exists, it should simply do nothing and return. Chris@64: // Chris@64: // The callback is allowed to load schema nodes other than the one requested, e.g. because it Chris@64: // expects they will be needed soon. Chris@64: // Chris@64: // If the `SchemaLoader` is used from multiple threads, the callback must be thread-safe. Chris@64: // In particular, it's possible for multiple threads to invoke `load()` with the same ID. Chris@64: // If the callback performs a large amount of work to look up IDs, it should be sure to Chris@64: // de-dup these requests. Chris@64: }; Chris@64: Chris@64: SchemaLoader(); Chris@64: Chris@64: SchemaLoader(const LazyLoadCallback& callback); Chris@64: // Construct a SchemaLoader which will invoke the given callback when a schema node is requested Chris@64: // that isn't already loaded. Chris@64: Chris@64: ~SchemaLoader() noexcept(false); Chris@64: KJ_DISALLOW_COPY(SchemaLoader); Chris@64: Chris@64: Schema get(uint64_t id, schema::Brand::Reader brand = schema::Brand::Reader(), Chris@64: Schema scope = Schema()) const; Chris@64: // Gets the schema for the given ID, throwing an exception if it isn't present. Chris@64: // Chris@64: // The returned schema may be invalidated if load() is called with a new schema for the same ID. Chris@64: // In general, you should not call load() while a schema from this loader is in-use. Chris@64: // Chris@64: // `brand` and `scope` are used to determine brand bindings where relevant. `brand` gives Chris@64: // parameter bindings for the target type's brand parameters that were specified at the reference Chris@64: // site. `scope` specifies the scope in which the type ID appeared -- if `brand` itself contains Chris@64: // parameter references or indicates that some parameters will be inherited, these will be Chris@64: // interpreted within / inherited from `scope`. Chris@64: Chris@64: kj::Maybe tryGet(uint64_t id, schema::Brand::Reader bindings = schema::Brand::Reader(), Chris@64: Schema scope = Schema()) const; Chris@64: // Like get() but doesn't throw. Chris@64: Chris@64: Schema getUnbound(uint64_t id) const; Chris@64: // Gets a special version of the schema in which all brand parameters are "unbound". This means Chris@64: // that if you look up a type via the Schema API, and it resolves to a brand parameter, the Chris@64: // returned Type's getBrandParameter() method will return info about that parameter. Otherwise, Chris@64: // normally, all brand parameters that aren't otherwise bound are assumed to simply be Chris@64: // "AnyPointer". Chris@64: Chris@64: Type getType(schema::Type::Reader type, Schema scope = Schema()) const; Chris@64: // Convenience method which interprets a schema::Type to produce a Type object. Implemented in Chris@64: // terms of get(). Chris@64: Chris@64: Schema load(const schema::Node::Reader& reader); Chris@64: // Loads the given schema node. Validates the node and throws an exception if invalid. This Chris@64: // makes a copy of the schema, so the object passed in can be destroyed after this returns. Chris@64: // Chris@64: // If the node has any dependencies which are not already loaded, they will be initialized as Chris@64: // stubs -- empty schemas of whichever kind is expected. Chris@64: // Chris@64: // If another schema for the given reader has already been seen, the loader will inspect both Chris@64: // schemas to determine which one is newer, and use that that one. If the two versions are Chris@64: // found to be incompatible, an exception is thrown. If the two versions differ but are Chris@64: // compatible and the loader cannot determine which is newer (e.g., the only changes are renames), Chris@64: // the existing schema will be preferred. Note that in any case, the loader will end up keeping Chris@64: // around copies of both schemas, so you shouldn't repeatedly reload schemas into the same loader. Chris@64: // Chris@64: // The following properties of the schema node are validated: Chris@64: // - Struct size and preferred list encoding are valid and consistent. Chris@64: // - Struct members are fields or unions. Chris@64: // - Union members are fields. Chris@64: // - Field offsets are in-bounds. Chris@64: // - Ordinals and codeOrders are sequential starting from zero. Chris@64: // - Values are of the right union case to match their types. Chris@64: // Chris@64: // You should assume anything not listed above is NOT validated. In particular, things that are Chris@64: // not validated now, but could be in the future, include but are not limited to: Chris@64: // - Names. Chris@64: // - Annotation values. (This is hard because the annotation declaration is not always Chris@64: // available.) Chris@64: // - Content of default/constant values of pointer type. (Validating these would require knowing Chris@64: // their schema, but even if the schemas are available at validation time, they could be Chris@64: // updated by a subsequent load(), invalidating existing values. Instead, these values are Chris@64: // validated at the time they are used, as usual for Cap'n Proto objects.) Chris@64: // Chris@64: // Also note that unknown types are not considered invalid. Instead, the dynamic API returns Chris@64: // a DynamicValue with type UNKNOWN for these. Chris@64: Chris@64: Schema loadOnce(const schema::Node::Reader& reader) const; Chris@64: // Like `load()` but does nothing if a schema with the same ID is already loaded. In contrast, Chris@64: // `load()` would attempt to compare the schemas and take the newer one. `loadOnce()` is safe Chris@64: // to call even while concurrently using schemas from this loader. It should be considered an Chris@64: // error to call `loadOnce()` with two non-identical schemas that share the same ID, although Chris@64: // this error may or may not actually be detected by the implementation. Chris@64: Chris@64: template Chris@64: void loadCompiledTypeAndDependencies(); Chris@64: // Load the schema for the given compiled-in type and all of its dependencies. Chris@64: // Chris@64: // If you want to be able to cast a DynamicValue built from this SchemaLoader to the compiled-in Chris@64: // type using as(), you must call this method before constructing the DynamicValue. Otherwise, Chris@64: // as() will throw an exception complaining about type mismatch. Chris@64: Chris@64: kj::Array getAllLoaded() const; Chris@64: // Get a complete list of all loaded schema nodes. It is particularly useful to call this after Chris@64: // loadCompiledTypeAndDependencies() in order to get a flat list of all of T's transitive Chris@64: // dependencies. Chris@64: Chris@64: private: Chris@64: class Validator; Chris@64: class CompatibilityChecker; Chris@64: class Impl; Chris@64: class InitializerImpl; Chris@64: class BrandedInitializerImpl; Chris@64: kj::MutexGuarded> impl; Chris@64: Chris@64: void loadNative(const _::RawSchema* nativeSchema); Chris@64: }; Chris@64: Chris@64: template Chris@64: inline void SchemaLoader::loadCompiledTypeAndDependencies() { Chris@64: loadNative(&_::rawSchema()); Chris@64: } Chris@64: Chris@64: } // namespace capnp Chris@64: Chris@64: #endif // CAPNP_SCHEMA_LOADER_H_