Chris@47: // Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
Chris@47: // Licensed under the MIT License:
Chris@47: //
Chris@47: // Permission is hereby granted, free of charge, to any person obtaining a copy
Chris@47: // of this software and associated documentation files (the "Software"), to deal
Chris@47: // in the Software without restriction, including without limitation the rights
Chris@47: // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
Chris@47: // copies of the Software, and to permit persons to whom the Software is
Chris@47: // furnished to do so, subject to the following conditions:
Chris@47: //
Chris@47: // The above copyright notice and this permission notice shall be included in
Chris@47: // all copies or substantial portions of the Software.
Chris@47: //
Chris@47: // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
Chris@47: // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
Chris@47: // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
Chris@47: // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
Chris@47: // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
Chris@47: // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
Chris@47: // THE SOFTWARE.
Chris@47: 
Chris@47: #ifndef CAPNP_ORPHAN_H_
Chris@47: #define CAPNP_ORPHAN_H_
Chris@47: 
Chris@47: #if defined(__GNUC__) && !defined(CAPNP_HEADER_WARNINGS)
Chris@47: #pragma GCC system_header
Chris@47: #endif
Chris@47: 
Chris@47: #include "layout.h"
Chris@47: 
Chris@47: namespace capnp {
Chris@47: 
Chris@47: class StructSchema;
Chris@47: class ListSchema;
Chris@47: struct DynamicStruct;
Chris@47: struct DynamicList;
Chris@47: namespace _ { struct OrphanageInternal; }
Chris@47: 
Chris@47: template <typename T>
Chris@47: class Orphan {
Chris@47:   // Represents an object which is allocated within some message builder but has no pointers
Chris@47:   // pointing at it.  An Orphan can later be "adopted" by some other object as one of that object's
Chris@47:   // fields, without having to copy the orphan.  For a field `foo` of pointer type, the generated
Chris@47:   // code will define builder methods `void adoptFoo(Orphan<T>)` and `Orphan<T> disownFoo()`.
Chris@47:   // Orphans can also be created independently of any parent using an Orphanage.
Chris@47:   //
Chris@47:   // `Orphan<T>` can be moved but not copied, like `Own<T>`, so that it is impossible for one
Chris@47:   // orphan to be adopted multiple times.  If an orphan is destroyed without being adopted, its
Chris@47:   // contents are zero'd out (and possibly reused, if we ever implement the ability to reuse space
Chris@47:   // in a message arena).
Chris@47: 
Chris@47: public:
Chris@47:   Orphan() = default;
Chris@47:   KJ_DISALLOW_COPY(Orphan);
Chris@47:   Orphan(Orphan&&) = default;
Chris@47:   Orphan& operator=(Orphan&&) = default;
Chris@47:   inline Orphan(_::OrphanBuilder&& builder): builder(kj::mv(builder)) {}
Chris@47: 
Chris@47:   inline BuilderFor<T> get();
Chris@47:   // Get the underlying builder.  If the orphan is null, this will allocate and return a default
Chris@47:   // object rather than crash.  This is done for security -- otherwise, you might enable a DoS
Chris@47:   // attack any time you disown a field and fail to check if it is null.  In the case of structs,
Chris@47:   // this means that the orphan is no longer null after get() returns.  In the case of lists,
Chris@47:   // no actual object is allocated since a simple empty ListBuilder can be returned.
Chris@47: 
Chris@47:   inline ReaderFor<T> getReader() const;
Chris@47: 
Chris@47:   inline bool operator==(decltype(nullptr)) const { return builder == nullptr; }
Chris@47:   inline bool operator!=(decltype(nullptr)) const { return builder != nullptr; }
Chris@47: 
Chris@47:   inline void truncate(uint size);
Chris@47:   // Resize an object (which must be a list or a blob) to the given size.
Chris@47:   //
Chris@47:   // If the new size is less than the original, the remaining elements will be discarded. The
Chris@47:   // list is never moved in this case. If the list happens to be located at the end of its segment
Chris@47:   // (which is always true if the list was the last thing allocated), the removed memory will be
Chris@47:   // reclaimed (reducing the messag size), otherwise it is simply zeroed. The reclaiming behavior
Chris@47:   // is particularly useful for allocating buffer space when you aren't sure how much space you
Chris@47:   // actually need: you can pre-allocate, say, a 4k byte array, read() from a file into it, and
Chris@47:   // then truncate it back to the amount of space actually used.
Chris@47:   //
Chris@47:   // If the new size is greater than the original, the list is extended with default values. If
Chris@47:   // the list is the last object in its segment *and* there is enough space left in the segment to
Chris@47:   // extend it to cover the new values, then the list is extended in-place. Otherwise, it must be
Chris@47:   // moved to a new location, leaving a zero'd hole in the previous space that won't be filled.
Chris@47:   // This copy is shallow; sub-objects will simply be reparented, not copied.
Chris@47:   //
Chris@47:   // Any existing readers or builders pointing at the object are invalidated by this call (even if
Chris@47:   // it doesn't move). You must call `get()` or `getReader()` again to get the new, valid pointer.
Chris@47: 
Chris@47: private:
Chris@47:   _::OrphanBuilder builder;
Chris@47: 
Chris@47:   template <typename, Kind>
Chris@47:   friend struct _::PointerHelpers;
Chris@47:   template <typename, Kind>
Chris@47:   friend struct List;
Chris@47:   template <typename U>
Chris@47:   friend class Orphan;
Chris@47:   friend class Orphanage;
Chris@47:   friend class MessageBuilder;
Chris@47: };
Chris@47: 
Chris@47: class Orphanage: private kj::DisallowConstCopy {
Chris@47:   // Use to directly allocate Orphan objects, without having a parent object allocate and then
Chris@47:   // disown the object.
Chris@47: 
Chris@47: public:
Chris@47:   inline Orphanage(): arena(nullptr) {}
Chris@47: 
Chris@47:   template <typename BuilderType>
Chris@47:   static Orphanage getForMessageContaining(BuilderType builder);
Chris@47:   // Construct an Orphanage that allocates within the message containing the given Builder.  This
Chris@47:   // allows the constructed Orphans to be adopted by objects within said message.
Chris@47:   //
Chris@47:   // This constructor takes the builder rather than having the builder have a getOrphanage() method
Chris@47:   // because this is an advanced feature and we don't want to pollute the builder APIs with it.
Chris@47:   //
Chris@47:   // Note that if you have a direct pointer to the `MessageBuilder`, you can simply call its
Chris@47:   // `getOrphanage()` method.
Chris@47: 
Chris@47:   template <typename RootType>
Chris@47:   Orphan<RootType> newOrphan() const;
Chris@47:   // Allocate a new orphaned struct.
Chris@47: 
Chris@47:   template <typename RootType>
Chris@47:   Orphan<RootType> newOrphan(uint size) const;
Chris@47:   // Allocate a new orphaned list or blob.
Chris@47: 
Chris@47:   Orphan<DynamicStruct> newOrphan(StructSchema schema) const;
Chris@47:   // Dynamically create an orphan struct with the given schema.  You must
Chris@47:   // #include <capnp/dynamic.h> to use this.
Chris@47: 
Chris@47:   Orphan<DynamicList> newOrphan(ListSchema schema, uint size) const;
Chris@47:   // Dynamically create an orphan list with the given schema.  You must #include <capnp/dynamic.h>
Chris@47:   // to use this.
Chris@47: 
Chris@47:   template <typename Reader>
Chris@47:   Orphan<FromReader<Reader>> newOrphanCopy(Reader copyFrom) const;
Chris@47:   // Allocate a new orphaned object (struct, list, or blob) and initialize it as a copy of the
Chris@47:   // given object.
Chris@47: 
Chris@47:   template <typename T>
Chris@47:   Orphan<List<ListElementType<FromReader<T>>>> newOrphanConcat(kj::ArrayPtr<T> lists) const;
Chris@47:   template <typename T>
Chris@47:   Orphan<List<ListElementType<FromReader<T>>>> newOrphanConcat(kj::ArrayPtr<const T> lists) const;
Chris@47:   // Given an array of List readers, copy and concatenate the lists, creating a new Orphan.
Chris@47:   //
Chris@47:   // Note that compared to allocating the list yourself and using `setWithCaveats()` to set each
Chris@47:   // item, this method avoids the "caveats": the new list will be allocated with the element size
Chris@47:   // being the maximum of that from all the input lists. This is particularly important when
Chris@47:   // concatenating struct lists: if the lists were created using a newer version of the protocol
Chris@47:   // in which some new fields had been added to the struct, using `setWithCaveats()` would
Chris@47:   // truncate off those new fields.
Chris@47: 
Chris@47:   Orphan<Data> referenceExternalData(Data::Reader data) const;
Chris@47:   // Creates an Orphan<Data> that points at an existing region of memory (e.g. from another message)
Chris@47:   // without copying it.  There are some SEVERE restrictions on how this can be used:
Chris@47:   // - The memory must remain valid until the `MessageBuilder` is destroyed (even if the orphan is
Chris@47:   //   abandoned).
Chris@47:   // - Because the data is const, you will not be allowed to obtain a `Data::Builder`
Chris@47:   //   for this blob.  Any call which would return such a builder will throw an exception.  You
Chris@47:   //   can, however, obtain a Reader, e.g. via orphan.getReader() or from a parent Reader (once
Chris@47:   //   the orphan is adopted).  It is your responsibility to make sure your code can deal with
Chris@47:   //   these problems when using this optimization; if you can't, allocate a copy instead.
Chris@47:   // - `data.begin()` must be aligned to a machine word boundary (32-bit or 64-bit depending on
Chris@47:   //   the CPU).  Any pointer returned by malloc() as well as any data blob obtained from another
Chris@47:   //   Cap'n Proto message satisfies this.
Chris@47:   // - If `data.size()` is not a multiple of 8, extra bytes past data.end() up until the next 8-byte
Chris@47:   //   boundary will be visible in the raw message when it is written out.  Thus, there must be no
Chris@47:   //   secrets in these bytes.  Data blobs obtained from other Cap'n Proto messages should be safe
Chris@47:   //   as these bytes should be zero (unless the sender had the same problem).
Chris@47:   //
Chris@47:   // The array will actually become one of the message's segments.  The data can thus be adopted
Chris@47:   // into the message tree without copying it.  This is particularly useful when referencing very
Chris@47:   // large blobs, such as whole mmap'd files.
Chris@47: 
Chris@47: private:
Chris@47:   _::BuilderArena* arena;
Chris@47:   _::CapTableBuilder* capTable;
Chris@47: 
Chris@47:   inline explicit Orphanage(_::BuilderArena* arena, _::CapTableBuilder* capTable)
Chris@47:       : arena(arena), capTable(capTable) {}
Chris@47: 
Chris@47:   template <typename T, Kind = CAPNP_KIND(T)>
Chris@47:   struct GetInnerBuilder;
Chris@47:   template <typename T, Kind = CAPNP_KIND(T)>
Chris@47:   struct GetInnerReader;
Chris@47:   template <typename T>
Chris@47:   struct NewOrphanListImpl;
Chris@47: 
Chris@47:   friend class MessageBuilder;
Chris@47:   friend struct _::OrphanageInternal;
Chris@47: };
Chris@47: 
Chris@47: // =======================================================================================
Chris@47: // Inline implementation details.
Chris@47: 
Chris@47: namespace _ {  // private
Chris@47: 
Chris@47: template <typename T, Kind = CAPNP_KIND(T)>
Chris@47: struct OrphanGetImpl;
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct OrphanGetImpl<T, Kind::PRIMITIVE> {
Chris@47:   static inline void truncateListOf(_::OrphanBuilder& builder, ElementCount size) {
Chris@47:     builder.truncate(size, _::elementSizeForType<T>());
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct OrphanGetImpl<T, Kind::STRUCT> {
Chris@47:   static inline typename T::Builder apply(_::OrphanBuilder& builder) {
Chris@47:     return typename T::Builder(builder.asStruct(_::structSize<T>()));
Chris@47:   }
Chris@47:   static inline typename T::Reader applyReader(const _::OrphanBuilder& builder) {
Chris@47:     return typename T::Reader(builder.asStructReader(_::structSize<T>()));
Chris@47:   }
Chris@47:   static inline void truncateListOf(_::OrphanBuilder& builder, ElementCount size) {
Chris@47:     builder.truncate(size, _::structSize<T>());
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: #if !CAPNP_LITE
Chris@47: template <typename T>
Chris@47: struct OrphanGetImpl<T, Kind::INTERFACE> {
Chris@47:   static inline typename T::Client apply(_::OrphanBuilder& builder) {
Chris@47:     return typename T::Client(builder.asCapability());
Chris@47:   }
Chris@47:   static inline typename T::Client applyReader(const _::OrphanBuilder& builder) {
Chris@47:     return typename T::Client(builder.asCapability());
Chris@47:   }
Chris@47:   static inline void truncateListOf(_::OrphanBuilder& builder, ElementCount size) {
Chris@47:     builder.truncate(size, ElementSize::POINTER);
Chris@47:   }
Chris@47: };
Chris@47: #endif  // !CAPNP_LITE
Chris@47: 
Chris@47: template <typename T, Kind k>
Chris@47: struct OrphanGetImpl<List<T, k>, Kind::LIST> {
Chris@47:   static inline typename List<T>::Builder apply(_::OrphanBuilder& builder) {
Chris@47:     return typename List<T>::Builder(builder.asList(_::ElementSizeForType<T>::value));
Chris@47:   }
Chris@47:   static inline typename List<T>::Reader applyReader(const _::OrphanBuilder& builder) {
Chris@47:     return typename List<T>::Reader(builder.asListReader(_::ElementSizeForType<T>::value));
Chris@47:   }
Chris@47:   static inline void truncateListOf(_::OrphanBuilder& builder, ElementCount size) {
Chris@47:     builder.truncate(size, ElementSize::POINTER);
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct OrphanGetImpl<List<T, Kind::STRUCT>, Kind::LIST> {
Chris@47:   static inline typename List<T>::Builder apply(_::OrphanBuilder& builder) {
Chris@47:     return typename List<T>::Builder(builder.asStructList(_::structSize<T>()));
Chris@47:   }
Chris@47:   static inline typename List<T>::Reader applyReader(const _::OrphanBuilder& builder) {
Chris@47:     return typename List<T>::Reader(builder.asListReader(_::ElementSizeForType<T>::value));
Chris@47:   }
Chris@47:   static inline void truncateListOf(_::OrphanBuilder& builder, ElementCount size) {
Chris@47:     builder.truncate(size, ElementSize::POINTER);
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <>
Chris@47: struct OrphanGetImpl<Text, Kind::BLOB> {
Chris@47:   static inline Text::Builder apply(_::OrphanBuilder& builder) {
Chris@47:     return Text::Builder(builder.asText());
Chris@47:   }
Chris@47:   static inline Text::Reader applyReader(const _::OrphanBuilder& builder) {
Chris@47:     return Text::Reader(builder.asTextReader());
Chris@47:   }
Chris@47:   static inline void truncateListOf(_::OrphanBuilder& builder, ElementCount size) {
Chris@47:     builder.truncate(size, ElementSize::POINTER);
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <>
Chris@47: struct OrphanGetImpl<Data, Kind::BLOB> {
Chris@47:   static inline Data::Builder apply(_::OrphanBuilder& builder) {
Chris@47:     return Data::Builder(builder.asData());
Chris@47:   }
Chris@47:   static inline Data::Reader applyReader(const _::OrphanBuilder& builder) {
Chris@47:     return Data::Reader(builder.asDataReader());
Chris@47:   }
Chris@47:   static inline void truncateListOf(_::OrphanBuilder& builder, ElementCount size) {
Chris@47:     builder.truncate(size, ElementSize::POINTER);
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: struct OrphanageInternal {
Chris@47:   static inline _::BuilderArena* getArena(Orphanage orphanage) { return orphanage.arena; }
Chris@47:   static inline _::CapTableBuilder* getCapTable(Orphanage orphanage) { return orphanage.capTable; }
Chris@47: };
Chris@47: 
Chris@47: }  // namespace _ (private)
Chris@47: 
Chris@47: template <typename T>
Chris@47: inline BuilderFor<T> Orphan<T>::get() {
Chris@47:   return _::OrphanGetImpl<T>::apply(builder);
Chris@47: }
Chris@47: 
Chris@47: template <typename T>
Chris@47: inline ReaderFor<T> Orphan<T>::getReader() const {
Chris@47:   return _::OrphanGetImpl<T>::applyReader(builder);
Chris@47: }
Chris@47: 
Chris@47: template <typename T>
Chris@47: inline void Orphan<T>::truncate(uint size) {
Chris@47:   _::OrphanGetImpl<ListElementType<T>>::truncateListOf(builder, size * ELEMENTS);
Chris@47: }
Chris@47: 
Chris@47: template <>
Chris@47: inline void Orphan<Text>::truncate(uint size) {
Chris@47:   builder.truncateText(size * ELEMENTS);
Chris@47: }
Chris@47: 
Chris@47: template <>
Chris@47: inline void Orphan<Data>::truncate(uint size) {
Chris@47:   builder.truncate(size * ELEMENTS, ElementSize::BYTE);
Chris@47: }
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct Orphanage::GetInnerBuilder<T, Kind::STRUCT> {
Chris@47:   static inline _::StructBuilder apply(typename T::Builder& t) {
Chris@47:     return t._builder;
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct Orphanage::GetInnerBuilder<T, Kind::LIST> {
Chris@47:   static inline _::ListBuilder apply(typename T::Builder& t) {
Chris@47:     return t.builder;
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename BuilderType>
Chris@47: Orphanage Orphanage::getForMessageContaining(BuilderType builder) {
Chris@47:   auto inner = GetInnerBuilder<FromBuilder<BuilderType>>::apply(builder);
Chris@47:   return Orphanage(inner.getArena(), inner.getCapTable());
Chris@47: }
Chris@47: 
Chris@47: template <typename RootType>
Chris@47: Orphan<RootType> Orphanage::newOrphan() const {
Chris@47:   return Orphan<RootType>(_::OrphanBuilder::initStruct(arena, capTable, _::structSize<RootType>()));
Chris@47: }
Chris@47: 
Chris@47: template <typename T, Kind k>
Chris@47: struct Orphanage::NewOrphanListImpl<List<T, k>> {
Chris@47:   static inline _::OrphanBuilder apply(
Chris@47:       _::BuilderArena* arena, _::CapTableBuilder* capTable, uint size) {
Chris@47:     return _::OrphanBuilder::initList(
Chris@47:         arena, capTable, size * ELEMENTS, _::ElementSizeForType<T>::value);
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct Orphanage::NewOrphanListImpl<List<T, Kind::STRUCT>> {
Chris@47:   static inline _::OrphanBuilder apply(
Chris@47:       _::BuilderArena* arena, _::CapTableBuilder* capTable, uint size) {
Chris@47:     return _::OrphanBuilder::initStructList(
Chris@47:         arena, capTable, size * ELEMENTS, _::structSize<T>());
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <>
Chris@47: struct Orphanage::NewOrphanListImpl<Text> {
Chris@47:   static inline _::OrphanBuilder apply(
Chris@47:       _::BuilderArena* arena, _::CapTableBuilder* capTable, uint size) {
Chris@47:     return _::OrphanBuilder::initText(arena, capTable, size * BYTES);
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <>
Chris@47: struct Orphanage::NewOrphanListImpl<Data> {
Chris@47:   static inline _::OrphanBuilder apply(
Chris@47:       _::BuilderArena* arena, _::CapTableBuilder* capTable, uint size) {
Chris@47:     return _::OrphanBuilder::initData(arena, capTable, size * BYTES);
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename RootType>
Chris@47: Orphan<RootType> Orphanage::newOrphan(uint size) const {
Chris@47:   return Orphan<RootType>(NewOrphanListImpl<RootType>::apply(arena, capTable, size));
Chris@47: }
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct Orphanage::GetInnerReader<T, Kind::STRUCT> {
Chris@47:   static inline _::StructReader apply(const typename T::Reader& t) {
Chris@47:     return t._reader;
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct Orphanage::GetInnerReader<T, Kind::LIST> {
Chris@47:   static inline _::ListReader apply(const typename T::Reader& t) {
Chris@47:     return t.reader;
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename T>
Chris@47: struct Orphanage::GetInnerReader<T, Kind::BLOB> {
Chris@47:   static inline const typename T::Reader& apply(const typename T::Reader& t) {
Chris@47:     return t;
Chris@47:   }
Chris@47: };
Chris@47: 
Chris@47: template <typename Reader>
Chris@47: inline Orphan<FromReader<Reader>> Orphanage::newOrphanCopy(Reader copyFrom) const {
Chris@47:   return Orphan<FromReader<Reader>>(_::OrphanBuilder::copy(
Chris@47:       arena, capTable, GetInnerReader<FromReader<Reader>>::apply(copyFrom)));
Chris@47: }
Chris@47: 
Chris@47: template <typename T>
Chris@47: inline Orphan<List<ListElementType<FromReader<T>>>>
Chris@47: Orphanage::newOrphanConcat(kj::ArrayPtr<T> lists) const {
Chris@47:   return newOrphanConcat(kj::implicitCast<kj::ArrayPtr<const T>>(lists));
Chris@47: }
Chris@47: template <typename T>
Chris@47: inline Orphan<List<ListElementType<FromReader<T>>>>
Chris@47: Orphanage::newOrphanConcat(kj::ArrayPtr<const T> lists) const {
Chris@47:   // Optimization / simplification: Rely on List<T>::Reader containing nothing except a
Chris@47:   // _::ListReader.
Chris@47:   static_assert(sizeof(T) == sizeof(_::ListReader), "lists are not bare readers?");
Chris@47:   kj::ArrayPtr<const _::ListReader> raw(
Chris@47:       reinterpret_cast<const _::ListReader*>(lists.begin()), lists.size());
Chris@47:   typedef ListElementType<FromReader<T>> Element;
Chris@47:   return Orphan<List<Element>>(
Chris@47:       _::OrphanBuilder::concat(arena, capTable,
Chris@47:           _::elementSizeForType<Element>(),
Chris@47:           _::minStructSizeForElement<Element>(), raw));
Chris@47: }
Chris@47: 
Chris@47: inline Orphan<Data> Orphanage::referenceExternalData(Data::Reader data) const {
Chris@47:   return Orphan<Data>(_::OrphanBuilder::referenceExternalData(arena, data));
Chris@47: }
Chris@47: 
Chris@47: }  // namespace capnp
Chris@47: 
Chris@47: #endif  // CAPNP_ORPHAN_H_