comparison osx/include/capnp/orphan.h @ 49:3ab5a40c4e3b

Add Capnp and KJ builds for OSX

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