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