jpayne@69: // Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
jpayne@69: // Licensed under the MIT License:
jpayne@69: //
jpayne@69: // Permission is hereby granted, free of charge, to any person obtaining a copy
jpayne@69: // of this software and associated documentation files (the "Software"), to deal
jpayne@69: // in the Software without restriction, including without limitation the rights
jpayne@69: // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
jpayne@69: // copies of the Software, and to permit persons to whom the Software is
jpayne@69: // furnished to do so, subject to the following conditions:
jpayne@69: //
jpayne@69: // The above copyright notice and this permission notice shall be included in
jpayne@69: // all copies or substantial portions of the Software.
jpayne@69: //
jpayne@69: // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
jpayne@69: // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
jpayne@69: // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
jpayne@69: // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
jpayne@69: // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
jpayne@69: // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
jpayne@69: // THE SOFTWARE.
jpayne@69: 
jpayne@69: #pragma once
jpayne@69: 
jpayne@69: #include "memory.h"
jpayne@69: #include <string.h>
jpayne@69: #include <initializer_list>
jpayne@69: 
jpayne@69: KJ_BEGIN_HEADER
jpayne@69: 
jpayne@69: namespace kj {
jpayne@69: 
jpayne@69: // =======================================================================================
jpayne@69: // ArrayDisposer -- Implementation details.
jpayne@69: 
jpayne@69: class ArrayDisposer {
jpayne@69:   // Much like Disposer from memory.h.
jpayne@69: 
jpayne@69: protected:
jpayne@69:   // Do not declare a destructor, as doing so will force a global initializer for
jpayne@69:   // HeapArrayDisposer::instance.
jpayne@69: 
jpayne@69:   virtual void disposeImpl(void* firstElement, size_t elementSize, size_t elementCount,
jpayne@69:                            size_t capacity, void (*destroyElement)(void*)) const = 0;
jpayne@69:   // Disposes of the array.  `destroyElement` invokes the destructor of each element, or is nullptr
jpayne@69:   // if the elements have trivial destructors.  `capacity` is the amount of space that was
jpayne@69:   // allocated while `elementCount` is the number of elements that were actually constructed;
jpayne@69:   // these are always the same number for Array<T> but may be different when using ArrayBuilder<T>.
jpayne@69: 
jpayne@69: public:
jpayne@69: 
jpayne@69:   template <typename T>
jpayne@69:   void dispose(T* firstElement, size_t elementCount, size_t capacity) const;
jpayne@69:   // Helper wrapper around disposeImpl().
jpayne@69:   //
jpayne@69:   // Callers must not call dispose() on the same array twice, even if the first call throws
jpayne@69:   // an exception.
jpayne@69: 
jpayne@69: private:
jpayne@69:   template <typename T, bool hasTrivialDestructor = KJ_HAS_TRIVIAL_DESTRUCTOR(T)>
jpayne@69:   struct Dispose_;
jpayne@69: };
jpayne@69: 
jpayne@69: class ExceptionSafeArrayUtil {
jpayne@69:   // Utility class that assists in constructing or destroying elements of an array, where the
jpayne@69:   // constructor or destructor could throw exceptions.  In case of an exception,
jpayne@69:   // ExceptionSafeArrayUtil's destructor will call destructors on all elements that have been
jpayne@69:   // constructed but not destroyed.  Remember that destructors that throw exceptions are required
jpayne@69:   // to use UnwindDetector to detect unwind and avoid exceptions in this case.  Therefore, no more
jpayne@69:   // than one exception will be thrown (and the program will not terminate).
jpayne@69: 
jpayne@69: public:
jpayne@69:   inline ExceptionSafeArrayUtil(void* ptr, size_t elementSize, size_t constructedElementCount,
jpayne@69:                                 void (*destroyElement)(void*))
jpayne@69:       : pos(reinterpret_cast<byte*>(ptr) + elementSize * constructedElementCount),
jpayne@69:         elementSize(elementSize), constructedElementCount(constructedElementCount),
jpayne@69:         destroyElement(destroyElement) {}
jpayne@69:   KJ_DISALLOW_COPY_AND_MOVE(ExceptionSafeArrayUtil);
jpayne@69: 
jpayne@69:   inline ~ExceptionSafeArrayUtil() noexcept(false) {
jpayne@69:     if (constructedElementCount > 0) destroyAll();
jpayne@69:   }
jpayne@69: 
jpayne@69:   void construct(size_t count, void (*constructElement)(void*));
jpayne@69:   // Construct the given number of elements.
jpayne@69: 
jpayne@69:   void destroyAll();
jpayne@69:   // Destroy all elements.  Call this immediately before ExceptionSafeArrayUtil goes out-of-scope
jpayne@69:   // to ensure that one element throwing an exception does not prevent the others from being
jpayne@69:   // destroyed.
jpayne@69: 
jpayne@69:   void release() { constructedElementCount = 0; }
jpayne@69:   // Prevent ExceptionSafeArrayUtil's destructor from destroying the constructed elements.
jpayne@69:   // Call this after you've successfully finished constructing.
jpayne@69: 
jpayne@69: private:
jpayne@69:   byte* pos;
jpayne@69:   size_t elementSize;
jpayne@69:   size_t constructedElementCount;
jpayne@69:   void (*destroyElement)(void*);
jpayne@69: };
jpayne@69: 
jpayne@69: class DestructorOnlyArrayDisposer: public ArrayDisposer {
jpayne@69: public:
jpayne@69:   static const DestructorOnlyArrayDisposer instance;
jpayne@69: 
jpayne@69:   void disposeImpl(void* firstElement, size_t elementSize, size_t elementCount,
jpayne@69:                    size_t capacity, void (*destroyElement)(void*)) const override;
jpayne@69: };
jpayne@69: 
jpayne@69: class NullArrayDisposer: public ArrayDisposer {
jpayne@69:   // An ArrayDisposer that does nothing.  Can be used to construct a fake Arrays that doesn't
jpayne@69:   // actually own its content.
jpayne@69: 
jpayne@69: public:
jpayne@69:   static const NullArrayDisposer instance;
jpayne@69: 
jpayne@69:   void disposeImpl(void* firstElement, size_t elementSize, size_t elementCount,
jpayne@69:                    size_t capacity, void (*destroyElement)(void*)) const override;
jpayne@69: };
jpayne@69: 
jpayne@69: // =======================================================================================
jpayne@69: // Array
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: class Array {
jpayne@69:   // An owned array which will automatically be disposed of (using an ArrayDisposer) in the
jpayne@69:   // destructor.  Can be moved, but not copied.  Much like Own<T>, but for arrays rather than
jpayne@69:   // single objects.
jpayne@69: 
jpayne@69: public:
jpayne@69:   inline Array(): ptr(nullptr), size_(0), disposer(nullptr) {}
jpayne@69:   inline Array(decltype(nullptr)): ptr(nullptr), size_(0), disposer(nullptr) {}
jpayne@69:   inline Array(Array&& other) noexcept
jpayne@69:       : ptr(other.ptr), size_(other.size_), disposer(other.disposer) {
jpayne@69:     other.ptr = nullptr;
jpayne@69:     other.size_ = 0;
jpayne@69:   }
jpayne@69:   inline Array(Array<RemoveConstOrDisable<T>>&& other) noexcept
jpayne@69:       : ptr(other.ptr), size_(other.size_), disposer(other.disposer) {
jpayne@69:     other.ptr = nullptr;
jpayne@69:     other.size_ = 0;
jpayne@69:   }
jpayne@69:   inline Array(T* firstElement KJ_LIFETIMEBOUND, size_t size, const ArrayDisposer& disposer)
jpayne@69:       : ptr(firstElement), size_(size), disposer(&disposer) {}
jpayne@69: 
jpayne@69:   KJ_DISALLOW_COPY(Array);
jpayne@69:   inline ~Array() noexcept { dispose(); }
jpayne@69: 
jpayne@69:   inline operator ArrayPtr<T>() KJ_LIFETIMEBOUND {
jpayne@69:     return ArrayPtr<T>(ptr, size_);
jpayne@69:   }
jpayne@69:   inline operator ArrayPtr<const T>() const KJ_LIFETIMEBOUND {
jpayne@69:     return ArrayPtr<T>(ptr, size_);
jpayne@69:   }
jpayne@69:   inline ArrayPtr<T> asPtr() KJ_LIFETIMEBOUND {
jpayne@69:     return ArrayPtr<T>(ptr, size_);
jpayne@69:   }
jpayne@69:   inline ArrayPtr<const T> asPtr() const KJ_LIFETIMEBOUND {
jpayne@69:     return ArrayPtr<T>(ptr, size_);
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline size_t size() const { return size_; }
jpayne@69:   inline T& operator[](size_t index) KJ_LIFETIMEBOUND {
jpayne@69:     KJ_IREQUIRE(index < size_, "Out-of-bounds Array access.");
jpayne@69:     return ptr[index];
jpayne@69:   }
jpayne@69:   inline const T& operator[](size_t index) const KJ_LIFETIMEBOUND {
jpayne@69:     KJ_IREQUIRE(index < size_, "Out-of-bounds Array access.");
jpayne@69:     return ptr[index];
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline const T* begin() const KJ_LIFETIMEBOUND { return ptr; }
jpayne@69:   inline const T* end() const KJ_LIFETIMEBOUND { return ptr + size_; }
jpayne@69:   inline const T& front() const KJ_LIFETIMEBOUND { return *ptr; }
jpayne@69:   inline const T& back() const KJ_LIFETIMEBOUND { return *(ptr + size_ - 1); }
jpayne@69:   inline T* begin() KJ_LIFETIMEBOUND { return ptr; }
jpayne@69:   inline T* end() KJ_LIFETIMEBOUND { return ptr + size_; }
jpayne@69:   inline T& front() KJ_LIFETIMEBOUND { return *ptr; }
jpayne@69:   inline T& back() KJ_LIFETIMEBOUND { return *(ptr + size_ - 1); }
jpayne@69: 
jpayne@69:   template <typename U>
jpayne@69:   inline bool operator==(const U& other) const { return asPtr() == other; }
jpayne@69:   template <typename U>
jpayne@69:   inline bool operator!=(const U& other) const { return asPtr() != other; }
jpayne@69: 
jpayne@69:   inline ArrayPtr<T> slice(size_t start, size_t end) KJ_LIFETIMEBOUND {
jpayne@69:     KJ_IREQUIRE(start <= end && end <= size_, "Out-of-bounds Array::slice().");
jpayne@69:     return ArrayPtr<T>(ptr + start, end - start);
jpayne@69:   }
jpayne@69:   inline ArrayPtr<const T> slice(size_t start, size_t end) const KJ_LIFETIMEBOUND {
jpayne@69:     KJ_IREQUIRE(start <= end && end <= size_, "Out-of-bounds Array::slice().");
jpayne@69:     return ArrayPtr<const T>(ptr + start, end - start);
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline ArrayPtr<const byte> asBytes() const KJ_LIFETIMEBOUND { return asPtr().asBytes(); }
jpayne@69:   inline ArrayPtr<PropagateConst<T, byte>> asBytes() KJ_LIFETIMEBOUND { return asPtr().asBytes(); }
jpayne@69:   inline ArrayPtr<const char> asChars() const KJ_LIFETIMEBOUND { return asPtr().asChars(); }
jpayne@69:   inline ArrayPtr<PropagateConst<T, char>> asChars() KJ_LIFETIMEBOUND { return asPtr().asChars(); }
jpayne@69: 
jpayne@69:   inline Array<PropagateConst<T, byte>> releaseAsBytes() {
jpayne@69:     // Like asBytes() but transfers ownership.
jpayne@69:     static_assert(sizeof(T) == sizeof(byte),
jpayne@69:         "releaseAsBytes() only possible on arrays with byte-size elements (e.g. chars).");
jpayne@69:     Array<PropagateConst<T, byte>> result(
jpayne@69:         reinterpret_cast<PropagateConst<T, byte>*>(ptr), size_, *disposer);
jpayne@69:     ptr = nullptr;
jpayne@69:     size_ = 0;
jpayne@69:     return result;
jpayne@69:   }
jpayne@69:   inline Array<PropagateConst<T, char>> releaseAsChars() {
jpayne@69:     // Like asChars() but transfers ownership.
jpayne@69:     static_assert(sizeof(T) == sizeof(PropagateConst<T, char>),
jpayne@69:         "releaseAsChars() only possible on arrays with char-size elements (e.g. bytes).");
jpayne@69:     Array<PropagateConst<T, char>> result(
jpayne@69:         reinterpret_cast<PropagateConst<T, char>*>(ptr), size_, *disposer);
jpayne@69:     ptr = nullptr;
jpayne@69:     size_ = 0;
jpayne@69:     return result;
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline bool operator==(decltype(nullptr)) const { return size_ == 0; }
jpayne@69:   inline bool operator!=(decltype(nullptr)) const { return size_ != 0; }
jpayne@69: 
jpayne@69:   inline Array& operator=(decltype(nullptr)) {
jpayne@69:     dispose();
jpayne@69:     return *this;
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline Array& operator=(Array&& other) {
jpayne@69:     dispose();
jpayne@69:     ptr = other.ptr;
jpayne@69:     size_ = other.size_;
jpayne@69:     disposer = other.disposer;
jpayne@69:     other.ptr = nullptr;
jpayne@69:     other.size_ = 0;
jpayne@69:     return *this;
jpayne@69:   }
jpayne@69: 
jpayne@69:   template <typename... Attachments>
jpayne@69:   Array<T> attach(Attachments&&... attachments) KJ_WARN_UNUSED_RESULT;
jpayne@69:   // Like Own<T>::attach(), but attaches to an Array.
jpayne@69: 
jpayne@69: private:
jpayne@69:   T* ptr;
jpayne@69:   size_t size_;
jpayne@69:   const ArrayDisposer* disposer;
jpayne@69: 
jpayne@69:   inline void dispose() {
jpayne@69:     // Make sure that if an exception is thrown, we are left with a null ptr, so we won't possibly
jpayne@69:     // dispose again.
jpayne@69:     T* ptrCopy = ptr;
jpayne@69:     size_t sizeCopy = size_;
jpayne@69:     if (ptrCopy != nullptr) {
jpayne@69:       ptr = nullptr;
jpayne@69:       size_ = 0;
jpayne@69:       disposer->dispose(ptrCopy, sizeCopy, sizeCopy);
jpayne@69:     }
jpayne@69:   }
jpayne@69: 
jpayne@69:   template <typename U>
jpayne@69:   friend class Array;
jpayne@69:   template <typename U>
jpayne@69:   friend class ArrayBuilder;
jpayne@69: };
jpayne@69: 
jpayne@69: static_assert(!canMemcpy<Array<char>>(), "canMemcpy<>() is broken");
jpayne@69: 
jpayne@69: namespace _ {  // private
jpayne@69: 
jpayne@69: class HeapArrayDisposer final: public ArrayDisposer {
jpayne@69: public:
jpayne@69:   template <typename T>
jpayne@69:   static T* allocate(size_t count);
jpayne@69:   template <typename T>
jpayne@69:   static T* allocateUninitialized(size_t count);
jpayne@69: 
jpayne@69:   static const HeapArrayDisposer instance;
jpayne@69: 
jpayne@69: private:
jpayne@69:   static void* allocateImpl(size_t elementSize, size_t elementCount, size_t capacity,
jpayne@69:                             void (*constructElement)(void*), void (*destroyElement)(void*));
jpayne@69:   // Allocates and constructs the array.  Both function pointers are null if the constructor is
jpayne@69:   // trivial, otherwise destroyElement is null if the constructor doesn't throw.
jpayne@69: 
jpayne@69:   virtual void disposeImpl(void* firstElement, size_t elementSize, size_t elementCount,
jpayne@69:                            size_t capacity, void (*destroyElement)(void*)) const override;
jpayne@69: 
jpayne@69:   template <typename T, bool hasTrivialConstructor = KJ_HAS_TRIVIAL_CONSTRUCTOR(T),
jpayne@69:                         bool hasNothrowConstructor = KJ_HAS_NOTHROW_CONSTRUCTOR(T)>
jpayne@69:   struct Allocate_;
jpayne@69: };
jpayne@69: 
jpayne@69: }  // namespace _ (private)
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: inline Array<T> heapArray(size_t size) {
jpayne@69:   // Much like `heap<T>()` from memory.h, allocates a new array on the heap.
jpayne@69: 
jpayne@69:   return Array<T>(_::HeapArrayDisposer::allocate<T>(size), size,
jpayne@69:                   _::HeapArrayDisposer::instance);
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T> Array<T> heapArray(const T* content, size_t size);
jpayne@69: template <typename T> Array<T> heapArray(ArrayPtr<T> content);
jpayne@69: template <typename T> Array<T> heapArray(ArrayPtr<const T> content);
jpayne@69: template <typename T, typename Iterator> Array<T> heapArray(Iterator begin, Iterator end);
jpayne@69: template <typename T> Array<T> heapArray(std::initializer_list<T> init);
jpayne@69: // Allocate a heap array containing a copy of the given content.
jpayne@69: 
jpayne@69: template <typename T, typename Container>
jpayne@69: Array<T> heapArrayFromIterable(Container&& a) { return heapArray<T>(a.begin(), a.end()); }
jpayne@69: template <typename T>
jpayne@69: Array<T> heapArrayFromIterable(Array<T>&& a) { return mv(a); }
jpayne@69: 
jpayne@69: // =======================================================================================
jpayne@69: // ArrayBuilder
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: class ArrayBuilder {
jpayne@69:   // Class which lets you build an Array<T> specifying the exact constructor arguments for each
jpayne@69:   // element, rather than starting by default-constructing them.
jpayne@69: 
jpayne@69: public:
jpayne@69:   ArrayBuilder(): ptr(nullptr), pos(nullptr), endPtr(nullptr) {}
jpayne@69:   ArrayBuilder(decltype(nullptr)): ptr(nullptr), pos(nullptr), endPtr(nullptr) {}
jpayne@69:   explicit ArrayBuilder(RemoveConst<T>* firstElement, size_t capacity,
jpayne@69:                         const ArrayDisposer& disposer)
jpayne@69:       : ptr(firstElement), pos(firstElement), endPtr(firstElement + capacity),
jpayne@69:         disposer(&disposer) {}
jpayne@69:   ArrayBuilder(ArrayBuilder&& other)
jpayne@69:       : ptr(other.ptr), pos(other.pos), endPtr(other.endPtr), disposer(other.disposer) {
jpayne@69:     other.ptr = nullptr;
jpayne@69:     other.pos = nullptr;
jpayne@69:     other.endPtr = nullptr;
jpayne@69:   }
jpayne@69:   ArrayBuilder(Array<T>&& other)
jpayne@69:       : ptr(other.ptr), pos(other.ptr + other.size_), endPtr(pos), disposer(other.disposer) {
jpayne@69:     // Create an already-full ArrayBuilder from an Array of the same type. This constructor
jpayne@69:     // primarily exists to enable Vector<T> to be constructed from Array<T>.
jpayne@69:     other.ptr = nullptr;
jpayne@69:     other.size_ = 0;
jpayne@69:   }
jpayne@69:   KJ_DISALLOW_COPY(ArrayBuilder);
jpayne@69:   inline ~ArrayBuilder() noexcept(false) { dispose(); }
jpayne@69: 
jpayne@69:   inline operator ArrayPtr<T>() KJ_LIFETIMEBOUND {
jpayne@69:     return arrayPtr(ptr, pos);
jpayne@69:   }
jpayne@69:   inline operator ArrayPtr<const T>() const KJ_LIFETIMEBOUND {
jpayne@69:     return arrayPtr(ptr, pos);
jpayne@69:   }
jpayne@69:   inline ArrayPtr<T> asPtr() KJ_LIFETIMEBOUND {
jpayne@69:     return arrayPtr(ptr, pos);
jpayne@69:   }
jpayne@69:   inline ArrayPtr<const T> asPtr() const KJ_LIFETIMEBOUND {
jpayne@69:     return arrayPtr(ptr, pos);
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline size_t size() const { return pos - ptr; }
jpayne@69:   inline size_t capacity() const { return endPtr - ptr; }
jpayne@69:   inline T& operator[](size_t index) KJ_LIFETIMEBOUND {
jpayne@69:     KJ_IREQUIRE(index < implicitCast<size_t>(pos - ptr), "Out-of-bounds Array access.");
jpayne@69:     return ptr[index];
jpayne@69:   }
jpayne@69:   inline const T& operator[](size_t index) const KJ_LIFETIMEBOUND {
jpayne@69:     KJ_IREQUIRE(index < implicitCast<size_t>(pos - ptr), "Out-of-bounds Array access.");
jpayne@69:     return ptr[index];
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline const T* begin() const KJ_LIFETIMEBOUND { return ptr; }
jpayne@69:   inline const T* end() const KJ_LIFETIMEBOUND { return pos; }
jpayne@69:   inline const T& front() const KJ_LIFETIMEBOUND { return *ptr; }
jpayne@69:   inline const T& back() const KJ_LIFETIMEBOUND { return *(pos - 1); }
jpayne@69:   inline T* begin() KJ_LIFETIMEBOUND { return ptr; }
jpayne@69:   inline T* end() KJ_LIFETIMEBOUND { return pos; }
jpayne@69:   inline T& front() KJ_LIFETIMEBOUND { return *ptr; }
jpayne@69:   inline T& back() KJ_LIFETIMEBOUND { return *(pos - 1); }
jpayne@69: 
jpayne@69:   ArrayBuilder& operator=(ArrayBuilder&& other) {
jpayne@69:     dispose();
jpayne@69:     ptr = other.ptr;
jpayne@69:     pos = other.pos;
jpayne@69:     endPtr = other.endPtr;
jpayne@69:     disposer = other.disposer;
jpayne@69:     other.ptr = nullptr;
jpayne@69:     other.pos = nullptr;
jpayne@69:     other.endPtr = nullptr;
jpayne@69:     return *this;
jpayne@69:   }
jpayne@69:   ArrayBuilder& operator=(decltype(nullptr)) {
jpayne@69:     dispose();
jpayne@69:     return *this;
jpayne@69:   }
jpayne@69: 
jpayne@69:   template <typename... Params>
jpayne@69:   T& add(Params&&... params) KJ_LIFETIMEBOUND {
jpayne@69:     KJ_IREQUIRE(pos < endPtr, "Added too many elements to ArrayBuilder.");
jpayne@69:     ctor(*pos, kj::fwd<Params>(params)...);
jpayne@69:     return *pos++;
jpayne@69:   }
jpayne@69: 
jpayne@69:   template <typename Container>
jpayne@69:   void addAll(Container&& container) {
jpayne@69:     addAll<decltype(container.begin()), !isReference<Container>()>(
jpayne@69:         container.begin(), container.end());
jpayne@69:   }
jpayne@69: 
jpayne@69:   template <typename Iterator, bool move = false>
jpayne@69:   void addAll(Iterator start, Iterator end);
jpayne@69: 
jpayne@69:   void removeLast() {
jpayne@69:     KJ_IREQUIRE(pos > ptr, "No elements present to remove.");
jpayne@69:     kj::dtor(*--pos);
jpayne@69:   }
jpayne@69: 
jpayne@69:   void truncate(size_t size) {
jpayne@69:     KJ_IREQUIRE(size <= this->size(), "can't use truncate() to expand");
jpayne@69: 
jpayne@69:     T* target = ptr + size;
jpayne@69:     if (KJ_HAS_TRIVIAL_DESTRUCTOR(T)) {
jpayne@69:       pos = target;
jpayne@69:     } else {
jpayne@69:       while (pos > target) {
jpayne@69:         kj::dtor(*--pos);
jpayne@69:       }
jpayne@69:     }
jpayne@69:   }
jpayne@69: 
jpayne@69:   void clear() {
jpayne@69:     if (KJ_HAS_TRIVIAL_DESTRUCTOR(T)) {
jpayne@69:       pos = ptr;
jpayne@69:     } else {
jpayne@69:       while (pos > ptr) {
jpayne@69:         kj::dtor(*--pos);
jpayne@69:       }
jpayne@69:     }
jpayne@69:   }
jpayne@69: 
jpayne@69:   void resize(size_t size) {
jpayne@69:     KJ_IREQUIRE(size <= capacity(), "can't resize past capacity");
jpayne@69: 
jpayne@69:     T* target = ptr + size;
jpayne@69:     if (target > pos) {
jpayne@69:       // expand
jpayne@69:       if (KJ_HAS_TRIVIAL_CONSTRUCTOR(T)) {
jpayne@69:         pos = target;
jpayne@69:       } else {
jpayne@69:         while (pos < target) {
jpayne@69:           kj::ctor(*pos++);
jpayne@69:         }
jpayne@69:       }
jpayne@69:     } else {
jpayne@69:       // truncate
jpayne@69:       if (KJ_HAS_TRIVIAL_DESTRUCTOR(T)) {
jpayne@69:         pos = target;
jpayne@69:       } else {
jpayne@69:         while (pos > target) {
jpayne@69:           kj::dtor(*--pos);
jpayne@69:         }
jpayne@69:       }
jpayne@69:     }
jpayne@69:   }
jpayne@69: 
jpayne@69:   Array<T> finish() {
jpayne@69:     // We could safely remove this check if we assume that the disposer implementation doesn't
jpayne@69:     // need to know the original capacity, as is the case with HeapArrayDisposer since it uses
jpayne@69:     // operator new() or if we created a custom disposer for ArrayBuilder which stores the capacity
jpayne@69:     // in a prefix.  But that would make it hard to write cleverer heap allocators, and anyway this
jpayne@69:     // check might catch bugs.  Probably people should use Vector if they want to build arrays
jpayne@69:     // without knowing the final size in advance.
jpayne@69:     KJ_IREQUIRE(pos == endPtr, "ArrayBuilder::finish() called prematurely.");
jpayne@69:     Array<T> result(reinterpret_cast<T*>(ptr), pos - ptr, *disposer);
jpayne@69:     ptr = nullptr;
jpayne@69:     pos = nullptr;
jpayne@69:     endPtr = nullptr;
jpayne@69:     return result;
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline bool isFull() const {
jpayne@69:     return pos == endPtr;
jpayne@69:   }
jpayne@69: 
jpayne@69: private:
jpayne@69:   T* ptr;
jpayne@69:   RemoveConst<T>* pos;
jpayne@69:   T* endPtr;
jpayne@69:   const ArrayDisposer* disposer = &NullArrayDisposer::instance;
jpayne@69: 
jpayne@69:   inline void dispose() {
jpayne@69:     // Make sure that if an exception is thrown, we are left with a null ptr, so we won't possibly
jpayne@69:     // dispose again.
jpayne@69:     T* ptrCopy = ptr;
jpayne@69:     T* posCopy = pos;
jpayne@69:     T* endCopy = endPtr;
jpayne@69:     if (ptrCopy != nullptr) {
jpayne@69:       ptr = nullptr;
jpayne@69:       pos = nullptr;
jpayne@69:       endPtr = nullptr;
jpayne@69:       disposer->dispose(ptrCopy, posCopy - ptrCopy, endCopy - ptrCopy);
jpayne@69:     }
jpayne@69:   }
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: inline ArrayBuilder<T> heapArrayBuilder(size_t size) {
jpayne@69:   // Like `heapArray<T>()` but does not default-construct the elements.  You must construct them
jpayne@69:   // manually by calling `add()`.
jpayne@69: 
jpayne@69:   return ArrayBuilder<T>(_::HeapArrayDisposer::allocateUninitialized<RemoveConst<T>>(size),
jpayne@69:                          size, _::HeapArrayDisposer::instance);
jpayne@69: }
jpayne@69: 
jpayne@69: // =======================================================================================
jpayne@69: // Inline Arrays
jpayne@69: 
jpayne@69: template <typename T, size_t fixedSize>
jpayne@69: class FixedArray {
jpayne@69:   // A fixed-width array whose storage is allocated inline rather than on the heap.
jpayne@69: 
jpayne@69: public:
jpayne@69:   inline constexpr size_t size() const { return fixedSize; }
jpayne@69:   inline constexpr T* begin() KJ_LIFETIMEBOUND { return content; }
jpayne@69:   inline constexpr T* end() KJ_LIFETIMEBOUND { return content + fixedSize; }
jpayne@69:   inline constexpr const T* begin() const KJ_LIFETIMEBOUND { return content; }
jpayne@69:   inline constexpr const T* end() const KJ_LIFETIMEBOUND { return content + fixedSize; }
jpayne@69: 
jpayne@69:   inline constexpr operator ArrayPtr<T>() KJ_LIFETIMEBOUND {
jpayne@69:     return arrayPtr(content, fixedSize);
jpayne@69:   }
jpayne@69:   inline constexpr operator ArrayPtr<const T>() const KJ_LIFETIMEBOUND {
jpayne@69:     return arrayPtr(content, fixedSize);
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline constexpr T& operator[](size_t index) KJ_LIFETIMEBOUND { return content[index]; }
jpayne@69:   inline constexpr const T& operator[](size_t index) const KJ_LIFETIMEBOUND {
jpayne@69:     return content[index];
jpayne@69:   }
jpayne@69: 
jpayne@69: private:
jpayne@69:   T content[fixedSize];
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T, size_t fixedSize>
jpayne@69: class CappedArray {
jpayne@69:   // Like `FixedArray` but can be dynamically resized as long as the size does not exceed the limit
jpayne@69:   // specified by the template parameter.
jpayne@69:   //
jpayne@69:   // TODO(someday):  Don't construct elements past currentSize?
jpayne@69: 
jpayne@69: public:
jpayne@69:   inline KJ_CONSTEXPR() CappedArray(): currentSize(fixedSize) {}
jpayne@69:   inline explicit constexpr CappedArray(size_t s): currentSize(s) {}
jpayne@69: 
jpayne@69:   inline size_t size() const { return currentSize; }
jpayne@69:   inline void setSize(size_t s) { KJ_IREQUIRE(s <= fixedSize); currentSize = s; }
jpayne@69:   inline T* begin() KJ_LIFETIMEBOUND { return content; }
jpayne@69:   inline T* end() KJ_LIFETIMEBOUND { return content + currentSize; }
jpayne@69:   inline const T* begin() const KJ_LIFETIMEBOUND { return content; }
jpayne@69:   inline const T* end() const KJ_LIFETIMEBOUND { return content + currentSize; }
jpayne@69: 
jpayne@69:   inline operator ArrayPtr<T>() KJ_LIFETIMEBOUND {
jpayne@69:     return arrayPtr(content, currentSize);
jpayne@69:   }
jpayne@69:   inline operator ArrayPtr<const T>() const KJ_LIFETIMEBOUND {
jpayne@69:     return arrayPtr(content, currentSize);
jpayne@69:   }
jpayne@69: 
jpayne@69:   inline T& operator[](size_t index) KJ_LIFETIMEBOUND { return content[index]; }
jpayne@69:   inline const T& operator[](size_t index) const KJ_LIFETIMEBOUND { return content[index]; }
jpayne@69: 
jpayne@69: private:
jpayne@69:   size_t currentSize;
jpayne@69:   T content[fixedSize];
jpayne@69: };
jpayne@69: 
jpayne@69: // =======================================================================================
jpayne@69: // KJ_MAP
jpayne@69: 
jpayne@69: #define KJ_MAP(elementName, array) \
jpayne@69:   ::kj::_::Mapper<KJ_DECLTYPE_REF(array)>(array) * \
jpayne@69:   [&](typename ::kj::_::Mapper<KJ_DECLTYPE_REF(array)>::Element elementName)
jpayne@69: // Applies some function to every element of an array, returning an Array of the results,  with
jpayne@69: // nice syntax.  Example:
jpayne@69: //
jpayne@69: //     StringPtr foo = "abcd";
jpayne@69: //     Array<char> bar = KJ_MAP(c, foo) -> char { return c + 1; };
jpayne@69: //     KJ_ASSERT(str(bar) == "bcde");
jpayne@69: 
jpayne@69: namespace _ {  // private
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: struct Mapper {
jpayne@69:   T array;
jpayne@69:   Mapper(T&& array): array(kj::fwd<T>(array)) {}
jpayne@69:   template <typename Func>
jpayne@69:   auto operator*(Func&& func) -> Array<decltype(func(*array.begin()))> {
jpayne@69:     auto builder = heapArrayBuilder<decltype(func(*array.begin()))>(array.size());
jpayne@69:     for (auto iter = array.begin(); iter != array.end(); ++iter) {
jpayne@69:       builder.add(func(*iter));
jpayne@69:     }
jpayne@69:     return builder.finish();
jpayne@69:   }
jpayne@69:   typedef decltype(*kj::instance<T>().begin()) Element;
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T, size_t s>
jpayne@69: struct Mapper<T(&)[s]> {
jpayne@69:   T* array;
jpayne@69:   Mapper(T* array): array(array) {}
jpayne@69:   template <typename Func>
jpayne@69:   auto operator*(Func&& func) -> Array<decltype(func(*array))> {
jpayne@69:     auto builder = heapArrayBuilder<decltype(func(*array))>(s);
jpayne@69:     for (size_t i = 0; i < s; i++) {
jpayne@69:       builder.add(func(array[i]));
jpayne@69:     }
jpayne@69:     return builder.finish();
jpayne@69:   }
jpayne@69:   typedef decltype(*array)& Element;
jpayne@69: };
jpayne@69: 
jpayne@69: }  // namespace _ (private)
jpayne@69: 
jpayne@69: // =======================================================================================
jpayne@69: // Inline implementation details
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: struct ArrayDisposer::Dispose_<T, true> {
jpayne@69:   static void dispose(T* firstElement, size_t elementCount, size_t capacity,
jpayne@69:                       const ArrayDisposer& disposer) {
jpayne@69:     disposer.disposeImpl(const_cast<RemoveConst<T>*>(firstElement),
jpayne@69:                          sizeof(T), elementCount, capacity, nullptr);
jpayne@69:   }
jpayne@69: };
jpayne@69: template <typename T>
jpayne@69: struct ArrayDisposer::Dispose_<T, false> {
jpayne@69:   static void destruct(void* ptr) {
jpayne@69:     kj::dtor(*reinterpret_cast<T*>(ptr));
jpayne@69:   }
jpayne@69: 
jpayne@69:   static void dispose(T* firstElement, size_t elementCount, size_t capacity,
jpayne@69:                       const ArrayDisposer& disposer) {
jpayne@69:     disposer.disposeImpl(const_cast<RemoveConst<T>*>(firstElement),
jpayne@69:                          sizeof(T), elementCount, capacity, &destruct);
jpayne@69:   }
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: void ArrayDisposer::dispose(T* firstElement, size_t elementCount, size_t capacity) const {
jpayne@69:   Dispose_<T>::dispose(firstElement, elementCount, capacity, *this);
jpayne@69: }
jpayne@69: 
jpayne@69: namespace _ {  // private
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: struct HeapArrayDisposer::Allocate_<T, true, true> {
jpayne@69:   static T* allocate(size_t elementCount, size_t capacity) {
jpayne@69:     return reinterpret_cast<T*>(allocateImpl(
jpayne@69:         sizeof(T), elementCount, capacity, nullptr, nullptr));
jpayne@69:   }
jpayne@69: };
jpayne@69: template <typename T>
jpayne@69: struct HeapArrayDisposer::Allocate_<T, false, true> {
jpayne@69:   static void construct(void* ptr) {
jpayne@69:     kj::ctor(*reinterpret_cast<T*>(ptr));
jpayne@69:   }
jpayne@69:   static T* allocate(size_t elementCount, size_t capacity) {
jpayne@69:     return reinterpret_cast<T*>(allocateImpl(
jpayne@69:         sizeof(T), elementCount, capacity, &construct, nullptr));
jpayne@69:   }
jpayne@69: };
jpayne@69: template <typename T>
jpayne@69: struct HeapArrayDisposer::Allocate_<T, false, false> {
jpayne@69:   static void construct(void* ptr) {
jpayne@69:     kj::ctor(*reinterpret_cast<T*>(ptr));
jpayne@69:   }
jpayne@69:   static void destruct(void* ptr) {
jpayne@69:     kj::dtor(*reinterpret_cast<T*>(ptr));
jpayne@69:   }
jpayne@69:   static T* allocate(size_t elementCount, size_t capacity) {
jpayne@69:     return reinterpret_cast<T*>(allocateImpl(
jpayne@69:         sizeof(T), elementCount, capacity, &construct, &destruct));
jpayne@69:   }
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: T* HeapArrayDisposer::allocate(size_t count) {
jpayne@69:   return Allocate_<T>::allocate(count, count);
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: T* HeapArrayDisposer::allocateUninitialized(size_t count) {
jpayne@69:   return Allocate_<T, true, true>::allocate(0, count);
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename Element, typename Iterator, bool move, bool = canMemcpy<Element>()>
jpayne@69: struct CopyConstructArray_;
jpayne@69: 
jpayne@69: template <typename T, bool move>
jpayne@69: struct CopyConstructArray_<T, T*, move, true> {
jpayne@69:   static inline T* apply(T* __restrict__ pos, T* start, T* end) {
jpayne@69:     if (end != start) {
jpayne@69:       memcpy(pos, start, reinterpret_cast<byte*>(end) - reinterpret_cast<byte*>(start));
jpayne@69:     }
jpayne@69:     return pos + (end - start);
jpayne@69:   }
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: struct CopyConstructArray_<T, const T*, false, true> {
jpayne@69:   static inline T* apply(T* __restrict__ pos, const T* start, const T* end) {
jpayne@69:     if (end != start) {
jpayne@69:       memcpy(pos, start, reinterpret_cast<const byte*>(end) - reinterpret_cast<const byte*>(start));
jpayne@69:     }
jpayne@69:     return pos + (end - start);
jpayne@69:   }
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T, typename Iterator, bool move>
jpayne@69: struct CopyConstructArray_<T, Iterator, move, true> {
jpayne@69:   static inline T* apply(T* __restrict__ pos, Iterator start, Iterator end) {
jpayne@69:     // Since both the copy constructor and assignment operator are trivial, we know that assignment
jpayne@69:     // is equivalent to copy-constructing.  So we can make this case somewhat easier for the
jpayne@69:     // compiler to optimize.
jpayne@69:     while (start != end) {
jpayne@69:       *pos++ = *start++;
jpayne@69:     }
jpayne@69:     return pos;
jpayne@69:   }
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T, typename Iterator>
jpayne@69: struct CopyConstructArray_<T, Iterator, false, false> {
jpayne@69:   struct ExceptionGuard {
jpayne@69:     T* start;
jpayne@69:     T* pos;
jpayne@69:     inline explicit ExceptionGuard(T* pos): start(pos), pos(pos) {}
jpayne@69:     ~ExceptionGuard() noexcept(false) {
jpayne@69:       while (pos > start) {
jpayne@69:         dtor(*--pos);
jpayne@69:       }
jpayne@69:     }
jpayne@69:   };
jpayne@69: 
jpayne@69:   static T* apply(T* __restrict__ pos, Iterator start, Iterator end) {
jpayne@69:     // Verify that T can be *implicitly* constructed from the source values.
jpayne@69:     if (false) implicitCast<T>(*start);
jpayne@69: 
jpayne@69:     if (noexcept(T(*start))) {
jpayne@69:       while (start != end) {
jpayne@69:         ctor(*pos++, *start++);
jpayne@69:       }
jpayne@69:       return pos;
jpayne@69:     } else {
jpayne@69:       // Crap.  This is complicated.
jpayne@69:       ExceptionGuard guard(pos);
jpayne@69:       while (start != end) {
jpayne@69:         ctor(*guard.pos, *start++);
jpayne@69:         ++guard.pos;
jpayne@69:       }
jpayne@69:       guard.start = guard.pos;
jpayne@69:       return guard.pos;
jpayne@69:     }
jpayne@69:   }
jpayne@69: };
jpayne@69: 
jpayne@69: template <typename T, typename Iterator>
jpayne@69: struct CopyConstructArray_<T, Iterator, true, false> {
jpayne@69:   // Actually move-construct.
jpayne@69: 
jpayne@69:   struct ExceptionGuard {
jpayne@69:     T* start;
jpayne@69:     T* pos;
jpayne@69:     inline explicit ExceptionGuard(T* pos): start(pos), pos(pos) {}
jpayne@69:     ~ExceptionGuard() noexcept(false) {
jpayne@69:       while (pos > start) {
jpayne@69:         dtor(*--pos);
jpayne@69:       }
jpayne@69:     }
jpayne@69:   };
jpayne@69: 
jpayne@69:   static T* apply(T* __restrict__ pos, Iterator start, Iterator end) {
jpayne@69:     // Verify that T can be *implicitly* constructed from the source values.
jpayne@69:     if (false) implicitCast<T>(kj::mv(*start));
jpayne@69: 
jpayne@69:     if (noexcept(T(kj::mv(*start)))) {
jpayne@69:       while (start != end) {
jpayne@69:         ctor(*pos++, kj::mv(*start++));
jpayne@69:       }
jpayne@69:       return pos;
jpayne@69:     } else {
jpayne@69:       // Crap.  This is complicated.
jpayne@69:       ExceptionGuard guard(pos);
jpayne@69:       while (start != end) {
jpayne@69:         ctor(*guard.pos, kj::mv(*start++));
jpayne@69:         ++guard.pos;
jpayne@69:       }
jpayne@69:       guard.start = guard.pos;
jpayne@69:       return guard.pos;
jpayne@69:     }
jpayne@69:   }
jpayne@69: };
jpayne@69: 
jpayne@69: }  // namespace _ (private)
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: template <typename Iterator, bool move>
jpayne@69: void ArrayBuilder<T>::addAll(Iterator start, Iterator end) {
jpayne@69:   pos = _::CopyConstructArray_<RemoveConst<T>, Decay<Iterator>, move>::apply(pos, start, end);
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: Array<T> heapArray(const T* content, size_t size) {
jpayne@69:   ArrayBuilder<T> builder = heapArrayBuilder<T>(size);
jpayne@69:   builder.addAll(content, content + size);
jpayne@69:   return builder.finish();
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: Array<T> heapArray(T* content, size_t size) {
jpayne@69:   ArrayBuilder<T> builder = heapArrayBuilder<T>(size);
jpayne@69:   builder.addAll(content, content + size);
jpayne@69:   return builder.finish();
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: Array<T> heapArray(ArrayPtr<T> content) {
jpayne@69:   ArrayBuilder<T> builder = heapArrayBuilder<T>(content.size());
jpayne@69:   builder.addAll(content);
jpayne@69:   return builder.finish();
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: Array<T> heapArray(ArrayPtr<const T> content) {
jpayne@69:   ArrayBuilder<T> builder = heapArrayBuilder<T>(content.size());
jpayne@69:   builder.addAll(content);
jpayne@69:   return builder.finish();
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T, typename Iterator> Array<T>
jpayne@69: heapArray(Iterator begin, Iterator end) {
jpayne@69:   ArrayBuilder<T> builder = heapArrayBuilder<T>(end - begin);
jpayne@69:   builder.addAll(begin, end);
jpayne@69:   return builder.finish();
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: inline Array<T> heapArray(std::initializer_list<T> init) {
jpayne@69:   return heapArray<T>(init.begin(), init.end());
jpayne@69: }
jpayne@69: 
jpayne@69: #if KJ_CPP_STD > 201402L
jpayne@69: template <typename T, typename... Params>
jpayne@69: inline Array<Decay<T>> arr(T&& param1, Params&&... params) {
jpayne@69:   ArrayBuilder<Decay<T>> builder = heapArrayBuilder<Decay<T>>(sizeof...(params) + 1);
jpayne@69:   (builder.add(kj::fwd<T>(param1)), ... , builder.add(kj::fwd<Params>(params)));
jpayne@69:   return builder.finish();
jpayne@69: }
jpayne@69: template <typename T, typename... Params>
jpayne@69: inline Array<Decay<T>> arrOf(Params&&... params) {
jpayne@69:   ArrayBuilder<Decay<T>> builder = heapArrayBuilder<Decay<T>>(sizeof...(params));
jpayne@69:   (... , builder.add(kj::fwd<Params>(params)));
jpayne@69:   return builder.finish();
jpayne@69: }
jpayne@69: #endif
jpayne@69: 
jpayne@69: namespace _ {  // private
jpayne@69: 
jpayne@69: template <typename... T>
jpayne@69: struct ArrayDisposableOwnedBundle final: public ArrayDisposer, public OwnedBundle<T...> {
jpayne@69:   ArrayDisposableOwnedBundle(T&&... values): OwnedBundle<T...>(kj::fwd<T>(values)...) {}
jpayne@69:   void disposeImpl(void*, size_t, size_t, size_t, void (*)(void*)) const override { delete this; }
jpayne@69: };
jpayne@69: 
jpayne@69: }  // namespace _ (private)
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: template <typename... Attachments>
jpayne@69: Array<T> Array<T>::attach(Attachments&&... attachments) {
jpayne@69:   T* ptrCopy = ptr;
jpayne@69:   auto sizeCopy = size_;
jpayne@69: 
jpayne@69:   KJ_IREQUIRE(ptrCopy != nullptr, "cannot attach to null pointer");
jpayne@69: 
jpayne@69:   // HACK: If someone accidentally calls .attach() on a null pointer in opt mode, try our best to
jpayne@69:   //   accomplish reasonable behavior: We turn the pointer non-null but still invalid, so that the
jpayne@69:   //   disposer will still be called when the pointer goes out of scope.
jpayne@69:   if (ptrCopy == nullptr) ptrCopy = reinterpret_cast<T*>(1);
jpayne@69: 
jpayne@69:   auto bundle = new _::ArrayDisposableOwnedBundle<Array<T>, Attachments...>(
jpayne@69:       kj::mv(*this), kj::fwd<Attachments>(attachments)...);
jpayne@69:   return Array<T>(ptrCopy, sizeCopy, *bundle);
jpayne@69: }
jpayne@69: 
jpayne@69: template <typename T>
jpayne@69: template <typename... Attachments>
jpayne@69: Array<T> ArrayPtr<T>::attach(Attachments&&... attachments) const {
jpayne@69:   T* ptrCopy = ptr;
jpayne@69: 
jpayne@69:   KJ_IREQUIRE(ptrCopy != nullptr, "cannot attach to null pointer");
jpayne@69: 
jpayne@69:   // HACK: If someone accidentally calls .attach() on a null pointer in opt mode, try our best to
jpayne@69:   //   accomplish reasonable behavior: We turn the pointer non-null but still invalid, so that the
jpayne@69:   //   disposer will still be called when the pointer goes out of scope.
jpayne@69:   if (ptrCopy == nullptr) ptrCopy = reinterpret_cast<T*>(1);
jpayne@69: 
jpayne@69:   auto bundle = new _::ArrayDisposableOwnedBundle<Attachments...>(
jpayne@69:       kj::fwd<Attachments>(attachments)...);
jpayne@69:   return Array<T>(ptrCopy, size_, *bundle);
jpayne@69: }
jpayne@69: 
jpayne@69: }  // namespace kj
jpayne@69: 
jpayne@69: KJ_END_HEADER