comparison osx/include/kj/array.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 KJ_ARRAY_H_
+#define KJ_ARRAY_H_
+
+#if defined(__GNUC__) && !KJ_HEADER_WARNINGS
+#pragma GCC system_header
+#endif
+
+#include "common.h"
+#include <string.h>
+#include <initializer_list>
+
+namespace kj {
+
+// =======================================================================================
+// ArrayDisposer -- Implementation details.
+
+class ArrayDisposer {
+  // Much like Disposer from memory.h.
+
+protected:
+  // Do not declare a destructor, as doing so will force a global initializer for
+  // HeapArrayDisposer::instance.
+
+  virtual void disposeImpl(void* firstElement, size_t elementSize, size_t elementCount,
+                           size_t capacity, void (*destroyElement)(void*)) const = 0;
+  // Disposes of the array.  `destroyElement` invokes the destructor of each element, or is nullptr
+  // if the elements have trivial destructors.  `capacity` is the amount of space that was
+  // allocated while `elementCount` is the number of elements that were actually constructed;
+  // these are always the same number for Array<T> but may be different when using ArrayBuilder<T>.
+
+public:
+
+  template <typename T>
+  void dispose(T* firstElement, size_t elementCount, size_t capacity) const;
+  // Helper wrapper around disposeImpl().
+  //
+  // Callers must not call dispose() on the same array twice, even if the first call throws
+  // an exception.
+
+private:
+  template <typename T, bool hasTrivialDestructor = __has_trivial_destructor(T)>
+  struct Dispose_;
+};
+
+class ExceptionSafeArrayUtil {
+  // Utility class that assists in constructing or destroying elements of an array, where the
+  // constructor or destructor could throw exceptions.  In case of an exception,
+  // ExceptionSafeArrayUtil's destructor will call destructors on all elements that have been
+  // constructed but not destroyed.  Remember that destructors that throw exceptions are required
+  // to use UnwindDetector to detect unwind and avoid exceptions in this case.  Therefore, no more
+  // than one exception will be thrown (and the program will not terminate).
+
+public:
+  inline ExceptionSafeArrayUtil(void* ptr, size_t elementSize, size_t constructedElementCount,
+                                void (*destroyElement)(void*))
+      : pos(reinterpret_cast<byte*>(ptr) + elementSize * constructedElementCount),
+        elementSize(elementSize), constructedElementCount(constructedElementCount),
+        destroyElement(destroyElement) {}
+  KJ_DISALLOW_COPY(ExceptionSafeArrayUtil);
+
+  inline ~ExceptionSafeArrayUtil() noexcept(false) {
+    if (constructedElementCount > 0) destroyAll();
+  }
+
+  void construct(size_t count, void (*constructElement)(void*));
+  // Construct the given number of elements.
+
+  void destroyAll();
+  // Destroy all elements.  Call this immediately before ExceptionSafeArrayUtil goes out-of-scope
+  // to ensure that one element throwing an exception does not prevent the others from being
+  // destroyed.
+
+  void release() { constructedElementCount = 0; }
+  // Prevent ExceptionSafeArrayUtil's destructor from destroying the constructed elements.
+  // Call this after you've successfully finished constructing.
+
+private:
+  byte* pos;
+  size_t elementSize;
+  size_t constructedElementCount;
+  void (*destroyElement)(void*);
+};
+
+class DestructorOnlyArrayDisposer: public ArrayDisposer {
+public:
+  static const DestructorOnlyArrayDisposer instance;
+
+  void disposeImpl(void* firstElement, size_t elementSize, size_t elementCount,
+                   size_t capacity, void (*destroyElement)(void*)) const override;
+};
+
+class NullArrayDisposer: public ArrayDisposer {
+  // An ArrayDisposer that does nothing.  Can be used to construct a fake Arrays that doesn't
+  // actually own its content.
+
+public:
+  static const NullArrayDisposer instance;
+
+  void disposeImpl(void* firstElement, size_t elementSize, size_t elementCount,
+                   size_t capacity, void (*destroyElement)(void*)) const override;
+};
+
+// =======================================================================================
+// Array
+
+template <typename T>
+class Array {
+  // An owned array which will automatically be disposed of (using an ArrayDisposer) in the
+  // destructor.  Can be moved, but not copied.  Much like Own<T>, but for arrays rather than
+  // single objects.
+
+public:
+  inline Array(): ptr(nullptr), size_(0), disposer(nullptr) {}
+  inline Array(decltype(nullptr)): ptr(nullptr), size_(0), disposer(nullptr) {}
+  inline Array(Array&& other) noexcept
+      : ptr(other.ptr), size_(other.size_), disposer(other.disposer) {
+    other.ptr = nullptr;
+    other.size_ = 0;
+  }
+  inline Array(Array<RemoveConstOrDisable<T>>&& other) noexcept
+      : ptr(other.ptr), size_(other.size_), disposer(other.disposer) {
+    other.ptr = nullptr;
+    other.size_ = 0;
+  }
+  inline Array(T* firstElement, size_t size, const ArrayDisposer& disposer)
+      : ptr(firstElement), size_(size), disposer(&disposer) {}
+
+  KJ_DISALLOW_COPY(Array);
+  inline ~Array() noexcept { dispose(); }
+
+  inline operator ArrayPtr<T>() {
+    return ArrayPtr<T>(ptr, size_);
+  }
+  inline operator ArrayPtr<const T>() const {
+    return ArrayPtr<T>(ptr, size_);
+  }
+  inline ArrayPtr<T> asPtr() {
+    return ArrayPtr<T>(ptr, size_);
+  }
+  inline ArrayPtr<const T> asPtr() const {
+    return ArrayPtr<T>(ptr, size_);
+  }
+
+  inline size_t size() const { return size_; }
+  inline T& operator[](size_t index) const {
+    KJ_IREQUIRE(index < size_, "Out-of-bounds Array access.");
+    return ptr[index];
+  }
+
+  inline const T* begin() const { return ptr; }
+  inline const T* end() const { return ptr + size_; }
+  inline const T& front() const { return *ptr; }
+  inline const T& back() const { return *(ptr + size_ - 1); }
+  inline T* begin() { return ptr; }
+  inline T* end() { return ptr + size_; }
+  inline T& front() { return *ptr; }
+  inline T& back() { return *(ptr + size_ - 1); }
+
+  inline ArrayPtr<T> slice(size_t start, size_t end) {
+    KJ_IREQUIRE(start <= end && end <= size_, "Out-of-bounds Array::slice().");
+    return ArrayPtr<T>(ptr + start, end - start);
+  }
+  inline ArrayPtr<const T> slice(size_t start, size_t end) const {
+    KJ_IREQUIRE(start <= end && end <= size_, "Out-of-bounds Array::slice().");
+    return ArrayPtr<const T>(ptr + start, end - start);
+  }
+
+  inline ArrayPtr<const byte> asBytes() const { return asPtr().asBytes(); }
+  inline ArrayPtr<PropagateConst<T, byte>> asBytes() { return asPtr().asBytes(); }
+  inline ArrayPtr<const char> asChars() const { return asPtr().asChars(); }
+  inline ArrayPtr<PropagateConst<T, char>> asChars() { return asPtr().asChars(); }
+
+  inline Array<PropagateConst<T, byte>> releaseAsBytes() {
+    // Like asBytes() but transfers ownership.
+    static_assert(sizeof(T) == sizeof(byte),
+        "releaseAsBytes() only possible on arrays with byte-size elements (e.g. chars).");
+    Array<PropagateConst<T, byte>> result(
+        reinterpret_cast<PropagateConst<T, byte>*>(ptr), size_, *disposer);
+    ptr = nullptr;
+    size_ = 0;
+    return result;
+  }
+  inline Array<PropagateConst<T, char>> releaseAsChars() {
+    // Like asChars() but transfers ownership.
+    static_assert(sizeof(T) == sizeof(PropagateConst<T, char>),
+        "releaseAsChars() only possible on arrays with char-size elements (e.g. bytes).");
+    Array<PropagateConst<T, char>> result(
+        reinterpret_cast<PropagateConst<T, char>*>(ptr), size_, *disposer);
+    ptr = nullptr;
+    size_ = 0;
+    return result;
+  }
+
+  inline bool operator==(decltype(nullptr)) const { return size_ == 0; }
+  inline bool operator!=(decltype(nullptr)) const { return size_ != 0; }
+
+  inline Array& operator=(decltype(nullptr)) {
+    dispose();
+    return *this;
+  }
+
+  inline Array& operator=(Array&& other) {
+    dispose();
+    ptr = other.ptr;
+    size_ = other.size_;
+    disposer = other.disposer;
+    other.ptr = nullptr;
+    other.size_ = 0;
+    return *this;
+  }
+
+private:
+  T* ptr;
+  size_t size_;
+  const ArrayDisposer* disposer;
+
+  inline void dispose() {
+    // Make sure that if an exception is thrown, we are left with a null ptr, so we won't possibly
+    // dispose again.
+    T* ptrCopy = ptr;
+    size_t sizeCopy = size_;
+    if (ptrCopy != nullptr) {
+      ptr = nullptr;
+      size_ = 0;
+      disposer->dispose(ptrCopy, sizeCopy, sizeCopy);
+    }
+  }
+
+  template <typename U>
+  friend class Array;
+};
+
+namespace _ {  // private
+
+class HeapArrayDisposer final: public ArrayDisposer {
+public:
+  template <typename T>
+  static T* allocate(size_t count);
+  template <typename T>
+  static T* allocateUninitialized(size_t count);
+
+  static const HeapArrayDisposer instance;
+
+private:
+  static void* allocateImpl(size_t elementSize, size_t elementCount, size_t capacity,
+                            void (*constructElement)(void*), void (*destroyElement)(void*));
+  // Allocates and constructs the array.  Both function pointers are null if the constructor is
+  // trivial, otherwise destroyElement is null if the constructor doesn't throw.
+
+  virtual void disposeImpl(void* firstElement, size_t elementSize, size_t elementCount,
+                           size_t capacity, void (*destroyElement)(void*)) const override;
+
+  template <typename T, bool hasTrivialConstructor = __has_trivial_constructor(T),
+                        bool hasNothrowConstructor = __has_nothrow_constructor(T)>
+  struct Allocate_;
+};
+
+}  // namespace _ (private)
+
+template <typename T>
+inline Array<T> heapArray(size_t size) {
+  // Much like `heap<T>()` from memory.h, allocates a new array on the heap.
+
+  return Array<T>(_::HeapArrayDisposer::allocate<T>(size), size,
+                  _::HeapArrayDisposer::instance);
+}
+
+template <typename T> Array<T> heapArray(const T* content, size_t size);
+template <typename T> Array<T> heapArray(ArrayPtr<T> content);
+template <typename T> Array<T> heapArray(ArrayPtr<const T> content);
+template <typename T, typename Iterator> Array<T> heapArray(Iterator begin, Iterator end);
+template <typename T> Array<T> heapArray(std::initializer_list<T> init);
+// Allocate a heap array containing a copy of the given content.
+
+template <typename T, typename Container>
+Array<T> heapArrayFromIterable(Container&& a) { return heapArray(a.begin(), a.end()); }
+template <typename T>
+Array<T> heapArrayFromIterable(Array<T>&& a) { return mv(a); }
+
+// =======================================================================================
+// ArrayBuilder
+
+template <typename T>
+class ArrayBuilder {
+  // Class which lets you build an Array<T> specifying the exact constructor arguments for each
+  // element, rather than starting by default-constructing them.
+
+public:
+  ArrayBuilder(): ptr(nullptr), pos(nullptr), endPtr(nullptr) {}
+  ArrayBuilder(decltype(nullptr)): ptr(nullptr), pos(nullptr), endPtr(nullptr) {}
+  explicit ArrayBuilder(RemoveConst<T>* firstElement, size_t capacity,
+                        const ArrayDisposer& disposer)
+      : ptr(firstElement), pos(firstElement), endPtr(firstElement + capacity),
+        disposer(&disposer) {}
+  ArrayBuilder(ArrayBuilder&& other)
+      : ptr(other.ptr), pos(other.pos), endPtr(other.endPtr), disposer(other.disposer) {
+    other.ptr = nullptr;
+    other.pos = nullptr;
+    other.endPtr = nullptr;
+  }
+  KJ_DISALLOW_COPY(ArrayBuilder);
+  inline ~ArrayBuilder() noexcept(false) { dispose(); }
+
+  inline operator ArrayPtr<T>() {
+    return arrayPtr(ptr, pos);
+  }
+  inline operator ArrayPtr<const T>() const {
+    return arrayPtr(ptr, pos);
+  }
+  inline ArrayPtr<T> asPtr() {
+    return arrayPtr(ptr, pos);
+  }
+  inline ArrayPtr<const T> asPtr() const {
+    return arrayPtr(ptr, pos);
+  }
+
+  inline size_t size() const { return pos - ptr; }
+  inline size_t capacity() const { return endPtr - ptr; }
+  inline T& operator[](size_t index) const {
+    KJ_IREQUIRE(index < implicitCast<size_t>(pos - ptr), "Out-of-bounds Array access.");
+    return ptr[index];
+  }
+
+  inline const T* begin() const { return ptr; }
+  inline const T* end() const { return pos; }
+  inline const T& front() const { return *ptr; }
+  inline const T& back() const { return *(pos - 1); }
+  inline T* begin() { return ptr; }
+  inline T* end() { return pos; }
+  inline T& front() { return *ptr; }
+  inline T& back() { return *(pos - 1); }
+
+  ArrayBuilder& operator=(ArrayBuilder&& other) {
+    dispose();
+    ptr = other.ptr;
+    pos = other.pos;
+    endPtr = other.endPtr;
+    disposer = other.disposer;
+    other.ptr = nullptr;
+    other.pos = nullptr;
+    other.endPtr = nullptr;
+    return *this;
+  }
+  ArrayBuilder& operator=(decltype(nullptr)) {
+    dispose();
+    return *this;
+  }
+
+  template <typename... Params>
+  T& add(Params&&... params) {
+    KJ_IREQUIRE(pos < endPtr, "Added too many elements to ArrayBuilder.");
+    ctor(*pos, kj::fwd<Params>(params)...);
+    return *pos++;
+  }
+
+  template <typename Container>
+  void addAll(Container&& container) {
+    addAll(container.begin(), container.end());
+  }
+
+  template <typename Iterator>
+  void addAll(Iterator start, Iterator end);
+
+  void removeLast() {
+    KJ_IREQUIRE(pos > ptr, "No elements present to remove.");
+    kj::dtor(*--pos);
+  }
+
+  Array<T> finish() {
+    // We could safely remove this check if we assume that the disposer implementation doesn't
+    // need to know the original capacity, as is thes case with HeapArrayDisposer since it uses
+    // operator new() or if we created a custom disposer for ArrayBuilder which stores the capacity
+    // in a prefix.  But that would make it hard to write cleverer heap allocators, and anyway this
+    // check might catch bugs.  Probably people should use Vector if they want to build arrays
+    // without knowing the final size in advance.
+    KJ_IREQUIRE(pos == endPtr, "ArrayBuilder::finish() called prematurely.");
+    Array<T> result(reinterpret_cast<T*>(ptr), pos - ptr, *disposer);
+    ptr = nullptr;
+    pos = nullptr;
+    endPtr = nullptr;
+    return result;
+  }
+
+  inline bool isFull() const {
+    return pos == endPtr;
+  }
+
+private:
+  T* ptr;
+  RemoveConst<T>* pos;
+  T* endPtr;
+  const ArrayDisposer* disposer;
+
+  inline void dispose() {
+    // Make sure that if an exception is thrown, we are left with a null ptr, so we won't possibly
+    // dispose again.
+    T* ptrCopy = ptr;
+    T* posCopy = pos;
+    T* endCopy = endPtr;
+    if (ptrCopy != nullptr) {
+      ptr = nullptr;
+      pos = nullptr;
+      endPtr = nullptr;
+      disposer->dispose(ptrCopy, posCopy - ptrCopy, endCopy - ptrCopy);
+    }
+  }
+};
+
+template <typename T>
+inline ArrayBuilder<T> heapArrayBuilder(size_t size) {
+  // Like `heapArray<T>()` but does not default-construct the elements.  You must construct them
+  // manually by calling `add()`.
+
+  return ArrayBuilder<T>(_::HeapArrayDisposer::allocateUninitialized<RemoveConst<T>>(size),
+                         size, _::HeapArrayDisposer::instance);
+}
+
+// =======================================================================================
+// Inline Arrays
+
+template <typename T, size_t fixedSize>
+class FixedArray {
+  // A fixed-width array whose storage is allocated inline rather than on the heap.
+
+public:
+  inline size_t size() const { return fixedSize; }
+  inline T* begin() { return content; }
+  inline T* end() { return content + fixedSize; }
+  inline const T* begin() const { return content; }
+  inline const T* end() const { return content + fixedSize; }
+
+  inline operator ArrayPtr<T>() {
+    return arrayPtr(content, fixedSize);
+  }
+  inline operator ArrayPtr<const T>() const {
+    return arrayPtr(content, fixedSize);
+  }
+
+  inline T& operator[](size_t index) { return content[index]; }
+  inline const T& operator[](size_t index) const { return content[index]; }
+
+private:
+  T content[fixedSize];
+};
+
+template <typename T, size_t fixedSize>
+class CappedArray {
+  // Like `FixedArray` but can be dynamically resized as long as the size does not exceed the limit
+  // specified by the template parameter.
+  //
+  // TODO(someday):  Don't construct elements past currentSize?
+
+public:
+  inline KJ_CONSTEXPR() CappedArray(): currentSize(fixedSize) {}
+  inline explicit constexpr CappedArray(size_t s): currentSize(s) {}
+
+  inline size_t size() const { return currentSize; }
+  inline void setSize(size_t s) { KJ_IREQUIRE(s <= fixedSize); currentSize = s; }
+  inline T* begin() { return content; }
+  inline T* end() { return content + currentSize; }
+  inline const T* begin() const { return content; }
+  inline const T* end() const { return content + currentSize; }
+
+  inline operator ArrayPtr<T>() {
+    return arrayPtr(content, currentSize);
+  }
+  inline operator ArrayPtr<const T>() const {
+    return arrayPtr(content, currentSize);
+  }
+
+  inline T& operator[](size_t index) { return content[index]; }
+  inline const T& operator[](size_t index) const { return content[index]; }
+
+private:
+  size_t currentSize;
+  T content[fixedSize];
+};
+
+// =======================================================================================
+// KJ_MAP
+
+#define KJ_MAP(elementName, array) \
+  ::kj::_::Mapper<KJ_DECLTYPE_REF(array)>(array) * [&](decltype(*(array).begin()) elementName)
+// Applies some function to every element of an array, returning an Array of the results,  with
+// nice syntax.  Example:
+//
+//     StringPtr foo = "abcd";
+//     Array<char> bar = KJ_MAP(c, foo) -> char { return c + 1; };
+//     KJ_ASSERT(str(bar) == "bcde");
+
+namespace _ {  // private
+
+template <typename T>
+struct Mapper {
+  T array;
+  Mapper(T&& array): array(kj::fwd<T>(array)) {}
+  template <typename Func>
+  auto operator*(Func&& func) -> Array<decltype(func(*array.begin()))> {
+    auto builder = heapArrayBuilder<decltype(func(*array.begin()))>(array.size());
+    for (auto iter = array.begin(); iter != array.end(); ++iter) {
+      builder.add(func(*iter));
+    }
+    return builder.finish();
+  }
+};
+
+}  // namespace _ (private)
+
+// =======================================================================================
+// Inline implementation details
+
+template <typename T>
+struct ArrayDisposer::Dispose_<T, true> {
+  static void dispose(T* firstElement, size_t elementCount, size_t capacity,
+                      const ArrayDisposer& disposer) {
+    disposer.disposeImpl(const_cast<RemoveConst<T>*>(firstElement),
+                         sizeof(T), elementCount, capacity, nullptr);
+  }
+};
+template <typename T>
+struct ArrayDisposer::Dispose_<T, false> {
+  static void destruct(void* ptr) {
+    kj::dtor(*reinterpret_cast<T*>(ptr));
+  }
+
+  static void dispose(T* firstElement, size_t elementCount, size_t capacity,
+                      const ArrayDisposer& disposer) {
+    disposer.disposeImpl(firstElement, sizeof(T), elementCount, capacity, &destruct);
+  }
+};
+
+template <typename T>
+void ArrayDisposer::dispose(T* firstElement, size_t elementCount, size_t capacity) const {
+  Dispose_<T>::dispose(firstElement, elementCount, capacity, *this);
+}
+
+namespace _ {  // private
+
+template <typename T>
+struct HeapArrayDisposer::Allocate_<T, true, true> {
+  static T* allocate(size_t elementCount, size_t capacity) {
+    return reinterpret_cast<T*>(allocateImpl(
+        sizeof(T), elementCount, capacity, nullptr, nullptr));
+  }
+};
+template <typename T>
+struct HeapArrayDisposer::Allocate_<T, false, true> {
+  static void construct(void* ptr) {
+    kj::ctor(*reinterpret_cast<T*>(ptr));
+  }
+  static T* allocate(size_t elementCount, size_t capacity) {
+    return reinterpret_cast<T*>(allocateImpl(
+        sizeof(T), elementCount, capacity, &construct, nullptr));
+  }
+};
+template <typename T>
+struct HeapArrayDisposer::Allocate_<T, false, false> {
+  static void construct(void* ptr) {
+    kj::ctor(*reinterpret_cast<T*>(ptr));
+  }
+  static void destruct(void* ptr) {
+    kj::dtor(*reinterpret_cast<T*>(ptr));
+  }
+  static T* allocate(size_t elementCount, size_t capacity) {
+    return reinterpret_cast<T*>(allocateImpl(
+        sizeof(T), elementCount, capacity, &construct, &destruct));
+  }
+};
+
+template <typename T>
+T* HeapArrayDisposer::allocate(size_t count) {
+  return Allocate_<T>::allocate(count, count);
+}
+
+template <typename T>
+T* HeapArrayDisposer::allocateUninitialized(size_t count) {
+  return Allocate_<T, true, true>::allocate(0, count);
+}
+
+template <typename Element, typename Iterator, bool = canMemcpy<Element>()>
+struct CopyConstructArray_;
+
+template <typename T>
+struct CopyConstructArray_<T, T*, true> {
+  static inline T* apply(T* __restrict__ pos, T* start, T* end) {
+    memcpy(pos, start, reinterpret_cast<byte*>(end) - reinterpret_cast<byte*>(start));
+    return pos + (end - start);
+  }
+};
+
+template <typename T>
+struct CopyConstructArray_<T, const T*, true> {
+  static inline T* apply(T* __restrict__ pos, const T* start, const T* end) {
+    memcpy(pos, start, reinterpret_cast<const byte*>(end) - reinterpret_cast<const byte*>(start));
+    return pos + (end - start);
+  }
+};
+
+template <typename T, typename Iterator>
+struct CopyConstructArray_<T, Iterator, true> {
+  static inline T* apply(T* __restrict__ pos, Iterator start, Iterator end) {
+    // Since both the copy constructor and assignment operator are trivial, we know that assignment
+    // is equivalent to copy-constructing.  So we can make this case somewhat easier for the
+    // compiler to optimize.
+    while (start != end) {
+      *pos++ = *start++;
+    }
+    return pos;
+  }
+};
+
+template <typename T, typename Iterator>
+struct CopyConstructArray_<T, Iterator, false> {
+  struct ExceptionGuard {
+    T* start;
+    T* pos;
+    inline explicit ExceptionGuard(T* pos): start(pos), pos(pos) {}
+    ~ExceptionGuard() noexcept(false) {
+      while (pos > start) {
+        dtor(*--pos);
+      }
+    }
+  };
+
+  static T* apply(T* __restrict__ pos, Iterator start, Iterator end) {
+    // Verify that T can be *implicitly* constructed from the source values.
+    if (false) implicitCast<T>(*start);
+
+    if (noexcept(T(*start))) {
+      while (start != end) {
+        ctor(*pos++, *start++);
+      }
+      return pos;
+    } else {
+      // Crap.  This is complicated.
+      ExceptionGuard guard(pos);
+      while (start != end) {
+        ctor(*guard.pos, *start++);
+        ++guard.pos;
+      }
+      guard.start = guard.pos;
+      return guard.pos;
+    }
+  }
+};
+
+template <typename T, typename Iterator>
+inline T* copyConstructArray(T* dst, Iterator start, Iterator end) {
+  return CopyConstructArray_<T, Decay<Iterator>>::apply(dst, start, end);
+}
+
+}  // namespace _ (private)
+
+template <typename T>
+template <typename Iterator>
+void ArrayBuilder<T>::addAll(Iterator start, Iterator end) {
+  pos = _::copyConstructArray(pos, start, end);
+}
+
+template <typename T>
+Array<T> heapArray(const T* content, size_t size) {
+  ArrayBuilder<T> builder = heapArrayBuilder<T>(size);
+  builder.addAll(content, content + size);
+  return builder.finish();
+}
+
+template <typename T>
+Array<T> heapArray(T* content, size_t size) {
+  ArrayBuilder<T> builder = heapArrayBuilder<T>(size);
+  builder.addAll(content, content + size);
+  return builder.finish();
+}
+
+template <typename T>
+Array<T> heapArray(ArrayPtr<T> content) {
+  ArrayBuilder<T> builder = heapArrayBuilder<T>(content.size());
+  builder.addAll(content);
+  return builder.finish();
+}
+
+template <typename T>
+Array<T> heapArray(ArrayPtr<const T> content) {
+  ArrayBuilder<T> builder = heapArrayBuilder<T>(content.size());
+  builder.addAll(content);
+  return builder.finish();
+}
+
+template <typename T, typename Iterator> Array<T>
+heapArray(Iterator begin, Iterator end) {
+  ArrayBuilder<T> builder = heapArrayBuilder<T>(end - begin);
+  builder.addAll(begin, end);
+  return builder.finish();
+}
+
+template <typename T>
+inline Array<T> heapArray(std::initializer_list<T> init) {
+  return heapArray<T>(init.begin(), init.end());
+}
+
+}  // namespace kj
+
+#endif  // KJ_ARRAY_H_