include/private/base/SkTArray.h - skia - Git at Google

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #ifndef SkTArray_DEFINED
 #define SkTArray_DEFINED

 #include "include/private/base/SkAlignedStorage.h"
 #include "include/private/base/SkAssert.h"
 #include "include/private/base/SkAttributes.h"
 #include "include/private/base/SkContainers.h"
 #include "include/private/base/SkMalloc.h"
 #include "include/private/base/SkMath.h"
 #include "include/private/base/SkSpan_impl.h"
 #include "include/private/base/SkTo.h"
 #include "include/private/base/SkTypeTraits.h"  // IWYU pragma: keep

 #include <algorithm>
 #include <climits>
 #include <cstddef>
 #include <cstdint>
 #include <cstring>
 #include <initializer_list>
 #include <new>
 #include <utility>

 /** SkTArray<T> implements a typical, mostly std::vector-like array.
     Each T will be default-initialized on allocation, and ~T will be called on destruction.

     MEM_MOVE controls the behavior when a T needs to be moved (e.g. when the array is resized)
       - true: T will be bit-copied via memcpy.
       - false: T will be moved via move-constructors.

     Modern implementations of std::vector<T> will generally provide similar performance
     characteristics when used with appropriate care. Consider using std::vector<T> in new code.
 */
 template <typename T, bool MEM_MOVE = sk_is_trivially_relocatable_v<T>> class SkTArray {
 public:
     using value_type = T;

     /**
      * Creates an empty array with no initial storage
      */
     SkTArray() : fOwnMemory(true), fCapacity{0} {}

     /**
      * Creates an empty array that will preallocate space for reserveCount
      * elements.
      */
     explicit SkTArray(int reserveCount) : SkTArray() { this->reserve_back(reserveCount); }

     /**
      * Copies one array to another. The new array will be heap allocated.
      */
     SkTArray(const SkTArray& that) : SkTArray(that.fData, that.fSize) {}

     SkTArray(SkTArray&& that) {
         if (that.fOwnMemory) {
             this->setData(that);
             that.setData({});
         } else {
             this->initData(that.fSize);
             that.move(fData);
         }
         fSize = std::exchange(that.fSize, 0);
     }

     /**
      * Creates a SkTArray by copying contents of a standard C array. The new
      * array will be heap allocated. Be careful not to use this constructor
      * when you really want the (void*, int) version.
      */
     SkTArray(const T* array, int count) {
         this->initData(count);
         this->copy(array);
     }

     /**
      * Creates a SkTArray by copying contents of an initializer list.
      */
     SkTArray(std::initializer_list<T> data) : SkTArray(data.begin(), data.size()) {}

     SkTArray& operator=(const SkTArray& that) {
         if (this == &that) {
             return *this;
         }
         this->clear();
         this->checkRealloc(that.size(), kExactFit);
         fSize = that.fSize;
         this->copy(that.fData);
         return *this;
     }
     SkTArray& operator=(SkTArray&& that) {
         if (this != &that) {
             this->clear();
             if (that.fOwnMemory) {
                 // The storage is on the heap, so move the data pointer.
                 if (fOwnMemory) {
                     sk_free(fData);
                 }

                 fData = std::exchange(that.fData, nullptr);

                 // Can't use exchange with bitfields.
                 fCapacity = that.fCapacity;
                 that.fCapacity = 0;

                 fOwnMemory = true;
             } else {
                 // The data is stored inline in that, so move it element-by-element.
                 this->checkRealloc(that.size(), kExactFit);
                 that.move(fData);
             }
             fSize = std::exchange(that.fSize, 0);
         }
         return *this;
     }

     ~SkTArray() {
         this->destroyAll();
         if (fOwnMemory) {
             sk_free(fData);
         }
     }

     /**
      * Resets to size() = n newly constructed T objects and resets any reserve count.
      */
     void reset(int n) {
         SkASSERT(n >= 0);
         this->clear();
         this->checkRealloc(n, kExactFit);
         fSize = n;
         for (int i = 0; i < this->size(); ++i) {
             new (fData + i) T;
         }
     }

     /**
      * Resets to a copy of a C array and resets any reserve count.
      */
     void reset(const T* array, int count) {
         SkASSERT(count >= 0);
         this->clear();
         this->checkRealloc(count, kExactFit);
         fSize = count;
         this->copy(array);
     }

     /**
      * Ensures there is enough reserved space for n elements.
      */
     void reserve(int n) {
         SkASSERT(n >= 0);
         if (n >= this->size()) {
             this->reserve_back(n - size());
         }
     }

     /**
      * Ensures there is enough reserved space for n additional elements. The is guaranteed at least
      * until the array size grows above n and subsequently shrinks below n, any version of reset()
      * is called, or reserve_back() is called again.
      */
     void reserve_back(int n) {
         SkASSERT(n >= 0);
         if (n > 0) {
             this->checkRealloc(n, kExactFit);
         }
     }

     void removeShuffle(int n) {
         SkASSERT(n < this->size());
         int newCount = fSize - 1;
         fSize = newCount;
         fData[n].~T();
         if (n != newCount) {
             this->move(n, newCount);
         }
     }

     // Is the array empty.
     bool empty() const { return fSize == 0; }

     /**
      * Adds 1 new default-initialized T value and returns it by reference. Note
      * the reference only remains valid until the next call that adds or removes
      * elements.
      */
     T& push_back() {
         void* newT = this->push_back_raw(1);
         return *new (newT) T;
     }

     /**
      * Version of above that uses a copy constructor to initialize the new item
      */
     T& push_back(const T& t) {
         void* newT = this->push_back_raw(1);
         return *new (newT) T(t);
     }

     /**
      * Version of above that uses a move constructor to initialize the new item
      */
     T& push_back(T&& t) {
         void* newT = this->push_back_raw(1);
         return *new (newT) T(std::move(t));
     }

     /**
      *  Construct a new T at the back of this array.
      */
     template<class... Args> T& emplace_back(Args&&... args) {
         void* newT = this->push_back_raw(1);
         return *new (newT) T(std::forward<Args>(args)...);
     }

     /**
      * Allocates n more default-initialized T values, and returns the address of
      * the start of that new range. Note: this address is only valid until the
      * next API call made on the array that might add or remove elements.
      */
     T* push_back_n(int n) {
         SkASSERT(n >= 0);
         T* newTs = TCast(this->push_back_raw(n));
         for (int i = 0; i < n; ++i) {
             new (&newTs[i]) T;
         }
         return newTs;
     }

     /**
      * Version of above that uses a copy constructor to initialize all n items
      * to the same T.
      */
     T* push_back_n(int n, const T& t) {
         SkASSERT(n >= 0);
         T* newTs = TCast(this->push_back_raw(n));
         for (int i = 0; i < n; ++i) {
             new (&newTs[i]) T(t);
         }
         return static_cast<T*>(newTs);
     }

     /**
      * Version of above that uses a copy constructor to initialize the n items
      * to separate T values.
      */
     T* push_back_n(int n, const T t[]) {
         SkASSERT(n >= 0);
         this->checkRealloc(n, kGrowing);
         T* end = this->end();
         for (int i = 0; i < n; ++i) {
             new (end + i) T(t[i]);
         }
         fSize += n;
         return end;
     }

     /**
      * Version of above that uses the move constructor to set n items.
      */
     T* move_back_n(int n, T* t) {
         SkASSERT(n >= 0);
         this->checkRealloc(n, kGrowing);
         T* end = this->end();
         for (int i = 0; i < n; ++i) {
             new (end + i) T(std::move(t[i]));
         }
         fSize += n;
         return end;
     }

     /**
      * Removes the last element. Not safe to call when size() == 0.
      */
     void pop_back() {
         SkASSERT(fSize > 0);
         --fSize;
         fData[fSize].~T();
     }

     /**
      * Removes the last n elements. Not safe to call when size() < n.
      */
     void pop_back_n(int n) {
         SkASSERT(n >= 0);
         SkASSERT(this->size() >= n);
         int i = fSize;
         while (i-- > fSize - n) {
             (*this)[i].~T();
         }
         fSize -= n;
     }

     /**
      * Pushes or pops from the back to resize. Pushes will be default
      * initialized.
      */
     void resize_back(int newCount) {
         SkASSERT(newCount >= 0);

         if (newCount > this->size()) {
             this->push_back_n(newCount - fSize);
         } else if (newCount < this->size()) {
             this->pop_back_n(fSize - newCount);
         }
     }

     /** Swaps the contents of this array with that array. Does a pointer swap if possible,
         otherwise copies the T values. */
     void swap(SkTArray& that) {
         using std::swap;
         if (this == &that) {
             return;
         }
         if (fOwnMemory && that.fOwnMemory) {
             swap(fData, that.fData);
             swap(fSize, that.fSize);

             // Can't use swap because fCapacity is a bit field.
             auto allocCount = fCapacity;
             fCapacity = that.fCapacity;
             that.fCapacity = allocCount;
         } else {
             // This could be more optimal...
             SkTArray copy(std::move(that));
             that = std::move(*this);
             *this = std::move(copy);
         }
     }

     T* begin() {
         return fData;
     }
     const T* begin() const {
         return fData;
     }

     // It's safe to use fItemArray + fSize because if fItemArray is nullptr then adding 0 is
     // valid and returns nullptr. See [expr.add] in the C++ standard.
     T* end() {
         if (fData == nullptr) {
             SkASSERT(fSize == 0);
         }
         return fData + fSize;
     }
     const T* end() const {
         if (fData == nullptr) {
             SkASSERT(fSize == 0);
         }
         return fData + fSize;
     }
     T* data() { return fData; }
     const T* data() const { return fData; }
     int size() const { return fSize; }
     size_t size_bytes() const { return this->bytes(fSize); }
     void resize(size_t count) { this->resize_back((int)count); }

     void clear() {
         this->destroyAll();
         fSize = 0;
     }

     void shrink_to_fit() {
         if (!fOwnMemory || fSize == fCapacity) {
             return;
         }
         if (fSize == 0) {
             sk_free(fData);
             fData = nullptr;
             fCapacity = 0;
         } else {
             SkSpan<std::byte> allocation = Allocate(fSize);
             this->move(TCast(allocation.data()));
             if (fOwnMemory) {
                 sk_free(fData);
             }
             this->setDataFromBytes(allocation);
         }
     }

     /**
      * Get the i^th element.
      */
     T& operator[] (int i) {
         SkASSERT(i < this->size());
         SkASSERT(i >= 0);
         return fData[i];
     }

     const T& operator[] (int i) const {
         SkASSERT(i < this->size());
         SkASSERT(i >= 0);
         return fData[i];
     }

     T& at(int i) { return (*this)[i]; }
     const T& at(int i) const { return (*this)[i]; }

     /**
      * equivalent to operator[](0)
      */
     T& front() { SkASSERT(fSize > 0); return fData[0];}

     const T& front() const { SkASSERT(fSize > 0); return fData[0];}

     /**
      * equivalent to operator[](size() - 1)
      */
     T& back() { SkASSERT(fSize); return fData[fSize - 1];}

     const T& back() const { SkASSERT(fSize > 0); return fData[fSize - 1];}

     /**
      * equivalent to operator[](size()-1-i)
      */
     T& fromBack(int i) {
         SkASSERT(i >= 0);
         SkASSERT(i < this->size());
         return fData[fSize - i - 1];
     }

     const T& fromBack(int i) const {
         SkASSERT(i >= 0);
         SkASSERT(i < this->size());
         return fData[fSize - i - 1];
     }

     bool operator==(const SkTArray<T, MEM_MOVE>& right) const {
         int leftCount = this->size();
         if (leftCount != right.size()) {
             return false;
         }
         for (int index = 0; index < leftCount; ++index) {
             if (fData[index] != right.fData[index]) {
                 return false;
             }
         }
         return true;
     }

     bool operator!=(const SkTArray<T, MEM_MOVE>& right) const {
         return !(*this == right);
     }

     int capacity() const {
         return fCapacity;
     }

 protected:
     // Creates an empty array that will use the passed storage block until it is insufficiently
     // large to hold the entire array.
     template <int InitialCapacity>
     SkTArray(SkAlignedSTStorage<InitialCapacity, T>* storage, int size = 0) {
         static_assert(InitialCapacity >= 0);
         SkASSERT(size >= 0);
         SkASSERT(storage->get() != nullptr);
         if (size > InitialCapacity) {
             this->initData(size);
         } else {
             this->setDataFromBytes(*storage);
             fSize = size;

             // setDataFromBytes always sets fOwnMemory to true, but we are actually using static
             // storage here, which shouldn't ever be freed.
             fOwnMemory = false;
         }
     }

     // Copy a C array, using pre-allocated storage if preAllocCount >= count. Otherwise, storage
     // will only be used when array shrinks to fit.
     template <int InitialCapacity>
     SkTArray(const T* array, int size, SkAlignedSTStorage<InitialCapacity, T>* storage)
         : SkTArray{storage, size}
     {
         this->copy(array);
     }

 private:
     // Growth factors for checkRealloc.
     static constexpr double kExactFit = 1.0;
     static constexpr double kGrowing = 1.5;

     static constexpr int kMinHeapAllocCount = 8;
     static_assert(SkIsPow2(kMinHeapAllocCount), "min alloc count not power of two.");

     // Note for 32-bit machines kMaxCapacity will be <= SIZE_MAX. For 64-bit machines it will
     // just be INT_MAX if the sizeof(T) < 2^32.
     static constexpr int kMaxCapacity = SkToInt(std::min(SIZE_MAX / sizeof(T), (size_t)INT_MAX));

     void setDataFromBytes(SkSpan<std::byte> allocation) {
         T* data = TCast(allocation.data());
         // We have gotten extra bytes back from the allocation limit, pin to kMaxCapacity. It
         // would seem like the SkContainerAllocator should handle the divide, but it would have
         // to a full divide instruction. If done here the size is known at compile, and usually
         // can be implemented by a right shift. The full divide takes ~50X longer than the shift.
         size_t size = std::min(allocation.size() / sizeof(T), SkToSizeT(kMaxCapacity));
         setData(SkSpan<T>(data, size));
     }

     void setData(SkSpan<T> array) {
         fData = array.data();
         fCapacity = SkToU32(array.size());
         fOwnMemory = true;
     }

     // We disable Control-Flow Integrity sanitization (go/cfi) when casting item-array buffers.
     // CFI flags this code as dangerous because we are casting `buffer` to a T* while the buffer's
     // contents might still be uninitialized memory. When T has a vtable, this is especially risky
     // because we could hypothetically access a virtual method on fItemArray and jump to an
     // unpredictable location in memory. Of course, SkTArray won't actually use fItemArray in this
     // way, and we don't want to construct a T before the user requests one. There's no real risk
     // here, so disable CFI when doing these casts.
     SK_NO_SANITIZE("cfi")
     static T* TCast(void* buffer) {
         return (T*)buffer;
     }

     size_t bytes(int n) const {
         SkASSERT(n <= kMaxCapacity);
         return SkToSizeT(n) * sizeof(T);
     }

     static SkSpan<std::byte> Allocate(int capacity, double growthFactor = 1.0) {
         return SkContainerAllocator{sizeof(T), kMaxCapacity}.allocate(capacity, growthFactor);
     }

     void initData(int count) {
         this->setDataFromBytes(Allocate(count));
         fSize = count;
     }

     void destroyAll() {
         if (!this->empty()) {
             T* cursor = this->begin();
             T* const end = this->end();
             do {
                 cursor->~T();
                 cursor++;
             } while (cursor < end);
         }
     }

     /** In the following move and copy methods, 'dst' is assumed to be uninitialized raw storage.
      *  In the following move methods, 'src' is destroyed leaving behind uninitialized raw storage.
      */
     void copy(const T* src) {
         if constexpr (std::is_trivially_copyable_v<T>) {
             if (!this->empty() && src != nullptr) {
                 sk_careful_memcpy(fData, src, this->size_bytes());
             }
         } else {
             for (int i = 0; i < this->size(); ++i) {
                 new (fData + i) T(src[i]);
             }
         }
     }

     void move(int dst, int src) {
         if constexpr (MEM_MOVE) {
             memcpy(static_cast<void*>(&fData[dst]),
                    static_cast<const void*>(&fData[src]),
                    sizeof(T));
         } else {
             new (&fData[dst]) T(std::move(fData[src]));
             fData[src].~T();
         }
     }

     void move(void* dst) {
         if constexpr (MEM_MOVE) {
             sk_careful_memcpy(dst, fData, this->bytes(fSize));
         } else {
             for (int i = 0; i < this->size(); ++i) {
                 new (static_cast<char*>(dst) + this->bytes(i)) T(std::move(fData[i]));
                 fData[i].~T();
             }
         }
     }

     // Helper function that makes space for n objects, adjusts the count, but does not initialize
     // the new objects.
     void* push_back_raw(int n) {
         this->checkRealloc(n, kGrowing);
         void* ptr = fData + fSize;
         fSize += n;
         return ptr;
     }

     void checkRealloc(int delta, double growthFactor) {
         // This constant needs to be declared in the function where it is used to work around
         // MSVC's persnickety nature about template definitions.
         SkASSERT(delta >= 0);
         SkASSERT(fSize >= 0);
         SkASSERT(fCapacity >= 0);

         // Return if there are enough remaining allocated elements to satisfy the request.
         if (this->capacity() - fSize >= delta) {
             return;
         }

         // Don't overflow fSize or size_t later in the memory allocation. Overflowing memory
         // allocation really only applies to fSizes on 32-bit machines; on 64-bit machines this
         // will probably never produce a check. Since kMaxCapacity is bounded above by INT_MAX,
         // this also checks the bounds of fSize.
         if (delta > kMaxCapacity - fSize) {
             sk_report_container_overflow_and_die();
         }
         const int newCount = fSize + delta;

         SkSpan<std::byte> allocation = Allocate(newCount, growthFactor);

         this->move(TCast(allocation.data()));
         if (fOwnMemory) {
             sk_free(fData);
         }
         this->setDataFromBytes(allocation);
         SkASSERT(this->capacity() >= newCount);
         SkASSERT(fData != nullptr);
     }

     T* fData{nullptr};
     int fSize{0};
     uint32_t fOwnMemory : 1;
     uint32_t fCapacity : 31;
 };

 template <typename T, bool M> static inline void swap(SkTArray<T, M>& a, SkTArray<T, M>& b) {
     a.swap(b);
 }

 /**
  * Subclass of SkTArray that contains a preallocated memory block for the array.
  */
 template <int N, typename T, bool MEM_MOVE = sk_is_trivially_relocatable_v<T>>
 class SkSTArray : private SkAlignedSTStorage<N,T>, public SkTArray<T, MEM_MOVE> {
 private:
     static_assert(N > 0);
     using STORAGE   = SkAlignedSTStorage<N,T>;
     using INHERITED = SkTArray<T, MEM_MOVE>;

 public:
     SkSTArray()
         : STORAGE{}, INHERITED(static_cast<STORAGE*>(this)) {}

     SkSTArray(const T* array, int count)
         : STORAGE{}, INHERITED(array, count, static_cast<STORAGE*>(this)) {}

     SkSTArray(std::initializer_list<T> data) : SkSTArray(data.begin(), SkToInt(data.size())) {}

     explicit SkSTArray(int reserveCount) : SkSTArray() {
         this->reserve_back(reserveCount);
     }

     SkSTArray         (const SkSTArray&  that) : SkSTArray() { *this = that; }
     explicit SkSTArray(const INHERITED&  that) : SkSTArray() { *this = that; }
     SkSTArray         (      SkSTArray&& that) : SkSTArray() { *this = std::move(that); }
     explicit SkSTArray(      INHERITED&& that) : SkSTArray() { *this = std::move(that); }

     SkSTArray& operator=(const SkSTArray& that) {
         INHERITED::operator=(that);
         return *this;
     }
     SkSTArray& operator=(const INHERITED& that) {
         INHERITED::operator=(that);
         return *this;
     }

     SkSTArray& operator=(SkSTArray&& that) {
         INHERITED::operator=(std::move(that));
         return *this;
     }
     SkSTArray& operator=(INHERITED&& that) {
         INHERITED::operator=(std::move(that));
         return *this;
     }

     // Force the use of SkTArray for data() and size().
     using INHERITED::data;
     using INHERITED::size;
 };

 #endif
	/*
	* Copyright 2011 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#ifndef SkTArray_DEFINED
	#define SkTArray_DEFINED

	#include "include/private/base/SkAlignedStorage.h"
	#include "include/private/base/SkAssert.h"
	#include "include/private/base/SkAttributes.h"
	#include "include/private/base/SkContainers.h"
	#include "include/private/base/SkMalloc.h"
	#include "include/private/base/SkMath.h"
	#include "include/private/base/SkSpan_impl.h"
	#include "include/private/base/SkTo.h"
	#include "include/private/base/SkTypeTraits.h" // IWYU pragma: keep

	#include <algorithm>
	#include <climits>
	#include <cstddef>
	#include <cstdint>
	#include <cstring>
	#include <initializer_list>
	#include <new>
	#include <utility>

	/** SkTArray<T> implements a typical, mostly std::vector-like array.
	Each T will be default-initialized on allocation, and ~T will be called on destruction.

	MEM_MOVE controls the behavior when a T needs to be moved (e.g. when the array is resized)
	- true: T will be bit-copied via memcpy.
	- false: T will be moved via move-constructors.

	Modern implementations of std::vector<T> will generally provide similar performance
	characteristics when used with appropriate care. Consider using std::vector<T> in new code.
	*/
	template <typename T, bool MEM_MOVE = sk_is_trivially_relocatable_v<T>> class SkTArray {
	public:
	using value_type = T;

	/**
	* Creates an empty array with no initial storage
	*/
	SkTArray() : fOwnMemory(true), fCapacity{0} {}

	/**
	* Creates an empty array that will preallocate space for reserveCount
	* elements.
	*/
	explicit SkTArray(int reserveCount) : SkTArray() { this->reserve_back(reserveCount); }

	/**
	* Copies one array to another. The new array will be heap allocated.
	*/
	SkTArray(const SkTArray& that) : SkTArray(that.fData, that.fSize) {}

	SkTArray(SkTArray&& that) {
	if (that.fOwnMemory) {
	this->setData(that);
	that.setData({});
	} else {
	this->initData(that.fSize);
	that.move(fData);
	}
	fSize = std::exchange(that.fSize, 0);
	}

	/**
	* Creates a SkTArray by copying contents of a standard C array. The new
	* array will be heap allocated. Be careful not to use this constructor
	* when you really want the (void*, int) version.
	*/
	SkTArray(const T* array, int count) {
	this->initData(count);
	this->copy(array);
	}

	/**
	* Creates a SkTArray by copying contents of an initializer list.
	*/
	SkTArray(std::initializer_list<T> data) : SkTArray(data.begin(), data.size()) {}

	SkTArray& operator=(const SkTArray& that) {
	if (this == &that) {
	return *this;
	}
	this->clear();
	this->checkRealloc(that.size(), kExactFit);
	fSize = that.fSize;
	this->copy(that.fData);
	return *this;
	}
	SkTArray& operator=(SkTArray&& that) {
	if (this != &that) {
	this->clear();
	if (that.fOwnMemory) {
	// The storage is on the heap, so move the data pointer.
	if (fOwnMemory) {
	sk_free(fData);
	}

	fData = std::exchange(that.fData, nullptr);

	// Can't use exchange with bitfields.
	fCapacity = that.fCapacity;
	that.fCapacity = 0;

	fOwnMemory = true;
	} else {
	// The data is stored inline in that, so move it element-by-element.
	this->checkRealloc(that.size(), kExactFit);
	that.move(fData);
	}
	fSize = std::exchange(that.fSize, 0);
	}
	return *this;
	}

	~SkTArray() {
	this->destroyAll();
	if (fOwnMemory) {
	sk_free(fData);
	}
	}

	/**
	* Resets to size() = n newly constructed T objects and resets any reserve count.
	*/
	void reset(int n) {
	SkASSERT(n >= 0);
	this->clear();
	this->checkRealloc(n, kExactFit);
	fSize = n;
	for (int i = 0; i < this->size(); ++i) {
	new (fData + i) T;
	}
	}

	/**
	* Resets to a copy of a C array and resets any reserve count.
	*/
	void reset(const T* array, int count) {
	SkASSERT(count >= 0);
	this->clear();
	this->checkRealloc(count, kExactFit);
	fSize = count;
	this->copy(array);
	}

	/**
	* Ensures there is enough reserved space for n elements.
	*/
	void reserve(int n) {
	SkASSERT(n >= 0);
	if (n >= this->size()) {
	this->reserve_back(n - size());
	}
	}

	/**
	* Ensures there is enough reserved space for n additional elements. The is guaranteed at least
	* until the array size grows above n and subsequently shrinks below n, any version of reset()
	* is called, or reserve_back() is called again.
	*/
	void reserve_back(int n) {
	SkASSERT(n >= 0);
	if (n > 0) {
	this->checkRealloc(n, kExactFit);
	}
	}

	void removeShuffle(int n) {
	SkASSERT(n < this->size());
	int newCount = fSize - 1;
	fSize = newCount;
	fData[n].~T();
	if (n != newCount) {
	this->move(n, newCount);
	}
	}

	// Is the array empty.
	bool empty() const { return fSize == 0; }

	/**
	* Adds 1 new default-initialized T value and returns it by reference. Note
	* the reference only remains valid until the next call that adds or removes
	* elements.
	*/
	T& push_back() {
	void* newT = this->push_back_raw(1);
	return *new (newT) T;
	}

	/**
	* Version of above that uses a copy constructor to initialize the new item
	*/
	T& push_back(const T& t) {
	void* newT = this->push_back_raw(1);
	return *new (newT) T(t);
	}

	/**
	* Version of above that uses a move constructor to initialize the new item
	*/
	T& push_back(T&& t) {
	void* newT = this->push_back_raw(1);
	return *new (newT) T(std::move(t));
	}

	/**
	* Construct a new T at the back of this array.
	*/
	template<class... Args> T& emplace_back(Args&&... args) {
	void* newT = this->push_back_raw(1);
	return *new (newT) T(std::forward<Args>(args)...);
	}

	/**
	* Allocates n more default-initialized T values, and returns the address of
	* the start of that new range. Note: this address is only valid until the
	* next API call made on the array that might add or remove elements.
	*/
	T* push_back_n(int n) {
	SkASSERT(n >= 0);
	T* newTs = TCast(this->push_back_raw(n));
	for (int i = 0; i < n; ++i) {
	new (&newTs[i]) T;
	}
	return newTs;
	}

	/**
	* Version of above that uses a copy constructor to initialize all n items
	* to the same T.
	*/
	T* push_back_n(int n, const T& t) {
	SkASSERT(n >= 0);
	T* newTs = TCast(this->push_back_raw(n));
	for (int i = 0; i < n; ++i) {
	new (&newTs[i]) T(t);
	}
	return static_cast<T*>(newTs);
	}

	/**
	* Version of above that uses a copy constructor to initialize the n items
	* to separate T values.
	*/
	T* push_back_n(int n, const T t[]) {
	SkASSERT(n >= 0);
	this->checkRealloc(n, kGrowing);
	T* end = this->end();
	for (int i = 0; i < n; ++i) {
	new (end + i) T(t[i]);
	}
	fSize += n;
	return end;
	}

	/**
	* Version of above that uses the move constructor to set n items.
	*/
	T* move_back_n(int n, T* t) {
	SkASSERT(n >= 0);
	this->checkRealloc(n, kGrowing);
	T* end = this->end();
	for (int i = 0; i < n; ++i) {
	new (end + i) T(std::move(t[i]));
	}
	fSize += n;
	return end;
	}

	/**
	* Removes the last element. Not safe to call when size() == 0.
	*/
	void pop_back() {
	SkASSERT(fSize > 0);
	--fSize;
	fData[fSize].~T();
	}

	/**
	* Removes the last n elements. Not safe to call when size() < n.
	*/
	void pop_back_n(int n) {
	SkASSERT(n >= 0);
	SkASSERT(this->size() >= n);
	int i = fSize;
	while (i-- > fSize - n) {
	(*this)[i].~T();
	}
	fSize -= n;
	}

	/**
	* Pushes or pops from the back to resize. Pushes will be default
	* initialized.
	*/
	void resize_back(int newCount) {
	SkASSERT(newCount >= 0);

	if (newCount > this->size()) {
	this->push_back_n(newCount - fSize);
	} else if (newCount < this->size()) {
	this->pop_back_n(fSize - newCount);
	}
	}

	/** Swaps the contents of this array with that array. Does a pointer swap if possible,
	otherwise copies the T values. */
	void swap(SkTArray& that) {
	using std::swap;
	if (this == &that) {
	return;
	}
	if (fOwnMemory && that.fOwnMemory) {
	swap(fData, that.fData);
	swap(fSize, that.fSize);

	// Can't use swap because fCapacity is a bit field.
	auto allocCount = fCapacity;
	fCapacity = that.fCapacity;
	that.fCapacity = allocCount;
	} else {
	// This could be more optimal...
	SkTArray copy(std::move(that));
	that = std::move(*this);
	*this = std::move(copy);
	}
	}

	T* begin() {
	return fData;
	}
	const T* begin() const {
	return fData;
	}

	// It's safe to use fItemArray + fSize because if fItemArray is nullptr then adding 0 is
	// valid and returns nullptr. See [expr.add] in the C++ standard.
	T* end() {
	if (fData == nullptr) {
	SkASSERT(fSize == 0);
	}
	return fData + fSize;
	}
	const T* end() const {
	if (fData == nullptr) {
	SkASSERT(fSize == 0);
	}
	return fData + fSize;
	}
	T* data() { return fData; }
	const T* data() const { return fData; }
	int size() const { return fSize; }
	size_t size_bytes() const { return this->bytes(fSize); }
	void resize(size_t count) { this->resize_back((int)count); }

	void clear() {
	this->destroyAll();
	fSize = 0;
	}

	void shrink_to_fit() {
	if (!fOwnMemory \|\| fSize == fCapacity) {
	return;
	}
	if (fSize == 0) {
	sk_free(fData);
	fData = nullptr;
	fCapacity = 0;
	} else {
	SkSpan<std::byte> allocation = Allocate(fSize);
	this->move(TCast(allocation.data()));
	if (fOwnMemory) {
	sk_free(fData);
	}
	this->setDataFromBytes(allocation);
	}
	}

	/**
	* Get the i^th element.
	*/
	T& operator[] (int i) {
	SkASSERT(i < this->size());
	SkASSERT(i >= 0);
	return fData[i];
	}

	const T& operator[] (int i) const {
	SkASSERT(i < this->size());
	SkASSERT(i >= 0);
	return fData[i];
	}

	T& at(int i) { return (*this)[i]; }
	const T& at(int i) const { return (*this)[i]; }

	/**
	* equivalent to operator[](0)
	*/
	T& front() { SkASSERT(fSize > 0); return fData[0];}

	const T& front() const { SkASSERT(fSize > 0); return fData[0];}

	/**
	* equivalent to operator[](size() - 1)
	*/
	T& back() { SkASSERT(fSize); return fData[fSize - 1];}

	const T& back() const { SkASSERT(fSize > 0); return fData[fSize - 1];}

	/**
	* equivalent to operator[](size()-1-i)
	*/
	T& fromBack(int i) {
	SkASSERT(i >= 0);
	SkASSERT(i < this->size());
	return fData[fSize - i - 1];
	}

	const T& fromBack(int i) const {
	SkASSERT(i >= 0);
	SkASSERT(i < this->size());
	return fData[fSize - i - 1];
	}

	bool operator==(const SkTArray<T, MEM_MOVE>& right) const {
	int leftCount = this->size();
	if (leftCount != right.size()) {
	return false;
	}
	for (int index = 0; index < leftCount; ++index) {
	if (fData[index] != right.fData[index]) {
	return false;
	}
	}
	return true;
	}

	bool operator!=(const SkTArray<T, MEM_MOVE>& right) const {
	return !(*this == right);
	}

	int capacity() const {
	return fCapacity;
	}

	protected:
	// Creates an empty array that will use the passed storage block until it is insufficiently
	// large to hold the entire array.
	template <int InitialCapacity>
	SkTArray(SkAlignedSTStorage<InitialCapacity, T>* storage, int size = 0) {
	static_assert(InitialCapacity >= 0);
	SkASSERT(size >= 0);
	SkASSERT(storage->get() != nullptr);
	if (size > InitialCapacity) {
	this->initData(size);
	} else {
	this->setDataFromBytes(*storage);
	fSize = size;

	// setDataFromBytes always sets fOwnMemory to true, but we are actually using static
	// storage here, which shouldn't ever be freed.
	fOwnMemory = false;
	}
	}

	// Copy a C array, using pre-allocated storage if preAllocCount >= count. Otherwise, storage
	// will only be used when array shrinks to fit.
	template <int InitialCapacity>
	SkTArray(const T* array, int size, SkAlignedSTStorage<InitialCapacity, T>* storage)
	: SkTArray{storage, size}
	{
	this->copy(array);
	}

	private:
	// Growth factors for checkRealloc.
	static constexpr double kExactFit = 1.0;
	static constexpr double kGrowing = 1.5;

	static constexpr int kMinHeapAllocCount = 8;
	static_assert(SkIsPow2(kMinHeapAllocCount), "min alloc count not power of two.");

	// Note for 32-bit machines kMaxCapacity will be <= SIZE_MAX. For 64-bit machines it will
	// just be INT_MAX if the sizeof(T) < 2^32.
	static constexpr int kMaxCapacity = SkToInt(std::min(SIZE_MAX / sizeof(T), (size_t)INT_MAX));

	void setDataFromBytes(SkSpan<std::byte> allocation) {
	T* data = TCast(allocation.data());
	// We have gotten extra bytes back from the allocation limit, pin to kMaxCapacity. It
	// would seem like the SkContainerAllocator should handle the divide, but it would have
	// to a full divide instruction. If done here the size is known at compile, and usually
	// can be implemented by a right shift. The full divide takes ~50X longer than the shift.
	size_t size = std::min(allocation.size() / sizeof(T), SkToSizeT(kMaxCapacity));
	setData(SkSpan<T>(data, size));
	}

	void setData(SkSpan<T> array) {
	fData = array.data();
	fCapacity = SkToU32(array.size());
	fOwnMemory = true;
	}

	// We disable Control-Flow Integrity sanitization (go/cfi) when casting item-array buffers.
	// CFI flags this code as dangerous because we are casting `buffer` to a T* while the buffer's
	// contents might still be uninitialized memory. When T has a vtable, this is especially risky
	// because we could hypothetically access a virtual method on fItemArray and jump to an
	// unpredictable location in memory. Of course, SkTArray won't actually use fItemArray in this
	// way, and we don't want to construct a T before the user requests one. There's no real risk
	// here, so disable CFI when doing these casts.
	SK_NO_SANITIZE("cfi")
	static T* TCast(void* buffer) {
	return (T*)buffer;
	}

	size_t bytes(int n) const {
	SkASSERT(n <= kMaxCapacity);
	return SkToSizeT(n) * sizeof(T);
	}

	static SkSpan<std::byte> Allocate(int capacity, double growthFactor = 1.0) {
	return SkContainerAllocator{sizeof(T), kMaxCapacity}.allocate(capacity, growthFactor);
	}

	void initData(int count) {
	this->setDataFromBytes(Allocate(count));
	fSize = count;
	}

	void destroyAll() {
	if (!this->empty()) {
	T* cursor = this->begin();
	T* const end = this->end();
	do {
	cursor->~T();
	cursor++;
	} while (cursor < end);
	}
	}

	/** In the following move and copy methods, 'dst' is assumed to be uninitialized raw storage.
	* In the following move methods, 'src' is destroyed leaving behind uninitialized raw storage.
	*/
	void copy(const T* src) {
	if constexpr (std::is_trivially_copyable_v<T>) {
	if (!this->empty() && src != nullptr) {
	sk_careful_memcpy(fData, src, this->size_bytes());
	}
	} else {
	for (int i = 0; i < this->size(); ++i) {
	new (fData + i) T(src[i]);
	}
	}
	}

	void move(int dst, int src) {
	if constexpr (MEM_MOVE) {
	memcpy(static_cast<void*>(&fData[dst]),
	static_cast<const void*>(&fData[src]),
	sizeof(T));
	} else {
	new (&fData[dst]) T(std::move(fData[src]));
	fData[src].~T();
	}
	}

	void move(void* dst) {
	if constexpr (MEM_MOVE) {
	sk_careful_memcpy(dst, fData, this->bytes(fSize));
	} else {
	for (int i = 0; i < this->size(); ++i) {
	new (static_cast<char*>(dst) + this->bytes(i)) T(std::move(fData[i]));
	fData[i].~T();
	}
	}
	}

	// Helper function that makes space for n objects, adjusts the count, but does not initialize
	// the new objects.
	void* push_back_raw(int n) {
	this->checkRealloc(n, kGrowing);
	void* ptr = fData + fSize;
	fSize += n;
	return ptr;
	}

	void checkRealloc(int delta, double growthFactor) {
	// This constant needs to be declared in the function where it is used to work around
	// MSVC's persnickety nature about template definitions.
	SkASSERT(delta >= 0);
	SkASSERT(fSize >= 0);
	SkASSERT(fCapacity >= 0);

	// Return if there are enough remaining allocated elements to satisfy the request.
	if (this->capacity() - fSize >= delta) {
	return;
	}

	// Don't overflow fSize or size_t later in the memory allocation. Overflowing memory
	// allocation really only applies to fSizes on 32-bit machines; on 64-bit machines this
	// will probably never produce a check. Since kMaxCapacity is bounded above by INT_MAX,
	// this also checks the bounds of fSize.
	if (delta > kMaxCapacity - fSize) {
	sk_report_container_overflow_and_die();
	}
	const int newCount = fSize + delta;

	SkSpan<std::byte> allocation = Allocate(newCount, growthFactor);

	this->move(TCast(allocation.data()));
	if (fOwnMemory) {
	sk_free(fData);
	}
	this->setDataFromBytes(allocation);
	SkASSERT(this->capacity() >= newCount);
	SkASSERT(fData != nullptr);
	}

	T* fData{nullptr};
	int fSize{0};
	uint32_t fOwnMemory : 1;
	uint32_t fCapacity : 31;
	};

	template <typename T, bool M> static inline void swap(SkTArray<T, M>& a, SkTArray<T, M>& b) {
	a.swap(b);
	}

	/**
	* Subclass of SkTArray that contains a preallocated memory block for the array.
	*/
	template <int N, typename T, bool MEM_MOVE = sk_is_trivially_relocatable_v<T>>
	class SkSTArray : private SkAlignedSTStorage<N,T>, public SkTArray<T, MEM_MOVE> {
	private:
	static_assert(N > 0);
	using STORAGE = SkAlignedSTStorage<N,T>;
	using INHERITED = SkTArray<T, MEM_MOVE>;

	public:
	SkSTArray()
	: STORAGE{}, INHERITED(static_cast<STORAGE*>(this)) {}

	SkSTArray(const T* array, int count)
	: STORAGE{}, INHERITED(array, count, static_cast<STORAGE*>(this)) {}

	SkSTArray(std::initializer_list<T> data) : SkSTArray(data.begin(), SkToInt(data.size())) {}

	explicit SkSTArray(int reserveCount) : SkSTArray() {
	this->reserve_back(reserveCount);
	}

	SkSTArray (const SkSTArray& that) : SkSTArray() { *this = that; }
	explicit SkSTArray(const INHERITED& that) : SkSTArray() { *this = that; }
	SkSTArray ( SkSTArray&& that) : SkSTArray() { *this = std::move(that); }
	explicit SkSTArray( INHERITED&& that) : SkSTArray() { *this = std::move(that); }

	SkSTArray& operator=(const SkSTArray& that) {
	INHERITED::operator=(that);
	return *this;
	}
	SkSTArray& operator=(const INHERITED& that) {
	INHERITED::operator=(that);
	return *this;
	}

	SkSTArray& operator=(SkSTArray&& that) {
	INHERITED::operator=(std::move(that));
	return *this;
	}
	SkSTArray& operator=(INHERITED&& that) {
	INHERITED::operator=(std::move(that));
	return *this;
	}

	// Force the use of SkTArray for data() and size().
	using INHERITED::data;
	using INHERITED::size;
	};

	#endif