libs/hwui/canvas/OpBuffer.h - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2020 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #pragma once

 #include <algorithm>
 #include <array>
 #include <cinttypes>
 #include <cstddef>
 #include <cstdlib>
 #include <type_traits>
 #include <utility>

 namespace android::uirenderer {

 template <typename T>
 struct OpBufferItemHeader {
     T type : 8;
     uint32_t size : 24;
 };

 struct OpBufferAllocationHeader {
     // Used size, including header size
     size_t used = 0;
     // Capacity, including header size
     size_t capacity = 0;
     // Offset relative to `this` at which the first item is
     size_t startOffset = 0;
     // Offset relative to `this` at which the last item is
     size_t endOffset = 0;
 };

 #define BE_OPBUFFERS_FRIEND()                                      \
     template <typename ItemTypes, template <ItemTypes> typename, typename, typename> \
     friend class OpBuffer

 template <typename ItemTypes, template <ItemTypes> typename ItemContainer,
           typename BufferHeader = OpBufferAllocationHeader,
           typename ItemTypesSequence = std::make_index_sequence<static_cast<int>(ItemTypes::COUNT)>>
 class OpBuffer {
     // Instead of re-aligning individual inserts, just pad the size of everything
     // to a multiple of pointer alignment. This assumes we never work with doubles.
     // Which we don't.
     static constexpr size_t Alignment = alignof(void*);

     static constexpr size_t PadAlign(size_t size) {
         return (size + (Alignment - 1)) & -Alignment;
     }

 public:
     static constexpr auto STARTING_SIZE = PadAlign(sizeof(BufferHeader));
     using ItemHeader = OpBufferItemHeader<ItemTypes>;

     explicit OpBuffer() = default;

     // Prevent copying by default
     OpBuffer(const OpBuffer&) = delete;
     void operator=(const OpBuffer&) = delete;

     OpBuffer(OpBuffer&& other) {
         mBuffer = other.mBuffer;
         other.mBuffer = nullptr;
     }

     void operator=(OpBuffer&& other) {
         destroy();
         mBuffer = other.mBuffer;
         other.mBuffer = nullptr;
     }

     ~OpBuffer() {
         destroy();
     }

     constexpr size_t capacity() const { return mBuffer ? mBuffer->capacity : 0; }

     constexpr size_t size() const { return mBuffer ? mBuffer->used : 0; }

     constexpr size_t remaining() const { return capacity() - size(); }

     // TODO: Add less-copy'ing variants of this. emplace_back? deferred initialization?
     template <ItemTypes T>
     void push_container(ItemContainer<T>&& op) {
         static_assert(alignof(ItemContainer<T>) <= Alignment);
         static_assert(offsetof(ItemContainer<T>, header) == 0);

         constexpr auto padded_size = PadAlign(sizeof(ItemContainer<T>));
         if (remaining() < padded_size) {
             resize(std::max(padded_size, capacity()) * 2);
         }
         mBuffer->endOffset = mBuffer->used;
         mBuffer->used += padded_size;

         void* allocateAt = reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->endOffset;
         auto temp = new (allocateAt) ItemContainer<T>{std::move(op)};
         temp->header = {.type = T, .size = padded_size};
     }

     void resize(size_t newsize) {
         // Add the header size to newsize
         const size_t adjustedSize = newsize + STARTING_SIZE;

         if (adjustedSize < size()) {
             // todo: throw?
             return;
         }
         if (newsize == 0) {
             free(mBuffer);
             mBuffer = nullptr;
         } else {
             if (mBuffer) {
                 mBuffer = reinterpret_cast<BufferHeader*>(realloc(mBuffer, adjustedSize));
                 mBuffer->capacity = adjustedSize;
             } else {
                 mBuffer = new (malloc(adjustedSize)) BufferHeader();
                 mBuffer->capacity = adjustedSize;
                 mBuffer->used = STARTING_SIZE;
                 mBuffer->startOffset = STARTING_SIZE;
             }
         }
     }

     template <typename F>
     void for_each(F&& f) const {
         do_for_each(std::forward<F>(f), ItemTypesSequence{});
     }

     void clear();

     ItemHeader* first() const { return isEmpty() ? nullptr : itemAt(mBuffer->startOffset); }

     ItemHeader* last() const { return isEmpty() ? nullptr : itemAt(mBuffer->endOffset); }

     class sentinal {
     public:
         explicit sentinal(const uint8_t* end) : end(end) {}
     private:
         const uint8_t* const end;
     };

     sentinal end() const {
         return sentinal{end_ptr()};
     }

     template <ItemTypes T>
     class filtered_iterator {
     public:
         explicit filtered_iterator(uint8_t* start, const uint8_t* end)
                 : mCurrent(start), mEnd(end) {
             ItemHeader* header = reinterpret_cast<ItemHeader*>(mCurrent);
             if (header->type != T) {
                 advance();
             }
         }

         filtered_iterator& operator++() {
             advance();
             return *this;
         }

         // Although this iterator self-terminates, we need a placeholder to compare against
         // to make for-each loops happy
         bool operator!=(const sentinal& other) const {
             return mCurrent != mEnd;
         }

         ItemContainer<T>& operator*() {
             return *reinterpret_cast<ItemContainer<T>*>(mCurrent);
         }
     private:
         void advance() {
             ItemHeader* header = reinterpret_cast<ItemHeader*>(mCurrent);
             do {
                 mCurrent += header->size;
                 header = reinterpret_cast<ItemHeader*>(mCurrent);
             } while (mCurrent != mEnd && header->type != T);
         }
         uint8_t* mCurrent;
         const uint8_t* const mEnd;
     };

     template <ItemTypes T>
     class filtered_view {
     public:
         explicit filtered_view(uint8_t* start, const uint8_t* end) : mStart(start), mEnd(end) {}

         filtered_iterator<T> begin() const {
             return filtered_iterator<T>{mStart, mEnd};
         }

         sentinal end() const {
             return sentinal{mEnd};
         }
     private:
         uint8_t* mStart;
         const uint8_t* const mEnd;
     };

     template <ItemTypes T>
     filtered_view<T> filter() const {
         return filtered_view<T>{start_ptr(), end_ptr()};
     }

 private:

     uint8_t* start_ptr() const {
         return reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->startOffset;
     }

     const uint8_t* end_ptr() const {
         return reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->used;
     }

     template <typename F, std::size_t... I>
     void do_for_each(F&& f, std::index_sequence<I...>) const {
         // Validate we're not empty
         if (isEmpty()) return;

         // Setup the jump table, mapping from each type to a springboard that invokes the template
         // function with the appropriate concrete type
         using F_PTR = decltype(&f);
         using THUNK = void (*)(F_PTR, void*);
         static constexpr auto jump = std::array<THUNK, sizeof...(I)>{[](F_PTR fp, void* t) {
             (*fp)(reinterpret_cast<const ItemContainer<static_cast<ItemTypes>(I)>*>(t));
         }...};

         // Do the actual iteration of each item
         uint8_t* current = start_ptr();
         const uint8_t* end = end_ptr();
         while (current != end) {
             auto header = reinterpret_cast<ItemHeader*>(current);
             // `f` could be a destructor, so ensure all accesses to the OP happen prior to invoking
             // `f`
             auto it = (void*)current;
             current += header->size;
             jump[static_cast<int>(header->type)](&f, it);
         }
     }

     void destroy() {
         clear();
         resize(0);
     }

     bool offsetIsValid(size_t offset) const {
         return offset >= mBuffer->startOffset && offset < mBuffer->used;
     }

     ItemHeader* itemAt(size_t offset) const {
         if (!offsetIsValid(offset)) return nullptr;
         return reinterpret_cast<ItemHeader*>(reinterpret_cast<uint8_t*>(mBuffer) + offset);
     }

     bool isEmpty() const { return mBuffer == nullptr || mBuffer->used == STARTING_SIZE; }

     BufferHeader* mBuffer = nullptr;
 };

 template <typename ItemTypes, template <ItemTypes> typename ItemContainer, typename BufferHeader,
         typename ItemTypeSequence>
 void OpBuffer<ItemTypes, ItemContainer, BufferHeader, ItemTypeSequence>::clear() {

     // Don't need to do anything if we don't have a buffer
     if (!mBuffer) return;

     for_each([](auto op) {
         using T = std::remove_reference_t<decltype(*op)>;
         op->~T();
     });
     mBuffer->used = STARTING_SIZE;
     mBuffer->startOffset = STARTING_SIZE;
     mBuffer->endOffset = 0;
 }

 }  // namespace android::uirenderer
	/*
	* Copyright (C) 2020 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#pragma once

	#include <algorithm>
	#include <array>
	#include <cinttypes>
	#include <cstddef>
	#include <cstdlib>
	#include <type_traits>
	#include <utility>

	namespace android::uirenderer {

	template <typename T>
	struct OpBufferItemHeader {
	T type : 8;
	uint32_t size : 24;
	};

	struct OpBufferAllocationHeader {
	// Used size, including header size
	size_t used = 0;
	// Capacity, including header size
	size_t capacity = 0;
	// Offset relative to `this` at which the first item is
	size_t startOffset = 0;
	// Offset relative to `this` at which the last item is
	size_t endOffset = 0;
	};

	#define BE_OPBUFFERS_FRIEND() \
	template <typename ItemTypes, template <ItemTypes> typename, typename, typename> \
	friend class OpBuffer

	template <typename ItemTypes, template <ItemTypes> typename ItemContainer,
	typename BufferHeader = OpBufferAllocationHeader,
	typename ItemTypesSequence = std::make_index_sequence<static_cast<int>(ItemTypes::COUNT)>>
	class OpBuffer {
	// Instead of re-aligning individual inserts, just pad the size of everything
	// to a multiple of pointer alignment. This assumes we never work with doubles.
	// Which we don't.
	static constexpr size_t Alignment = alignof(void*);

	static constexpr size_t PadAlign(size_t size) {
	return (size + (Alignment - 1)) & -Alignment;
	}

	public:
	static constexpr auto STARTING_SIZE = PadAlign(sizeof(BufferHeader));
	using ItemHeader = OpBufferItemHeader<ItemTypes>;

	explicit OpBuffer() = default;

	// Prevent copying by default
	OpBuffer(const OpBuffer&) = delete;
	void operator=(const OpBuffer&) = delete;

	OpBuffer(OpBuffer&& other) {
	mBuffer = other.mBuffer;
	other.mBuffer = nullptr;
	}

	void operator=(OpBuffer&& other) {
	destroy();
	mBuffer = other.mBuffer;
	other.mBuffer = nullptr;
	}

	~OpBuffer() {
	destroy();
	}

	constexpr size_t capacity() const { return mBuffer ? mBuffer->capacity : 0; }

	constexpr size_t size() const { return mBuffer ? mBuffer->used : 0; }

	constexpr size_t remaining() const { return capacity() - size(); }

	// TODO: Add less-copy'ing variants of this. emplace_back? deferred initialization?
	template <ItemTypes T>
	void push_container(ItemContainer<T>&& op) {
	static_assert(alignof(ItemContainer<T>) <= Alignment);
	static_assert(offsetof(ItemContainer<T>, header) == 0);

	constexpr auto padded_size = PadAlign(sizeof(ItemContainer<T>));
	if (remaining() < padded_size) {
	resize(std::max(padded_size, capacity()) * 2);
	}
	mBuffer->endOffset = mBuffer->used;
	mBuffer->used += padded_size;

	void* allocateAt = reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->endOffset;
	auto temp = new (allocateAt) ItemContainer<T>{std::move(op)};
	temp->header = {.type = T, .size = padded_size};
	}

	void resize(size_t newsize) {
	// Add the header size to newsize
	const size_t adjustedSize = newsize + STARTING_SIZE;

	if (adjustedSize < size()) {
	// todo: throw?
	return;
	}
	if (newsize == 0) {
	free(mBuffer);
	mBuffer = nullptr;
	} else {
	if (mBuffer) {
	mBuffer = reinterpret_cast<BufferHeader*>(realloc(mBuffer, adjustedSize));
	mBuffer->capacity = adjustedSize;
	} else {
	mBuffer = new (malloc(adjustedSize)) BufferHeader();
	mBuffer->capacity = adjustedSize;
	mBuffer->used = STARTING_SIZE;
	mBuffer->startOffset = STARTING_SIZE;
	}
	}
	}

	template <typename F>
	void for_each(F&& f) const {
	do_for_each(std::forward<F>(f), ItemTypesSequence{});
	}

	void clear();

	ItemHeader* first() const { return isEmpty() ? nullptr : itemAt(mBuffer->startOffset); }

	ItemHeader* last() const { return isEmpty() ? nullptr : itemAt(mBuffer->endOffset); }

	class sentinal {
	public:
	explicit sentinal(const uint8_t* end) : end(end) {}
	private:
	const uint8_t* const end;
	};

	sentinal end() const {
	return sentinal{end_ptr()};
	}

	template <ItemTypes T>
	class filtered_iterator {
	public:
	explicit filtered_iterator(uint8_t* start, const uint8_t* end)
	: mCurrent(start), mEnd(end) {
	ItemHeader* header = reinterpret_cast<ItemHeader*>(mCurrent);
	if (header->type != T) {
	advance();
	}
	}

	filtered_iterator& operator++() {
	advance();
	return *this;
	}

	// Although this iterator self-terminates, we need a placeholder to compare against
	// to make for-each loops happy
	bool operator!=(const sentinal& other) const {
	return mCurrent != mEnd;
	}

	ItemContainer<T>& operator*() {
	return reinterpret_cast<ItemContainer<T>>(mCurrent);
	}
	private:
	void advance() {
	ItemHeader* header = reinterpret_cast<ItemHeader*>(mCurrent);
	do {
	mCurrent += header->size;
	header = reinterpret_cast<ItemHeader*>(mCurrent);
	} while (mCurrent != mEnd && header->type != T);
	}
	uint8_t* mCurrent;
	const uint8_t* const mEnd;
	};

	template <ItemTypes T>
	class filtered_view {
	public:
	explicit filtered_view(uint8_t* start, const uint8_t* end) : mStart(start), mEnd(end) {}

	filtered_iterator<T> begin() const {
	return filtered_iterator<T>{mStart, mEnd};
	}

	sentinal end() const {
	return sentinal{mEnd};
	}
	private:
	uint8_t* mStart;
	const uint8_t* const mEnd;
	};

	template <ItemTypes T>
	filtered_view<T> filter() const {
	return filtered_view<T>{start_ptr(), end_ptr()};
	}

	private:

	uint8_t* start_ptr() const {
	return reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->startOffset;
	}

	const uint8_t* end_ptr() const {
	return reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->used;
	}

	template <typename F, std::size_t... I>
	void do_for_each(F&& f, std::index_sequence<I...>) const {
	// Validate we're not empty
	if (isEmpty()) return;

	// Setup the jump table, mapping from each type to a springboard that invokes the template
	// function with the appropriate concrete type
	using F_PTR = decltype(&f);
	using THUNK = void ()(F_PTR, void);
	static constexpr auto jump = std::array<THUNK, sizeof...(I)>{[](F_PTR fp, void* t) {
	(fp)(reinterpret_cast<const ItemContainer<static_cast<ItemTypes>(I)>>(t));
	}...};

	// Do the actual iteration of each item
	uint8_t* current = start_ptr();
	const uint8_t* end = end_ptr();
	while (current != end) {
	auto header = reinterpret_cast<ItemHeader*>(current);
	// `f` could be a destructor, so ensure all accesses to the OP happen prior to invoking
	// `f`
	auto it = (void*)current;
	current += header->size;
	jump[static_cast<int>(header->type)](&f, it);
	}
	}

	void destroy() {
	clear();
	resize(0);
	}

	bool offsetIsValid(size_t offset) const {
	return offset >= mBuffer->startOffset && offset < mBuffer->used;
	}

	ItemHeader* itemAt(size_t offset) const {
	if (!offsetIsValid(offset)) return nullptr;
	return reinterpret_cast<ItemHeader>(reinterpret_cast<uint8_t>(mBuffer) + offset);
	}

	bool isEmpty() const { return mBuffer == nullptr \|\| mBuffer->used == STARTING_SIZE; }

	BufferHeader* mBuffer = nullptr;
	};

	template <typename ItemTypes, template <ItemTypes> typename ItemContainer, typename BufferHeader,
	typename ItemTypeSequence>
	void OpBuffer<ItemTypes, ItemContainer, BufferHeader, ItemTypeSequence>::clear() {

	// Don't need to do anything if we don't have a buffer
	if (!mBuffer) return;

	for_each([](auto op) {
	using T = std::remove_reference_t<decltype(*op)>;
	op->~T();
	});
	mBuffer->used = STARTING_SIZE;
	mBuffer->startOffset = STARTING_SIZE;
	mBuffer->endOffset = 0;
	}

	} // namespace android::uirenderer