288 lines
8.9 KiB
C++
288 lines
8.9 KiB
C++
/*
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* Copyright (C) 2020 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <algorithm>
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#include <array>
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#include <cinttypes>
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#include <cstddef>
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#include <cstdlib>
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#include <type_traits>
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#include <utility>
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namespace android::uirenderer {
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template <typename T>
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struct OpBufferItemHeader {
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T type : 8;
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uint32_t size : 24;
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};
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struct OpBufferAllocationHeader {
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// Used size, including header size
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size_t used = 0;
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// Capacity, including header size
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size_t capacity = 0;
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// Offset relative to `this` at which the first item is
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size_t startOffset = 0;
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// Offset relative to `this` at which the last item is
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size_t endOffset = 0;
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};
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#define BE_OPBUFFERS_FRIEND() \
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template <typename ItemTypes, template <ItemTypes> typename, typename, typename> \
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friend class OpBuffer
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template <typename ItemTypes, template <ItemTypes> typename ItemContainer,
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typename BufferHeader = OpBufferAllocationHeader,
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typename ItemTypesSequence = std::make_index_sequence<static_cast<int>(ItemTypes::COUNT)>>
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class OpBuffer {
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// Instead of re-aligning individual inserts, just pad the size of everything
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// to a multiple of pointer alignment. This assumes we never work with doubles.
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// Which we don't.
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static constexpr size_t Alignment = alignof(void*);
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static constexpr size_t PadAlign(size_t size) {
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return (size + (Alignment - 1)) & -Alignment;
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}
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public:
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static constexpr auto STARTING_SIZE = PadAlign(sizeof(BufferHeader));
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using ItemHeader = OpBufferItemHeader<ItemTypes>;
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explicit OpBuffer() = default;
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// Prevent copying by default
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OpBuffer(const OpBuffer&) = delete;
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void operator=(const OpBuffer&) = delete;
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OpBuffer(OpBuffer&& other) {
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mBuffer = other.mBuffer;
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other.mBuffer = nullptr;
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}
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void operator=(OpBuffer&& other) {
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destroy();
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mBuffer = other.mBuffer;
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other.mBuffer = nullptr;
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}
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~OpBuffer() {
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destroy();
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}
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constexpr size_t capacity() const { return mBuffer ? mBuffer->capacity : 0; }
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constexpr size_t size() const { return mBuffer ? mBuffer->used : 0; }
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constexpr size_t remaining() const { return capacity() - size(); }
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// TODO: Add less-copy'ing variants of this. emplace_back? deferred initialization?
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template <ItemTypes T>
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void push_container(ItemContainer<T>&& op) {
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static_assert(alignof(ItemContainer<T>) <= Alignment);
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static_assert(offsetof(ItemContainer<T>, header) == 0);
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constexpr auto padded_size = PadAlign(sizeof(ItemContainer<T>));
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if (remaining() < padded_size) {
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resize(std::max(padded_size, capacity()) * 2);
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}
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mBuffer->endOffset = mBuffer->used;
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mBuffer->used += padded_size;
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void* allocateAt = reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->endOffset;
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auto temp = new (allocateAt) ItemContainer<T>{std::move(op)};
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temp->header = {.type = T, .size = padded_size};
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}
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void resize(size_t newsize) {
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// Add the header size to newsize
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const size_t adjustedSize = newsize + STARTING_SIZE;
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if (adjustedSize < size()) {
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// todo: throw?
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return;
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}
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if (newsize == 0) {
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free(mBuffer);
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mBuffer = nullptr;
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} else {
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if (mBuffer) {
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mBuffer = reinterpret_cast<BufferHeader*>(realloc(mBuffer, adjustedSize));
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mBuffer->capacity = adjustedSize;
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} else {
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mBuffer = new (malloc(adjustedSize)) BufferHeader();
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mBuffer->capacity = adjustedSize;
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mBuffer->used = STARTING_SIZE;
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mBuffer->startOffset = STARTING_SIZE;
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}
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}
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}
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template <typename F>
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void for_each(F&& f) const {
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do_for_each(std::forward<F>(f), ItemTypesSequence{});
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}
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void clear();
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ItemHeader* first() const { return isEmpty() ? nullptr : itemAt(mBuffer->startOffset); }
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ItemHeader* last() const { return isEmpty() ? nullptr : itemAt(mBuffer->endOffset); }
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class sentinal {
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public:
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explicit sentinal(const uint8_t* end) : end(end) {}
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private:
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const uint8_t* const end;
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};
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sentinal end() const {
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return sentinal{end_ptr()};
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}
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template <ItemTypes T>
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class filtered_iterator {
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public:
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explicit filtered_iterator(uint8_t* start, const uint8_t* end)
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: mCurrent(start), mEnd(end) {
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ItemHeader* header = reinterpret_cast<ItemHeader*>(mCurrent);
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if (header->type != T) {
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advance();
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}
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}
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filtered_iterator& operator++() {
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advance();
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return *this;
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}
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// Although this iterator self-terminates, we need a placeholder to compare against
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// to make for-each loops happy
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bool operator!=(const sentinal& other) const {
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return mCurrent != mEnd;
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}
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ItemContainer<T>& operator*() {
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return *reinterpret_cast<ItemContainer<T>*>(mCurrent);
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}
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private:
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void advance() {
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ItemHeader* header = reinterpret_cast<ItemHeader*>(mCurrent);
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do {
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mCurrent += header->size;
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header = reinterpret_cast<ItemHeader*>(mCurrent);
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} while (mCurrent != mEnd && header->type != T);
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}
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uint8_t* mCurrent;
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const uint8_t* const mEnd;
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};
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template <ItemTypes T>
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class filtered_view {
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public:
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explicit filtered_view(uint8_t* start, const uint8_t* end) : mStart(start), mEnd(end) {}
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filtered_iterator<T> begin() const {
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return filtered_iterator<T>{mStart, mEnd};
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}
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sentinal end() const {
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return sentinal{mEnd};
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}
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private:
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uint8_t* mStart;
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const uint8_t* const mEnd;
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};
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template <ItemTypes T>
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filtered_view<T> filter() const {
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return filtered_view<T>{start_ptr(), end_ptr()};
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}
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private:
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uint8_t* start_ptr() const {
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return reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->startOffset;
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}
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const uint8_t* end_ptr() const {
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return reinterpret_cast<uint8_t*>(mBuffer) + mBuffer->used;
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}
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template <typename F, std::size_t... I>
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void do_for_each(F&& f, std::index_sequence<I...>) const {
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// Validate we're not empty
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if (isEmpty()) return;
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// Setup the jump table, mapping from each type to a springboard that invokes the template
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// function with the appropriate concrete type
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using F_PTR = decltype(&f);
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using THUNK = void (*)(F_PTR, void*);
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static constexpr auto jump = std::array<THUNK, sizeof...(I)>{[](F_PTR fp, void* t) {
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(*fp)(reinterpret_cast<const ItemContainer<static_cast<ItemTypes>(I)>*>(t));
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}...};
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// Do the actual iteration of each item
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uint8_t* current = start_ptr();
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const uint8_t* end = end_ptr();
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while (current != end) {
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auto header = reinterpret_cast<ItemHeader*>(current);
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// `f` could be a destructor, so ensure all accesses to the OP happen prior to invoking
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// `f`
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auto it = (void*)current;
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current += header->size;
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jump[static_cast<int>(header->type)](&f, it);
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}
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}
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void destroy() {
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clear();
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resize(0);
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}
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bool offsetIsValid(size_t offset) const {
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return offset >= mBuffer->startOffset && offset < mBuffer->used;
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}
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ItemHeader* itemAt(size_t offset) const {
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if (!offsetIsValid(offset)) return nullptr;
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return reinterpret_cast<ItemHeader*>(reinterpret_cast<uint8_t*>(mBuffer) + offset);
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}
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bool isEmpty() const { return mBuffer == nullptr || mBuffer->used == STARTING_SIZE; }
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BufferHeader* mBuffer = nullptr;
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};
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template <typename ItemTypes, template <ItemTypes> typename ItemContainer, typename BufferHeader,
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typename ItemTypeSequence>
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void OpBuffer<ItemTypes, ItemContainer, BufferHeader, ItemTypeSequence>::clear() {
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// Don't need to do anything if we don't have a buffer
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if (!mBuffer) return;
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for_each([](auto op) {
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using T = std::remove_reference_t<decltype(*op)>;
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op->~T();
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});
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mBuffer->used = STARTING_SIZE;
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mBuffer->startOffset = STARTING_SIZE;
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mBuffer->endOffset = 0;
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}
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} // namespace android::uirenderer
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