1 // Copyright 2024 The Pigweed Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); you may not 4 // use this file except in compliance with the License. You may obtain a copy of 5 // the License at 6 // 7 // https://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 11 // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 12 // License for the specific language governing permissions and limitations under 13 // the License. 14 #pragma once 15 16 #include <cstddef> 17 18 #include "pw_assert/assert.h" 19 #include "pw_preprocessor/compiler.h" 20 #include "pw_result/result.h" 21 22 namespace pw::allocator { 23 24 /// Describes the layout of a block of memory. 25 /// 26 /// Layouts are passed to allocators, and consist of a (possibly padded) size 27 /// and a power-of-two alignment no larger than the size. Layouts can be 28 /// constructed for a type `T` using `Layout::Of`. 29 /// 30 /// Example: 31 /// 32 /// @code{.cpp} 33 /// struct MyStruct { 34 /// uint8_t field1[3]; 35 /// uint32_t field2[3]; 36 /// }; 37 /// constexpr Layout layout_for_struct = Layout::Of<MyStruct>(); 38 /// @endcode 39 class Layout { 40 public: Layout()41 constexpr Layout() : Layout(0) {} Layout(size_t size)42 constexpr explicit Layout(size_t size) 43 : Layout(size, alignof(std::max_align_t)) {} Layout(size_t size,size_t alignment)44 constexpr Layout(size_t size, size_t alignment) 45 : size_(size), alignment_(alignment) {} 46 47 /// Creates a Layout for the given type. 48 template <typename T> Of()49 static constexpr Layout Of() { 50 return Layout(sizeof(T), alignof(T)); 51 } 52 53 /// If the result is okay, returns its contained layout; otherwise, returns a 54 /// default layout. Unwrap(const Result<Layout> & result)55 static constexpr Layout Unwrap(const Result<Layout>& result) { 56 return result.ok() ? (*result) : Layout(); 57 } 58 Extend(size_t size)59 constexpr Layout Extend(size_t size) const { 60 PW_ASSERT(!PW_ADD_OVERFLOW(size, size_, &size)); 61 return Layout(size, alignment_); 62 } 63 size()64 constexpr size_t size() const { return size_; } alignment()65 constexpr size_t alignment() const { return alignment_; } 66 67 private: 68 size_t size_; 69 size_t alignment_; 70 }; 71 72 inline bool operator==(const Layout& lhs, const Layout& rhs) { 73 return lhs.size() == rhs.size() && lhs.alignment() == rhs.alignment(); 74 } 75 76 inline bool operator!=(const Layout& lhs, const Layout& rhs) { 77 return !(lhs == rhs); 78 } 79 80 } // namespace pw::allocator 81