1 // Copyright 2023 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_allocator/allocator.h" 19 #include "pw_allocator/capability.h" 20 21 namespace pw::allocator { 22 23 /// A memory allocator that always fails to allocate memory. 24 /// 25 /// A null allocator may be useful as part of a larger framework if allocation 26 /// should be disallowed under certain circumstances. For example, a function 27 /// that returns different allocators based on an input parameter may return a 28 /// null allocator when given an invalid or unsupported parameter value. 29 class NullAllocator : public Allocator { 30 public: 31 static constexpr Capabilities kCapabilities = 0; 32 33 // TODO(b/326509341): Make the constructor private once downstream consumers 34 // are migrated. 35 friend NullAllocator& GetNullAllocator(); NullAllocator()36 constexpr NullAllocator() : Allocator(kCapabilities) {} 37 38 private: 39 /// @copydoc Allocator::Allocate DoAllocate(Layout)40 void* DoAllocate(Layout) override { return nullptr; } 41 42 /// @copydoc Allocator::Deallocate DoDeallocate(void *)43 void DoDeallocate(void*) override {} 44 45 /// @copydoc Allocator::Deallocate DoDeallocate(void * ptr,Layout)46 void DoDeallocate(void* ptr, Layout) override { DoDeallocate(ptr); } 47 }; 48 49 /// Returns a reference to the NullAllocator singleton. 50 NullAllocator& GetNullAllocator(); 51 52 } // namespace pw::allocator 53