simple_allocator.h

// Copyright 2025 The Pigweed Authors
//
// 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
//
//     https://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 <cstddef>
#include <optional>
 
#include "pw_bytes/span.h"
#include "pw_multibuf/v1_adapter/allocator.h"
#include "pw_multibuf/v1_adapter/internal/chunk_allocator.h"
#include "pw_multibuf/v1_adapter/multibuf.h"
#include "pw_sync/lock_annotations.h"
#include "pw_sync/mutex.h"
 
namespace pw::multibuf::v1_adapter {
 
class SimpleAllocator : public MultiBufAllocator {
 public:
  SimpleAllocator(ByteSpan region,
                  Allocator& metadata_allocator,
                  size_t alignment = 1)
      : chunk_allocator_(region, metadata_allocator, alignment) {}
 
  [[nodiscard]] bool TryReserveRegions(size_t num_regions)
      PW_LOCKS_EXCLUDED(mutex_);
 
 protected:
  void Reset() PW_LOCKS_EXCLUDED(mutex_);
 
 private:
  class SimpleChunkAllocator : public internal::ChunkAllocator {
   public:
    SimpleChunkAllocator(ByteSpan region,
                         Allocator& metadata_allocator,
                         size_t alignment);
 
    ~SimpleChunkAllocator() override;
 
    [[nodiscard]] bool Init();
 
    size_t CountChunks(size_t desired_size);
 
    [[nodiscard]] bool TryReserveRegions(size_t num_regions);
 
    void Reset();
 
   private:
    using iterator = DynamicVector<Region>::iterator;
 
    Region* AllocateRegion(size_t min_size, size_t desired_size) override;
 
    size_t TryDeallocateRegion(void* ptr) override;
 
    std::tuple<iterator, iterator> Split(iterator iter, size_t offset);
 
    iterator Merge(iterator left, iterator right);
 
    size_t available_ = 0;
 
    DynamicVector<Region> subregions_;
  };
 
  std::optional<MultiBuf> DoAllocate(size_t min_size,
                                     size_t desired_size,
                                     bool contiguous) override
      PW_LOCKS_EXCLUDED(mutex_);
 
  std::optional<size_t> DoGetBackingCapacity() override
      PW_LOCKS_EXCLUDED(mutex_);
 
  pw::sync::Mutex mutex_;
 
  SimpleChunkAllocator chunk_allocator_ PW_GUARDED_BY(mutex_);
};
 
 
}  // namespace pw::multibuf::v1_adapter