first-fit-top.h

Go to the documentation of this file.

/*
 * This file is part of the µOS++ project (https://micro-os-plus.github.io/).
 * Copyright (c) 2016-2025 Liviu Ionescu. All rights reserved.
 *
 * Permission to use, copy, modify, and/or distribute this software
 * for any purpose is hereby granted, under the terms of the MIT license.
 *
 * If a copy of the license was not distributed with this file, it can
 * be obtained from https://opensource.org/licenses/mit.
 */
 
#ifndef CMSIS_PLUS_MEMORY_FIRST_FIT_TOP_H_
#define CMSIS_PLUS_MEMORY_FIRST_FIT_TOP_H_
 
// ----------------------------------------------------------------------------
 
#if defined(__cplusplus)
 
// ----------------------------------------------------------------------------
 
#include <cmsis-plus/rtos/os.h>
 
// ----------------------------------------------------------------------------
 
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wc++98-compat"
#pragma clang diagnostic ignored "-Wdocumentation-unknown-command"
#endif
 
// ----------------------------------------------------------------------------
 
namespace os
{
  namespace memory
  {
 
    // ========================================================================
 
    class first_fit_top : public rtos::memory::memory_resource
    {
    public:
      first_fit_top (void* addr, std::size_t bytes);
 
      first_fit_top (const char* name, void* addr, std::size_t bytes);
 
    protected:
      first_fit_top () = default;
 
      first_fit_top (const char* name);
 
    public:
      // The rule of five.
      first_fit_top (const first_fit_top&) = delete;
      first_fit_top (first_fit_top&&) = delete;
      first_fit_top&
      operator= (const first_fit_top&)
          = delete;
      first_fit_top&
      operator= (first_fit_top&&)
          = delete;
 
      virtual ~first_fit_top () override;
 
    protected:
#pragma GCC diagnostic push
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wpadded"
#elif defined(__GNUC__)
#pragma GCC diagnostic ignored "-Wpadded"
#endif
 
      // A 'chunk' is where the user block resides; it keeps track of size,
      // it accommodates alignment and helps maintain the free list.
      typedef struct chunk_s
      {
        // The actual chunk size, in bytes;
        // the next chunk starts exactly after this number of bytes.
        // This is the only overhead that applies to all allocated blocks.
        std::size_t size;
 
        // For allocated chunks, here, or at the next address that
        // satisfies the required alignment, starts the payload.
 
        // When the chunk is in the free list, instead of the
        // payload, here is a pointer to the next chunk.
        /* struct */ chunk_s* next;
      } chunk_t;
 
#pragma GCC diagnostic pop
 
      void
      internal_construct_ (void* addr, std::size_t bytes);
 
      void
      internal_reset_ (void) noexcept;
 
      void*
      internal_align_ (chunk_t* chunk, std::size_t bytes,
                       std::size_t alignment);
 
      virtual void*
      do_allocate (std::size_t bytes, std::size_t alignment) override;
 
      virtual void
      do_deallocate (void* addr, std::size_t bytes,
                     std::size_t alignment) noexcept override;
 
      virtual std::size_t
      do_max_size (void) const noexcept override;
 
      virtual void
      do_reset (void) noexcept override;
 
    protected:
      // Offset of payload inside the chunk.
      static constexpr std::size_t chunk_offset = offsetof (chunk_t, next);
      static constexpr std::size_t chunk_align = sizeof (void*);
      static constexpr std::size_t chunk_minsize = sizeof (chunk_t);
 
      static constexpr std::size_t block_minsize = sizeof (void*);
 
      // Extra padding from chunk to block.
      static constexpr std::size_t
      calc_block_padding (std::size_t block_align)
      {
        return os::rtos::memory::max (block_align, chunk_align) - chunk_align;
      }
 
      // The minimum chunk to it the block.
      static constexpr std::size_t
      calc_block_minchunk (std::size_t block_padding)
      {
        return chunk_offset + block_minsize + block_padding;
      }
 
      void* arena_addr_ = nullptr;
      // No need for arena_size_bytes_, use total_bytes_.
 
      chunk_t* free_list_ = nullptr;
 
    };
 
    // ========================================================================
 
    template <std::size_t N>
    class first_fit_top_inclusive : public first_fit_top
    {
    public:
      static const std::size_t bytes = N;
 
      first_fit_top_inclusive (void);
 
      first_fit_top_inclusive (const char* name);
 
    public:
      // The rule of five.
      first_fit_top_inclusive (const first_fit_top_inclusive&) = delete;
      first_fit_top_inclusive (first_fit_top_inclusive&&) = delete;
      first_fit_top_inclusive&
      operator= (const first_fit_top_inclusive&)
          = delete;
      first_fit_top_inclusive&
      operator= (first_fit_top_inclusive&&)
          = delete;
 
      virtual ~first_fit_top_inclusive ();
 
    protected:
      char arena_[bytes];
 
    };
 
    // ========================================================================
 
    template <typename A = os::rtos::memory::allocator<char>>
    class first_fit_top_allocated : public first_fit_top
    {
    public:
      using value_type = char;
 
      using allocator_type = A;
 
      using allocator_traits = std::allocator_traits<A>;
 
      // It is recommended to have the same type, but at least the types
      // should have the same size.
      static_assert (
          sizeof (value_type)
              == sizeof (typename allocator_traits::value_type),
          "The allocator must be parametrised with a type of same size.");
 
      first_fit_top_allocated (std::size_t bytes,
                               const allocator_type& allocator
                               = allocator_type ());
 
      first_fit_top_allocated (const char* name, std::size_t bytes,
                               const allocator_type& allocator
                               = allocator_type ());
 
    public:
      // The rule of five.
      first_fit_top_allocated (const first_fit_top_allocated&) = delete;
      first_fit_top_allocated (first_fit_top_allocated&&) = delete;
      first_fit_top_allocated&
      operator= (const first_fit_top_allocated&)
          = delete;
      first_fit_top_allocated&
      operator= (first_fit_top_allocated&&)
          = delete;
 
      virtual ~first_fit_top_allocated ();
 
    protected:
      allocator_type* allocator_ = nullptr;
 
    };
 
    // ------------------------------------------------------------------------
  } /* namespace memory */
} /* namespace os */
 
// ===== Inline & template implementations ====================================
 
namespace os
{
  namespace memory
  {
 
    // ========================================================================
 
    inline first_fit_top::first_fit_top (const char* name)
        : rtos::memory::memory_resource{ name }
    {
    }
 
    inline first_fit_top::first_fit_top (void* addr, std::size_t bytes)
        : first_fit_top{ nullptr, addr, bytes }
    {
    }
 
    inline first_fit_top::first_fit_top (const char* name, void* addr,
                                         std::size_t bytes)
        : rtos::memory::memory_resource{ name }
    {
      trace::printf ("%s(%p,%u) @%p %s\n", __func__, addr, bytes, this,
                     this->name ());
 
      internal_construct_ (addr, bytes);
    }
 
    // ========================================================================
 
    template <std::size_t N>
    inline first_fit_top_inclusive<N>::first_fit_top_inclusive ()
        : first_fit_top_inclusive (nullptr)
    {
    }
 
    template <std::size_t N>
    inline first_fit_top_inclusive<N>::first_fit_top_inclusive (
        const char* name)
        : first_fit_top{ name }
    {
      trace::printf ("%s() @%p %s\n", __func__, this, this->name ());
 
      internal_construct_ (&arena_[0], bytes);
    }
 
    template <std::size_t N>
    first_fit_top_inclusive<N>::~first_fit_top_inclusive ()
    {
      trace::printf ("%s() @%p %s\n", __func__, this, this->name ());
    }
 
    // ========================================================================
 
    template <typename A>
    inline first_fit_top_allocated<A>::first_fit_top_allocated (
        std::size_t bytes, const allocator_type& allocator)
        : first_fit_top_allocated (nullptr, bytes, allocator)
    {
    }
 
    template <typename A>
    first_fit_top_allocated<A>::first_fit_top_allocated (
        const char* name, std::size_t bytes, const allocator_type& allocator)
        : first_fit_top{ name }
    {
      trace::printf ("%s(%u) @%p %s\n", __func__, bytes, this, this->name ());
 
      // Remember the allocator, it'll be used by the destructor.
      allocator_ = static_cast<allocator_type*> (
          &const_cast<allocator_type&> (allocator));
 
      void* addr = allocator_->allocate (bytes);
      if (addr == nullptr)
        {
          estd::__throw_bad_alloc ();
        }
 
      internal_construct_ (addr, bytes);
    }
 
    template <typename A>
    first_fit_top_allocated<A>::~first_fit_top_allocated ()
    {
      trace::printf ("%s() @%p %s\n", __func__, this, this->name ());
 
      // Skip in case a derived class did the deallocation.
      if (allocator_ != nullptr)
        {
          allocator_->deallocate (
              static_cast<typename allocator_traits::pointer> (arena_addr_),
              total_bytes_);
 
          // Prevent another deallocation.
          allocator_ = nullptr;
        }
    }
 
    // ------------------------------------------------------------------------
 
  } /* namespace memory */
} /* namespace os */
 
#pragma GCC diagnostic pop
 
// ----------------------------------------------------------------------------
 
#endif /* __cplusplus */
 
// ----------------------------------------------------------------------------
 
#endif /* CMSIS_PLUS_MEMORY_FIRST_FIT_TOP_H_ */