lifo.cpp

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/*
 * 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.
 */
 
#if defined(OS_USE_OS_APP_CONFIG_H)
#include <cmsis-plus/os-app-config.h>
#endif
 
#include <cmsis-plus/memory/lifo.h>
#include <memory>
 
// ----------------------------------------------------------------------------
 
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wc++98-compat"
#endif
 
// ----------------------------------------------------------------------------
 
namespace os
{
  namespace memory
  {
 
    // ========================================================================
 
    lifo::~lifo ()
    {
      trace::printf ("lifo::%s() @%p %s\n", __func__, this, this->name ());
    }
 
#pragma GCC diagnostic push
// Needed because 'alignment' is used only in trace calls.
#pragma GCC diagnostic ignored "-Wunused-parameter"
 
    void*
    lifo::do_allocate (std::size_t bytes, std::size_t alignment)
    {
      std::size_t block_padding = calc_block_padding (alignment);
      std::size_t alloc_size = rtos::memory::align_size (bytes, chunk_align);
      alloc_size += block_padding;
      alloc_size += chunk_offset;
 
      std::size_t block_minchunk = calc_block_minchunk (block_padding);
      alloc_size = os::rtos::memory::max (alloc_size, block_minchunk);
 
      chunk_t* chunk = nullptr;
 
      while (true)
        {
          // Allocate only from the first block and only if it is
          // the really first in the arena; this prevents fragmentation.
          if (free_list_ == reinterpret_cast<chunk_t*> (arena_addr_))
            {
              chunk = free_list_;
 
              int rem = static_cast<int> (chunk->size - alloc_size);
              if (rem >= 0)
                {
                  if ((static_cast<std::size_t> (rem)) >= block_minchunk)
                    {
                      // If the chunk is larger than needed
                      // (at least one more chunk is available);
                      // break it into two chunks and return the top one.
 
                      // Shrink bottom chunk to remaining size.
                      chunk->size = static_cast<std::size_t> (rem);
 
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
#if defined(__clang__)
#pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
#endif
                      // Compute where top chunk starts.
                      chunk = reinterpret_cast<chunk_t*> (
                          reinterpret_cast<char*> (chunk) + rem);
#pragma GCC diagnostic pop
                      chunk->size = alloc_size;
 
                      // Splitting one chunk creates one more chunk.
                      ++free_chunks_;
                    }
                  else
                    {
                      // Found a chunk that is exactly the size or slightly
                      // larger than the requested size; return this chunk.
 
                      // Always at the list head.
                      // The next chunk becomes the first list element.
                      free_list_ = chunk->next;
 
                      // If this was the last chunk, the free list is empty.
                    }
                }
            }
 
          if (chunk != nullptr)
            {
              break;
            }
 
          if (out_of_memory_handler_ == nullptr)
            {
#if defined(OS_TRACE_LIBCPP_MEMORY_RESOURCE)
              trace::printf ("lifo::%s(%u,%u)=0 @%p %s\n", __func__, bytes,
                             alignment, this, this->name ());
#endif
 
              return nullptr;
            }
 
#if defined(OS_TRACE_LIBCPP_MEMORY_RESOURCE)
          trace::printf ("lifo::%s(%u,%u) @%p %s out of memory\n", __func__,
                         bytes, alignment, this, this->name ());
#endif
          out_of_memory_handler_ ();
 
          // If the handler returned, assume it freed some memory
          // and try again to allocate.
        }
 
      void* aligned_payload = internal_align_ (chunk, bytes, alignment);
 
#if defined(OS_TRACE_LIBCPP_MEMORY_RESOURCE)
      trace::printf ("lifo::%s(%u,%u)=%p,%u @%p %s\n", __func__, bytes,
                     alignment, aligned_payload, alloc_size, this, name ());
#endif
 
      return aligned_payload;
    }
 
#pragma GCC diagnostic pop
 
    // ------------------------------------------------------------------------
  } /* namespace memory */
} /* namespace os */
 
// ----------------------------------------------------------------------------