Method do_allocate

system/lib/libcxx/src/memory_resource.cpp:345–397

}

void* unsynchronized_pool_resource::do_allocate(size_t bytes, size_t align) {
  // A pointer to allocated storage (6.6.4.4.1) with a size of at least bytes.
  // The size and alignment of the allocated memory shall meet the requirements for
  // a class derived from memory_resource (23.12).
  // If the pool selected for a block of size bytes is unable to satisfy the memory request
  // from its own internal data structures, it will call upstream_resource()->allocate()
  // to obtain more memory. If bytes is larger than that which the largest pool can handle,
  // then memory will be allocated using upstream_resource()->allocate().

  int i = __pool_index(bytes, align);
  if (i == __num_fixed_pools_)
    return __adhoc_pool_.__do_allocate(__res_, bytes, align);
  else {
    if (__fixed_pools_ == nullptr) {
      __fixed_pools_ =
          (__fixed_pool*)__res_->allocate(__num_fixed_pools_ * sizeof(__fixed_pool), alignof(__fixed_pool));
      __fixed_pool* first = __fixed_pools_;
      __fixed_pool* last  = __fixed_pools_ + __num_fixed_pools_;
      for (__fixed_pool* pool = first; pool != last; ++pool)
        ::new ((void*)pool) __fixed_pool;
    }
    void* result = __fixed_pools_[i].__try_allocate_from_vacancies();
    if (result == nullptr) {
      auto min = [](size_t a, size_t b) { return a < b ? a : b; };
      auto max = [](size_t a, size_t b) { return a < b ? b : a; };

      size_t prev_chunk_size_in_bytes  = __fixed_pools_[i].__previous_chunk_size_in_bytes();
      size_t prev_chunk_size_in_blocks = prev_chunk_size_in_bytes >> __log2_pool_block_size(i);

      size_t chunk_size_in_blocks;

      if (prev_chunk_size_in_blocks == 0) {
        size_t min_blocks_per_chunk = max(__min_bytes_per_chunk >> __log2_pool_block_size(i), __min_blocks_per_chunk);
        chunk_size_in_blocks        = min_blocks_per_chunk;
      } else {
        static_assert(__max_bytes_per_chunk <= SIZE_MAX - (__max_bytes_per_chunk / 4), "unsigned overflow is possible");
        chunk_size_in_blocks = prev_chunk_size_in_blocks + (prev_chunk_size_in_blocks / 4);
      }

      size_t max_blocks_per_chunk =
          min((__max_bytes_per_chunk >> __log2_pool_block_size(i)),
              min(__max_blocks_per_chunk, __options_max_blocks_per_chunk_));
      if (chunk_size_in_blocks > max_blocks_per_chunk)
        chunk_size_in_blocks = max_blocks_per_chunk;

      size_t block_size = __pool_block_size(i);

      size_t chunk_size_in_bytes = (chunk_size_in_blocks << __log2_pool_block_size(i));
      result                     = __fixed_pools_[i].__allocate_in_new_chunk(__res_, block_size, chunk_size_in_bytes);
    }
    return result;
  }
}

void unsynchronized_pool_resource::do_deallocate(void* p, size_t bytes, size_t align) {
  // Returns the memory at p to the pool. It is unspecified if,