Method reallocate

lib/pugixml/src/pugixml.cpp:7664–7709

		}

		void* reallocate(void* ptr, size_t old_size, size_t new_size)
		{
			// round size up to block alignment boundary
			old_size = (old_size + xpath_memory_block_alignment - 1) & ~(xpath_memory_block_alignment - 1);
			new_size = (new_size + xpath_memory_block_alignment - 1) & ~(xpath_memory_block_alignment - 1);

			// we can only reallocate the last object
			assert(ptr == 0 || static_cast<char*>(ptr) + old_size == &_root->data[0] + _root_size);

			// try to reallocate the object inplace
			if (ptr && _root_size - old_size + new_size <= _root->capacity)
			{
				_root_size = _root_size - old_size + new_size;
				return ptr;
			}

			// allocate a new block
			void* result = allocate(new_size);
			if (!result) return 0;

			// we have a new block
			if (ptr)
			{
				// copy old data (we only support growing)
				assert(new_size >= old_size);
				memcpy(result, ptr, old_size);

				// free the previous page if it had no other objects
				assert(_root->data == result);
				assert(_root->next);

				if (_root->next->data == ptr)
				{
					// deallocate the whole page, unless it was the first one
					xpath_memory_block* next = _root->next->next;

					if (next)
					{
						xml_memory::deallocate(_root->next);
						_root->next = next;
					}
				}
			}

			return result;
		}

		void revert(const xpath_allocator& state)
		{