198   for (auto first = files_.begin(),  in Init()  local
199             second = first + (first == files_.end() ? 0 : 1);  in Init()
200        first != files_.end() && second != files_.end();  in Init()
201        second = first + 1) {  in Init()
202     auto first_begin = first->extents[0].start_block();  in Init()
203     auto first_end = first_begin + first->extents[0].num_blocks();  in Init()
208       first = files_.erase(first);  in Init()
215         first = files_.erase(first);  in Init()
218         first->extents[0].set_num_blocks(second_begin - first_begin);  in Init()
219         ++first;  in Init()
222       ++first;  in Init()