看leveldb，加中文注释，顺便学c++
看代码之前建议看看这个：
-> include/leveldb/status -> util/status -> util/arena -> include/leveldb/slice -> include/leveldb/filter_policy
-> util/hash -> util/filter_policy -> util/bloom -> util/logging -> util/mutexlock -> include/leveldb/cache
-> util/cache -> util/coding -> util/no_destructor -> include/leveldb/comparator/
-> util/comparator -> util/crc32c -> util/histogram -> include/leveldb/options -> util/options -> util/posix_logger
-> util/random -> include/leveldb/env -> util/env -> util/env_posix -> table/format -> table/block_builder
-> table/block -> table/filter_block -> include/leveldb/iterator -> table/iterator -> table/iterator_wrapper
-> table/merger -> table/two_level_iterator -> include/leveldb/table -> table/table
-> include/leveldb/table_builder -> table/table_builder -> db/skiplist -> db/log_format
-> db/log_reader -> db/log_writer -> db/filename -> include/leveldb/db -> db/dbformat
-> db/memtable -> db/snapshot -> db/table_cache -> db/version_edit -> db/version_set -> db/db_iter
-> include/leveldb/write_batch -> db/write_batch_internal -> db/write_batch -> db/builder -> db/db_impl
遇到问题看不懂，下面文章能给点提示: