作者：heiyeluren
tmdb 是类似于DBM的小型Hash KV数据库 (Mini NoSQL DB)
TieMa?(Tiny&Mini) TDBM (like dbm-style database)(ANSI C, GCC require)
Last update：2010/7/12 v0.0.1
参考代码：https://github.com/heiyeluren/tmdb/blob/master/src/tmdb.h
The tmdb use static hash table to organize data, doing so mainly to faster query to the data, but the problem caused by the less able to accommodate the data. Currently holds the record total of 65,536, each Key length does not exceed 64 bytes.
Data storage using index files and data files separate ways, so in order to ensure the growth of the index records would not cause the file to the increase.
Hash table using open zipper method of conflict to resolve, using the more efficient hash function:
h = ((h <<5) + h) ^ c'', with a starting hash of 5381.
Describe the entire data storage structure:
[ Index structure describe ] Index File: xxx.tdi
Index File Struct:
+-----------+----------------------+--------------+----------------+
| Header | Key ptr buckets | Key Record 1 |Key Record 2 .. |
+-----------+----------------------+--------------+----------------+
256Bytes 262144Bytes(256KB) 76Bytes 76Bytes
Index header
+--------------+-------------------------+
| Record total | Free space |
+--------------+-------------------------+
4Bytes 252Bytes
Index key buckets
+----------+----------+----------+--------------+
| Key ptr1 | Key ptr2 | Key ptr3 | Key ptrN .. |
+----------+----------+----------+--------------+
4Bytes 4Bytes 4Bytes 4Bytes ...
Index key record
+-------+--------------+----------+----------+
| Flag | Key | Data ptr | Next ptr |
+-------+--------------+----------+----------+
4Bytes 64Bytes 4Bytes 4Bytes
[ Data structure describe ] Data File: xxx.tdb
Data File structure:
+----------------+----------------+-----------------+
| Header | Data Record 1 |Data Record 2.. |
+----------------+----------------+-----------------+
256bytes dynamics length dynamics length
Data record
+--------+-------+------------------+----------+
| Flag | len | Data | Next ptr |
+--------+-------+------------------+----------+
4Bytes 4Bytes dynamics length 4Bytes
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