知识大全 C#使用BerkeleyDB操作简介

Posted 2022-07-17 数据库

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Berkeley DB是历史悠久的嵌入式数据库系统主要应用在UNIX/LINUX操作系统上 Berkeley DB的存储的是key/value键值对可以理解为硬盘上的超级hash表其可以管理 TB数据而且能支撑几千个并发访问目前Berkeley DB有C++版和Java版所以我们需要一个访问的中间转换已经有人发布了C#的API 可以从 Berkeley DB for NET 上面找到现在最新版是版本可以支持和版本篇将以版做实例 BerkeleyDB的版本可以在 db/l下载当前最新版本为版 C++版的Berkeley DB可以在 db/db/l这里下载 By Birdshover@ 博客园下载到Berkeley DB for Net的API——libdb dotnet_ _ zip后就可以开始使用了首先在libdb dotnet_ _ zip解压缩的bin目录找到libdb_dotNET dll 这个就是版本使用的dll 新建项目引用这个dll 注意自己编译源码可能会编译不过主要是因为里面一些委托和委托的参数可见性不一致造成的把那些参数用到的class 或者struct都调成public即可 BerkeleyDB的数据库操作需要借助DbBTree类因此需要先得到DbBTree的实例但是DbBTree类会对其它几个类有依赖必须依赖其它几个类才能创建下面代码就是初始化得到DbBTree实例的一个过程 /// <summary> /// 数据库目录 /// </summary> private string directory; /// <summary> /// 数据库文件名 /// </summary> private string dbName; private DbBTree btree; private Txn txn; private Db db; private Env env; /// <summary> /// 初始化 /// </summary> private void Init() env = new Env(EnvCreateFlags None); Env OpenFlags envFlags = Env OpenFlags Create | Env OpenFlags InitLock | Env OpenFlags InitLog | Env OpenFlags InitMPool | Env OpenFlags InitTxn | Env OpenFlags Recover; env Open(directory envFlags ); txn = env TxnBegin(null Txn BeginFlags None); db = env CreateDatabase(DbCreateFlags None); btree = (DbBTree)db Open(txn dbName null DbType BTree Db OpenFlags Create ); 另外Berkeley DB数据库的操作需要借助于序列化 /// <summary> /// 二进制序列化 /// </summary> private BinaryFormatter formatter; /// <summary> /// 键内存流 /// </summary> private MemoryStream keyStream; /// <summary> /// 内容内存流 /// </summary> private MemoryStream dataStream; private void StreamInit() formatter = new BinaryFormatter(); keyStream = new MemoryStream(); dataStream = new MemoryStream(); Berkeley DB是键值数据库因此定义一个获取键接口 public interface IPut string Key get; 一数据库的保存与更新 public bool Set(IPut put) Reset(); keyStream Position = ; formatter Serialize(keyStream put Key); DbEntry key = DbEntry InOut(keyStream GetBuffer() (int)keyStream Position); dataStream Position = ; formatter Serialize(dataStream put); DbEntry data = DbEntry InOut(dataStream GetBuffer() (int)dataStream Position); WriteStatus status = btree Put(txn ref key ref data); switch (status) case WriteStatus Success: return true; case WriteStatus NotFound: case WriteStatus KeyExist: default: return false; 上述代码就可以保存键值显示对键值进行序列化然后再保存保存完有三个状态可以一一处理二数据库的删除删除最为简单 public bool Remove(IPut put) keyStream Position = ; formatter Serialize(keyStream put Key); DbEntry key = DbEntry InOut(keyStream GetBuffer() (int)keyStream Position); DeleteStatus status = btree Delete(txn ref key); switch (status) case DeleteStatus NotFound: case DeleteStatus Success: return true; case DeleteStatus KeyEmpty: default: return false; 三关于添加和删除添加和删除并没有真正得进行添加和删除必须执行Commit操作 private bool isit = false; public void Commit() txn Commit(Txn CommitMode None); isit = true; 四寻找键用键查询值和hash表一样使用 public bool Get(ref IPut put) keyStream Position = ; formatter Serialize(keyStream put Key); DbEntry key = DbEntry InOut(keyStream GetBuffer() (int)keyStream Position); dataStream SetLength(dataStream Capacity); DbEntry data = DbEntry Out(dataStream GetBuffer()); while (true) ReadStatus status = btree Get(txn ref key ref data DbFile ReadFlags None); switch (status) case ReadStatus Success: dataStream Position = ; dataStream SetLength(data Size); put = (IPut)formatter Deserialize(dataStream); return true; case ReadStatus BufferSmall: //扩容 if (key Buffer Length < key Size) keyStream SetLength(key Size); key = DbEntry Out(keyStream GetBuffer()); if (data Buffer Length < data Size) dataStream SetLength(data Size); data = DbEntry Out(dataStream GetBuffer()); continue; case ReadStatus NotFound: case ReadStatus KeyEmpty: default: return false; 五遍历 public List<IPut> Find() List<IPut> custList = new List<IPut>(); using (DbBTreeCursor cursor = btree OpenCursor(txn DbFileCursor CreateFlags None)) IPut cust = null; while (GetNextRecord(cursor ref cust)) custList Add(cust); return custList; private bool GetNextRecord(DbBTreeCursor cursor ref IPut cust) ReadStatus status; keyStream SetLength(keyStream Capacity); dataStream SetLength(dataStream Capacity); DbEntry key = DbEntry Out(keyStream GetBuffer()); DbEntry data = DbEntry Out(dataStream GetBuffer()); do status = cursor Get(ref key ref data DbFileCursor GetMode Next DbFileCursor ReadFlags None); switch (status) case ReadStatus NotFound: return false; case ReadStatus KeyEmpty: continue; // skip deleted records case ReadStatus BufferSmall: if (key Buffer Length < key Size) keyStream SetLength(key Size); key = DbEntry Out(keyStream GetBuffer()); if (data Buffer Length < data Size) dataStream SetLength(data Size); data = DbEntry Out(dataStream GetBuffer()); continue; case ReadStatus Success: dataStream Position = ; dataStream SetLength(data Size); cust = (IPut)formatter Deserialize(dataStream); return true; default: return false; while (true); 六完整操作封装 public interface IPut string Key get; public class BDBManager : IDisposable /// <summary> /// 数据库目录 /// </summary> private string directory; /// <summary> /// 数据库文件名 /// </summary> private string dbName; private DbBTree btree; private Txn txn; private Db db; private Env env; /// <summary> /// 二进制序列化 /// </summary> private BinaryFormatter formatter; /// <summary> /// 键内存流 /// </summary> private MemoryStream keyStream; /// <summary> /// 内容内存流 /// </summary> private MemoryStream dataStream; public BDBManager(string directory string dbName) this directory = directory; this dbName = dbName; Init(); StreamInit(); public bool Set(IPut put) Reset(); keyStream Position = ; formatter Serialize(keyStream put Key); DbEntry key = DbEntry InOut(keyStream GetBuffer() (int)keyStream Position); dataStream Position = ; formatter Serialize(dataStream put); DbEntry data = DbEntry InOut(dataStream GetBuffer() (int)dataStream Position); WriteStatus status = btree Put(txn ref key ref data); switch (status) case WriteStatus Success: return true; case WriteStatus NotFound: case WriteStatus KeyExist: default: return false; private bool isit = false; public void Commit() txn Commit(Txn CommitMode None); isit = true; public List<IPut> Find() List<IPut> custList = new List<IPut>(); using (DbBTreeCursor cursor = btree OpenCursor(txn DbFileCursor CreateFlags None)) IPut cust = null; while (GetNextRecord(cursor ref cust)) custList Add(cust); return custList; public bool Get(ref IPut put) keyStream Position = ; formatter Serialize(keyStream put Key); DbEntry key = DbEntry InOut(keyStream GetBuffer() (int)keyStream Position); dataStream SetLength(dataStream Capacity); DbEntry data = DbEntry Out(dataStream GetBuffer()); while (true) ReadStatus status = btree Get(txn ref key ref data DbFile ReadFlags None); switch (status) case ReadStatus Success: dataStream Position = ; dataStream SetLength(data Size); put = (IPut)formatter Deserialize(dataStream); return true; case ReadStatus BufferSmall: //扩容 if (key Buffer Length < key Size) keyStream SetLength(key Size); key = DbEntry Out(keyStream GetBuffer()); if (data Buffer Length < data Size) dataStream SetLength(data Size); data = DbEntry Out(dataStream GetBuffer()); continue; case ReadStatus NotFound: case ReadStatus KeyEmpty: default: return false; public bool Remove(IPut put) Reset(); keyStream Position = ; formatter Serialize(keyStream put Key); DbEntry key = DbEntry InOut(keyStream GetBuffer() (int)keyStream Position); DeleteStatus status = btree Delete(txn ref key); switch (status) case DeleteStatus NotFound: case DeleteStatus Success: return true; case DeleteStatus KeyEmpty: default: return false; public void Dispose() if (!isit) Commit(); db Close(); db Close(); private void Reset() isit = false; private void Init() env = new Env(EnvCreateFlags None); Env OpenFlags envFlags = Env OpenFlags Create | Env OpenFlags InitLock | Env OpenFlags InitLog | Env OpenFlags InitMPool | Env OpenFlags InitTxn | Env OpenFlags Recover; env Open(directory envFlags ); txn = env TxnBegin(null Txn BeginFlags None); db = env CreateDatabase(DbCreateFlags None); btree = (DbBTree)db Open(txn dbName null DbType BTree Db OpenFlags Create ); private void StreamInit() formatter = new BinaryFormatter(); keyStream = new MemoryStream(); dataStream = new MemoryStream(); private bool GetNextRecord(DbBTreeCursor cursor ref IPut cust) ReadStatus status; keyStream SetLength(keyStream Capacity); dataStream SetLength(dataStream Capacity); DbEntry key = DbEntry Out(keyStream GetBuffer()); DbEntry data = DbEntry Out(dataStream GetBuffer()); do status = cursor Get(ref key ref data DbFileCursor GetMode Next DbFileCursor ReadFlags None); switch (status) case ReadStatus NotFound: return false; case ReadStatus KeyEmpty: continue; // skip deleted records case ReadStatus BufferSmall: if (key Buffer Length < key Size) keyStream SetLength(key Size); key = DbEntry Out(keyStream GetBuffer()); if (data Buffer Length < data Size) dataStream SetLength(data Size); data = DbEntry Out(dataStream GetBuffer()); continue; case ReadStatus Success: dataStream Position = ; dataStream SetLength(data Size); cust = (IPut)formatter Deserialize(dataStream); return true; default: return false; while (true); 调用方法首先要有一个写入的实体类必须可以序列化并且实现IPut接口 [Serializable()] class Item : IPut public string Name get; set; public string Text get; set; public int ID get; set; public override string ToString() return string Format( ID: Key: ID Name); public string Key get return Name; 操作 using (BDBManager manager = new BDBManager( db db dat )) bool success = manager Set(new Item() ID = Name = Test Text = ); Console WriteLine(string Format( set is success)); using (BDBManager manager = new BDBManager( db db dat )) IPut put = new Item() Name = Test ; bool success = manager Get(ref put); Console WriteLine(string Format( read is item : success put ToString())); using (BDBManager manager = new BDBManager( db db dat )) IPut put = new Item() Name = Test ; bool success = manager Remove(put); Console WriteLine(string Format( remove is item : success put ToString())); using (BDBManager manager = new BDBManager( db db dat )) List<IPut> list = manager Find(); foreach (var item in list) Console WriteLine(item ToString()); Console WriteLine( end ); Console ReadKey(); cha138/Article/program/net/201311/12343