l-db v1.0.1

Ldb

对 leveldb 的 node.js 封装，支持同步与异步调用，并支持事件监听

Install

npm install l-db --save

Documentation

Features

• 支持同步方法调用 leveldb api，代码逻更清析
• 也支持异步方法调用 leveldb api，使运行更高效
• 异步调用使用 Promise 对象，尽量使代码更清析
• 支持 Javascript ES6 中的 async await 方法

API

• new Ldb([options])

  • Ldb.prototype.open(location, [options])
  • Ldb.prototype.close()

  • Ldb.prototype.put( key, value ) or Ldb.prototype.put( json )

  • Ldb.prototype.del( key ) or Ldb.prototype.del( keys )

  • Ldb.prototype.get( key ) or Ldb.prototype.get( keys ) return values
  • Ldb.prototype.forEach( callback, [iterator_options] )
  • Ldb.prototype.asyncPut() return Promise object
  • Ldb.prototype.asyncDel() return Promise object
  • Ldb.prototype.asyncGet() return Promise object
  • Ldb.prototype.asyncForEach( callback, [iterator_options] )
  • Ldb.prototype.getIterator([iterator_options]) return LdbIterator
  • Ldb.prototype.addEventListener( type, callback )
  • Ldb.prototype.addEventListenerOnce( type, callback )
  • Ldb.prototype.removeEventListener( type, callback )

• Ldb.open(location, options) return Ldb instance

• Ldb.destroy(location)
• Ldb.repair(location)

new Ldb(options)

!! 如果参数中含有 location , 那么 ldb 实例即为打开状态

const Ldb = require('l-db');
let options = {
  // base settings
  "location" : './test.db',
  "writeSync" : false,
  "readFillCache" : true,
  
  // Levedb default settings
  "createIfMissing" : true,
  "errorIfExists" : false,
  "compression" : true,
  "writeBufferSize" : 4194304,
  "blockSize" : 4096,
  "maxOpenFiles" : 1000,
  "blockRestartInterval" :16,
  "maxFileSize" : 2097152,
  "block_cache" : 8388608,
  "filterPolicy" : 10,
  
  // EventListener
  "onReady" : ()=>{},
  "onCreate" : ()=>{},
  "onChanged" : ()=> {},
  "onError" : ()=>{},
  "onClosed" : ()=>{}
};
let ldb = new Ldb(options);

想了解设置项的含义，请参考 Leveldb 文档

Ldb.prototype.open(location, options)

具体的参数设置同上

ldb.open('./test.db', {});

Ldb.prototype.close()

ldb.close();

Ldb.prototype.put( key, value ) or Ldb.prototype.put( json )

ldb.put("abc", 123);
ldb.put({
  "abc": null, // delete abc
  "def": 456,
  "ghi": [7, 8, 9]
});

Ldb.prototype.del( key ) or Ldb.prototype.del( keys )

ldb.del("abc");
ldb.del(["abc", "def"]);

Ldb.prototype.get( key ) or Ldb.prototype.get( keys )

let value = ldb.get("abc");
let value_json = ldb.get(["abc", "def", "ghi"]);

Ldb.prototype.forEach( callback, iterator_options )

ldb.forEach((iter)=>{
    console.log(iter.key, iter.value);
});

通过设置 iterator_options 可筛选返回结果

ldb.put({"a1": 1, "a2": 2, "b1": 3, "b2": 4, "c1": 5, "c2" : 6, "d.1": 7, "d.2": 8});

let callback = (iter) => {console.log(iter.key, ":", iter.value);}

ldb.forEach(callback, {start: "b"});
// print: b1:3, b2:4, c1:5, c2:6, d.1:7, d.2:8

ldb.forEach(callback, {start: "b", end:"c"});
// print: b1:3, b2:4

ldb.forEach(callback, {prefix: "d."});
// print: d.1:7, d.2:8

Ldb.prototype.asyncPut()

异步调用 put 方法

ldb.asyncPut("abc", 123).then(()=>{
    ...
}).catch((error)=>{
  	console.log(error);  
});

(async ()=>{
  await ldb.asyncPut("abc", 1234);
})()

Ldb.prototype.asyncDel()

ldb.asyncDel("abc", 123).then(()=>{
    ...
});

(async ()=>{
  await ldb.asyncPut("abc", 1234);
})()

Ldb.prototype.asyncGet()

ldb.asyncGet("abc", 123).then((value)=>{
    console.log(value)
});

(async ()=>{
  let value = await ldb.asyncGet("abc");
})()

Ldb.prototype.asyncForEach( callback, iterator_options )

ldb.forEach((iter)=>{
    console.log(iter.key, iter.value);
});

Ldb.prototype.getIterator(iterator_options)

let iter = ldb.getIterator({start: "b"});
while(iter.isValid){
    console.log(iter.key, iter.value);
  	iter.next();
}

Ldb.prototype.addEventListener( type, callback )

• ready 数据库打开后，会触发事件
• create 当数据库不存在被创建后，会触发事件
• changed 当执行 put 或 del 操作后，会触发事件
• error 当有错误产生后，会触发事件
• closed 当数据库关闭后，会触发事件

ldb.addEventListener("changed", (info)=>{
  	console.log( info.from, info.key );
  	// print: put "abc"
});

ldb.put("abc", 123);

Ldb.prototype.addEventListenerOnce( type, callback )

ldb.addEventListenerOnce("ready", (info)=>{
  	console.log("ok")
});

Ldb.prototype.removeEventListener( type, callback )

ldb.removeEventListener("ready", func);

Ldb.open(location, options)

let ldb = Ldb.open("./test.db")

Ldb.destroy(location)

Ldb.destroy("./test.db")

Ldb.repair(location)

Ldb.repair("./test.db")