Leveldb-addon

Leveldb addon for Node.js, supports synchronous and asynchronous invocation, and supports event emitter

$3

* Support synchronization method call Leveldb, code logic more clear
* Also supports asynchronous method call Leveldb to make running more efficient
* Asynchronous calls use Promise to make the code clearer

INSTALLATION

``shell
npm install leveldb-addon --save
`

API

* [new Leveldb([options])](#new-ldb-options)

#### Properties
[Leveldb.prototype.location]() Reflects the string of the database path*

[Leveldb.prototype.isOpen]() Reflects the boolearn of the database is available*

[Leveldb.prototype.stateCode]() Reflects the number of the databease status , whenever a database change changes*

#### Methods

* [Leveldb.prototype.open(location, [options])](#Leveldb-prototype-open-location-options)
* Leveldb.prototype.close()
Leveldb.prototype.put( key, value ) or Ldb.prototype.put( json ) return Boolean when execution succeeds return true*
Ldb.prototype.del( key ) or Ldb.prototype.del( keys ) return Boolean when execution succeeds return true*
Ldb.prototype.get( key ) or Ldb.prototype.get( keys ) return [values]*
* [Ldb.prototype.forEach( callback, [iteratorOptions] )](#Leveldb-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, [iteratorOptions] )](#Leveldb-prototype-asyncForEach-callback-iterator_options)
[Ldb.prototype.getIterator([iteratorOptions])](#Leveldb-prototype-getIterator-iterator_options) return Leveldb.Iterator*
* Ldb.prototype.addListener( type, callback, once )
* Ldb.prototype.removeListener( type, callback )
* [Ldb.prototype.match(prefix, offset) ]()

Ldb.open(location, options) return Leveldb instance*
* Ldb.destroy(location)
* Ldb.repair(location)
* [Ldb.isExist(location)]()
* IteratorOptions

* start
* end
* prefix
* reverse
* snapshot: default true
* Leveldb.Iterator
Iterator.read() If the iterator is valid to return itself, the invalid returns undefined*
* Iterator.key
* Iterator.value
* Iterator.isEnd
iterator.break() release iterator*

$3

`javascript
const Leveldb = require('leveldb-addon');
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 Leveldb(options);
`

For information about setting items, see the Leveldb documentation

$3

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

$3

`javascript
ldb.close();
`

$3

`javascript
if (ldb.put("abc", 123)) {
console.log('ok');
}
ldb.put({
"abc": null, // delete abc
"def": 456,
"ghi": [7, 8, 9]
});
`

$3

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

$3

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

$3

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

ldb.forEach((iter)=>{
if(!/b/.test(iter.key)){
iter.break();
}else{
console.log(iter.key, iter.value);
}
});

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, {start: "c", end:"b", reverse:true});
// print: c1:5, c2:6

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

`

$3

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

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

$3

`javascript
ldb.asyncDel("abc").then(()=>{
...
});
`

`javascript
(async ()=>{
await ldb.asyncDel("abc")
})()
`

$3

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

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

$3

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

$3

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

$3

* type :
* ready Trigger event after database open
* create Triggers an event when the database is created
* changed Triggers an event when the put or del operation is executed
* error Triggers an event when an error occurs
* closed Trigger event after database shutdown

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

ldb.put("abc", 123);
`

$3

`javascript
ldb.removeEventListener("ready", func);
`

$3

`javascript
let ldb = Leveldb.open("./test.db")
`

$3

`javascript
Leveldb.destroy("./test.db")
`

$3

`javascript
Leveldb.repair("./test.db")
`

$3

`javascript
let options = {
"start":"a",
"end": "b",
"prefix": "c",
"reverse": true,
"limit":
}
``