Node.js处理I/O数据之使用Buffer模块缓冲数据

var jsonStr='{"name":"cuiyanwei","sex":"男","blog":"Http://www.cnblogs.com/5ishare/"}';
//json转js对象
var jsObj=JSON.parse(jsonStr);
console.log(jsObj);
//js对象转Json
var newJsonStr=JSON.stringify(jsObj);
console.log(newJsonStr);

//    1.字节大小 2.八位字节缓冲区 3.UTF8字符串
var  buffer256=new  Buffer(256);
var  bufferOctets=new Buffer([0x6f,0x63,0x74,0x65,0x74,0x73]);
var bufferUTF8=new  Buffer("Some UTF8 Text",'utf8');

var buf256=new Buffer(25);
//fill(value,[offset],[end]) 将value写到缓冲区从offset索引(默认0)处开始,并在end索引处结束的每个字节(默认buffer长度)
buf256.fill("1",0);
console.log(buf256.toString());
//wirte(string,[offset],[length],[encoding]) 使用encoding编码从缓冲区offset索引开始写入string中length数量的字节
buf256.write("abc",1,2,'utf8');
console.log(buf256.toString());
buf256[6]=56;//将索引处的数据替换为指定的value值
console.log(buf256.toString());

var bufUTF8=new  Buffer("Some UTF8 Text",'utf8');
console.log(bufUTF8.toString());
//toString([encoding],[start],[end]) 使用encoding编码,读取从start(0)到end(尾)
console.log(bufUTF8.toString('utf8',0,4));
//返回缓冲区在指定offset字节的八进制值
console.log(bufUTF8[8].toString(16));
//Node.js提供StringDecoder对象,有一个write(buffer)来进行解码,并使用指定的编码写入缓冲区数据
var StringDecoder=require('string_decoder').StringDecoder;
var decoder=new StringDecoder('utf8');
console.log(decoder.write(bufUTF8));

var s='UTF8 text \u00b6';
console.log(s.length);
console.log(Buffer.byteLength(s,'utf8'));
console.log(Buffer(s).length)

var bufSource=new  Buffer("1234567890",'utf8');
var bufTarget=new  Buffer("abcedfghijklmn",'utf8');
//copy.(targetBuffer, targetStart, sourceStart, sourceEnd)
//bufSource.copy(bufTarget,10,3,9); //abcedfghij4567
bufSource.copy(bufTarget,0,3,9);//456789ghijklmn
console.log(bufTarget.toString());

var  number=new Buffer('123456789');
console.log(number.toString());
var slice=number.slice(3.9);
console.log(slice.toString());
slice[0]='#'.charCodeAt(0);
slice[slice.length-1]='#'.charCodeAt(0);
console.log(slice.toString());
console.log(number.toString());

var buff1 = new Buffer("123");
var buff2 = new Buffer("abc");
console.log(Buffer.concat([buff1, buff2,buff1]).toString());