//常见一个规定长度,默认用0填充
console.log(Buffer.alloc(10));
console.log(Buffer.alloc(20));
// 用2填充
console.log(Buffer.alloc(5,2));
// 创建一个长度为 5、且未初始化的 Buffer。这个方法比调用 Buffer.alloc() 更快，
// 但返回的 Buffer 实例可能包含旧数据，因此需要使用 fill() 或 write() 重写。
console.log(Buffer.allocUnsafe(5,2));
console.log(Buffer.from([1,2,3]));
console.log(Buffer.from(‘test‘));
//指定编码
console.log(Buffer.from(‘test‘,‘base64‘));

// 实际占了几个字节
console.log(Buffer.byteLength(‘test‘));
//一个中文三个字节
console.log(Buffer.byteLength(‘测试‘));

console.log(Buffer.isBuffer({}));
console.log(Buffer.isBuffer(Buffer.from([1,2,3])));

const buf1 = Buffer.from(‘This‘)
const buf2 = Buffer.from(‘ is ‘)
const buf3 = Buffer.from(‘a ‘)
const buf4 = Buffer.from(‘test ‘)
const buf5 = Buffer.from(‘!‘)

const buf = Buffer.concat([buf1,buf2,buf3,buf4,buf5])
console.log(buf.toString());

//1.buf.length     
const buf = Buffer.from(‘This is a test!‘)
console.log(buf.length); //15
const buf2 = Buffer.alloc(10);
const buf3 = Buffer.allocUnsafe(10); //默认不填充
buf2[0]=2
//下面证明,就算默认不填充,可是长度是根据你一开始创建的大小来控制,与填不填充内容无关
console.log(buf2.length); //10
console.log(buf3.length); //10


//2.buf.toString() 
console.log(buf.toString()); //默认utf-8 This is a test
console.log(buf.toString(‘base64‘)); //VGhpcyBpcyBhIHRlc3Qh

//3.buf.fill() alloc是自动填充0,但是可以用fill()来填充其他的值
const buf4 = Buffer.allocUnsafe(10)
console.log(buf4);
console.log(buf4.fill(10,2,6));//fill(像填充的内容,从哪里开始,从哪里结束) 


//4.buf.equals()  两个Buffer的内容是否相等
const buf5  = Buffer.from(‘test‘)
const buf6  = Buffer.from(‘test‘)
const buf7  = Buffer.from(‘test!‘)

console.log(buf5.equals(buf6)); //true
console.log(buf5.equals(buf7)); //false

//5.buf.indexOf() buf5=test
console.log(buf5.indexOf(‘s‘)); //找到就返回所在位置的index(从0开始)
console.log(buf5.indexOf(‘a‘));//找不到就返回-1

//6.buf.copy()
const buf8 = Buffer.allocUnsafe(10).fill(‘*‘)
const buf9 = Buffer.allocUnsafe(10).fill(‘!‘)
//拷贝‘buf8‘中第 3-6字节数据到‘buf9‘第4个偏移量开始
buf8.copy(buf9,4,3,6)
console.log(buf9.toString()); // !!!!***!!!