//异步形式读取文件

function copyFile(url){

    const extName = path.extname(url)

    const fileName = path.basename(url)

    const dirName = path.dirname(url)

    fs.readFile(url, (err, data) => {

        fs.writeFile(`${dirName}/${fileName}_copy_1${extName}`, data , err => {

            if(err){

                console.log(`写入出现错误 ${err.toString()}`)

            }else{

                console.log('完成!')

            }

        })

    })

}

//同步形式读取文件

function copySync(url){

    const extName = path.extname(url)

    const fileName = path.basename(url)

    const dirName = path.dirname(url)

    var data = fs.readFileSync(url)

    fs.writeFileSync(`${dirName}/${fileName}_copy_1${extName}`,data)

    console.log('同步拷贝完成!')

}

const fs = require('fs')

const path = require('path')

// 使用流拷贝

function streamCopyFile(url){

    const extName = path.extname(url)

    const fileName = path.basename(url)

    const dirName = path.dirname(url)

    let options = {

        highWaterMark : 64 * 1024 //默认值，每个chunk的大小

    }

    const readable = fs.createReadStream(url, options)

    const writable = fs.createWriteStream(`${dirName}/${fileName}_copy${extName}`)

    var size = 0

    var totalSize = 0

    const stat = fs.stat(url, (err , stats) => {

        totalSize = stats.size

    })

    readable.on('open', () => {

        console.log('打开文件');

    })

    readable.on('data', data => {

        size = data.length + size

        console.log('已完成 ' + parseInt((size / totalSize) * 100) + '%');

        writable.write(data)

        readable.pause()

    })

    readable.on('end', () => {

        console.log('读取完成')

    })

    readable.on('error', err => {

        console.log(`读取时出现错误 ${err.toString()}`)

    })

    writable.on('error', err => {

        console.log(`写入时出现错误 ${err.toString()}`)

    })

    //将内存中数据全部写入文件后触发 drain 事件

    writable.on('drain', () => {

        readable.resume()

    })

    writable.on('finish', () => {

        console.error('写入完成');

    })

}

//通过管道的方式

function pipeCopyFile(url){

    const extName = path.extname(url)

    const fileName = path.basename(url)

    const dirName = path.dirname(url)

    const readable = fs.createReadStream(url)

    const writable = fs.createWriteStream(`${dirName}/${fileName}_copy_2${extName}`)

    var size = 0

    var totalSize = 0

    const stat = fs.stat(url, (err , stats) => {

        totalSize = stats.size

    })

    writable.on('pipe', (src) => {

        console.log('有数据正通过管道流入写入器')

    })

    writable.on('finish', () => {

        console.error('写入已完成')

    })

    readable.pipe(writable)

}