十三.compress

1.压缩与解压缩处理

可以使用zlib模块进行压缩与解压缩处理，压缩文件以后可以减少体积，加快传输速度和节约宽带

2.压缩对象

压缩和解压缩对象都是一个可读可写流

方法	说明
zlib.createGzip	返回 Gzip 流对象，使用 Gzip 算法对数据进行压缩处理
zlib.createGunzip	返回 Gzip 流对象，使用 Gzip 算法对压缩的数据进行解压缩处理
zlib.createDeflate	返回 Deflate 流对象，使用 Deflate 算法对数据进行压缩处理
zlib.createInflate	返回 Deflate 流对象，使用 Deflate 算法对数据进行解压缩处理

3.压缩与解压缩

var zlib = require("zlib")
var fs = require("fs")

function zip(src) {
  var gzip = zlib.createGzip() //创建压缩流
  var inputStream = fs.createReadStream(src)
  var outputStream = fs.createWriteStream(src + ".gz")
  inputStream.pipe(gzip).pipe(outputStream)
}
zip("source.txt")

function unzip(src) {
  var gunzip = zlib.createGunzip()
  var inputStream = fs.createReadStream(src)
  var outputStream = fs.createWriteStream(src.slice(0, -3))
  inputStream.pipe(gunzip).pipe(outputStream)
}
gnzip("source.txt.gz")

4.在 http 中的应用

var zlib = require("zlib")
var fs = require("fs")
var http = require("http")
http.createServer(function(request, response) {
  var raw = fs.createReadStream("." + request.url)
  var acceptEncoding = request.headers["accept-encoding"]
  if (!acceptEncoding) {
    acceptEncoding = ""
  }
  if (acceptEncoding.match(/\bdeflatte\b/)) {
    response.setHeader("Content-Encoding", "deflate")
    raw.pipe(zlib.createDeflate()).pipe(response)
  } else if (acceptEncoding.match(/\bgzip\b/)) {
    response.setHeader("Content-Encoding", "gzip")
    raw.pipe(zlib.createGzip()).pipe(response)
  } else {
    raw.pipe(response)
  }
}).listen(9090)

var zlib = require('zlib')
var fs = require('fs')
var http = require('http')

var request = http.get({
  host: 'localhost',
  path: '/index.html',
  port: 9090,
  headers: {
    'accept-encoding':'gzip,deflate'
  }
})

request.on('response',function(response){
  var output = fs.createWriteStream('test.txt')
  switch(response.headers['content-encoding']){
    case 'gzip':
      response.pipe(zlib.createGunzip()).pipe(output)
      break;
    case 'deflate':
      response.pipe(zlib.createInflate()).pipe(output)}
      break;
    default:
      response.pipe(output)
      break;
})
request.end()

5.方法调用

var zlib = require("zlib")
var fs = require("fs")

var out = fs.createWriteStream("input.log")
var input = "input"
zlib.gzip(input, function(err, buffer) {
  if (!err) {
    zlib.unzip(buffer, function(err, buffer) {
      if (!err) {
        console.log(buffer.toString())
        out.end(buffer)
      }
    })
  }
})