How to download and unzip a zip file in memory in NodeJs?

javascript, node.js, unzip, zip, zlib

Solution

You need a library that can handle buffers. The latest version of `adm-zip` will do:

npm install adm-zip

My solution uses the `http.get` method, since it returns Buffer chunks.

Code:

var file_url = 'http://notepad-plus-plus.org/repository/7.x/7.6/npp.7.6.bin.x64.zip';

var AdmZip = require('adm-zip');
var http = require('http');

http.get(file_url, function(res) {
  var data = [], dataLen = 0; 

  res.on('data', function(chunk) {
    data.push(chunk);
    dataLen += chunk.length;

  }).on('end', function() {
    var buf = Buffer.alloc(dataLen);

    for (var i = 0, len = data.length, pos = 0; i < len; i++) { 
      data[i].copy(buf, pos); 
      pos += data[i].length; 
    } 

    var zip = new AdmZip(buf);
    var zipEntries = zip.getEntries();
    console.log(zipEntries.length)

    for (var i = 0; i < zipEntries.length; i++) {
      if (zipEntries[i].entryName.match(/readme/))
        console.log(zip.readAsText(zipEntries[i]));
    }
  });
});

The idea is to create an array of buffers and concatenate them into a new one at the end. This is due to the fact that buffers cannot be resized.

Update

This is a simpler solution that uses the `request` module to obtain the response in a buffer, by setting `encoding: null` in the options. It also follows redirects and resolves http/https automatically.

var file_url = 'https://github.com/mihaifm/linq/releases/download/3.1.1/linq.js-3.1.1.zip';

var AdmZip = require('adm-zip');
var request = require('request');

request.get({url: file_url, encoding: null}, (err, res, body) => {
  var zip = new AdmZip(body);
  var zipEntries = zip.getEntries();
  console.log(zipEntries.length);

  zipEntries.forEach((entry) => {
    if (entry.entryName.match(/readme/i))
      console.log(zip.readAsText(entry));
  });
});

The `body` of the response is a buffer that can be passed directly to `AdmZip`, simplifying the whole process.

Problem

I want to download a zip file from the internet and unzip it in memory without saving to a temporary file. How can I do this? Here is what I tried: ``` var url = 'http://bdn-ak.bloomberg.com/precanned/Comdty_Calendar_Spread_Option_20120428.txt.zip'; var request = require('request'), fs = require('fs'), zlib = require('zlib'); request.get(url, function(err, res, file) { if(err) throw err; zlib.unzip(file, function(err, txt) { if(err) throw err; console.log(txt.toString()); //outputs nothing }); }); ``` [EDIT] As, suggested, I tried using the adm-zip library and I still cannot make this work: ``` var ZipEntry = require('adm-zip/zipEntry'); request.get(url, function(err, res, zipFile) { if(err) throw err; var zip = new ZipEntry(); zip.setCompressedData(new Buffer(zipFile.toString('utf-8'))); var text = zip.getData(); console.log(text.toString()); // fails }); ```

Original source

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