How to compress a buffer with yazl?

Question

How can I compress/decompress a buffer via yazl? https://www.npmjs.com/package/yazl

I don't want to create/save a zip file but just compress a buffer and forward it to another service. Any sample code would be helpful

var yazl = require("yazl");

var buf = fs.readFileSync(__dirname + '/testArchive.txt');
var zipfile = new yazl.ZipFile();
zipfile.addBuffer(buf, "TEMPENTRY");
zipfile.end();

So has it been archived at this point? How to I inflate that buffer by using yauzl then?

Answer 1

This kind of function should help, manually retrieving the stream's packets, then concatenating them into one single Buffer :

function stream2buffer(readableStream) {
  return new Promise((resolve, reject) => {
    const chunks = [];
    readableStream.on('data', (chunk) => {
      chunks.push(chunk);
    }).on('end', () => {
      resolve(Buffer.concat(chunks));
    }).on('error', (err) => {
      reject(err);
    });
  });
}

Then you can use it on yazl.ZipFile.outputStream , and on the other side on the readable stream provided by yauzl.ZipFile.openReadStream 's callback.

Edit

What I meant is more like using this function on yazl 's outputStream , not on the source files you want to compress. More like this:

function zipper(mapping) { // mapping is expected to be a Map here
  const handler = new yazl.ZipFile(); // yazl = require('yazl');
  for (mapItem of mapping) {
    if (typeof mapItem[1] === 'string' || mapItem[1] instanceof String) {
      handler.addFile(mapItem[1], mapItem[0]);
    } else if (mapItem[1] instanceof Buffer) {
      handler.addBuffer(mapItem[1], mapItem[0]);
    } else if (mapItem[1] instanceof stream.Readable) { // stream = require('stream');
      handler.addReadStream(mapItem[1], mapItem[0]);
    } else throw new Error('unsupported type');
  }
  handler.end();
  return stream2buffer(handler.outputStream);
}

And it's alike for the unzipping:

function unzipper(buffer) {
  return new Promise((resolve, reject) => {
    unzippedContents = {};
    yauzl.fromBuffer(buffer, {lazyEntries: true}, (err, zip) => { // yauzl = require('yauzl')
      if (err) return reject(err);
      zip.on('entry', (entry) => {
        if (/\/$/.test(entry.fileName)) return zip.readEntry(); // no directories
        zip.openReadStream(entry, async (err, rs) => {
          try {
            if (err) throw err;
            unzippedContents[entry.fileName] = await stream2buffer(rs);
          } catch (err) {
            zip.close();
            return reject(err);
          }
          zip.readEntry();
        });
      }).on('end', () => {
        zip.close();
        resolve(unzippedContents);
      });
      zip.readEntry(); // start the process
    });
  });
}