CODEWITHSUNDEEP
javascriptnode.jscharacter-encodingchunked-encodingnode-streams
Mayank Patel
Mayank Patel

Reputation: 376

How to read data of a NodeJS stream without it being lost?

I need to know the encoding of a node stream for which I am using detect-character-encoding module. But the problem is that I can only read encodings of a buffer and not a stream due to which I have to do something like this:

FileStream.on('data', (chunk) => {
  console.log(chunk)
  const charsetMatch = detectCharacterEncoding(chunk)
  console.log(charsetMatch)
})

Knowing stream encoding comes at the cost of losing a chunk of data, which is required later in the code flow. Is there a way possible in which I can just peek at chunk know its encoding and not lose the chunk and data?

Upvotes: 0

Views: 1497

Answers (1)

darklightcode
darklightcode

Reputation: 2772

You can build a promise to return both the contents and the charset of the stream:

const charsetStream = (stream) => new Promise((resolve, reject) => {

  const detectCharacterEncoding = require('detect-character-encoding');
  let chunks = [];

  stream.on('data', (chunk) => {
    chunks.push(chunk);
  })

  stream.on('end', () => {
    chunks = Buffer.concat(chunks);
    resolve({
      content: chunks,
      charset: detectCharacterEncoding(chunks)
    })
  })

  stream.on('error', (err) => {
    reject(err);
  })

});

charsetStream(FileStream)
  .then(info => {
    console.log('content', info.content);
    console.log('charset', info.charset);
  })
  .catch(console.log);
  
  // You can use the FileStream outside the method but you can use it once !
  // this is completely different than the "stream" variable
  FileStream.on('data', (chunk) => {
    console.log('FileStream', chunk.toString());
  })

Upvotes: 1

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