CODEWITHSUNDEEP
javascriptnode.js
user746157
user746157

Reputation:

How to read binary file byte by byte using javascript?

I need to read the binary file byte by byte using javascript.I had got below code in this site,but its not working.I think i have to add some extra src file as a reference to it.Please help me to do it.here the code...

var fs = require('fs');
var Buffer = require('buffer').Buffer;
var constants = require('constants');

fs.open("file.txt", 'r', function(status, fd) {
    if (status) {
        console.log(status.message);
        return;
    }
    var buffer = new Buffer(100);
    fs.read(fd, buffer, 0, 100, 0, function(err, num) {
        console.log(buffer.toString('utf-8', 0, num));
    });
});

Upvotes: 8

Views: 26053

Answers (3)

bmaupin
bmaupin

Reputation: 16005

import { readFile } from 'fs/promises';

// read the file into a buffer (https://nodejs.org/api/fs.html#fspromisesreadfilepath-options)
(await readFile('file.txt'))
  // (optional) read just a portion of the file
  .slice(startingByte, endingByte)
  // process each byte however you like
  .forEach((byte) => console.log(byte));

Upvotes: 0

robertklep
robertklep

Reputation: 203534

You can read the file synchronously, byte by byte:

fs.open('file.txt', 'r', function(err, fd) {
  if (err)
    throw err;
  var buffer = Buffer.alloc(1);
  while (true)
  {   
    var num = fs.readSync(fd, buffer, 0, 1, null);
    if (num === 0)
      break;
    console.log('byte read', buffer[0]);
  }
});

Upvotes: 9

Cigodien
Cigodien

Reputation: 78

You can use the following code:

var blob = file.slice(startingByte, endindByte);
reader.readAsBinaryString(blob);

Here's how it works:

  • file.slice will slice a file into bytes and save to a variable as binary. You can slice by giving the start byte and end byte.

  • reader.readAsBinaryString will print that byte as binary file. It doesn't matter how big the file is.

For more info, see this link.

Upvotes: 2

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