Using buffers

Here is some information on creating gulp plugin that manipulates buffers.

Writing a Plugin > Using buffers

Using buffers

If your plugin is relying on a buffer based library, you will probably choose to base your plugin around file.contents as a buffer. Let's implement a plugin prepending some text to files:

var through = require('through2');
var gutil = require('gulp-util');
var PluginError = gutil.PluginError;

// consts
const PLUGIN_NAME = 'gulp-prefixer';

// plugin level function (dealing with files)
function gulpPrefixer(prefixText) {
  if (!prefixText) {
    throw new PluginError(PLUGIN_NAME, 'Missing prefix text!');

  prefixText = new Buffer(prefixText); // allocate ahead of time

  // creating a stream through which each file will pass
  var stream = through.obj(function(file, enc, cb) {
    if (file.isStream()) {
      this.emit('error', new PluginError(PLUGIN_NAME, 'Streams are not supported!'));
      return cb();

    if (file.isBuffer()) {
      file.contents = Buffer.concat([prefixText, file.contents]);

    // make sure the file goes through the next gulp plugin

    // tell the stream engine that we are done with this file

  // returning the file stream
  return stream;

// exporting the plugin main function
module.exports = gulpPrefixer;

The above plugin can be used like this:

var gulp = require('gulp');
var gulpPrefixer = require('gulp-prefixer');

  .pipe(gulpPrefixer('prepended string'))

Handling streams

Unfortunately, the above plugin will error when using gulp.src in non-buffered (streaming) mode. You should support streams too if possible. See Dealing with streams for more information.

Some plugins based on buffers

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