code: function convertBody(buffer, headers) {
  	if (typeof convert !== 'function') {
  		throw new Error('The package `encoding` must be installed to use the textConverted() function');
  	}
  
  	const ct = headers.get('content-type');
  	let charset = 'utf-8';
  	let res, str;
  
  	// header
  	if (ct) {
  		res = /charset=([^;]*)/i.exec(ct);
  	}
  
  	// no charset in content type, peek at response body for at most 1024 bytes
  	str = buffer.slice(0, 1024).toString();
  
  	// html5
  	if (!res && str) {
  		res = /<meta.+?charset=(['"])(.+?)\1/i.exec(str);
  	}
  
  	// html4
  	if (!res && str) {
  		res = /<meta[\s]+?http-equiv=(['"])content-type\1[\s]+?content=(['"])(.+?)\2/i.exec(str);
  
  		if (res) {
  			res = /charset=(.*)/i.exec(res.pop());
  		}
  	}
  
  	// xml
  	if (!res && str) {
  		res = /<\?xml.+?encoding=(['"])(.+?)\1/i.exec(str);
  	}
  
  	// found charset
  	if (res) {
  		charset = res.pop();
  
  		// prevent decode issues when sites use incorrect encoding
  		// ref: https://hsivonen.fi/encoding-menu/
  		if (charset === 'gb2312' || charset === 'gbk') {
  			charset = 'gb18030';
  		}
  	}
  
  	// turn raw buffers into a single utf-8 buffer
  	return convert(
  		buffer,
  		'UTF-8',
  		charset
  	).toString();
  }
docs: Detect buffer encoding and convert to target encoding
  ref: http://www.w3.org/TR/2011/WD-html5-20110113/parsing.html#determining-the-character-encoding
  
  @param   Buffer  buffer    Incoming buffer
  @param   String  encoding  Target encoding
  @return  String