var Stream = require('stream').Stream; 
var PassThrough = require('readable-stream').PassThrough; 
var util = module.exports = { 
}
; 
util.isStream = function (source){ 
return source instanceof Stream; 
} 
; 
util.normalizeInputSource = function (source){ 
if (source === null ) { 
return Buffer.alloc(0); 
} 
 else if (typeof source === 'string') { 
return Buffer.from(source); 
} 
 else if (util.isStream(source) && !source._readableState) { 
var normalized = new PassThrough(); 
source.pipe(normalized); 
return normalized; 
} 
return source; 
} 
;