四好公路
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var util = require('util')
var Transform = require('stream').Transform
util.inherits(Counter, Transform)
module.exports = Counter
function Counter(options) {
if (!(this instanceof Counter))
return new Counter(options)
Transform.call(this, options)
this.length = 0
}
Counter.prototype._transform = function (chunk, encoding, callback) {
this.length += chunk.length
this.push(chunk)
callback()
}