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var Stream = require('stream')
// through
//
// a stream that does nothing but re-emit the input.
// useful for aggregating a series of changing but not ending streams into one stream)
exports = module.exports = through
through.through = through
//create a readable writable stream.
function through (write, end, opts) {
write = write || function (data) { this.queue(data) }
end = end || function () { this.queue(null) }
var ended = false, destroyed = false, buffer = [], _ended = false
var stream = new Stream()
stream.readable = stream.writable = true
stream.paused = false
// stream.autoPause = !(opts && opts.autoPause === false)
stream.autoDestroy = !(opts && opts.autoDestroy === false)
stream.write = function (data) {
write.call(this, data)
return !stream.paused
}
function drain() {
while(buffer.length && !stream.paused) {
var data = buffer.shift()
if(null === data)
return stream.emit('end')
else
stream.emit('data', data)
}
}
stream.queue = stream.push = function (data) {
// console.error(ended)
if(_ended) return stream
if(data === null) _ended = true
buffer.push(data)
drain()
return stream
}
//this will be registered as the first 'end' listener
//must call destroy next tick, to make sure we're after any
//stream piped from here.
//this is only a problem if end is not emitted synchronously.
//a nicer way to do this is to make sure this is the last listener for 'end'
stream.on('end', function () {
stream.readable = false
if(!stream.writable && stream.autoDestroy)
process.nextTick(function () {
stream.destroy()
})
})
function _end () {
stream.writable = false
end.call(stream)
if(!stream.readable && stream.autoDestroy)
stream.destroy()
}
stream.end = function (data) {
if(ended) return
ended = true
if(arguments.length) stream.write(data)
_end() // will emit or queue
return stream
}
stream.destroy = function () {
if(destroyed) return
destroyed = true
ended = true
buffer.length = 0
stream.writable = stream.readable = false
stream.emit('close')
return stream
}
stream.pause = function () {
if(stream.paused) return
stream.paused = true
return stream
}
stream.resume = function () {
if(stream.paused) {
stream.paused = false
stream.emit('resume')
}
drain()
//may have become paused again,
//as drain emits 'data'.
if(!stream.paused)
stream.emit('drain')
return stream
}
return stream
}
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