In Addition to that, whenthe counter can emit something
counter._transform = function(chunk, encoding, callback){
count += (chunk && chunk.length) || 0
this.push(chunk)
if(count >= threshhold) this.emit('threshhold_reached')
callback()
}
Am Dienstag, 11. Februar 2014 12:36:20 UTC+1 schrieb greelgorke:
>
> you can count bytes with by putting a passthrough stream in between
>
> var counter = new stream.Transform
> var count = 0
> counter._transform = function(chunk, encoding, callback){
> count += (chunk && chunk.length) || 0
> this.push(chunk)
> callback()
> }
>
>
> slowSourceStream.pipe(counter).pipe(destinationStream)
>
>
>
> Am Samstag, 8. Februar 2014 01:12:37 UTC+1 schrieb Denys Khanzhiyev:
>>
>> Hello,
>>
>> I have a task where one slow stream is piped to fs.writeStream and after
>> some event I need to read from that writen file, i.e. read from growing
>> file from some position. A have seen `node-growing-file`, and
>> `tailing-stream` nothing seems to solve my problem.
>>
>> It looks like I do not understand how streams work
>> Here is my helper object (though it is called PxyStream it is not stream
>> in fact),
>>
>> var
>> fs = require('fs');
>>
>> function PxyStream(path,readStream,writeStream,start,end){
>> this.path = path;
>> this.readStream = readStream;
>> this.writeStream = writeStream;
>> this._offset = start;
>> this.endPos = end;
>> this.writeStream.on('finish',function(){
>> this._writeStreamFinished = true;
>> this.nextStream();
>> }.bind(this))
>> }
>>
>>
>> PxyStream.prototype.pipe = function(destination){
>> this.destination = destination;
>> this.nextStream();
>> }
>>
>> PxyStream.prototype.nextStream = function(){
>> if(!this._stream){
>> var options = {
>> start: this._offset
>> };
>> var last = this._writeStreamFinished;
>> console.log('new read stream',this._offset, last);
>> this._stream = fs.createReadStream(this.path,options);
>> this._stream.pipe(this.destination,{end: false});
>> this._stream.on('data',function(data){
>> this._offset += data.length;
>> }.bind(this));
>>
>> this._stream.on('end',function(){
>> console.log('read stream end',this._offset, last);
>> this._stream.unpipe();
>> this._stream = null;
>> if(last) {
>> this.destination.emit('end');
>> }
>> this._watch();
>> }.bind(this));
>> }
>> }
>>
>> PxyStream.prototype._watch = function(){
>> this.readStream.once('data',function(){
>> this.nextStream();
>> }.bind(this))
>> }
>>
>> exports.PxyStream = PxyStream;
>>
>>
>> I am using it as
>>
>> pxyStream = new PxyStream(filePath,<slowReadStream>,
>> <fsWriteStream>,start,null);
>> // i need end position too but lets skip it for now
>> pxyStream.pipe(<otherSlowStream>);
>>
>> my problem is I see 'read stream end' message far before otherSlowStream
>> ends.
>> In fact it never ends, but i can see its progress.
>> Actually destination is http.response stream.
>> I thought stream.pipe should slow down reading in order to keep buffers
>> short.
>> Maybe attached 'data' event makes it read fast, but how can I count bytes
>> then?
>> The other problem is I can not end destination properly.
>>
>>
>>
>>
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