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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