I have a transform stream and a writable stream that both need to read from stdin. The transform stream transforms chunks and emits them (as usual). The writable stream collects some information from the stream and has a getInfo() function that can be called to retrieve that information. This is what my current code looks like, with mergeStreams being a hacky mess to make it work:
const myStream = () => {
const transformStream = foo()
const writableStream = bar()
const stream = mergeStreams([transformStream, writableStream], (push, cb) => { // flush function
// add some output to the end of the stream
push('\n' + writableStream.getInfo() + '\n')
cb() // stream is done
})
stream.push('\n') // start with a blank line
return stream
}
process.stdin
.pipe(myStream())
.pipe(process.stdout)
// sample output:
/* // blank line
* output from transformStream
* output from transformStream
* and so on from transformStream
* and finally the result from writableStream.getInfo()
*/and here's a rundown of the stream logic
/* stream is writable/readable
on write, chunks go to transformStream and writableStream
transformStream receives, transforms, and emits values
when the writer is finished writing to the stream
and transformStream is done reading/writing
and writableStream is done reading,
emit result of writableStream.getInfo()
*/I made this work with node streams by proxying the chunks to the other streams and using the flush function and events. It's complex and awkward behind the scenes. I hope that with pull-stream, I can get rid of that hacky mergeStreams function and do this with some pull-stream modules. I can't find a way to return a single stream that writes to both transformStream and writableStream and to inject the results of getInfo() at the end.
Thanks for any advice on this!
I have a transform stream and a writable stream that both need to read from stdin. The transform stream transforms chunks and emits them (as usual). The writable stream collects some information from the stream and has a
getInfo()function that can be called to retrieve that information. This is what my current code looks like, withmergeStreamsbeing a hacky mess to make it work:and here's a rundown of the stream logic
I made this work with node streams by proxying the chunks to the other streams and using the flush function and events. It's complex and awkward behind the scenes. I hope that with pull-stream, I can get rid of that hacky
mergeStreamsfunction and do this with some pull-stream modules. I can't find a way to return a single stream that writes to bothtransformStreamandwritableStreamand to inject the results ofgetInfo()at the end.Thanks for any advice on this!