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70 lines
2.2 KiB
Markdown
70 lines
2.2 KiB
Markdown
8 months ago
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# minipass-pipeline
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Create a pipeline of streams using Minipass.
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Calls `.pipe()` on all the streams in the list. Returns a stream where
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writes got to the first pipe in the chain, and reads are from the last.
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Errors are proxied along the chain and emitted on the Pipeline stream.
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## USAGE
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```js
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const Pipeline = require('minipass-pipeline')
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// the list of streams to pipeline together,
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// a bit like `input | transform | output` in bash
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const p = new Pipeline(input, transform, output)
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p.write('foo') // writes to input
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p.on('data', chunk => doSomething()) // reads from output stream
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// less contrived example (but still pretty contrived)...
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const decode = new bunzipDecoder()
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const unpack = tar.extract({ cwd: 'target-dir' })
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const tbz = new Pipeline(decode, unpack)
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fs.createReadStream('archive.tbz').pipe(tbz)
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// specify any minipass options if you like, as the first argument
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// it'll only try to pipeline event emitters with a .pipe() method
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const p = new Pipeline({ objectMode: true }, input, transform, output)
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// If you don't know the things to pipe in right away, that's fine.
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// use p.push(stream) to add to the end, or p.unshift(stream) to the front
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const databaseDecoderStreamDoohickey = (connectionInfo) => {
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const p = new Pipeline()
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logIntoDatabase(connectionInfo).then(connection => {
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initializeDecoderRing(connectionInfo).then(decoderRing => {
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p.push(connection, decoderRing)
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getUpstreamSource(upstream => {
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p.unshift(upstream)
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})
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})
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})
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// return to caller right away
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// emitted data will be upstream -> connection -> decoderRing pipeline
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return p
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}
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```
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Pipeline is a [minipass](http://npm.im/minipass) stream, so it's as
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synchronous as the streams it wraps. It will buffer data until there is a
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reader, but no longer, so make sure to attach your listeners before you
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pipe it somewhere else.
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## `new Pipeline(opts = {}, ...streams)`
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Create a new Pipeline with the specified Minipass options and any streams
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provided.
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## `pipeline.push(stream, ...)`
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Attach one or more streams to the pipeline at the end (read) side of the
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pipe chain.
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## `pipeline.unshift(stream, ...)`
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Attach one or more streams to the pipeline at the start (write) side of the
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pipe chain.
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