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# minipass
A _very_ minimal implementation of a [PassThrough
stream](https://nodejs.org/api/stream.html#stream_class_stream_passthrough)
[It's very
fast](https://docs.google.com/spreadsheets/d/1oObKSrVwLX_7Ut4Z6g3fZW-AX1j1-k6w-cDsrkaSbHM/edit#gid=0)
for objects, strings, and buffers.
Supports pipe()ing (including multi-pipe() and backpressure
transmission), buffering data until either a `data` event handler or
`pipe()` is added (so you don't lose the first chunk), and most other
cases where PassThrough is a good idea.
There is a `read()` method, but it's much more efficient to consume
data from this stream via `'data'` events or by calling `pipe()` into
some other stream. Calling `read()` requires the buffer to be
flattened in some cases, which requires copying memory.
There is also no `unpipe()` method. Once you start piping, there is
no stopping it!
If you set `objectMode: true` in the options, then whatever is written
will be emitted. Otherwise, it'll do a minimal amount of Buffer
copying to ensure proper Streams semantics when `read(n)` is called.
This is not a `through` or `through2` stream. It doesn't transform
the data, it just passes it right through. If you want to transform
the data, extend the class, and override the `write()` method. Once
you're done transforming the data however you want, call
`super.write()` with the transform output.
For an example of a stream that extends MiniPass to provide transform
capabilities, check out [minizlib](http://npm.im/minizlib).
## USAGE
```js
const MiniPass = require('minipass')
const mp = new MiniPass(options) // optional: { encoding }
mp.write('foo')
mp.pipe(someOtherStream)
mp.end('bar')
```
### collecting
```js
mp.collect().then(all => {
// all is an array of all the data emitted
// encoding is supported in this case, so
// so the result will be a collection of strings if
// an encoding is specified, or buffers/objects if not.
//
// In an async function, you may do
// const data = await stream.collect()
})
```
### iteration
You can iterate over streams synchronously or asynchronously in
platforms that support it.
Synchronous iteration will end when the currently available data is
consumed, even if the `end` event has not been reached. In string and
buffer mode, the data is concatenated, so unless multiple writes are
occurring in the same tick as the `read()`, sync iteration loops will
generally only have a single iteration.
To consume chunks in this way exactly as they have been written, with
no flattening, create the stream with the `{ objectMode: true }`
option.
```js
const mp = new Minipass({ objectMode: true })
mp.write('a')
mp.write('b')
for (let letter of mp) {
console.log(letter) // a, b
}
mp.write('c')
mp.write('d')
for (let letter of mp) {
console.log(letter) // c, d
}
mp.write('e')
mp.end()
for (let letter of mp) {
console.log(letter) // e
}
for (let letter of mp) {
console.log(letter) // nothing
}
```
Asynchronous iteration will continue until the end event is reached,
consuming all of the data.
```js
const mp = new Minipass({ encoding: 'utf8' })
// some source of some data
let i = 5
const inter = setInterval(() => {
if (i --> 0)
mp.write(Buffer.from('foo\n', 'utf8'))
else {
mp.end()
clearInterval(inter)
}
}, 100)
// consume the data with asynchronous iteration
async function consume () {
for await (let chunk of mp) {
console.log(chunk)
}
return 'ok'
}
consume().then(res => console.log(res))
// logs `foo\n` 5 times, and then `ok`
```