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[](https://npmjs.org/package/peek-readable)
[](https://npmcharts.com/compare/peek-readable?start=600&interval=30)
[](https://coveralls.io/github/Borewit/peek-readable?branch=master)
[](https://www.codacy.com/app/Borewit/peek-readable?utm_source=github.com&utm_medium=referral&utm_content=Borewit/peek-readable&utm_campaign=Badge_Grade)
[](https://lgtm.com/projects/g/Borewit/peek-readable/alerts/)
[](https://lgtm.com/projects/g/Borewit/peek-readable/context:javascript)
[](https://snyk.io/test/github/Borewit/peek-readable?targetFile=package.json)
# peek-readable
A promise based asynchronous stream reader, which makes reading from a stream easy.
Allows to read and peek from a [Readable Stream](https://nodejs.org/api/stream.html#stream_readable_streams)
Note that [peek-readable](https://github.com/Borewit/peek-readable) was formally released as [then-read-stream](https://github.com/Borewit/peek-readable).
## Usage
### Installation
```shell script
npm install --save peek-readable
```
The `peek-readable` contains one class: `StreamReader`, which reads from a [stream.Readable](https://nodejs.org/api/stream.html#stream_class_stream_readable).
### Compatibility
NPM module is compliant with [ECMAScript 2017 (ES8)](https://en.wikipedia.org/wiki/ECMAScript#8th_Edition_-_ECMAScript_2017).
## Examples
In the following example we read the first 16 bytes from a stream and store them in our buffer.
Source code of examples can be found [here](test/examples.ts).
```js
const fs = require('fs');
const { StreamReader } = require('peek-readable');
(async () => {
const fileReadStream = fs.createReadStream('JPEG_example_JPG_RIP_001.jpg');
const streamReader = new StreamReader(fileReadStream);
const buffer = Buffer.alloc(16);
const bytesRead = await streamReader.read(buffer, 0, 16);
// buffer contains 16 bytes, if the end-of-stream has not been reached
})();
```
End-of-stream detection:
```js
(async () => {
const fileReadStream = fs.createReadStream('JPEG_example_JPG_RIP_001.jpg');
const streamReader = new StreamReader(fileReadStream);
const buffer = Buffer.alloc(16);
try {
await streamReader.read(buffer, 0, 16);
// buffer contains 16 bytes, if the end-of-stream has not been reached
} catch(error) {
if (error instanceof EndOfStreamError) {
console.log('End-of-stream reached');
}
}
})();
```
With peek you can read ahead:
```js
const fs = require('fs');
const { StreamReader } = require('peek-readable');
const fileReadStream = fs.createReadStream('JPEG_example_JPG_RIP_001.jpg');
const streamReader = new StreamReader(fileReadStream);
const buffer = Buffer.alloc(20);
(async () => {
let bytesRead = await streamReader.peek(buffer, 0, 3);
if (bytesRead === 3 && buffer[0] === 0xFF && buffer[1] === 0xD8 && buffer[2] === 0xFF) {
console.log('This is a JPEG file');
} else {
throw Error('Expected a JPEG file');
}
bytesRead = await streamReader.read(buffer, 0, 20); // Read JPEG header
if (bytesRead === 20) {
console.log('Got the JPEG header');
} else {
throw Error('Failed to read JPEG header');
}
})();
```
If you have to skip a part of the data, you can use ignore:
```js
(async () => {
//...
await streamReader.ignore(16);
})();
```
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