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first-chunk-stream

4.0.0 • Public • Published

first-chunk-stream Build Status

Buffer and transform the n first bytes of a stream

Install

$ npm install first-chunk-stream

Usage

const fs = require('fs');
const getStream = require('get-stream');
const FirstChunkStream = require('first-chunk-stream');
 
// unicorn.txt => unicorn rainbow
const stream = fs.createReadStream('unicorn.txt')
    .pipe(new FirstChunkStream({chunkSize: 7}, async (chunk, encoding) => {
        return chunk.toString(encoding).toUpperCase();
    }));
 
(async () => {
    const data = await getStream(stream);
 
    if (data.length < 7) {
        throw new Error('Couldn\'t get the minimum required first chunk length');
    }
 
    console.log(data);
    //=> 'UNICORN rainbow'
})();

API

FirstChunkStream(options, transform)

FirstChunkStream constructor.

transform(chunk, encoding)

Type: Function

Async function that receives the required options.chunkSize bytes.

Expected to return an buffer-like object or string or object of form {buffer: Buffer, encoding: string} to send to stream or firstChunkStream.stop to end stream right away.

An error thrown from this function will be emitted as stream errors.

Note that the buffer can have a smaller length than the required one. In that case, it will be due to the fact that the complete stream contents has a length less than the options.chunkSize value. You should check for this yourself if you strictly depend on the length.

new FirstChunkStream({chunkSize: 7}, async (chunk, encoding) => {
    return chunk.toString(encoding).toUpperCase(); // Send string to stream
});
 
new FirstChunkStream({chunkSize: 7}, async (chunk, encoding) => {
    return chunk; // Send buffer to stream
});
 
new FirstChunkStream({chunkSize: 7}, async (chunk, encoding) => {
    return {
        buffer: chunk,
        encoding: encoding,
    }; // Send buffer with encoding to stream
});
 
new FirstChunkStream({chunkSize: 7}, async (chunk, encoding) => {
    return FirstChunkStream.stop; // End the stream early
});
 
new FirstChunkStream({chunkSize: 7}, async (chunk, encoding) => {
    throw new Error('Unconditional error'); // Emit stream error
});

options

Type: object

The options object is passed to the Duplex stream constructor allowing you to customize your stream behavior. In addition, you can specify the following option:

chunkSize

Type: number

How many bytes you want to buffer.

Install

npm i first-chunk-stream

DownloadsWeekly Downloads

1,384,325

Version

4.0.0

License

MIT

Unpacked Size

10.5 kB

Total Files

5

Last publish

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