Created
August 19, 2020 13:25
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I created a NodeJS Transform Stream which repack data chunks to necessary size chunks
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const { Transform } = require('stream'); | |
const sliceBySize = (buffer, size, callback) => { | |
let chunk = buffer.slice(0, size); | |
let index = size; | |
while (chunk.length >= size) { | |
callback(chunk); | |
chunk = buffer.slice(index, index + size); | |
index += size; | |
} | |
return chunk; | |
}; | |
class ChunkerTransformStream extends Transform { | |
_chunkSize = 512; | |
_chunk = Buffer.alloc(0); | |
constructor(chunkSize) { | |
super(); | |
if (!Number.isNaN(Number(chunkSize))) this._chunkSize = Number(chunkSize); | |
} | |
_transform(oldChunk, encoding, callback) { | |
const freeSpaceLength = this._chunkSize - this._chunk.length; | |
if (oldChunk.length > freeSpaceLength) { | |
this.push(Buffer.concat([this._chunk, oldChunk.slice(0, freeSpaceLength)])); | |
this._chunk = sliceBySize( | |
oldChunk.slice(freeSpaceLength), | |
this._chunkSize, | |
(chunk) => this.push(chunk) | |
); | |
} else { | |
this._chunk = Buffer.concat([this._chunk, oldChunk]); | |
if (this._chunk.length >= this._chunkSize) { | |
this.push(this._chunk); | |
this._chunk = Buffer.alloc(0); | |
} | |
} | |
callback(); | |
} | |
_flush(callback) { | |
this.push(this._chunk); | |
callback(); | |
} | |
} | |
module.exports = ChunkerTransformStream; |
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