buffer to stream

bufferStream.js

const stream = require( "stream" )
const fileSystem = require( "fs" )
const util = require( "util" )

// turn the given source Buffer into a Readable stream.
function BufferStream(source) {
    if (!Buffer.isBuffer(source)) {
        throw(new Error("Source must be a buffer."))
    }
    // Super constructor.
    stream.Readable.call(this)

    this._source = source

    // keep track of which portion of the source buffer is currently being pushed
    // onto the internal stream buffer during read actions.
    this._offset = 0
    this._length = source.length

    // When the stream has ended, try to clean up the memory references.
    this.on("end", this._destroy)
}

util.inherits(BufferStream, stream.Readable)

// I attempt to clean up variable references once the stream has been ended.
// --
// NOTE: I am not sure this is necessary. But, I'm trying to be more cognizant of memory
// usage since my Node.js apps will (eventually) never restart.
BufferStream.prototype._destroy = function() {
    this._source = null
    this._offset = null
    this._length = null
    console.log('stream ended')
}


// I read chunks from the source buffer into the underlying stream buffer.
// --
// NOTE: We can assume the size value will always be available since we are not
// altering the readable state options when initializing the Readable stream.
BufferStream.prototype._read = function(size) {
    //set the size equal to the fixedSizedChunker
    size = 262144

    // If we haven't reached the end of the source buffer, push the next chunk onto
    // the internal stream buffer.
    if (this._offset < this._length) {
        this.push( this._source.slice(this._offset, (this._offset + size)))
        this._offset += size
    }

    //No size chunking, pushing the whole buffer, this results in an extra chunk coming out
    /*if (this._offset < this._length) {
        this.push( this._source )
        this._offset += this._length
    }*/
    
    // If we've consumed the entire source buffer, close the readable stream.
    if (this._offset >= this._length) {
        console.log('null pushed')
        this.push(null)
    }
}

module.exports = function (buffer) { 
    return new BufferStream(buffer)
}