bufferToStreams.js

var AWS = require('aws-sdk');
var ReadableStream = AWS.util.nodeRequire('stream').Readable;

function bufferToStream(buffer) {
    if (!AWS.util.Buffer.isBuffer(buffer)) buffer = new AWS.util.Buffer(buffer);

    var readable = new ReadableStream();
    var pos = 0;
    readable._read = function(size) {
        if (pos >= buffer.length) return readable.push(null);

        var end = pos + size;
        if (end > buffer.length) end = buffer.length;
        readable.push(buffer.slice(pos, end));
        pos = end;
    };

    return readable;
}

function bufferToStreamHighWater(buffer) {
    if (!AWS.util.Buffer.isBuffer(buffer)) buffer = new AWS.util.Buffer(buffer);

    var readable = new ReadableStream({ highWaterMark: 5 * Math.pow(1024, 2) });
    var pos = 0;
    readable._read = function(size) {
        if (pos >= buffer.length) return readable.push(null);

        var end = pos + size;
        if (end > buffer.length) end = buffer.length;
        readable.push(buffer.slice(pos, end));
        pos = end;
    };

    return readable;
}

function bufferToStreamImmediate(buffer) {
    if (!AWS.util.Buffer.isBuffer(buffer)) buffer = new AWS.util.Buffer(buffer);

    var readable = new ReadableStream();
    var pos = 0;
    readable._read = function(size) {
        if (pos >= buffer.length) return readable.push(null);

        var end = pos + size;
        if (end > buffer.length) end = buffer.length;

        setImmediate(function() {
            readable.push(buffer.slice(pos, end));
            pos = end;
        });
    };

    return readable;
}

var ten = new Buffer(10 * Math.pow(1024, 2));
var twenty = new Buffer(20 * Math.pow(1024, 2));

// Works: small enough
// bufferToStream(ten).pipe(process.stdout);

// Fails: too big
// bufferToStream(twenty).pipe(process.stdout);

// Works: highWaterMark
// bufferToStreamHighWater(twenty).pipe(process.stdout);

// Works: setImmediate
// bufferToStreamImmediate(twenty).pipe(process.stdout);