Package Exports

o-stream

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (o-stream) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

O-Stream

Provides an intuitive interface for node streams, in typescript.

Useful for creating streams and gulp plugins (there is an example).

Install

npm install --save o-stream

Or dev:
npm install --save-dev o-stream

Basic Usage

Simple transform stream:

import ObjectStream, { EnteredArgs } from "o-stream"

let incrementStream = ObjectStream.transform<number, number>({
    onEntered: (args: EnteredArgs<number, number>) => {
        args.output.push(args.object + 1);
    }
});

stream.write(4);

let actual = stream.read(); // 5

Output on stream end:

import ObjectStream, { EnteredArgs, EndedArgs } from "o-stream"

let sum = 0;
let sumStream = ObjectStream.transform<number, number>({
    onEntered: (args: EnteredArgs<number, number>) => {
        sum += args.object;
    },
    onEnded: (args: EndedArgs<number>) => {
        args.output.push(sum);
    }
});

sumStream.write(100);
sumStream.write(5);
sumStream.write(-10);
sumStream.end();

let actualSum = sumStream.read(); // 95

Async:

import ObjectStream, { EnteredAsyncArgs, EndedAsyncArgs } from "o-stream"

let sum = 0;
let sumStream = ObjectStream.transform<number, number>({
    onEnteredAsync: (args: EnteredAsyncArgs<number, number>) => {
        sum += args.object;
        args.done();
    },
    onEndedAsync: (args: EndedAsyncArgs<number>) => {
        args.output.push(sum);
        args.done();
    }
});

let num1 = 4;
let num2 = 6;
let num3 = -1;
let expected = num1 + num2 + num3;

sumStream.write(num1);
sumStream.write(num2);
sumStream.write(num3);
sumStream.end();

let actual = sumStream.read();

expect(actual).toBe(expected);

Create a stream from an array:

import ObjectStream from "o-stream"

let stream = ObjectStream.fromArray([1, 2, 3, 5, 8, 13]);

Gulp plugin example

This example creates a single file listing the input files names:

import ObjectStream, { EnteredArgs, EndedArgs, Transform } from "o-stream";
import * as gutil from "gulp-util"; // install --save-dev @types/gulp-utils

export default function plugin(outFilePath: string): Transform {

    let myPaths: string[] = [];

    return ObjectStream.transform({
        onEntered: (args: EnteredArgs<gutil.File, gutil.File>) => {
            myPaths.push(args.object.relative);
        },
        onEnded: (args: EndedArgs<gutil.File>) => {
            let file = new gutil.File({
                cwd: "",
                base: "",
                path: outFilePath,
                contents: new Buffer(myPaths.join("\n"))
            })

            args.output.push(file);
        }
    });
}

Combine streams: Creates a stream that passes data through multiple underling streams.

import ObjectStream, { EnteredArgs, EndedArgs } from "o-stream"

// Just appends some string to the input string.
function createAppendStream(append: string): NodeJS.ReadWriteStream {
    return ObjectStream.transform<string, string>({
        onEntered: args => { args.output.push(args.object + append); }
    });
}

let combined = new CombinedStream([
    createAppendStream("b"),
    createAppendStream("c"),
    createAppendStream("d"),
    createAppendStream("e")
]);

combined.write("a");

let actual = combined.read();

expect(actual).to.equal("abcde");

Error handling

Node streams do not propagate errors.
ObjectStreams(created with this library), by default, propagate errors.
It means that errors emitted from a source stream will be re-emitted from the current stream.
You can override the default error handling:

import ObjectStream, { EnteredArgs } from "o-stream"

let myStream = ObjectStream.transform<number, number>({
        onSourceStreamError: args => args.emitError(args.error + "b")
    });

Require Usage

let ostream = require('o-stream').default;