暂停和缓冲流

Question

I have a stream of files, and at some point i need to pause my stream, wait until it finish and buffers, and then continue.

Example:

var eventStream = require('event-stream')
gulp.task('test', () => {
    eventStream.readArray([1, 2, 3, 4, 5])
        .pipe(gulpTap((data) => {
            console.log('d1:', data);
        }))
        .pipe(gulpTap((data) => {
            console.log('d2:', data);
        }))
        .on('end', function () {
            console.log('ended');
        });
})

prints:
d1 1
d2 1
d1 2
d2 2
d1 3
d2 3
ended

when i want it to be like:
d1 1
d1 2
d1 3
d2 1
d2 2
d2 3

The reason here is that i want to collect some data from all files in one object, and then provide it to other objects, so i need a some kind of sync in the middle of pipe chain

Answer 1

You can do this with the help of through2 , eg:

const eventStream = require('event-stream');
const through = require('through2');

gulp.task('test', () => {
    const input = [];

    eventStream.readArray([1, 2, 3, 4, 5])
        .pipe(through.obj((data, enc, done) => {
            // Save data and remove from stream
            input.push(data);

            console.log('d1:', data);
            return done();
        }, function(done) {
            // Return "buffered" data back to stream
            input.forEach(this.push.bind(this));

            return done();
        }))
        .pipe(through.obj((data, enc, done) => {
            console.log('d2:', data);
            return done(null, data);
        }))
        .on('end', function () {
            console.log('ended');
        });
});

Real-life example: https://github.com/sirlantis/gulp-order