serverless-spy
Version:
CDK-based library for writing elegant integration tests on AWS serverless architecture and an additional web console to monitor events in real time.
42 lines (41 loc) • 1.42 kB
JavaScript
import { Writable } from "stream";
import { headStream as headWebStream } from "./headStream.browser";
import { isReadableStream } from "./stream-type-check";
export const headStream = (stream, bytes) => {
if (isReadableStream(stream)) {
return headWebStream(stream, bytes);
}
return new Promise((resolve, reject) => {
const collector = new Collector();
collector.limit = bytes;
stream.pipe(collector);
stream.on("error", (err) => {
collector.end();
reject(err);
});
collector.on("error", reject);
collector.on("finish", function () {
const bytes = new Uint8Array(Buffer.concat(this.buffers));
resolve(bytes);
});
});
};
class Collector extends Writable {
constructor() {
super(...arguments);
this.buffers = [];
this.limit = Infinity;
this.bytesBuffered = 0;
}
_write(chunk, encoding, callback) {
this.buffers.push(chunk);
this.bytesBuffered += chunk.byteLength ?? 0;
if (this.bytesBuffered >= this.limit) {
const excess = this.bytesBuffered - this.limit;
const tailBuffer = this.buffers[this.buffers.length - 1];
this.buffers[this.buffers.length - 1] = tailBuffer.subarray(0, tailBuffer.byteLength - excess);
this.emit("finish");
}
callback();
}
}