StreamReader.jsā¢2.5 kB
import { AbortError, } from './Errors.js';
import { Deferred } from './Deferred.js';
import { AbstractStreamReader } from "./AbstractStreamReader.js";
/**
* Node.js Readable Stream Reader
* Ref: https://nodejs.org/api/stream.html#readable-streams
*/
export class StreamReader extends AbstractStreamReader {
constructor(s) {
super();
this.s = s;
/**
* Deferred used for postponed read request (as not data is yet available to read)
*/
this.deferred = null;
if (!s.read || !s.once) {
throw new Error('Expected an instance of stream.Readable');
}
this.s.once('end', () => {
this.endOfStream = true;
if (this.deferred) {
this.deferred.resolve(0);
}
});
this.s.once('error', err => this.reject(err));
this.s.once('close', () => this.abort());
}
/**
* Read chunk from stream
* @param buffer Target Uint8Array (or Buffer) to store data read from stream in
* @param mayBeLess - If true, may fill the buffer partially
* @returns Number of bytes read
*/
async readFromStream(buffer, mayBeLess) {
if (buffer.length === 0)
return 0;
const readBuffer = this.s.read(buffer.length);
if (readBuffer) {
buffer.set(readBuffer);
return readBuffer.length;
}
const request = {
buffer,
mayBeLess,
deferred: new Deferred()
};
this.deferred = request.deferred;
this.s.once('readable', () => {
this.readDeferred(request);
});
return request.deferred.promise;
}
/**
* Process deferred read request
* @param request Deferred read request
*/
readDeferred(request) {
const readBuffer = this.s.read(request.buffer.length);
if (readBuffer) {
request.buffer.set(readBuffer);
request.deferred.resolve(readBuffer.length);
this.deferred = null;
}
else {
this.s.once('readable', () => {
this.readDeferred(request);
});
}
}
reject(err) {
this.interrupted = true;
if (this.deferred) {
this.deferred.reject(err);
this.deferred = null;
}
}
async abort() {
this.reject(new AbortError());
}
async close() {
return this.abort();
}
}