recoder-code
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JavaScript
import { EndOfStreamError, AbortError } from "./Errors.js";
export class AbstractStreamReader {
constructor() {
this.endOfStream = false;
this.interrupted = false;
/**
* Store peeked data
* @type {Array}
*/
this.peekQueue = [];
}
async peek(uint8Array, mayBeLess = false) {
const bytesRead = await this.read(uint8Array, mayBeLess);
this.peekQueue.push(uint8Array.subarray(0, bytesRead)); // Put read data back to peek buffer
return bytesRead;
}
async read(buffer, mayBeLess = false) {
if (buffer.length === 0) {
return 0;
}
let bytesRead = this.readFromPeekBuffer(buffer);
if (!this.endOfStream) {
bytesRead += await this.readRemainderFromStream(buffer.subarray(bytesRead), mayBeLess);
}
if (bytesRead === 0 && !mayBeLess) {
throw new EndOfStreamError();
}
return bytesRead;
}
/**
* Read chunk from stream
* @param buffer - Target Uint8Array (or Buffer) to store data read from stream in
* @returns Number of bytes read
*/
readFromPeekBuffer(buffer) {
let remaining = buffer.length;
let bytesRead = 0;
// consume peeked data first
while (this.peekQueue.length > 0 && remaining > 0) {
const peekData = this.peekQueue.pop(); // Front of queue
if (!peekData)
throw new Error('peekData should be defined');
const lenCopy = Math.min(peekData.length, remaining);
buffer.set(peekData.subarray(0, lenCopy), bytesRead);
bytesRead += lenCopy;
remaining -= lenCopy;
if (lenCopy < peekData.length) {
// remainder back to queue
this.peekQueue.push(peekData.subarray(lenCopy));
}
}
return bytesRead;
}
async readRemainderFromStream(buffer, mayBeLess) {
let bytesRead = 0;
// Continue reading from stream if required
while (bytesRead < buffer.length && !this.endOfStream) {
if (this.interrupted) {
throw new AbortError();
}
const chunkLen = await this.readFromStream(buffer.subarray(bytesRead), mayBeLess);
if (chunkLen === 0)
break;
bytesRead += chunkLen;
}
if (!mayBeLess && bytesRead < buffer.length) {
throw new EndOfStreamError();
}
return bytesRead;
}
}