Borewit
139 lines
3.8 KiB
TypeScript
139 lines
3.8 KiB
TypeScript
import type { IGetToken } from 'strtok3';
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import * as Token from 'token-types';
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import * as util from '../common/Util.js';
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import { StringType } from 'token-types';
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/**
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* Page header
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* Ref: https://www.xiph.org/ogg/doc/framing.html#page_header
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*/
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export interface IPageHeader {
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/**
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* capture_pattern
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* A header begins with a capture pattern that simplifies identifying pages;
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* once the decoder has found the capture pattern it can do a more intensive job of verifying that it has in fact found a page boundary (as opposed to an inadvertent coincidence in the byte stream).
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*/
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capturePattern: string,
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/**
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* stream_structure_version
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*/
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version: number,
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/**
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* header_type_flag
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*/
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headerType: {
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/**
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* True: continued packet;
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* False: fresh packet
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*/
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continued: boolean,
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/**
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* True: first page of logical bitstream (bos)
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* False: not first page of logical bitstream
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*/
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firstPage: boolean,
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/**
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* True: last page of logical bitstream (eos)
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* False: not last page of logical bitstream
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*/
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lastPage: boolean
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},
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/**
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* The total samples encoded after including all packets finished on this page
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* The position specified in the frame header of the last page tells how long the data coded by the bitstream is.
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*/
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absoluteGranulePosition: number,
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streamSerialNumber: number,
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pageSequenceNo: number,
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pageChecksum: number,
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/**
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* The number of segment entries to appear in the segment table.
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* The maximum number of 255 segments (255 bytes each) sets the maximum possible physical page size at 65307 bytes or
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* just under 64kB (thus we know that a header corrupted so as destroy sizing/alignment information will not cause a
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* runaway bitstream. We'll read in the page according to the corrupted size information that's guaranteed to be a
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* reasonable size regardless, notice the checksum mismatch, drop sync and then look for recapture).
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*/
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page_segments: number;
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}
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export const PageHeader: IGetToken<IPageHeader> = {
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len: 27,
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get: (buf, off): IPageHeader => {
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return {
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capturePattern: new StringType(4, 'latin1').get(buf, off),
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version: Token.UINT8.get(buf, off + 4),
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headerType: {
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continued: util.getBit(buf, off + 5, 0),
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firstPage: util.getBit(buf, off + 5, 1),
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lastPage: util.getBit(buf, off + 5, 2)
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},
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// packet_flag: Token.UINT8.get(buf, off + 5),
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absoluteGranulePosition: Number(Token.UINT64_LE.get(buf, off + 6)),
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streamSerialNumber: Token.UINT32_LE.get(buf, off + 14),
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pageSequenceNo: Token.UINT32_LE.get(buf, off + 18),
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pageChecksum: Token.UINT32_LE.get(buf, off + 22),
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page_segments: Token.UINT8.get(buf, off + 26)
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};
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}
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};
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export interface ISegmentTable {
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totalPageSize: number
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}
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export class SegmentTable implements IGetToken<ISegmentTable> {
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private static sum(buf: Uint8Array, off: number, len: number): number {
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const dv = new DataView(buf.buffer, 0);
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let s = 0;
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for (let i = off; i < off + len; ++i) {
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s += dv.getUint8(i);
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}
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return s;
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}
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public len: number;
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constructor(header: IPageHeader) {
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this.len = header.page_segments;
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}
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public get(buf: Uint8Array, off: number): ISegmentTable {
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return {
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totalPageSize: SegmentTable.sum(buf, off, this.len)
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};
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}
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}
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export interface IPageConsumer {
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/**
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* Need to parse to end to be able to calculate the duration
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*/
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durationOnLastPage: boolean;
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/**
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* Parse Ogg page
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* @param header Ogg page header
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* @param pageData Ogg page data
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*/
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parsePage(header: IPageHeader, pageData: Uint8Array): Promise<void>;
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/**
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* Calculate duration of provided header
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*/
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calculateDuration(enfOfStream: boolean): void;
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/**
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* Force to parse pending segments
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*/
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flush(): Promise<void>;
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}
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