Add extension for tokenizer for random access to media

lib/AbstractTokenizer.ts

@@ -14,17 +14,23 @@ interface INormalizedReadChunkOptions extends IReadChunkOptions {
  */
 export abstract class AbstractTokenizer implements ITokenizer {
 
-  public fileInfo: IFileInfo;
-
   private onClose?: OnClose;
+  private numBuffer = new Uint8Array(8);
+
+  public abstract fileInfo: IFileInfo;
+
+  /**
+   * Tokenizer-stream position
+   */
+  public position = 0;
+
 
   /**
    * Constructor
    * @param options Tokenizer options
    * @protected
    */
   protected constructor(options?: ITokenizerOptions) {
-    this.fileInfo = options?.fileInfo ?? {};
     this.onClose = options?.onClose;
     if (options?.abortSignal) {
       options.abortSignal.addEventListener('abort', () => {
@@ -33,12 +39,7 @@ export abstract class AbstractTokenizer implements ITokenizer {
     }
   }
 
-  /**
-   * Tokenizer-stream position
-   */
-  public position = 0;
-
-  private numBuffer = new Uint8Array(8);
+  abstract supportsRandomAccess(): boolean;
 
   /**
    * Read buffer from tokenizer

lib/BufferTokenizer.ts

@@ -1,8 +1,10 @@
-import type { ITokenizerOptions, IReadChunkOptions } from './types.js';
+import type {ITokenizerOptions, IReadChunkOptions, IRandomAccessFileInfo, IRandomAccessTokenizer} from './types.js';
 import { EndOfStreamError } from 'peek-readable';
 import { AbstractTokenizer } from './AbstractTokenizer.js';
 
-export class BufferTokenizer extends AbstractTokenizer {
+export class BufferTokenizer extends AbstractTokenizer implements IRandomAccessTokenizer {
+
+  public fileInfo: IRandomAccessFileInfo;
 
   /**
    * Construct BufferTokenizer
@@ -11,7 +13,7 @@ export class BufferTokenizer extends AbstractTokenizer {
    */
   constructor(private uint8Array: Uint8Array, options?: ITokenizerOptions) {
     super(options);
-    this.fileInfo.size = this.fileInfo.size ? this.fileInfo.size : uint8Array.length;
+    this.fileInfo = {...options?.fileInfo ?? {}, ...{size: uint8Array.length}};
   }
 
   /**
@@ -55,4 +57,12 @@ export class BufferTokenizer extends AbstractTokenizer {
   public close(): Promise<void> {
     return super.close();
   }
+
+  supportsRandomAccess(): boolean {
+    return true;
+  }
+
+  setPosition(position: number): void {
+    this.position = position;
+  }
 }

lib/FileTokenizer.ts

@@ -1,12 +1,32 @@
 import { AbstractTokenizer } from './AbstractTokenizer.js';
 import { EndOfStreamError } from 'peek-readable';
-import type { IReadChunkOptions, ITokenizerOptions } from './types.js';
+import type {IRandomAccessTokenizer, IRandomAccessFileInfo, IReadChunkOptions, ITokenizerOptions} from './types.js';
 import { type FileHandle, open as fsOpen } from 'node:fs/promises';
 
-export class FileTokenizer extends AbstractTokenizer {
+interface IFileTokenizerOptions extends ITokenizerOptions {
+  /**
+   * Pass additional file information to the tokenizer
+   */
+  fileInfo: IRandomAccessFileInfo;
+}
+
+export class FileTokenizer extends AbstractTokenizer implements IRandomAccessTokenizer {
 
-  public constructor(private fileHandle: FileHandle, options: ITokenizerOptions) {
+  public fileInfo: IRandomAccessFileInfo;
+
+  /**
+   * Create tokenizer from provided file path
+   * @param sourceFilePath File path
+   */
+  static async fromFile(sourceFilePath: string): Promise<FileTokenizer> {
+    const fileHandle = await fsOpen(sourceFilePath, 'r');
+    const stat = await fileHandle.stat();
+    return new FileTokenizer(fileHandle, {fileInfo: {path: sourceFilePath, size: stat.size}});
+  }
+
+  protected constructor(private fileHandle: FileHandle, options: IFileTokenizerOptions) {
     super(options);
+    this.fileInfo = options.fileInfo;
   }
 
   /**
@@ -48,10 +68,14 @@ export class FileTokenizer extends AbstractTokenizer {
     await this.fileHandle.close();
     return super.close();
   }
-}
 
-export async function fromFile(sourceFilePath: string): Promise<FileTokenizer> {
-  const fileHandle = await fsOpen(sourceFilePath, 'r');
-  const stat = await fileHandle.stat();
-  return new FileTokenizer(fileHandle, {fileInfo: {path: sourceFilePath, size: stat.size}});
+  setPosition(position: number): void {
+    this.position = position;
+  }
+
+  supportsRandomAccess(): boolean {
+    return true;
+  }
 }
+
+

lib/ReadStreamTokenizer.ts

@@ -1,18 +1,21 @@
 import { AbstractTokenizer } from './AbstractTokenizer.js';
 import { EndOfStreamError, type IStreamReader } from 'peek-readable';
-import type { IReadChunkOptions, ITokenizerOptions } from './types.js';
+import type {IFileInfo, IReadChunkOptions, ITokenizerOptions} from './types.js';
 
 const maxBufferSize = 256000;
 
 export class ReadStreamTokenizer extends AbstractTokenizer {
 
+  public fileInfo: IFileInfo;
+
   /**
    * Constructor
    * @param streamReader stream-reader to read from
    * @param options Tokenizer options
    */
   public constructor(private streamReader: IStreamReader, options?: ITokenizerOptions) {
     super(options);
+    this.fileInfo = options?.fileInfo ?? {};
   }
 
   /**
@@ -102,4 +105,8 @@ export class ReadStreamTokenizer extends AbstractTokenizer {
   public abort(): Promise<void> {
     return this.streamReader.abort();
   }
+
+  supportsRandomAccess(): boolean {
+    return false;
+  }
 }

lib/core.ts

@@ -6,7 +6,7 @@ import { BufferTokenizer } from './BufferTokenizer.js';
 import type { ITokenizerOptions } from './types.js';
 
 export { EndOfStreamError, type AnyWebByteStream } from 'peek-readable';
-export type { ITokenizer, IFileInfo, ITokenizerOptions, IReadChunkOptions, OnClose } from './types.js';
+export type { ITokenizer, IRandomAccessTokenizer, IFileInfo, ITokenizerOptions, IReadChunkOptions, OnClose } from './types.js';
 export type { IToken, IGetToken } from '@tokenizer/token';
 export { AbstractTokenizer } from './AbstractTokenizer.js';
 

lib/index.ts

@@ -2,8 +2,9 @@ import type { Readable } from 'node:stream';
 import type { ReadStreamTokenizer } from './ReadStreamTokenizer.js';
 import { stat as fsStat } from 'node:fs/promises';
 import { type ITokenizerOptions, fromStream as coreFromStream } from './core.js';
+import {FileTokenizer} from "./FileTokenizer.js";
 
-export { fromFile } from './FileTokenizer.js';
+export { FileTokenizer } from './FileTokenizer.js';
 export * from './core.js';
 export type { IToken, IGetToken } from '@tokenizer/token';
 
@@ -22,12 +23,13 @@ interface StreamWithFile extends Readable {
  * @returns Tokenizer
  */
 export async function fromStream(stream: Readable, options?: ITokenizerOptions): Promise<ReadStreamTokenizer> {
-  const augmentedOptions: ITokenizerOptions = options ?? {};
-  augmentedOptions.fileInfo = augmentedOptions.fileInfo ?? {};
+  const rst = coreFromStream(stream, options);
   if ((stream as StreamWithFile).path) {
     const stat = await fsStat((stream as StreamWithFile).path as string);
-    augmentedOptions.fileInfo.path = (stream as StreamWithFile).path;
-    augmentedOptions.fileInfo.size = stat.size;
+    rst.fileInfo.path = (stream as StreamWithFile).path;
+    rst.fileInfo.size = stat.size;
   }
-  return coreFromStream(stream, augmentedOptions);
+  return rst;
 }
+
+export const fromFile = FileTokenizer.fromFile;

lib/types.ts

@@ -21,6 +21,13 @@ export interface IFileInfo {
   url?: string;
 }
 
+export interface IRandomAccessFileInfo extends IFileInfo {
+  /**
+   * File size in bytes
+   */
+  size: number;
+}
+
 export interface IReadChunkOptions {
 
   /**
@@ -36,16 +43,30 @@ export interface IReadChunkOptions {
   /**
    * Position where to begin reading from the file.
    * Default it is `tokenizer.position`.
-   * Position may not be less then `tokenizer.position`.
+   * Position may not be less than `tokenizer.position`, unless `supportsRandomAccess()` returns `true`.
    */
   position?: number;
 
   /**
-   * If set, will not throw an EOF error if not all of the requested data could be read
+   * If set, will not throw an EOF error if not all off the requested data could be read
    */
   mayBeLess?: boolean;
 }
 
+export interface IRandomAccessTokenizer extends ITokenizer {
+
+  /**
+   * Provide access to information of the underlying information stream or file.
+   */
+  fileInfo: IRandomAccessFileInfo;
+
+  /**
+   * Change the position (offset) of the tokenizer
+   * @param position New position
+   */
+  setPosition(position: number): void;
+}
+
 /**
  * The tokenizer allows us to read or peek from the tokenizer-stream.
  * The tokenizer-stream is an abstraction of a stream, file or Buffer.
@@ -55,12 +76,12 @@ export interface ITokenizer {
   /**
    * Provide access to information of the underlying information stream or file.
    */
-  fileInfo: IFileInfo;
+  readonly fileInfo: IFileInfo;
 
   /**
    * Offset in bytes (= number of bytes read) since beginning of file or stream
    */
-  position: number;
+  readonly position: number;
 
   /**
    * Peek (read ahead) buffer from tokenizer
@@ -123,6 +144,11 @@ export interface ITokenizer {
    * Abort pending asynchronous operations
    */
   abort(): Promise<void>;
+
+  /**
+   * Returns true when the underlying file supports random access
+   */
+  supportsRandomAccess(): boolean;
 }
 
 export type OnClose = () => Promise<void>;

test/test.ts

@@ -9,7 +9,6 @@ import { assert, expect, use } from 'chai';
 import chaiAsPromised from 'chai-as-promised';
 import { fromStream, fromWebStream, fromFile, fromBuffer, type ITokenizer } from '../lib/index.js';
 import Path from 'node:path';
-import { FileTokenizer } from '../lib/FileTokenizer.js';
 import { EndOfStreamError } from 'peek-readable';
 
 import mocha from 'mocha';
@@ -617,7 +616,7 @@ describe('Matrix tests', () => {
 
           const rst = await tokenizerType.loadTokenizer('test1.dat');
 
-          if (rst instanceof FileTokenizer) {
+          if (rst.supportsRandomAccess()) {
             assert.strictEqual(rst.fileInfo.size, 16, 'check file size property');
           }
           await peekOnData(rst);
@@ -993,5 +992,27 @@ it('should release stream after close', async () => {
   assert.isFalse(stream.locked, 'stream is unlocked after closing tokenizer');
 });
 
+describe('Random-read-acccess', async () => {
+
+  it('Read ID3v1 header at the end of the file', async () => {
+
+    const tokenizer = await fromFile(getResourcePath('id3v1.mp3'));
+    try {
+      const id3HeaderSize = 128;
+      const id3Header = new Uint8Array(id3HeaderSize);
+      await tokenizer.readBuffer(id3Header,{position: tokenizer.fileInfo.size - id3HeaderSize});
+      const id3Tag = new TextDecoder('utf-8').decode(id3Header.subarray(0, 3));
+      assert.strictEqual(id3Tag, 'TAG');
+      assert.strictEqual(tokenizer.position, tokenizer.fileInfo.size, 'Tokenizer position should be at the end of the file');
+      tokenizer.setPosition(0);
+      assert.strictEqual(tokenizer.position, 0, 'Tokenizer position should be at the beginning of the file');
+    }
+    finally {
+      await tokenizer.close();
+    }
+  });
+
+});
+