@loaders.gl/3d-tiles/src/3d-tiles-archive/3d-tiles-archive-archive.ts

3D Tiles, an open standard for streaming massive heterogeneous 3D geospatial datasets.

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright vis.gl contributors

import {FileProviderInterface} from '@loaders.gl/loader-utils';
import {MD5Hash} from '@loaders.gl/crypto';
import {DeflateCompression, NoCompression} from '@loaders.gl/compression';
import {IndexedArchive, parseZipLocalFileHeader} from '@loaders.gl/zip';

type CompressionHandler = (compressedFile: ArrayBuffer) => Promise<ArrayBuffer>;

/**
 * Handling different compression types in zip
 */
const COMPRESSION_METHODS: {[key: number]: CompressionHandler} = {
  /** No compression */
  0: (data) => new NoCompression().decompress(data),
  /** Deflation */
  8: (data) => new DeflateCompression({raw: true}).decompress(data)
};

/**
 * Class for handling information about 3tz file
 */
export class Tiles3DArchive extends IndexedArchive {
  /** hash info */
  private hashTable?: Record<string, bigint>;

  /**
   * creates Tiles3DArchive handler
   * @param fileProvider - FileProvider with the whole file
   * @param hashTable - hash info
   */
  constructor(
    fileProvider: FileProviderInterface,
    hashTable?: Record<string, bigint>,
    fileName?: string
  ) {
    super(fileProvider, hashTable, fileName);
    this.hashTable = hashTable;
  }

  /**
   * Returns file with the given path from 3tz archive
   * @param path - path inside the 3tz
   * @returns buffer with ready to use file
   */
  async getFile(path: string): Promise<ArrayBuffer> {
    // sometimes paths are not in lower case when hash file is created,
    // so first we're looking for lower case file name and then for original one
    let data = await this.getFileBytes(path.toLocaleLowerCase());
    if (!data) {
      data = await this.getFileBytes(path);
    }
    if (!data) {
      throw new Error(`No such file in the archive: ${path}`);
    }

    return data;
  }

  /**
   * Trying to get raw file data by adress
   * @param path - path inside the archive
   * @returns buffer with the raw file data
   */
  private async getFileBytes(path: string): Promise<ArrayBuffer | null> {
    let uncompressedFile: ArrayBuffer;
    if (this.hashTable) {
      const arrayBuffer = new TextEncoder().encode(path).buffer;
      const nameHash = await new MD5Hash().hash(arrayBuffer, 'hex');
      const byteOffset = this.hashTable[nameHash];
      if (byteOffset === undefined) {
        return null;
      }

      const localFileHeader = await parseZipLocalFileHeader(byteOffset, this.fileProvider);
      if (!localFileHeader) {
        return null;
      }

      const compressedFile = await this.fileProvider.slice(
        localFileHeader.fileDataOffset,
        localFileHeader.fileDataOffset + localFileHeader.compressedSize
      );

      const compressionMethod = COMPRESSION_METHODS[localFileHeader.compressionMethod];
      if (!compressionMethod) {
        throw Error('Only Deflation compression is supported');
      }

      uncompressedFile = await compressionMethod(compressedFile);
    } else {
      uncompressedFile = await this.getFileWithoutHash(path);
    }

    return uncompressedFile;
  }
}