visgl / loaders.gl / 20382848403

// loaders.gl

// SPDX-License-Identifier: MIT

// Copyright (c) vis.gl contributors

import zlib from 'zlib';

import {Readable} from 'stream';

import {toArrayBuffer} from '@loaders.gl/loader-utils';

/**

 *

 */

export function decompressReadStream(readStream: Readable, headers?: Headers) {

  switch (headers?.get('content-encoding')) {

    case 'br':

      return readStream.pipe(zlib.createBrotliDecompress());

    case 'gzip':

      return readStream.pipe(zlib.createGunzip());

    case 'deflate':

      return readStream.pipe(zlib.createDeflate());

    default:

      // No compression or an unknown one, just return it as is

      return readStream;

  }

}

/**

 *

 * @param readStream

 * @returns

 */

export async function concatenateReadStream(readStream): Promise<ArrayBuffer> {

  const arrayBufferChunks: ArrayBuffer[] = [];

  return await new Promise((resolve, reject) => {

    readStream.on('error', (error) => reject(error));

    // Once the readable callback has been added, stream switches to "flowing mode"

    // In Node 10 (but not 12 and 14) this causes `data` and `end` to never be called unless we read data here

    readStream.on('readable', () => readStream.read());

    readStream.on('data', (chunk) => {

      if (typeof chunk === 'string') {

        reject(new Error('Read stream not binary'));

      }

      arrayBufferChunks.push(toArrayBuffer(chunk));

    });

    readStream.on('end', () => {

      const arrayBuffer = concatenateArrayBuffers(arrayBufferChunks);

      resolve(arrayBuffer);

    });

  });

}

/**

 * Concatenate a sequence of ArrayBuffers

 * @return A concatenated ArrayBuffer

 * @note duplicates loader-utils since polyfills should be independent

 */

export function concatenateArrayBuffers(sources: (ArrayBuffer | Uint8Array)[]): ArrayBuffer {

  // Make sure all inputs are wrapped in typed arrays

  const sourceArrays = sources.map((source2) =>

    source2 instanceof ArrayBuffer ? new Uint8Array(source2) : source2

  );

  // Get length of all inputs

  const byteLength = sourceArrays.reduce((length, typedArray) => length + typedArray.byteLength, 0);

  // Allocate array with space for all inputs

  const result = new Uint8Array(byteLength);

  // Copy the subarrays

  let offset = 0;

  for (const sourceArray of sourceArrays) {

    result.set(sourceArray, offset);

    offset += sourceArray.byteLength;

  }

  // We work with ArrayBuffers, discard the typed array wrapper

  return result.buffer;

}