rx-player/src/utils/byte_parsing.ts

Canal+ HTML5 Video Player

/**
 * Copyright 2015 CANAL+ Group
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Returns a Uint8Array from the arguments given, in order:
 *   - if the next argument given is a number N set the N next bytes to 0.
 *   - else set the next bytes to the argument given.
 * @param {...(Number|Uint8Array)} args
 * @returns {Uint8Array}
 */
function concat(...args: Array<Uint8Array | number[] | number>): Uint8Array<ArrayBuffer> {
  const l = args.length;
  let i = -1;
  let len = 0;
  let arg;
  while (++i < l) {
    arg = args[i];
    len += typeof arg === "number" ? arg : arg.length;
  }
  const arr = new Uint8Array(len);
  let offset = 0;
  i = -1;
  while (++i < l) {
    arg = args[i];
    if (typeof arg === "number") {
      offset += arg;
    } else if (arg.length > 0) {
      arr.set(arg, offset);
      offset += arg.length;
    }
  }
  return arr;
}

/**
 * Translate groups of 2 big-endian bytes to Integer (from 0 up to 65535).
 * @param {Uint8Array} bytes
 * @param {Number} offset - The offset (from the start of the given array)
 * @returns {Number}
 */
function be2toi(bytes: Uint8Array, offset: number): number {
  return (bytes[offset + 0] << 8) + (bytes[offset + 1] << 0);
}

/**
 * Translate groups of 3 big-endian bytes to Integer.
 * @param {Uint8Array} bytes
 * @param {Number} offset - The offset (from the start of the given array)
 * @returns {Number}
 */
function be3toi(bytes: Uint8Array, offset: number): number {
  return (
    bytes[offset + 0] * 0x0010000 + bytes[offset + 1] * 0x0000100 + bytes[offset + 2]
  );
}

/**
 * Translate groups of 4 big-endian bytes to Integer.
 * @param {Uint8Array} bytes
 * @param {Number} offset - The offset (from the start of the given array)
 * @returns {Number}
 */
function be4toi(bytes: Uint8Array, offset: number): number {
  return (
    bytes[offset + 0] * 0x1000000 +
    bytes[offset + 1] * 0x0010000 +
    bytes[offset + 2] * 0x0000100 +
    bytes[offset + 3]
  );
}

/**
 * Translate groups of 4 big-endian bytes representing a two's complement signed
 * integer to directly that value.
 * @param {Uint8Array} bytes
 * @param {Number} offset - The offset (from the start of the given array)
 * @returns {Number}
 */
function be4toiSigned(bytes: Uint8Array, offset: number): number {
  const value =
    (bytes[offset] << 24) |
    (bytes[offset + 1] << 16) |
    (bytes[offset + 2] << 8) |
    bytes[offset + 3];

  // Convert to signed 32-bit integer using JavaScript's bitwise OR
  // This handles the two's complement conversion properly
  return value | 0;
}

/**
 * Translate groups of 8 big-endian bytes to Integer.
 * @param {Uint8Array} bytes
 * @param {Number} offset - The offset (from the start of the given array)
 * @returns {Number}
 */
function be8toi(bytes: Uint8Array, offset: number): number {
  return (
    (bytes[offset + 0] * 0x1000000 +
      bytes[offset + 1] * 0x0010000 +
      bytes[offset + 2] * 0x0000100 +
      bytes[offset + 3]) *
      0x100000000 +
    bytes[offset + 4] * 0x1000000 +
    bytes[offset + 5] * 0x0010000 +
    bytes[offset + 6] * 0x0000100 +
    bytes[offset + 7]
  );
}

/**
 * Translate Integer (from 0 up to 65535) to a Uint8Array of length 2 of
 * the corresponding big-endian bytes.
 * @param {Number} num
 * @returns {Uint8Array}
 */
function itobe2(num: number): Uint8Array {
  return new Uint8Array([(num >>> 8) & 0xff, num & 0xff]);
}

/**
 * Translate Integer to a Uint8Array of length 4 of the corresponding big-endian
 * bytes.
 * @param {Number} num
 * @returns {Uint8Array}
 */
function itobe4(num: number): Uint8Array {
  return new Uint8Array([
    (num >>> 24) & 0xff,
    (num >>> 16) & 0xff,
    (num >>> 8) & 0xff,
    num & 0xff,
  ]);
}

/**
 * Translate Integer to a Uint8Array of length 8 of the corresponding big-endian
 * bytes.
 * /!\ If the top-most bytes are set, this might go over MAX_SAFE_INTEGER, thus
 * leading to a "bad" value.
 * @param {Number} num
 * @returns {Uint8Array}
 */
function itobe8(num: number): Uint8Array {
  const l = num % 0x100000000;
  const h = (num - l) / 0x100000000;
  return new Uint8Array([
    (h >>> 24) & 0xff,
    (h >>> 16) & 0xff,
    (h >>> 8) & 0xff,
    h & 0xff,
    (l >>> 24) & 0xff,
    (l >>> 16) & 0xff,
    (l >>> 8) & 0xff,
    l & 0xff,
  ]);
}

/**
 * Translate groups of 2 little-endian bytes to Integer (from 0 up to 65535).
 * @param {Uint8Array} bytes
 * @param {Number} offset - The offset (from the start of the given array)
 * @returns {Number}
 */
function le2toi(bytes: Uint8Array, offset: number): number {
  return (bytes[offset + 0] << 0) + (bytes[offset + 1] << 8);
}

/**
 * Translate groups of 4 little-endian bytes to Integer.
 * @param {Uint8Array} bytes
 * @param {Number} offset - The offset (from the start of the given array)
 * @returns {Number}
 */
function le4toi(bytes: Uint8Array, offset: number): number {
  return (
    bytes[offset + 0] +
    bytes[offset + 1] * 0x0000100 +
    bytes[offset + 2] * 0x0010000 +
    bytes[offset + 3] * 0x1000000
  );
}

/**
 * Translate groups of 8 little-endian bytes to Integer.
 * @param {Uint8Array} bytes
 * @param {Number} offset - The offset (from the start of the given array)
 * @returns {Number}
 */
function le8toi(bytes: Uint8Array, offset: number): number {
  return (
    bytes[offset + 0] +
    bytes[offset + 1] * 0x0000100 +
    bytes[offset + 2] * 0x0010000 +
    bytes[offset + 3] * 0x1000000 +
    (bytes[offset + 4] +
      bytes[offset + 5] * 0x0000100 +
      bytes[offset + 6] * 0x0010000 +
      bytes[offset + 7] * 0x1000000) *
      0x100000000
  );
}

/**
 * Translate Integer (from 0 up to 65535) to a Uint8Array of length 2 of
 * the corresponding little-endian bytes.
 * @param {Number} num
 * @returns {Uint8Array}
 */
function itole2(num: number): Uint8Array {
  return new Uint8Array([num & 0xff, (num >>> 8) & 0xff]);
}

/**
 * Translate Integer to a Uint8Array of length 4 of the corresponding
 * little-endian bytes.
 * @param {Number} num
 * @returns {Uint8Array}
 */
function itole4(num: number): Uint8Array {
  return new Uint8Array([
    num & 0xff,
    (num >>> 8) & 0xff,
    (num >>> 16) & 0xff,
    (num >>> 24) & 0xff,
  ]);
}

/**
 * Check if an ArrayBuffer is equal to the bytes given.
 * @param {ArrayBuffer} buffer
 * @param {Uint8Array} bytes
 * @returns {Boolean}
 */
function isABEqualBytes(buffer: ArrayBuffer, bytes: Uint8Array): boolean {
  const view = new DataView(buffer);
  const len = view.byteLength;
  if (len !== bytes.length) {
    return false;
  }
  for (let i = 0; i < len; i++) {
    if (view.getUint8(i) !== bytes[i]) {
      return false;
    }
  }
  return true;
}

/**
 * Convert any BufferSource-typed structure into the corresponding Uint8Array.
 * @param {BufferSource} input
 * @returns {Uint8Array}
 */
function toUint8Array(
  input: ArrayBufferView<ArrayBuffer> | ArrayBuffer,
): Uint8Array<ArrayBuffer> {
  if (input instanceof Uint8Array) {
    // TypeScript's just dumb here
    return input as Uint8Array<ArrayBuffer>;
  } else if (input instanceof ArrayBuffer) {
    return new Uint8Array(input);
  } else {
    return new Uint8Array(input.buffer);
  }
}

export {
  concat,
  be2toi,
  be3toi,
  be4toi,
  be4toiSigned,
  be8toi,
  le2toi,
  le4toi,
  le8toi,
  itobe2,
  itobe4,
  itobe8,
  itole2,
  itole4,
  isABEqualBytes,
  toUint8Array,
};