rochars / byte-data

 * Copyright (c) 2017-2018 Rafael da Silva Rocha.

 *

 * Permission is hereby granted, free of charge, to any person obtaining

 * a copy of this software and associated documentation files (the

 * "Software"), to deal in the Software without restriction, including

 * without limitation the rights to use, copy, modify, merge, publish,

 * distribute, sublicense, and/or sell copies of the Software, and to

 * permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE

 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION

 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 *

 */

/**

 * @fileoverview A function to swap endianness in byte buffers.

 * @see https://github.com/rochars/endianness

 */

/**

 * Swap the byte ordering in a buffer. The buffer is modified in place.

 * @param {!Array<number|string>|!Uint8Array} bytes The bytes.

 * @param {number} offset The byte offset.

 * @param {number=} index The start index. Assumes 0.

 * @param {?number=} end The end index. Assumes the buffer length.

 * @throws {Error} If the buffer length is not valid.

 */

  let limit = parseInt(offset / 2, 10);

  if (len % offset) {

    throw new Error("Bad buffer length.");

  }

  while (index < len) {

    swap(bytes, offset, index, limit);

    index += offset;

  }

}

/**

 * Swap the byte order of a value in a buffer. The buffer is modified in place.

 * @param {!Array<number|string>|!Uint8Array} bytes The bytes.

 * @param {number} offset The byte offset.

 * @param {number} index The start index.

 * @private

 */

function swap(bytes, offset, index, limit) {

  let x = 0;

  let y = offset - 1;

  while(x < limit) {

    let theByte = bytes[index + x];

    bytes[index + x] = bytes[index + y];

    bytes[index + y] = theByte;

    x++;

    y--;

  }

}