rochars / uint-buffer

index.js

/*
 * Copyright (c) 2018-2019 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 Encode and decode unsigned integers to and from byte buffers.
 * @see https://github.com/rochars/uint-buffer
 */

/** @module uint-buffer */

/**
 * A class to write and read unsigned ints to and from byte buffers.
 */
export class UintBuffer {
  
  /**
   * @param {number} bits The number of bits used by the integer.
   */
  constructor(bits) {

This code seems to be duplicated in your project.

    /**
     * The number of bits used by one number.
     * @type {number}
     */
    this.bits = bits;
    /**
     * The number of bytes used by one number.
     * @type {number}
     */
    this.bytes = bits < 8 ? 1 : Math.ceil(bits / 8);
    /**
     * @type {number}
     * @protected
     */
    this.max = Math.pow(2, bits) - 1;
    /**
     * @type {number}
     * @protected
     */
    this.min = 0;
    /** @type {number} */
    let r = 8 - ((((bits - 1) | 7) + 1) - bits);
    /**
     * @type {number}
     * @private
     */
    this.lastByteMask_ = Math.pow(2, r > 0 ? r : 8) - 1;
  }

  /**
   * Write one unsigned integer to a byte buffer.
   * @param {!Uint8Array|!Array<number>} buffer An array of bytes.
   * @param {number} num The number.
   * @param {number=} index The index being written in the byte buffer.
   * @return {number} The next index to write on the byte buffer.
   * @throws {TypeError} If num is not a number.
   * @throws {RangeError} On overflow.
   */
  pack(buffer, num, index=0) {
    if (num !== num || typeof num != 'number') {
      throw new TypeError();
    }
    this.overflow(num);
    buffer[index] = (num < 0 ? num + Math.pow(2, this.bits) : num) & 255;
    index++;
    /** @type {number} */
    let len = this.bytes;
    for (let i = 2; i < len; i++) {
      buffer[index] = Math.floor(num / Math.pow(2, ((i - 1) * 8))) & 255;
      index++;
    }
    if (this.bits > 8) {
      buffer[index] = Math.floor(
          num / Math.pow(2, ((this.bytes - 1) * 8))) & this.lastByteMask_;
      index++;
    }
    return index;
  }
  
  /**
   * Read one unsigned integer from a byte buffer.
   * @param {!Uint8Array|!Array<number>} buffer An array of bytes.
   * @param {number=} index The index to read.
   * @return {number} The number.
   * @throws {RangeError} On overflow.
   */
  unpack(buffer, index=0) {
    /** @type {number} */
    let num = this.unpackUnsafe(buffer, index);
    this.overflow(num);
    return num; 
  }

  /**
   * Read one unsigned integer from a byte buffer.
   * Does not check for overflows.
   * @param {!Uint8Array|!Array<number>} buffer An array of bytes.
   * @param {number} index The index to read.
   * @return {number}
   * @protected
   */
  unpackUnsafe(buffer, index) {
    /** @type {number} */
    let num = 0;
    for(let x = 0; x < this.bytes; x++) {
      num += buffer[index + x] * Math.pow(256, x);
    }
    return num;
  }

  /**
   * Throws range error in case of overflow.
   * @param {number} num The number.
   * @throws {RangeError} On overflow.
   * @protected
   */
  overflow(num) {
    if (num > this.max || num < this.min) {
      throw new RangeError();
    }
  }
}