main.js

/*
 * Copyright (c) 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 The utf8-buffer-size API.
 * @see https://github.com/rochars/utf8-buffer-size
 */

/** @module utf8BufferSize */

/**
 * Returns how many bytes are needed to serialize a UTF-8 string.
 * @see https://encoding.spec.whatwg.org/#utf-8-encoder
 * @param {string} str The string to pack.
 * @return {number} The number of bytes needed to serialize the string.
 */
export default function utf8BufferSize(str) {
  /** @type {number} */
  let bytes = 0;
  for (let i = 0, len = str.length; i < len; i++) {
    /** @type {number} */
    let codePoint = str.codePointAt(i);
    if (codePoint < 128) {
      bytes++;
    } else {
      if (codePoint <= 2047) {
        bytes++;
      } else if(codePoint <= 65535) {
        bytes+=2;
      } else if(codePoint <= 1114111) {
        i++;
        bytes+=3;
      }
      bytes++;
    }
  }
  return bytes;
}