unwxvpkg/src/util.js

unpack wx[av]pkg

'use strict';

module.exports = {
  /**
   * 判断两个数组是否相等
   * @param  {Array}   a 数组a
   * @param  {Array}   b 数组b
   * @return {Boolean}   判断结果
   */
  equal(a, b) {
    if (a.length !== b.length) return false;

    for (let i = 0, len = a.length; i < len; i++) {
      if (a[i] !== b[i]) return false;
    }

    return true;
  },
  /**
   * 读取32位无符号整型数
   * @param  {Array}  buffer buffer数组
   * @param  {Number} offset 偏移量
   * @return {Number}        读取到的整型数
   */
  readInt32(buffer, offset) {
    offset = offset || 0;
    return (buffer[offset] << 24) + (buffer[offset + 1] << 16) + (buffer[offset + 2] << 8) + (buffer[offset + 3] << 0);
  },

  /**
   * 读取16位无符号整型数
   * @param  {Array}  buffer buffer数组
   * @param  {Number} offset 偏移量
   * @return {Number}        读取到的整型数
   */
  readInt16(buffer, offset) {
    offset = offset || 0;
    return (buffer[offset] << 8) + (buffer[offset + 1] << 0);
  },

  /**
   * 读取8位无符号整型数
   * @param  {Array}  buffer buffer数组
   * @param  {Number} offset 偏移量
   * @return {Number}        读取到的整型数
   */
  readInt8(buffer, offset) {
    offset = offset || 0;
    return buffer[offset] << 0;
  },

  /**
   * 将buffer数组转为字符串
   * @param  {Array}  buffer buffer数组
   * @return {String}        字符串
   */
  bufferToString(buffer) {
    let str = '';
    for (let i = 0, len = buffer.length; i < len; i++) {
      str += String.fromCharCode(buffer[i]);
    }
    return str;
  },

  /**
   * 将字符串转为buffer数组
   * @param  {String}   str 字符串
   * @return {Array}        buffer数组
   */
  stringToBuffer(str) {
    let buffer = Buffer.alloc(str.length, 0xff);
    str.forEach((char, index) => {
      buffer[index] = char.charCodeAt(0) & 0xff;
    });

    return buffer;
  },

  /**
   * 读取buffer数组的指定字节数
   * @param  {Array}  buffer buffer数组
   * @param  {Number} begin  开始游标
   * @param  {Number} length 读取长度
   * @return {Array}         读取到的数据
   */
  readBytes(buffer, begin, length) {
    let end = begin + length;
    if (end > buffer.length) {
      throw new Error('读取的长度超出了buffer数组的界限！');
    }

    return buffer.slice(begin, end);
  },
};