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sudotman/orig.js

Created January 20, 2023 12:02
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original crc
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orig.js
/**
* [js-crc]{@link https://github.com/emn178/js-crc}
*
* @namespace crc
* @version 0.2.0
* @author Chen, Yi-Cyuan [emn178@gmail.com]
* @copyright Chen, Yi-Cyuan 2015-2017
* @license MIT
*/
/*jslint bitwise: true */
(function () {
'use strict';
var root = typeof window === 'object' ? window : {};
var NODE_JS = !root.JS_CRC_NO_NODE_JS && typeof process === 'object' && process.versions && process.versions.node;
if (NODE_JS) {
root = global;
}
var COMMON_JS = !root.JS_CRC_NO_COMMON_JS && typeof module === 'object' && module.exports;
var AMD = typeof define === 'function' && define.amd;
var ARRAY_BUFFER = !root.JS_CRC_NO_ARRAY_BUFFER && typeof ArrayBuffer !== 'undefined';
var HEX_CHARS = '0123456789abcdef'.split('');
var Modules = [
{
name: 'crc32',
polynom: 0xEDB88320,
initValue: -1,
bytes: 4
},
{
name: 'crc16',
polynom: 0xA001,
initValue: 0,
bytes: 2
}
];
var i, j, k, b;
for (i = 0; i < Modules.length; ++i) {
var m = Modules[i];
m.method = (function (m) {
return function (message) {
return crc(message, m);
};
})(m);
m.table = [];
for (j = 0; j < 256; ++j) {
b = j;
for (k = 0; k < 8; ++k) {
b = b & 1 ? m.polynom ^ (b >>> 1) : b >>> 1;
}
m.table[j] = b >>> 0;
}
}
var crc = function (message, module) {
var notString = typeof message !== 'string';
if (notString && ARRAY_BUFFER && message instanceof ArrayBuffer) {
message = new Uint8Array(message);
}
var crc = module.initValue, code, i, length = message.length, table = module.table;
if (notString) {
for (i = 0; i < length; ++i) {
crc = table[(crc ^ message[i]) & 0xFF] ^ (crc >>> 8);
}
} else {
for (i = 0; i < length; ++i) {
code = message.charCodeAt(i);
if (code < 0x80) {
crc = table[(crc ^ code) & 0xFF] ^ (crc >>> 8);
} else if (code < 0x800) {
crc = table[(crc ^ (0xc0 | (code >> 6))) & 0xFF] ^ (crc >>> 8);
crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
} else if (code < 0xd800 || code >= 0xe000) {
crc = table[(crc ^ (0xe0 | (code >> 12))) & 0xFF] ^ (crc >>> 8);
crc = table[(crc ^ (0x80 | ((code >> 6) & 0x3f))) & 0xFF] ^ (crc >>> 8);
crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
} else {
code = 0x10000 + (((code & 0x3ff) << 10) | (message.charCodeAt(++i) & 0x3ff));
crc = table[(crc ^ (0xf0 | (code >> 18))) & 0xFF] ^ (crc >>> 8);
crc = table[(crc ^ (0x80 | ((code >> 12) & 0x3f))) & 0xFF] ^ (crc >>> 8);
crc = table[(crc ^ (0x80 | ((code >> 6) & 0x3f))) & 0xFF] ^ (crc >>> 8);
crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
}
}
}
crc ^= module.initValue;
var hex = '';
if (module.bytes > 2) {
hex += HEX_CHARS[(crc >> 28) & 0x0F] + HEX_CHARS[(crc >> 24) & 0x0F] +
HEX_CHARS[(crc >> 20) & 0x0F] + HEX_CHARS[(crc >> 16) & 0x0F];
}
hex += HEX_CHARS[(crc >> 12) & 0x0F] + HEX_CHARS[(crc >> 8) & 0x0F] +
HEX_CHARS[(crc >> 4) & 0x0F] + HEX_CHARS[crc & 0x0F];
return hex;
};
var exports = {};
for (i = 0;i < Modules.length;++i) {
var m = Modules[i];
exports[m.name] = m.method;
}
if (COMMON_JS) {
module.exports = exports;
} else {
for (i = 0;i < Modules.length;++i) {
var m = Modules[i];
root[m.name] = m.method;
}
if (AMD) {
define(function() {
return exports;
});
}
}
})();
@mehuylsharma
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mehuylsharma commented Jan 20, 2023 

/**
 * [js-crc]{@link https://github.com/emn178/js-crc}
 *
 * @namespace crc
 * @version 0.2.0
 * @author Chen, Yi-Cyuan [emn178@gmail.com]
 * @copyright Chen, Yi-Cyuan 2015-2017
 * @license MIT
 */
/*jslint bitwise: true */
(function () {
  'use strict';

  var root = typeof window === 'object' ? window : {}; // Verifies that window is true and sets root variable to window or an empty object if it doesn't exist
  var NODE_JS = !root.JS_CRC_NO_NODE_JS && typeof process === 'object' && process.versions && process.versions.node; // Verifies that we are using nodejs
  if (NODE_JS) {
    root = global; // If in nodejs, root is global (an object that encompasses window and some more file system functionality)
  }
  var COMMON_JS = !root.JS_CRC_NO_COMMON_JS && typeof module === 'object' && module.exports; // If we're a commonjs module
  var AMD = typeof define === 'function' && define.amd; // Not sure what define.amd is but if define is a function AMD is define.amd
  var ARRAY_BUFFER = !root.JS_CRC_NO_ARRAY_BUFFER && typeof ArrayBuffer !== 'undefined';
  var HEX_CHARS = '0123456789abcdef'.split(''); //Create an array of each element in the string

  var Modules = [
    {
      name: 'crc32',
      polynom: 0xEDB88320,
      initValue: -1,
      bytes: 4
    }, 
    {
      name: 'crc16',
      polynom: 0xA001,
      initValue: 0,
      bytes: 2
    }
  ]; // Two objects in array with above properties 

  var i, j, k, b; // Instantiate 4 variables, the types are unknown as of now
  for (i = 0; i < Modules.length; ++i) {
    var m = Modules[i];
    m.method = (function (m) {
      return function (message) {
        return crc(message, m);
      };
    })(m);
    m.table = [];
    for (j = 0; j < 256; ++j) {
      b = j;
      for (k = 0; k < 8; ++k) {
        b = b & 1 ? m.polynom ^ (b >>> 1) : b >>> 1;
      }
      m.table[j] = b >>> 0;
    }
  }
  
  
  //For loop that does stuff, there are bitwise operators that I'm not aware of but should be convertable pretty easily minus the specific js syntax

  var crc = function (message, module) {
	// crc is a function that takes in two params, message and module
    var notString = typeof message !== 'string'; // if message is not a string then notString is true
    if (notString && ARRAY_BUFFER && message instanceof ArrayBuffer) { // if message is an instance of (message's prototype is) ArrayBuffer and Array_buffer exists and notString is true
      message = new Uint8Array(message);
    }

	// i dont understand below but instantiations
	
    var crc = module.initValue, code, i, length = message.length, table = module.table;
	
	//below code has tons of bitwise stuff that i have no idea about, so skippin
    if (notString) {
      for (i = 0; i < length; ++i) {
        crc = table[(crc ^ message[i]) & 0xFF] ^ (crc >>> 8);
      }
    } else {
      for (i = 0; i < length; ++i) {
        code = message.charCodeAt(i);
        if (code < 0x80) {
          crc = table[(crc ^ code) & 0xFF] ^ (crc >>> 8);
        } else if (code < 0x800) {
          crc = table[(crc ^ (0xc0 | (code >> 6))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
        } else if (code < 0xd800 || code >= 0xe000) {
          crc = table[(crc ^ (0xe0 | (code >> 12))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | ((code >> 6) & 0x3f))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
        } else {
          code = 0x10000 + (((code & 0x3ff) << 10) | (message.charCodeAt(++i) & 0x3ff));
          crc = table[(crc ^ (0xf0 | (code >> 18))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | ((code >> 12) & 0x3f))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | ((code >> 6) & 0x3f))) & 0xFF] ^ (crc >>> 8);
          crc = table[(crc ^ (0x80 | (code & 0x3f))) & 0xFF] ^ (crc >>> 8);
        }
      }
    }
    crc ^= module.initValue;

    var hex = '';
    if (module.bytes > 2) {
      hex += HEX_CHARS[(crc >> 28) & 0x0F] + HEX_CHARS[(crc >> 24) & 0x0F] +
             HEX_CHARS[(crc >> 20) & 0x0F] + HEX_CHARS[(crc >> 16) & 0x0F];
    }
    hex += HEX_CHARS[(crc >> 12) & 0x0F] + HEX_CHARS[(crc >> 8) & 0x0F] +
           HEX_CHARS[(crc >> 4) & 0x0F] + HEX_CHARS[crc & 0x0F];
    return hex;
  };
  
  //Below stuff is just making sure exports work accoring to if we're in CommonJS, AMD (?) and assigning them nicely

  var exports = {};
  for (i = 0;i < Modules.length;++i) {
    var m = Modules[i];
    exports[m.name] = m.method;
  }
  if (COMMON_JS) {
    module.exports = exports;
  } else {
    for (i = 0;i < Modules.length;++i) {
      var m = Modules[i];
      root[m.name] = m.method;
    }
    if (AMD) {
      define(function() {
        return exports;
      });
    }
  }
})(); // <- this part here makes sure the function is run once the file is run

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