wiegand-encoder
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Encode and decode 26, 34, or 38 bit Wiegand protocol credentials
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# wiegand-encoder
Lightweight module that encodes and decodes 26, 34, or 38 bit Wiegand protocol credentials for communication with access control systems.
[](https://github.com/jessety/wiegand-encoder/actions?query=workflow%3Aci)
[](https://codecov.io/gh/jessety/wiegand-encoder)
[](https://www.npmjs.com/package/wiegand-encoder)
[](https://github.com/jessety/wiegand-encoder/blob/main/LICENSE)
## Installation
```bash
npm install wiegand-encoder
```
## Usage
```javascript
// Modules
import wiegand from 'wiegand-encoder';
// CommonJS
const wiegand = require('wiegand-encoder');
```
### Encoding
The `encode()` function converts a card number and facility code into binary, counts the bit parity of each half of the message, and wraps it in parity bits.
```javascript
const encoded = wiegand.encode(cardNumber, facilityCode);
wiegand.encode(wiegand.encode(324, 90));
// 00101101000000001010001000
```
If the specified card number or facility code are too high for the standard bit length, it will throw an exception. The largest possible card number in 26-bit protocol is `65535`, and the largest possible facility code is `255`.
### Decoding
The `decode()` function validates the parity bits on either side of the message, then parses the message content from binary back into integers.
```javascript
const { cardNumber, facilityCode } = wiegand.decode('00101101000000001010001000');
// { cardNumber: 324, facilityCode: 90 }
```
If the parity bits are invalid, `decode()` will throw an exception.
To check parity on a message without decoding it, use `parity.validate()`.
```javascript
try {
wiegand.parity.validate('00101101000000001010001000');
} catch (error) {
console.error(error);
}
```
### Alternate bit length
By default, `encode()` encodes all messages as 26-bit.
To encode a larger message (e.g. 34-bit, 38-bit, etc.) send the bit length for the card number and facility code to the `encode()` function.
26-bit credentials use a card number length of `16` and a facility code length of `8`. To encode a 34-bit message, use a card number length of `22` and a facility code length fo `10`.
```javascript
wiegand.encode(cardNumber, facilityCode, cardNumberLength, facilityCodeLength);
wiegand.encode(wiegand.encode(324, 90, 22, 10));
// 0000101101000000000000001010001000
```
The `decode()` function also supports optional `cardNumberLength` and `facilityCodeLength` parameters, but will attempt to infer them based on the content of the length of the message if omitted.
```javascript
const { cardNumber, facilityCode } = wiegand.decode('0000101101000000000000001010001000');
// { cardNumber: 324, facilityCode: 90 }
```
## License
MIT © Jesse Youngblood